A rechargeable calcium-oxygen battery that operates at room temperature.

Ye, Lei; Liao, Meng; Zhang, Kun; Zheng, Mengting; Jiang, Yi; Cheng, Xiangran; Wang, Chuang; Xu, Qiuchen et al. · Nature · 2024

basic_science · Level V

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Abstract

Calcium-oxygen (Ca-O<sub>2</sub>) batteries can theoretically afford high capacity by the reduction of O<sub>2</sub> to calcium oxide compounds (CaO<sub>x</sub>) at low cost<sup>1-5</sup>. Yet, a rechargeable Ca-O<sub>2</sub> battery that operates at room temperature has not been achieved because the CaO<sub>x</sub>/O<sub>2</sub> chemistry typically involves inert discharge products and few electrolytes can accommodate both a highly reductive Ca metal anode and O<sub>2</sub>. Here we report a Ca-O<sub>2</sub> battery that is rechargeable for 700 cycles at room temperature. Our battery relies on a highly reversible two-electron redox to form chemically reactive calcium peroxide (CaO<sub>2</sub>) as the discharge product. Using a durable ionic liquid-based electrolyte, this two-electron reaction is enabled by the facilitated Ca plating-stripping in the Ca metal anode at room temperature and improved CaO<sub>2</sub>/O<sub>2</sub> redox in the air cathode. We show the proposed Ca-O<sub>2</sub> battery is stable in air and can be made into flexible fibres that are weaved into textile batteries for next-generation wearable systems.