Modified Lithium Borate Buffer Layer for Cathode/Sulfide Electrolyte Interface Stabilization

Abstract

. All-solid-state rechargeable batteries, using nonflammable sulfide-based solid electrolytes, address lithium-ion battery safety issues while enhancing energy density and operating temperature range. However, the electrochemical stability limitations of sulfide electrolytes present challenges to the interface stability, particularly with oxide-based cathodes. The application of a stable coating layer is known to be effective for stabilizing the cathode/sulfide electrolyte interface. In particular, lithium borate is a promising coating material owing to its cost-effectiveness and efficiency in controlling interfacial reactions. However, lithium borate exhibits oxide characteristics, leading to a difference in the chemical potential of Li + compared to sulfide electrolytes. This discrepancy results in an uneven distribution of Li + ions at the interface, which hinders Li-ion migration during charge and discharge cycles. To address this issue, a lithium borate-coating layer was modified with sulfur via a gaseous reaction involving sulfur. Sulfur-modified lithium borate is expected to reduce the chemical potential difference of Li + and