A CuS-based composite cathode with a high areal capacity for sulfide-based all-solid-state batteries

All-solid-state batteries (ASSBs) by utilizing sulfide electrolytes (SEs) have recently attracted much attention because of their advantages such as high ionic conductivity and low processing temperature of SEs. To enhance the electrochemical properties of ASSBs such as areal capacity and cycle performance, it is highly desired to obtain an intimate contact between active materials and SEs in the cathode and decrease the content of non-active materials including electronically conductive carbon and SEs. In this work, a carbon-free composite cathode with CuS as the active material and lithium argyrodite Li_5.5PS_4.5Cl_1.5 (LPSCl) as the SE was prepared by ball milling. Due to the tight contact between LPSCl and CuS caused by ball milling, high theoretical specific capacity, and relatively large electronic conductivity of CuS, the ASSB with a composite cathode containing a CuS loading of 10.2 mg cm⁻² delivered a large initial discharge capacity of 434.3 mAh g^–1_electrode based on the cathode mass and a high areal capacity of 5.5 mAh cm⁻² at room temperature. At a higher CuS loading of 20.4 mg cm⁻², an ultrahigh areal capacity of 12.7 mAh cm⁻² and a calculated specific energy of 955 Wh kg^–1_electrode based on the cathode were obtained at 60 °C. Our work demonstrates that the carbon-free, CuS-based composite cathode is a highly promising cathode for high-energy-density ASSBs.