High loading CuS-based cathodes for all-solid-state lithium sulfur batteries with enhanced volumetric capacity

Transition metal sulfides have shown to improve the performance of lithium-sulfur batteries both with liquid and solid electrolytes. In this work, the beneficial effect of copper sulfide for enabling high areal capacity lithiumsulfur all-solid-state batteries is shown. Copper sulfide-carbon (CuSC) and three different copper sulfide-sulfurcarbon (CuSS) composites are investigated as positive electrodes in all-solid-state lithium-sulfur batteries. The composites are prepared via facile and low-cost mechanochemical ball-milling. It is found that the CuS/C ratio greatly influences the redox properties of the CuSC cathode. Scanning electron microscopy, ex-situ X-ray diffraction, and galvanostatic cycling were also conducted to evaluate the CuSS composite electrodes in Li|LiI-Li$_{3}$PS$_{4}$|CuS–S–C solid-state cells. High mass loading cells made using these composite electrodes deliver capacities as high as 1600 mAh g$^{-1}$$_{(CuS+S)}$ and 7 mAh cm$^{-2}$ at 20 °C. The higher density of CuS also leads to larger volumetric capacities, up to 3900 mAh cm$^{-3}$$_{(CuS+S)}$, thus enabling a potential energy density gain up to 15% with respect to a conventional Carbon–Sulfur cathode.