Fluorine and Copper Codoping for High Performance Li₂O-Based Cathode Utilizing Solid-State Oxygen Redox

Transition-metal-doped Li₂O cathodes using redox reaction of solid-state oxygen are candidates as high capacity cathode materials for lithium-ion batteries. In our previously reported study, copper-doped Li₂O (CuDL) exhibited a high charge-discharge capacity of 300 mAh g^-1. However, the developed cathode not only exhibited poor cyclability but also decomposed during charge-discharge cycles. In this study, fluorine and copper were codoped into the Li₂O structure by stepwise mechanochemical reaction to create a high performance cathode with high cyclability. Fluorine-, copper-doped Li₂O (F-CuDL) was prepared by the mechanochemical reaction of Li₂O with LiF, followed by a reaction with CuO. The F-CuDL cathode exhibited a good cycle performance (300 mAh g^-1, 30 cycles at a constant current of 50 mA g^-1). X-ray diffraction (XRD) and Cu K-edge X-ray absorption near edge structure (XANES) analyses revealed that F-CuDL does not undergo decomposition even after charge-discharge cycles, revealing that doping with fluorine leads to the stabilization of the CuDL crystal structure.