Microstructure and Pressure-Driven Electrodeposition Stability in Solid-State Batteries

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Interfacial deposition stability at the Li-metal-solid electrolyte interface in all solid-state batteries is governed by the stress-transport-electrochemistry coupling in conjunction with the polycrystalline/amorphous solid electrolyte architecture. In this work, we delineate the optimal solid electrolyte microstructure comprising grains, grain boundaries, and voids possessing desirable ionic conductivity and elastic modulus for superior transport and strength. An analytical formalism is provided to discern the impact of external “stack” pressure-induced mechanical stress on electrodeposition stability; the stress magnitudes obtained are in the megapascal range, considerably diminishing the stress-kinetics effects. For experimental stack pressures ranging up to 10 MPa, the impact of stress on reaction kinetics is negligibly small, and electrolyte transport overpotentials dictate electrodeposition stability. High current density operation with stable deposition can be ensured with ample external pressure, high temperature, and low surface roughness operation for a low shear modulus ratio of the solid electrolyte to Li-metal. Solid electrolyte architecture is screened via virtual generation and characterization Large grain size, low void size, and porosity provide favorable conduction and stiffness Stack pressure <10 MPa has negligible impact on stress-kinetics coupling High operating pressure, temperature, and low roughness can aid stable deposition Lithium electrodeposition is dependent on solid electrolyte microstructure, stack pressure, and operating temperature. Verma et al. suggest a method to delineate the architecture and operating conditions that lead to stable deposition.