Surface Modification of Al Foils for Aluminum Electrolytic Capacitor

Miniaturization and light weight of aluminum electrolytic capacitor can be achieved via the enhancement in the specific capacitance of anodized aluminum foils resulted from the introduction of compounds with high permittivity into dielectric layer. However, the electrostatic repulsion between the compounds and aluminum substrates hinders this introduction of the compounds, leading to a limited improvement in the specific capacitance. In this work, a novel strategy has been developed to promote the deposition of TiO₂ on the surface of aluminum foils by surface modification with polyvinyl alcohol, which sharply decreases the electrostatic repulsion and dramatically increases the mass of deposited TiO₂. The evolution of composition and morphology during the process are studied and the capacitor performance of aluminum foils with various treatments is investigated. Interestingly, after surface modification, a specific capacitance of 131.5 µF cm⁻² under the withstanding voltage of 21.2 V is obtained, and there is about 60% enhancement in the specific capacitance compared with those without TiO₂, and about 30% enhancement compared with those without surface modification, respectively. The specific capacitance obtained is the highest one for aluminum electrolytic capacitor reported to date. These outstanding performances exhibit great potential of this strategy for commercial application on aluminum electrolytic capacitor.