Micro‐Silicon as Anodes for High‐Cycle‐Life Lithium‐Ion Batteries

Abstract

Silicon (Si) is regarded as a promising anode material for next‐generation lithium‐ion batteries (LIBs) due to its exceptionally high theoretical specific capacity. However, the large volumetric change that occurs during lithiation and delithiation has hindered the practical implementation of Si anodes, even though nano‐Si (n‐Si) shows improved cycling capability. This review examines the emerging strategies of increasing battery performance using feasible micro‐Si (μ‐Si) as anode. Trade‐offs between performance, cost, and scalability of n‐Si and µ‐Si are compared. Porous Si architecture is explored to accommodate volume expansion while preserving electrical integrity. Electrolyte design, including high‐concentration electrolytes and functional additives, is reviewed in the context of promoting stable solid electrolyte interphase (SEI) formation on μ‐Si surfaces. Coating strategies such as carbon, polymer, and metal oxide coatings as well as compositing μ‐Si with conductive matrices are discussed for their roles in buffering mechanical strain and enhancing electrochemical performance. Finally, the economic and practical implications of using metallurgical‐grade µ‐Si and scalable processing techniques are analyzed, providing insight into the viability of μ‐Si‐based anodes for commercial applications. This review aims to guide future research toward the development of high‐energy density, long‐life LIBs using earth‐abundant and industrially relevant µ‐Si materials.

Microsized Si (μ‐Si) anodes are promising for high‐energy LIBs due to their high capacity and low cost, but suffering from issues such as large volume expansion, unstable interfaces, and cycling instability. This review discussed the up‐to‐date strategies including μ‐Si anode architectures as well as electrolyte and binder engineering to mitigate these issues while evaluating the scalability and commercial viability of μ‐Si anodes.

1. Introduction

As energy demands rise across the globe, more options for energy storage become appealing to use [1]. Research over the past two decades on lithium‐ion batteries (LIBs) has aimed to achieve this goal and to progress energy storage technologies further [2]. LIBs have been a research focus due to their high volumetric [3] and gravimetric energy density [4] and their versatility in electric vehicles (EVs) and energy grid storage [5]. However, difficulties arise in fully integrating LIBs into the power grid and EVs due to application costs, sources of materials, and the aging of the battery [6, 7]. To overcome these limitations, researchers over the past decade have focused on the materials used in each component of the battery [8]. High energy density cathode materials such as transition metal oxides [9], modified NCMs and NCAs [10], sulfur [11], and covalent organic frameworks (COFs) [12], as well as different types of solid‐state electrolytes have been studied [13]. For anode materials, however, graphite is primarily used due to its desirable chemical and mechanical properties, and compatibility with current electrolyte technology [14]. But graphite has been limited by its theoretical specific capacity of 372 mAh g⁻¹ [15] which has led to an increase in research into higher‐capacity anode materials over the past decade [16]. Anode materials in LIBs need to provide a high capacity, increased calendar life [17], be environmentally friendly [18], have cycling performance, and be commercially stable [19]. Issues arise with high energy density batteries for commercial use involving maintaining chemical stability, high electrical conductivity, and formation of uniform solid electrolyte interphase (SEI) while minimizing dendrite growth [20]. Current examples of some commonly researched and industrially viable anodes include lithium metal [21], micro‐sized graphite [22], and silicon (Si)‐based anode materials [23].

Si as an anode material has been a desirable choice for replacing graphite anodes due to its highly desirable theoretical capacity of ~4200 mAh g⁻¹ [24, 25]. Si presents not only desirable electrochemical properties for high energy density LIBs, but also potential economic benefits due to its ease of manufacturing from resources such as Si waste [26]. Challenges arise in using Si as an anode material compared to graphite in areas such as long‐term mechanical stability [27], lower electrical conductivities [28], and poor diffusion rate [29]. Other issues arise during cycling, which include its high volume expansion during lithiation (~300%) [30], which in turn leads to the Si particles pulverizing themselves during cycling, continuous SEI growth on its surface, and low initial coulombic efficiency (ICE), which consumes Li [31, 32]. These challenges, overall, have hindered commercialization of Si‐based anodes for large‐scale applications such as EVs [33], and grid energy storage. With the high theoretical capacity of Si, it still presents high potential to satisfy the future EVs demand growth [34].

Current research has focused on the production of nano‐Si (n‐Si) to overcome the challenges presented by traditional Si‐based anodes [35]. While n‐Si has been the predominant area of research for Si‐based anodes [36], their limitations in industrial applications and economics have led to an increasing trend toward micro‐sized silicon (μ‐Si)‐based anodes to integrate toward replacing graphite as the main anode material [37, 38]. For practical industry applications, n‐Si has challenges such as low ICE [39], higher cost [40], low tap density [41], and complex fabrication methods [42, 43]. Gradually, interest in µ‐Si has been increasing due to the unexplored benefits of implementing µ‐Si particles for anode materials for industrial and commercial applications. It has been explored for industry applications due to some major differences between n‐Si and μ‐Si, such as its much lower costs to produce, and lower surface reactivity compared to n‐Si, which would lead to better calendar life and SEI stability [44, 45]. Some companies have adopted graphite‐silicon oxide (Gr‐SiO _x ) blended anodes to balance high capacity with improved cycle life by mitigating the volumetric expansion of Si [46]. Current technologies in the industry for Si‐graphite anodes approximate around 10%–15% Si [47] on the high end of weight percent Si. While 7 wt% Si in anodes is required to compete with fossil fuel vehicles using high‐energy‐density cathodes, commercial anodes are currently limited to 2–3 wt% Si to ensure adequate cycle life [48, 49]. Si ratios remain around 15%–25% for a majority of current research but high ratio Si anode research has been able to reach up to 60% Si ratios for Si‐graphite based anode systems [50, 51]. However, fully implementing these high‐Si ratio graphite anodes has proven to be difficult due to these challenges primarily with n‐Si particles, which reduces the energy density of Si‐graphite anodes and provides poorer cycling stability [52, 53]. Research over the past 5 years has begun to develop µ‐Si‐based anodes to gain more popularity due to new technologies on the modification of Si particles to be used in Si‐graphite composite anodes [54]. As previously stated, graphite is the dominating material of choice for anode materials in LIBs. While Si presents significant challenges for full implementation in commercial anodes, high‐ratio Si‐graphite composite anodes have emerged as a promising research direction for μ‐Si‐based anode development in LIBs [55, 56]. Figure 1 briefly shows some of the characteristics, fabrication methods, and applications of µ‐Si anode materials.

FIGURE 1.

Overview of μ‐Si‐based anodes and their key characteristics in linking research results to industry adoption.

This review will discuss recent developments and breakthroughs in µ‐Si anode modifications that can be developed into high‐ratio Si‐graphite anode materials. Strategies that will be discussed will involve stabilizing the structure of µ‐Si particles, doping and coating of Si particles, and non‐Si modification of graphite, binders, and electrolytes. Specifically, this article will focus on commercially viable applications of µ‐Si modifications and present the current research technologies and the potential economic benefits and shortcomings involving n‐Si and µ‐Si to present why µ‐Si is a viable technology for Si‐based anode materials for LIBs. We will present tradeoffs involving doping Si with impurity materials and balancing the higher conductivity and the amount of impurity. We will also compare the current technologies and discuss the effects of the added Si amount on the overall performance of batteries. We will use these presented ideas to show why µ‐Si should be more focused in research areas of Si anodes. Commercial applications and the scalability of LIB materials will be an important measure to overcome [57]. Figure 2 shows the timeline for Si‐based anodes and the major accomplishments that have been achieved over the past 50 years. This paper will review the characteristics and strategies of µ‐Si and why it is the best option to achieve this goal compared to the traditionally researched n‐Si. We will discuss the differences between µ‐Si and n‐Si and where each excels and falls short in specific areas, especially in commercial applications where µ‐Si excels.

FIGURE 2.

Timeline of advancements in μ‐Si anodes and their integration into laboratory and industrial applications [58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68]. Adapted with permission [62]. Copyright 2008, John Wiley and Sons. Adapted with permission [63]. Copyright 2013, American Chemical Society. Adapted with permission [64]. Copyright 2017, The American Association for the Advancement of Science. Adapted with permission [65]. Copyright 2019, Springer Nature with a Creative Commons CC‐BY 4.0 license. Adapted with permission [66]. Copyright 2023, IOP Publishing Limited with a Creative Commons CC‐BY 4.0 license. Adapted with permission [67]. Copyright 2021, The American Association for the Advancement of Science.

2. Comparison of n‐Si and μ‐Si‐Based Anodes

With the current split in Si‐based anode research, a comparison of µ‐Si and n‐Si is important for understanding the potential applications and implementation of Si‐based anodes. It is important to understand the differences in electrochemistry and processing techniques between n‐Si and μ‐Si. Studies on each type of Si depend on the associated challenges that should be mitigated with Si‐based anodes, such as volume expansion, reactivity, and economic viability. Figure 3 compares the advantages and limitations of n‐Si and µ‐Si. Comparing their properties, we will discuss why µ‐Si research could lead to a future in commercially viable LIB anode materials.

FIGURE 3.

Comparison of the advantages and disadvantages of n‐Si and μ‐Si.

2.1. n‐Si‐Based Anodes

Nano‐scale Si has been studied to control the volume expansion mechanically and improve the electrical conductivity and diffusion rates [69]. While in laboratory‐scale research n‐Si has been appealing due to its potential in overcoming problems that Si‐based anodes face, these advancements have yet to be used in commercial‐scale LIBs. In commercial applications, n‐Si faces challenges such as complex manufacturing and high cost [70], high surface area leading to more side reactions with electrolyte which further reduces stability [71], poor electrochemical properties such as ICE and tap density [72] and poor calendar aging [73]. These challenges hinder n‐Si materials to become a prominent solution to implement higher ratio Si anodes into the battery industry [74].

Some synthesis methods for n‐Si included a sputtering method of physical vapor deposition [75], advanced mechanical ball milling techniques [76], and chemical vapor deposition [77]. While some of the methods of research have been specified for larger‐scale applications and research, there is still a large technological barrier for n‐Si to be a viable option in industrial batteries. However, n‐Si has been deserving of its in‐depth research with some of its benefits anticipated to be captured on a larger scale by implementing strategies such as carbon coating [78], new binders [79], and electrolytes [80]. These strategies will also be discussed as possible solutions to µ‐Si challenges.

2.2. µ‐Si‐Based Anodes

Recent research has increasingly focused on µ‐Si‐based anodes, exploring the distinctive properties of µ‐Si in comparison to n‐Si‐based anodes. For industrial applications, µ‐Si is advantageous because of its higher tap density, which allows more efficient electrode packing and has become a major focus in the development of µ‐Si‐based anodes for LIBs [81]. µ‐Si also presents advantageous conditions for its simplicity in manufacturing and fabrication. As stated in the previous section, n‐Si requires advanced manufacturing techniques that would involve high costs for industry adaptation. On the other hand, µ‐Si is inherently abundant, which drives down its price, and requires less advanced fabrication to be usable for anode purposes [82]. Although μ‐Si offers higher tap density, lower surface area, higher ICE, and lower production cost than n‐Si, several challenges limit its commercialization. Its large volume change during cycling causes particle cracking, unstable SEI formation, electrode swelling, and loss of electrical contact. These issues become more severe in thick electrodes with commercial‐level mass loading because Li⁺ ion transport, electron conduction, and active material utilization are limited. Moreover, irreversible Li consumption during initial SEI formation remains important in full cells with a limited Li inventory, making prelithiation necessary to improve ICE and preserve Li from the cathode. However, prelithiation must be carefully controlled because insufficient or nonuniform lithiation provides limited improvement, whereas excessive lithiation reduces reversible capacity [83]. Electrochemical prelithiation is difficult to scale up because it requires a temporary cell. Li metal‐based methods also require strict environmental control and can be time consuming. Furthermore, many effective μ‐Si structures require complex processing, which increases production costs and reduces manufacturing reproducibility [84].

The failure mechanism of μ‐Si is not fundamentally different from that of n‐Si because both result from the large alloying‐induced volume expansion of Si, mechanical stress, unstable SEI formation, and loss of electrical contact [83]. The main difference is the severity of each degradation process. μ‐Si particles are more susceptible to cracking and pulverization because they exceed the critical fracture size [85]. In contrast, n‐Si particles better withstand mechanical strain but cause greater SEI formation and irreversible lithium loss because of their higher surface area. Thus, μ‐Si degradation is mainly caused by particle cracking and electrode‐structure damage, whereas n‐Si degradation is more strongly influenced by surface reactions and interfacial instability. During repeated lithiation and delithiation, the large volume expansion of μ‐Si causes particle fracture and gradual rearrangement, filling the interparticle voids and resulting in electrode solidification, reduced porosity, and increased tortuosity. As a result, electrolyte penetration and Li⁺ transport become difficult, while mechanical stress causes further particle pulverization and loss of electrical contact [72]. In addition, the collapse of the porous electrode structure repeatedly breaks and reforms the SEI, causing continuous Li consumption and faster capacity loss during long‐term cycling [86, 87]. These issues are more critical in high‐loading μ‐Si electrodes because electrode solidification reduces stress relaxation and increases transport resistance. Therefore, maintaining a stable porous electrode structure using carbon frameworks, elastic binders, optimized electrode designs, and stable electrolytes or interphases is important for achieving high areal capacity and long cycle life. Compared with SiO _x ‐based composites, μ‐Si also experiences more severe mechanical degradation. Si/C composites help reduce these issues by using conductive carbon networks and internal void spaces. However, degradation can still occur because of Si–C interfacial separation, unstable SEI formation, and failure of the conductive network [88, 89]. SiO _x ‐graphite composites show less volume expansion than pure μ‐Si, but they have low ICE because Li is irreversibly consumed to form Li₂O, lithium silicates, and the SEI [32, 90]. Therefore, μ‐Si research should focus on controlling particle fracture, developing strong binders, maintaining electrode porosity and conductive networks, and forming stable interphases at practical mass loadings. In comparison, Si/C and SiO _x ‐graphite systems require more attention to internal interface stability, irreversible Li loss, and composite optimization.

Since graphite is already the most common anode material used commercially, combining it with Si will allow for smoother implementation of Si into commercial batteries. Graphite pairs well with µ‐Si since having a large portion of the anode composed of graphite helps reduce the impact of the volume expansion, increases the low conductivity of Si, and still maintains high electrochemical properties such as specific and volumetric capacities [91]. Some studies have focused mostly on the n‐Si advancements for Si‐based anode materials [25, 92] while this review will discuss strategies for implementing µ‐Si into a larger commercial role for LIBs and specifically focus on how to achieve high Si ratios for Si‐graphite‐based anodes. This will be achieved by exploring recent research technologies and strategies that have helped minimize the challenges arising from using µ‐Si‐based batteries. Si modifications, graphite modifications, effective binder design, novel electrolyte design, and low‐cost fabrication methods will organize these strategies.

3. Microstructural Engineering of μ‐Si‐Based Anodes

Si as an anode has already been extensively studied and different strategies have been suggested to overcome its challenges [93]. While a large amount of the improvements involves modifying Si, other components within the battery, such as binders and electrolyte designs, as well as the modification of graphite with Si materials have also been studied. In this section, we will discuss the stabilization of Si particles for high‐ratio Si‐based anodes through different strategies including doping and coating of Si microparticles (SMPs), as well as structural modifications of SMPs such as core–shell and composite structures. Table 1 gives a few examples of modified µ‐Si structures with various reported electrochemical performance results for different variations of µ‐Si anodes.

TABLE 1.

Modified µ‐Si structures with electrochemical performance comparisons.

Si Structure	Specific capacity, mAh g −1	Cycles	Current density/C‐rate	ICE, %	Mass loading, mg cm −2	Pouch cell energy density, Wh kg −1 /Cycles/C‐rate	Ref.
VC‐SC	—	—	—	—	—	490.3/500/—	[94]
µHGC + nHGC@Si	651.4	500	2.0 A g−1	85.9	—	—	[95]
d‐SiO@SiO x /C@C	1023	300	1.0 A g−1	—	—	569/400/0.5 C	[96]
Si@HC	1053	200	0.1 A g−1	70.0	2.6	—	[97]
DP‐Si‐1.0	935.9	100	0.5 A g−1	64.5	0.65–0.85	—	[98]
Si@rGO(S)	2586	150	0.1 C	93.0	1.0–1.1	—	[99]
Si/C/CNT/Cu	~700	2300	2.0 A g−1	72.6–74.8	1.1	—/100/1.0 C	[100]
Si@C@LPS 15%	~1600	300	2.0 A g−1	86.7	0.6–1.2	—/100/0.5 C	[101]

3.1. µ‐Si Structural Modifications

One promising structure that will be analyzed involves modification of the structure and network of µ‐Si particles into a monolithic layered structure with a crystalline–amorphous network to address the issues of volume expansion and structural degradation with µ‐Si‐based anodes [102]. Researchers transformed montmorillonite into monolithic layered Si with a thickness of 10–20 µm, which is composed of crystalline and amorphous regions that are designed to mitigate stresses from volume changes during cycling. This allows the material to enhance its structural integrity and longevity. Figure 4a shows how the monolithic structure was synthesized. Tap density for the montmorillonite derived Si (M‐Si) is comparable to graphite at ~0.9–1.0 g cm⁻¹. Due to the mesoporous architecture and residual SiO₂ network present in the monolithic structure, both can act as support to the volume expansion of the SMPs, allowing the cell to have enhanced cycling stability over high cycle amounts. For the half‐cell, a reversible capacity of 1130 mAh g⁻¹ with a capacity retention of 92% over 500 cycles was recorded for M‐Si‐4 (mass ratio of M‐Si/SiO₂), and pouch cell testing with NCM811 exhibits an energy density of 655 Wh kg⁻¹ with 82% capacity retention after 200 cycles. These electrochemical tests show promise for a scalable process for the modified structure of µ‐Si for commercial batteries. Continuing to modify the structure with compatible doping and coating of the layered structure could improve the conductivity of the Si or help stabilize the SEI layer formation to allow for potentially superior cycling ability.

FIGURE 4.

(a) Schematic illustration of the Montmorillonite‐derived Si (M‐Si), and long‐term cycling stabilities of M‐Si‐4 anode at different C‐rates. Adapted with permission [102]. Copyright 2024, American Chemical Society. (b) A schematic diagram of the synthesis process of FPSi@C. EIS curves before cycle and long‐term cycling performances at 3.6 A g⁻¹ of PSi@C and FPSi@C. Adapted with permission [103]. Copyright 2008, John Wiley and Sons.

A gradient hybrid SEI (H‐SEI) is developed to maintain structural integrity of μ‐Si anodes [104]. It contains crack‐arresting nanocrystals and a flexible polymer‐rich outer layer that suppress interfacial cracking, redistribute mechanical stress, and maintain Li⁺ transport in μ‐SiO _x anodes. The resulting 1 Ah pouch cells retained 81.8% capacity after 1000 cycles at 30 °C, 80.3% after 500 cycles at 70 °C, and 78.7% at −20 °C, demonstrating strong cycling stability over a wide temperature range.

Other modifications have been researched over the past half decade to optimize currently known structural designs or discover new and unique structural designs for Si. Phase‐engineering and crystallographic modifications of microsized SiO _x ‐based anodes present a novel way to produce a scalable, modifiable method to improve the mechanical integrity of SiO _x anodes [105]. These recent discoveries create new paths toward modification of the structure of µ‐Si particles to be more desirable for commercialization. Zeng et al. found a scalable and environmentally friendly structuring of µ‐Si into a planar structure made up of fragmented porous Si (FPSi) made from etching an Al–Si alloy, ball milling, and carbon coating [103]. Ball‐milling transforms the 3D porous Si (PSi) into 2D planar structures, which helps reduce internal stresses, increase areal and specific capacity, and enhance the long‐term cycling over 3D PSi. PSi and FPSi were both coated with carbon to then be tested with FPSi@C, which shows a specific capacity of 810 mAh g⁻¹ after 600 cycles with a capacity retention of ~83.5% for the long‐term cycling performance at a current density of 3.6 A g⁻¹ as shown in Figure 4b. FPSi@C showed a superior areal capacity and lower impedance compared to PSi@C, which further indicates better performance of the modified structure of planar Si. Full‐cell testing and in situ characterization could give a better understanding of what is happening with the structure over hundreds of cycles and how to best optimize the planar Si, either by modifying the carbon coating or understanding the SEI growth and better additives/coatings to control it to further increase the cycling of the sample. Overall, a novel structure of µ‐Si can be used to continuously improve the long‐term cycling of anodes and gives a foundation to expand toward commercialization, whether by using it with graphite for high Si ratio anodes or optimizing a fabrication process.

3.2. Porous µ‐Si Designs

Porous µ‐Si particles can combine the advantages of both µ‐ and n‐scale engineering for Si‐based anodes. PSi design with nanoporosity added to the structure can address the advantages and disadvantages of each strategy, while allowing a base µ‐Si particle to be used [106]. This design strategy has created the path toward stabilizing µ‐Si‐based anodes by incorporating a porous design into the µ‐Si particles [45]. As shown by Zheng et al., unique structures can be achieved by incorporating porous µ‐Si into anode materials, which creates a Formicarium‐like Si (FMSi) structure with nanoencapsulation to allow for scalable, long‐life batteries [107]. As represented in Figure 5a, the design that was created starts with montmorillonite minerals to be etched to form the formicarium structure out of porous µ‐Si. This is then coated with TiO₂ and combined with few‐layered MXene via electrostatic self‐assembly to encapsulate the coated porous µ‐Si. This unique structure of porous µ‐Si provides a hard–soft structure around Si, which was shown to improve the conductivity of Si, regulate its volume expansion complications, and allow the growth of a stable SEI layer. The electrochemical results of the novel structure were compared to bare FMPSi and FMPSi@TiO₂ without the layered MXene in Figure 5a. FMPSi@TiO₂@FMXene showed capacities of 1254.9 and 970.4 mAh g⁻¹ at current densities of 0.5 and 1 A g⁻¹ after 500 cycles. Its full‐cell performance with commercial LiFePO₄ (LFP) in 100 cycles showed a high‐capacity retention rate of 91.6%. This is a solid improvement over other µ‐Si‐based methods that have been reported by other recent researchers. FMPSi@TiO₂ shows that a nanoencapsulation structure of FMPSi‐based anodes can provide long‐cycling stability, and other methods to provide the hard–soft encapsulation around the Si particles can be an option toward stable µ‐Si‐based anodes.

FIGURE 5.

(a) Synthesis process of FMPSi@TiO2@FMXene with cycling performance at 0.5 A g⁻¹ for 500 cycles. Adapted with permission [107]. Copyright 2024, American Chemical Society. (b) Schematic illustration of Si/Si‐Ti anode synthesis, and half‐cell performance of Si1/4TiAl0.36 at 200 mA g⁻¹. Adapted with permission [108]. Copyright 2023, American Chemical Society. (c) Schematic diagram of porous structure and robust SEI film on different Si anodes along with electrochemical performance of cSiPC‐LHCE anode at 1 C. Adapted with permission [109]. Copyright 2024, John Wiley and Sons.

The structure of the Si skeleton improves other properties such as ICE and mechanical stability and electrical properties [110]. This stability‐to‐capacity ratio was experimented with Si/Ti–Si alloy to control the ratio of Si and Ti, therefore controlling its surface area and properties [108]. Ti was supplied by titanium‐blast furnace slag to reduce the environmental impact of eliminating the leftover slag. The titanium slag was combined with industrial Si and Al particles in an induction furnace at specific ratios. The cooled compound was then ball milled, and Al was etched off, leading to a controllable porous µ‐Si and Ti alloy (Figure 5b). The porous µ‐Si alloy provides a unique benefit by incorporating waste products and industrial powders to provide positive environmental and practical implications for manufacturing µ‐Si‐based anodes. Its electrochemical tests exhibited specific capacities of 1161 and 1112 mAh g⁻¹ at 0.2 and 0.5 A g⁻¹ after 200 and 100 cycles, respectively. The porous µ‐Si‐Ti alloy also showed an ICE of 81.2%, which is improved from bare porous µ‐Si. This process is simple and provides more possibilities for the scalability of porous µ‐Si‐based anodes while providing a positive outcome on the environmental impacts of the manufacturing process as well.

Other methods of improving porous µ‐Si structures focus on stabilizing the SEI layer by combining the porous µ‐Si with other structures to improve long‐term stability [111]. For example, incorporating 3D porous µ‐Si coated with pitch‐based carbon layer anode material with a localized high concentration electrolyte (LHCE) will provide a LiF‐rich SEI layer that leads to a stable SEI layer, which allows porous µ‐Si to be used for fast‐charging batteries [109]. The 3D porous µ‐Si was assembled via Si nanosheets to combine various advantages of each type of Si such as µ‐Si's improved tap density, processing and manufacturing efficiency, and electrochemical activity and stress tolerance of n‐Si. The pitch carbon‐coated crystalline Si (cSiPC) with the LHCE was compared with samples with regular electrolyte and μ‐SiPC which was synthesized by pitch‐coated pyrolysis of μ‐Si particles. Figure 5c shows the improved electrochemical performance of cSiPC‐LHCE, exhibiting a higher specific capacity over 200 cycles compared to cSiPC and μ‐SiPC with the regular electrolyte. The Si nanosheets within the Si particle were shown to improve the capacity retention of the anode at C‐Rates from 0.1 to 3 with the largest improvements appearing at higher C rates with the coated porous µ‐Si with the LHCE (cSiPC‐LHCE) having capacity retention rates of 84.2%, 70.8%, 49.1%, and 35.1 % for C rates of 0.5, 1, 2, and 3 C. Also, ICE of cSiPC‐LHCE was measured to be 90.07% with a reversible specific capacity of 2409 mAh g⁻¹. The cell was created as a thin film which reaches a 94.5% state of charge (SOC) in 10 min at 6 C. This study successfully incorporated LHCE to coated porous µ‐Si as an electrolyte formulation. A thin interfacial layer was developed from a functional molecule, (2S,2’S)‐N,N’‐carbonylbis(2‐amino‐2‐hydroxyacetamide) on porous μ‐Si to homogenize Li⁺ transport and form a dense, uniform LiF‐rich SEI. The modified anode delivered 2041 mAh g⁻¹ at 10 C, retained 64.2% of its capacity after 1000 cycles, and enabled non‐prelithiated full cells with 100% μ‐Si anodes to achieve 71% capacity retention after 100 cycles at 45 °C [112]. Similarly, Sun et al. combined porous μ‐Si with MXene, rGO, and a CVD‐carbon coating to form mPSi‐MGC, thereby improving mechanical stability, conductivity, and SEI stability. The optimized anode delivered 1800 mAh g⁻¹, retained 99 mAh g⁻¹ after 200 cycles, and maintained 818 mAh g⁻¹ at 3 A g⁻¹ [113].

In another study, μ‐Si is recovered from PV waste was converted into a sieve‐like PSi/C structure. This material exhibited low electrode expansion and long‐term cycling stability, while the corresponding pouch cell achieved a volumetric energy density of 1428 Wh L⁻¹. This approach also demonstrated a sustainable route for recycling PV Si waste [114]. Further strategies for improving porous µ‐Si should be explored by using recyclable materials and uniquely structuring the porous µ‐Si.

3.3. Composite‐Based µ‐Si Anodes

Composite µ‐Si anodes have emerged as a promising approach for improving battery performance. By integrating microscale Si particles with other materials such as carbon matrices, ceramic, or polymer composite designs can buffer volume changes, and achieve a balance between the high capacity of Si and the structural stability and conductivity of supporting materials [35, 115, 116]. In this section, recent developments in composite µ‐Si anodes are discussed, highlighting material selection strategies, fabrication techniques, and their electrochemical performances, and how these composites address the intrinsic limitations of µ‐Si while advancing the commercial viability of Si‐based anodes. A low‐cost and scalable solid‐state strategy was introduced to construct a multifunctional Li₂Si₂O₅/LiAlSiO₄/carbon network around μ‐Si particles. Li₂Si₂O₅ supplies additional Li, LiAlSiO₄ improves Li⁺ transport, and the carbon network enhances conductivity and buffers volume expansion. As a result, ICE increased from 77.9% to 93.3% and electrode expansion reduced from 262% to 140%. The graphite‐blended anode also retained 85.1% of its capacity after 300 cycles [117]. Inspired by structures of chloroplasts in biological systems, Xu et al. investigated a novel design for microsized SiO composites. They created a hierarchical SiO composite with a SiO core encircled by an outer carbon shell, dispersed SnO₂ nanoparticles, and a conductive N‐doped carbon interlayer [118]. Figure 6a shows a schematic of the process and structure of the composite anode. They measured its resversible capacity as 1209 mA h g⁻¹ after 160 cycles while still maintaining high rate capabilities at elevated current densities measuring of 722.7 mA h g⁻¹ at 5 A g⁻¹. Also, full‐cell measurements showed a 73% capacity retention and reversible capacity of 92.9 mAh g⁻¹ at 1 C after 100 cycles. These findings highlight the potential of biomimetic structural engineering as an effective strategy for enabling practical implementation of µ‐Si anodes in next‐generation LIBs, where maintaining structural integrity and conductive pathways during repeated lithiation cycles remains a critical challenge.

FIGURE 6.

(a) Synthesis process of the SiO‐NC@SnO2‐C composite. Half‐cell performances and rate capabilities of SiO‐NC@SnO2‐C, SiO@SnO2 and SiO anodes at 200 mA g⁻¹. Cycling performance of full‐cell assembled with LiFePO4 cathode and SiO‐NC@SnO2‐C anode at the current density of 1 C. Adapted with permission [118]. Copyright 2025, John Wiley and Sons. (b) Schematic illustration of the preparation of SiG/HC@CNTs composites and long‐term cycling capacities of the SiG/HC@CNTs, SiG/HC and SiG/WC anodes at 1.0 A g⁻¹. Adapted with permission [119]. Copyright 2025, Elsevier. (c) Fabrication process and TEM image MicroSi/SWCNT/Graphene@cPan composite, and cycling stability comparison of μ‐Si, Si/Cwith the SWCNT‐based composite anode at 1 A g⁻¹. Adapted with permission [120]. Copyright 2025, Elsevier.

In another study by Sun et al., porous µ‐Si particles were integrated with carbon nanotubes (CNTs) through a mixing‐calcination process, while a polyvinylpyrrolidone‐derived carbon layer formed a robust interfacial network [121]. This double‐layered architecture reduced the specific surface area while maintaining high tap density, features that are advantageous for the industrial implementation of µ‐Si anode materials. When combined with NCM811 for full‐cell testing, it showed high‐rate performance and more than 90% capacity retention over 100 cycles. Another aspect of their study was the extraction of porous µ‐Si particles from AlSi waste alloys, which offers an eco‐friendly supply of porous µ‐Si through material recycling. To enhance this process while maintaining the Si source, it is suggested to optimize the wet chemistry that creates the composite network. The composite network stabilizes the µ‐Si; however, due to the poor performance of half‐cells, refining the interface chemistry to improve the stability or conductivity of the SEI could be effective strategies for further process enhancement; for example, replacing CNTs with alternative carbon frameworks such as biomass‐derived porous carbons, or graphene‐based structures.

Si‐graphite composites represent a leading focus within µ‐Si anode due to the advantages in sustainability from life cycle assessments of Si compared to that of graphite [122]. However, µ‐Si‐graphite composite anodes still show some challenges such as volume expansion, electrode pulverization, and continuous SEI growth. Gao et al. proposed a method for synthesizing closed pore hard carbon from wood to encapsulate µ‐Si particles, creating a composite anode that accommodates volumetric expansion of Si through the closed pores, while the encapsulation enhances electrical contact and conductivity of the electrode [119]. Figure 6b shows the overall steps for synthesizing the composite. They showed that the internal holes of biomass‐derived closed pores have elastic, self‐healing characteristics that would well accommodate the volume expansion of µ‐Si. The wood‐derived µ‐Si‐graphite composite (SiG/HC@CNT) was synthesized with 25 wt% µ‐Si and was tested vs bare SIG/HC closed pore hard carbon and wood chips SiG/WC without CNTs and exhibited a 91.21% capacity retention after 500 cycles at 1 A g⁻¹. While testing the reversible capacity of 750 mAh g⁻¹ after 100 cycles at 0.2 A g⁻¹. Compared to other carbon sources, wood‐derived hard carbon offers a sustainable and cost‐effective alternative. Its inherent porous structure and the ability to form closed pores upon carbonization make it particularly suitable for Si encapsulation. This approach aligns with the broader trend in battery research focusing on sustainable materials and scalable fabrication methods. Introducing dopants into hard carbon could enhance the conductivity of Si, whereas mechanical modeling and characterization provide further insight into how porosity affects cell performance.

Recent research has increasingly focused on the integration of a protective shell around µ‐Si particles, along with additional processing steps, to fabricate a composite anode comprising µ‐Si and its surrounding shell [123]. Using an antisolvent spraying method with ethanol, Chiu et al. presented a cyclized polyacrylonitrile (cPAN) shell around µ‐Si particles, followed by a thermal treatment in the presence of single walled carbon nanotubes (SWCNTs) and graphene to create a µ‐Si/SWCNT/Graphene@cPAN composite anode material that can alleviate volume expansion of Si while providing a stable structure and facilitating electronic transport [120]. The SWCNTs and graphene were integrated into the cPAN matrix and form particles with diameters 20–30 µm. Figure 6c shows a schematic of how the structure is formed with a TEM image observing the morphological and structural design of the composite material. Also, the electrochemical performance demonstrated an ICE of 91.24% for the composite anode which was ~5%–10% more than bare µ‐Si and a basic Si/C composite. The cycling stability of the three materials was tested over 300 cycles with the composite material demonstrating a capacity of 902.84 mAh g⁻¹, which was improved over bare µSi and Si/C composite for higher cycle numbers. Unlike conventional Si anodes, which experience rapid capacity degradation resulting from substantial volume expansion and unstable SEI, the proposed composite showed considerable performance enhancements. The cPAN layer acted as a protective barrier, preventing direct contact between Si and the electrolyte, thereby stabilizing the SEI and enhancing ICE. To expand further upon this study, optimizing the antisolvent spraying process would answer questions on the potential scalability of the method and cost concerns that have not been fully explored. A study comparing different methods of antisolvent processes, such as antisolvent selection, droplet size control, and drying conditions would help fully optimize the spraying process for industrial use. Other industry testing such as environmental and thermal analysis of the cell and how it can be impacted by less‐than‐ideal conditions should be considered.

3.4. Carbon Coating of µ‐Si Anodes

Carbon coating has emerged as a highly effective approach to enhance the mechanical stability and electrochemical performance of µ‐Si anodes [124]. By forming a conductive, flexible, and often porous carbon layer on the Si surface, this modification can buffer volume changes, maintain electrode integrity, and improve electronic conductivity [125]. A recently noteworthy study used recycled µ‐Si from photovoltaic (PV) waste as a Si source and coated it with a locally ordered graphitized carbon layer [126]. This study presented a novel strategy that used locally ordered carbon compared to traditionally disordered graphitized carbon. This improved Li ion transport in the anode and enhanced the electrochemical performance of the battery. This ordered carbon structure also acted as a buffer between the electrolyte and Si. It helped to reduce degradation and improved the overall mechanical stability of the anode by accommodating volume changes in µ‐Si. Electrochemical tests done in the study supported these claims by showing a 95.13% capacity retention in full‐cell testing over 100 cycles. Additionally, the material demonstrated excellent electrochemical performance, with a reversible capacity of 2314 mAh g⁻¹ and retained a capacity of 1185 mAh g⁻¹ after 500 cycles at a current density of 2 A g⁻¹ (Figure 7a). These values can provide high energy density in combination with long‐term cyclability, which pure µ‐Si fails to exhibit. This study highlights a shift in mindset in future research for µ‐Si‐based anodes by providing efficient electrochemical performance from cheaper, abundant waste materials that are easily accessible. Other strategies to incorporate waste‐derived µ‐Si into anodes for LIBs will be crucial for scalability. Incorporating the graphitized carbon with Si could be a strategy to slowly incorporate the recycled µ‐Si into the anode system for commercial applications over time [129].

FIGURE 7.

(a) Illustration of the material structure, synthesis procedure, and performanceimproving mechanism of Si@t‐C, along with the cycling stability of Si@t‐C, Si@m‐C, Si@a‐C, and m‐Si anodes at a current density of 2 A g⁻¹. Adapted with permission [126]. Copyright 2025, American Chemical Society. (b) Schematic of the μSi@PAA and μSi@PAA‐TA‐CMC/CNT electrodes and mechanism before and after cycling with cycling performances at 4 A g⁻¹. Adapted with permission [127]. Copyright 2025, Elsevier. (c) Reprecipitation method and conditions to synthesize SMP/LSG composites, and comparison between different SMP composites specific discharge capacities. Adapted with permission [128]. Copyright 2024, American Chemical Society.

Different variations of carbon is possible for coating to the µ‐Si particles such as CNTs have shown to have a simple synthesis technique and potential as a scalable route to industrial production [130]. A study explored the construction of a dense CNT coating combined with carboxymethyl cellulose (CMC) to form a dense conductive coating around µ‐Si particles, with polymer binders polyacrylic acid (PAA) and tannic acid (TA) incorporated to ensure adhesion between the coating and particles [127]. The purpose of the coating structure was to buffer the volume changes of µ‐Si particles during cycling, improve the electronic conductivity and maintain the electrode's mechanical integrity. A schematic illustration of the dense coating layer on the µ‐Si particles and the interconnected network structure is presented (Figure 7b). Electrochemical tests showed that µ‐SiO _x @PAA‐TA‐CMC/CNT maintained a high reversable capacity of 891.6 mAh g⁻¹ at 4 A g⁻¹ after 1000 cycles, indicating good potential for industrial use for long‐term cycling of the battery. Full‐cell test was done with µSiO _x @PAA‐TA‐CMC/CNT||LFP at 0.5 C maintained a capacity of 129.6 mAh g⁻¹ after 100 cycles with a capacity retention of 89.6%. The testing results have shown long cycle life and high‐capacity LIBs performance for industrial use of the µ‐SiO _x @PAA‐TA‐CMC/CNT structure. Future work involves functionalization of the CNT to prevent agglomeration through repeated cycling, or finding alternatives to the CNTs which are more cost‐effective and scalable for industry fabrication. In situ characterization could provide deeper insight into how the polymer‐CNT coating network functions, enabling the development of improved and scalable alternatives to either the CNTs or the polymers used. Carbon layering wrapped around the µ‐Si particles has shown to be a viable method to accommodate volume expansion and provide a stable SEI layer protecting the µ‐Si [131, 132]. Recent research has presented a method to allow for a scalable method of wrapping graphene oxide (GO) around the µ‐Si particles forming SiO _x and SiC protective films to protect from volume expansion and enhancing electrical conductivity [128]. This reprecipitation method involved dispersing µ‐Si particles and GO in tetrahydrofuran (THF), then injecting into n‐hexane, where neither material was soluble, causing immediate aggregation and precipitation to form the composite film coating around the µ‐Si particle. The GO was laser scribed which allowed GO to convert to laser‐scribed graphene (LSG) which formed a 3D porous structure (RP‐SMP/LSG) enhancing the electrical conductivity. As shown in Figure 7c, the SMPs were wrapped with GO and the LSG network was formed around the protected SMPs by laser scribing. RP‐SMP/LSG showed improved discharge capacity compared to GO and with a capacity retention of 50.2% at 100 cycles. This process is novel for being simple, fast, and performed at room temperature, allowing for potential scalable applications. It was reported that the wrapping around the µ‐Si particles began to degrade, so adding dual coating or electrolyte additives to stabilize the wrapping during cycling could help to accommodate the volume expansion and stabilize the SEI growth. Full‐cell testing to assess the ICE and long‐term cycling would be useful for giving a better idea for the scalability of the process. Optimizing the wrapping quality could help with ensuring degradation would be less impactful to the system. Overall, reprecipitation presents an intriguing option for a scalable coating/film‐based modification for µ‐Si anodes, but more work is needed to optimize the industrial electrochemical results for real applications.

3.5. Polymer Coating of µ‐Si Anodes

Polymer coating Si anodes is another method that has been explored toward improving the stability of Si anodes. Polymer coatings have been shown to modify the Si anode–electrolyte interface to promote the uniform transport of Li⁺ ions, accommodate the volume expansion of Si particles, and provide adjustable functional groups to tune the polymer to meet the requirements of the anode [133]. Previous comprehensive research on stabilizing µ‐Si particles for anode materials has often combined specific µ‐Si modifications, with core–shell Si‐based anode materials being a highly represented approach [134]. The impacts of increasing the stability of the µ‐Si allow for it to be usable in larger weight percentages in combination with graphite for anode materials. Compositing with mechanically strong materials can alleviate the impact of the volume expansion for µ‐Si, and structuring the µ‐Si with a strong electrically conductive material such as CNTs or conductive glue (CG) can improve the conductivity, which improves battery performance and long‐term cyclability [135]. A study on stabilizing µ‐Si structures reported that aramid nanofibers (ANFs) were applied to the surface of SMPs, allowing CNTs to form an interconnected network with the ANFs on the surface of Si (Figure 8a) [136]. An in situ dual coating process on SMPs using ANF and CNT allowed for an improved structural stability due to the enhanced mechanical properties introduced from the CNT/ANF network. This improvement in strength was measured by the elastic modulus increasing from 6.45 GPa of pure SMP electrode to 13.65 GPa with the inclusion of the CNT/ANF network in the SMPs. The electrochemical properties of Si were also improved with the mechanical properties, and a high cycling stability was achieved for the CNT/ANF/SMP anode with a specific capacity of 555 mAh g⁻¹ at 100 cycles, while overall anode expansion was reduced by 51.5% after 100 cycles compared to a pure SMP anode (capacity 135 mAh g⁻¹). This work showed a unique approach to stabilizing the SMPs by introducing nanosized materials onto the Si surface and combining them to form a composite of nanomaterials with µ‐Si. While ANFs themselves do not provide desirable conductivities for the SMPs, combining them with other conductive materials such as CNT shows promise for improving both the structural stability and conductivity. This approach has practical application potential, as high cycling stability was achieved when combined with graphite. Adjusting the conductive materials or types of nanofibers will be essential to increase the SMP content compared to graphite for future practical applications.

FIGURE 8.

(a) Synthesis of ANF/CNT/SMP material and its long cycling performance compared with other anode materials. Adapted with permission [136]. Copyright 2024, John Wiley and Sons. (b) Synthesis strategy of Si@PSLB. Full‐cell cycling and rate performances of Si//NCM90 and Si4@PSLB//NCM90. Adapted with permission [137]. Copyright 2023, John Wiley and Sons. (c) Schematic diagram of the structural changes in carbon‐coated SiOx with polymer coating during cycling and the PDA‐mediated interaction between the carbon layer and PAM polymer. Cycling performance of pouch cells paired with NCM811. Adapted with permission [138]. Copyright 2024, Elsevier.

Other work involved polymer coating of µ‐Si, with an emphasis on using the polymer coating for stabilizing the interface of Si particles to improve the performance and mechanical properties. The study from Li et al. demonstrated that engineering a uniform organic/inorganic H‐SEI on µ‐Si particles substantially improved the electrochemical stability of Si anodes in LIBs [137]. A polyhedral oligomeric silsesquioxane‐lithium bis (allylmalonato) borate (PSLB)‐based chelation coating on the Si surface facilitated the formation of a dense, mechanically robust, and ionically conductive SEI layer that effectively accommodated the large volume expansion typically associated with Si lithiation. Electrochemical testing showed that the modified Si anode maintained a reversible capacity of approximately 1083 mAh g⁻¹ after 300 cycles at a current density of 1 A g⁻¹, significantly outperforming untreated µ‐Si electrodes. The coated electrode also exhibited improved CE, reduced impedance growth, and enhanced Li⁺ ion transport kinetics, indicating suppression of continuous electrolyte decomposition and repeated SEI fracture during cycling. Figure 8b presents a schematic illustration of the polymer coating applied to Si structure, along with full‐cell cycling performances of pristine Si and modified Si4/PSLB paired with NCM90 as cathode. The polymer coated Si electrode delivered a specific capacity of ~150 mAh g⁻¹ after 150 cycles, compared to ~90 mAh g⁻¹ for uncoated Si electrode, and also demonstrated improved rate performance over 40 cycles at various C‐rates. In full‐cell testing with a high‐nickel layered oxide cathode, the engineered Si anode achieved approximately 80.8% capacity retention after 150 cycles at 0.5 C, demonstrating improved practical viability beyond half‐cell configurations. Structural and interfacial characterization further revealed that the H‐SEI coating effectively mitigated particle pulverization and electrode swelling by distributing mechanical stress more uniformly across the Si surface. Microscopy analysis showed that the coated electrodes retained a comparatively intact morphology after repeated cycling, whereas uncoated Si experienced severe cracking and surface degradation. Overall, the findings highlight the importance of SEI chemistry and interphase engineering as an effective strategy for enhancing the long‐term cycling stability of µ‐Si anodes for next‐generation LIBs. A water‐processable PEDOT:PSS/PAA (P:PP) layer was post‐coated onto the surface of the fabricated μ‐Si electrode instead of being applied to individual Si particles. The electrode‐level overlayer combines the conductivity of PEDOT:PSS with the strong adhesion and flexibility of PAA. This helps maintain electrical contact, suppress electrode swelling and delamination, and form a stable LiF‐rich SEI. Consequently, the coated electrode retained about 80% of its capacity after 150 cycles and delivered approximately 1618 mAh g⁻¹ after 200 cycles [139].

A polymer‐interface engineering strategy was developed to stabilize micron‐sized SiO _x anodes in LIBs by constructing a functional polymeric interphase on carbon‐coated SiO _x microparticles through a polydopamine (PDA)‐mediated polyacrylamide (PAM) coating, rather than using the polymer as a carbon precursor [138]. In this structure, PDA acted as an adhesive molecular bridge between the carbon surface and the PAM shell, enabling robust coating adhesion and improved interfacial stability. The elastic PAM layer accommodated volume expansion during cycling while simultaneously regulating electrolyte access to the SiO _x surface, thereby mitigating interfacial side reactions and suppressing continuous SEI reformation. Figure 8c shows a schematic illustration of the carbon and polymer coatings on the SiO particles. The long‐term pouch cell results with NCM811 cathodes showed that the polymer‐coated SiO improved the capacity retention from 80% to 85% after 800 cycles compared to the noncoated SiO anode. Electrochemical characterization demonstrated that the PDA‐PAM coating significantly enhanced cycling stability, reduced impedance growth, and improved storage stability compared with unmodified SiO _x materials. The coating promoted formation of a thinner and more stable SEI while preserving conductive pathways within the electrode despite repeated lithiation‐induced volume changes. Importantly, the strategy was validated under commercially relevant conditions using graphite‐blended pouch cells containing 10 wt% SiO _x . These results highlight the importance of artificial polymeric interphase engineering for µ‐Si‐based anodes, where interfacial degradation and mechanical instability remain primary limitations for long‐cycle operation.

4. Binder Design for µ‐Si‐Based Anodes

Design and materials that are incorporated for binders play an important role in the performance of µ‐Si anodes due to their role in maintaining the electrode structure and long‐term cyclability. The most common binder materials used for Si‐based anodes are polyvinylidene fluoride (PVDF) and CMC [140]. Current binder research is more applicable to n‐Si compared to µ‐Si‐based anodes, and current binder material like PVDF have good wettability and chemical stability but are less suitable for high‐capacity Si anodes due to its weak bonding interaction with the Si particles and current collector [141]. A shift in focus for binder systems from n‐Si to µ‐Si has occurred due to high theoretical capacity of µ‐Si and growing interest in commercializing Si‐based anode batteries [142]. This section will explore recent novel binder designs for µ‐Si anodes, highlighting their mechanical properties, flexibility, and chemical compatibility with Si to evaluate their effectiveness in accommodating µ‐Si particles volume expansion.

Research has been performed to stabilize low‐cost raw µ‐Si particles with a novel human‐ligament inspired binder design, which is mechanically strengthened to construct a µ‐Si anode with high cycling life, reversible capacity, and ICE [143]. Figure 9a provides a visualization of the binder design before and after cycling, presenting how the ligament‐based design can enhance the adhesion between the µ‐Si particles, and the current collector and mitigate the volume expansion of µ‐Si particles during cycling. The binder design was a biomimetic binder (PSB), synthesized by thermal crosslinking of PAA, sodium alginate and borax in an aqueous solution. This structure exhibited the flexibility of fibrils in the ligaments and wrapped around µ‐Si particles, effectively accommodating the volume expansion of Si while maintaining the structural integrity. As a result, PSB binder better handled strain concentration and maintained the mechanical stability of Si anode through hydrogen bonding compared to the traditional PVDF binder with van der Waals forces. For half‐cells, µ‐Si electrodes with conventional binders (PAA and PVDF) showed a rapid capacity drop in the initial cycles at high current density due to poor mechanical stability and inability to withstand volume expansion. In contrast, the PSB binder delivered a reversible capacity of ~1500 mAh g⁻¹ with 91.4% capacity retention during 600 cycles at 4000 mA g⁻¹, while PAA and PVDF showed very low capacity and almost no retention (Figure 9a). For the full‐cell testing, the modified µ‐Si was combined with graphite and used with NCM811 cathode to exhibit capacity retention of 91.4% after 200 cycles showing the strong cycling stability when combined with graphite. The ligament‐based binder design holds promise for future binder work for µ‐Si based anodes, and its combined use with graphite in the full cells highlights its potential for commercialization for using low‐cost Si materials. Further work with different precursors could lower the cost of the binder or provide even better stability when incorporating a larger percentage of µ‐Si with graphite. Using even lower‐cost sources of µ‐Si such as metallurgical grade or recycled µ‐Si, could further support industrial adoption by reducing overall material costs.

FIGURE 9.

(a) Schematic of mechanism of PVDF and PSB binders with μ‐Si anodes during cycling and their long‐term cycling stability at 4000 mA g⁻¹. Adapted with permission [143]. Copyright 2024, Elsevier. (b) Schematic of the μ‐Si anodes with PAA and PPC binders during cycling and their stress evolutions after continuous cycling by the finite element method along with half‐cell cycling performances at 0.5 C. Adapted with permission [144]. Copyright 2024, John Wiley and Sons.

Hydrogen bonding is a key factor in enhancing the structural integrity of the binder with the µ‐Si particles, but sufficient electrical conductivity is also important for efficient electron transport in the electrode and maintaining high performance batteries [145]. Combining the mechanical stability and electrical conductivity is a major point in binder materials research [146]. A cross‐linked conductive network binder PPC composed of PAA, polypyrrole (PPy), and citric acid (CA), can establish many hydrogen bonds between PAA and PPy groups facilitated by the CA, while also enabling the conductive polymer to bind to the µ‐Si particles [144]. The combination of many hydrogen bonds and the conductive polymer network allows the PPC binder to mitigate the µ‐Si volume expansion while maintaining electrical contact and conductivity of the active materials. Figure 9b provides a comparison of µ‐Si cycling with only PAA and Super P, and then with the synthesized PPC binder and Super P, showing schematically how the PPC binder holds the µ‐Si particles together during cycling. The PPC binder significantly improved the electrochemical performance of µ‐Si anodes, delivering 2656.9 mAh g⁻¹ after 100 cycles and 1776.7 mAh g⁻¹ after 300 cycles, while PAA showed rapid degradation with only 451.1 mAh g⁻¹. The PPC electrode also recovered capacity to 2063.7 mAh g⁻¹ after electrolyte and Li metal replacement, indicating preserved structural integrity. Simulations further showed that the PPC binder effectively reduced stress during volume expansion through its hydrogen‐bonding network, unlike PAA, which exhibited high stress concentration and structural instability. Future work in this area can combine the µ‐Si with graphite to test its stability at higher temperatures and extended cycling, using conditions more aligned with industry standards to assess the commercialization potential of the PPC binder for µ‐Si anodes.

An amphiphilic poly(ethylene‐alt‐maleic acid) (PECH) binder was developed to reduce the degradation of μ‐Si Anodes. The nonpolar hydrocarbon segments of conventional polyalkyl binders provide limited interaction with the native Si surface. In contrast, PECH contains flexible ethylene segments and rigid polar dicarboxyl groups that interact with conductive carbon and Si, respectively. These complementary interactions form a homogeneous 3D conductive structure. The μ‐Si anode with PECH binder delivered a high specific capacity of 3059 mAh g⁻¹ and retained 81% of its capacity after 100 cycles [147].

PVA, which has a flexible carbon–carbon backbone functionalized with hydroxyl groups, has also been used in multifunctional binders for μ‐Si anodes. Yan et al. developed a PPG binder that combined the elasticity of polyvinyl alcohol (PVA) with a PAA‐conductive graphene framework. The resulting μ‐Si electrode delivered 1913.1 mAh g⁻¹ with 86.7% capacity retention after 1000 cycles at 1 C. It also achieved a capacity of 1451 mAh g⁻¹ at 5 C [82]. Polyurethane (PU)‐based binders provide additional elasticity and adhesion. A 3D PU‐PAA network offered multiple action sites, reduced the slip between the binder and electrode particles, and stabilized both the μ‐Si anode and SEI. The μ‐Si anode demonstrated a high specific capacity of 1934 mAh g⁻¹ after 500 cycles with a capacity retention of 60.9% [148]. More recently, a water‐borne PU (WPU) ionomer containing PTMEG/PEG soft segments and a PEG‐CA polyol showed a strain above 1500%. It also provided approximately twice the peel strength of PAA and increased ionic conductivity by almost one order of magnitude. In μ‐Si half‐cell at 0.2 C, the electrode maintained a capacity of approximately 2.1–2.3 Ah g⁻¹ after 500 cycles, with a CE of at least 99.98% [149]. Functionalized styrene‐butadiene rubber (SBR) provides another relevant polyacrylate‐elastomer binder design. Grafting PAA onto SBR improved its compatibility with Na‐PAA, reduced phase separation, and provided a better balance between flexibility and cohesion. A composite anode containing 30 wt% Si‐50 wt% graphite with the PAA‐g‐SBR/Na‐PAA binder system maintained 673 mAh g⁻¹ after 130 cycles, whereas the anode using the unmodified SBR/Na‐PAA binder rapidly degraded [150].

Binders for µ‐Si anodes must have a combination of mechanical stiffness to hold their structural integrity while also being elastic enough to accommodate volume expansion of Si, which is difficult to achieve with a basic linear structure, must have a system or network to achieve both properties [151, 152]. This combination was achieved by introducing a hierarchical GO/ssDNA binder, which was developed by coating µ‐Si with GO and integrating a flexible single strand DNA (ssDNA), improving structural stability and cycling performance [153]. The electrode delivered 808 mAh g⁻¹ after 450 cycles, significantly outperforming PAA‐based systems in long‐term stability despite a lower ICE. This dual‐layer binder design shows strong potential for µ‐Si anodes, but cost‐effective alternatives to ssDNA are needed for practical applications. Further work on full‐cell cycling and long‐term stability operations should be explored to consider commercializing the binder for LIBs. Using this dual layer approach for binder structures should pave way to future binder materials to incorporate this structure. Combining cheaper binder materials with GO, or incorporating graphite into µ‐Si particles to reduce the amount of binder materials, would be beneficial to improve the overall cyclability. Several examples of various binder materials with electrochemical performances are provided in Table 2 when used in combination with µ‐Si anodes.

TABLE 2.

Various binders used for µ‐Si anodes comparing the specific capacity, current densities, and full/pouch cell performances. These characteristics are key parameters for evaluating industrial scalability.

Binder	Half ‐cell				Full/pouch cell				Reference
	Capacity, mAh g −1	Anode active material loading, mg cm −2	Cycles	Current density/C‐rate	Retention, %	Cycles	C‐rate, C	ICE, %
PEDOT : PSS	2200	0.2–0.4	200	0.2 C	—	—	—	—	[69]
PGG	1913.1	1–2	1000	—	85.1	200	—	—	[82]
CMC‐10% PDA	1700	1.36	1000	0.2 C	80	50	1.0	88.2	[154]
DNB	1115	0.7	300	4.2 A g−1	86	50	0.1	88.8	[155]
PVPA	574	1.84	100	0.5 A g−1	—	150	0.5 A g−1	60	[142]
PAID	2459	0.42	200	0.2 C	—	—	—	—	[156]
APAM	2104.3	0.6–0.8	100	1.8 A g−1	—	—	—	—	[157]
P(AA‐co‐LiAMPS)	587.8	—	400	1.0 C	—	—	—	—	[158]
CSS	~2400	—	100	0.3 C	~81	100	0.5	—	[159]
PAAS/0.08SMTH	1670	1.75	150	0.3 A g−1	~70	30	0.1	—	[160]

5. Electrolyte Design for µ‐Si‐Based Anodes

For Si‐based anodes, the electrolyte plays a vital role in long‐term cycling and mechanical durability of the battery cell [161]. The SEI on Si anodes is dependent on the role of the lithium hexafluorophosphate (LiPF₆) salt present in the electrolyte, which generally impacts the reductive decomposition of the SEI layer [162]. To work toward commercializing µ‐Si‐based anodes, researchers have made progress on finding novel electrolyte technologies to improve SEI stability, overall mechanical stability and reduce unwanted side reactions [163]. Similarly, graphite began to get commercialized when ethylene carbonate was introduced as a novel electrolyte for graphite‐based anodes [164]. In the same way, µ‐Si anodes require a thorough understanding and study of compatible and novel electrolyte materials to achieve industrial commercialization. Liu et al. developed a dipropylene glycol methyl propyl ether (DPMPE)/FEC/LiBOB electrolyte (DPMPE/F/B) that forms a thin, flexible, and LiF‐rich SEI on μ‐Si. This electrolyte reduced volume expansion and interfacial degradation, achieving 93.03% ICE, 95.87% capacity retention after 300 cycles, and stable pouch‐cell performance under lean‐electrolyte conditions [165]. In another study, a nonflammable molten‐salt electrolyte composed of lithium bis(fluorosulfonyl)imide, potassium bis(fluorosulfonyl)amide, and cesium bis(fluorosulfonyl)imide with a specific mole ratio (Li_0.3K_0.35Cs_0.35FSA) was developed to form a robust, inorganic‐rich SEI on µ‐Si. This interphase reduced volume‐expansion damage and enabled the µ‐Si half‐cell to retain 60.7% of its capacity after 100 cycles, with an average CE of 99.5% [166].

Polymer electrolytes have received significant attention in Si‐based anodes research due to their ability to accommodate volume expansion of Si and recover their shape once the volume of Si has returned to the initial state, which can provide a large positive impact on the long‐term stability of the Si anode [167, 168]. Recent work has explored polymer‐based electrolytes with polymerized 1,3‐dioxolane (PDOL) via an in situ polymerization to stabilize µ‐Si particles and suppress pulverization, enhancing the cyclability of the anode [169]. Cheng et al. claimed that this polymerization strategy combines the wettability of a liquid electrolyte with the flexibility of polymer‐based electrolytes. Figure 10a shows a schematic of the overall impact of the polymer electrolyte and the schematic for the polymerization technique used as the mechanism for the PDOL. This developed a quasi‐solid electrolyte with 10% FEC plasticizer that exhibited an ICE of 97.5% with a reversible capacity of 1837.1 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. Its full‐cell Si/PDOL/LFP performance showed a capacity retention of 76.3% after 300 cycles. The PDOL‐10FEC cell showed better rate performance, delivering 3113 mAh g⁻¹ at 200 mA g⁻¹ and 1889 mAh g⁻¹ at 5000 mA g⁻¹, outperforming CLE and PDOL cells which showed lower capacity retention at high current densities. This study shows the promise of PDOL as an electrolyte material for stabilizing µ‐Si anodes compared to traditional liquid‐based electrolytes. Future work could explore different plasticizers at different concentrations to improve the capacity retention for higher cycle numbers to follow in the footsteps of graphite toward commercialization of µ‐Si anodes. Additional studies could test in situ polymerization during common battery assembly conditions or combine PDOL electrolyte in a hybrid system such as a ceramic material (e.g., LATP) or ionic liquids.

FIGURE 10.

(a) Illustration of SMPs anode with polymerized 1,3‐dioxolane (PDOL) electrolyte during cycling with the in situ polymerized mechanism of the electrolyte, and rate performance comparison of SMPs anode with PDOL‐10FEC and CLE electrolyte from 200 to 5000 mA g⁻¹. Adapted with permission [169]. Copyright 2024, John Wiley and Sons. (b) Schematic of cell configuration of solid‐state lithium‐ion batteries with pristine Si/C anode and solid polymer electrolyte (PEO‐LiTFSI). Rate performances and voltage profiles of preinfiltrated Si/C electrodes with PEO‐LiTFSI under various current densities. Adapted with permission [170]. Copyright 2024, American Chemical Society. (c) TEM images of bare Si and fluorinated carbonincorporated SMP (F‐Si), and cycling performance of a 500 mAh pouch‐cell with an E‐Gel electrolyte and NCM811 cathode. Adapted with permission [171]. Copyright 2024, John Wiley and Sons with a Creative Commons CC‐BY 4.0 license.

Novel work in electrolyte materials for µ‐Si‐based anodes includes fully solid‐state electrolytes, including polymer‐based electrolytes. Si has been explored as an emerging anode material for solid‐state batteries due to its low lithiation potential of 0.4 V and its high theoretical capacity and abundance as a resource combined with its environmental benefits [172]. Research on specific solid electrolytes has explored different combinations of µ‐Si anodes using polyethylene oxide (PEO) electrolytes with µ‐Si/carbon anodes [170]. In this work, three different types of micron‐sized, PSi/C electrodes (pristine, prelithiated and reinfiltrated) were tested with the PEO‐based electrolyte to compare the impacts of PEO on different preparations of µ‐Si/Carbon anodes and identify the most efficient design for µ‐Si solid state batteries. Figure 10b shows a schematic of how the electrodes and electrolytes were prepared and their comparison with the electrochemical tests. The study found that prelithiation and preinfiltration improved the electrochemical performance of the solid‐state batteries at higher temperatures, especially when compared to pristine Si/C.The cell with a preinfiltrated Si/C electrode and PEO‐LiTFSi electrolyte half‐cell measured a specific capacity of ~1000 mAh g⁻¹ after 100 cycles under 800 mA g⁻¹ with average C.E. of >98.9%. The preinfiltrated Si/C electrode improved Li⁺ ion transport, reducing polarization and improving active material utilization at high current density. It also showed strong rate capability, maintaining >2500 mAh g⁻¹ when the current density returned to 200 mA g⁻¹ (Figure 10b). It demonstrated that preinfiltration is an effective strategy to improve solid‐state battery performance. This work presents a strategy for designing solid‐state electrolytes with Si‐based anodes and can be viewed as a benchmark for designing experiments to find novel strategies for improving µ‐Si‐based anodes.

Wang et al. developed a zwitterion‐modified quasi‐solid‐state electrolyte (PVIPSE) that stabilizes µ‐Si by equalizing the interfacial potential, homogenizing Li⁺ flux and FEC distribution, and forming a thin, uniform, inorganic‐rich SEI. The μ‐Si anode retained a specific capacity of 2124 mAh g⁻¹ after 200 cycles at 0.5 C, while the μ‐Si||LFP pouch cell retained 93% of its initial capacity after 50 cycles [173]. Other methods of integrating novel electrolyte materials with µ‐Si‐based anodes have been researched to increase the structural stability of the anode materials. Gel–polymer electrolytes (GPEs) use the polymer matrix structure to keep solvents immobilized to improve the stability of the system [174]. GPEs present beneficial properties such as mitigation of electrolyte leakage and flammability while retaining their wettability, making them attractive for safer LIBs and commercialization [175]. Research has been done on novel strategies to integrate µ‐Si with GPEs, such as using electron beam crosslinking to allow for initiator‐free assembly and improving the structural stability of the system [176]. A method was developed for integrating a highly elastic GPE with high‐energy‐density SMP anodes using electron beam‐induced covalent linkages, addressing the structural stability challenge of µ‐Si [171]. SMPs were first coated with a fluorinated carbon layer and then exposed to electron beam irradiation in the presence of GPE precursors, which allowed covalent bonds to form between GPE and SMPs with an interconnected network that can accommodate SMPs expansion during cycling. TEM images of the bare and fluorinated carbon‐incorporated SMPs (F‐Si) are compared in Figure 10c, showing that the F‐Si has a distinct ~20 nm surface layer, while bare Si has a smooth surface with only a native oxide layer. The 500 mAh pouch cell with F‐Si|E‐Gel|NCM811 delivered high energy densities of 413 Wh kg⁻¹ and 1022 Wh L⁻¹, with 77.0% capacity retention after 150 cycles, demonstrating strong stability and performance using µ‐Si without relying on nanoscale designs. GPEs provided high ionic conductivity, which improved the ionic conductivity of SMPs from ~0.2 mS cm⁻¹ for bare Si, at ~0.75 mS cm⁻¹ with the coating and process with an increase in electrical conductivity from ~0.05 to 0.11 mS cm⁻¹. The GPE consisted of PVA with cyano groups (PVA‐CN) and an acrylic compound precursor, which was activated by the electron beam. This research shows the possibilities of integrating GPE with µ‐Si‐based anodes with novel processes to create unique and efficient structures. Long‐term cycle testing, optimization of GPE composition via alternative polymers or additives should be explored to enhance the ionic conductivity and cycling stability beyond those reported in this article. Different structures or coatings can be developed to increase the capability of higher conductivity and mechanically stronger GPE materials. These studies present the vital role of the electrolyte in stabilizing µ‐Si anodes by accommodating volume expansion and improving the overall conductivity of the system. Electrolyte compatibility with industrial‐based fabrication is essential for allowing µ‐Si anodes to become commercialized for modern day LIBs.

Considering both electrochemical performance and manufacturability, no single strategy is universally superior for improving μ‐Si anodes. Table 3 compares the effectiveness, cost‐efficiency, advantages, and limitations of the different approaches for improving μ‐Si anodes based on the reported findings presented throughout the manuscript.

TABLE 3.

Comparative evaluation of the effectiveness, cost‐efficiency, advantages, and limitations of strategies for improving μ‐Si anodes.

Strategy	Effectiveness	Cost‐efficiency	Main advantages	Main limitations
Porous μ‐Si structures	High. Internal spaces and stress‐distributing structures can maintain high Si utilization.	Moderate. Ball milling and some alloy‐based methods are scalable, but etching, pore control, Si loss, and multiple heating or separation steps increase the cost.	It directly accommodates Si expansion, reduces particle cracking, and supports high Si content and fast‐charging.	A high surface area can increase SEI formation and reduce ICE, while excessive porosity lowers tap density and volumetric energy density.
Multicomponent composites	Very high in laboratory cells because its different components strengthen the structure, improve conductivity, and stabilize the SEI.	Low to moderate. Specialty nanomaterials, precise assembly, spraying, heating, and interface‐control steps can increase manufacturing costs.	It addresses mechanical, electronic, and interfacial issues at the same time and is useful for high‐loading, high‐rate, and long‐cycle applications.	Its complex composition makes quality control, large‐scale production, and recycling difficult.
Scalable carbon coating and μ‐Si‐graphite composites	High. Carbon improves conductivity, maintains contact, and reduces the effect of expansion.	High when pitch, biomass‐derived carbon, or simple pyrolysis is used, but moderate when CNTs, graphene, laser processing, or repeated coating steps are required.	It provides a good balance of conductivity, expansion control, tap density, and compatibility with existing graphite‐anode manufacturing.	Carbon and graphite reduce the overall gravimetric capacity, while uneven coatings remain a concern.
Polymer and artificial interphase coatings	High. Elastic coatings limit direct electrolyte contact, relieve stress, and suppress repeated SEI cracking.	Moderate. Polymers are inexpensive at low amount, but uniform coating, solvent recovery and additional processing increase the cost.	It requires a small amount of coating, while its adhesion, elasticity, and functional groups can be adjusted to control swelling and interfacial side reactions.	Coating defects, gradual deformation, poor chemical stability, and uneven thickness can reduce performance.
Multifunctional binders	Very high considering their small material fraction. Conductive cross‐linked binders also maintained high capacity.	Very high. They avoid restructuring the Si powder, use conventional slurry coating, and can use low‐cost materials.	Strong adhesion, elasticity, self‐healing, cross‐linking, and possible electronic or ionic conductivity make this one of the easiest independent strategy to apply in existing electrode production.	A binder cannot fully prevent particle cracking or unstable electrolyte reactions.
Electrolyte modification	High for improving ICE, stabilizing the SEI, enhancing rate capability, and controlling impedance.	High for small amounts of additives, but moderate to low for in situ polymerization, solid polymers, and electron‐beam‐crosslinked gels.	It improves the entire electrode surface without changing particle synthesis, reduces continuous electrolyte decomposition, and supports fast charging.	It cannot fully prevent bulk Si fracture, while high salt content, viscosity, solvent cost, poor wetting, safety concerns, and equipment compatibility may limit large scale production.

6. Economics and Scalability for Commercialization

The economics of battery anode materials plays an important role in allowing a material to transition from a research laboratory to commercialization of the materials for industrial use [177, 178]. There are many different methods that have been explored to lower the cost of using µ‐Si for real world applications, including using recycled Si sources such as waste plastics [179], PV cells [180], industrial waste [181], and metallurgical‐grade Si [182]. Recycled Si has gained strong interest in Si research because it reduces supply cost by utilizing abundant waste sources [183], and provides an environmentally friendly solution for managing waste Si, thereby improving the sustainability of the processes [184]. Implementing waste Si for high‐performance Si‐based LIBs remains a key research focus, as the projected increase of waste Si to around 80 million tonnes (Mt) by 2050 will lead to future challenges involving use and storage of waste Si [185]. However, problems arise when using waste‐derived Si as a source of Si compared to high‐purity, such as presence of metals such as lead, copper, or silver which could introduce hazardous materials or compromise the performance of the cell [186]. Modifications to the battery structure can overcome these challenges. For example, recent work by Liu et al. has used µ‐Si from PV waste as anode material to develop high‐voltage LIBs [187]. This work presented a novel approach to using µ‐Si from PV waste paired with an ether‐based electrolyte, enabling the formation of a dual‐layer SEI with a polymeric outer layer and a rigid inner layer which would support ionic conduction and suppress the side reactions. Its polymeric outer layer helped to hold the fractured Si together, while the Li₂O/LiF‐rich inner layer allowed PV waste‐derived µ‐Si to achieve a CE of 99.94% with a capacity retention of 83.13% after 200 cycles in the half cells. The NCM811||µ‐Si pouch cell delivered a volumetric energy density of 1147 Wh L⁻¹ with a capacity retention of 88.7% after 88 cycles, which was significantly improved compared to previous works pouch cell performance. This work shows the potential for high‐voltage µ‐Si‐based anodes based on modification of electrolyte material to form a more beneficial SEI layer that enables the use of PV waste‐based materials. In this work, the main modification was in the electrolyte and could be further modified with greener electrolyte materials and industry‐based testing, such as calendar aging and abuse tolerance tests. Overall, this work presents a strong contribution to high‐energy‐density LIBs with Si anode research, by implementing economically viable sources of Si that, with further improvements in manufacturing and cycling life, show promise toward commercialization.

PV‐waste‐derived µ‐Si has been explored with various modification strategies to be implemented as an anode material for LIBs. As discussed earlier, SEI stabilization is an important factor for both anode‐grade and waste‐derived Si materials. SEI stability has been shown to be a requirement for reinforcing the mechanical stability and cyclability of Si‐based anode materials [188], and this requirement is even more important for waste‐derived Si due to the presence of impurity atoms, which must be resolved [189]. The benefits of implementing PV waste‐derived Si for waste management are the driving force behind further research on its application, and recent work involving the application of a polymer coating to form a robust SEI around the µ‐Si particle has addressed the volume expansion and unstable SEI while delivering high performance, showing continued innovation [190]. This work addressed the waste‐to‐resource problem of PV‐industry Si scrap by coating it with a fluorinated polymer (TFEMA) crosslinked with KH570 to form a stable SEI layer, as shown in Figure 11a. The Si@TFEMA||LFP full‐cell demonstrated a capacity of 131 mAh g⁻¹ with 90% capacity retention after 100 cycles, showing a significant improvement compared to bare Si scrap. The electrochemical tests done with the Si@TFEMA electrode showed a high ICE of 90.2% at a current density of 0.2 A g⁻¹, which was an improvement over pristine Si, which exhibited 85.1%. This work presents strong environmental and economic benefits by reusing Si waste and improving battery performance. The fluorinated coating stabilizes the SEI and enables the use of µ‐Si, but further studies on scalability, cost, and comparison with other cutting‐edge methods are needed for industrial adoption.

FIGURE 11.

(a) Schematic diagram of PV Si scrap with a LiF‐induced strategy, where crosslinking between silane coupling agent (KH570) and trifluoromethyl ethyl methacrylate (TFEMA) enables fluorinated terminal groups on Si scrap to promote fast formation of a LiF‐rich SEI. Cycling performance of full coin‐cell and pouch‐cell using Si and Si@TFEMA as anode. Adapted with permission [190]. Copyright 2025, Elsevier. (b) Cycling performance and impedance comparison of commercial graphite with 3D‐printed recycled PV cell Si anode. Adapted with permission [191]. Copyright 2025, Royal Society of Chemistry with a Creative Commons CC‐BY 3.0 license.

Various methods for recycling PV waste have been explored; however, challenges related to material processing and structural stability have limited their widespread application. A novel approach was developed to address both issues by recycling Si from discarded PV cells and converting it into functional anodes for LIBs through advanced 3D‐printing techniques [191]. By integrating materials recovery with additive manufacturing, this work aimed to demonstrate a sustainable pathway for transforming solar panel waste into high‐value energy storage components. The integration of 3D printing contributed to the sustainable outcomes of µ‐Si anodes and enabled them to compete with or surpass the electrochemical performance of industry standard anode materials like graphite. A comparison of specific capacity and impedance between the PV‐recycled, 3D‐printed Si anodes and industry standard graphite is shown in Figure 11b. The 3D‐printed samples maintained 89% capacity retention and 100% CE, which were substantially higher compared to commercial graphite anode, with a capacity retention of 66% over 200 cycles. An EIS graph in Figure 11b shows a charge‐transfer resistance of 35.56 Ω which was found comparable or lower to similar studies as well as much lower than commercial graphite resistance of 577 Ω. The samples tested only contained 12% Si active material, suggesting strong potential to increase the Si ratio with improved processing, materials selection, or advances in 3D‐printing technology. Strategies that could be implemented to improve the scalability of the process include industrial engineering approaches such as life cycle assessments for both the PV cells and recycled Si anodes, performing in situ characterization to examine the changes in structure of the 3D‐printed anodes compared to traditional µ‐Si anodes. Long‐term, high‐loading, and full‐cell testing must be explored to increase the confidence and depth of the technology, especially for implementation in industry research and design. In addition, exploring more advanced 3D‐printing materials and continuously evaluating new 3D‐printing technologies could further enhance performance. Overall, the work being done on PV waste shows promise not only as a method of providing cheap, easily accessible Si for the battery industry, but also as a potential solution to the problems involving waste management in PV industry for its nonrecyclable Si materials. Future work on novel modifications of waste‐derived Si could open the door to collaboration between the PV and battery industries to improve logistics and future technologies for their respective industries. In addition to industrial waste sources, sectors like agricultural industry have potential to provide a cheap source of Si for LIBs [192]. Previous work has explored rice husks as a potential source of n‐Si anodes, offering a cheap and sustainable source of Si [193]. Most of these works have been done on n‐Si, with limited discussion and exploration for µ‐Si anodes in relatively recent years, which has exhibited lower performance compared to n‐Si [194]. Rice husks as raw materials show promise as a source of Si due to increasing issues with waste control in the agricultural industry [195]. For µ‐Si‐based anodes derived from rice husk waste, a work involving developing a nitrogen doped composite material of carbon/SiO _x derived from rice husks was explored at the microscale, but this was still not fully implemented as µ‐Si [196]. This work can still pave the way for future biomass‐derived µ‐Si anodes as a potential area for research strategies similar to the PV industry.

Expanding sources of µ‐Si to more industries besides PV cells would provide new incentives between the industries to develop industrially viable products and aid waste management in the industry providing Si. While also allowing for cheap and sustainable manufacturing methods of Si‐based anodes which can help to bridge the gap between laboratory research and industrial applications by providing mutual economic benefits.

7. Perspective and Future Works

The evolution of µ‐Si anodes for LIBs has witnessed various advancements throughout the past decade. As the field continues to broaden its research and mature key research directions must balance the electrochemical performance optimization with industrial integration, manufacturing and system‐level challenges. Progress has been made in optimizing the design of the µ‐Si structure with 3D PSi, and novel structural engineering accomplishments such as planar‐shaped Si. Electrolyte designs have also been researched extensively with new polymer‐based solid electrolytes. Binder design advancements, in combination with coating and doping elements, introduced to the Si structure have shown promising performances when considering the poor cycling life of bare Si. However, with these advances in µ‐Si anodes, associated with the challenges in commercialization of µ‐Si still have a long way to go to be considered over graphite for modern‐day anode materials. As shown throughout this review, many of the substantial improvements that have been made toward developing high‐performance batteries with µ‐Si have lacked the proper testing needed to compare them with the benchmarks required for integrating laboratory research toward industrial commercialization. There are still many methods to improve upon the research that has been done on µ‐Si‐based anodes, and these will be explored as future research directions based on the discussions presented.

Advanced anode architectures based on industrial‐scale synthesis processes would be a key factor in advancing high performance Si anodes toward industrial applications. Designing structures that can withstand ~300% volume expansion will improve cycle life; while simple, low‐cost designs that easily integrate into existing manufacturing processes are essential for commercialization of µ‐Si anodes. Combining mechanical stability with cost‐effective processing can be achieved by combining current research approaches for µ‐Si, such as using recycled PV waste as the source of µ‐Si and synthesizing a mechanically stable design that can overcome the challenges with volume expansion and electrical conductivity. Recycled Si must be further explored for µ‐Si anodes, as it can help address waste management challenges while providing a low‐cost and sustainable material source. This can reduce costs of manufacturing and encourage the transition from graphite‐dominant materials to the integration of Si into industrial processes.

Combining design improvements for µ‐Si anode research with current‐day graphite anodes would be another key strategy to implement µ‐Si into industrial applications. It is an expensive and time‐consuming process to completely overhaul industrial processes to accommodate new, innovative µ‐Si‐based materials. This is a key reason that implementation of Si‐graphite is pushing the industry toward integrating novel, cutting‐edge research for µ‐Si. Many modern EV and battery manufacturers have begun to slowly implement Si into their battery materials with graphite, since it is currently what works best for commercializing Si‐based anodes compared to using pure or very high percentages of Si in anode materials. As seen in this review, many researchers used their modified Si materials directly as anodes, which shows strong performance for their laboratory‐based research, but like n‐Si research, a gap remains between these researches and practical commercialization of the materials. Integration of high‐ratio Si anodes with graphite is a key step for advancing µ‐Si anodes, as it helps to reduce issues such as volume expansion and unstable SEI. The maximum potential amount of Si wt% content used in the anode material is estimated to be around 25%–30% with today's technology and research [197]. Hopefully, with more research toward µ‐Si anodes rather than nanosized Si, more improvements and mechanisms can be discovered and implemented to increase the total optimal amount of Si wt% for anode materials.

SEI and electrolyte engineering play a key role in prospects for µ‐Si anode materials as the SEI stability is a key challenge to overcome for stable Si‐based anodes. Novel additives discussed in this review such as fluorinated solvents, localized high‐concentration electrolytes and solid‐state electrolytes have yielded improvements in laboratory studies, but further development is needed for commercial viability. Novel binder designs can lead to dual layer structures that can both enhance the mechanical stability of Si and improve its electrical conductivity. New solid‐state electrolyte materials continue to be a relevant topic for electrolyte research and combining that technology with µ‐Si‐based anodes could lead to a breakthrough within both fields for battery research. Other research areas that can lead toward practical integration of cell architectures include all‐solid‐state batteries, high‐power EV packs, and flexible devices, which can provide solutions for the challenges of integrating µ‐Si materials into anode technology. This is where nano‐scale research can help bridge the gap for µ‐Si anodes, with more research work focused on micro‐scale Si, combining the beneficial properties of both n‐Si and µ‐Si. With sustainability, cost, and performance at the forefront of battery research, µ‐Si‐based anode materials can become the cornerstone of high‐performance LIBs technology.

Author Contributions

O.C.B. and O.G.S. contributed equally to write the manuscript. J. J. N. revised the manuscript. All authors participated in the discussion.

Funding

This study was supported by the Ignite Grant Program for Applied Research Award (FY26‐106‐068000‐4) and UWM Discovery and Innovation Grant (DIG) award.

Conflicts of Interest

The authors declare no conflicts of interest.

Bellevage Owen Cameron, Shovon Osman Goni, Nosrati Ali, Islam S. M. Shaikhul, Niu Junjie, Micro‐Silicon as Anodes for High‐Cycle‐Life Lithium‐Ion Batteries, ChemSusChem 2026, 19, e70983. 10.1002/cssc.70983

Data Availability Statement

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.