The influence of current density dependent Li2CO3 properties on the discharge and charge reactions of Li-CO2/O2 battery

Abstract

As a promising energy storage technology, Li-CO2/O2 batteries not only deliver ultrahigh discharge capacity but also capture and convert CO2 into renewable energy. The exploration into the deposition and decomposition kinetics of discharge product (Li2CO3) is urgent for the high thermodynamic stability. Herein, the influence of current density on the essential characteristics of Li2CO3 has been explored. The results show that the Li2CO3 with poor crystallinity and elliptical disk morphology can be obtained at medium current density, corresponding to the excellent electrochemical performance including ultrahigh capacity of 5800 mA h/g, lower discharge-charge gap of 1.15 V, and long-term cycle life of 80 cycles. In addition, the morphology and crystallinity of Li2CO3 are tailored by the relative energy barriers for electron migration and O2- generation. At a medium current density (500 mA/g), the accelerated electron migration can realize the nucleation rate equivalent to growth one of Li2CO3. At this time, Li2CO3 will uniformly deposit on the cathode surface, forming elliptical disk morphology with poor crystallinity. Obviously, this work provides new sights for promoting the development of Li-CO2/O2 battery through rational design of catalysts to accelerate the deposition and decomposition processes of Li2CO3.