Solvothermal modification of activated carbon for enhanced electrochemical performance in screen-printed supercapacitors

Abstract

This study reports a novel method for enhancing the specific capacitance of screen-printed, activated-carbon-based supercapacitor electrodes through solvothermal modification of the active material. Commercial activated carbon (Kuraray YP-80F) is suspended in N,N-Dimethylformamide (DMF) and heat treated in a sealed autoclave at 160 °C for 12 h to modify its hydrophilicity and surface properties, eliminating the need for an additional drying retardant in the aqueous electrode ink that limits its electrochemically active surface area. Additionally, the average pore volume of the carbon material is increased by 50 % (1.22 cm3g-1to 1.83 cm3g-1) and the specific surface area by 21 % (2040 m2g−1to 2471 m2g−1), resulting in further enhanced double layer formation. Screen-printed two-electrode supercapacitors demonstrate a specific capacitance increase of ∼140 % (12 F g−1to 28 F g−1) with aqueous electrolyte, and ∼80 % (18 F g−1to 33 F g−1) with deep eutectic solvent (DES) electrolyte, compared to cells fabricated using a commercial drying retardant. Moreover, similar capacitance retention after 10,000 charge-discharge cycles (∼95 % with aqueous, ∼85 % with DES), and a 22–25 % reduction in capacitance-normalised leakage current (40 μA F−1to 30 μA F−1with aqueous, 145 μA F−1to 113 μA F−1with DES) is obtained using solvothermal treatment.