Preparation And Capacitance Properties Of Nickel-based Double-metal Hydroxide Materials

In this paper,two kinds of electrode materials of nickel-aluminum double hydroxide(NiAl-LDH)and nickel-cobalt double hydroxide(NiCo-LDH)were prepared by solvothermal and hydrothermal method.The influence of the amount of surfactant and the ratio of mixed solvents on the properties of the material was investigated in solvothermal method.In hydrothermal method,in addition to exploring the effects of the dosage of surface active agent,reaction temperature and reaction time on the performance of the synthetic materials,the electrochemical performance difference between the binder-free electrode which is directly grown on the conductive substrate and the powder electrode is also compared.The composition and morphology of the materials were analyzed by XRD and SEM,and the electrochemical properties of the prepared double-metal hydroxide were studied by electrochemical correlation test.NiAl-LDHs were prepared by solvothermal method.The effects of the amount of oleylamine and the ratio of alcohol-water mixed solvents on the morphology and electrochemical properties of the materials were investigated.The results showed that when the amount of oil amine was 1.49 mmol and the volume ratio of alcohol to water was 1:1,the NiAl-LDH material had the best performance.The specific capacities at 1 A/g and 10 A/g were 1147.2 F/g and 740.9 F/g respectively,and the capacity retention rate was 64.6%.The capacity retention rate was 74.9% after 2000 cycles at 2 A/g.A simple hydrothermal method was used to prepare NiAl-LDH binder-free electrode material under the condition of polyvinylpyrrolidone(PVP)as a surfactants,and compared with the powder electrode prepared under the same condition.The electrochemical test results showed that the electrochemical performance of NiAl-LDH was improved significantly by in-situ growth on foamed nickel.In addition,the influence of the amount of PVP on the electrochemical performance of NiAl-LDH was also investigated.The results showed that NiAl-LDH had the best performance when 1.25 g PVP was added.The specific capacities of NiAl-LDH at 1 A/g and 10 A/g were 1074.2 F/g and 898.8 F/g,respectively,and the capacity retention rate was 84.1%,showing a good rate performance.The capacity retention rate was 63.8% after 2000 cycles.The NiCo-LDH binder-free electrode material was prepared by a simple hydrothermal method.The effects of the dosage of PVP,reaction temperature and reaction time on the properties of NiCo-LDHs were investigated in the experiment.The experimental results showed that NiCo-LDH prepared with PVP addition of 1 g,reaction temperature of 120 °C and reaction time of 12 h had the best electrochemical performance.The specific capacity values at the current densities of 1 A/g and 10 A/g were 1449.8 F/g and 1154.1 F/g,respectively,and the capacity retention rate was 79.6%.After 2000 cycles,the specific capacitance values had almost no attenuation.An asymmetrical supercapacitor(NiCo-LDH//AC)was assembled by using NiCo-LDH as the positive electrode and activated carbon as the negative electrode,respectively.The specific capacity of NiCo-LDH//AC at 0.5 A/g is 96.9 F/g,and when the current density increases to 10 A/g,the specific capacity is 52 F/g.Only 6% of capacity was lost after 2000 cycles.The energy density could reach 32.3 Wh/kg at a power density of 387.1 W/kg.