Battery Separator Edge Sealing to Prevent Electrode Exposure
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Solution Overview
Problem
In the production of lithium secondary batteries, particularly in the stacking or folding type, the exposure of electrodes during assembly leads to electric short circuits due to separator folding or tearing, resulting in low voltage defects, which existing methods fail to fully prevent by only sealing the edges in the width direction.
Innovation Solution
A separator sealing apparatus comprising first and second sealing units that thermally fuse and press the edges of upper and lower separators along both width and length directions, ensuring complete coverage and preventing electrode exposure, integrated with a transfer unit for synchronized operation on existing production lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only the edges of the cell semi-finished product are sealed in the width direction, then the sealing process is simple and fast, but the electrode may still be exposed due to separator folding or tearing
Solution Approach 1:
The sealing apparatus is divided into multiple independent sealing units (first sealing unit for width direction, second sealing unit for length direction) that can seal different regions of the separator. Each sealing unit operates independently with its own heating and pressing mechanisms, allowing comprehensive edge sealing without requiring a single complex sealing system.
Solution Approach 2:
The sealing process extends from one dimension (width direction only) to two dimensions (width direction and length direction). The first sealing unit seals edges in the width direction while the second sealing unit seals edges in the length direction, creating complete perimeter sealing that prevents electrode exposure from folding or tearing in any direction.
2Reliability
If edges are sealed in both width and length directions, then electrode exposure is fundamentally prevented, but the sealing process time increases
Solution Approach 1:
The sealing of both width and length direction edges is performed as preliminary actions before the cell assembly process. By completing all necessary sealing operations at this early stage, the patent prevents the need for additional sealing steps later, ultimately reducing total process time despite the increased initial sealing duration.
Solution Approach 2:
The multiple sealing units operate in a continuous manner to seal all edges of the separator. The first sealing unit and second sealing unit work together to simultaneously or sequentially seal all peripheral edges, ensuring continuous protective action without interruption or need for repositioning, which minimizes total sealing time despite comprehensive coverage.
3Manufacturing precision
If multiple sealing units are added to seal all edges, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The sealing system is segmented into specialized units: a first sealing unit with first upper and lower heating blocks for width direction edges, and a second sealing unit with second upper and lower heating blocks for length direction edges. Each unit is optimized for its specific sealing direction, achieving high precision through specialization rather than requiring a single complex multi-directional sealing mechanism.
Solution Approach 2:
Each sealing unit (first and second sealing units) is designed with universal functionality to handle both heating and pressing operations for its respective edges. The upper and lower heating blocks in each unit work together as a coordinated system, allowing each unit to perform complete sealing functions for its designated direction, reducing the need for additional specialized components.
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
Significantly reduces the low voltage defect rate by ensuring the electrode is not exposed, allowing for continuous mass production of cell semi-finished products with improved reliability and reduced defects.
Implementation Method 1
heating blocks configured to apply heat and pressure to outer regions at both short sides of the electrode plate
Data Source
AI summary
A separator sealing apparatus for bonding an upper separator and a lower separator with an electrode plate being interposed therebetween and a separator sealing method is provided. The separator sealing apparatus includes a first sealing unit configured to seal a first region specified as an outer edge along a width direction of the electrode plate, among portions where the upper separator and the lower separator face each other; and a second sealing unit configured to seal a second region specified as an outer edge along a length direction of the electrode plate, among the portions where the upper separator and the lower separator face each other.