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.