Hybrid Capacitor Polymer Pre-Coating for Large Low-ESR Windings
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Solution Overview
Problem
Existing methods for manufacturing hybrid capacitors are limited to small sizes and unsuitable for large axial capacitors due to issues with polymer impregnation and diffusion, leading to incomplete conductive pathways and high equivalent series resistance (ESR).
Innovation Solution
The method involves pre-treating asymmetrical anodes and cathodes with conductive polymer coatings before winding, followed by impregnating with liquid electrolyte, allowing for improved polymer distribution and eliminating size restrictions, resulting in enhanced capacitance and reduced ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pre-formed conductive polymer slurry is used to impregnate the interstitial spaces of the capacitor winding, then the manufacturing complexity is reduced compared to in-situ polymerization, but the diffusion rate and efficiency are limited, restricting the capacitor size to small dimensions only
Solution Approach 1:
The conductive polymer is applied to the separator and electrode surfaces before winding the capacitor structure. This preliminary coating ensures that conductive pathways are established on all surfaces prior to assembly, allowing the polymer to be distributed throughout the interstitial spaces without relying on slow diffusion processes after winding. This enables large capacitor sizes to be achieved while maintaining complete conductive coverage.
2Manufacturing precision
If the separator filters polymeric particles and counterions during diffusion, then the conductive polymer purity is improved, but the effective diffusion is limited, restricting the maximum capacitor length and size
Solution Approach 1:
The conductive polymer coating is applied to the separator and electrodes before winding, ensuring that even distant regions of long capacitors receive adequate polymer coverage. This eliminates the diffusion limitation that would otherwise restrict capacitor length, as the polymer is already in place rather than needing to diffuse through the entire structure after assembly.
Solution Approach 2:
The separator is designed with controlled porosity to allow liquid electrolyte penetration while maintaining structural integrity. The porous structure enables the liquid electrolyte to reach all regions of the capacitor, working in conjunction with the pre-applied conductive polymer to ensure complete conductive pathways throughout the entire capacitor length.
3Ease of manufacture
If the bottom tab is dipped in the polymer precursor or slurry during axial capacitor manufacturing, then the tab becomes coated with conductive polymer, but this causes processing problems and prevents subsequent voltage application for polymer formation or healing
Solution Approach 1:
The conductive polymer is applied to the separator and electrode surfaces before winding and assembly, rather than dipping the completed axial capacitor tabs in polymer slurry. This preliminary application ensures that conductive pathways are established without coating the tabs, allowing subsequent voltage application for polymer formation or healing to proceed without interference.
4Manufacturing precision
If in-situ polymerization of monomer is used to form conductive polymer in the capacitor, then complete polymer coverage can be achieved, but the process is complex and results in product contamination by monomer and oxidizer
Solution Approach 1:
The conductive polymer is pre-formed and applied to the separator and electrodes before capacitor assembly, eliminating the need for in-situ polymerization within the sealed capacitor. This approach achieves complete conductive coverage without the contamination risks associated with monomer and oxidizer residues from in-situ polymerization processes.
Solution Approach 2:
Instead of performing the complex in-situ polymerization process within the capacitor, the conductive polymer structure is created separately in advance and then transferred to the capacitor components. This copying approach maintains the benefits of complete polymer coverage while avoiding the harmful contamination effects of in-situ polymerization.
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 approach enables the production of capacitors with high capacitance and low ESR, suitable for various designs including axial capacitors, with improved volumetric efficiency and reproducibility, and allows for larger sizes and higher voltages.
Implementation Method 1
adding the solution onto the working element wherein the conductive polymer migrates, or diffuses, into the interstitial spaces
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
An improved capacitor is described herein. The capacitor comprises a working element wherein the working element comprises an anode comprising a dielectric thereon and an anode conductive polymer layer on the dielectric. The capacitor also includes a cathode comprising a cathode conductive polymer layer and a conductive separator between the anode and said cathode. An anode lead is in electrical contact with the anode and a cathode lead is in electrical contact with the cathode.