Conductive Cathode Foil for Low-Hydrogen Electrolytic Capacitors
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Solution Overview
Problem
Electrolytic capacitors used in medium and high voltage applications face challenges in suppressing the production of hydrogen gas, which increases with higher voltages and can lead to pressure buildup and potential damage.
Innovation Solution
The solution involves forming a conductive layer on the surface of the cathode foil and adjusting its natural immersion potential to be higher than that of a reference cathode foil, effectively shifting the potential range of the cathode reaction to favor the reduction of dissolved oxygen over hydrogen ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric oxide film layer is thinned to increase capacitance, then capacitance is improved, but hydrogen gas production increases
Solution Approach 1:
A conductive layer is introduced as an intermediary between the cathode foil and the electrolyte solution. This conductive layer serves as a mediator that facilitates electron transfer while controlling the cathode reaction potential, thereby suppressing hydrogen gas production even when the dielectric oxide film is thinned to increase capacitance.
Solution Approach 2:
The natural immersion potential of the cathode is changed by forming a conductive layer with specific electrochemical properties. This parameter change in potential shifts the cathode reaction from hydrogen ion reduction to dissolved oxygen reduction, suppressing hydrogen gas production while maintaining high capacitance through thin dielectric oxide film.
2Strength
If withstand voltage of 100 V or more is required for medium and high voltage applications, then voltage rating is improved, but hydrogen gas production increases due to enlarged surface structure
Solution Approach 1:
The conductive layer acts as an intermediary that decouples the relationship between enlarged surface area and hydrogen gas production. It allows the cathode to utilize the enlarged surface structure for high voltage capability while controlling the electrochemical reactions to favor oxygen reduction over hydrogen evolution.
Solution Approach 2:
By changing the natural immersion potential parameter through conductive layer formation, the invention enables high withstand voltage (100V or more) applications while suppressing hydrogen gas production. The potential shift ensures that even with enlarged surface area, the cathode reaction remains dominated by oxygen reduction.
3Object-generated harmful factors
If nitro compounds are added to suppress hydrogen gas production, then hydrogen gas production is reduced, but withstand voltage decreases and suppression performance drops over time
Solution Approach 1:
Instead of using nitro compounds that degrade over time, the invention employs a conductive layer that provides stable, long-lasting hydrogen gas suppression. The conductive layer is a structural component that does not consume or degrade, offering durable performance without the limitations of chemical additives.
Solution Approach 2:
The conductive layer provides self-sustaining hydrogen gas suppression through its inherent electrochemical properties. The natural immersion potential of the conductive layer automatically maintains the suppression effect without requiring external additives or periodic replenishment, unlike nitro compounds that lose effectiveness over time.
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 significantly suppresses the production of hydrogen gas, enhancing the durability of the suppression effect and maintaining low hydrogen gas production even after prolonged use.
Implementation Method 1
when current in a range of current density of leakage current of the electrolytic capacitor flows by electrochemical polarization, potential corresponding to said current is at a higher side than a natural immersion potential
Implementation Method 2
effectively shifting the potential range of the cathode reaction to favor the reduction of dissolved oxygen over hydrogen ions
Data Source
AI summary
A cathode and an electrolytic capacitor including the cathode which can suppress production of hydrogen gas are provided. The cathode of the electrolytic capacitor comprising cathode foil formed of valve action metal, and a conductive layer formed on a surface of the cathode foil. When current in a range of current density of leakage current of the electrolytic capacitor flows by electrochemical polarization, potential corresponding to said current is at a higher side than a natural immersion potential of reference cathode foil formed of the valve action metal with purity of 99.9%.