Electrical Performance Enhancement of 400 V Level Aluminum Solid Electrolytic Capacitors with Interface Modulation through Intervention of PVA

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a conductive polymer dispersion, is widely used in cathodes of solid electrolytic capacitors. However, it still suffers from performance limitations when used at high frequencies, and its withstand voltage must be improved. Herein, impregnation drying introduces a polyvinyl alcohol (PVA) coating onto alumina, which regulates the interface between the PEDOT:PSS cathode and alumina. The equivalent series resistance (ESR) of the capacitor is significantly reduced, whereas the withstand voltage is slightly improved. This study demonstrates that the presence of PVA enhances the wettability of PEDOT:PSS dispersions on alumina surfaces. Changes in the infrared peak positions of the -OH and -SO₃H groups following the mixing of the PVA and PEDOT:PSS films, along with alterations in the thermal decomposition temperature, indicate the occurrence of crosslinking. Theoretical calculations demonstrate the presence of hydrogen bonds between the -OH groups in PVA and the -SO₃H groups of PEDOT:PSS. Interface modulation effectively improves capacitor performance, as the capacitance ratio of capacitors with 400 V level withstand voltages increases from 97.35% to 98.85%, and the ESR at 100 kHz is significantly reduced by ≈40%. This study provides a valuable reference for the preparation of high-performance solid electrolytic capacitors.