Separator Tension Modulus for Battery Cycle Life
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Solution Overview
Problem
Nonaqueous electrolyte batteries face challenges in extending charge-and-discharge cycle life due to thin separators leading to internal short circuits and uneven current distribution, which limits their capacity and performance.
Innovation Solution
A nonaqueous electrolyte battery design featuring a porous separator with a tension modulus ranging from 200 to 2000 N/mm² in the winding direction, allowing for flexibility to absorb electrode expansion and contraction, and a mode diameter of 1 to 10 µm to prevent internal short circuits, thereby improving charge-and-discharge cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator thickness is reduced to increase battery capacity, then the battery capacity increases, but internal short circuits occur and charge-and-discharge cycle life becomes short
Solution Approach 1:
The patent changes the mechanical parameter (tension modulus) of the separator from conventional low values to specifically 200-2000 N/mm² in the winding direction. This parameter change allows the separator to maintain adequate thickness for safety while providing sufficient flexibility to absorb electrode expansion/contraction, thereby preventing internal short circuits and improving cycle life despite increased capacity requirements.
2Quantity of substance
If the separator thickness is reduced, then the battery capacity increases, but the separator cannot sufficiently absorb electrode expansion and contraction
Solution Approach 1:
The patent modifies the tension modulus parameter of the separator to 200-2000 N/mm² in the winding direction, enabling the separator to sufficiently absorb electrode expansion and contraction even when thickness is reduced, thus maintaining adaptability while increasing battery capacity.
Solution Approach 2:
The patent applies different mechanical properties to different directions of the separator by specifying tension modulus in the winding direction (200-2000 N/mm²) while maintaining appropriate properties in other directions, allowing the separator to locally adapt to electrode expansion/contraction forces.
3Quantity of substance
If the separator thickness is reduced, then the battery capacity increases, but force is partially applied to electrodes generating large difference in current distribution
Solution Approach 1:
The patent changes the tension modulus parameter to 200-2000 N/mm² in the winding direction, which provides sufficient flexibility to the separator to accommodate electrode expansion and contraction without applying excessive force to the electrodes. This maintains uniform current distribution across the electrode surface even when separator thickness is reduced for increased capacity.
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 improved separator design enhances the battery's charge-and-discharge cycle life by dispersing forces applied to electrodes, preventing internal short circuits and ensuring uniform current distribution, leading to higher capacity retention ratios over multiple cycles.
Implementation Method 1
a porous separator with a tension modulus ranging from 200 to 2000 N/mm² in the winding direction, allowing for flexibility to absorb electrode expansion and contraction
Implementation Method 2
a porous separator with a tension modulus ranging from 200 to 2000 N/mm² in the winding direction and a mode diameter of 1 to 10 µm to prevent internal short circuits
Data Source
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AI summary
According to an embodiment, a nonaqueous electrolyte battery including an electrode group and a nonaqueous electrolyte is provided. The electrode group is formed by winding a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode. The tension modulus of the separator in the winding direction is within a range of 200 (N/mm2) to 2,000 (N/mm2) .