Cylindrical Cell Separator With Integrated Heat-Sealed Bottom
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Solution Overview
Problem
Conventional cylindrical cell separators face challenges in maximizing available cell volume, requiring additional materials and complex handling processes, leading to increased internal resistance and reduced performance due to the need for laminated structures and sealants, which complicates high-speed manufacturing.
Innovation Solution
A guided separator is developed where the sheet material is wound around a mandrel, with an extended lower portion that is welted and heat-formed to create a sealed bottom without the need for external sealants, allowing on-line length adjustments and eliminating the requirement for laminated sheets, thereby optimizing cell volume and reducing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an outer and inner isolating cup are attached to the lower end of the separator with thermoplastic sealant, then reliable insulation between electrodes is achieved, but substantial cell volume is occupied by cups and sealant reducing useful capacity
Solution Approach 1:
The separator and bottom insulating structure are merged into a single integrated component. The separator sheet material is formed to include an integral bottom portion that extends downward and is folded back to create the insulating bottom structure, eliminating the need for separate cups and sealant applications.
Solution Approach 2:
The separator is divided into functional zones: the main separator body for ion conduction and the integrated bottom portion for insulation. The bottom portion is further segmented into side walls and a closed bottom, creating distinct functional regions within a single component.
2Stability of the object's composition
If the separator is made longer than required and windings are bound with a binder then folded back to close the bottom, then a self-containing unit is formed, but the closing operation is complicated requiring movements in different directions and creating wrinkles
Solution Approach 1:
The binder material is extracted and eliminated from the process. Instead of binding windings with additional material, the separator sheet material itself is formed and folded to create the closed bottom structure, using only the base material.
Solution Approach 2:
The physical state of the separator material is changed by heating during the folding process. The heat treatment makes the material more pliable for folding and then sets the folded structure, enabling complex shaping without additional binding materials.
3Reliability
If a hot melt sealant is applied to fill the cell bottom including the bottom region of the separator, then the bottom is sealed, but the available useful cell volume is decreased
Solution Approach 1:
The separator structure performs its own sealing function through the folded and heat-formed bottom portion. The integral design creates a self-contained structure that seals the bottom region without requiring external sealant materials.
4Reliability
If a laminated structure with semi permeable membrane layer is used for secondary cells, then proper separation function is achieved, but cost increases and internal resistance increases due to adhesives
Solution Approach 1:
The separator is constructed from a single homogeneous porous material throughout, without laminated layers or adhesive bonds. The uniform porous structure provides consistent ion conduction properties and eliminates the energy losses associated with multiple material interfaces.
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 solution enables maximum utilization of cell volume, reduces internal resistance, and simplifies the manufacturing process by eliminating the need for adhesives and laminates, resulting in improved performance and synchronization with high-speed manufacturing lines.
Implementation Method 1
the extension is at least equal to the radius of the separator cylinder and this extending portion is welted with distilled or de-ionized water and wetted until the material softens
Implementation Method 2
The folding step is followed by a heat forming and fusing step, wherein a heated die is pressed against the bottom of the mandrel pressing and heating the folded portion therebetween, which causes the sheet material to fuse together
Data Source
AI summary
Separator for cylindrical cell of the outwardly guided type, wherein a sheet material is wound around a mandrel, and starting from the winding step until the insertion of a separator into the cell, an outward support is used that renders the binding of neighboring turns of the separator winding unnecessary, and the separator sheet has an extended portion, with the extension being at least equal to the radius of the separator cylinder, and with this extended portion being wetted with distilled or de-ionized water until the material softens and the winding and the mandrel are rotated and the bottom part is folded back and heat fused to close the separator cylinder.