Phosphorus Compound Electrode for EDLC Interface Resistance
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Solution Overview
Problem
Electric double layer capacitors experience increased resistance due to the formation of a passive film of aluminum fluoride between the current collector and polarizable electrode layers, caused by fluorine ions from the electrolyte solution reacting with the aluminum current collector, leading to reduced reliability over time.
Innovation Solution
Incorporating a phosphorus compound into the polarizable electrode layers, which are stable to fluorine ions, to prevent chemical reactions at the interface between the current collector and the electrode layers, thereby suppressing the formation of a passive film and maintaining low interface resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-containing anions are used as electrolyte solute to reduce electrolysis deterioration, then reliability against electrolysis is improved, but interface resistance increases due to passive film formation
Solution Approach 1:
A phosphorus compound coating layer is introduced as an intermediary between the aluminum current collector and the fluorine-containing electrolyte solution. This coating layer acts as a protective barrier that prevents direct contact and chemical reaction between fluorine ions and aluminum, thereby eliminating passive film formation while allowing the electrolyte to perform its electrolysis-resistant function.
Solution Approach 2:
The invention converts the harmful effect of fluorine ions (which cause passive film formation and increased resistance) into a beneficial outcome by using them in the electrolyte solution while protecting the current collector. The phosphorus compound coating enables the electrolyte to maintain its electrolysis protection function while the fluorine ions are prevented from damaging the aluminum surface.
2Power
If aluminum current collector is used for the positive electrode, then electrical conductivity is improved, but chemical stability deteriorates due to reaction with fluorine ions
Solution Approach 1:
The phosphorus compound coating serves as a protective intermediary layer that preserves the aluminum current collector's electrical conductivity while shielding it from chemical reactions with fluorine ions. This coating allows the aluminum to maintain its excellent conductive properties without sacrificing chemical stability in the fluorine-containing electrolyte environment.
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 use of phosphorus compounds in the electrode layers stabilizes the surface of the current collector, preventing fluorine ion reactions and maintaining low interface resistance, resulting in an electric double layer capacitor with improved long-term reliability and reduced property degradation.
Implementation Method 1
The first polarizable electrode layer contains a phosphorus compound, which is stable to fluorine ions, thereby stabilizing the surface of the first current collector. The phosphorus compound functions to prevent the chemical reaction between the first current collector and the fluorine ions at the interface
Data Source
AI summary
An electric double layer capacitor includes a positive electrode, a negative electrode which faces the positive electrode and is isolated therefrom, and an electrolyte solution. The positive electrode includes a first current collector of a metal foil and a first polarizable electrode layer on the first current collector, the first polarizable electrode layer containing a phosphorus compound. The negative electrode includes a second current collector of a metal foil and a second polarizable electrode layer on the second current collector. The electrolyte solution, with which the first and second polarizable electrode layers are impregnated, has fluorine-containing anions as an electrolyte solute.