Hybrid Electrolytic Capacitor Cathode for Low ESR at High Frequency
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Solution Overview
Problem
Hybrid electrolytic capacitors with inorganic conductive layers on valve metal foils exhibit low capacitance at high frequencies and high ESR values, especially after high-temperature endurance testing, due to high interface resistance and limited adhesion between the solid electrolyte and inorganic conductive layers.
Innovation Solution
A hybrid electrolytic capacitor design featuring a cathode with a dense organic conductive polymer layer formed via electrolytic polymerization on an inorganic conductive layer, which reduces interface resistance and enhances adhesion, allowing for improved capacitance and ESR performance across various frequencies and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an inorganic conductive layer is formed on the cathode to increase capacitance, then capacitance at low frequency is improved, but interface resistance increases and high-frequency characteristics deteriorate
Solution Approach 1:
The patent applies a composite structure consisting of an inorganic conductive layer (such as titanium carbide or carbon) combined with an organic conductive polymer layer. The inorganic layer provides high capacitance at low frequencies, while the organic polymer layer reduces interface resistance and improves high-frequency characteristics. This composite approach allows the capacitor to achieve both high capacitance and good high-frequency performance simultaneously.
2Loss of energy
If the inorganic conductive layer is made thicker to reduce ESR, then ESR decreases, but adhesion to the solid electrolyte deteriorates
Solution Approach 1:
The organic conductive polymer layer serves as an intermediate layer between the inorganic conductive layer and the solid electrolyte. This intermediate layer improves adhesion by providing a transition zone that bonds well with both the inorganic layer below and the solid electrolyte above, allowing the inorganic layer to be sufficiently thick for low ESR while maintaining strong adhesion through the polymer interface.
Solution Approach 2:
The organic conductive polymer acts as an intermediary layer that mediates the interface between the inorganic conductive layer and the solid electrolyte. It provides good adhesion to both materials while maintaining electrical conductivity, thus reducing ESR without compromising bond strength.
3Ease of manufacture
If chemical polymerization is used to form the conductive polymer layer, then manufacturing simplicity is improved, but leakage current increases
Solution Approach 1:
The patent replaces chemical polymerization with electrolytic polymerization. Instead of using chemical reagents that can leave residues and increase leakage current, the organic conductive polymer is formed electrochemically by applying a voltage to reduce the monomer (such as EDOT) directly on the cathode surface. This electrochemical approach produces a cleaner polymer layer with fewer impurities and lower leakage current.
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 capacitor achieves high capacitance, low ESR, excellent high-frequency characteristics, and excellent high-temperature durability by extending the region where cathode oxide film resistance dominates over interface resistance, even at high frequencies, and maintaining these properties after severe thermal testing.
Implementation Method 1
forming an organic conductive layer having a conductive polymer on a surface of the inorganic conductive layer via electrolytic polymerization of a monomer having a n-conjugated double bond
Implementation Method 2
a composite electrolyte layer comprising a solid electrolyte layer having conductive polymer particles and an electrolytic solution impregnated in gaps in the solid electrolyte layer
Data Source
AI summary
Provided is a hybrid electrolytic capacitor having large capacitance, low ESR, and superior high-frequency characteristics and high-temperature endurance. The hybrid electrolytic capacitor 1 is provided with: a cathode 10 having a cathode substrate 11 made of a valve metal, an oxide layer 12 provided on a surface of the cathode substrate 11, an inorganic conductive layer 13 provided on a surface of the oxide layer 12 and including an inorganic conductive material, and an organic conductive layer 14 provided on a surface of the inorganic conductive layer 13 and including a conductive polymer; an anode 20 having an anode substrate 21 made of a valve metal and a dielectric layer 22 provided on a surface of the anode substrate 21; and a composite electrolyte layer 30 having a solid electrolyte layer 31 containing conductive polymer particles 31a which is provided between and in contact with the organic conductive layer 14 of the cathode 10 and the dielectric layer 22 of the anode 20, and an electrolytic solution 32 filled between the conductive polymer particles 31a in the solid electrolyte layer 31.