Non-Aqueous Battery Electrode Coating for Stable Can Contact
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Solution Overview
Problem
The narrow clearance between the electrode assembly and the outer housing can in non-aqueous electrolyte secondary batteries leads to assembly failures and significant deterioration due to the expansion and contraction of the negative electrode mixture layer during charge-discharge cycles, resulting in poor electrical connections.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a wound electrode assembly with a negative electrode mixture layer having a larger charge expansion coefficient on its outermost circumference, ensuring stable contact between the negative electrode current collector and the outer housing can, while maintaining a sufficient clearance during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clearance between the electrode assembly and the inner face of the outer housing can is narrowed to ensure contact of the exposed surface of the negative electrode current collector with the inner face of the outer housing can, then electrical connection is improved, but insertion during battery manufacturing is likely to fail and productivity decreases
Solution Approach 1:
The negative electrode mixture layer is designed with different properties in different regions: the first negative electrode mixture layer (at the outermost circumference) has a larger charge expansion coefficient, while the second negative electrode mixture layer (inner region) has a smaller charge expansion coefficient. This local differentiation allows the outer region to expand sufficiently during charging to ensure contact with the outer housing can, while the inner region maintains structural stability, thus resolving the contradiction between ensuring electrical connection and maintaining insertion feasibility.
2Reliability
If the negative electrode mixture layer is allowed to expand significantly during charge to strengthen electrical connection, then contact with the outer housing can is improved, but deterioration due to charge-discharge cycles increases
Solution Approach 1:
By creating a spatial gradient in the charge expansion coefficient of the negative electrode mixture layer, the patent allows only the outermost region (first negative electrode mixture layer) to undergo significant expansion during charging to ensure contact with the outer housing can. The inner region (second negative electrode mixture layer) has a smaller expansion coefficient, which reduces overall expansion and contraction stress during charge-discharge cycles, thereby minimizing deterioration and improving cycle life while still achieving reliable electrical connection.
Solution Approach 2:
The negative electrode mixture layer is segmented into two distinct regions with different functional characteristics: the first layer at the outermost circumference responsible for expansion and contact establishment, and the second layer in the inner region responsible for maintaining structural integrity. This segmentation allows each region to perform its specific function optimally, resolving the contradiction between achieving good contact and maintaining long-term durability.
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 enhances assembly productivity and reduces deterioration, achieving a robust electrical connection and maintaining battery performance across charge-discharge cycles.
Implementation Method 1
the negative electrode mixture layer expands during charge
Data Source
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AI summary
The purpose of the present invention is to provide a non-aqueous electrolytic secondary battery in which electrical connection between an exposed surface of a negative current collector at the outermost periphery of an electrode assembly and the inner surface of an outer can is ensured. A non-aqueous electrolytic secondary battery according to an embodiment of the present disclosure is provided with a wound electrode assembly. A negative electrode (12) comprises a sheet-like negative current collector (40) having a negative electrode mixture layer (42) formed on a surface thereof, and includes a double-side coating portion in which the negative electrode mixture layer (42) is formed on both sides of the negative current collector (40), and a single-side coating portion in which the negative electrode mixture layer (42B) is formed on one side of the negative current collector. At least a part of the single-side coating portion is disposed at the outermost periphery of the electrode assembly. At least a part of an exposed surface of the negative current collector in the single-side coating portion is in contact with the inner surface of an outer can. The charge expansion ratio of the negative electrode mixture layer (42B) in the single-side coating portion is greater than the charge expansion ratio of the negative electrode mixture layer (42A) in the double-side coating portion.