Heterostructured CuCo₂S₄-Co₉S₈ Nanosheets as Freestanding Cathodes for Flexible Fiber-Shaped Li-CO₂ Batteries

Li-CO2 batteries with attractive characteristics of high energy density power supply and carbon dioxide fixation have attracted widespread attention. However, the lack of suitable cathode catalysts and their unsatisfactory electrochemical performance have impeded their development as promising Li-CO2 batteries for energy storage. Constructing heterojunctions by interfacial engineering to improve performance is considered one of the effective strategies. Herein, heterostructured CuCo2S4-Co9S8 nanosheets are fabricated by a facile hydrothermal method and employed as efficient cathode catalysts for Li-CO2 batteries. The construction of heterojunctions by interfacial engineering has proved as an effective strategy to enhance the electrochemical performance of the Li-CO2 batteries. The delocalized electrons between CuCo2S4 and Co9S8 contribute to a low median charge potential (∼3.6 V), small polarization (0.62 V), high energy efficiency of up to 83%, and outstanding cycle life (480 h) of the CuCo2S4-Co9S8 cathodes. Meanwhile, as a proof of concept, flexible fiber-shaped Li-CO2 batteries based on these cathodes are fabricated and demonstrate boosted flexibility adaptability and provide a stable power supply at various bending conditions.