Synthesis And Electrochemical Properties Of Spherical Layered Double Hydroxides

As a typical two-dimensional material,layered double hydroxides(LDHs)have been widely used because it is easy to prepare and budget-friendly.At the same time,due to the adjustability of the composition,structure and morphology of hydrotalcite,LDHs have drawn more and more attention in terms of electrochemical energy storage.However,the research on the electrochemical properties of LDHs is basically based on their composition and structure.There are few studies on the effect of LDHs morphology in terms of electrochemical performance,and the methods for preparing special morphology LDHs are complex.This paperintroduces the spherical Co-Al LDHs which was prepared by a two-step method using a spherical basic cobalt salt as a precursor,and electrochemical tests were carried out.NiCoAl LDHs were prepared by doping nickel into Co-Al LDHs while maintaining the spherical morphology.The specific steps are as follows:The alkaline cobalt salt was prepared by hydrothermal synthesis under specific conditions,and then the alkaline cobalt salt was converted into Co-Al LDHs while the spherical morphology remained unchanged.The effect of different feed ratios,temperature,pH and time on the morphology of Co-Al LDHs formed during the conversion process were explored.It was found that the Co-Al LDHs were synthesized at a molar ratio of cobalt to aluminum of 1.5:1,pH=13,reaction temperature of 80? and reaction time of 12 h.With electrochemical testing,it was found that when the current density was 0.1 A·g-1,the specific capacitance would be 823.2 F·g-1,and when the current density was increased to 2 A·g-1,the specific capacitance would be maintained up to 783.46 F·g-1,which could charge and discharge 2500 times in 0.5 A·g-1,while maintaining 94.93%of the initial capacitance,with good rate and large specific capacitance.Preparation of NiCoAl LDHs can be achived by using spherical Co-Al LDHs as precursors by doping nickel into it.The effect of different feed amounts,temperature,time and amount of reactant dispersion on the morphology of NiCoAl LDHs were analyzed during the preparation process.It was found that the input amount of the reactant Na2[NiCl4]solution(1 ml/L)was 10 ml,the reaction temperature was 70?,the reaction time was 7 h,and the dispersion amount of Co-Al LDHs suspension was 1 g/100 mL.The NiCoAl LDHs prepared below are spherical with uniform morphology.with electrochemical testing,it was found that when the current density is 0.2 A·g-1,the specific capacitance is 853.18 F·g-1,and it can be charged and discharged at a large current density of 5 A·g-1.Maintaining 822.08 F·g-1,charging and discharging 1000 times at 1 A·g-1,still retaining 98.94%of the initial capacitance.By comparison,it was found that the spherical NiCoAl LDHs posseses higher specific capacitance as the electrode material,with better rateperformance and lower resistance.