Ultra-Fast Electrochemical Expansion for Rapid Enhancement of Graphite Paper Electrode

Graphite paper is widely used in energy storage systems such as batteries and supercapacitors due to its availability, cost, and excellent chemical and thermal stability. However, its hydrophobic surface and dense structure limit electrolytic ion diffusion in aqueous supercapacitors, reducing electrochemical performance. To address these issues, graphite paper was treated with mild acid solution and electrochemically oxidized for varying durations to enhance its properties for high-performance supercapacitors. Acid treatment not only expanded the graphite but also functionalized its surface, making it more hydrophilic, as confirmed by FTIR and contact angle measurements. This modification improved the electrode's electrochemical performance by facilitating better ion diffusion and insertion, resulting in increased specific capacitance. After 5 min of treatment, the graphite layers enlarged from 35 to 469 μm, resulting in an enhanced specific capacitance of 219 F g^-1 at 10 mV s^-1 but poor cycling stability with 80% capacitance retention after 500 cycles. In contrast, the 3 min treatment achieved a specific capacitance of 113 F g^-1 with excellent cycling stability without significant capacitance fading. These results highlight the importance of optimizing both the structural and chemical properties of graphite for achieving high performance and long cycling stability.