Lithium-Ion Button Cell Electrode Tabs With Insulated Reinforcement
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Solution Overview
Problem
Existing rechargeable lithium-ion button cell batteries face issues with electrode connections that are prone to breakage during welding and expose metal surfaces to electrolyte, leading to short circuits and reduced cycle life.
Innovation Solution
The electrodes are designed with tapered widths and conductor tabs that are either bent outward and upward or welded to a metal flake with insulation washers, ensuring no metal is exposed to electrolyte, and the battery is sealed with a crimped gasket for reliable connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the conductor tab is made thin (0.006mm to 0.016mm) to reduce weight and improve energy density, then the volumetric energy density is improved, but the tab becomes easy to break during welding and assembly
Solution Approach 1:
The conductor tab is divided into two parts: a thin tab portion (0.006mm to 0.016mm) for maintaining low weight and high energy density, and a thicker reinforcement portion (0.03mm to 0.06mm) that extends to the casing inner surface to provide mechanical strength during welding and assembly. This segmentation allows each part to optimize its thickness for its specific function.
Solution Approach 2:
The conductor tab transitions from a uniform thin structure to a multi-dimensional structure with varying thickness. The tab portion remains thin for energy density, while the reinforcement portion extends in the vertical dimension to reach the casing inner surface, creating a thickness gradient that solves both the energy density and strength requirements.
2Reliability
If the conductor tab is extended in length to be welded directly to the casing, then the welding connection is improved, but the tab becomes more prone to breakage during assembly
Solution Approach 1:
The conductor tab is segmented into a thin tab portion for electrical connection and a separate thicker reinforcement portion for mechanical support. The reinforcement portion extends to the casing inner surface to provide a strong welding base without requiring the entire tab to be thick, thus preventing breakage during assembly.
Solution Approach 2:
The reinforcement portion acts as an intermediary element between the thin tab and the casing. It provides a mechanically strong connection point for welding to the casing while the thin tab portion maintains low weight and high energy density, mediating between the conflicting requirements of strength and energy density.
3Reliability
If insulation washers are used to cover the casing inner surface, then short circuit prevention is improved, but it becomes difficult to fully cover the metal flake
Solution Approach 1:
The reinforcement portion of the conductor tab is designed to extend to and contact the casing inner surface before the insulation washer is installed. This preliminary extension ensures that the metal flake and tab connection area are already positioned for complete coverage by the washer, making the insulation process more effective and easier to manufacture.
Solution Approach 2:
The design replaces the need for complex multi-washer insulation systems with a simpler single-washer system. The reinforcement portion provides a standardized interface that allows one insulation washer to fully cover all metal surfaces, simplifying the insulation mechanism while maintaining reliability.
Data Source
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AI summary
A rechargeable lithium ion button cell battery having a sealed housing comprises an inner casing and an outer casing , both casings have at least one flat area as top or bottom of the battery, and a round or oval sidewall vertically formed to the flat area. An insulation gasket is positioned between said sidewalls, and the outer casing opening is mechanically crimped to complete the seal of the battery. Inside the sealed housing the anode and cathode electrodes are spiral wound with separator to be a round or oval roll. Said roll axis is vertical to the said flat areas of the casings. The two electrodes are tapered in width to fully utilize the inner space. The electrodes comprise current collectors of metal foils coated with lithium-intercalating active materials, leaving small area of uncoated metal foils as conductor tabs for connecting the electrodes to the casings. The tabs could be welded or by tight contacting to the casings, in several options. Insulation washers or tapes are applied to the naked metal surfaces of the electrodes or casings inside of the housing to prevent short circuit and enable the battery to have longer cycle life.