Origin of high electrochemical stability of multi-metal chloride solid electrolytes for high energy all-solid-state lithium-ion batteries

All-solid-state batteries (ASSBs) have gained substantial attention because of their intrinsic safety and potentially high energy density. To enable ASSBs, developing solid-state electrolytes (SSEs) with high electrochemical stability is of foremost significance. Here we report a multi-metal chloride SSEs with an excellent electrochemical stability (up to 4.5 V vs. Li+/Li), which originates from the strong Zr-Cl bonding. In addition, a high room-temperature ionic conductivity of 1.58 mS/cm was achieved via increasing the Li vacancies in the structure as well as balancing carrier and vacancy concentration. Coupled with nickel-rich cathodes (LiNi0.83Co0.12Mn0.05O2) and high-voltage LiCoO2 (4.5 V vs. Li+/Li), ASSBs demonstrated superb electrochemical performance. This work provides an in-depth structural understanding of multi-metal chloride SSEs and feasible strategies to realize high-energy-density ASSBs.