Ultrafast Fabrication of H(2)SO(4), LiCl, and Li(2)SO(4) Gel Electrolyte Supercapacitors with Reduced Graphene Oxide (rGO)-LiMnO(x) Electrodes Processed Using Atmospheric-Pressure Plasma Jet

Pastes containing reduced graphene oxide (rGO) and LiCl-Mn(NO(3))(2)·4H(2)O are screen-printed on a carbon cloth substrate and then calcined using a nitrogen atmospheric-pressure plasma jet (APPJ) for conversion into rGO-LiMnO(x) nanocomposites. The APPJ processing time is within 300 s. RGO-LiMnO(x) on carbon cloth is used to sandwich H(2)SO(4), LiCl, or Li(2)SO(4) gel electrolytes to form hybrid supercapacitors (HSCs). The areal capacitance, energy density, and cycling stability of the HSCs are evaluated using electrochemical measurement. The HSC utilizing the Li(2)SO(4) gel electrolyte exhibits enhanced electrode–electrolyte interface reactions and increased effective surface area due to its high pseudocapacitance (PC) ratio and lithium ion migration rate. As a result, it demonstrates the highest areal capacitance and energy density. The coupling of charges generated by embedded lithium ions with the electric double-layer capacitance (EDLC) further contributed to the significant overall capacitance enhancement. Conversely, the HSC with the H(2)SO(4) gel electrolyte exhibits better cycling stability. Our findings shed light on the interplay between gel electrolytes and electrode materials, offering insights into the design and optimization of high-performance HSCs.