Enhanced capacity of all-solid-state battery comprising LiNbO₃-coated Li(Ni_0.8Co_0.1Mn_0.1)O₂ Cathode, Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) solid electrolyte and lithium metal anode

All-solid-state lithium-ion batteries are a promising next-generation technology because they have higher energy densities than their liquid-electrolyte counterparts. Halogen-rich argyrodite, specifically Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6), was recently shown to have higher ionic conductivities compared with those of other argyrodite-like sulfides. Although the Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) in Li | Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) | Li(Ni_0.8Co_0.1Mn_0.1)O₂–Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) batteries have shown good electrochemical stability, the low discharge capacity limits the application of the battery. In continuation, this study examined the potential of a carbon additive for altering the electronic conductivity of the cathode and enhancing the capacity of Li | Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) | Li(Ni_0.8Co_0.1Mn_0.1)O₂–Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) batteries. After a 50-cycle charge/discharge, the carbon additive (0.1 C) enhanced the discharge capacity from 3.1 to 167 mAh/g, resulted in a capacity retention rate and coulombic efficiency of 95.4% and 99.9% when using 0.1 C and 0.5 C, respectively, and increased the resistance of the battery from 53 to 56 Ω. Therefore, the all-solid-state battery employing high-ion-conductive Li_5.4(PS₄)(S_0.4Cl_1.0Br_0.6) and a carbon-modified cathode showed improved capacity. This study provides a proven framework for developing all-solid-state batteries employing halogen-rich argyrodite (Li_7-α(PS₄)(S_2-αX_α); α > 1) with enhanced ionic conductivities.