Atomic Level Fabrication of Oxychloride Interface for High‐Rate and High‐Voltage Lithium‐Ion Batteries

Abstract In recent years, oxychloride‐based materials have emerged as a promising solid‐state electrolyte (SSE) candidate owing to its ultrahigh ionic conductivity and decent cathode compatibility. Although the fabrication of SSE coatings for cathode materials has been recognized as a promising strategy, a precise synthesis of oxychloride‐based SSE coating is still not realized due to the lack of appropriate preparation method. As a proof of concept, we propose a superior lithium‐ion conductive aluminum‐based oxychloride (LAOC) coating synthesized by atomic level fabrication strategy with unique self‐limiting reaction mechanism. The LAOC modified lithium cobalt oxide (LCO) cathode exhibits a high capacity retention of 86.4% after 500 cycles at 5 C and significantly improved high‐voltage cycling stability. The outstanding performance is ascribed to the high interfacial ionic conductivity and construction of robust cathode electrolyte interphase. The ionic conductivity of LCO increased from 1.785 × 10 −7 to 2.823 × 10 −6 S cm −1 after LAOC coating. Scanning transmission X‐ray microscopy and transmission electron microscopy reveal that the LAOC coating suppresses interfacial degradation and mitigates the structural collapse of LCO. This study offers great opportunity for the atomic level fabrication of superior ionic conductive oxychloride thin films to realize high performance lithium‐ion batteries.