One-pot synthesis of high-performance N-doped Co（PO₃）₂@C negative electrode materials for supercapacitors

We synthesized a cobalt metaphosphate and nitrogen（N） doped carbon（C） composite（Co（PO3）2@C） by an one-pot method using green phytate（PA）, melamine（MA）, cobalt acetate tetrahydrate（Co（OAc）2·4H2O）, and polyvinylidene fluoride（PVDF） hollow fiber membrane as raw materials. Among them, PA can be used as a green phosphorus（P） source since PA is a hexadentate ligand with six phosphate groups and the oxygen atom（O） in each phosphate group can be used as a coordination atom to react with cobalt ions to form a complex with stable chemical properties. MA is rich in N elements, and PVDF hollow fiber membrane contains fluorine（F） element, which can also provide a framework structure. The doping of N and F elements can make the porous carbon material have better wettability, which facilitates the electron transfer in the electrolyte, thus greatly improving the electrochemical performance of the material. The prepared active negative electrode material has a specific capacitance of 1067.42 F·g-1 at the current density of 1 A·g-1. Even at the current density of 10 A·g-1, the capacitance retention rate of 85.79% can be achieved after 20000 cycles.