Breaking the Reversibility Barrier in Na–CO ₂ Batteries: A Molten‐Salt Electrolyte and Catalytic RuO ₂ Design

ABSTRACT The practical application of sodium–carbon dioxide (Na–CO 2 ) batteries is impeded by persistent challenges, including high charging overpotential and inadequate cycling stability, which originate from the insulating nature of the discharge product (Na 2 CO 3 ) and detrimental electrolyte decomposition at elevated voltages. Although substantial research has focused on cathode catalysts, the charging voltage typically remains above 4 V, resulting in irreversible side reactions and limited cycle life. In this study, we introduce a nitrate‐based molten‐salt electrolyte strategy to address these issues fundamentally. The NaNO 3– KNO 3– CsNO 3 eutectic electrolyte exhibits a high ionic conductivity of 96 mS cm −1 and a broad electrochemical window, enabling a Na–CO 2 battery with a Super P cathode to operate at a low charge plateau of 3.2 V and deliver a high discharge capacity of 4852 mAh g −1 over 150 cycles. Moreover, by incorporating a RuO 2 catalyst supported on Super P, the charge voltage is further reduced to 3.0 V, and the cycle life exceeds 300 cycles. This work underscores the synergistic effect of molten‐salt electrolytes and heterogeneous catalysts in overcoming kinetic and stability limitations, providing a viable pathway toward practical, high‐performance Na–CO 2 batteries.