Polymer Engineering for Stable Zinc Metal Anodes: From Molecular Design to Integrated Strategy

ABSTRACT

Aqueous zinc‐ion batteries (AZIBs) are regarded as a promising energy storage system due to their high safety and low cost. However, the severe dendritic growth, hydrogen evolution reaction (HER), and interfacial corrosion/passivation of zinc metal anodes, which are coupled failure modes, severely limit their cycle life and commercialization progress. Due to their highly tunable molecular structures and inherent multifunctionality, polymer materials offer a systematic solution to these interconnected failure mechanisms. This review aims to elucidate how to achieve synergistic effects through rational polymer design, which encompasses ion transport regulation, side reaction suppression, mechanical buffering, and electrolyte environment optimization. In addition, four main polymer strategies were systematically reviewed: direct modification and protection of the electrode‐electrolyte interface with polymer artificial interface layers; conversion of inert separator layers into functionalized components with polymer‐modified separators; and upgrading from a physical host to a multifunctional integrated electrode with polymer‐based 3D current collectors. Finally, this article points out that future efforts to promote the practical application of high‐performance, long‐life AZIBs should focus on: the utilization of intelligently designed interfaces, the development of electrolytes with wide voltage windows, the implementation of multiscale computational simulations, and the establishment of sustainable polymer systems.

This work elucidates the multifaceted degradation mechanisms of zinc metal anodes, detailing the concurrent processes of dendrite formation, hydrogen evolution, and parasitic water‐induced de‐solvation. It highlights how these factors lead to surface passivation and severe capacity decay. The study provides critical mechanistic insights and proposes effective strategies to suppress these detrimental reactions, offering essential solutions for advancing stable aqueous zinc‐ion batteries.

1. Introduction

The increasingly severe energy crisis and the demand for global sustainable development have jointly driven the pursuit of a new generation of high‐performance, low‐cost, and inherently safe energy storage systems. In this context, aqueous zinc ion batteries (AZIBs) have become a current research hotspot due to their advantages of avoiding the flammable and explosive risks of organic electrolytes, low cost, and high theoretical capacity [1]. In this context, zinc metal anodes (ZMAs) are considered ideal for batteries due to their high theoretical capacity, high abundance, and suitable redox potential [2, 3]. However, in practical applications, zinc negative electrodes still face many challenges such as dendrite growth, hydrogen evolution reaction, interface passivation, and corrosion. These side reactions do not exist independently, but are closely related and mutually reinforcing, forming an unbreakable vicious cycle that ultimately leads to battery failure [3, 4, 5].

To address these challenges, researchers have developed various strategies, including constructing artificial interfacial layers, optimizing electrolytes, designing separators, and building 3D current collectors [5, 6, 7, 8]. Polymer materials, with their precisely designable molecules, ease of processing, and capacity for multifunctionality, offer unique advantages in all these strategies [8, 9, 10]. Through precise molecular engineering, polymers can be endowed with various functions such as guiding ion transport [11], inhibiting side reactions [12] and buffering mechanical stress [13, 14], which are expected to provide systematic solutions. However, current research mostly focuses on the performance of polymers in a specific component (such as a single coating or gel electrolyte) in isolation, lacking a unified design paradigm and in‐depth review that starts from the essence of polymer structure‐property and can coordinate its functions across components and scales to systematically address coupling failures [14, 15].

This article provides some insights into the multifunctional integrated design framework for stable zinc metal anodes (ZMAs) for the first time. Our aim is to elucidate how the rational design of polymers, from molecular to mesoscopic scales [16, 17], can synergistically integrate multiple functions: such as ion transport regulation, side reaction inhibition, mechanical buffering, and interfacial stabilization: into zinc metal anodes (ZMAs). This integrated approach systematically decouples and inhibits the failure network of ZMAs [18, 19]. This article first discusses the thermodynamic and dynamic roots of coupling failure in ZMAs; Then, the molecular design principles and mechanisms of multifunctional integration of polymers were explained; Subsequently, the latest progress and design logic of polymers in four main strategies were systematically reviewed: artificial interface layers [20], electrolytes [21], separators and 3D current collectors. Finally, current challenges are summarized, followed by an outlook toward intelligent and sustainable future directions [22]. We hope this article can provide clear insights and a unified design framework for the design of high‐performance ZMAs based on polymer molecular engineering [23].

2. Coupling Failure Mechanism of ZMAs in Aqueous Electrolytes

The failure of ZMAs is a typical multi‐scale, multi‐physics field coupling process [24]. The four core issues‐dendritic growth, HER, corrosion behavior, and interface passivation are thermodynamically spontaneous and kinetically interrelated. Their mutual exacerbation creates a chain reaction [25]. Consequently, a deep understanding of the underlying thermodynamic driving forces, kinetic pathways, and crucially, their synergies is essential for developing rational and efficient anode protection strategies.

2.1. Dendritic Growth

Dendritic growth is the primary cause of internal short circuits in AZIBs. It originates from a mass transfer crisis at the electrode interface. According to the typical Chazalviel space charge model (Sand's time model), under constant‐current, zinc ions (Zn²⁺) at the electrode interface are continuously consumed due to continuous reduction, and their mass transfer process can be described by Fick's law Equation (1). When deposition reaches the critical Sand's time, the concentration of interface cations approaches zero [26].

$$\tau =\pi D{\left(zF{C}_0/2J\right)}^2$$ (1)

Among them, τ is the Sand's time, D is the diffusion coefficient of Zn²⁺, C₀ is the bulk concentration, J is the current density, z is the charge number (Zn²⁺ is 2), and F is the Faraday constant. Equation 1 clearly shows that the dendrite initiation time (τ) is inversely proportional to the square of the current density and directly proportional to the square of the concentration.

The Sand's time (τ) model quantitatively describes the incubation period before dendrite onset. Polymer engineering offers precise control over these variables to kinetically suppress dendrites. First, polymers reduce the effective diffusion coefficient (D)​ by creating tortuous nanochannels, hindering mass transport. Second, by anchoring anions or introducing cationic groups, polymers increase the Zn‐transference number (tZn²⁺), which mathematically enhances the term, leading to a quadratic increase in π. Third, functional groups (e.g., ─CN, ─C═O) regulate the local current density (J)​ by homogenizing the flux across the electrode interface. Our recent work on the PVA/Bmim[ZnBr] supramolecular gel exemplifies this synergy; the polyanionic clusters immobilize anionic species to boost to 0.61, while the optimized solvation structure lowers the de‐solvation energy barrier, collectively extending the Sand's time and enabling ultra‐stable cycling [8].

Following this concentration depletion, charge neutrality is broken, leading to the formation of a space charge region. The internal electric field strength E in this region, whose characteristic thickness relates to a modified Debye length, can be approximated by (Equation 2):

$$E=\left(J/\epsilon \right)t\left(whent>\tau \right)$$ (2)

where ε is the dielectric constant of the electrolyte, and t is the time elapsed beyond τ. This intensified electric field then governs ion migration, overriding the previous diffusion‐controlled mechanism.

Electric field instability is epitomized by the tip effect: any protrusion with a curvature radius r experiences a locally enhanced electric field, E local ≈ E × (h/r) (where h is the protrusion height), directly enabling the positive feedback loop for dendrite growth [27]. Concurrently, electrocrystallization kinetics critically influence deposition morphology. Thermodynamically stable (002) crystal planes favor lateral growth, promoting flat deposition, whereas (100) and other planes grow faster, predisposing to vertical dendrite formation [28]. Once micro‐scale protrusions emerge, the coupling of the “tip effect” and “shielding effect” creates a self‐reinforcing vicious cycle [29]. Furthermore, the mechanical stress from growing dendrites can puncture protective interfacial layers, exposing fresh, highly active zinc surfaces that catalyze side reactions [30].

2.2. Hydrogen Evolution Reaction

HER poses a significant challenge in AZIBs, not only causing gas generation and swelling but also initiating a detrimental cycle of irreversible side reactions. This process severely corrodes the interface and lowers Coulombic efficiency, ultimately compromising the battery's integrity and lifespan [31].

The redox potential of zinc (−0.76 V vs. SHE) is much more negative than the equilibrium potential of HER (0 V vs. SHE) in neutral water, making HER thermodynamically spontaneous [32]. Furthermore, the hydrolysis of Zn²⁺ and its complexation with OH– render commonly used electrolytes weakly acidic Equation (3 and 4) [33]. The Pourbaix diagram of zinc confirms that metallic zinc is unstable in such acidic media. Without an effective artificial electrode/electrolyte interface (AEI), direct contact between zinc and the acidic electrolyte leads to spontaneous corrosion and hydrogen gas evolution. During operation, continuous HER will consume H⁺ and produce OH⁻, causing local alkalization of the interface Equation (6 and 7). According to the Nernst equation, alkalization causes a negative shift in the equilibrium potential of HER, significantly reducing its overpotential and further accelerating the HER kinetics Equation (8 and 9).

$$\mathrm{Zn}{{\left({\mathrm{H}}_2\mathrm{O}\right)}_6}^{2+}\to \mathrm{Zn}{\left({\mathrm{H}}_2\mathrm{O}\right)}_5{\left(\mathrm{OH}\right)}^{+}+{\mathrm{H}}^{+}$$ (3)

$$\mathrm{Z}{\mathrm{n}}^{2+}+\mathrm{O}{\mathrm{H}}^{-}\rightleftharpoons \mathrm{Zn}{\left(\mathrm{OH}\right)}^{+}$$ (4)

$$\mathrm{Zn}+2{\mathrm{H}}^{+}\to \mathrm{Z}{\mathrm{n}}^{2+}+{\mathrm{H}}_2\uparrow$$ (5)

$$2{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2$$ (6)

$$2{\mathrm{H}}_2\mathrm{O}+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2+2\mathrm{O}{\mathrm{H}}^{-}$$ (7)

$$\mathrm{E}\left(\mathrm{Z}{\mathrm{n}}^{2+}/\mathrm{Zn}\right)={\mathrm{E}}^{\circ }(\mathrm{Z}{\mathrm{n}}^{2+}/\mathrm{Zn})-\left(\mathrm{RT}/\left(2\mathrm{F}\right)\right)\ast \ln \left(1/\left[\mathrm{Z}{\mathrm{n}}^{2+}\right]\right)$$ (8)

(9)

This self‐accelerating cycle constitutes the primary chemical driver for subsequent corrosion and passivation processes [34].

The efficacy of polymer‐based protection against HER is intrinsically linked to their ability to modulate the hydrolysis equilibrium of hydrated zinc ions. As discussed above, the reaction serves as a dominant proton source. Here, the role of polar functional groups (e.g., ─CN, ─C═O, ‐SO₃ ⁻) within the polymer matrix becomes pivotal. Through strong Lewis acid‐base interactions, these groups preferentially coordinate with, effectively displacing water molecules from the primary solvation sheath. This de‐solvation process​ not only lowers the activation energy for transport but, more importantly, disrupts the hydrolytic cycle by removing the ligand water molecules necessary for generation.

A quintessential example illustrating this mechanism is the recently developed PVA/Bmim[ZnBr] supramolecular gel electrolyte [8]. In this system, the polyanionic species act as electron‐withdrawing entities that redistribute the electron density around the PVA sites. This modulation enhances the chemisorption affinity of these sites for, effectively ‘locking’ the zinc ions within the polymer network. By sequestering and replacing its hydration shell with stable coordination bonds, the polymer matrix fundamentally alters the local chemical environment, shifting the hydrolysis equilibrium far to the left and starving the anode surface of the protons required for the HER. This case underscores that advanced polymer design transcends simple physical barriers, operating instead through sophisticated molecular‐level manipulation of solvation thermodynamics [35].

2.3. Corrosion Behavior

Zinc corrosion occurs persistently during both battery storage and cycling, serving as the main contributor to self‐discharge [36]. It involves both electrochemical corrosion (e.g., Zn dissolution via micro‐galvanic couples) [37] and chemical corrosion (where dissolved Zn²⁺ reacts with OH^–, SO₄ ^2–, etc., to form insoluble basic salts) [38]. During cycling, the repeated deposition and stripping of zinc continuously expose fresh, highly electrochemically active surfaces. In the alkalized interface microenvironment, this significantly accelerates the hydrogen evolution reaction (HER) and corrosion. The OH^– generated from these reactions further reacts with Zn²⁺ to form a non‐conductive layer of basic zinc salts [39]. This byproduct layer, which often deposits unevenly, not only passivates parts of the zinc as electrochemically inactive dead zinc but, more critically, severely disrupts the local electric field and ion flux. This distortion leads to highly non‐uniform current distribution, creating ideal conditions for rampant dendritic growth and ultimately compromising the structural integrity of the electrode [40].

2.4. Interface Passivation

The passivation layer is a direct byproduct of dendritic growth, HER, and corrosion, typically consisting a dense inner layer of ZnO/Zn(OH)₂ and a porous outer layer of basic salts. Its insulating or semiconducting properties significantly increase the interfacial impedance [41]. Over long‐term cycling, this layer is not static. Mechanical stress from dendrite growth, gas pressure from HER, and electrode volume changes cause it to fracture and reform [42]. The fresh zinc surface exposed at the fracture site immediately triggers more intense side reactions, resulting in the regeneration of a thicker, less performing passivation layer. This dynamic process continuously consumes active materials and electrolyte [43].

2.5. Summary

In summary, the four major failure modes constitute a strongly coupled failure network (Figure 1) [44]. (1)​ Dendrites increase the active surface area and generate mechanical stress, which exacerbates HER and corrosion, and can puncture the passivation layer. (2)​ The alkaline environment produced by HER promotes the precipitation of corrosion products, thickens the passivation layer [45], and gas bubbles distort current distribution. (3)​ Corrosion products are the primary components of the passivation layer and can themselves act as sites for new dendrite nucleation. (4)​ The rupture of this passivation layer then re‐exposes fresh zinc, restarting the entire vicious cycle. Therefore, addressing these interlinked issues requires a systematic and comprehensive strategy that leverages synergistic effects, a principle that guides the subsequent discussion of polymer design [42] (Table 1).

FIGURE 1.

Schematic diagram of zinc anode coupling failure mechanism.

TABLE 1.

Multi‐target regulation by polymer engineering: resolving interrelated challenges of Zn anodes.

Failure mode	Polymeric targets	Mechanistic insights	Typical functional groups/structures
Dendrites	Mechanical confinement layer	High‐modulus confinement	Cross‐linked aromatics
	Homogeneous nucleation induction	Nucleation guidance	Fluorocarbon‐based​
HER	Water‐depleting layer	Hydration suppression	Carboxylate
	De‐solvation medium	Kinetic acceleration	Crown ether ring
Corrosion	Physical shielding	Barrier protection	Dense cross‐linked structure
	Interface pH buffering	Proton scavenging	Zwitterionic groups
Passivation	Facet control	Anisotropic deposition	Bulky chain segments
	Dissolve by‐products	Solubilization	Multidentate chelation
Multifaceted failure	Hierarchical architecture	Synergistic modulation	Hierarchical composites

3. Polymer Materials

Polymers have unique advantageous combinations, among which the most important are their excellent molecular designability and rich functional groups [46]. Due to this advantage, polymers are considered as the basis for multifunctional integrated design [47].

Evaluation of Gibbs free energy for coordination between polymer functional groups and Zn²⁺. Density Functional Theory (DFT) calculations indicate that the substitution of molecules in the primary solvation sheath by polymer ligands (e.g., ─CN, ─C═O) results in significantly negative values, typically ranging from to kJ mol⁻¹. For instance, recent computational studies report values as low as kJ mol⁻¹ for the interaction, which is substantially more favorable than the coordination [48]. This large, negative provides the fundamental driving force for the spontaneous formation of a robust polymer‐coordination layer, effectively disrupting the hydrogen‐bonding network of bulk water. This thermodynamic perspective underpins not only subsequent solvation structure reconstruction and dielectric modulation but also the facet‐selective regulation of Zn deposition, as elaborated below. The preferential orientation of the thermodynamically stable Zn (002) plane induced by polymers follows three interconnected mechanisms:

1. Facet‐selective chemical adsorption: Polar functional groups (e.g., ‐OH in PVA, ‐C≡N in PAN) exhibit differential binding energies to Zn crystal facets, with stronger adsorption to the (002) plane than to the more reactive (100)/(101) planes. This selective adsorption acts as a kinetic cap on high‐surface‐energy facets, suppressing vertical dendrite initiation.

2. Reduced solid‐liquid interfacial energy: Polymer adsorption reconstructs the inner Helmholtz plane at the electrode/electrolyte interface, effectively lowering the solid‐liquid interfacial energy of the (002) plane. Per Wulff's theorem, this energetic favorability promotes the lateral expansion of the (002) plane over other orientations, providing a thermodynamic basis for the observed texture evolution.

3. Suppressed nucleation overpotential: The stabilized (002) interface reduces the Gibbs free energy barrier for nucleation, which manifests experimentally as a decreased nucleation overpotential. This kinetic facilitation steers Zn atoms to attach preferentially to the (002) lattice, avoiding random nucleation on high‐energy facets.

Beyond directly displacing water molecules from the primary solvation shell, polymer architectures also reshape the macroscopic dielectric landscape​ of the interfacial microenvironment. This dielectric confinement reconstructs the electrical double layer at the anode interface. For instance, in EMIM[OAc]‐modified Zn–I₂ batteries, the imidazolium cation embeds into a lean‐water inner Helmholtz plane while OAc⁻ inerts the solvation sheath, effectively lowering the local dielectric/reactivity and enabling >18 000 cycles [48].

While the above dielectric and solvation effects operate at the molecular scale, polymer engineering further exerts control via nanoscale confinement within cross‐linked networks.

Therefore, by adopting a collaborative strategy, the coupling failure of ZMA can be improved, and its mechanism of action and design principles are mainly reflected in the following four aspects [49].

3.1. Inhibiting Dendritic Growth

Uneven ion flow and anisotropic electrocrystallization are the root causes of dendritic growth. Polymer materials are characterized by unique advantages and designability. They can regulate this issue in two ways; chemical regulation guided by functional groups: Polymers containing polar functional groups can coordinate with Zn²⁺, achieve uniform ion distribution, reduce nucleation barriers, and guide uniform zinc deposition [50, 51]. Physically, structural confinement​ can be achieved by constructing a 3D porous polymer skeleton or combining it with a 3D current collector. This architecture​ provides ample deposition space, thereby​ significantly reducing the local current density and forcing​ zinc to deposit in an ordered, lateral filling mode rather than through disordered vertical protrusion [52].

3.2. Suppressing Side Reactions

The occurrence of HER and corrosion relies on the direct contact and catalysis between water molecules and active species on the zinc surface. Polymers suppress these reactions via two principal strategies. First, a dense, continuous polymer layer can act as a physical barrier, preventing water molecules and dissolved oxygen from reaching the zinc surface [53]. Strong coordinating groups (such as ether oxygen bonds, cyano groups) can competitively enter the primary solvation sheath of Zn2+, partially replacing coordinated water to form a stable composite structure, thereby reducing water activity and HER tendency from the root [54, 55].

3.3. Maintaining Integrity Interface

The significant volume change of zinc during the deposition/stripping process can damage rigid interfaces, while the accumulation of byproducts can thicken the passivation layer. While high‐modulus rigid polymer based artificial interphase layers (e.g., dense inorganic coatings, highly crosslinked polymers) are effective at resisting initial dendrite penetration, they suffer from a critical thermodynamic trade‐off: excessive stiffness leads to low fracture toughness and poor interfacial compliance, making the coating prone to cracking under the >300% volume fluctuation of Zn anodes, which creates shortcuts for dendrite penetration.

The viscoelasticity and flexibility of polymers can adapt to the volume strain during cycling, and strong interface interactions (chemical bonds, hydrogen bonds) can be designed to prevent coating delamination [56, 57]. By utilizing supramolecular interactions or introducing dynamic covalent bonds, polymer networks are constructed. When damage occurs at the interface, they can spontaneously repair, thereby dynamically maintaining the integrity and protective function of the interface [58, 59].

3.4. Bulk Environment Optimization

There are currently two main approaches to solve this problem. The first is the construction of a gel/quasi‐solid electrolyte structure: fixing liquid electrolytes in a polymer network, which reduces water activity through nanoconfinement effects and broadens the electrochemical window [60, 61]. Selective ion transport pathway design: Through chemical modification of the polymer matrix (introduction of charged groups, design of pores), creating preferential transport channels for Zn²⁺, improving its transference number [62, 63].

Overall, the core value of polymers in aqueous zinc ion batteries lies in their ability to organically integrate various functions such as inhibiting dendrites, blocking side reactions, buffering mechanical stress, and optimizing ion transport into a material system or integrated interface through sophisticated molecular design, as summarized in Table 2 [46, 64, 65]. This integrated design approach precisely addresses the crux of the interrelated failure modes of zinc negative electrodes [66]. The specific strategies described in the following text are the embodiment of putting this integrated concept into practice at different components and structural levels of batteries [9, 67] (Figure 2).

TABLE 2.

Summary of multi‐functional integrated design and molecular engineering strategies for polymer materials.

Polymer Core Function	Mechanism of Action	Targeted Failure Mode	Embodiment in Strategies	Key Design Elements
Guiding Uniform Ion Transport/Deposition	1. Polar functional groups (‐OH, ‐CN) coordinate with Zn2+ to homogenize the interface ion concentration. 2. Construct a 3D structure to reduce local current density and guide lateral filling deposition.	Dendritic Growth	interface layer/separator/3D current collectors	Zinc affinity, pore structure, and charge density of functional groups
Suppressing Side Reactions (HER/Corrosion)	1. Physically block water molecules and dissolved oxygen. 2. Strong ligands (such as ‐CN) competitively enter the Zn2+ solvation sheath, replacing water molecules and reducing water activity.	Corrosion	interface layer/electrolytes	Hydrophobicity, coordination strength with Zn2+, and network density
Providing Mechanical Flexibility & Adaptive Interface	1. The viscoelasticity of the polymer adapts to the volumetric strain of Zn deposition/stripping. 2. Introduce dynamic bonds (such as reversible covalent bonds, hydrogen bonds) to achieve interface self‐healing.	Passivation Layer Instability	interface layer	The flexibility, dynamic bond types, and interfacial binding energy of polymer chains
Optimizing Bulk Ion Transport Environment	1. Construct nano confinement in polymer network (gel electrolyte) to reduce water activity and broaden voltage window. 2. Design selective ion channels (such as introducing charged groups) to increase the Zn2+ migration number.	Accelerated Side Reactions	electrolytes/ separator	Network cross‐linking degree, functional group properties, and solvent limitation state

FIGURE 2.

Schematic diagram of multifunctional integrated design principles for polymers.

4. Polymer‐Stabilized ZMAs Strategies: From Interface to Architecture

There have been many diverse research works utilizing the multifunctional integrated design strategy of polymers. These works mainly involve introducing Polymer based artificial interphase layers with uniform ion transport, suppressing side reactions, and maintaining high mechanical strength. Systematically categorized as: polymer artificial protective layer [68, 69], polymer‐based electrolyte [62, 70], polymer modified separator [71, 72] and (4) polymer 3D current collector [73, 74]. This chapter will examine these strategies in turn, detailing their mechanisms, advantages, and limitations.

4.1. Polymer Artificial Interfacial Layer

A direct strategy to address instability issues is to construct a polymer interfacial layer on the ZMA, which modifies the local electrochemical environment. The core of this approach lies in introducing a multifunctional barrier, which must simultaneously facilitate uniform ion transport, inhibit side reactions, accommodate volume changes, and maintain mechanical integrity [75]. Depending on the construction method of the interfacial layer and its binding mechanism with the zinc substrate, the main strategies can be categorized into three types: coating [53, 76], in situ polymerization [77, 78] and self‐assembly [79, 80]. These strategies reflect an evolutionary path from physical isolation to chemical bonding, and ultimately to molecular precision design (Table 3).

TABLE 3.

Summary of different of polymer artificial interface layer strategies.

Strategy	Construction method	Core mechanism and advantages	Key challenges	Ref
Coating	Pre synthetic polymer solutions for physical coatings such as scraping, spin coating, and spray coating	The process is simple and easy to scale up	Weak interface bonding and difficult uniformity control	[81]
In situ Polymerization	Directly initiate (electrochemical/chemical/photochemical) monomer polymerization on the surface of Zn	The interface has strong bonding (can form covalent/coordination bonds) and good adhesion	The process is more complex and requires precise control of polymerization conditions	[77]
Self‐assembled Monolayer, SAM	Functional molecules spontaneously align on the surface of Zn through chemical adsorption/intermolecular forces	Molecular level precision interface control, ultra‐thin (∼nm)	Mechanical strength and long‐term stability are limited, making it difficult to withstand drastic volume changes	[82]

4.1.1. Coated Polymer Protective Layer

The coating method is to cover the surface of the ZMA with a pre synthesized polymer solution through simple scraping, spin coating, or spraying methods to form a protective layer [83, 84]. This method is simple to prepare and easy to prepare on a large scale, and is currently the most fundamental method for constructing polymer based artificial interphase layers [85].

Early researchers used polymers such as polyvinylidene fluoride (PVDF) as polymer based artificial interphase layers for zinc negative electrodes, utilizing their chemical inertness and density to isolate the electrolyte [86, 87]. As research deepens, researchers have begun to use the polar functional groups on its chain segments to design zinc negative electrode polymer based artificial interphase layers [88, 89]. By regulating the interface performance through polar functional groups, the synergistic effect of multiple mechanisms can evenly distribute the ion concentration on the electrode surface, leading to uniform nucleation; Guide the optimal growth of zinc ions [88, 89]. For example, Chen et al. [90] constructed a polyvinyl alcohol (PVA) protective layer on a zinc negative electrode using a simple scraping method. PVA molecular chains are rich in hydroxyl groups, which can effectively coordinate and guide Zn²⁺ (Figure 3a), reduce nucleation overpotential, and induce preferential deposition on the (002) crystal plane during Zn²⁺ deposition, forming a smooth deposition layer and inhibiting dendritic growth (Figure 3b). This experimental observation aligns with the facet‐selective adsorption mechanism discussed in Section 3: the abundant ‐OH groups in PVA preferentially bind to the Zn (002) plane, lowering its interfacial energy to steer lateral growth over vertical dendrite formation. The polyacrylonitrile (PAN) coating provides another approach to regulate the interface through functional group design [81]. The cyano (─C≡N) groups act as strong Lewis base sites, capable of strongly coordinating tightly with Zn²⁺. This interaction not only homogenizes interfacial cation distribution for uniform nucleation but also, due to its linear geometry, helps steer zinc deposition toward specific orientations (Figure 3c). At the same time, the strong interaction between cyano and Zn²⁺ enables it to competitively enter the primary solvation shell of Zn²⁺, partially replacing coordinating water molecules. This strategy embodies the mechanism of reconstructing the solvation shell and reducing interfacial water activity, which effectively inhibits the water‐involved HER and corrosion. Furthermore, the introduction of polar cyano groups optimizes the wettability of the coating surface (Figure 3d), synergizing with anions in the electrolyte to construct low‐resistance hydrophilic ion transport microchannels at the interface. The synergy of these mechanisms—guiding deposition, suppressing side reactions, and optimizing transport—significantly lowers interfacial resistance and enhances the reversibility of zinc plating/stripping (Figure 3e). To overcome the limitations of single polymer performance, Liu et al. [91] developed a PVDF‐SBA‐15 organic‐inorganic composite coating, illustrating the strategy of achieving synergy through material compositing. The PVDF‐SBA15 composite layer was fabricated via a spin‐coating process. This hybrid structure combines the mechanical robustness of inorganic SBA‐15 with the adhesive properties of the PVDF polymer matrix, effectively suppressing dendrite growth (Figure 3f). The inorganic filler also markedly enhances the mechanical strength of the coating, improving its resistance to deposition stress and cracking. Tests showed this composite coating reduced HER by approximately 82% (Figure 3g). Immersion experiments further demonstrated minimal corrosion and byproduct formation on coated zinc, proving the coating's efficacy in suppressing long‐term corrosion via substrate synergy.

FIGURE 3.

(a) Schematic illustrations of the Zn deposition process for PVA@Zn and bare Zn electrodes. (b) The peak intensity ratio of I (002)/I (100) and I (002)/I (101) for the corresponding electrodes. SEM images of (f) Zn and (g–k) PVA@Zn‐1 electrodes after 100 h [90]. Copyright 2022, Elsevier. (c) Schematic illustration of dendrite formation process on bare Zn and PANZ@Zn‐2 electrodes. (d) PAN@Zn of contact angles between different zinc anodes and electrolyte. (e) Electrochemical impedance spectra (EIS) of symmetric cells with bare Zn and PANZ@Zn anodes [81]. Copyright 2021, Wiley‐VCH. (f) Schematic diagrams of Zn deposition process on bare Zn and PVDF‐SBA15@Zn. (g) The volume of hydrogen evolution at different cycles [91]. Copyright 2022, Elsevier.

Although the coating method has significant advantages, its inherent drawbacks cannot be ignored. First, the protective layer constructed by the coating method has poor stability with the zinc metal substrate. During the long‐term operation of the battery, peeling and cracking of the protective layer may occur between the protective layer and the substrate; Second, achieving uniform thickness and pinhole‐free coating on large‐area industrial‐grade electrodes is a key manufacturing challenge to ensure consistent battery performance. Therefore, future research should not only focus on developing new polymers with stronger intrinsic interfacial affinity, but also on developing precisely controllable coating processes

4.1.2. In Situ Polymerization Polymer Based Artificial Interphase Layers

To overcome the weak adhesion and non‐uniform coverage possible with coated layers, the in situ polymerization strategy has been developed [77, 92, 93]. This approach involves introducing reactive monomers and initiators into the cell assembly, where polymerization is triggered directly on the zinc surface via electrochemical [94], chemical [78, 95], photochemical, or other means. This results in a protective layer grown from and tightly bound to the substrate.

The key advantage of in situ polymerization is the formation of strong covalent or coordination bonds with the zinc substrate, fulfilling the mechanism of robust interfacial bonding [96, 97]. For example, the polyaniline network electro‐polymerized on zinc exhibits excellent mechanical stability due to this direct bonding, while its intrinsic conductivity helps homogenize surface current distribution [98]. Furthermore, advanced in situ polymers can incorporate dynamic covalent bonds, creating networks with self‐healing capabilities. This embodies the mechanism of dynamic adaptation, allowing the interface to repair minor damage during cycling [99]. For example, Liu et al. [68] constructed a polyvinylidene fluoride (PVDF) based composite protective layer on the surface of a zinc negative electrode using electrochemical polymerization. The strategy of building robust and resilient interfaces through the formation of chemical bonds has been implemented. The protective layer constructed by electrochemical polymerization can be tightly bound to the zinc negative electrode substrate through covalent/coordination bonds, and has excellent stability, which can maintain stability after bending at 1000°C (Figure 4a,b). Concurrently, the hydrophobic nature of PVDF effectively isolates the electrolyte, suppressing side reactions (Figure 4c). Jing et al. [100] utilized electrochemical processes to precisely tailor a protective layer, creating an interface conducive to fine‐grained zinc nucleation on copper current collectors (Figure 4d). This work exemplifies the mechanism of nucleation site regulation. Density functional theory calculations confirmed that the modified interface provides a more favorable Gibbs free energy for deposition (Figure 4e,f), guiding more uniform zinc growth.

FIGURE 4.

(a) Schematic of the bending test SEM images of. (b) Pb‐PVDF@Zn and Pb@Zn after 100 bending times. (c) XRD contour plots of bare Zn, Pb@Zn, and PbPVDF@Zn after soaking in 2M ZnSO₄ aqueous electrolyte for different days [68]. Copyright 2024, Royal Society of Chemistry. (d) Preparation process of NC‐Cu@Ti electrode. (e) Ea and Zn adsorption configurations for Cu and Zn modeling. [2, 3] Copyright 2021, Wiley‐VCH. (f) Adsorption setup for Cu Ea and Zn with various particle sizes [100]. Copyright 2024, American Chemical Society.

In summary, in situ polymerization enables the construction of polymer based artificial interphase layers with strong adhesion and excellent conformity to the electrode surface. The cited cases demonstrate that this strategy can simultaneously achieve robust interfacial bonding for durability, incorporate functional components to suppress side reactions, and fine‐tune interfacial properties to optimize deposition kinetics, highlighting its strong potential for building high‐performance artificial interphases.

4.1.3. Self‐Assembled Monolayer Polymer Based Artificial Interphase Layers

The self‐assembled monolayers spontaneously and directionally arranges functional molecules on the surface of the zinc negative electrode to form a highly ordered ultra‐thin protective layer [79]. Mainly utilizing intermolecular forces and non‐covalent interactions or specific chemical adsorption behaviors with zinc substrate. Self‐assembling monolayer provide interface control with molecular‐level precision [101, 102].

The research has confirmed the effectiveness of this strategy. For instance, Mwemezi et al. [102] constructed a SAM on zinc using 11‐mercaptoundecanoic acid (HS(CH2)10COOH) molecules (Figure 5a). This design exemplifies the concept of molecular‐level precision in constructing an interface barrier. Its hydrophobic alkyl chain tail groups can effectively block water molecules, directly and ultimately achieving physical barrier to inhibit HER and corrosion (Figure 5b). At the same time, its ionizable carboxylate tail groups can adjust the charge state and hydrophilicity according to the interface pH (Figure 5c). This basic interface chemical regulation capability helps adapt to the changing interface microenvironment during electrochemical processes.

FIGURE 5.

(a) Schematic diagram describing the functions of MUDA SAMs for simultaneous suppression of side reactions and dendrite formation in AZIBs. (b) Nyquist plots of Zn || Zn and MUDA/Zn || Zn under AC application of OCV ± 10 mV. (c) Photo images of Zn || Zn and MUDA/Zn || Zn cells during galvanostatic P/S cycles in 1 M ZnSO₄ at pH  =  4.3 (1 mA cm⁻², 1 mAh cm⁻²). Photos were taken when an electrode on the left side was in a stripped state. In MUDA/Zn || Zn, MUDA/Zn was located on the left side [102]. Copyright 2022, Wiley‐VCH.

In summary, the coating method serves as a fast track to practical application, yet it requires addressing the issue of interface reliability. In contrast, the in situ polymerization method represents an advanced path for pursuing high performance and intelligence design, but it has a higher technological threshold. Meanwhile, the self‐assembly method provides a microscopic lens for exploring fundamental mechanisms and ultimate performance limits. Future interface designs may tend toward a hybrid strategy, such as introducing post‐treatment to induce local crosslinking on the basis of simple coating, in order to balance processing convenience with high interface performance. Table 4 summarizes the recent advances in polymer‐based artificial interphase layers for stable Zn anodes.

TABLE 4.

Summary of Polymer based artificial interphase layers for Stable Zn Anodes.

Sub‐type	Material	Key functional groups	Method	Thickness	Electrolyte	Cycle Life (sym.) [h] @ [mA cm−2, mAh cm−2]	Voltage Hysteresis [mV]	CPC [Ah cm−2]	Avg. CE [%]	Full Cell Performance	Refs.
Coating	PVA	‐OH	Blade coating	∼ 16.5 µm	2 M Zn(OTf)2	>5000 @ 0.25, 0.25	—	>5.0	>99	>1000 (MnO2) @ 1 A g−1	[90]
Coating	PANZ	‐C≡N, Zn2 +‐O	Drip coating	—	2 M Zn(OTf)2	>1140 @ 1, 1	∼75	>0.57	99.8	>1000 (Mn‐V2O5) @ 500 mA g−1	[81]
Hybrid coating	PVDF‐SBA15	‐CF2‐, hydrophobic, porous SiO2	Spin coating	—	3 M ZnSO4	>1650 @ 3, 0.6	∼38	>0.99		1000 (V2O5) @ 1 A g−1, 82.14%	[91]
Hybrid interface	Pb‐PVDF	Pb nanoparticles,—CF2	One step chemical displacement	0.5 µm	2 M ZnSO4	>8100 @ 1, 0.5		>8	99.94	5000 (VOH) @ 2 A g−1, 82.7%	[68]
SAM	MUDA	‐SH, ‐COOH, alkyl chain	Impregnation	∼1.25 nm	1 M ZnSO4 (pH 4.3)	>1000 @ 1, 1	∼22	>1	99.72	500 (δ‐MnO2) @ 500 mA −1, 188 mAh g−1	[102]
Coating	ZF‐PAN	‐C≡N, [Fe (CN)6] [6, 7, 8]−	Electrospinning	∼10 µm	2 M ZnSO4	>5500 @ 0.5, 0.5	83.2	>2.75	98.15	600 (MnO2) @ 2C, 66.0%	[103]
Coating	PEDOT	Conjugated π‐π bond	Electrochemical deposition	∼2µm	2 M ZnSO4	>5500 @ 0.5, 0.5	42.6	>27.3	98.9	600 (MnO2) @ 2C, 66.0%	[104]
Coating	nF2/PVDF (Zn‐SP)	‐CF2 −, ZnF2, Sn	Drip	∼2 µm	2 M ZnSO4	>1500 @ 2, 2	13	>3	99.8	1600 (CNT@MnO2) @ 1 A g−1, 98.6%	[105]

4.2. Polymer‐Based Electrolyte

Engineering the electrolyte by introducing polymers is a fundamental strategy to stabilize the ZMAs from the source of bulk transport environment and deposition interface [47, 102]. This strategy aims to optimize the solvation structure and transport pathway of Zn²⁺ while simultaneously widening the electrochemical stability window of the electrolyte [106, 107]. Research in this area has evolved from simple liquid‐phase additive strategies to the construction of complex quasi‐solid and solid systems [108].

4.2.1. Polymer Functional Additives in Liquid Electrolytes

Introducing a small amount of soluble polymer or monomer additives into the electrolyte of traditional aqueous zinc ion batteries can regulate the ion transport environment and deposition interface from the source [109]. The functional groups of these additives mainly function to regulate the solvation and deposition behavior of zinc ions, effectively suppressing side reactions while maintaining high ionic conductivity [110].

There are three main mechanisms for adding additives to the electrolyte: (1) Reconstruction of Zn²⁺ solvation sheath. Functional groups on the polymer chain with strong coordination ability with zinc ions can replace some water molecules and form a more stable structure [111]. (2) Interface control. The polymer can preferentially adsorb on the surface of ZMAs to form a molecular boundary facial mask. To achieve uniform distribution of ion currents on the surface [112]. (3) Adjusting the properties of electrolyte. Additives can regulate the viscosity of the electrolyte, improve ion migration and mass transfer [113]. For example, Chen et al. [114] introduced an ionic liquid additive that preferentially adsorbs cations on the zinc surface, modifies the local water structure, and uses anion‐derived electrostatic effects to regulate interfacial Zn²⁺ distribution. The synergy of these actions promotes uniform zinc deposition, as validated by phase‐field simulations (Figure 6a–c). In another approach, Cui et al. [115] used succinonitrile molecules in a highly concentrated electrolyte to reconstruct the Zn^{2 +} solvation sheath. The nitrile (–C≡N) groups modify the solvation environment, reducing water activity and minimizing its participation in side reactions (Figure 6d,e). This mechanism effectively suppresses​ battery failure across a wide temperature range, from 25°C to −90°C.

FIGURE 6.

(a) Schematic illustration of the evolution process during Zn deposition and SEI generation in these electrolytes. Dendrite morphology growth as a function of time based on (b) Zn(OTf)₂ and (c) Zn(OTf)₂ with [CellMim]⁺ electrolyte [114]. Copyright 2025, Royal Society of Chemistry. (d) 3D snapshot obtained by MD simulations and representative Zn²⁺‐solvation structure in the ZS electrolyte. (e) Schematic diagrams of Zn²⁺ solvation structure and corresponding interfacial reactions in ZW and ZS [115]. Copyright 2020, Elsevier.

The strategy of adding additives has the advantages of small process changes, simplicity, and wide applicability. However, additives may decompose (or: be degraded/consumed) during long‐term cycling, especially under high‐voltage operation, leading to their depletion. This degradation negatively impacts the overall stability of the battery. Therefore, additive strategies often need to be combined with other stabilization methods to ensure long‐term ZMA durability.

4.2.2. Gel Polymer Electrolytes

Gel polymer electrolytes (GPEs) are quasi‐solid systems that have attracted significant research interest due to their high ionic conductivity, good electrode‐electrolyte interfacial contact, robust mechanical strength, and enhanced safety [116].

The protective effect of gel polymer electrolytes (GPEs) stems from their unique solid‐liquid composite phase state: GPEs physically immobilize a large amount of free water through a polymer network. Essentially extending the chemical water locking mechanism from the molecular scale to the macroscopic phase state [117]. For instance, n the Ni²⁺/Zn²⁺ bimetallic cation GPE developed by Liu et al. [118] the introduced Ni²⁺ generates an electrostatic shielding effect. This not only regulates ion flux and deposition kinetics (Figure 7a) to homogenize interfacial ion flow and guide Zn deposition onto the (002) plane, but also enables excellent low‐temperature performance at −20°C (Figure 7b). In a different design, Pei et al. [119] created a repulsive volume effect by introducing a crowding agent, forcing polymer chains to form highly ordered ion channels. This precisely interprets the mechanism of designing selective ion transport channels, not only allowing the electrolyte to maintain a conductivity of 0.36 mS cm⁻¹ at −60°C, but also achieving a wide electrochemical window of >2.5 V (Figure 7c–e). These studies confirmed that the gel electrolyte can simultaneously achieve ion transport, interface stability and mechanical strength.

FIGURE 7.

(a) Rate performances of Zn //Zn symmetrical cells at different current densities at −20°C. (b) Cycling performance of the symmetrical cells at −20°C under 10 mA cm⁻², 5 mAh cm⁻² [118]. Copyright 2024, Wiley‐VCH. (c) Differential scanning calorimetric thermograms of electrolytes recorded at 5°C min⁻¹. (d) Radial distribution functions and corresponding coordination plots of Zn²⁺ in CZHE at −60°C. (e) Comparison of Zn²⁺ solvation structures in CZHE and LE at −60°C [119]. Copyright 2025, Springer Nature.

Current challenges for GPEs include maintaining their structural integrity against long‐term electrode volume changes and preventing the evaporation or decomposition of the contained solvent.

4.2.3. Quasi‐Solid and Solid Polymer Electrolytes

Quasi–solid and solid polymer electrolytes are committed to reducing or even completely eliminating liquid components in pursuit of ultimate stability and safety in batteries [120]. The core of is to construct a solid‐state ion conduction system, which allows ions to be mainly transported through the movement of polymer segments or artificially designed restricted channels, thereby avoiding the inherent leakage, volatilization, and severe side reactions of liquid electrolytes [121].

The functional implementation of QSSPEs/SPEs is usually based on synergistic mechanisms such as salt precipitation effect and deep‐water locking, which jointly create an environment with extremely low solvent activity and limited ion migration [43]. The use of ultra‐high concentrations of zinc salts can trigger strong salt precipitation effects and strong interactions between zinc ions and polar groups. This will cause dehydration and densification of the polymer network, binding residual moisture or high boiling point solvents in a tightly bound state, thereby rendering it electrochemically inactive [122]. Ion transport in such systems then relies on the segmental motion of polymer chains or on specially engineered fast‐ion‐conduction pathways, such as those created by incorporating inorganic fillers or constructing ordered nanochannels [123].

For example, Hu et al. [124] incorporated high‐concentration zinc acetate into a polymer network using urea as a solubilizer. The strong salting‐out effect from the acetate ions was crucial for achieving high mechanical strength (557% stretchability, 3.7 MPa compressive strength) and excellent fatigue resistance (Figure 8a,b), resulting in a system that balances a modified transport environment with superior mechanical integrity (Figure 8c). A common shortcoming of such systems is relatively low ionic conductivity. Critically, this electrolyte system also delivers exceptional HER suppression performance. The high zinc acetate concentration induces a pronounced salting‐out effect, which drastically reduces the activity of free water molecules available for the hydrogen evolution reaction (HER). Simultaneously, acetate anions competitively coordinate with Zn²⁺, displacing water molecules from the primary solvation sheath and disrupting the hydrolysis equilibrium of hydrated zinc ions a dominant proton source for HER as discussed in Section 2.2. Urea further immobilizes residual free water via strong hydrogen bonding, while the acetate/acetic acid buffer pair mitigates local interfacial alkalization during cycling, preventing the negative shift of the HER equilibrium potential that would otherwise accelerate side reactions. The synergy of these effects enables the electrolyte to maintain high ionic conductivity while effectively suppressing HER, contributing to the long‐term cycling stability of the Zn anode. To address this, Zhang et al. [125]. innovatively introduced single‐walled carbon nanotubes (SWCNTs) into a quasi‐solid electrolyte. Theoretical simulations and experiments demonstrated that rapid ion transport channels could form on the SWCNT surface (Figure 8d). This strategy of using conductive fillers as ion highways successfully enhanced conductivity without compromising the solid‐state character of the electrolyte (Figure 8e–g).

FIGURE 8.

(a,b) Digital photos of compressive strength tests. (c) Schemes showing the mechanical durability of USPH‐5 [124]. Copyright 2025, Wiley‐VCH. (d) Schematic illustration of (A) fast ion transport through SWcNt channels in cPAM. (e) ionic conductivity of various hydrogels, with eight trials conducted for each type (f) Temperature and (g) Water content dependence of ionic conductivity of CPAM and PAM [125]. Copyright 2025, American Association for the Advancement of Science.

The change of polymer electrolyte from additive to gelled state and then to quasi solid state reflects the continuous exploration of improvement methods for AZIBs (Table 5). GPEs represent one of the most promising solid electrolyte strategies in terms of performance and practicability for practical applications. For AZIBs, the future goal lies in further developing such GPEs (or: this category of electrolytes) to achieve simultaneously high ionic conductivity and a wide electrochemical window.

TABLE 5.

Summary of polymer‐based electrolytes and additives for stable Zn anodes.

Type	Material/System	Key Functional Groups/Composition	Preparation/Formulation	Key Parameter	α [mS cm−1]/t(Zn2+)	Cycle Life (sym.) [h] @ [mA cm−2, mAh cm− 2]	Avg. CE [%]	Full Cell Performance	Refs.
Additive	[CellMim]	Imidazole cation, cellulose skeleton,—OH	Esterification synthesis, direct addition	1 g L−1	—	>1800 @ 1, 1	—	500 (NVO) @ 1 A g−1, 83.6%	[114]
Eutectic electrolyte	ZS	‐C≡N, H2O, [Zn (H2O)4(SN)2]2+	Heating and mixing	Zn (ClO4)2·6 H2O: SN = 1:8	5.52/—	>2000 @ 0.2, 2	98.4	—	[115]
Gel electrolyte	Ni/Zn‐GPE	‐CONH2, ‐COO−, Ni2+	One‐step thermal polymerization	Ni2+ concentration 0.05 M	28.70 @ −20°C/0.465	>2700 @ 5, 1 (RT)	99.4	1000 (V2O5) @ 1 A g−1, 75.6% (RT)	[118]
Gel electrolyte	CZHE	Zwitterionic groups, maltose, ‐OH	Soak after synthesis	Maltose 40wt%	33.1/0.67	>1200 @ 1, 1	99.6	1000 (PANI) @ 3 A g−1, 85%	[119]
Gel electrolyte	USPH‐5	‐CONH2, CH COO−, urea	Thermal polymerization	Zn (Ac)2 5 molal	8.07/—	>1000 @ 0.5, 0.5	99.93	1000 (NVO) @ 1 A g−1, 79.51%	[124]
Gel electrolyte	CPAM	‐CONH2, single‐walled carbon nanotubes	Photoinduced in situ polymerization	SWCNT 0.02 mg mL−1	30.3/—	>7030 @ 1, 1	99	2000 (ZVO) @ 40 A g−1, 80%	[125]

4.3. Polymer‐Modified Separators

In AZIBs, the separator functions as a physical barrier to prevent electrical short circuits while permitting selective ion transport [126]. Commonly used commercial separators, such as glass fiber (GF) and polypropylene (PP) membranes, primarily provide basic isolation [71]. Modifying these separators with polymers is a cost‐effective and relatively simple strategy to enhance their functionality, enabling active regulation of ion transport and optimization of the electrode‐electrolyte interface [127] (Table 6). The main modification approaches are surface modification​ and composite fabrication:

TABLE 6.

Summary of the performance and properties of commonly used separators in water‐based Zinc Ion Batteries.

Separator type	Typical material	Thickness (µm)	Porosity (%)	Mechanical strength (tensile strength/modulus)	effect
Fiberglass diaphragm	GF	>300	71.55–91.8		The electrolyte has excellent wettability and fast liquid absorption; But the pore size distribution is uneven
Cellulose based membrane	BNF	∼8	>50	89.53 MPa	The migration number of Zn2+ is as high as 0.7; Guide the deposition of Zn (002) texture.
	Cotton based cellulose film	—	—	29.2 MPa, 4.16GPa	Can withstand large‐area capacity deposition of 20 mAh cm2
	SBCN	∼8		207 MPa	High transparency (∼90%), ultra long cycle stability (>5200 h)
Polyolefin membrane	PP/PE	∼16–25
Modified/Functional Diaphragm	Grafted modified polyolefin (such as PP‐g‐AA)	∼25			Introducing hydrophilic water (‐ COOH) reduces contact angle and improves wettability; Partial hydrophobic domains block water and inhibit HER.
	Composite coating/functional layer (such as MOF@ GF, PGZ)	10–30			High Zn2+ migration number (0.80–0.86), homogenization of ion flow, suppression of dendrites and side reactions.
	Electro‐spun nanofiber membrane (such as PAN/PI, PAN)	∼63	83.9	24.65 MPa	The uniform pore structure and interwoven fiber network are conducive to guiding the uniform transport of ions.
	Aramid/cellulose composite film (AC film)	—		303 MPa	As an interlayer, the wet strength remains at 92.7 MPa and the contact angle is 54°

4.3.1. Surface‐Modified Separators

The surface modification strategy centers on the direct performance enhancement of conventional glass fiber separators through the application of engineered polymer coatings, which impart critical properties including excellent interfacial stability, effective dendrite suppression, and long‐term cycling durability [128].

According to the polymer chemical properties of commercial membrane coatings, there are several mechanisms of action: ion selective transport layer: (1) Ion‐Selective Transport Layer:​ Polymers with specific charged or zwitterionic groups can be selected to create membranes that preferentially transport Zn^{2 +} over other ions (e.g., SO₄ ²⁻), increasing the Zn²⁺ transference number [63]; (2) Hydrophilicity/Chemical Regulation Layer:​ Coatings with tuned hydrophilicity/hydrophobicity can regulate water activity at the interface and influence interfacial electrochemical stability [129]; (3) Mechanical Reinforcement Layer:​ High‐modulus polymer coatings (e.g., aramid) can enhance the overall puncture strength of the separator, providing a robust physical barrier against dendrite penetration. For example, Zhang et al. [130] spin‐coated a composite layer of sulfonated cellulose and graphene on a separator. The negatively charged sulfonate (–SO₃ ⁻) groups preferentially adsorb and conduct Zn^{2 +} while repelling anions like SO₄ ²⁻. This ion‐selective transport guides Zn deposition with a preferred (002) crystallographic orientation, significantly improving deposition uniformity and reversibility (Figure 9a,b). Kim et al. [131] demonstrated a multifunctional improvement via a single treatment (Figure 9c). They coated a glass fiber separator surface with PVDF and introduced oxygen‐containing polar groups using atmospheric pressure plasma treatment (Figure 9d). This combined strategy enhanced both the mechanical robustness of the separator and its interfacial ion transport properties.

FIGURE 9.

(a) Synthesis of sulfonic cellulose by grafting sulfonic acid groups on the cellulose backbone. (b) The ion‐sieving function of sulfonic cellulose on the Janus separator surface. Energy profiles of SO₄ ^2‐  and H⁺ adsorption on the sulfonic cellulose under zeta potential [130]. Copyright 2022, Wiley‐VCH. (c) Schematic representations of structural and electrochemical improvements in bare GF and FP@GF. (d) Schematic illustration of oxygen‐based functional group incorporation into the PVDF matrix [131]. Copyright 2025, Elsevier.

The surface modification strategy offers advantages of good compatibility, wide applicability, and operational simplicity. A key limitation, however, is the potentially insufficient long‐term adhesion between the coating and the separator substrate, which may lead to delamination.

4.3.2. Polymer Composite Separators

Polymer composite membrane refers to the construction of an integrated membrane with novel structure and functional characteristics by combining two or more polymer materials with commercial membranes [132].

The structure and function of these composite membranes can be precisely designed to concurrently achieve high mechanical strength, fast and selective ion transport, and interfacial stability. For instance, Wang et al. [133] fabricated a separator with gradient wettability by compositing hydrophilic cellulose and hydrophobic aramid nanofiber. Functional groups on this composite separator coordinate strongly with Zn²⁺, optimizing the de‐solvation process at the interface (Figure 10a). Moreover, the separator demonstrated a high HER overpotential (−1.78 V), indicating effective suppression of water decomposition. In another study, Wu et al. [71] prepared a β‐PVDF/glass fiber composite separator via thermally induced phase separation. The high polarity of the β‐PVDF phase yielded a high Zn²⁺ transference number (t(Zn²⁺) ≈ 0.80) and a high Young's modulus, synergistically inhibiting dendrite penetration (Figure 10d–f).

FIGURE 10.

(a) The schematic diagram for the performance‐improvement mechanism of the ANF/MFC separator. (b) Binding energy of ANF‐Zn, MFC‐Zn, MFC–H₂O, and ANF‐H₂O. (c) The energy barrier ΔE of the de‐solvation of Zn²⁺ in GF and ANF/MFC separators [133]. Copyright 2025, Elsevier (d) Comparison of the calculated Zn²⁺ ion transference numbers and Zn²⁺ ion conductance of different separators. (e) Stress‐strain curves of the GF and PGZ separators at dry and wetted states. (f) Digital images of GF and PGZ separators suspended with 300 g weight [71]. Copyright 2025, Wiley‐VCH.

The polymer‐modified separator strategy successfully transforms passively isolated components into multifunction components capable of actively participating in the electrochemical process of batteries through two paths: surface engineering or intrinsic reconstruction (Table 7). Surface‐modified separators focus more on process flexibility and immediate application potential, suitable for rapid functional optimization of existing systems, and represent a practical path of adding to the good. Polymer composite separators, on the other hand, aim to achieve breakthroughs in intrinsic performance and multifunctional integration, providing a material foundation for the development of next‐generation high‐performance separators, and represent a future‐oriented innovative path.

TABLE 7.

Summary of polymer‐modified separators for stable Zn Anodes.

Base	Modification/Strategy	Method	Key Groups	σ [mS cm−1]/t(Zn2+)	Cycle Life (sym.) [h] @ [mA cm−2, mAh cm−2]	Avg. CE [%]	Full Cell Performance	Refs.
GF	Sulfonated cellulose/graphene (Janus)	Spin coating	‐SO3	23.9/0.826	>1400 @ 10, 10	99.2%	1900 (CNT‐MnO2) @ 1 A g−1, 95%	[130]
GF	Plasma treatment of PVDF coating(FP@GF)	Vacuum filtration + plasma treatment	‐OH, ‐COOH	67.43/0.49	>500 @ 2, 1	99.98%	150 (MnO2) @ 1.0 C, ∼98%	[131]
Cellulose	Aramid nanofibers/microfiber cellulose (ANF/MFC)	Vacuum filtration + freeze‐drying	─OH, ─C═O	31.96/—	>3800 @ 1, 1	99.6%	2000 (V2O5) @ 1 A g−1, ∼90%	[133]
Polymer membrane	β‐ PVDF/GF powder/Zn(OTf)2 (PGZ)	Solution casting + hot annealing	High polarity β—PVD	1145.50 mS/0.80	3500 @ 0.5, 0.5	99.9	23 000 (I2) @ 5C, 76.4%	[71]

4.4. Polymer‐Based 3D Current Collectors

Three‐dimensional (3D) porous current collectors (e.g., carbon cloth, metal foam, graphene sponge) effectively reduce local current density, provide ample space for zinc deposition, and buffer volume changes via their interconnected pores, representing a classic physical strategy to suppress dendrites [134]. However, traditional 3D frameworks are often inert, offering only physical support. Integrating polymers into these structures can impart critical electrochemical functionalities. Based on their primary role, polymers enable three key design strategies for functionalizing 3D current collectors [11].

4.4.1. Polymer As a Zincophilic Nucleation‐Guiding Layer

Coating polymers rich in specific functional groups on the surface of a 3D skeleton can create an environment with uniformly distributed zinc affinity sites, which has the following advantages: 1) Reducing the nucleation overpotential of zinc through coordination and inducing uniform nucleation [135]; (2) Guide subsequent zinc atoms to preferentially grow along the thermodynamically stable (002) crystal plane and suppress dendrites at the atomic scale [136]; (3) Improve the electrolyte wettability on the electrode​ surface to ensure ion transport efficiency. [137]

Modifying a layer of polydopamine on the surface of carbon cloth fibers is an effective strategy [138]. Modifying a layer of polydopamine on the surface of carbon cloth fibers is an effective strategy. More importantly, it strongly induces the (002) crystal plane orientation deposition of zinc, thus achieving dense, dendrite‐free zinc deposition within a 3D framework, endowing the symmetric battery with exceptional cycle stability (Figure 11a–c). Liu et al. [103] constructed a dual‐functional hydrophobic layer on zinc foil via electrospinning, comprising hydrophobic polyacrylonitrile (PAN) and zinc hexacyanoferrate (ZFHCF) (Figure 11d). The PAN matrix blocks water penetration to inhibit HER and corrosion, while the ZFHCF framework provides abundant nucleation sites and ion channels to guide uniform deposition. This synergistic design addresses both dendrite growth and side reactions, enabling a symmetric cell cycle life exceeding 5500 h (Figure 11e).

FIGURE 11.

(a) Nucleation overpotential of bare Zn and Zn@PDA asymmetrical cell (vs Cu electrode). (b) Images of contact angles between distilled water and Zn@PDA anodes. (c) Partial schematic illustration of PDA coating preventing H₂O molecules from conducting Zn²⁺ [138]. Copyright 2022, Wiley‐VCH. (d) Schematic illustration of zinc deposition on the surfaces of bare Zn, PAN@Zn, and ZF‐PAN@Zn electrodes. (e) Cycling performance of Zn||Zn, PAN@Zn||PAN@Zn, and ZF‐PAN@Zn||ZF‐PAN@Zn cells at 0.5 mA·cm⁻² with capacity of 0.5 mAh·cm⁻² [103]. Copyright 2025, Elsevier.

The strength of this strategy is its ability to fundamentally improve the initial zinc nucleation behavior. Its limitations include potential challenges in ensuring the long‐term electrochemical stability of the functional groups and achieving a uniform coating throughout the intricate depths of a complex 3D scaffold. Future development should focus on intelligent coatings with dynamic responsiveness to adapt to changes during cycling.

4.4.2. Polymer as a 3D Conductive Network

This strategy leverages a synergistic mechanism: constructing an additional 3D conductive network to homogenize current density while using nanostructures for physical confinement of zinc deposition [139]. Intrinsically conductive polymers (e.g., poly‐pyrrole, polyaniline, PEDOT:PSS) are used to build a secondary conductive network on an insulating skeleton or to form an ion‐electron bi‐continuous pathway with ion‐conductive gels [140]. This structure helps balance the electric field distribution at the interface in real time and confines zinc deposition within predefined nanoscale zones via a physical confinement effect [141].

The carbonized poly‐pyrrole nanowire‐modified carbon fiber studied by Chen et al. [142] demonstrated this with carbonized poly‐pyrrole (PPy) nanowires grown on etched carbon fibers. Poly‐pyrrole nanowires were grown on etched carbon fibers through electrochemical in situ polymerization and further carbonized to construct a hierarchical conductive network (Figure 12a). This network not only provides additional electronic conduction paths, but its nanowire structure also subdivides the gaps between carbon fibers into nanoscale microreactors, achieving fine physical confinement of zinc deposition (Figure 12b). Even at high current densities, zinc is restricted to grow within the microzones constructed by PPy nanowires, thus maintaining a dendrite‐free deposition morphology. Wang et al. [104] showed that a PEDOT layer electrodeposited on zinc creates self‐constructed electric field channels via its conjugated π‐π bonds. During plating, these channels attract Zn²⁺ via Coulombic attraction, promoting uniform transport and deposition. During stripping, they repel electrons from Zn atoms, accelerating the process (Figure 12c). This electric‐field sponge effect enhances reaction kinetics (Figure 12d,e), enabling a Zn@PEDOT symmetric cell to cycle stably for >5250 h at 1 mA cm⁻² and tolerate ultra‐high current densities up to 80 mA cm⁻².

FIGURE 12.

(a) Schematic diagram of a 2D fabric battery (b) The CPPy@ECFs at different magnifications [142]. Copyright 2023, Elsevier. (c) The electric‐field sponge effect regulated Zn plating/stripping process on the PEDOT‐coated Zn  (d,e) Density distribution of Zn²⁺ in bare Zn system and Zn@PEDOT system [104]. Copyright 2024, Wiley‐VCH.

While this strategy effectively optimizes current distribution and ion transport, a key limitation is the potential degradation in the structural stability and conductivity of the conductive polymers themselves during long‐term electrochemical cycling.

4.4.3. Construction of an Artificial Solid Electrolyte Interface (ASEI)

Inspired by the solid electrolyte interphase (SEI) in lithium batteries, a dense and stable artificial SEI (ASEI) can be constructed on current collectors to facilitate rapid Zn²⁺ shuttling while isolating water [143]. Organic and inorganic hybrid designs are commonly used: by using inorganic components such as ZnF₂, ZnN₃(PO₄)₂, and fast ion conductors to enhance the migration rate of zinc ions [144], and by utilizing polymers such as PVDF and polyimide to provide flexibility, an environment with high ion migration rate and stability is constructed [145].

For example, a ZnF₂/PVDF composite layer functions as an effective ASEI. The inorganic ZnF₂ component provides fast transport channels for Zn²⁺ [105]. While the PVDF polymer binder ensures mechanical adhesion and flexibility between the coating and the 3D current collector. This composite layer isolates the zinc from both water molecules and electrons, effectively suppressing side reactions (Figure 13a–c).

FIGURE 13.

(a) Density functional theory calculations of the free H₂O adsorption process on metallic Zn and ZnF₂. Simulated electric field distributions and the corresponding schematic diagrams of Zn²⁺ ions deposition processes on (b) bare Zn and (c) Zn‐SP [105]. Copyright 2022, Elsevier.

Although this strategy isolates side reactions from the source and provides a stable interface, its long‐term cycling stability remains a limitation [146]. Thus, developing composite interfaces with high ionic conductivity and excellent mechanical properties is a crucial direction to address this issue [147].

The three roles of polymers in 3D current collectors clearly present the design logic evolution from chemical modification to physical composite and interface engineering. The zincophilic nucleation guiding layer solves the problem of where to start growing, which is the foundation of functionalization [148]. The 3D conductive network solves the problem of how to uniformly distribute current and ions, strengthening process control [149]. The artificial SEI layer solves the problem of under what environment to grow, pursuing the intrinsic stability of the interface.

These three functions are not mutually exclusive, and the future development direction is to develop intelligent fluid collection systems that are multifunctional, integrated, and capable of adaptive response [150]. The ideal system can integrate the interface characteristics of zinc friendly coatings, conductive networks, and artificial solid electrolytes [151]. Through this integrated design, the entire process of zinc deposition nucleation, growth, and even interface environment can be finely controlled from multiple dimensions, laying the foundation for the next generation of high‐performance zinc battery negative electrodes [152].

4.5. Integrated and Multiscale Design Strategies

While Chapters 4.1–4.4 highlight the merits of individual strategies, their standalone implementation often entails inherent trade‐offs, for instance, thick interphases increase impedance, whereas soft gels lack dendrite‐blocking rigidity. The next evolutionary step lies in cross‐component collaboration, where polymer interface layers, gel electrolytes, functional separators, and 3D hosts are chemically/physically interlocked to encode mechanical, interfacial, and redox functionalities into a single architecture.

Three synergistic paradigms merit emphasis. (i) Interphase and gel hybridization: A dense polymer coating homogenizes Zn²⁺ flux, while the gel matrix confines volume expansion and deactivates free water. Representative examples include the PAM‐DMF hydrogel affording 650 h at 30 mA cm⁻²/ 15 mAh cm⁻² and 68% Zn utilization [153], and the PVA/Bmim[ZnBr] supramolecular IL gel that leverages Br‐H/H‐bond networks for stress dissipation (>2000 h) while stabilizing four‐electron iodine via [IBr₂]⁻ [8]. (ii) Janus polymer interfaces: Asymmetric functionality decouples anode‐side (hydrophobic, Zn²⁺‐affinity) and cathode‐side (hydrophilic, proton‐permeable) requirements, as exemplified by DICP's Janus hydrogel membrane enabling 48 mAh in 22.5 cm² pouch cells [154]. (iii) 3D scaffold + gel infusion: Infiltrating viscoelastic gels into porous Zn frameworks (e.g., 3D‐Zn@ZnSe, In@PAM) accommodates >300% volumetric strain under high areal capacities (>10 mAh cm⁻²) while avoiding delamination endemic to rigid coatings.

Moving forward, integrated design must prioritize chemical bonding or physical interlocking​ among components, rather than mere stacking to deliver the trifecta of ionic conductivity, mechanical toughness, and electrochemical stability demanded by practical AZIBs.

5. Summary and Outlook

5.1. Summary

Facing the severe challenges posed by multiple coupled failures in AZIBs, such as dendritic growth, HER corrosion, and interfacial corrosion/passivation of ZMAs, this review systematically review the systematic solutions provided by polymer materials, leveraging their customizable molecular design and multifunctional integration potential [155]. This article proposes and elaborates for the first time the core framework of multifunctional integrated design of polymers. The fundamental logic lies in the rational design of polymers across multiple scales, from molecular structure to aggregated state [156], which integrates various functions such as guiding ion transport, suppressing side reactions, buffering mechanical stress, and optimizing the transport environment, synergistically into different components of the battery (interface, electrolyte, separator, current collector) [157], thereby breaking the vicious cycle of failure modes [158].

This article first deeply analyzes the coupling relationship between the four major failure modes of ZMAs (dendrite, HER, corrosion, and passivation), which trigger each other and amplify gradually [24]. It clarifies that any effective strategy must be systematic. Then, the stabilization mechanism of polymers is summarized into four interrelated design principles: regulating ion flux and deposition kinetics [159], constructing physicochemical barriers [160], providing mechanical flexibility and adaptive interfaces [161], and optimizing bulk ion transport environment [162]. Based on this, the article systematically reviews the latest progress of the four major polymer strategies:

1. Polymer based artificial interphase layers (coating, in situ polymerization, self‐assembly) serve as barriers directly modifying the electrode surface, achieving an evolution from passive barrier to active chemical regulation [20].

2. Polymer‐based electrolytes (functional additives, gel, quasi‐solid state) originate from the bulk transport environment and achieve gradient control over the activity and state of “water” by reconstructing the solvation sheath and constructing a confined network [60, 163].

3. Polymer‐modified membranes transform inert isolation components into “smart components” with ion selectivity and interface regulation capabilities, indirectly but effectively creating a favorable deposition environment [164, 165].

4. Polymer‐based 3D current collectors upgrade traditional physical hosts into “functionalized electrodes” that integrate chemical guidance, conductive networks, and artificial SEI, achieving precise control over the entire zinc deposition process [166, 167].

In summary, the success of various strategies all stems from the practice of the principle of multifunctional integrated design of polymers [168]. This article not only reviews the progress but also aims to provide a unified design framework, laying a solid theoretical for the development of high‐performance and long‐lasting AZIBs based on polymer molecular engineering [62, 169].

5.2. Outlook

In order to overcome existing limitations, push this field from the laboratory to practical applications, and develop toward higher performance dimensions, the following forward‐looking directions are worth exploring in depth:

1. Development of intelligent responsive polymer interfaces: Design and synthesis of “intelligent” polymer interfaces capable of dynamic and reversible responses to changes in external electrochemical environments, such as local pH, mechanical stress, potential, and ion concentration. For example, pH‐responsive gels can contract or change their hydrophilicity/hydrophobicity when the interface becomes alkaline, which more effectively blocks the transport of OH⁻ and stabilizes the interface [170]. Stress‐responsive coatings can harden in situ upon sensing the micro‐stress from dendrite compression, thereby actively inhibiting dendrite penetration [171]. Meanwhile, redox‐responsive (or potential‐responsive) molecules can switch their conformation or conductivity within the different potential windows of zinc deposition and dissolution, dynamically optimizing ion transport pathways and interface stability [172]. Such adaptive interfaces represent a paradigm shift from static protection to dynamic intelligent management.

2. Wide‐window polymer electrolyte system matching high‐voltage cathodes: Current research primarily focuses on protecting ZMAs. To match high‐voltage materials such as MnO₂, V₂O₅, and organic cathodes, there is an urgent need to develop polymer electrolytes that remain stable across a wide electrochemical stability window (> 2.0 V vs. Zn²⁺/Zn, even up to 2.5 V) [173, 174]. This requires starting from molecular design, synthesizing novel polymer matrices with high oxidation resistance (such as highly fluorinated polymers [175, 176], poly‐ionic liquids with specific structures), and collaboratively designing anion capture or molecular crowding electrolytes [177]. Simultaneously, it achieves stable protection of the highly active zinc anode and compatibility with high‐voltage cathodes, thereby significantly enhancing the energy density of the full battery [178].

3. Multi‐scale computational simulation and artificial intelligence‐assisted design: Overcoming the limitations of the current “trial and error” research and development model. Utilizing first‐principles calculations, molecular dynamics simulations, and machine learning, this article reveals the interaction mechanisms between polymer functional groups and Zn²⁺, H₂O, and electrolyte components at the atomic/molecular scale [179, 180]. This facilitates prediction of the structure‐property relationships of polymer structures and their ionic conductivity, mechanical properties, and electrochemical stability [181, 182]. The utilization of artificial intelligence algorithms facilitates the execution of, high‐throughput screening procedures, encompassing potential polymer monomers, topological structures, and composite material formulations, accelerating the discovery and design process of high‐performance, customized polymer materials [183].

4. While significant progress has been made in prolonging cycling life at low areal capacities (1–2 mAh cm⁻²), the transition to practical high‐areal‐capacity systems (>10 mAh cm⁻²) imposes severe challenges on the mechanical integrity of polymer interphases. The substantial volume expansion (∼300%) of zinc during deep galvanization can induce cracking or delamination of rigid polymer coatings [46, 184, 185]. Future research must shift focus from merely increasing Young's modulus to enhancing toughness and interfacial adhesion. Strategies such as incorporating dynamic covalent bonds​ for self‐healing capabilities, or utilizing porous polymer scaffolds​ to accommodate volume fluctuations, represent promising avenues. Moreover, establishing standardized testing protocols at high areal capacities is imperative to bridge the gap between academic research and industrial application [65, 186].

Polymer interface engineering is propelling the research on AZIBs toward a new stage characterized by multi‐dimensional synergy and intelligent precision [9, 187, 188] In the future, through in‐depth mechanistic exploration of stringent standards, innovation in intelligent materials, adoption of sustainable concepts, and close industry‐academia‐research collaboration, polymer materials are poised to play a pivotal/crucial​ role in advancing aqueous zinc‐ion batteries (AZIBs) [188, 189].

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.