Conductive Cathode Layer for Low-Hydrogen Electrolytic Capacitors
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Solution Overview
Problem
Electrolytic capacitors used in medium and high voltages face increased hydrogen gas production due to anode reactions, which can lead to pressure buildup and potential casing expansion, and existing methods to suppress hydrogen gas, such as using nitro compounds, either reduce capacitor voltage or lose effectiveness over time.
Innovation Solution
A cathode design for electrolytic capacitors that includes a conductive layer on the cathode foil, adjusting its natural immersion potential to a higher level than the reference cathode foil, thereby suppressing hydrogen gas production by favoring cathode reactions that reduce 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 adjusts the natural immersion potential of the cathode to a higher level, which suppresses hydrogen gas production while maintaining the thinned dielectric oxide film structure for high capacitance.
Solution Approach 2:
The natural immersion potential of the cathode is changed by adding a conductive layer, shifting it to a higher level. This parameter change suppresses the cathode reaction that produces hydrogen gas, allowing the use of thinned dielectric oxide films without excessive hydrogen generation.
2Object-generated harmful factors
If nitro compounds are added to suppress hydrogen gas, then hydrogen gas production is reduced, but capacitor voltage decreases
Solution Approach 1:
A conductive layer is used as an intermediary to adjust the cathode's natural immersion potential, replacing the need for nitro compounds. This approach suppresses hydrogen gas production without the voltage-reducing side effects of nitro compound additives.
3Object-generated harmful factors
If nitro compounds are used to suppress hydrogen gas, then hydrogen gas production is reduced, but suppression effectiveness decreases over time
Solution Approach 1:
The conductive layer on the cathode provides continuous, self-sustaining suppression of hydrogen gas production by maintaining a higher natural immersion potential. Unlike nitro compounds that are consumed over time, the conductive layer structure permanently establishes the desired potential condition without degradation.
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
Effectively suppresses hydrogen gas production, maintaining capacitor integrity and voltage performance by dominating cathode reactions that reduce dissolved oxygen, even in the presence or absence of nitro compounds.
Implementation Method 1
a cathode reaction expressed by the following chemical formula (2), in which electrons produced in the anode reaction are received and hydrogen ions are reduced, occurs at the cathode-foil side
Implementation Method 2
When current in a range of current density of the leakage current of the electrolytic capacitor flows by electrochemical polarization, if the electrolyte solution includes a nitro compound, potential corresponding to said current may be at the higher side than the natural immersion potential of the reference cathode foil by 0.15 V or more
Data Source
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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 %.