Li3InCl6-Coated High-Voltage Cathodes for Thiophosphate-Based Solid-State Li Batteries

Abstract

Solid-state Li batteries are pursued as potentially safe and stable high-energy storage systems. However, key issues remain unsolved, impeding the practical realization.[1] One of the fundamental reasons for the failure of these batteries is likely the instability of solid-state electrolytes, such as Li6PS5Cl, towards high voltage cathodes. To mitigate the interface instability issues coating materials that prevent the decomposition of the solid-state electrolytes without limiting the ionic transport across them are thus urgently warranted.[2,3] Halides have been shown to have excellent high voltage stability up to 4.2 V in combination with moderate Li-ion conductivities of the order of magnitude ~10-3 S cm-1.[4]Combining the properties of halides with sulfides, hence, could be a promising strategy to enable room temperature solid-state Li batteries. Therefore, we synthesized nano-sized Li3InCl6 powder by mechanochemistry.Thereafter, Li3InCl6 was coated onto micrometer-sized LiNi0.8Co0.15Al0.05O2 (LIC@NCA) cathode particles using mechanofusion technique. The thickness and uniformity of the coating were investigated using FIB-SEM and TEM. The coating thickness has been found to be as thin as 200 nm nanometers fully covering the NCA particles. Finally, LIC@NCA particles have been tested in a solid-state Li batteries using Li:In-alloy as anode and Li6PS5Cl as SSE. Cells with LIC@NCA show a significant improvement (from 60 mAh/g to 150 mAh/g) in respect of the initial capacity loss and capacity fading compared to the pristine NCA.