Post-hydration treatment and nano-SiO2 blocking defects in anodized aluminum foils to improve the breakdown voltage of a PEDOT:PSS solid electrolytic capacitor†

The rapid development of new energy power generation technologies has led to increasingly stringent requirements for power supply voltage stability, necessitating the adoption of solid capacitors with ultra-low equivalent series resistance (ESR) to meet the demands of applications spanning from low-voltage to high-voltage domains. The adhesiveness of the cathode poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and defects in the Al₂O₃ surface layer create discharge breakdown paths that enable the low breakdown voltage (BV) of solid capacitors. Firstly, the effects on the capacitor's performance are analyzed by studying the dynamic changes between the Al₂O₃ dielectric layer and the hydration layer produced by post-hydration treatment (PHT). The thinned Al₂O₃ layer and thickened hydration layer increase the loss and ESR of solid capacitors while avoiding the concentration of charge in a single conductive path, enhancing the leakage current and BV. Secondly, the reformed dense Al₂O₃ after PHT provides a hydration layer that blocks the defects, resulting in an improved BV of the solid capacitor without affecting the capacitance and loss. Finally, after a brief PHT, the anodized aluminum foil reforms in a nano-SiO₂-containing solution. These negatively charged nano-SiO₂ particles are effectively adsorbed onto the surface of the alumina dielectric layer, reducing the formation of conductive paths within the dielectric layer and significantly enhancing the BV of capacitors coated with PEDOT:PSS. In this study, the capacitor's BV is significantly enhanced by 120 V, offering a simple and innovative approach to improving the BV of aluminum solid electrolytic capacitors.