Electrode Structural Changes And Their Effects On Capacitance Performance During Preparation And Charge-Discharge Processes

Due to the good pore structure and stable physical and chemical properties,it has developed in micro hole,hole,big hole,such as pore structure,up to hundreds or even thousands of square meters per gram than surface and good electrical conductivity,thus became a kind of ideal electric double layer of super capacitor electrode materials.The specific surface area and pore structure of the electrochemical performance of the two key factors.However,many steps will affect these two factors in the process from the preparation of activated carbon to the electrode.In particular,the pore structure of electrodes is greatly affected by the addition of conductive agents and adhesives,and the dynamic electrochemical properties displayed during charging and discharging are closely related to the changes in pore structure.The pore structure and specific surface area of the electrode determine its capacitance,but these parameters will change in the process of electrode preparation and affect the capacitance performance.In this study,after considering the electrode material is made into film,is pressed on the nickel foam.We first discussed the pressure for electrode pore structure influence.Found that the pressure will reduce the pile hole between the electrode material particles.After,we explored the PTFE as a binder for electrode pore structure.The influence of the mass ratio,the greater the electrodes for the destruction of the pore structure.After that,we respectively explored the two common conductive material(carbon black and graphene)for the influence of electrode pore structure.The ratio of activated carbon,conductive agent and binder was optimized.The optimal ratio was obtained(93:3:3).The electrode capacitance was increased by 17%,with good cycling stability.In conclusion,these findings have important application prospects for further optimizing the electrode preparation process and improving the performance of ultracapacitor in industrial applications.In order to further explore the influence of the changes in the pore structure of the electrode during the charging and discharging cycle on the electrochemical properties of the electrode,we characterized the pore structure before and after the charging and discharging of the electrode,and found that the pore structure blocked before was reopened.In the Nyquist plots of electrochemical ac impedance spectra,the charge transfer resistance(Rct)increases with the number of charge and discharge cycles,which indicates that the specific surface increases and the conductivity decreases as the electrode expands.In order to inhibit the increase of Rct due to the decrease of conductivity,we found that the flexible graphene has better cycling performance.In addition,the electrochemical properties of graphene-activated carbon-black were further improved by replacing physical crosslinking with chemically crosslinked graphene-activated carbon-carbon black to form a more stable conductive network.