Effects of plasma on electrochemical performance of carbon cloth-based supercapacitor

In this work, the surface of carbon cloth is treated by plasma jet to improve its hydrophilicity. The symmetrical carbon cloth-based supercapacitor is assembled with the carbon cloth treated by plasma as the active electrodes and sodium chloride solution as the electrolyte. With the discharge time (1 min, 2 min, 3 min) and working gas types (argon, air, helium) of plasma as variables, the effects of different plasma on the hydrophilicity of carbon cloth are observed, and the changes of the electrochemical properties of the supercapacitors with single or double carbon cloth electrodes treated by different plasma are studied. The contact angle test results show that the plasma of different working gases can weaken the hydrophobicity of carbon cloth, and the helium plasma can make the carbon cloth change from hydrophobicity to hydrophilicity. The electric capacity calculated by cyclic voltammetry shows that plasma can increase the electric capacity of carbon cloth-based supercapacitors. The electric capacity of carbon cloth-based supercapacitors with two carbon cloth electrodes treated by plasma is larger than that of single carbon cloth electrode treated by plasma. The argon and helium plasma with longer discharge time can significantly improve the electric capacity of carbon cloth-based supercapacitors. The galvanostatic charge-discharge curve shows that different working gases of plasma can make carbon cloth-based supercapacitors obtain pseudocapacitance, increase the charge-discharge time and electric capacity. From the AC impedance spectrum, it can be concluded that the plasma of any kind of working gas can reduce the impedance and charge transfer resistance of the carbon cloth-based supercapacitor. The longer plasma discharge time lead to the smaller impedance, and the impedance of the supercapacitor with both carbon cloth electrodes treated by plasma is smaller.