Pore-size effect of activated carbons on the electrochemical performances of symmetric supercapacitors under compression

Abstract

Applying proper compression during the assembling or operating of the activated‑carbon (AC)-based supercapacitors (SCs) is an effective way of optimizing the energy storage performances, of which the effects may vary dramatically with the porous structures of the ACs. This work converts soybean dreg into ACs with tailorable porous structures via a facile KOH activation. Specific electrochemical performances of the ACs under compression are examined and analyzed for different average pore sizes. With the increase in the compressive stress from 0.25 to 4 MPa, the electrochemical performances of the AC-based SCs are improved, with volumetric capacitance, capacitance retention increased and resistance and self-discharge rate decreased. Furthermore, by analyzing the dependence of specific electrochemical performances on the compressive stress, the compression-responsivity is found to be more profound for the ACs with smaller average pore size. The ACs with an average pore size of 1.38 nm exhibit the most favorable comprehensive electrochemical performances under relatively high compressive stresses. The ACs with an average pore size of 2.24 nm possess balanced energy storage performances for both low and high compressions. Such results may guide the optimization of the SCs assembling and selection of ACs with suitable porous structures for certain application conditions.