Separator Joint Buffer for Battery Electrode Protection
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Solution Overview
Problem
Existing electrode assemblies for electric storage elements, such as non-aqueous electrolyte secondary batteries, face challenges in reliably preventing the positive and negative sheets from contacting foreign materials due to the deterioration of the joint strength between separators, which can lead to separation and exposure to metal particles generated during welding.
Innovation Solution
The solution involves forming a joint portion between the separators to wrap the positive and negative sheets, and creating a separating portion outside the joint to act as a buffer, preventing direct contact with the sheets or electric collectors, thereby stabilizing the bond strength and preventing foreign material contact. This can be achieved through thermal fusion bonding or compression bonding, and optionally using a protecting layer made of insulating materials like alumina.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the joint portion joints the two separators at the outermost side in the width direction, then the positive sheet and negative sheet are wrapped to prevent foreign material contact, but the joint portion is brought into direct contact with leads or electric collector causing deterioration of joint strength and separation
Solution Approach 1:
The patent introduces a buffer portion as an intermediary element between the joint portion and the leads/electric collector. This buffer portion absorbs the direct contact and mechanical stress, preventing the joint portion from being brought into direct contact with the leads or electric collector during vibration or shock, thereby maintaining joint strength while preserving the wrapping protection function.
Solution Approach 2:
The separator structure is segmented into three distinct functional regions: a joint portion for bonding the separators, a buffer portion for absorbing mechanical stress and preventing direct contact with leads, and a wrapping portion for covering the sheets. This segmentation allows each region to perform its specific function optimally without interfering with the others.
2Object-affected harmful factors
If the joint portion is formed by thermal fusion bonding of the two separators, then the positive and negative sheets are wrapped to prevent foreign material contact, but the joint strength deteriorates under vibration and shock
Solution Approach 1:
The buffer portion is designed in advance as a cushioning element that anticipates and absorbs the impact of vibration and shock before they can reach the joint portion. This beforehand cushioning protects the thermally fused joint from mechanical stress that would otherwise cause deterioration or separation.
3Object-affected harmful factors
If the separators are positioned to wrap the sheets, then protection against foreign material is achieved, but the joint portion becomes vulnerable to separation under vibration and shock
Solution Approach 1:
The buffer portion serves as a mediator between the stable joint portion and the external environment causing vibration and shock. It absorbs these disturbances, allowing the joint portion to maintain its stable bonded state while the separators continue to provide wrapping protection.
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 approach effectively prevents the positive and negative sheets from contacting foreign materials, stabilizing the joint strength and preventing separation of the separators, thus enhancing the protection of the sheets from metal particles and maintaining the integrity of the battery.
Implementation Method 1
The joint portion is formed by, e.g., thermal fusion bonding of the two separators by heat rollers at the time of winding
Implementation Method 2
a separating portion that is formed outside the joint portion so that the first separator and the second separator are separated from each other
Data Source
AI summary
An electrode assembly has a positive sheet, a negative sheet, and separators that are stacked and wounded. A joint portion is formed by thermally fusion bonding or compression bonding of the separators at one end in a width direction thereof so that one end of the positive sheet on an opposite side in a width direction with respect to a positive lead is wrapped by the separators. Arranged outside of the joint portion in the width direction is a separating portion where the separators are separated from each other. A protecting layer made of an insulating material is formed on the end face of the positive sheet. The positive sheet is reliably prevented from being in contact with a foreign material.