Electrochemical Stability of Li5.4(PS4)(S0.4Cl1.0Br0.6) in an All-Solid-State Battery Comprising LiNbO3-Coated Li(Ni0.8Co0.1Mn0.1)O2 Cathode and Lithium Metal Anode

Abstract

All-solid-state lithium-ion batteries are a promising next-generation technology because they have higher energy densities than their liquid-electrolyte counterparts. Recently, halogen-rich argyrodite, specifically Li5.4(PS4)(S0.4Cl1.0Br0.6), has been reported to show higher ionic conductivities than other sulfides with argyrodite structures and electrochemical stability against lithium metal. However, the stability of Li5.4(PS4)(S0.4Cl1.0Br0.6) against cathode active materials in all-solid-state batteries has not yet been evaluated. Herein, we report the electrochemical stability of Li5.4(PS4)(S0.4Cl1.0Br0.6) as a solid electrolyte in an all-solid-state battery. Li(Ni0.8Co0.1Mn0.1)O2 and lithium metal were used as the cathode and anode, respectively, and an enhancement in the discharge capacity was expected. The impedance of the battery was almost independent of the frequency above 106 Hz for 50 charge/discharge cycles. These findings are a result of the constant lithium-ion resistance of Li5.4(PS4)(S0.4Cl1.0Br0.6). X-ray diffraction analysis confirmed that no byproduct phase was formed in the cathode mixture over 50 cycles. These results demonstrate the high chemical stability of Li5.4(PS4)(S0.4Cl1.0Br0.6) against Li(Ni0.8Co0.1Mn0.1)O2, thereby broadening the design scope of electrolyte materials for all-solid-state lithium-ion batteries with high performance and stability.