Phosphorous Protective Layer for Electric Double-Layer Capacitor Collector
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Solution Overview
Problem
Conventional electric double-layer capacitors degrade over time when used at high temperatures due to increased interface resistance between the polarizable electrode layer and the collector, caused by corrosion of the collector surface.
Innovation Solution
The electrode design includes a collector with a protective phosphorous layer and a conductive layer with a phosphorous compound, limiting the eluted phosphorous compound to 1.35 mg/m2 per unit surface area, which suppresses corrosion and maintains low interface resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer with carbon black and binder is formed between the collector and polarizable electrode layer to reduce interface resistance, then the adhesion strength increases and interface resistance decreases, but the collector surface corrodes at high temperatures causing degradation over time
Solution Approach 1:
A protective layer containing phosphorous is introduced as an intermediary substance between the collector and the external environment. This protective layer acts as a barrier that prevents corrosive substances from reaching and corroding the collector surface, while allowing the conductive layer to maintain its function of reducing interface resistance. The phosphorous-containing protective layer specifically suppresses corrosion at high temperatures without interfering with the electrical conductivity or adhesion properties of the conductive layer.
Solution Approach 2:
The invention changes the chemical composition parameters of the protective layer by incorporating phosphorous compounds. By controlling the presence and concentration of phosphorous in the protective layer, the corrosion resistance is enhanced. The amount of phosphorous compound is controlled so that when the collector is immersed in water, the eluted phosphorous is limited to specific amounts, ensuring optimal protection without excessive material usage.
2Object-affected harmful factors
If the collector surface is exposed without protection to maintain good conductivity and adhesion, then the interface resistance remains low, but the corrosion resistance at high temperatures deteriorates
Solution Approach 1:
The invention optimizes the phosphorous compound content in the protective layer by establishing specific quantitative limits. The amount of phosphorous compound is controlled so that when the collector is immersed in water, the eluted phosphorous is limited to not greater than 1.35 mg/m². This parameter control ensures sufficient corrosion protection while preventing excessive phosphorous elution that could adversely affect the system.
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 design enhances the high-temperature characteristics and longevity of electric double-layer capacitors by preventing corrosion and maintaining low resistance during prolonged charging and discharging cycles.
Implementation Method 1
a polarizable electrode layer that is formed above this collector and can reversibly adsorb and desorb ions
Implementation Method 2
a collector with a protective layer containing phosphorous on its surface... An amount of a phosphorous compound per unit surface area of the collector, eluted when the collector is immersed into water, is not greater than 1.35 mg/m2
Data Source
AI summary
An electrode for electric double-layer capacitor includes a collector with a protective layer containing phosphorous on its surface, and a polarizable electrode layer that is formed on this collector and can adsorb and desorb ions. An amount of a phosphorous compound per unit surface area of the collector, eluted when the collector is immersed into water, is not greater than 1.35 mg/m2 in terms of phosphorous equivalent. An electric double-layer capacitor employs this electrode for at least one of a positive electrode and a negative electrode.