Heterostructured CuCo<sub>2</sub>S<sub>4</sub>‑Co<sub>9</sub>S<sub>8</sub> Nanosheets as Freestanding Cathodes for Flexible\nFiber-Shaped Li-CO<sub>2</sub> Batteries

Li-CO<sub>2</sub> batteries with\nattractive characteristics of\nhigh energy density power supply and carbon dioxide fixation have\nattracted widespread attention. However, the lack of suitable cathode\ncatalysts and their unsatisfactory electrochemical performance have\nimpeded their development as promising Li-CO<sub>2</sub> batteries\nfor energy storage. Constructing heterojunctions by interfacial engineering\nto improve performance is considered one of the effective strategies.\nHerein, heterostructured CuCo<sub>2</sub>S<sub>4</sub>-Co<sub>9</sub>S<sub>8</sub> nanosheets are fabricated by a facile hydrothermal\nmethod and employed as efficient cathode catalysts for Li-CO<sub>2</sub> batteries. The construction of heterojunctions by interfacial engineering\nhas proved as an effective strategy to enhance the electrochemical\nperformance of the Li-CO<sub>2</sub> batteries. The delocalized electrons\nbetween CuCo<sub>2</sub>S<sub>4</sub> and Co<sub>9</sub>S<sub>8</sub> contribute to a low median charge potential (∼3.6 V), small\npolarization (0.62 V), high energy efficiency of up to 83%, and outstanding\ncycle life (480 h) of the CuCo<sub>2</sub>S<sub>4</sub>-Co<sub>9</sub>S<sub>8</sub> cathodes. Meanwhile, as a proof of concept, flexible\nfiber-shaped Li-CO<sub>2</sub> batteries based on these cathodes are\nfabricated and demonstrate boosted flexibility adaptability and provide\na stable power supply at various bending conditions.