Electric Double Layer Capacitor Anionic Polymer Gel Electrolyte
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Solution Overview
Problem
Electric double layer capacitors with aqueous electrolytes face issues with thermal expansion leading to electrolyte leakage and reduced performance at high temperatures.
Innovation Solution
Incorporating an anionic polymer and a polyprotic acid in the aqueous electrolyte to enhance binding properties and stability, reducing electrolyte loss and maintaining electrical performance even at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aqueous electrolyte is used in electric double layer capacitor, then good electrical performance is achieved, but electrolyte leakage occurs at high temperature due to thermal expansion
Solution Approach 1:
The patent uses a composite gel electrolyte system combining polyacrylamide polymer matrix with aqueous electrolyte solution containing sulfuric acid and zinc sulfate. This composite structure provides both the electrical conductivity needed for capacitor performance and the physical containment that prevents thermal expansion leakage at high temperatures.
Solution Approach 2:
The patent modifies the physical state of the electrolyte by transforming it from a free-flowing liquid to a gel state through polymer incorporation. This parameter change in the electrolyte's physical state maintains its electrochemical functionality while eliminating the harmful thermal expansion and leakage issues associated with liquid electrolytes.
2Reliability
If aqueous electrolyte is used in electric double layer capacitor, then good electrical performance is achieved, but capacitance reduces at high temperature due to electrolyte leakage
Solution Approach 1:
The gel composite electrolyte system maintains the aqueous electrolyte's ionic conductivity for good electrical performance while the polymer matrix physically retains the electrolyte, preventing the quantity loss that would otherwise reduce capacitance at elevated temperatures.
Solution Approach 2:
By changing the electrolyte from liquid to gel state, the patent preserves the quantity of electrolyte substance at high temperatures, thereby maintaining capacitance while still achieving good electrical performance through the conductive aqueous-based gel composition.
3Reliability
If aqueous electrolyte is used in electric double layer capacitor, then good electrical performance is achieved, but equivalent series resistance increases at high temperature due to electrolyte leakage
Solution Approach 1:
The gel electrolyte composite maintains the low ESR characteristics of aqueous electrolytes through its conductive composition while the polymer network structure prevents electrolyte loss, thereby preventing the increase in equivalent series resistance that occurs with liquid electrolyte leakage at high temperatures.
Solution Approach 2:
The phase change from liquid to gel state eliminates electrolyte leakage while preserving ionic conductivity, thereby maintaining low equivalent series resistance at high temperatures while still achieving good electrical performance.
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 high capacitance and low equivalent series resistance (ESR) at temperatures above 70°C, maintaining excellent electrical properties.
Implementation Method 1
the anionic polymer serves as binding agent for the electrochemically active particles
Implementation Method 2
the electrolyte includes a polyprotic acid... capable of undergoing two or more proton dissociations
Implementation Method 3
the aqueous electrolyte tends to undergo thermal expansion when exposed to high temperature environments
Data Source
AI summary
An electric double layer capacitor that contains at least one electrochemical cell is provided. The cell contains electrodes (e.g., two electrodes) that each contain a porous matrix of electrochemically-active particles (e.g., carbon). An aqueous-based electrolyte is disposed in contact with the porous matrix. In accordance with the present invention, the electrolyte is provided with an anionic polymer that serves as binding agent for the electrochemically active particles and thus reduces electrolyte loss, especially at higher temperatures. Because the polymer is anionic in nature, it is generally hydrophilic and thus can retain its binding properties in the presence of water. The anionic nature of the polymer also allows it to remain stable in the presence of a corrosive polyprotic acid, which is employed in the electrolyte to enhance charge density. Thus, as a result of the present invention, a capacitor may be formed that is capable of exhibiting good electrical performance (e.g., high capacitance and low ESR), even at high temperatures (e.g., 70° C. and above).