Stress‐Lensed Electrochemical Sintering Enables Fast and Stable Lithium‐Silicon Alloy Chemistry in All‐Solid‐State Batteries

ABSTRACT

The fundamental challenge in all‐solid‐state batteries (ASSBs) lies in regulating the dynamic reconstruction of solid‐solid interfaces under electro‐chemo‐mechanical conditions. Currently, no mechanism exists to reconcile the conflicting requirements of structural stability and rapid ion transport for high‐capacity silicon (Si) anodes: expansion‐accommodated encapsulation strategies preserve integrity but block interparticle ionic contact, while intrinsic electrochemical sintering restores conduction but creates excessive agglomeration that fractures the electrode. Here, we propose a stress‐lensed electrochemical sintering (SLES) strategy to guide selective interfacial bonding by depositing Si conformally into a porous carbon host, specifically utilizing its high‐curvature pore entrances as geometric constrictions. During cycling, these constrictions act as “stress lenses”, concentrating the volumetric expansion stress of Si precisely at interparticle contacts. This focused mechanical energy locally lowers the atomic diffusion barrier, guiding the formation of a robust, percolating Si network while preserving internal voids to buffer volume changes. The resulting Si‐SLES anode resolves the stability‐transport conflict, achieving ∼100% capacity retention after 100 cycles with superior rate capability and demonstrating practical viability in full cells over 700 cycles.

We propose a SLES strategy, where the lithiation stress of Si deposited at high‐curvature pore entrances of the porous carbon host is concentrated, to guide selective electrochemical sintering. These geometric constrictions act as stress lenses, directing the formation of a percolating Si network, resolving the stability‐transport conflict, and achieving ∼100% capacity retention over 100 cycles in ASSBs.

1. Introduction

The advancement of electrochemical energy storage fundamentally relies on managing complex material transformations in confined spaces [1, 2, 3]. This challenge is especially critical for all‐solid‐state batteries (ASSBs), which promise exceptional safety and energy density but are constrained by a core interfacial issue: the inherent incompatibility between static electrode architectures and dynamic electro‐chemo‐mechanical processes occurring during operation [4, 5]. Due to the absence of liquid electrolyte wetting, the inherently poor adhesion and point‐to‐point contact at solid‐solid interfaces are catastrophically challenged by the dynamic volumetric changes inherent to high‐capacity electrode materials [6, 7, 8]. Silicon (Si) is regarded as a promising anode material for ASSBs due to its high specific capacity, but it epitomizes the extreme case of dynamic interfacial failure. It's phenomenal lithium storage capability is negated by catastrophic volumetric swings (>300%) that pulverize particles cut off solid‐solid interfaces and ionic pathways [9, 10, 11, 12]. The mechanical structural collapse and kinetic hysteresis collectively form a critical bottleneck for ASSB development.

In the context of dynamic structural evolution, electrochemical sintering emerges as a critical, double‐edged phenomenon for Si anodes. During alloying/dealloying cycles, repeated breaking and reformation of Si─Si bonds can fuse adjacent particles, inherently increasing interfacial contact area [9, 11, 13, 14, 15]. If without control, the formation of large agglomerates would intensify strain and accelerate structural failure, surpassing the ion transport in the bulk phase (over electrochemical sintering, fourth quadrant of Figure 1) [11, 16, 17]. Prevailing designs attempt to manage this dynamic with static constraints, which fall into two insufficient categories: delayed over electrochemical sintering (e.g., carbon coatings) or fully suppressing it through rigid physical isolation. Delayed sintering cannot withstand the stresses of Si expansion and only postpones the inevitable collapse. Additionally, the poor kinetics of the involved carbon in the sintering bulk impede lithium‐ion (Li⁺) transport (third quadrant of Figure 1) [18, 19, 20]. While the non‐electrochemical sintering achieved by combining low‐expansion structure and tough surface coating constructs an isolated structure, severely compromising ionic transport (second quadrant of Figure 1) [21, 22, 23]. This highlights that a static electrode design cannot effectively manage the natural dynamic changes in high‐capacity materials. What is needed is a strategy that actively steers and utilizes this dynamic evolution, thereby achieving simultaneous mechanical stability and fast kinetics.

FIGURE 1.

Design paradigms for Si anodes in ASSBs: from static confinement to dynamic guidance. (I) “Stress‐lensed” selective electrochemical sintering: The pore entrance of PC acts as the stress lens, magnifying the lithiation stress to induce interparticle sintering along PC, guaranteeing a mechanically reliable and low‐resistance ionic highway. (II) Non‐electrochemical sintering: The buffered expansion effectively preserves the integrity of the carbon layer, but the poor ionic conductivity of the carbon results in sluggish kinetics and stress heterogeneity. (III) Delayed over electrochemical sintering: A carbon coating temporarily hinders sintering but fractures under cyclic stress, leading to eventual particle coalescence and obstructed ion transport. (IV) Over electrochemical sintering: Uncontrolled sintering in pristine Si leads to large agglomerates that exacerbate strain, cause electrode fracture, and fail to establish efficient long‐range conduction.

Herein, we promote dynamic stress guidance and introduce stress‐lensed electrochemical sintering (SLES) as a strategy to achieve selective electrochemical sintering. This is realized through engineered geometric variation, by precisely depositing Si at the high‐curvature pore entrance of a porous carbon (PC) matrix (first quadrant of Figure 1). During lithiation, these discrete pore entrances act as stress concentrators, analogous to optical lenses focusing light, focally concentrating the mechanical energy. This concentrated stress lowers the activation energy for bond rearrangement, guiding the sintering propensity to form a coherent Si network exclusively along predetermined PC boundaries. Thus, the selectively sintered network effectively reconciles the static‐dynamic conflict and provides continuous, mechanically reliable, and low‐resistance ionic highways. The resulting SLES anode achieves ∼100% capacity retention over 100 cycles and superior rate performance (>80% capacity retention at 1C) in sulfide‐based ASSBs. This work establishes a new principle of geometry‐guided dynamic evolution, turning their most problematic dynamic responses into their greatest design opportunity.

2. Results and Discussion

2.1. Structural Design and Realization of the Stress‐Lens Geometry

To actively guide electrochemical sintering, we engineer a Si‐based composite with spatially defined stress‐lens geometry. As shown in Figure 2a, the key to this design is a PC matrix with abundant, uniformly distributed pore entrances. Through precise deposition, a‑Si is conformally accumulated at these geometrically confined pore entrances, strengthening discrete “stress‑lens” sites while retaining internal void space to accommodate volume expansion. During lithiation, the stress from volumetric expansion of Si is topologically focused at these lens‑like constrictions, generating stress‐concentrated sites precisely at interparticle contacts that actively drive and guide interparticle sintering. In contrast, a control sample (Si‐NES) is designed with a continuous carbon layer that uniformly coats the outer surface, which isolates Si particles, shields interfacial stress, and fully suppresses sintering. To directly compare the spatially controlled stress fields, the Si content in both Si‐SLES and Si‐NES is approximately 50 wt% (measured through a controlled oxidation method, Supporting information).

FIGURE 2.

The stress‐lens geometry structure design and realization. (a) Synthesis schematic of Si‐SLES and Si‐NES from PC. The Si deposits inside the pores and at the pore entrances to ensure surface electrochemical sintering while keeping void space for volume expansion. The C deposits only on the particle surface to shield stress and block electrochemical sintering. (b) Spherical aberration‐corrected HAADF‐STEM of Si‐NES samples, with high‐curvature pore entrances highlighted. (c,d) Corresponding (c) Si and (d) C EDS elemental mappings of (b). (e) N₂ adsorption‐desorption isotherms, (f) Pore size distributions, (g) Small‐angle x‐ray scattering patterns of PC, Si‐SLES, and Si‐NES samples.

The successful construction of the designed “stress lens” architecture is confirmed through multiscale characterization. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images with corresponding energy dispersive spectrometer (EDS) mappings confirm a uniform distribution of Si throughout the PC matrix, with no significant morphological difference between Si‐SLES and Si‐NES (Figure S1‐S6), showing the conformal nature of the initial Si deposition. The new peak at 28 in X‐ray diffraction (XRD) patterns (Figure S7) verifies the successful deposition of Si, which is further corroborated by the emerging peak at 468 cm⁻¹ in Raman spectra (Figure S8) in the Si‐SLES and Si‐NES samples. Spherical aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and corresponding EDS mapping of Si‐NES visually evidence a high‐curvature PC framework (Figure 2b), within which the uniformly distributed Si (Figure 2c) is confined by the continuous carbon phase (Figure 2d). Furthermore, the carbon layer in Si‐NES exhibits a lower I_D/I_G ratio, indicating a higher degree of graphitization compared to the PC matrix, consistent with a distinct, conformal coating. X‐ray photoelectron spectroscopy (XPS) spectra (Figure S9) also confirm that Si‐NES has a lower Si signal and a strong C signal representing the carbon‐isolated structure.

The precisely geometric constriction of “stress lens” was further quantitatively confirmed using gas adsorption‐desorption and small‐angle X‐ray scattering (SAXS) (data summarized in Table S1). As shown in Figure 2e, the pristine PC shows a Type I isotherm with a high specific surface area (∼2000 m² g⁻¹), characteristic of a microporous structure. This high surface area signifies the uniform distribution of abundant pore entrances on the PC surface. Additionally, the hysteresis loop observed in the adsorption‐desorption isotherms indicates an ink‐bottle effect at the pore entrances, further evidencing the presence of high‐curvature pore entrances. After Si deposition, Si‐SLES shows Type III isotherms, suggesting that the deposition of Si leads to the closure of micropores, corresponding to a significant decrease in specific surface area to 48 m² g⁻¹. Subsequent carbon deposition further results in a reduction in its specific surface area to 11 m² g⁻¹, with the corresponding hysteresis loop no longer observed, evidencing the effective shielding of the outer surface in Si‐NES. As the diffusion speed of CO₂ at 273K is faster than N₂ at 77K, CO₂ adsorption‐desorption isotherms were used to analyze the ultra‐micropores of the samples, and their pore‐size distributions were analyzed based on the results. A similar reduction in specific surface area is observed (Figure S10), and the pronounced narrowing of pore entrance size of Si‐SLES directly evidences the formation of high‑curvature constrictions of the intended “lens” geometry (Figure 2f). Small‐angle X‐ray scattering (SAXS) reveals that both Si‐SLES and Si‐NES possess high internal specific surface areas (391 m² g⁻¹ and 339 m² g⁻¹, respectively) (Figure 2g), indicating the deposited carbon primarily locates at the PC surface rather than inside and the preservation of sealed internal voids that are essential for buffering volume expansion.

Thus, the proposed Si‐SLES structure with “stress focusing” at the pore entrance and “volume buffering” in the pore body reduces the volume expansion compared to bulk Si (µSi, Figure S11). Plus, though PC matrix provides only negligible reversible capacity (Figure S12), it substantially enhances the overall electronic conductivity to improve the overall electrode kinetics (Table S2). This unique geometry is expected to selectively guide electrochemical sintering at interparticle contacts while preserving the overall structural integrity of the electrode for ASSBs.

2.2. Stress‐Lens Derived Electrochemical Sintering

The delicately designed stress lens promotes selective electrochemical sintering at interparticle contacts. Finite element simulations of adjacent Si‐SLES particles during the lithiation process visually demonstrate the stress‐lens effect (Figure 3a). The high‐curvature pore entrances in Si‐SLES act as stress concentrators, generating localized stress zones along pore entrances of PC during Si expansion, reducing the Si─Si bond rearrangement barrier, thereby promoting selective sintering at the interparticle boundaries. This strong interparticle bonding leads to toughening solid‐solid interfaces. AFM force‐distance curve analysis measured at particle interfaces (inset Figure 3b) of cycled Si‐SLES and Si‐NES shows that the interface of Si‐SLES exhibits a high Young's modulus of 49 GPa, along with more overlapping approach and retract curves, indicating a lower plastic deformation. In contrast, the interfaces between Si‐NES particles rely on physical contact between particles, resulting in a significantly lower Young's modulus of 10.9 GPa. The pronounced hysteresis between the approach and retract curves indicates irreversible plastic deformation, which would lead to continuous structural destabilization during cycling. The AFM modulus mapping results (Figure 3c and Figure S13) further confirm the high and uniformly distributed Young's modulus at the particle interface of Si‐SLES. Meanwhile, the abrupt drop in Young's modulus at the interfaces of Si‐NES demonstrates discontinuous interfaces between particles. These results verify that the stress lens strongly transforms the solid‐solid physical connections into a mechanically reliable sintered network.

FIGURE 3.

Stress‐lens effect and selectively electrochemical sintering behavior. (a) Stress distribution at the lithiation state of Si‐SLES and the schematic of the role of the stress lens structure in electrochemical sintering. (b) Force‐distance curves from AFM tests on the interparticle gaps of Si‐SLES and Si‐NES after 1 cycle, with measuring points indicated in the inset. (c) AFM modulus mappings of the Si‐SLES anode and the Si‐NES anode after 1 cycle. (d,g) FESEM cross‐sectional images of (d) the Si‐SLES and (g) the Si‐NES pristine anodes. (e,h) FESEM cross‐sectional images with EDS overlayed mappings of (e) the Si‐SLES and (h) the Si‐NES anodes after 1 cycle. Dotted circles indicate sintered particles in the Si‐SLES anode and non‐sintered particles in the Si‐NES anode. (f,i) 3D renderings of the deep‐learning‐segmented Si‐C phase from representative regions of (f) the Si‐SLES and (i) the Si‐NES anodes after one cycle, obtained by FIB tomography. Dotted lines correspond to the features highlighted above.

Consequently, selectively guided sintering behaviors drive the stable dynamic evolution of the anode structure across cycles. Before cycling, both Si‐SLES and Si‐NES electrodes exhibit similar porous structures (Figure 3d,g, and Figure S14‐S15). However, after one cycle, compared to the Si‐NES, the Si‐SLES electrode displays a more fused morphology with fewer cracks (Figure S16). We further scratched off the particles from the cycled electrode and vigorously dispersed them. As shown in Figure S17, Si‐NES maintains its original particle size (5‐7 µm), indicating successful sintering suppression. While the Si‐SLES shows fused aggregates larger than 20 µm, signaling a robust sintered network formation. Focused ion beam (FIB) cross‐sectional morphology images provided by SEM and field emission scanning electron microscope (FESEM) and corresponding EDS mapping images further provide the detailed internal microstructures (Figure 3e,h, and Figure S18). Si‐SLES electrode fuses adjacent anode particles and anode‐electrolyte interfaces with negligible cracks in the anode and the electrolyte, confirming that the localized stress concentrated at the stress lens does not induce mechanical degradation. Meanwhile Si‐NES maintains clear particle boundaries and more cracks due to the stress‐shielding and block effect of the carbon layer. In contrast, µSi representing uncontrolled over‐sintering exhibited severe particle coalescence into large agglomerates with extensive cracking after cycling (Figure S19), highlighting the detrimental effect of unguided electrochemical sintering and underscoring the necessity of the stress‐lens geometry for guiding selective interparticle bonding. These observations are further corroborated by 3D reconstructions obtained by FIB tomography, where only the Si‐C phase is rendered. The Si‐SLES anode exhibits extensive 3D particle connectivity (Figure 3f), whereas Si‐C particles in the Si‐NES anode remain largely isolated, confirming its inertness toward sintering (Figure 3i).

The temperature dependence of the SLES process was further examined (Figures S20 and S21). At 60°C, stress‐lensed sintering effectively formed a coherent Si network, but elevated temperature also accelerated parasitic reactions, lowering the initial Coulombic efficiency. While at 0°C, side reactions were suppressed, but sintering was insufficient due to limited atomic diffusion, and sluggish low‐temperature kinetics prevented full capacity utilization.

To further quantify the structural evolution of the sintered network, porosity and geometric tortuosity were extracted from FIB‐tomography data. Two tortuosity metrics were evaluated: the through‐thickness tortuosity (τ_end), representing the most efficient percolating transport pathway across the electrode, and the domain‐averaged tortuosity (τ_mean), capturing internal transport complexity, including dead‐ends and side branches (Figure S22). After cycling, both Si‐SLES and Si‐NES exhibited a decline in porosity, yet their pore phase tortuosity evolved in opposite directions (Table S3). The pore phase tortuosity of Si‐SLES increased moderately, indicating that substantial densification occurs while maintaining relatively direct connected pathways through the residual pore network. In contrast, the pore phase tortuosity of Si‐NES rose sharply, confirming significant degradation of the pore network. More importantly, the Si phase tortuosity of Si‐NES increased considerably after cycling, indicating a decline of effective long‐range transport pathways. Conversely, the Si phase tortuosity of Si‐SLES decreased substantially after cycling, signaling a transition from a structurally constrained particle network toward a more efficient percolating Si network driven by electrochemically induced restructuring and interparticle sintering.

2.3. Mechano‑Kinetic Synergy From Stress‐Lensed Sintering

The stress‐lensed sintering fundamentally constructs the coherent electrode architecture for a low‐resistance ionic pathway. Finite element simulations of two adjacent particles (#1 and #2) during lithiation show that Si‐SLES maintains a uniform Li⁺ distribution (Figure S23) and a homogenous stress field (Figure 4a), leading to a negligible interparticle stress difference (<0.5 GPa) (Figure 4b). In contrast, in Si‐NES, the carbon coating hinders Li⁺ transport, resulting in a prominent ion distribution gradient. This inhomogeneous lithiation leads to distinct stress accumulation differences between two particles (exceeding 59.5 GPa) (Figure 4b and Figure S24), predisposing them to mechanical failure and increased electrochemical polarization. The robust interparticle bonding coupled with homogeneous stress distribution yields a mechanically durable anode architecture. Particle indentation tests on cycled anodes (Figure 4c,d) demonstrate that sintered agglomerates in Si‐SLES withstand loading up to 10 s before interparticle fracture occurs, corresponding to a substantially higher fracture force of 15.7 mN. In contrast, the loosely aggregated Si‑NES structure fails much earlier (4 s) under 3.4 mN, and further experiences carbon coating failure and particle fracture under higher force.

FIGURE 4.

Mechanical‐reliable and low‐resistance sintered interfaces in Si‐SLES. (a) Stress distribution in two adjacent particles (#1 and #2, separated by dashed lines) of Si‐SLES and Si‐NES at different states of charge. (b) The average stress difference between the two particles at different states of charge. (c) Optical images of Si‐SLES and Si‐NES post‐cycle agglomerates at various loading times in particle indentation tests. (d) Force‐displacement curves from particle indentation tests of Si‐SLES and Si‐NES after 1 cycle. (e,f) KPFM surface potential mappings at the particle interfaces of (e) Si‐SLES and (f) Si‐NES anodes after 1 cycle. (g) The statistical histograms of surface potential data. (h,i) GITT plots of Si‐SLES and Si‐NES during the first‐cycle (h) discharge and (i) charge process. (j) Current‐voltage response obtained from DC polarization of Si‐SLES and Si‐NES.

More significantly, this sintering‐induced structural integration triggers a profound transformation at the electronic/ionic interface. The atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) were employed to test the potential between particles to confirm the interfacial contact quality and charge transfer uniformity (Figure 4e‐g and Figure S25). The Si‐NES anode displays steep, localized potential gradients at particle boundaries, revealing the existence of high‐resistance bottlenecks that hinder interparticle current flow. In contrast, Si‐SLES exhibits a remarkably uniform potential landscape at these sintered interfaces. This homogeneity signifies low interfacial resistance and facilitates rapid, homogeneous ion transport. Galvanostatic intermittent titration technique (GITT) measurements (Figure 4h,i) validate that Si‐SLES achieves more than an order of magnitude higher than higher ionic transport coefficients across all tested states of charge/discharge (SOC/DOD). DC polarization tests (Figure 4j and Figure S26) also show that Si‐SLES exhibits a stronger current response, indicating a higher ionic conductivity under indentical testing conditions.

Electrochemical impedance spectroscopy (EIS) and related distribution of relaxation times (DRT) method show that, after delithiation (2 V vs. Li⁺/Li), the solid‐state diffusion resistance (R_diff) of Si‐SLES is significantly lower than Si‐NES (Figure S27). XPS analysis of SEI on cycled anodes (Figure S28) reveals no significant difference between Si‐SLES and Si‐NES at various etching times, confirming that the substantial disparity in their interfacial impedances is attributed to the electrode structure rather than the SEI. Upon extended cycles, the robust sintered network in Si‐SLES maintains nearly constant impedance in both lithiated and delithiated states (Figures S29‐S32, Tables S4 and S5). Whereas both the electrode internal resistance (R_comp) and R_diff of Si‐NES increase significantly, which indicates the gradual accumulation of “dead Si” in Si‐NES due to the weak point contact and unevenly distributed stress during lithiation. Furthermore, the solid‐state electrolyte resistance (R_SSE) of the Si‐SLES anode remains stable throughout cycling, providing additional electrochemical evidence that the electrolyte is not degraded by the stress‐lens effect. Thus, the SLES accomplishes a robust network with a rapid and stable Li⁺ transport throughout cycling.

2.4. Electrochemical Performances

The integrated structural and ionic benefits directly enable exceptional comprehensive electrochemical performance in Li₆PS₅Cl (LPSCl) based ASSBs. As shown in Figure 5a, Si‐SLES demonstrates dramatically enhanced cycling stability, achieving a capacity retention of ∼100% after 100 cycles, far superior to the 20.6% retention of Si‐NES. Si‐SLES delivers superior Coulombic efficiency, consistently exceeding 99% from the fifth cycle onward, whereas Si‐NES only reaches a comparable level by the 46th cycle (Figure S33). Notably, Si‐SLES maintains stable operation even under reduced stack pressure (20 MPa and 10 MPa) (Figures S34 and S35), indicating stress‐lensed sintering structure enabled a substantial reduction in the required stack pressure to sustain interparticle contacts and enable the self‐healing of the sintering network during cycling, which shows great potential for practical low‐pressure assembly requirements. This stands in stark contrast to its behavior in liquid electrolytes (LE), where pervasive wetting inherently enhances interparticle connection and forms conformal SEI, physically preventing interparticle electrochemical sintering. Instead, the exposed Si and concentrated stress of Si‐SLES lead to a dynamic interface and rapid capacity fade (Figure 5b). This reversal underscores that the beneficial role of SLES is uniquely essential and decisive in the ASSBs.

FIGURE 5.

Electrochemical performances of the Si‐SLES anode. (a) Cycling stability of Si‐SLES and Si‐NES in ASSBs. (b) Cycling stability of Si‐SLES and Si‐NES in LE. (c,d) Contour map of dQ/dV versus voltage at (c) charging and (d) discharging processes of Si‐SLES and Si‐NES at different cycling numbers. (e) Rate performance of Si‐SLES and Si‐NES. (f) Comparisons of the capacity retention rate in the first 100 cycles versus the capacity retention rate at 1C between this work and previously reported results [5, 21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39]. (g) Cycling test of the Si‐SLES || LPSCl || LIC || NCM532 full cell.

Stress‐lensed sintered network largely reduces the electrochemical polarization. This polarization is reflected in first‐cycle charge/discharge profiles, where Si‐NES has significantly higher overpotential (Figure S36). Titration gas chromatography (TGC) analysis after 1 cycle reveals that trapped Li contributes only ∼2.5% of the first‐cycle irreversible capacity of Si‐SLES, confirming that the reduced polarization ensures a near complete delithiation (Figure S37). The dominant irreversible capacity thus originates from SEI formation, including the lithiation of the native SiO_x surface layer into a flexible Li_xSiO_y phase that further reinforces the mechanical integrity of the anode. The dQ/dV distribution maps over the first 50 cycles (Figure 5c,d, and Figure S38) reveal that the lithiation peak positions of Si‐SLES remain highly stable, whereas those of Si‐NES progressively shift, indicating continuously increasing polarization upon cycling. Thus, Si‐SLES anodes underpin remarkable rate performance. As shown in Figure 5e, at the current density of 1 mA cm⁻² (∼1C), Si‐SLES maintains an areal capacity of 1.02 mAh cm⁻², corresponding to 81% retention relative to the capacity measured at 0.05 mA cm⁻². At the high current density of 3 mA cm⁻², Si‐SLES can still have a capacity retention of >50%, while Si‐NES could barely deliver any measurable capacity under the same conditions due to severe kinetic limitations, confirming that ionic rather than electronic transport dominates the rate capability. Comparative benchmarking confirms that Si‐SLES achieves a leading combination of cycle life and rate capability among reported Si‐based sulfide ASSBs (Figure 5f) [21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39]. Furthermore, the practical potential was further validated by a full cell with NCM532 cathode and relatively stable Li₃InCl₆ (LIC) electrolyte at the cathode side (Figure 5g, with cathode mass loading: 24.6 mg cm⁻², initial capacity: 3.03 mAh cm⁻²). The cell exhibits remarkable capacity retention, maintaining over 70% of its capacity through 542 cycles. Even after extended cycling to 700 cycles, it continues to preserve robust capacities above 60%, demonstrating exceptional long‐term stability with minimal decay. Together, these results highlight that the stress‐lensed sintering architecture not only ensures cycling stability but also enables high‐rate operation for ASSBs.

3. Conclusion

We demonstrate that the inherent electrochemical sintering of Si, traditionally viewed as detrimental, can be spatially and energetically guided through deliberate microstructural engineering. The proposed stress‐lensed sintering fundamentally resolves the mechanics‐kinetics trade‐off for practical, high‐performance ASSBs. The PC host with high‐curvature pore entrances acts as a “stress lens”,' selectively concentrating cyclic stress at the interparticle contacts, thereby programming the formation of a continuous, mechanically durable, and ionically rapid Si network. As a consequence, the delicately designed anode delivers exceptional cycling stability (∼100% capacity retention after 100 cycles) and remarkable rate performance (>80% capacity retention at 1C). Furthermore, it meets practical requirements in full‐cell configurations, demonstrating >60% capacity retention after 700 cycles. This principle of geometry‐guided dynamic responses offers a versatile framework for stabilizing other high‐capacity electrodes (e.g., Sn, Li metal) in solid‐state systems, representing an effective strategy for achieving high‐performance ASSBs.

Author Contributions

Q.‐H.Y., S.C.W., and Z.Y.Z. supervised the project and edited the paper. T.Z.X., and Q.D.G. designed the study, wrote the manuscript, carried out the experiments and analyzed the electrochemical data. J.S.Q. performed COMSOL simulations and analyzed simulation results. M.H. and R.B. contributed to the experiment and analysis of FIB‐SEM. Z.Y.Z. contributed to the experiment and analysis of AFM and HAADF‐STEM. F.B.L., S.J.C., Z.S.L. and D.Y.L. performed the SEM and XPS tests. J.X.H., J.X., J.W.H. and W.W. supported the material preparation. All authors discussed the results and commented on the paper.

Conflicts of Interest

The authors declare no conflict of interest.

Supporting information

Supporting File: adma74090‐sup‐0001‐SuppMat.docx.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.