Study On In-situ Synthesis And Mechanical Property Of PEDOT Cathode Materials For Solid Tantalum Electrolytic Capacitors

High stability,excellent reliability,and high volumetric efficiency bring solid tantalum electrolytic capacitors?STEC?into broad applications,such as aerospace,military,and medical.However,for conventional STEC,the low conductivity of MnO₂ cathode film can cause high equivalent series resistance?ESR?and limit its application in high frequency.Conductive polymer poly?3,4-ethylenedioxythiophene??PEDOT?films have been successfully applied in sensors,photovoltaics,and OLED because of its high conductivity and good thermal stability.In this study,the aim is to replace MnO₂ with PEDOT films in STEC to lower ESR and improve capacitance-frequency characteristic.Firstly,under the instruction of in-situ polymerization theories,highly conductive PEDOT films were prepared by using orthogonal experimental design method.The results show that the conductivity of PEDOT is up to 51.3 S/cm when the weight ratio of oxidizer/EDOT is 8:1 and the concentration of methanol solvent is 80%by weight at 60°C.Moreover,the conductivity of PEDOT films can be increased to 55.7 S/cm and the pot life of premixed solutions can be significantly increased to 30 min by the addition of 1.5 wt%imidazole.Secondly,due to the porous structure of tantalum pellet,one homemade vacuum system is used to make premixed solutions penetrate deep into the pores to gain the full capacitance extraction.As a result,the whole dielectric surface is completely covered with the homogeneous PEDOT films.Furthermore,vacuum atmosphere is also responsible for the low dissipation and leakage current?LC?of STEC due to the efficient cleaning.Finally,the mechanical property of PEDOT cathode films and the LC of STEC are systematically studied.It is observed that the PEDOT films tend to crack after cleaning and drying.In this paper,this problem was solved by adding multi-walled carbon nanotube?MWCNTs?into the premixed solutions.The relatively high LC is a main challenge faced by polymer tantalum capacitors.This study focuses on the effects of defects in dielectric on LC and simulates the electric field by using ANSYS to provide data support for the analysis of LC.Based on the above analysis,an internal separation layer technique is proposed and carried on by depositing a titania?TiO₂?dielectric on Ta₂O₅ film.The results demonstrate that the additional dielectric layer on top of the Ta₂O₅ film can suppress LC effectively by covering defect spots.