Preparation And Electrochemical Performance Of Nickel-cobalt-aluminum Layered Double Hydroxide

Hydrotalcite-like materials which are used as supercapacitor electrode materials have been widely studied and have got great achievements in recent years.In this paper,a nickel-cobalt-aluminum layered double metal hydroxide（NiCoAl-LDHs）electrode material was successfully prepared by hydrothermal method.The effects of conditions such as the ratio of nickel-cobalt-aluminum metal ions,the reaction time of hydrothermal reaction,the reaction temperature,and the ratio of precipitant to the nickel metal salt on the electrochemical performance of electrode materials were investigated.The effects of different templating agents and their amounts on the micromorphology and electrochemical performance of NiCoAl-LDHs electrode materials were studied.NiCoAl-LDHs electrode materials were prepared by hydrothermal method.The effects of the ratio of metal ions,reaction time,temperature,and concentration ratio of precipitant to nickel salt on the properties of nickel-cobalt-aluminum hydroxide were investigated.The results show that when the ratio of nickel-cobalt-aluminum salt is 2:1:1,the hydrothermal reaction time is 12 h,the temperature is 120℃,and the ratio of urea to nickel salt is 4:1,the prepared materials have better electrochemical performance.Specific capacity at 1 A·g^-1 and 10 A·g^-1 are 1188 F·g^-1 and 952 F·g^-1,respectively.After 2000 charge and discharge cycles,the capacity retention rate can reach 85.2%.NiCo-LDHs,Ni Al-LDHs,Co Al-LDHs and NiCoAl-LDHs materials were prepared by hydrothermal method,and their morphology and electrochemical characterization were performed.The results show that the micro-morphology of the four materials are cluster-shaped spheres piled up by petal-like structures,and the structural particles of NiCoAl-LDHs material are independent and uniform,which helps increase the specific surface area of the material.The specific capacitances of the four materials at 1 A·g^-1 were 894 F·g^-1,942 F·g^-1,885 F·g^-1 and 1068 F·g^-1,respectively.During the preparation of NiCoAl-LDHs materials,the ratio of the amount of metal nickel salt to Tween-80 can optimize its electrochemical performance.The experimental results show that the specific capacitances of the four materials at the current of 1 A·g^-1 are 1336 F·g^-1,1433 F·g^-1,1430 F·g^-1,and 1289 F·g^-1,respectively.This shows that the addition of the templating agent effectively improves the chemical properties of the material.The electrochemical performance of asymmetric supercapacitor（ASC）was tested by using Tween-80 electrode with 0.003 mol as positive electrode and AC as negative electrode.The results show that the energy density of ASC is as high as 89.79 Wh·kg^-1 at a power density of 775.0 W·kg^-1.This shows that NiCoAl-LDHs//AC ASC with high energy density shows huge potential applications in the next generation of energy storage devices.The effects of the amounts of the four template agents PVA,PVP,CTAB and SDS on the electrochemical performance of the materials were investigated.The results showed that when the added amount of PVA,PVP,CTAB and SDS was 0.75 g,1.00 g,1.00 g and 1.00 g respectively,the obtained electrode material had the best electrochemical performance,and the specific capacity was 1454 F·g^-1,1553 F·g^-1,1648 F·g^-1 and 1420 F·g^-1 at 1 A·g^-1.After 2000 cycles,the capacity retention rates were 83.8%,88.4%,90.0%and 83.5%respectively.Asymmetric supercapacitor（ASC）was assembled with 1.00 g of CTAB electrode and activated carbon（AC）,and tested for electrochemical performance.The results show that when the power density of ASC is 800 W·kg^-1,the energy density is as high as 75.55 wh·kg^-1.After 2000 cycles at the current density of 10 A·g^-1,the capacity retention rate of ASC is 89.9%,showing excellent electrochemical performance.