Secondary Battery Separator End Overlap for Winding Stress
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Solution Overview
Problem
Existing electrode assemblies for secondary batteries face issues with uneven stress distribution due to potential bending at the corner parts of the separators during the winding process, which affects the packing efficiency, yield cycle time, and quality of the assembly.
Innovation Solution
The electrode assembly incorporates an outer separator with a functional layer of adhesive resin having a higher melting point than the base material, combined with an inner separator, where the end portions of both separators overlap to form an end portion overlapping part with a thickness greater than the sum of the electrode facing parts, preventing bending at the corner parts during winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the end portions of two separators are laminated and heat-fused to form a joint part, then the separators can be prevented from bending at the joint part, but the corner parts of the end portions may still bend inward or in another direction causing uneven stress distribution
Solution Approach 1:
The patent applies local quality by creating an end portion overlapping part with increased thickness (greater than the sum of the two electrode facing parts) specifically at the corner regions of the separator end portions. This localized thickening provides enhanced structural support and stress distribution at the vulnerable corner areas, while the rest of the separator maintains its original properties. The functional layer with adhesive resin is also strategically positioned to provide localized reinforcement where bending is most likely to occur.
2Force
If pressure is exerted on the electrode assembly from the outside, then the battery operates under compression, but local increase in thickness at the joint part causes uneven stress on the electrode assembly
Solution Approach 1:
The patent changes the physical parameter of thickness at the end portion overlapping part, making it larger than the sum of the thicknesses of the two electrode facing parts. This parameter change creates a gradual transition in thickness from the joint part toward the electrode facing parts, which helps distribute compression stress more uniformly throughout the separator structure when external pressure is applied to the battery.
3Ease of manufacture
If the separators are wound into the electrode assembly, then the battery is assembled, but the corner parts of the end portions bend inward or in another direction during winding
Solution Approach 1:
The patent implements preliminary action by pre-forming the end portion overlapping part with increased thickness and proper geometry before the winding process. This preliminary structural preparation ensures that the separator end portions maintain their shape and do not bend inward or in unwanted directions during the winding operation, thereby facilitating smoother assembly while preserving separator integrity.
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 configuration enhances the durability and performance of the electrode assembly by preventing bending at the corner parts of the separators, ensuring even stress distribution and improved structural integrity during pressure application.
Implementation Method 1
a functional layer having an adhesive resin with a higher melting point than that of a separator base material
Implementation Method 2
a thickness of the end portion overlapping part is larger than a sum of thicknesses of the two electrode facing parts
Data Source
AI summary
This electrode body for secondary batteries comprises: a positive electrode; a negative electrode; an outer separator; and an inner separator which is arranged inside the outer separator. An outer electrode, which is either the positive electrode or the negative electrode arranged on the outer side, is sandwiched by the outer separator and the inner separator. The outer separator and the inner separator have: two electrode facing parts that face the outermost layers of the outer electrode, while overlapping with each other, with the outer electrode being interposed therebetween; and a terminal overlapping part that is provided at respective ends of the outer separator and the inner separator. The thickness of the front end of the terminal overlapping part is larger than the sum of the thicknesses of the two electrode facing parts.