Insight of electro-chemo-mechanical process inside integrated configuration of composite cathode for solid-state batteries

The complicated electro-chemo-mechanical process that occurs inside the composite cathode for solid-state batteries (SSBs), is of first importance to be insighted for the development of SSBs to seek higher energy density. Herein, exampled with layered transition-metal oxide of LiNi_xCo_yMn_1-x-yO₂ (NCM), an electro-chemo-mechanical model containing electrochemical kinetics, finite-strain constitutive model and cohesive zone model was built to uncover the impact of ionic conductivity and Young's modulus (E) of solid-state electrolyte (SE) on the electro-chemo-mechanical process inside composite cathode and the intergranular failure of single cathode particle. The intergranular failure of NCM particles is powerfully determined by the Young's modulus of SE and the primary particle size, which is postponed by the coarse-primary NCM with soft SE of E=∼2 GPa. Compared with Young's modulus, increasing the ionic conductivity can uniform the distribution of both Li-ion and stress in the whole composite NCM cathode, realizing improved electrochemical performance with larger normalized capacity and lower the interfacial impendence. Hence, high-adequate ionic conductivity of 5 × 10⁻⁴ S cm⁻¹ and soft mechanical property of E=∼2 GPa can be proposed as the guideline of SE for great electrochemical performance with prolongated lifespan of composite NCM cathode, paving an avenue to foster the application of SSBs.