Electrode Assembly Separator Bonding for Battery Bending Control
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Solution Overview
Problem
The expansion ratio difference between negative and positive electrodes in high-capacity secondary batteries causes bending and warping issues, leading to deformation and performance degradation.
Innovation Solution
An electrode assembly with a separator having a wet bonding force of 1.5 gf/20 mm to 15 gf/20 mm with respect to the negative electrode, and a dry bonding force of 8 gf/20 mm to 25 gf/20 mm, ensuring appropriate bonding forces to prevent bending and maintain alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the size of the electrode assembly is increased to achieve high capacity, then the battery capacity is improved, but the bending and warping of the electrode assembly becomes more severe due to non-uniform bonding force
Solution Approach 1:
The separator is designed with different bonding forces for different electrodes: a first bonding force for the positive electrode and a second bonding force for the negative electrode, where the bonding force to the negative electrode is greater. This local differentiation in bonding characteristics compensates for the differential expansion between positive and negative electrodes during charging/discharging, preventing bending and warping in large-sized high-capacity electrode assemblies.
2Stability of the object's composition
If the bonding force between separator and electrode is increased to prevent bending, then the structural stability is improved, but the expansion ratio difference causes non-uniform bonding leading to warping
Solution Approach 1:
The separator exhibits locally differentiated bonding characteristics with stronger bonding to the negative electrode than to the positive electrode. This asymmetric bonding design compensates for the greater expansion of the negative electrode during lithium insertion, maintaining uniform bonding force distribution across the electrode assembly and preventing warping while ensuring structural stability.
3Quantity of substance
If a silicon-based active material is used in the negative electrode to increase capacity, then the energy density is improved, but the expansion ratio during activation process increases causing bending
Solution Approach 1:
The separator is designed with enhanced bonding force specifically to the negative electrode containing silicon-based active material. This localized strengthening of bonding at the negative electrode interface compensates for the large expansion that occurs when silicon-based materials undergo lithium insertion during activation, preventing bending while maintaining the high energy density benefits of silicon-based anodes.
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
Prevents bending and warping of the electrode assembly, improving assembly yield and maintaining electrode position alignment, thereby enhancing cell performance and energy density.
Implementation Method 1
a wet bonding force of the separator with respect to the negative electrode is 1.5 gf/20 mm or more and 15 gf/20 mm or less
Implementation Method 2
a dry bonding force of 8 gf/20 mm to 25 gf/20 mm, ensuring appropriate bonding forces to prevent bending and maintain alignment
Data Source
AI summary
Positive electrode; negative electrode; and an electrode assembly comprising a separator provided between the positive electrode and negative electrode, wherein the separator has a wet adhesion to the negative electrode of 1.5 gf/20 mm or more and 15 gf/20 mm or less, and a secondary battery comprising the same. When the wet adhesion of the separator of the electrode assembly to the negative electrode satisfies the above range, distortion of the electrode assembly is effectively prevented before impregnation with the electrolyte solution, and at the same time, after impregnation with the electrolyte solution, the bending phenomenon after activation of the electrode assembly and the secondary battery including it is further reduced, and it can be suppressed effectively.