Carbon-coated Li2S cathode for improving the electrochemical properties of an all-solid-state lithium-sulfur battery using Li2S-P2S5 solid electrolyte

Li2S is coated with carbon to improve the electrical conductivity of the composite cathode in all-solid-state lithium-sulfur batteries. Carbon is applied by thermal evaporation from a polyacrylonitrile (PAN) source at 600 °C for 5 h. It is shown that the carbon coating is impurity free, and the crystallinity of Li2S is well maintained. The electronic conductivity of Li2S is dramatically improved from 9.21 × 10−9 S cm−1 to 2.39 × 10−2 S cm−1 upon carbon coating. An all-solid-state battery prepared with the carbon-coated Li2S shows a high initial capacity of 585 mAh g−1 (g of Li2S) that increases up to 730 mAh g−1 (g of carbon-coated Li2S) by the 10th cycle. This high capacity is stable throughout the 25 cycles tested, with an excellent coulombic efficiency of 99%. Carbon-coated Li2S is advantageous for all-solid-state batteries due to the increased electrical conductivity, while allowing a reduction of the total carbon content present in the composite cathode.