Laminate Film Cell with Thickened Edge Sealing
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Solution Overview
Problem
The use of aluminum laminate films as exterior packaging materials for cells poses challenges such as moisture infiltration, leading to degradation in cell properties and short-circuiting issues due to the thinness of the CPP layer and the sealing width, which affects the cell's capacity and safety.
Innovation Solution
A cell design with a laminate film structure that includes a thicker edge portion compared to the thermal welded portion, using a three-layered laminate film with a nylon or PET exterior layer, an aluminum foil, and a CPP interior layer, where the thermal welding is performed away from the edge to prevent burr-induced short-circuiting and ensure adequate sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the CPP layer thickness is reduced to increase cell capacity, then the cell capacity increases, but moisture infiltration risk increases leading to degradation in cell properties
Solution Approach 1:
The patent applies local quality by creating a thicker edge portion at the sealing area of the laminate film while maintaining a thinner CPP layer in the central area. This localized thickness variation provides enhanced moisture barrier and sealing strength at the edges where it is most needed, while allowing the central area to maintain thinness for maximum cell capacity. The edge portion thickness is specifically designed to be greater than the CPP layer thickness to prevent moisture infiltration during sealing operations.
2Quantity of substance
If the sealing width is reduced to increase cell capacity, then the cell capacity increases, but the sealing reliability decreases leading to moisture infiltration
Solution Approach 1:
The patent implements local quality by concentrating sealing function at the edge portion where the laminate film is folded back. The sealing width is minimized in the central area to maximize capacity, while the edge portion provides localized sealing strength through increased thickness. This allows the sealing function to be performed at the periphery rather than requiring a wide sealed area across the entire cell.
Solution Approach 2:
The patent transitions from a two-dimensional sealing approach (relying on wide sealing area) to a three-dimensional approach by creating variable thickness in the laminate film. The thicker edge portion adds a vertical dimension to the sealing structure, providing enhanced sealing capability without increasing the horizontal sealing width, thus maintaining cell capacity while improving sealing reliability.
3Reliability
If thermal welding is performed at the edge portion, then sealing is achieved, but short-circuiting occurs due to burr-induced contact between electrode terminal and aluminum layer
Solution Approach 1:
The patent extracts the thermal welding operation from the edge portion where it causes harmful effects. Instead of welding at the very edge where burrs could cause short-circuiting, the welding is performed at a position slightly inward from the edge. The folded-back structure then provides a buffer zone that prevents burr-induced short-circuiting while maintaining effective sealing.
Solution Approach 2:
The folded-back laminate film structure acts as an intermediary between the thermal welding zone and the edge area. This intermediate structure allows the welding to be performed safely inward from the edge while still achieving effective sealing at the perimeter, preventing direct contact between burrs and the electrode terminal or aluminum layer.
4Reliability
If a thicker laminate film is used to prevent moisture infiltration, then reliability improves, but cell capacity decreases due to reduced internal space
Solution Approach 1:
The patent applies local quality by varying the laminate film thickness across different regions. The edge portion has increased thickness to provide superior moisture barrier performance where it is most critical for sealing. The central area maintains reduced thickness to maximize the internal space available for active materials, thereby maintaining cell capacity. This spatially differentiated thickness distribution optimizes both reliability and capacity.
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 design prevents short-circuiting and moisture infiltration, maintaining superior cycle properties and cell capacity while ensuring the safety and reliability of the cell, even when the CPP layer thickness is reduced for increased capacity.
Implementation Method 1
two parts of an interior resin film of the laminate film are disposed to face each other, and thermal welding is performed along a peripheral portion of a cell element, so that air-tight sealing can be performed
Implementation Method 2
The metal foil 11 has an important role of protecting a content packaged in the laminate film from entering moisture, oxygen, and light
Data Source
AI summary
A cell in which thermal welding of a laminate packaging is performed so that the thickness of a thermal welded portion including an electrode terminal is larger than that of a thermal welded portion including no electrode terminal.