Solid Electrolytic Capacitor Cathode Layer for Low ESR Stability
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Solution Overview
Problem
Existing electrolytic capacitors with solid electrolytes face issues of increased equivalent series resistance (ESR) due to air permeation, particularly under high-temperature conditions, leading to conductive polymer deterioration.
Innovation Solution
Incorporating a cathode lead-out layer containing a carbon material and a first polymer with acid groups, such as sulfone or carboxyl groups, enhances adhesion and forms a gas barrier, reducing air permeation and maintaining low ESR even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon layer is used as the cathode lead-out layer, then electrical conductivity is improved, but adhesion to the solid electrolyte layer is insufficient and gas barrier performance is poor
Solution Approach 1:
The cathode lead-out layer is constructed as a composite material containing carbon particles (5-50 mass%), binder resin (30-60 mass%), and inorganic filler (10-40 mass%). This composite structure combines the electrical conductivity of carbon with the adhesion properties of binder resin and the gas barrier properties of inorganic filler, resolving the contradiction between conductivity and adhesion/gas barrier performance
Solution Approach 2:
The patent applies different materials with specific functions in different regions of the cathode lead-out layer. The binder resin provides adhesion at the interface with the solid electrolyte layer, while the inorganic filler creates a tortuous path for gas permeation, and carbon particles provide conductivity throughout the layer. Each component is optimized for its specific local function
2Temperature
If the electrolytic capacitor operates at high temperature, then power delivery capability is improved, but ESR increases due to conductive polymer deterioration
Solution Approach 1:
The cathode lead-out layer is designed in advance to prevent air permeation before it can reach the solid electrolyte layer and cause conductive polymer deterioration. The inorganic filler creates a gas barrier that blocks oxygen and moisture, preventing the chemical reactions that would increase ESR at high temperatures. This preliminary protection maintains ESR stability even when operating at elevated temperatures
Solution Approach 2:
The composite structure with inorganic filler (such as alumina, silica, or boehmite) creates a tortuous path for gas permeation, effectively blocking air from reaching the solid electrolyte layer. This composite material approach maintains low ESR at high temperatures by preventing the oxidative degradation of the conductive polymer
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
The enhanced adhesion between the carbon material and conductive polymer suppresses the increase in ESR, providing improved performance and stability under high-temperature conditions.
Implementation Method 1
the cathode lead-out layer contains a carbon material and a first polymer including an acid group... forms a gas barrier, reducing air permeation
Implementation Method 2
Incorporating a cathode lead-out layer containing a carbon material and a first polymer with acid groups, such as sulfone or carboxyl groups, enhances adhesion
Data Source
AI summary
An electrolytic capacitor includes a capacitor element. The capacitor element includes an anode body, a dielectric layer that covers at least a part of the anode body, a solid electrolyte layer that covers at least a part of the dielectric layer, and a cathode lead-out layer that covers a part of the solid electrolyte layer. The cathode lead-out layer contains a carbon material and a first polymer including an acid group. The acid group includes at least one selected from the group consisting of a sulfone group, a carboxyl group, and a derivative of the sulfone group or the carboxyl group.