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.