Secondary battery
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Solution Overview
Problem
The expansion of the negative electrode mixture layer during charging and discharging in secondary batteries leads to increased stress and deformation of electrode plates, which can cause performance decline and internal short-circuits.
Innovation Solution
A secondary battery design with a separator configuration where the coefficient of static friction of the surface opposing the positive electrode on the winding inner side is greater than that of the surface opposing the positive electrode on the winding outer side, specifically a ratio of 1.3 or higher, to balance the forces of friction and prevent plate deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative electrode mixture layer is expanded to increase battery capacity, then the battery capacity increases, but the stress inside the battery increases and electrode plates may deform
Solution Approach 1:
The patent applies local quality by making the two separator surfaces have different coefficients of static friction. The first separator surface (winding outer side) has a higher coefficient (μ1 ≥ 0.3) than the second separator surface (winding inner side, μ2 < 0.3). This asymmetric friction characteristic locally compensates for the stress distribution caused by negative electrode expansion, preventing electrode plate deformation while maintaining high battery capacity.
2Ease of manufacture
If identical separators are used on both sides of the positive electrode, then the manufacturing process is simple, but the electrode plates deform due to unbalanced friction forces during negative electrode expansion
Solution Approach 1:
The patent implements local quality by differentiating the friction characteristics of the two separator surfaces. The first separator surface is designed with higher friction (μ1 ≥ 0.3) and the second with lower friction (μ2 < 0.3), creating an asymmetric structure that actively counteracts the unbalanced stress from negative electrode expansion, thereby preventing electrode deformation.
Solution Approach 2:
The patent applies asymmetry by making the coefficients of static friction of the two separator surfaces unequal. Specifically, the ratio μ1/μ2 is set to 0.2 or more, with μ1 ≥ 0.3 and μ2 < 0.3. This asymmetric friction design creates a compensatory force distribution that balances the stress on the positive electrode during charging and discharging, preventing electrode plate deformation.
3Force
If the coefficient of static friction of the separator surface on the winding outer side is increased, then the friction force on the positive electrode surface is increased to counteract stress, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by differentiating the friction characteristics of the two separator surfaces. The first separator surface (winding outer side) has a higher coefficient (μ1 ≥ 0.3) than the second separator surface (winding inner side, μ2 < 0.3). This asymmetric friction characteristic locally compensates for the stress distribution caused by negative electrode expansion, preventing electrode plate deformation while maintaining high battery capacity.
Solution Approach 2:
The patent applies asymmetry by making the coefficients of static friction of the two separator surfaces unequal. Specifically, the ratio μ1/μ2 is set to 0.2 or more, with μ1 ≥ 0.3 and μ2 < 0.3. This asymmetric friction design creates a compensatory force distribution that balances the stress on the positive electrode during charging and discharging, preventing electrode plate deformation.
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 effectively suppresses electrode plate deformation during charging and discharging, maintaining battery performance and preventing internal short-circuits.
Implementation Method 1
a ratio of a coefficient of static friction of a surface of the first separator on the winding outer side in contact with the first surface of the positive electrode to a coefficient of static friction of a surface of the second separator on the winding inner side in contact with the second surface of the positive electrode is greater than or equal to 1.3
Data Source
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AI summary
A secondary battery (10) according to one embodiment of the present disclosure is provided with a wound electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) interposed therebetween. The secondary battery (10) is characterized in that the separator (13) includes a first separator (31) facing a first surface (11A) on the winding inner side of the positive electrode (11), and a second separator (32) facing a second surface (11B) on the winding outer side of the positive electrode (11), the ratio of the static friction coefficient of the surface on the winding outer side of the first separator (31) in contact with the first surface (11A) of the positive electrode (11) to the static friction coefficient of the surface on the winding inner side of the second separator (32) in contact with the second surface (11B) of the positive electrode (11) being 1.3 or more.