Folded Separator Adhesive Unfolding for Battery Deformation
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Solution Overview
Problem
Lithium-ion batteries experience irreversible deformation due to stress from separator contraction, electrode expansion, and winding stresses, leading to increased thickness and potential equipment incompatibility, which existing methods like buffer layers and complex processes fail to completely alleviate.
Innovation Solution
A separator with a folded structure unit across its widthwise direction, filled with an adhesive, which unfolds after electrolyte injection and high-temperature aging, effectively eliminating deformation caused by thermal contraction and electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of separator is used to separate cathode and anode in winding or laminating structures, then the separation function is improved, but the cell thickness increases and deformation occurs due to accumulated contraction stress
Solution Approach 1:
The separator is divided into multiple layers with different functions: a base separator layer for separation and a stress-compensation layer with folded structure for stress management. This segmentation allows each layer to perform its specific function optimally without the entire separator contributing to thickness accumulation.
Solution Approach 2:
The folded structure unit in the stress-compensation layer is designed to dynamically adjust its configuration in response to stress changes. The folds can expand or contract to compensate for thermal contraction and electrode expansion stresses, maintaining separator effectiveness while preventing cell deformation.
2Ease of manufacture
If the separator is wound to form the cell, then the cell structure is formed, but contraction stress accumulates in the separator toward the center and causes irreversible deformation
Solution Approach 1:
The stress-compensation layer with folded structure is pre-installed on the separator before winding. This preliminary configuration allows the layer to actively counteract contraction stresses as they develop during winding and cell operation, preventing stress accumulation before it causes deformation.
Solution Approach 2:
The folded structure converts the harmful contraction stress into a beneficial mechanism: the folds act as stress absorbers that can expand to accommodate contraction, transforming the potential source of deformation into a stress-management feature that protects the cell structure.
3Force
If buffer layers are coated on electrode plates or separator to reduce winding stress, then stress reduction is achieved, but the process becomes complicated and cost increases
Solution Approach 1:
The stress-compensation layer is integrated directly onto the separator as a single unified component rather than adding separate buffer layers to multiple surfaces. This merging reduces the number of manufacturing steps while achieving the same stress-reduction effect.
Solution Approach 2:
Instead of changing material composition through multiple buffer layers, the invention changes the structural parameter of the separator by incorporating the folded configuration. This structural parameter change achieves stress management without requiring additional materials or complex coating processes.
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 prevents irreversible deformation in lithium-ion batteries by allowing the separator to relax and reduce stress on electrodes, maintaining battery compatibility and performance over cycles.
Implementation Method 1
the adhesive filled in the folded structure unit of the separator may be dissolved into the electrolyte, the folded structure unit can be unfolded to a flat position again
Implementation Method 2
the separator shrinks after being heated, a length of the separator shortens
Data Source
AI summary
The present disclosure provides a separator and an electrochemical device, the separator is provided with a folded structure unit across a widthwise direction of the separator, and an overlapping part of the folded structure unit is filled with an adhesive. When the separator is applied into a production of the electrochemical device, a winding process can be performed as usual. After an electrolyte injection or high temperature aging of the electrochemical device, the adhesive filled in the folded structure unit of the separator may be dissolved into the electrolyte, the folded structure unit can be unfolded to a flat position again, so as to effectively eliminate deformation of the electrochemical device, which may be caused by thermal contraction of the separator, over stress in the separator wound in a cell, or the separator's binding on expansion of negative and positive electrodes, during operation and production of the electrochemical device.