Cylindrical Alkaline Battery Negative Electrode Design
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Solution Overview
Problem
Cylindrical alkaline storage batteries face issues with increased internal resistance and short circuits due to cracks or splits in the thin parts of the negative electrode, which hinder capacity enhancement and cycle durability.
Innovation Solution
The battery design features a negative electrode with a thin part that is more flexible due to reduced active material volume, positioned differently from the positive electrode, and a boundary part with varying thickness and increased mass per unit area to prevent cracks and splits, ensuring the electrode group is securely inserted without increasing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative electrode is made thinner in the outermost circumferential part to increase volumetric efficiency, then battery capacity is improved, but cracks and splits occur in the thin part causing short circuits and increased internal resistance
Solution Approach 1:
The negative electrode is designed with non-uniform thickness: the outermost circumferential part (thin part) has reduced thickness to increase volumetric efficiency and capacity, while the inner part (main part) maintains sufficient thickness for mechanical strength. This local differentiation allows the battery to achieve high capacity without compromising electrode integrity, as each region is optimized for its specific function.
2Stability of the object's composition
If the thin part of the negative electrode is made more flexible by reducing active material volume, then the electrode can be inserted without cracks, but the amount of active material is reduced
Solution Approach 1:
The thin part of the negative electrode has reduced active material volume compared to the main part, making it more flexible and suitable for insertion into the battery casing without developing cracks. The main part retains sufficient active material for electrical performance. This local differentiation optimizes both flexibility and active material utilization.
Solution Approach 2:
The negative electrode extends beyond the outer end of the positive electrode in the circumferential direction, creating a three-dimensional arrangement where the thin part wraps around the outer circumference. This dimensional arrangement allows the flexible thin part to conform to the battery casing while the main part remains positioned for optimal electrical contact.
3Manufacturing precision
If the boundary part is designed with varying thickness to prevent cracks, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The boundary part is designed with a specific thickness gradient that transitions from the thin part to the main part. This controlled variation in thickness prevents stress concentration and crack formation at the transition zone, while maintaining overall structural simplicity suitable for manufacturing.
Data Source
AI summary
A cylindrical alkaline storage battery suitable to increase its capacity and arranged to prevent a short circuit and internal resistance increase, including an electrode group held in an outer can and formed by rolling up together a negative electrode having a negative-electrode core body and a hydrogen-absorbing alloy layer supported thereon, a positive electrode, and a separator. The negative electrode includes a main part forming inside part of the electrode group, a thin part smaller than the main part in the thickness of the hydrogen-absorbing alloy layer and the amount of a hydrogen-absorbing alloy contained in unit volume of that layer, and a boundary part formed between the main and thin parts and having a hydrogen-absorbing alloy layer thickness varying along the length of the negative-electrode core body. The positive electrode outer end and the negative electrode boundary part are at different positions circumferentially of the electrode group.