Despite progress in solid-state battery engineering, our understanding of the chemo-mechanical phenomena that govern electrochemical behavior and stability at solid-solid interfaces remains limited compared to solid-liquid interfaces. Here, we use operando synchrotron X-ray computed microtomography to investigate the evolution of lithium/solid-state electrolyte interfaces during battery cycling, revealing how the complex interplay between void formation, interphase growth, and volumetric changes determines cell behavior. Void formation during lithium stripping is directly visualized in symmetric cells, and the loss of contact at the interface between lithium and the solid-state electrolyte (Li 10 SnP 2 S 12) is found to be the primary cause of cell failure. Reductive interphase formation within the solid-state electrolyte is simultaneously observed, and image segmentation reveals that the interphase is redox-active upon charge. At the cell level, we postulate that global volume changes and loss of stack pressure occur due to partial molar volume mismatches at either electrode. These results provide new insight into how chemo-mechanical phenomena can impact cell performance, which is necessary to understand for the development of solid-state batteries. File list (2) download file view on ChemRxiv Manuscript Updated.pdf (1.08 MiB) download file view on ChemRxiv Supplementary Information.pdf (1.02 MiB)

In this Perspective, we assess the promise and challenges for solid-state batteries (SSBs) to operate under fast-charge conditions (e.g., <10 min charge). We present the limitations of state-of-the-art lithium-ion batteries (LIBs) and liquid-based lithium metal batteries in context, and highlight the distinct advantages offered by SSBs with respect to rate performance, thermal safety, and cell architecture. Despite the promising fast-charge attributes of SSBs, we must overcome fundamental challenges pertaining to electro-chemo-mechanics interaction, interface evolution, and transport-kinetics dichotomy to realize their implementation. We describe the mechanistic implications of critical features including plating-stripping crosstalk, metallic filament growth, cathode microstructure, and interphase formation on the fast-charge performance of SSBs. Toward achieving the eventual goal of fast-charge in SSBs, we highlight both intrinsic (e.g., interface design, transport properties) and extrinsic (e.g., temperature, pressure) design factors that can favorably modulate the mechanistic coupling and cross-correlations. Finally, a list of key research questions is identified that need to be answered to gain a deeper understanding of the fast-charge capabilities and requirements of SSBs.

Transformation of the electrodeposition morphology, facilitated by the surface self-diffusion across a step

Solid‐state batteries (SSBs), utilizing a lithium metal anode, promise to deliver enhanced energy and power densities compared to conventional lithium‐ion batteries. Penetration of lithium filaments through the solid‐state electrolytes (SSEs) during electrodeposition poses major constraints on the safety and rate performance of SSBs. While microstructural attributes, especially grain boundaries (GBs) within the SSEs are considered preferential metal propagation pathways, the underlying mechanisms are not fully understood yet. Here, a comprehensive insight is presented into the mechanistic interactions at the mesoscale including the electrochemical‐mechanical response of the GB‐electrode junction and competing ion transport dynamics in the SSE. Depending on the GB transport characteristics, a highly non‐uniform electrodeposition morphology consisting of either cavities or protrusions at the GB‐electrode interface is identified. Mechanical stability analysis reveals localized strain ramps in the GB regions that can lead to brittle fracture of the SSE. For ionically less conductive GBs compared to the grains, a crack formation and void filling mechanism, triggered by the heterogeneous nature of electrochemical‐mechanical interactions is delineated at the GB‐electrode junction. Concurrently, in situ X‐ray tomography of pristine and failed Li7La3Zr2O12 (LLZO) SSE samples confirm the presence of filamentous lithium penetration and validity of the proposed mesoscale failure mechanisms.

Vehicular electrification necessitates the need for fast charge of lithium-ion batteries (LIBs) involving high current densities such that the charging durations reach equivalence with internal combustion engine vehicles refueling times. High C-rate performance of LIBs requires overcoming challenges associated with Li plating, thermal excursions and battery shutdown at sub-zero temperatures. In this work, we aim to understand/improve fast charge characteristics by delving into the electrode level microstructural impact on battery performance in terms of delivered capacity, temperature rise and plating propensity. A microstructure-aware physics-based electrochemical-thermal model is used to ascertain the performance-safety indicators from sub-zero to standard thermal environments. Fast charge is an anode-centric phenomenon; consequently, optimal anode porosities and operating conditions are ascertained. At sub-zero temperatures, high C-rate operation up to a threshold provides good capacities and low plating propensity through large heat generation induced cell temperature elevation to appreciable levels. Beyond the threshold current, self-shutdown of the cell prevents any degradation. Additionally, standard thermal environment operation is majorly limited by rapid temperature rise beyond safe limits and large plating propensities at low porosities.