Electrochemical performance of symmetric supercapacitors under compression: Size effects of activated carbon spheres

The significant influences of the external stress in the electrochemical performances of the supercapacitors require the optimization of the electrode materials with reasonable morphology. In this work, activated carbon spheres (ACSs) of different sizes are prepared from hydrothermal processing of glucose aqueous solution, pre-carbonization, and KOH activation. The energy storage performance of ACS-based supercapacitors (SCs) under compression is analyzed. Increasing the compressive stress from 1 MPa to 8 MPa promotes the specific capacitance of the ACS-based SCs, which achieves 374 F/g at 0.5 A/g for the ACSs with the smallest diameter of 1.48 μm. Applying higher compressive stress also reduces IR drop and the self-discharge rate. The compression is found to have more significant positive effects on the electrochemical properties of the ACSs with larger sizes. The understanding of the morphological effect of the electrode materials on the electrochemical properties under compressive stress can help design and select appropriate electrode materials for supercapacitors applied under certain stresses.