| Supercapacitors,as a new energy supply device for automobiles,are expected to alleviate the problems of fossil energy crisis and environmental pollution.Graphene oxide（GO）and ABO3 perovskite are the most studied supercapacitor electrode materials.GO is commonly used as a negative electrode,which has both double layer capacitance and pseudocapacitance,but its synthesis method is simple.ABO3perovskite is commonly used as a positive electrode,and the oxygen vacancy content has a significant effect on its electrochemical properties.In this paper,GO was prepared by microwave plasma-enhanced chemical vapor deposition（MPCVD）,and thconcentration of oxygen vacancy in lanthanum cobaltate（LaCoO3）was increased by microwave plasma etching.The electrochemical properties of GO and LaCoO3 were tested and the effect of oxygen vacancy content（%Vo）on the electrochemical properties of LaCoO3 was analyzed.Then,these two materials were used as positive and negative electrodes to make asymmetric supercapacitor.The working voltage,energy density,power density and charging and discharging efficiency of the device were tested.Finally,based on the electrochemical experiment results of the device,a power system model of a certain bus supercapacitor was built,and the power performance is matched and simulated.The results showed that the GO prepared by MPCVD has the typical coiling and stacking morphology of graphite-like materials.But it has more defects at the edges.The cyclic voltammetry test results showed that the GO has a pair of wide and weak redox peaks near-0.6V potential,indicating that it has both double-layer capacitance and pseudocapacitance.Its maximum specific capacitance is 197 F/g.Its specific capacitance retention rate is 94%after 2000 charge and discharge cycles at a current density of 5A/g in the three-electrode system.Microwave plasma etching results showed that the surface and edge of LaCoO3particles became rough after etching.After 2.5 min etching in argon and hydrogen gas atmosphere,lanthanum oxide vacancy content of cobalt increased from 51.58%to56.65%.When the etching time was prolonged to 5 min under the same atmosphere,and the oxygen vacancy content was increased to 62.24%,which was higher than the etching effect of pure argon atmosphere（53.07%）.Constant current charge-discharge test results show that the LaCoO3 with 62.24%of Vo has the best electrochemical performance.Its specific capacitance can up to 706.9 F/g,which is twice than that of unetched LaCoO3.The electrochemical impedance test found that it has the smallest1.48Ωcharge transfer resistance.An asymmetric supercapacitor was formed by the above two materials.Go was used as the negative electrode and LaCoO3 was used as the positive electrode.According to the experimental tests,the specific capacitance of LaCoO3//GO asymmetric supercapacitor can up to 134 F/g at the current density of 1 A/g.When the current density increased to 50 A/g,the specific capacitance can still up to 98.5 F/g,and the capacity retention rate is 73.5%.In addition,the results show that the energy density of LaCoO3//GO asymmetric supercapacitor can reach up to 47.64 Wh/kg,and the power density can reach up to 37,080 W/kg.After 4000 cycles of charging and discharging,the specific capacitance has no decrease,and the charging and discharging efficiency maintains about 95%.The state of charge（SOC）estimation model of a single LaCoO3//GO asymmetric supercapacitor is established by using the ampere-time integration method and the open-circuit voltage method,which is in good correspondence with the experimental results.A supercapacitor module is formed by a series of 375 asymmetric supercapacitor monomers.The power source model of a 17 t bus with a total energy of180 kWh is composed of 100 supercapacitor modules in parallel.Simulink simulation results show that the bus equipped with the supercapacitor can run for 1.8 hours at the maximum design speed of 71 km/h,and the maximum travel range is about 130 km. |
