Neutral Electrolyte for Wet Capacitor Corrosion
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Solution Overview
Problem
Conventional wet electrolytic capacitors face issues with corrosion when using corrosive electrolytes, leading to problems such as aluminum current collector sensitivity and detachment of cathode coatings, which can result in reduced electrical properties and reliability.
Innovation Solution
A neutral pH working electrolyte with a conductivity of 10 milliSiemens per centimeter or more, comprising solvents and ionic compounds, along with a depolarizer like alkyl-substituted nitroaromatic compounds, is used to stabilize the electrolyte and maintain electrical conductivity while preventing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corrosive electrolytes (e.g., sulfuric acid) are used to achieve high electrical conductivity, then electrical conductivity is improved, but corrosion of aluminum current collector and detachment of cathode coatings occur, reducing reliability
Solution Approach 1:
The patent changes the pH parameter of the electrolyte from highly acidic (conventional) to neutral (pH 6.5-7.5). This parameter change fundamentally alters the chemical properties of the electrolyte, making it non-corrosive to aluminum current collectors and cathode coatings while maintaining adequate electrical conductivity through careful selection of ionic compounds and their concentrations.
Solution Approach 2:
The patent employs a composite electrolyte formulation consisting of multiple components: ionic compounds (such as lithium salts, sodium salts, potassium salts, calcium salts, or aluminum salts), solvents (such as water, alcohols, ketones, esters, or amides), and optional additives. This composite approach allows the electrolyte to achieve both chemical stability (non-corrosiveness) and electrical conductivity simultaneously, resolving the contradiction between reliability and harmful factors.
2Reliability
If neutral liquid electrolytes are used to avoid corrosion, then reliability is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent optimizes the concentration parameters of ionic compounds in the neutral electrolyte to achieve adequate electrical conductivity. By carefully controlling the amount of ionic compounds (e.g., 0.1-10 mM lithium salts, sodium salts, potassium salts, calcium salts, or aluminum salts) in the neutral pH electrolyte, the patent achieves a balance between maintaining neutral pH (for corrosion resistance) and sufficient ionic concentration (for electrical conductivity).
Solution Approach 2:
The patent uses a composite electrolyte system combining multiple ionic compounds with different properties, solvents, and optional additives. This composite formulation allows the electrolyte to achieve both chemical stability (neutral pH for corrosion resistance) and adequate electrical conductivity through the synergistic effect of multiple ionic species and solvent molecules, resolving the contradiction between reliability and energy loss.
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 solution provides a stable and conductive electrolyte that prevents corrosion, maintaining high electrical properties and reliability in wet electrolytic capacitors, even under elevated temperatures, by balancing pH and conductivity.
Implementation Method 1
The electrolyte has a pH of from about 5.0 to about 8.0 and an electrical conductivity of from about 10 milliSiemens per centimeter or more, determined at a temperature of 25° C.
Implementation Method 2
The working electrolyte comprises from about 1 to about 500 parts per million of a nitroaromatic depolarizer, the nitroaromatic depolarizer including an alkyl-substituted nitrobenzoic acid, an anhydride or salt thereof
Implementation Method 3
To avoid these problems, more neutral liquid electrolytes may be employed... The electrolyte has a pH of from about 5.0 to about 8.0... provides a stable and conductive electrolyte that prevents corrosion
Data Source
AI summary
A working electrolyte for use in a wet electrolytic capacitor is provided. The electrolyte is relatively neutral and has a pH of from about 5.0 to about 8.0, in some embodiments from about 5.5 to about 7.5, and in some embodiments, from about 6.0 to about 7.5. Despite possessing a neutral pH level, the electrolyte is nevertheless electrically conductive. For instance, the electrolyte may have an electrical conductivity of about 10 milliSiemens per centimeter (“mS/cm”) or more, in some embodiments about 30 mS/cm or more, and in some embodiments, from about 40 mS/cm to about 100 mS/cm, determined at a temperature of 25° C.