Understanding Kinetics of Complex Interfaces in Solid-State Batteries from Multiscale Simulations

Abstract

Developing viable solid-state batteries requires understanding the various chemical and physical processes that occur at homogeneous and heterogeneous solid-solid interfaces. Examples include internal grain boundaries, interphases, and electrode-electrolyte interfaces, each of which can play a key role in determining transport and cycling stability. To explore these impacts in detail, our team has been applying simulations from the atomic scale to the mesoscale, considering the structure, chemistry, and dynamics of the solid-state interfaces. We will provide an overview of these activities as applied to the garnet Li7-xLa3Zr2O12 (LLZO) solid electrolyte system. First, we will show how mesoscale phase-field models can be combined with atomistic simulations of grains and grain boundary regions to predict and assess the transport properties of interface-dominated systems. We apply this framework to determine the operating conditions and microstructural considerations for which grain boundaries appreciably affect diffusion mechanisms and pathways in LLZO. Second, we will show how ab initio simulations are applied to isolate local chemical motifs that act as precursors to interphase formation at the LLZO-cathode interface. Evidence of interdiffusion and structural reorganization at the interface provides clues into possible degradation mechanisms, in addition to impacting interfacial impedance. Overall, the simulation results highlight the importance of considering interfaces in realistic materials descriptions of solid-state batteries, while simultaneously highlighting the possible tunability of microstructure at multiple scales to impact performance.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.