Superionic lithium argyrodite-type sulfide electrolyte with optimized composite cathode fabrication enabling stable All-Solid-State Batteries

All-solid-state batteries (ASSBs) are promising candidates for next-generation energy storage devices. However, several key aspects especially superionic solid electrolytes (SEs) and carefully designed electrode configurations still remain a challenge for the development of high performance ASSBs. Herein, a halogen-rich lithium argyrodite, Li_5.5PS_4.5Cl_0.8Br_0.7 (LPSCB) with optimized synthesis condition is successfully prepared. Electrochemical impedance spectroscopy and X-ray diffraction illustrate that annealing temperature affects Li-ion dynamics, which guides the formation of LPSCB with a high room-temperature ionic conductivity of 10.7 mS cm⁻¹. Furthermore, LiNi_0.9Co_0.05Mn_0.05O₂ with ZrO₂ dual-functional coating layer (ZrO₂@NCM) was introduced as cathode active materials (CAMs) to guarantee high-energy-density composite cathode. Correspondingly, a better understanding of the optimization of composite cathode design based on the superionic LPSCB is well elucidated and fast ion/electron transport is achieved by revealing the effect of different CAM fractions in the cathodes on the rate and cycling performance. Specifically, ASSBs with 60 wt.% and 80 wt.% CAM deliver high discharge capacity of 1.1 and 1.95 mAh cm⁻² at −20 °C and 60 °C, with corresponding capacity retention of 86.4 % and 69.7 % after 100 and 150 cycles, respectively. This work demonstrates the necessity of customizing CAM fractions depending on the desired applications of ASSBs, and provides an effective cathode modification strategy toward the development of sulfide-based ASSBs with excellent electrochemical performance.