Urchin-like\nγ‑MnO<sub>2</sub>/Carbon\nNanotubes as an Efficient Cathode Catalyst for Durable Solid-State\nLithium and Sodium-CO<sub>2</sub> Batteries

Metal-CO<sub>2</sub> batteries integrate the benefits of carbon\ndioxide capture and efficient energy storage, representing a prospective\ninnovation in energy storage systems. In particular, most of the research\nattention has been concentrated on Li-CO<sub>2</sub> and Na-CO<sub>2</sub> batteries due to their high energy density and discharge\npotential. However, the excessive accumulation of discharge products\nand the volatilization of the liquid electrolyte restrict the further\nadvancements of these batteries. Herein, we synthesized an urchin-like\nγ-MnO<sub>2</sub> cathode catalyst that enables a rapid and\nreversible CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) and\nthe CO<sub>2</sub> evolution reaction (CO<sub>2</sub>ER). The assembled\nsolid-state Li/Na-CO<sub>2</sub> batteries with Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>- and Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub>-based composite solid electrolytes\nfacilitate uniform stripping/deposition of metallic anodes, thereby\nensuring the long-term cycling stability of batteries. The assembled\nLi/Na-CO<sub>2</sub> batteries exhibit cycling stability for 240 and\n100 cycles, respectively, at a current density of 200 mA g<sup>–1</sup> and a cutting-off capacity of 500 mAh g<sup>–1</sup>. Even\nat a high current density of 500 mA g<sup>–1</sup>, the batteries\nstill possess excellent rate capability. This work provides a promising\nsolution to reduce the costs of cathode catalysts and enhance safety\nfor Li/Na-CO<sub>2</sub> batteries.