Balancing Ionic and Electronic Conductivities in All-Solid-State Batteries: The Effect of LPSCl Coating Thickness on Cathode Active Materials

Abstract

All-solid-state batteries (ASSBs) with sulfide solid electrolytes are promising next-generation battery technologies that exhibit excellent thermal stability and mitigate problems related to thermal runaway. However, loose interparticle connections between active materials and solid electrolytes in ASSBs, which can lead to low reversible capacity, render studying ASSBs challenging. Herein, we fabricate LiNi0.8Co0.1Mn0.1O2 (NCM811)@Li6PS5Cl (LPSCl) core–shells using a mechanofusion process to address a point-contact problem within the cathode composite of ASSBs. Determining the optimal layer thickness for LPSCl coatings is crucial because excessively thick or thin layers can hinder electron or ion conduction throughout the cathode composite. A mixture of core–shell and LPSCl using NCM811@LPSCl core–shells with a 90:10 weight ratio, featuring an adequately thin LPSCl coating layer of ≈320 nm, exhibits moderate effective electronic and ionic conductivities of 1.78 × 10−6 and 1.72 × 10−3 S cm−1, respectively. The cathode composite using this core–shell also exhibits considerably enhanced rate capability, with a reversible capacity of 170.9 mAh g−1 at 0.5 C. This study demonstrates that NCM811@LPSCl core–shells with improved contact points and balanced ionic and electronic conductivities can enhance the utilization yield of cathode active materials and improve the electrochemical performance of ASSBs.