Urchin-like γ-MnO₂/Carbon Nanotubes as an Efficient Cathode Catalyst for Durable Solid-State Lithium and Sodium-CO₂ Batteries

Metal-CO2 batteries integrate the benefits of carbon dioxide capture and efficient energy storage, representing a prospective innovation in energy storage systems. In particular, most of the research attention has been concentrated on Li-CO2 and Na-CO2 batteries due to their high energy density and discharge potential. However, the excessive accumulation of discharge products and the volatilization of the liquid electrolyte restrict the further advancements of these batteries. Herein, we synthesized an urchin-like γ-MnO2 cathode catalyst that enables a rapid and reversible CO2 reduction reaction (CO2RR) and the CO2 evolution reaction (CO2ER). The assembled solid-state Li/Na-CO2 batteries with Li7La3Zr2O12- and Na3Zr2Si2PO12-based composite solid electrolytes facilitate uniform stripping/deposition of metallic anodes, thereby ensuring the long-term cycling stability of batteries. The assembled Li/Na-CO2 batteries exhibit cycling stability for 240 and 100 cycles, respectively, at a current density of 200 mA g–1 and a cutting-off capacity of 500 mAh g–1. Even at a high current density of 500 mA g–1, the batteries still possess excellent rate capability. This work provides a promising solution to reduce the costs of cathode catalysts and enhance safety for Li/Na-CO2 batteries.