Cathode Foil Potential Control to Suppress Capacitor Hydrogen Gas
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Solution Overview
Problem
Electrolytic capacitors used in medium and high voltage applications face challenges in suppressing hydrogen gas production, which can lead to increased internal pressure and potential casing expansion due to the thinning of the dielectric oxide film, limiting their performance and reliability, especially at voltages of 160 V or more.
Innovation Solution
A cathode for electrolytic capacitors is designed with a conductive layer on the cathode foil, adjusting its natural immersion potential to be higher than that of a reference cathode, thereby shifting the cathode reaction to reduce dissolved oxygen rather than hydrogen ions, effectively suppressing hydrogen gas production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the dielectric oxide film layer is thinned to increase capacitance, then the capacitance increases, but hydrogen gas production increases significantly
Solution Approach 1:
A conductive layer is introduced as an intermediary between the cathode foil and the electrolyte solution. This conductive layer modifies the electrochemical environment at the cathode surface, suppressing the hydrogen evolution reaction while maintaining electrical conductivity. The conductive layer acts as a mediator that changes the reaction pathway, reducing hydrogen gas production without compromising capacitance.
Solution Approach 2:
The natural immersion potential of the cathode is changed by forming a conductive layer on the cathode foil surface. This parameter change shifts the electrochemical window, making the hydrogen evolution reaction less favorable. By controlling the potential parameter through the conductive layer, hydrogen gas production is suppressed while capacitance is maintained.
2Stress or pressure
If the dielectric oxide film layer is thinned for medium and high voltage applications, then the voltage rating increases, but hydrogen gas production increases
Solution Approach 1:
The conductive layer serves as an intermediary that decouples the relationship between thin dielectric film and hydrogen evolution. It modifies the cathode-electrolyte interface to suppress hydrogen evolution, allowing thin dielectric films to be used for high voltage applications without the associated hydrogen gas production problem.
Solution Approach 2:
By changing the natural immersion potential parameter through the conductive layer, the electrochemical stability window is extended. This allows the capacitor to operate at higher voltages with thin dielectric films while suppressing the harmful hydrogen evolution reaction that would normally occur under these conditions.
3Object-generated harmful factors
If nitro compounds are added to suppress hydrogen gas, then hydrogen gas production decreases, but withstand voltage decreases
Solution Approach 1:
The harmful function of nitro compounds (hydrogen suppression) is extracted and achieved through a different mechanism - the conductive layer on the cathode. This eliminates the need to add nitro compounds to the electrolyte, thereby preserving the high withstand voltage characteristics while still suppressing hydrogen gas production.
Solution Approach 2:
Instead of using chemical additives (nitro compounds) in the electrolyte to suppress hydrogen evolution, a conductive layer intermediary is applied to the cathode surface. This alternative approach achieves hydrogen suppression without the detrimental effect of reduced withstand voltage associated with nitro compound additives.
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 reduces hydrogen gas production, enhancing the reliability and performance of electrolytic capacitors by maintaining lower internal pressure and preventing casing expansion, even at high voltages.
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 may be at the higher side than the natural immersion potential of the reference cathode foil
Implementation Method 2
the cathode reaction to reduce dissolved oxygen rather than hydrogen ions, effectively suppressing hydrogen gas production
Implementation Method 3
The electrolyte solution repairs deteriorated portion of the dielectric oxide film layer formed on the anode foil, such as deterioration and damage, by leakage current. However, hydrogen gas is produced due to the film repairment by the leakage current of the dielectric oxide film layer
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 includes cathode foil formed of valve action metal and a conductive layer formed on a surface of the cathode foil. A natural immersion potential of the cathode foil when immersed in an electrolyte solution 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%.