Two-Layer Polymer Electrolyte in Wound Capacitors for Leakage and ESR
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Solution Overview
Problem
Existing electrolytic capacitors face challenges in simultaneously suppressing both leakage current and equivalent series resistance (ESR) increases, particularly when using liquid components and conductive polymer layers as electrolytes.
Innovation Solution
The electrolytic capacitor design includes an anode foil with a porous portion covered by a dielectric layer, a cathode foil, a separator with fiber material, and two conductive polymer layers with differing electrical conductivities, where a first conductive polymer layer with lower conductivity covers the dielectric layer and defects, while a second conductive polymer layer with higher conductivity forms a conductive path between the anode and cathode foils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single conductive polymer layer is used, then the ESR can be reduced, but the leakage current increases due to insufficient coverage at defects
Solution Approach 1:
The conductive polymer electrolyte is divided into two distinct layers: a first conductive polymer layer with lower conductivity that provides defect coverage and leakage suppression, and a second conductive polymer layer with higher conductivity that ensures low ESR. This segmentation allows each layer to perform its specialized function optimally.
Solution Approach 2:
Different regions of the conductive polymer electrolyte are assigned different conductivity characteristics. The first layer near the dielectric interface has lower conductivity for leakage suppression, while the second layer has higher conductivity for ESR reduction. This local quality differentiation resolves the contradiction between leakage current suppression and ESR control.
2Reliability
If the conductive polymer layer is made thinner to reduce ESR, then the ESR decreases, but the coverage of defects on the dielectric layer becomes insufficient, increasing leakage current
Solution Approach 1:
The conductive polymer electrolyte is segmented into two layers with different thicknesses and conductivities. The first layer is optimized for defect coverage thickness to suppress leakage, while the second layer is optimized for conductivity to reduce ESR, resolving the thickness-related contradiction.
Solution Approach 2:
The conductive polymer electrolyte uses a composite structure of two different conductive polymer materials with distinct conductivity values. This composite approach allows simultaneous optimization of leakage suppression (first layer) and ESR reduction (second layer) without compromising either function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces leakage current and ESR by ensuring a sufficient conductive path while minimizing leakage at defects, thereby enhancing overall capacitor performance.
Implementation Method 1
the first conductive polymer layer covers at least a portion of a surface of the dielectric layer in the porous portion
Implementation Method 2
a second conductive polymer layer with higher conductivity forms a conductive path between the anode and cathode foils
Implementation Method 3
the anode foil includes a porous portion on which at least a portion of a surface is covered with a dielectric layer
Data Source
AI summary
An electrolytic capacitor includes a capacitor element and a liquid component, wherein the capacitor element includes an anode foil, a cathode foil, a separator, and first and second conductive polymer layers, the anode foil, the cathode foil, and the separator are wound in a longitudinal direction of the elongated shapes to form a wound body, the anode foil includes a porous portion in which a surface is covered with a dielectric layer, the separator contains a fiber material, the first conductive polymer layer covers a surface of the dielectric layer in the porous portion, a surface of the cathode foil, and a surface of the fiber material in the separator, the second conductive polymer layer covers a surface of the first conductive polymer layer, the first conductive polymer layer and the second conductive polymer layer contain a first conductive polymer and a second conductive polymer, respectively.