Improvement of Electrochemical Characteristics and Study of Deterioration of Aluminum Foil in Organic Electrolytes for EDLC

The anodic behavior of aluminum (Al) foils with varying purity, capacitance, and withstand voltage in organic electrolytes was examined for EDLC. The results of cyclic voltammetry (CV) and chronoamperometry (CA) experiments showed that the electrochemical stability improves when Al foil has higher purity, lower capacitance, and higher withstand voltage. To improve the electrochemical stability of EDLC current collectors made of low-purity foil (99.4% Al foil), the foil was modified by chemical etching to reduce its capacitance to $60{\mu}F/cm^2$ and forming to have withstand a voltage of 3 Vf. EDLC cells using the modified Al foil as a current collector were made to 2.7 V with 360 F, and a constant voltage load test was subsequently performed for 2500 hours at high temperature under a rated voltage of 2.7 V. The reliability and stability of the EDLC cell improved when the modified Al foil was used as a current collector. To understand the deterioration process of the Al current collector, standard cells made of conventional Al foil under a constant voltage load test were disassembled, and the surface changes of the foil were measured every 500 hours. The Al foil became increasingly corroded, causing the adhesion between the AC coating layer and the Al foil to weaken, and it was confirmed that partial AC coating layer peeling occurred.