Advanced Li/Na–CO2 Batteries Enabled by the γ-MnO2 Catalyst with Enhanced Carbonate Decomposition

Metal–CO2 batteries, especially Li–CO2 and Na–CO2 batteries, are regarded as ideal new-generation energy storage systems owing to their high energy density and extraordinary CO2 capture capability. However, the advancement of metal–CO2 batteries is still at an early stage. The problems caused by accumulation of carbonates during charge–discharge cycles, such as large polarization and poor reversibility, restrict their practical application. Therefore, designing efficient catalysts is crucial for promoting the decomposition of carbonate to improve the electrochemical performance of metal–CO2 batteries. Herein, we first adopted sea urchin-like γ-MnO2 as the cathode material for Li/Na–CO2 batteries. Benefiting from the unique structure and excellent catalytic activity of γ-MnO2, the as-prepared Li–CO2 and Na–CO2 batteries can achieve low overpotentials of 1.28 and 1.36 V, respectively, at a current density of 100 mA g–1 with a cutoff capacity of 1000 mA h g–1. The overpotentials are lower than those of most of the state-of-the-art catalysts in previous reports. After 100 and 50 cycles of Li–CO2 and Na–CO2 batteries, respectively, their charging termination voltages remain at around 4.1 and 3.9 V, respectively; such a low charging platform indicates the excellent catalytic activity of the γ-MnO2 cathode on the discharge products. Our findings offer a promising guideline to design efficient electrocatalysts for high-performance metal–CO2 batteries.