Electrolytic Capacitor Electrolyte for Low Impedance at 400 V
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Solution Overview
Problem
Current electrolytic capacitors face challenges in achieving both high withstand voltage and long lifetime, particularly at high temperatures, due to hydration reactions that lead to increased internal pressure and capacitor deterioration, and existing solutions fail to balance chemical conversion capability and voltage withstand effectively.
Innovation Solution
An electrolytic capacitor configuration with an electrolytic solution containing ethylene glycol, 10 to 30% water, 1 to 12% amine salt of a polycarboxylic acid, and 0.01 to 2% ammonium hypophosphite or hypophosphorous acid, which suppresses hydration reactions and enhances chemical conversion capability, allowing for low impedance and high withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of water in the electrolytic solution is increased to achieve low impedance, then the impedance decreases, but the anode foil and cathode foil undergo hydration reaction at high temperature to generate gas, leading to increased internal pressure and capacitor deterioration
Solution Approach 1:
The patent introduces diethylamine azelate as an intermediary substance in the electrolytic solution that mediates between water and the electrode foils. This additive suppresses the hydration reaction between water and the foils while maintaining the beneficial low-impedance characteristics of higher water content solutions. The diethylamine azelate acts as a protective intermediary layer that prevents direct harmful interaction between water and the aluminum foils.
Solution Approach 2:
The patent optimizes the concentration parameters of multiple components in the electrolytic solution: water content (10-30% by mass), diethylamine azelate (14-22% by mass), and ammonium hypophosphite (0.01-2% by mass). By carefully controlling these parameter ranges, the solution achieves a balance where sufficient water content provides low impedance while the optimized concentrations of additives suppress hydration reactions and maintain thermal stability.
2Stability of the object's composition
If diethylamine azelate or triethylamine salt is used to suppress hydration reaction, then thermal stability improves, but both good chemical conversion capability and high withstand voltage cannot be achieved simultaneously
Solution Approach 1:
The patent creates a composite electrolytic solution system that combines multiple functional components: diethylamine azelate (for thermal stability and hydration suppression), ammonium hypophosphite (for chemical conversion capability and oxide film formation), and controlled water content (for low impedance). This composite approach allows each component to contribute its specific benefit while the synergistic interaction among components achieves both thermal stability and high withstand voltage capability simultaneously.
Solution Approach 2:
The patent applies different functional additives to different aspects of capacitor performance: diethylamine azelate specifically targets thermal stability and hydration suppression, while ammonium hypophosphite specifically enhances chemical conversion capability and oxide film quality. This localized functional assignment allows each additive to optimize its specific function without interfering with the overall performance balance.
3Reliability
If the content of water is increased to achieve low impedance, then the impedance decreases, but the lifetime of the electrolytic capacitor is shortened due to deterioration of the anode foil and cathode foil
Solution Approach 1:
The patent employs diethylamine azelate and ammonium hypophosphite as protective agents that cushion against the harmful effects of high water content before deterioration can occur. These additives preemptively suppress hydration reactions and protect the electrode foils from water-induced deterioration, allowing the capacitor to maintain low impedance over an extended service life without suffering from accelerated aging.
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 proposed configuration achieves a balance of low impedance, high withstand voltage, and extended lifetime by controlling water content and using specific amine salts and hypophosphorous acid, preventing capacitor malfunction and maintaining performance across a wide temperature range.
Implementation Method 1
it has been found that the configurations of PTLs 4 and 5 fail to achieve both a good chemical conversion capability and a high withstand voltage... diethylamine azelate or a triethylamine salt contained suppresses, to a certain extent, the hydration reaction of the electrode foils (particularly the cathode foil) due to a large amount of water
Implementation Method 2
An aluminum electrolytic capacitor uses, as a dielectric material, an oxide film formed on the surface of an aluminum foil through an electrochemical surface treatment
Implementation Method 3
an oxide film formed on the surface of an aluminum foil through an electrochemical surface treatment
Implementation Method 4
An electrolytic capacitor has, for example, a configuration having formed therein a capacitor element including an anode foil and a cathode foil, which each are electrically connected to a terminal, with a separator intervening therebetween
Data Source
AI summary
To provide an electrolytic capacitor having a configuration that achieves a low impedance by increasing the content of water, satisfies a withstand voltage of 400 V or more, and is capable of enhancing the long-term reliability. Provided as a solution is an electrolytic capacitor (1) including an electrolytic solution (2e) containing ethylene glycol, 10 to 30% by mass of water, and 1 to 12% by mass of an amine salt of a carboxylic acid, having added thereto 0.01 to 2% by mass of one or more kind of ammonium hypophosphite, an amine salt of hypophosphorous acid, and hypophosphorous acid, the carboxylic acid being a polycarboxylic acid having a chain hydrocarbon skeleton and a molecular weight of 140 to 500.