Battery Unit Cell Separator Cutting With Thermal Fusion Sealing
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Solution Overview
Problem
In the manufacturing of secondary battery unit cells, the existing methods often result in separators being folded, leading to short circuits due to improper cutting, as the pressure applied during cutting can cause the separators to fold inwards, exposing electrodes and causing electrical shorts when unit cells are stacked.
Innovation Solution
A method and apparatus that involves cutting the separators between electrodes in a stacked configuration using a cutter that protrudes from an upper block, with both blocks being heated to a predetermined temperature to thermally fuse the separators, preventing folding by ensuring the cut portions remain bonded and maintaining a uniform shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is applied vertically to cut the separators using a traditional cutter, then the separators are cut between electrodes, but the separators are folded in the direction of pressure application, causing short circuits
Solution Approach 1:
The cutting process is divided into two distinct stages: first, the separator is cut by the cutter blade; second, the cut surface is sealed by the heated pressing surface. This segmentation of functions prevents the folding issue by separating the cutting action from the pressing action, and adding a sealing step to secure the cut edges.
Solution Approach 2:
The pressing surface is heated to a specific temperature range (50-150°C) to enable thermal sealing of the separator after cutting. This parameter change (adding heat) transforms the pressing surface from a simple mechanical press into a thermal sealing tool, which bonds the cut edges and prevents folding that would cause short circuits.
2Ease of manufacture
If the separators are cut without thermal fusion, then the cutting process is simpler, but the cut portions are not bonded and may fold, leading to short circuits
Solution Approach 1:
The cutting and sealing functions are merged into a single integrated pressing device. The pressing surface serves dual purposes: it provides mechanical pressure for cutting and thermal energy for sealing. This combination maintains manufacturing simplicity while ensuring separator stability through thermal bonding of the cut edges.
Solution Approach 2:
The heated pressing surface induces a phase transition in the separator material at the cut edges, melting and re-solidifying the material to create a sealed bond. This phase transition process ensures the cut portions are bonded and remain stable, preventing folding and short circuits.
3Manufacturing precision
If the upper and lower blocks are both heated, then the thermal fusion of separators is more effective, but the energy consumption increases
Solution Approach 1:
Instead of heating entire blocks uniformly, the heating is applied locally only to the pressing surfaces that contact the separators. This localized heating approach ensures effective thermal fusion at the critical interface while minimizing overall energy consumption by avoiding unnecessary heating of the entire block structure.
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 approach effectively prevents separator folding and short circuits by ensuring the separators are cut and bonded in a way that maintains their position, reducing the likelihood of electrical failures during the assembly of unit cells.
Implementation Method 1
at least one or more of the upper block and the lower block is heated to a predetermined temperature so that pressed points of the separators are thermally fused
Data Source
AI summary
An apparatus for manufacturing a unit cell cuts lower and upper separators between sets of adjacent electrodes. In a state of a process of manufacturing the unit cell, the lower and upper separators continuously move in a longitudinal direction; and the electrodes are stacked between the separators and on the upper separator, respectively. The apparatus includes a lower block disposed under the lower separator and an upper block vertically aligned with the lower block above the upper separator. A lower end of a cutter is installed for access to the inside and outside. The upper block descends to press the separators to a surface of the lower block. One or both of the upper and lower blocks is heated to a predetermined temperature to thermally fuse pressed points of the separators. The cutter protrudes from the upper block to perform cutting at points at which the separators are pressed.