First Prototype 18650 Aqueous Supercapacitors Using Graphite Coated Al Foil As Low Cost and Anti-Corrosion Current Collector

Abstract

Supercapacitors have been attached much attention for power supplies due to their high-power density and excellent cycling stability. Up to now, the study of aqueous supercapacitors is increasing continuously due to their low-cost and high safety with non-flammable. Especially, it provides a high-power density up to 10 kW kg-1 (refers to the fast charge/discharge capability) which is higher than other electrolytes such as organic and ionic liquid electrolytes.(1) However, the major problem of the aqueous electrolyte system is the corrosion of metal current collector, especially aluminium (Al) foil. Even the Al foil is a promising current collector due to its low-cost, it can be corroded easily in aqueous solutions. Additionally, the resistive oxide film is spontaneously formed on the surface of Al foil, leading to low conductivity of the electrode.(2) To address this issue, we chose the graphite material for coating on the top and bottom of Al foil surface as a hydrophobic layer to prevent a penetration of the aqueous solution into Al foil surface that can be confirmed by contact angle measurement. In addition, we further studied the electrochemical performance of the as-prepared electrode in a half-cell configuration. Overall, not only protection of corrosion but also improvement of interfacial contact between electrode material layer and current collector are resulted from graphite protective layer, leading to low internal resistance and high-rate capability of the electrode. Moreover, the corrosion suppression of the current collector can enhance the cycling stability of the electrode. Finally, we fabricated the first prototype of cylindrical aqueous supercapacitor with the standardized size of 18650 for commercial-scale using the as-modified current collector which achieves capacitance of 18.9 F/cell at 50 mA and excellent cycling stability with almost 100% over 8,000 cycles at 250 mA. KEYWORDS: Aqueous supercapacitors, anti-corrosion, hydrophobic protective layer REFERENCES C. Zhong, Y. Deng, W. Hu, J. Qiao, L. Zhang and J. Zhang, Chem. Soc. Rev., 44, 7484 (2015). 2. P. Chomkhuntod, M. Sawangphruk and K. Kongsawatvoragul, ECS Transactions, 97, 3 (2020). Figure 1