Preparation Of Cr,Mo,W Doped Nickel Cobalt Hydroxide Phosphide And Its Electrochemical Properties

As a new type of energy storage device with high specific capacitance,long cycle life and fast charge/discharge rate,supercapacitors have received a lot of attention.Its electrode material plays a crucial role in the performance of the device.The development of electrode materials with high specific capacitance,low cost,environmental protection and long life has been the focus of research.In the paper,three elements,Cr,Mo and W,were mainly used to dope NiCo-based metal hydroxides,and their effects on the electrochemical properties of the complexes were investigated.In addition,their corresponding phosphides were prepared by phosphorylation,and then the effects of doping elements on the electrochemical properties of the phosphides were investigated to elaborate the energy storage mechanism.The specific contents are as follows:1.NiCo-LDH electrode materials were prepared by a simple one-step hydrothermal method.On this basis,NiCoM-LDH(M=Cr,Mo,W)composites were synthesized by introducing three different metal ions to create synergistic effects between different metal ions.The overall electrochemical performance of the electrode materials can be improved by controlling the ratio of metal ions introduced during the preparation process and adjusting the microstructure of the materials.The results showed that the overall electrochemical performance of the electrode materials was best when the ratios of Ni:Co:Cr,Ni:Co:Mo and Ni:Co:W were all 1:1:0.05.In the three-electrode test system,the specific capacities of NCC0.05,NCM-0.05 and NCW-0.05 at 1 A g-1 were 2350 F g-1,2670 F g-1 and 1968 F g-1,respectively,which were better than those of pure NiCo hydroxide(NC)at 1 A g-1(1676 F g-1)when the current density was increased to 10 A g-1.The specific capacities of NCC-0.05,NCM-0.05 and NCW-0.05 can still be maintained at 1717 F g-1,1580 F g-1 and 1500 F g-1,showing a better rate capability.In addition,the assembled NCC//AC,NCM//AC and NCW//AC supercapacitor devices exhibit high energy densities of 43.3 Wh kg-1,47.64 Wh kg-1 and 41.24 Wh kg-1,respectively.2.On the basis of transition metal hydroxide,Cr,Mo and W elements were introduced into the NiCo bimetallic phosphide by low-temperature decomposition of NaH2PO2 under N2 environment to form NCCP,NCMP and NCWP composites with unique three-dimensional flower shape.The electrochemical test analysis showed that the prepared NCCP,NCMP and NCWP electrode materials exhibited higher capacity and cycling stability compared with the NCP materials,with specific capacities of 1839 F g-1,1580 F g-1 and 1500 F g-1 at a current density of 1 A g-1,respectively,which were higher than that of 1128 F g-1 for the NCP electrode materials,indicating that the ion-to-ion synergistic effect can accelerate the redox reaction and thus improve the electrochemical performance.In addition,the optimal doping amounts of Cr,Mo and W doping,respectively,were investigated and obtained by electrochemical tests,where NCCP-0.25,NCMP-0.05 and NCWP-0.1 showed the optimal electrochemical performance compared to the other ratios of the samples.The devices assembled with NCCP//YP50,NCMP//YP50 and NCWP//YP50 also exhibit high energy densities of 29 Wh kg-1,23.8 Wh kg-1 and 24.5 Wh kg-1,respectively,which are better than NCP//YP50(23 Wh kg-1).