Sodium-ion batteries(SIBs)are promising alternatives to lithium-ion batteries(LIBs)for large-scale en-ergy storage considering the abundance and low cost of Na-containing resources.However,the energy density of SIBs has been limited by the typically low specific capacities of traditional intercalation-based cathodes.Metal fluorides,in contrast,can deliver much higher capacities based on multi-electron con-version reactions.Among metal fluorides,CuF2 presents a theoretical specific capacity as high as 528 mAh/g while its Na-ion storage mechanism has been rarely reported.Here,we report CuF2 as a SIB cath-ode,which delivers a high capacity of 502 mAh/g but suffers from poor electrochemical reversibility.As a solution,we adjust the cell configuration by inserting a carbon-coated separator,which hinders the trans-portation of dissolved Cu ions and improves the reversibility of the CuF2 cathode.By using in-situ XRD measurements and theoretical calculation,we propose that a one-step conversion reaction occurs during the discharge process,and a reconversion reaction competes with the oxidization of Cu to dissolved Cu ion during the charge process.

Yiming Dai;Qiujie Chen;Chenchen Hu;Yangyang Huang;Wangyan Wu;Mingliang Yu;Dan Sun;Wei Luo

Institute of New Energy for Vehicles,School of Materials Science and Engineering,Tongji University,Shanghai 201804,China;CAS Key Laboratory of Design and Assembly of Functional Nanostructures,and Fujian Provincial Key Laboratory of Nanomaterials,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002,China;Haixi Institute,Xiamen Institute of Rare Earth Materials,Chinese Academy of Sciences,Xiamen 361021,China

中国化学快报（英文版）

[1]Yiming Dai;Qiujie Chen;Chenchen Hu;Yangyang Huang;Wangyan Wu;Mingliang Yu;Dan Sun;Wei Luo-.Copper fluoride as a low-cost sodium-ion battery cathode with high capacity)[J].中国化学快报（英文版）,2022(03):1435-1438

CuF2,reconversion

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