Preparation And Capacitance Performance Of Ni?Co Phosphate Electrode Materials

Commonly used electrical energy storage devices include lithium batteries,lead-acid batteries,and supercapacitors.Supercapacitors have higher power density and longer life,still have relatively stable performance and higher safety under extreme temperatures.Therefore,they are more suitable as energy storage devices than lithium batteries at low temperatures.Supercapacitors are composed of current collectors,electrode materials,electrolytes,separators,and casings.The electrode materials determine the upper limit of the performance of the supercapacitors and are one of the most important components.Ni?Co phosphates(NCP)have the advantages of low cost,rich reserves,and high electrochemical activity when used as electrode materials.They have not received widespread attention,and there are few related studies,so they have good research prospects.We synthesize the NCP active material on the foamed nickel substrate's surface through a simple one-step low-temperature hydrothermal method to directly obtain the corresponding electrode,thus avoiding the use of binders.To further improve the performance of the electrode material,some carbon materials(AC,CNT and GO)and metal oxides(Cu O,MnO₂ and Co₃O₄)were used for modification.Finally,the electrochemical properties of the samples were tested by CV,GCD,EIS and other methods,and the physical and chemical properties of the samples were characterized by SEM,XRD,RAMAN,SEM,BET and other methods.The main contents of this research are as follows:1.First,the pure NCP electrode material was prepared by the low-temperature hydrothermal method.The influence of the source of raw materials,the molar ratio of Ni/Co,solvent,the hydrothermal temperature,and the filling degree of the reactor on the obtained NCP electrode material was studied by the single-factor control variable method.The results show that the best synthesis conditions are:Ni(NO₃)₂ and Co(NO₃)₂ as raw materials;Ni/Co molar ratio of 1:1;pure deionized water as the solvent;the hydrothermal temperature of160?;The filling degree of the reactor is 60%.The samples obtained under this synthesis condition showed two morphologies in physical and chemical tests:rods with regular shapes and spheres with rough surfaces,with good dispersibility;rod crystals with a diameter of about 0.5?m and a length of about 5-10?m.The spherical structure material's diameter is about 3?m,the median diameter D₅₀ is 7.45?m,and the XRD characteristic peak is not obvious.In the electrochemical test,the specific capacitances at current densities of 1,4,7,10 A/g were 2960 F/g,2876 F/g,2780 F/g and 2706 F/g.The co-existence of nickel ions and cobalt ions will produce a synergistic effect of binary transition metals and improving the electrochemical performance of electrode materials.2.After that,based on the optimal synthesis conditions of pure NCP,we modified the pure NCP through the three carbon materials of CNT,AC and GO,and obtained three composites material of NCP/AC,NCP/CNT and NCP/GO.Then the physical and chemical properties and electrochemical properties of these three composite materials were characterized and analyzed.The results show that the NCP/AC composite has the best overall performance under the condition of reaction time 14 h,1.59 wt%AC addition and add method(1).The material is sea urchin-like with a densely arranged rod-like structure.The rod-shaped material's diameter is about 0.5?m and the length is about 10-15?m.The median particle size D₅₀ is 9.55?m.The particles The diameter has increased.The charging specific capacitances at current densities of 1,4,7,10 A/g are 5800 F/g,4704 F/g,4046 F/g,3562 F/g.Compared with pure NCP,the capacitance performance of the composite material has been significantly improved.Because the introduction of carbon materials enhances the conductivity and establishes more active sites so that the active materials can be fully utilized,thereby improving the electrochemistry performance.3.Finally,we studied the effect of introducing metal oxides on pure NCP.The pure NCP was modified by Cu O,MnO₂ and Co₃O₄.The modified products(NCP/Cu O,NCP/MnO₂ and NCP/Co₃O₄)were characterized and analyzed for their physical and chemical properties,electrochemical properties.The results show that NCP/MnO₂ has the best comprehensive performance under the condition of reaction time 12 h,4.77 wt%MnO₂ addition amount and add method(1),showing a loose micro-flower-like structure with a cross-sectional diameter of about 1?m.The length is about 20-30?m;the diameter distribution is relatively concentrated,and the median diameter D₅₀ is 6.62?m.Compared with pure NCP,NCP/MnO₂has a smaller particle diameter and a larger specific surface area,bringing more active sites and shorter ion channels,which improves the overall electrochemical performance.The specific capacitances at current densities of 1,4,7,10 A/g are 3626 F/g,3336 F/g,3140 F/g,and 3104 F/g.