Unveiling the Adsorption-Desorption Mechanism in Phosphorus-Doped Activated Carbon for Enhanced Double-Layer Pouch-Cell Supercapacitors

Abstract

Activated carbon (AC) suffers from low energy density in the organic system of electric double-layer capacitors (EDLCs). Currently, the research spotlight for enhancing the specific capacitance of AC in EDLC is to optimize the pore size distribution and enhance the specific surface area, but the increase of porosity in turn decreases the conductivity of AC. The surface modification is an effective strategy to improve the surface properties of carbon electrodes and enhance electrochemical performance. However, little attention has been paid to the interaction between AC surface and organic electrolyte. In this work, we have developed a phosphorus doping aimed at modulation of adsorption/desorption dynamics of organic electrolytes on the AC electrode. It was found that the phosphorus-carbon bonding increases the adsorbed amounts of TEA⁺/BF₄⁻ per unit surface area, altering the charge storage mechanism and leading to improved specific capacitance. Furthermore, we fabricated a symmetrical pouch-cell supercapacitor with an energy density of 36.2 Wh kg⁻¹. The capacitance retention of 93.7 % was maintained after 30,000 cycles at a current density of 10 A g⁻¹. These findings significantly advance our understanding of the charge storage dynamics in phosphorus-doped AC and will guide the design of improved carbon-based supercapacitors.