Preparation of Al2O3/TiO2 Composite film with High Specific Capacitance by Surface Self-assembly Method

For anodized aluminum, the enhancement of the specific capacitance foils by increasing dielectric constant is one of the most common methods to meet the requirements of miniaturization and lightweight of aluminum electrolytic capacitors. In this study, surface self-assembly method was used to introduce sulfonic acid group to graft the surface of aluminum foil for changing its electrical properties. Electrostatic repulsion between surface of aluminum foil and colloidal particles of titanium dioxide was changed to electrostatic forces due to the existence of sulfonic acid group, which dramatically enhanced the deposition of titanium dioxide on the surface of the aluminum foil. After heat treatment and anodic oxidation of aluminum foil, the Al2O3/TiO2 compounds with high dielectric constant on the surface of aluminum foil were prepared successfully. Comparing with those without TiO2 coating, the content of Ti on the surface of anodized aluminum foil prepared by surface self-assembly method increased by 30 times while the specific capacitance of anodized aluminum foil was enhanced by 44.26% at the withstanding voltage of 400 V. Therefore, anodized aluminum foil with a high specific capacitance prepared by above method exhibits great potential in commercial application of aluminum electrolytic capacitor in the future.