LiMn2O4 Li-ion hybrid supercapacitors processed by nitrogen atmospheric-pressure plasma jet

LiCl–Mn(NO3)2·4H2O pastes were screen-printed on a carbon cloth substrate and furnace-calcined to convert them into LiMn2O4. The LiMn2O4 electrode was then post-processed using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ processing created oxygen vacancy defects on the electrode surface. Electrochemical tests of the Li-ion hybrid supercapacitors (Li–HSCs) were performed by cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD) in 1-M Li2SO4 aqueous solution. The results indicate that proper APPJ treatment optimizes the Li–HSCs performance, whereas excessive APPJ treatment may cause material damage. After 3-min APPJ treatment at 620 °C, the Li–HSCs exhibited a maximum areal capacitance of 87.96 mF/cm2 with capacitance retention of 124.8% after a 1000-cycle CV test.