Polymer Electrolyte Layering for Capacitor Cycling Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solid electrolytic capacitors face issues with capacitance stability during power cycling due to incompatibility or insufficient filling of polymer layers, leading to poor adhesion and delamination, particularly in high charge density applications.
Innovation Solution
A solid electrolytic capacitor design featuring a first solid electrolyte layer with a low glass transition temperature and a second solid electrolyte layer with a higher glass transition temperature, along with adhesion layers, to enhance ionic conductivity and improve layer adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high charge density powder is used to increase capacitance, then capacitance increases, but pore size decreases making it difficult to deposit conductive polymer on interstitial surfaces
Solution Approach 1:
The conductive polymer cathode is divided into multiple layers with different formulations. The first layer uses in-situ polymerization to deposit polymer directly on the dielectric surface, while subsequent layers use pre-formed polymer slurries. This segmentation allows each layer to serve a specific function: the first layer ensures good adhesion and surface coverage, while outer layers provide additional capacitance without requiring perfect interstitial penetration.
Solution Approach 2:
Different regions of the cathode structure are assigned different material properties. The inner layer near the dielectric uses in-situ polymerized conductive polymer for optimal adhesion and surface coverage, while outer layers use pre-formed polymer with different compositional ratios to maximize capacitance. This local differentiation of material quality resolves the conflict between achieving surface coverage and maximizing total capacitance.
2Area of stationary object
If multiple layers of conductive polymer with different formulations are used, then interstitial surface area coverage improves, but layer compatibility and adhesion deteriorate leading to delamination during power cycling
Solution Approach 1:
The glass transition temperature (Tg) parameter of the polymer layers is systematically controlled to ensure compatibility. The first layer uses a polymer with Tg below 0°C, while outer layers use polymers with Tg of at least 50°C. This parameter differentiation ensures that each layer remains mechanically stable during power cycling while maintaining good interfacial adhesion, preventing delamination despite formulation differences.
Solution Approach 2:
The cathode is constructed as a composite structure with multiple polymer layers having different compositions and properties. Each layer is designed with specific polymer-to-polyanion ratios and Tg characteristics to optimize both coverage and adhesion. The composite structure allows synergistic combination of layers with different functionalities while maintaining overall structural integrity through careful selection of interfacial compatibility parameters.
3Area of stationary object
If in-situ polymerization is used for the primary layer, then initial surface coverage is improved, but forming outer layers from pre-formed polymer slurries becomes difficult
Solution Approach 1:
The glass transition temperature parameter is used to ensure compatibility between layers formed by different methods. The in-situ polymerized first layer has Tg below 0°C, while pre-formed polymer slurries for outer layers use polymers with Tg of at least 50°C. This parameter control ensures that the phase states and mechanical properties of layers are compatible, allowing successful deposition of outer layers on the in-situ formed base layer without adhesion problems.
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 exhibits improved capacitance stability with less than 15% loss after 50,000 power cycles, maintaining performance in high charge density environments.
Implementation Method 1
the first solid electrolyte has a low Tg (glass transition temperature)
Implementation Method 2
the second solid electrolyte has a high Tg and more preferably comprises a second polymer with a high Tg
Implementation Method 3
Capacitors comprising a tantalum anode and a cathode comprising a solid electrolyte formed from conductive polymer cathodes
Data Source
AI summary
Provided is a solid electrolytic capacitor with an improve capacitance stability. The capacitor comprises an anode with a dielectric on the anode. A cathode is on the dielectric wherein the cathode comprises a first solid electrolyte layer wherein the first solid electrolyte layer preferably comprises a first polymer and has a first glass transition temperature. A second solid electrolyte layer is on the first solid electrolyte layer wherein the second solid electrolyte layer preferably comprises a second polymer and has a second glass transition temperature which is higher than the first glass transition temperature.