Activated Carbon‐Based Supercapacitors with High Gravimetric and Volumetric Capacitance at Commercial‐Level Mass Loading

Activated carbons (ACs) are derived from cornhusk via a simple technique consisting of hydrothermal carbonization and following KOH activation, with porous structures and morphology of the ACs controlled by adjusting the amount of KOH for the activation. As the main active materials of the electrode for supercapacitors (SCs), both the porosity and morphology exhibit significant influence in the compaction density of the electrode. The ACs activated with a KOH/biochar ratio of 3:1 not only provide a high surface area of 3024 m 2 g −1 but also guarantee a high compaction density of 11.6 mg cm −2 for a 200 μm‐thick electrode, leading to high performances for both gravimetric and volumetric capacitance. Moreover, the morphology of a thin sheet‐like interconnected network benefits the densely compact nature of the ACs in the electrode. Concerning the practical application, the effect of electrode thickness on the electrochemical performance is examined to optimize the electrode with commercial‐level mass loading with organic electrolyte, which is of ≈344 F g −1 in gravimetric capacitance and 210 F cm −3 in volumetric capacitance as well as excellent capacitance retention over 90% after 5000 galvanostatic charge–discharge cycles. In addition, good electrochemical performances of the optimized electrode with commercial‐level mass loading are over a broad range of work temperature.