Study On Doping,Modification And Capacitance Properties Of CoCr Hydrotalcite

With the wide use of clean energy,exploring new storage and conversion technology has become the key to solve the efficient utilization of clean energy.Electrochemical energy storage was considered to be the most promising renewable energy storage technology due to its high efficiency and flexibility.Among them,supercapacitors have been studied for their strong charge storage capacity and high cycling stability.Among many electrode materials,hydrotalcite compounds have been applied to the electrode materials of supercapacitor due to their advantages of high theoretical specific capacitance,adjustable structural composition and environmental protection.However,the hydrotalcite electrode materials have the disadvantages of poor electrical conductivity and easy agglomeration,which leads to the reduction of ion transport channels.Therefore,optimizing the structure of hydrotalcite material to improve its electrochemical conductivity is very important to improve the electrochemical performance of hydrotalcite material.Therefore,in this paper,CoCr hydrotalcite is doped and modified to promote the ion transport rate,improve its electrical conductivity and optimize its electrochemical performance.(1)CoCr hydrotalcite(CoCr-LDHs)was synthesized by one-step hydrothermal method,and the optimum reaction conditions were obtained by electrochemical performance test.The best electrochemical properties of CoCr hydrotalcite were obtained under the conditions of Co:Cr=3:1.5,synthesis temperature 160°C and hydrothermal reaction time 4 h.The results show that the specific capacity is 614.8 F/g at 1 A/g,the specific capacitance is still 44.3%at 20 A/g.After 2000 cycles,34.9%of the initial specific capacity at 10 A/g.(2)Based on the optimal synthesis conditions of CoCr-LDHs,in order to improve the electrical conductivity and rate performance,first CoCr-LDHs was doped with nickel,and then CoCr Ni-LDHs was etching treatment.CoCr Ni-LDHs showed the best electrochemical performance when doped with 1 mmol of Ni²⁺.When the etching concentration was 2 mol/L,the sample specific capacity and rate capability reached the maximum.When the current density is 1 A/g,the specific capacity of CoCr Ni-LDHs increases from 955.1 F/g to 1405.2 F/g;the specific capacity decays by 30.53%at 20 A/g.(3)The influence of etching/sulfuration composite treatment on the electrochemical performance of CoCr Ni-LDHs was investigated by using a two-step method by changing the concentration of Na OH solution and the solubility of Na₂S solution respectively.Etching treatment concentration was 2 mol/L and sulfuration treatment concentration was 2 mol/L,the sample showed the best rate performance.At 1 A/g,the specific capacitance is 1501.3 F/g.When the current density is increased by 20 times,the specific capacity remains 64.3%of the initial value.The specific capacity of the sample decays by 21.3%after 2000 cycles at 20A/g.There are 44 figures,11 tables and 152 references in this paper.