Preparation And Electrical Properties Of Calcium Carbide-Based Carbon Materials

With the development of the electronics industry and the widespread use of electronic products,the market demand for high-capacitance supercapacitors is becoming more and more urgent.The rich variety of carbon materials,large specific surface area,simple preparation,and low price make it a good capacitor material and have broad application prospects in the field of electrochemistry,but its low specific capacity will affect the overall performance of the capacitor.In this paper,two types of carbon spheres were prepared and chemically activated by oxidation and hydrothermal methods respectively.The optimal molar ratio of activated carbon to alkali was determined,and the electrochemical performance of carbon spheres was improved by compounding with different metal oxides,in order to obtain high-performance carbon materials composite electrode material.Spheres were successfully prepared by controlling the reaction time for 10h by oxidation,a series of carbon materials?CM?were synthesised by changing the reaction time.The effects of reaction time on the morphology and capacitance performance of carbon materials were studied using FESEM and electrochemical tests.The results showed that calcium carbide was used as carbon.The morphology of the carbon material prepared from the source gradually changed from spherical to massive as the reaction time shortened.Among them,the CM₈ has the best capacitance performance,with a specific capacitance of 32.69F·g^-1 and a small solution resistance of 2.3?.Its rate performance is better than CM₄?retention rate of 68%?when the current density is 2A·g^-1?retention rate is 60%?.CM was activated by KOH and changes the carbon-alkali molar ratio(R_CM/KOH)to obtain a series of high specific surface area carbon materials.After being activated with KOH,the carbon material as a whole appears loose,increasing the specific surface area of the carbon material,which is beneficial to the infiltration of the electrolyte and the formation of the electric double layer,thereby increasing the specific capacitance of the carbon material.With the decrease of R_CM/KOH,both the specific surface area and the specific capacitance of the carbon materials show an increasing trend.When the R_CM/KOH is 0.5:1,the specific surface area and specific capacitance of ACM_0.5 both reach the maximum,S_BET is 1114.3m2·g^-1,and the specific capacitance is 165.47F·g^-1.It has good charge and discharge performance and can be used as super electrode material for capacitors.At the same time,the two-step activation mechanism of KOH is analyzed and proposed.It is believed that KOH activation of CM is mainly due to the chemical reaction of carbon materials with different compounds to form0.19nm micropores.Carbon spheres/Co₃O₄ composites were prepared by using carbon spheres as templates and using two different composite methods?direct precipitation method and solvothermal method?to composite activated calcium carbide-based carbon spheres with Co₃O₄ respectively.XRD,FTIR and electrochemical tests were used to analyze the structure and electrochemical properties of the composites.The experimental results show that the carbon spheres/Co₃O₄composite(C-Co'₁₀)prepared by the solvothermal method has better electrochemical performance,such as a larger specific capacity(the specific capacitance of C-Co'₁₀ is156.29F·g^-1 greater than C-Co₁₀ 18.42F·g^-1),faster diffusion rate(N-quist curve of C-Co'₁₀composite material is closer to 45°than C-Co₁₀),and better cycle stability(after 500 cycles,C-Co'₁₀(Cyclic retention rate of 97.94%is greater than 93%of C-Co₁₀).This may be due to the smaller particle size and better dispersion of the composites prepared by the solvothermal method.In addition,when the mass ratio of carbon spheres and cobalt nitrate is 1:10,the material electrodes C-Co₁₀ and C-Co'₁₀ prepared by two composite methods respectively have the best electrochemical performance,and the specific capacitances are 18.42F·g^-1 and156.29F·g^-1,the solution impedance?R_S?is 0.03?and 0.02?,respectively.The carbon spheres prepared by hydrothermal method using glucose as the carbon source were activated,and their specific capacitance increased from 2.46F·g^-1 to 142.37F·g^-1 before activation.At the same time,the resistance R_ct of the carbon sphere charge transfer is small after activation,and has good conductivity stability?after 500 cycles,its cycle retention rate is85.12%?.At 0.5A·g^-1 and the ammonium molybdate content is 10%,the prepared carbon spheres/MoO₃ composite has the best electrochemical performance,which a specific capacitance is 151.67F·g^-1,charge transfer resistance R_ctt and ion diffusion resistance both are small.After 500 cycles,the retention rate of cycle rate is 89.21%,which is better than single carbon spheres and other carbon spheres/MoO₃ composite materials.The composite of carbon spheres and MoO₃ improves the cycle life of a single material and reduces the charge transfer resistance of a single material.