Quantitative regulation of electrochemical-mechanical performance of composite cathode in all-solid-state batteries

Abstract

The intricate interplay between electrochemical and mechanical phenomena and the volumetric changes leading to interfacial stability within composite cathodes exerts a profound influence on the long-term cycling performance of all-solid-state batteries (ASSBs). This study quantitatively assesses a novel approach aimed at modulating the electrochemical-mechanical performance within composite cathodes by integrating LiNi1−x-yCoxMnyO2 (NCM) with LiCoO2 (LCO) particles. The insightful evaluation is conducted through a multiphysics modeling strategy. The NCM and LCO particles, each displaying distinct open-circuit voltage-concentration relationships, interact and evolve in a two-stage manner during charging, with their coupled electrochemical-mechanical behaviors remaining relatively insensitive to particle positioning. Stage I is dominated by the mechanical response due to NCM particle shrinkage (stress σMises≈1.3 GPa, debonding gap Gd≈1.8 nm). Stage II is governed by the mechanical stress accumulation resulting from the expansion of LCO particles (σMises≈7 GPa, Gd≈62 nm). The choice of solid electrolyte (SE) materials plays a competing role with the modulating of NCM/LCO ratio since SEs possess high compression-bearing capabilities favoring a higher LCO content, while those characterized by robust interfacial strength with particles allow for greater NCM content. Results offer valuable insights into designing more resilient and enduring composite cathodes, unlocking the design and manufacturing of long-cycling ASSBs.