Alkaline Cell Anode Casing Alloy Coating Hydrogen Gassing
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Solution Overview
Problem
Aqueous alkaline battery cells, particularly button and metal-air cells, face challenges in leakage resistance due to hydrogen gas evolution, electrocapillary leakage, and electrochemically driven creepage, especially without added mercury, which affects their aesthetic appearance and functional integrity.
Innovation Solution
The use of a negative electrode casing made from a copper-free metal substrate coated with an alloy of copper, tin, and zinc, where the relative amounts of copper, tin, and zinc are between 55 to 85, 9 to 30, and 2.5 to 20 by weight, respectively, to minimize hydrogen gassing and enhance leakage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If mercury is added to alkaline cells to minimize hydrogen gas evolution, then hydrogen gassing is reduced, but environmental concerns arise and aesthetic appearance is compromised
Solution Approach 1:
The invention extracts and eliminates mercury from the alkaline cell system by replacing it with alternative materials (bismuth, indium, gallium) that provide the same hydrogen gassing suppression function without the environmental toxicity. This directly resolves the contradiction by removing the harmful substance while maintaining the desired performance.
Solution Approach 2:
The invention changes the chemical composition parameters of the cell by substituting mercury with alternative metals having appropriate hydrogen evolution overpotentials. This parameter substitution maintains the functional performance (hydrogen gassing control) while eliminating the environmental harm associated with mercury.
2Ease of manufacture
If seal members and sealing interfaces are made porous or have openings, then assembly is easier, but electrolyte wicking and leakage increase
Solution Approach 1:
The invention applies different properties to different parts of the sealing system. Seal members have localized non-porous regions at critical sealing interfaces to prevent electrolyte wicking, while other areas may remain porous for assembly flexibility. This local differentiation resolves the contradiction by providing both ease of assembly and leakage resistance where needed.
3Power
If negative electrode casing surface area is increased to improve electrical contact, then current collection is enhanced, but hydrogen gassing and leakage opportunities increase
Solution Approach 1:
The invention changes the surface property parameters of the negative electrode casing by coating it with metals having high hydrogen evolution overpotentials (bismuth, indium, gallium). This parameter change allows the casing to maintain large surface area for current collection while suppressing hydrogen gassing that would otherwise occur at increased surface areas.
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 solution effectively reduces hydrogen gassing and electrochemically driven creepage, improving the leakage resistance of alkaline battery cells while maintaining an attractive appearance and ensuring the cells operate without added mercury.
Implementation Method 1
Mercury worked well to inhibit hydrogen gassing and electrochemically driven creepage because it has a very high hydrogen evolution overpotential
Implementation Method 2
Electrolyte can wick by capillary action through pores and other openings in seal members and between seal members and other components that seal electrolyte within the cell housing
Implementation Method 3
Electrochemically driven creepage can occur between a seal member and a metal housing component at a negative potential
Data Source
Figure 1
AI summary
The invention is an electrochemical cell with a zinc-containing negative electrode, an aqueous alkaline electrolyte and a cup-shaped metal negative electrode casing in contact with the negative electrode. The negative electrode casing is formed from a substrate that is substantially free of copper and at least those portions of the surface of the negative electrode casing in the seal area and the current collector area are coated with a layer of an alley comprising copper, tin and zinc. The alloy layer reduces hydrogen gassing within the cell and is particularly useful in cells with no added mercury. Embodiments of the invention include cells with prismatic, cylindrical and button shaped containers and cells with positive electrode active materials including manganese dioxide, silver oxide and oxygen.