Preparation And Properties Of Copper Phosphide-based Electrode Materials For Supercapacitor

Supercapacitors have become a powerful alternative for energy storage devices due to their high power density.Electrode materials are the key components of supercapacitors,but current applied electrode materials generally exist the problem of low capacity and energy density.Transition metal phosphides（TMPs）are expected to improve the above shortcomings due to their high theoretical specific capacitance.Currently,researches on TMPs as electrode materials for supercapacitors mainly focus on cobalt and nickel phosphating materials with high cost,while there is almost no exploration on low-cost copper phosphides materials.Therefore,this paper mainly optimized the preparation process of Cu₃P-based materials from the perspective of appropriate doping and recombination,mading up for the large gap between the measured performance and the theoretical predicted performance.In this paper,a series of simple synthesis methods,such as hydrothermal method,solvothermal method and low temperature phosphatization reaction,were used to prepare Cu₃P/r GO composites,MOF-derived Cu₃P doped with trace Ni²⁺and Cu₃P-Ni₂P nanorods arrays.The XRD,SEM,TEM,XPS,CV,GCD and EIS tests were carried out.The synergistic effect between Cu₃P and its composite components was discussed,so that Cu₃P could become an alternative electrode material for high-energy supercapacitors.The main research results are as follows:（1）Cu₃P/r GO composite material was prepared by simple stirring steps and phosphating reaction.Cu₃P particles were hollow spherical structure with a diameter between 400-600 nm,and were loaded on the lamellar folded r GO.The effect of GO content on the electrochemical properties of the composites was investigated.The capacitance of Cu₃P/r GO-0.03 electrode material reaches 470 F g^-1 at 1 A g^-1,and retains 46.0%of the initial specific capacitance at 20 A g^-1.In addition,the cycling performance of asymmetric supercapacitor（ASC）built by it as the cathode electrode is excellent.RGO enhances the conductivity of Cu₃P and disperses Cu₃P particles as an active matrix,increasing the transport channels of electrons and ions and improving the energy storage performance.（2）MOF-derived Cu₃P doped with trace Ni²⁺was prepared by hydrothermal process followed by high temperature reduction and low temperature phosphatization.The effect of Ni content on the electrochemical properties of the Cu₃P/C-6%Ni electrode material was investigated.The obtained Cu₃P/C-6%Ni electrode material has a regular octahedral shape with a side length of about 500 nm and a porous surface.The material has high specific capacitance(576.6 F g^-1 at 1 A g^-1;196 F g^-1 at 20 A g^-1),the specific capacitance of ASC assembled with AC negative electrode and KOH electrolyte can still maintain 81.8%of the initial value after 5000 cycles of testing,showing excellent cycling stability.The energy density is up to 15.2 Wh kg^-1 at 800.1 W kg^-1.The doping of Ni²⁺exposes more defects on the surface of Cu₃P,thus forming a large number of reaction sites.The doping effect improves the electrochemical activity of the materials.（3）Cu₃P-Ni₂P composite electrode material directly grown on the copper foam substrate was obtained by in-situ oxidation,hydrothermal method and low temperature phosphatizing method.It has nanorods structure and good arrangement,and its rough surface provides more reaction sites for active substances.Compared with single Cu₃P material,its electrochemical performance is greatly improved.The specific capacitance at 1 A g^-1 reaches 770 F g^-1.After 1600 charge-discharge cycles,the specific capacity can retain 81.1%of the initial value,which is due to the synergistic effect of bimetallic compounds.The direct construction of nanoscale active materials on conductive substrates not only avoids"dead surfaces"caused by adhesives and conductive agents,but also speeds up electron transport,thus maximizing the use of active materials.