Serpentine Separator Electrode Assembly With Uniform Adhesion
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Solution Overview
Problem
Existing electrode assemblies experience deviations in adhesive force and air permeability across layers, leading to issues such as lithium precipitation and non-charging, while maintaining adequate adhesive force and air permeability is crucial for uniform performance.
Innovation Solution
The electrode assembly employs an elongated separator sheet folded in a serpentine pattern between electrodes, with a manufacturing process involving primary and secondary heat press operations to ensure uniform adhesive force and air permeability, using a specific temperature, pressure, and time regimen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electrode assembly manufacturing is used, then production efficiency is maintained, but deviations in adhesive force and air permeability across layers occur
Solution Approach 1:
The separator is pre-heated before stacking to activate its adhesive properties in advance. This preliminary heating ensures that when the separator contacts the electrodes during stacking, it immediately bonds uniformly across all layers, eliminating deviations in adhesive force and air permeability that would otherwise occur during the stacking process.
Solution Approach 2:
The manufacturing process utilizes temperature parameter changes by heating the separator to a specific temperature range before stacking. This parameter change transforms the separator's adhesive characteristics, enabling uniform bonding across all electrode layers and resolving the inconsistency in adhesive force and air permeability.
2Strength
If adhesive force is increased to prevent layer separation, then structural stability improves, but air permeability decreases
Solution Approach 1:
By controlling the temperature parameter during separator heating, the adhesive force is enhanced to an optimal level without excessive increase. The temperature is maintained within a specific range that activates adhesion sufficiently to prevent layer separation while preserving the separator's porosity and air permeability for lithium ion transport.
Solution Approach 2:
The separator is designed as a composite structure combining adhesive functional layers with porous transport layers. This composite material approach allows simultaneous achievement of adequate adhesive force for structural stability and sufficient air permeability for lithium ion conduction, resolving the trade-off between these two properties.
3Reliability
If air permeability is increased to improve lithium ion transport, then charging performance improves, but adhesive force decreases
Solution Approach 1:
The separator employs a composite material design with distinct functional zones: one layer optimized for high air permeability and lithium ion transport, and another layer providing adhesive bonding to electrodes. This composite structure enables the assembly to achieve both high charging performance through improved ion transport and adequate structural stability through strong adhesion.
Solution Approach 2:
Different regions of the separator are assigned different properties: the surface layers contact electrodes and provide adhesion, while the central porous region maximizes air permeability for lithium ion transport. This local differentiation of quality allows the separator to simultaneously satisfy both adhesive and permeability requirements without compromise.
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 prevents lithium precipitation and non-charging, ensures uniform performance, and facilitates easier handling and electrolyte wetting, while maintaining appropriate adhesive force and air permeability.
Implementation Method 1
a heating unit (121b) for heating the separator
Implementation Method 2
a pressing unit (180) for pressing the first electrode (11), the separator (14), and the second electrode (12) to one another
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
An electrode assembly includes a plurality of electrodes arranged in a stack along a stacking axis with a respective separator portion of an elongated separator sheet positioned between and winding around each of the electrodes in the stack along a serpentine path. An intermediate one of the separator portions may be adhered to an intermediate one of the electrodes such that it would take a peel force in a range from 5 gf to 35 gf per 20 mm width applied to an edge of the intermediate separator portion in order to peel it away from the intermediate electrode at a speed of 100 mm/min along the stacking axis. Moreover, top and bottom ones of the separator portions may each have a value of air permeability from 70 sec/100ml to 85 sec/100ml per square inch of the respective separator portion at a pressure of 0.05 MPa and at room temperature.