In Situ Sodiation of CoSe 2 Modulating Charge Transfer in Sodium−Selenium Batteries
Ningxun Zhang, Chenyang Gao, Junfeng Liang, Jian Zhu, Xu Tan, Wenlu Yuan, Zheng Yang, Huchong Yao, Shengjie Peng, Tao Wang, Yuping WuABSTRACT
Selenized polyacrylonitrile (SePAN), characterized by the unique C−Se covalent bonds, can suppress the formation of polyselenides and their associated shuttle effect in sodium−selenium (Na−Se) batteries. However, its polymeric structure and distinct conversion mechanism lead to sluggish redox kinetics, severely limiting the rate capability. To overcome these challenges, we propose a catalyst−charge transfer mediator strategy to accelerate the conversion kinetics of SePAN by leveraging the intrinsic dynamic electrochemical behavior of CoSe 2 additives. We demonstrate that CoSe 2 weakens both C−Se and Se−Se bonds, thereby facilitating their cleavage and subsequent conversion. Moreover, the synchronized sodiation of CoSe 2 forms Na x CoSe 2 intermediates, which reorganize the local charge density at the Na 2 Se 2 /Na x CoSe 2 interface. This process induces an additional interfacial charge transfer of 0.36 e , significantly enhancing conductivity. By incorporating CoSe 2 into SePAN nanofibers, the bifunctional strategy enables Na−Se batteries to achieve outstanding rate performance, delivering a high capacity of 404.3 mAh g −1 at an ultra‐high rate of 10 C. Overall, this study provides comprehensive insights into the rational design and mechanistic role of CoSe 2 catalysts in high‐performance Na−Se batteries.