On the Role of Interfacial Mechanical Damage in Composite Cathodes for All- Solid-State Batteries

Abstract

Solid-state-batteries (SSBs) present a promising technology for next-generation batteries due to their superior properties including increased energy density, wider electrochemical window and safer electrolyte design. A particularly attractive SSB architecture features a lithium metal anode, a composite solid-state cathode and an inorganic SSE separating the electrodes. While an attractive alternative, successful commercialization of SSBs still faces many challenges and is contingent upon resolution of a series of chemo-mechanical stability issues. One such concern is associated with integrity of composite electrodes. Both cathodes and anodes may consist of a composite of active particles surrounded by a solid-state electrolyte matrix. During cycling, the active particles undergo electrochemically induced expansion and contraction while the SSE provides an ion pathway for Li diffusion. Developing models for these systems requires an understanding of three critical components: i) the behavior of the active particles themselves, ii) the behavior of the solid-state electrolyte, and iii) the combined behavior of the composite electrode.Our work investigates the effect of mechanical damage at the interface between active material and solid-state electrolyte, specializing on a LCO-LGPS composite cathode for SSBs. We model chemo-mechanical interactions between active particles under galvanostatic charging conditions and study the evolution of interfacial damage under varying material and microstructural properties. Specifically, we investigate different electrolyte compositions with varying stiffness as well as different active particles with varying volumetric expansions, and their effect on interfacial stresses, mechanical damage, and the overall electrochemical response of the system. Finally, we discuss how variations in microstructural composition can alter the state of interfacial damage. Both packing effects and particle size distribution are discussed for electrode compositions of different active material to understand from a design perspective how these factors can impact integrity of the interface and overall electrochemical performance.