Boosting the Electrochemical Performance of All‐Solid‐State Batteries with Sulfide Li6PS5Cl Solid Electrolyte Using Li2WO4‐Coated LiCoO2 Cathode

Solid‐state batteries exhibit promising prospects due to their potential in terms of safety and energy density. Sulfide solid electrolytes have received much attention due to their high ionic conductivity (about 10−2 S cm−1). However, high side reactions between solid sulfide electrolytes and oxide cathodes, such as LiCoO2, have hampered the development of all‐solid‐state sulfide batteries. Here, first‐principles calculations and experiments are combined to demonstrate a novel protective layer to cope with the Li6PS5Cl electrolyte and LiCoO2 cathode interface problem. By uniformly coating LiCoO2 with a layer of Li2WO4, the interfacial resistance (the 100th cycle) between the sulfide electrolyte and LiCoO2 is reduced to about 68 Ω cm2, which is nearly 15 times lower than the premodified 1061 Ω cm2. The 2 wt% Li2WO4‐coated LiCoO2(2%LWO‐LCO)/Li6PS5Cl/Li‐In all‐solid‐state battery exhibits satisfactory capacity and excellent cycling stability at room temperature (93% capacity retention after 100 cycles). Furthermore, the ab initio molecular dynamics based on the Perdew, Burke, and Ernzerhof density functional theory calculations show that Li2WO4 can effectively prevent the diffusion of Co and O from LiCoO2 into the Li6PS5Cl solid electrolyte. It is shown that molecular dynamics help predict the interfacial reactions in all‐solid‐state sulfide batteries. Combining the prediction of first‐principles calculations and experimentation, a novel material of Li2WO4 is adopted to reduce the interfacial resistance between LiCoO2 cathode and the sulfide electrolyte. The electrochemical performance shows that the Li2WO4‐coated LiCoO2 can significantly improve the all‐solid‐state battery electrochemical performance based on Li6PS5Cl sulfide solid electrolyte.