Z-Stack Battery Separator Fusion to Prevent Electrode Unwinding
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Solution Overview
Problem
Secondary batteries with Z stack electrode assemblies face issues of unwinding and reduced safety due to weak structural integrity and large gaps between electrode plates and the separator, leading to performance deterioration and capacity loss under external impacts.
Innovation Solution
The outermost end area of the separator is thermally fused to the bent areas, and the remaining bent areas are contracted to enhance structural stability, applying adhesives in various shapes to absorb impacts and prevent unwinding, thereby improving manufacturing processability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator is bent in a Z shape to form a stack electrode assembly, then the battery capacity is increased, but the structural integrity deteriorates leading to unwinding and safety issues
Solution Approach 1:
The outermost end area of the separator is thermally fused to the bent area in advance during manufacturing, creating a preliminary bond that prevents unwinding during subsequent handling and use. This preliminary action addresses the structural integrity issue before it can manifest as a problem.
Solution Approach 2:
The separator undergoes thermal fusion at its outermost end area, changing its physical state from flexible to bonded/fused. This parameter change creates a permanent attachment point that maintains the Z-stack structure while preserving the bent configuration needed for high capacity.
2Reliability
If the outermost end area of the separator is thermally fused to bent areas, then safety against unwinding is improved, but manufacturing complexity increases
Solution Approach 1:
The mechanical bonding of the separator end to the bent area is replaced with thermal fusion. Instead of using mechanical fasteners, clips, or complex clamping mechanisms, the patent uses heat to create a permanent bond, simplifying the manufacturing process while ensuring reliable attachment.
Solution Approach 2:
Heat acts as an intermediary medium to bond the separator end to the bent area. The thermal energy facilitates the fusion process, creating a strong bond without requiring direct mechanical intervention or complex bonding equipment.
3Quantity of substance
If the bent areas are contracted to reduce Z stack width, then battery design capacity is increased, but the separator gaps become smaller reducing safety margin
Solution Approach 1:
The separator is designed with different properties in different regions: the outermost end area is thermally fused to provide structural anchoring, while the heat contraction areas are selectively reduced in width to increase capacity. This local differentiation allows the separator to simultaneously achieve high capacity and maintain safety through strategic reinforcement at critical locations.
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 solution prevents unwinding, enhances safety against external impacts, and increases battery design capacity by stabilizing the electrode assembly and reducing its width, thus improving overall performance and protection of side surfaces.
Implementation Method 1
the outermost end area of the separator is bent to be thermally fused to a bent area of the plurality of bent areas of the separator
Implementation Method 2
The bent area of the separator may include a heat contraction area. A spaced distance between the heat contraction area and each of ends of the first and second electrode plates may be about 0.01 mm to about 1 mm
Data Source
AI summary
A secondary battery includes a Z stack electrode assembly including a separator bent in a Z shape and including a plurality of bent areas, a first electrode plate on a lower portion of each of the bent areas, and a second electrode plate on an upper portion of each of the bent areas, and an exterior portion configured to accommodate the Z stack electrode assembly, and an outermost end area of the separator is bent to be thermally fused to a bent area of the plurality of bent areas of the separator.