In-situ imaging electrocatalysis in a solid-state Li-O2 battery with CuSe nanosheets as air cathode

The development of highly efficient catalysts in the cathodes of rechargeable Li-O2 batteries is a considerable challenge. To enhance the electrochemical performance of the Li-O2 battery, it is essential to choose a suitable catalyst material. Copper selenide (CuSe) is considered as a more promising cathode catalyst material for Li-O2 battery due to its better conductivity and rich electrochemical active sites. However, its electrochemical reaction and fundamental catalytic mechanism remain unclear till now. Herein, in-situ environmental transmission electron microscopy technique was used to study the catalysis mechanism of the CuSe nanosheets in Li-O2 batteries during discharge and charge processes. It is found that Li2O was formed and decomposed around the ultrafine-grained Cu during the discharge and charge processes, respectively, demonstrating excellent cycling. This indicate that the freshly formed ultrafine-grained Cu in the conversion reaction catalyzed the latter four-electron-transfer oxygen reduction reaction, leading to the formation of Li2O. Our study provides important understanding of the electrochemistry of the Li-O2 nanobatteries, which will aid the development of high-performance Li-O2 batteries for energy storage applications.