Modeling And Simulation Of Electrochemical Properties Of Porous Carbon Electrode Materials With Different Dimensions Based On Supercapacitors

Supercapacitors as new energy storage devices have the advantages of long cycle life and high power density.The supercapacitor equivalent model can control the material structure by analyzing the impedance characteristics and charge-discharge behavior of the electrode material.Electrode materials play a decisive role in the performance of supercapacitors.Carbon materials are widely used in electric double-layer supercapacitors due to their large specific surface area,good conductivity,and stable performance.In the research of carbon materials,researchers always use the same modified Randall equivalent circuit model to analyze the impedance characteristics of different materials,but this model is less applicable to each carbon material,and there are deviations in the analysis of materials.Optimization of supercapacitors requires updated models to capture material-scale physical properties and characterize their electrical output.In view of the above shortcomings,on the basis of the original model,taking the dimension of typical carbon materials as the breakthrough point,four equivalent circuit models of carbon materials for electric double layer capacitors are established,and the models are verified with the impedance measured by the experiment and the constant current charge and discharge data,and explore the effect of changing the impedance parameter value in the model on the simulated charge and discharge.The main research contents are as follows:（1）Test the electrochemical properties of graphene quantum dots with zero-dimensional point-like structure.According to its working principle and impedance data,on the basis of its pore structure with macropores and mesopores,an equivalent circuit of zero-dimensional electric double layer electrode material is established.The impedance fitting error of the modified Randall equivalent circuit model is 64.81%lower than that of the modified Randles equivalent circuit model.According to the experimental data of constant current charge and discharge,a model is built in MATLAB for charge and discharge simulation,the RMSE（Root Mean Square Error）of the model is calculated to be 0.1097 V.The increase of the model resistance parameters will cause the simulation voltage drop to increase to varying degrees,and the increase of R_ct3 has the greatest impact on the voltage drop.（2）Test the electrochemical properties of carbon nanotubes with one-dimensional tubular structure.According to its working principle and impedance data,on the basis of its mesoporous pore structure,an equivalent circuit model of a one-dimensional electric double layer electrode material is established.The resultant error is 37.70%lower than that of the modified Randles equivalent circuit model.According to the experimental data of constant current charge and discharge,a model was built in MATLAB for charge and discharge simulation,the RMSE of the model was calculated to be 0.0710 V.The increase of the model resistance parameters will cause the simulation voltage drop to increase to varying degrees,and the increase of R_ct2 has the greatest impact on the voltage drop.（3）To test the electrochemical properties of graphene with two-dimensional layered structure,according to its working principle and impedance data,on the basis of its pore structure with macropores and mesopores,an equivalent circuit model of a two-dimensional electric double layer electrode material was established.Its impedance fitting error is 74.81%lower than that of the modified Randles equivalent circuit model.According to the experimental data of constant current charge and discharge,a model was built in MATLAB for charge and discharge simulation,the RMSE of the model was calculated to be 0.1424 V.The increase of the model resistance parameters will cause the simulation voltage drop to increase to varying degrees,and the increase of R_ct1 has the greatest impact on the voltage drop.（4）To test the electrochemical properties of the activated carbon with three-dimensional structure,according to its working principle and impedance data,on the basis of its pore structure with macropores,mesopores and micropores,an equivalent circuit model of the three-dimensional electric double layer electrode material was established.Its impedance fitting error is 50.71%lower than that of the modified Randles equivalent circuit model.In order to continue to verify the applicability of this model,three-dimensional hierarchical porous carbon（DCHPC）was prepared by KOH activation of carbonized chitosan,and its impedance fitting error was reduced by 89.39%,which is more applicable than activated carbon.According to the experimental data of constant current charge and discharge,a model was built in MATLAB for charge and discharge simulation,the RMSE of the model was calculated to be 0.0382 V.The increase of the model resistance parameters will cause the simulation voltage drop to increase to varying degrees,and the increase of R_ct has the greatest impact on the voltage drop.Modeling and simulation of supercapacitors is beneficial to their rational use and performance optimization,and also plays an important role in optimizing electrode materials.The establishment of models of different dimensions can more accurately show the working principles of different electrode materials,and express their impedance characteristics in a more detailed manner,which is conducive to rationally regulating the pore structure and conductivity of electrode materials,and has important practical significance and is more applicable.