Wound Li-Ion Electrode Layout to Prevent Ultrahigh-Resistance Regions
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Solution Overview
Problem
Nonaqueous electrolyte solution secondary batteries face issues with high resistance in the central part of the wound electrode body due to inadequate permeation of the electrolyte solution, leading to the formation of ultrahigh-resistance regions, which can drastically decrease battery characteristics.
Innovation Solution
The battery design includes a negative electrode active material layer with a first high-resistance region extending from the end towards the center, where the length of this region is limited to 0.35 or less of the total electrode material layer length, preventing overlap with central high-resistance areas and thus suppressing the formation of ultrahigh-resistance regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If multiple negative electrode tabs are stacked and bent to reduce battery size, then volume energy density is improved, but a stripe-shaped high-resistance region is formed in the negative electrode active material layer
Solution Approach 1:
The patent applies local quality by controlling the resistance characteristics in specific regions of the negative electrode active material layer. By managing the extent of the first high-resistance region (L1/La ≤ 0.35), the invention creates a localized resistance distribution that prevents ultrahigh-resistance regions while maintaining low resistance in critical areas, thus resolving the contradiction between compact battery design and electrode resistance.
2Quantity of substance
If the battery capacity is increased, then energy storage is improved, but the nonaqueous electrolyte solution permeates less easily into the central part, forming high-resistance regions
Solution Approach 1:
The patent applies parameter changes by controlling the ratio L1/La of the first high-resistance region length to the total electrode material layer length, limiting it to 0.35 or less. This parameter control ensures that even in high-capacity batteries with longer electrode layers, the electrolyte solution can still adequately permeate the central regions, preventing ultrahigh-resistance region formation while maintaining high capacity.
3Ease of manufacture
If the first high-resistance region extends toward the central part, then the negative electrode tabs can be connected, but ultrahigh-resistance regions may form when the high-resistance region reaches the central part
Solution Approach 1:
The patent applies local quality by spatially separating the tab connection region from the central high-resistance region. By limiting L1/La ≤ 0.35, the first high-resistance region is confined to the peripheral areas, allowing tab connections to be made in low-resistance zones while preventing overlap with central high-resistance regions, thus avoiding ultrahigh-resistance region formation.
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 reduces the likelihood of ultrahigh-resistance region formation, thereby maintaining battery performance and preventing a drastic decrease in characteristics.
Implementation Method 1
a part of the nonaqueous electrolyte solution is normally decomposed at initial charging and a film including a decomposition product thereof (solid electrolyte interface film: SEI film) is formed on a surface of the negative electrode active material layer
Implementation Method 2
there is still room for improvement in the aforementioned technique. That is to say, in the nonaqueous electrolyte solution secondary battery, a part of the nonaqueous electrolyte solution is normally decomposed at initial charging and a film including a decomposition product thereof (solid electrolyte interface film: SEI film) is formed on a surface of the negative electrode active material layer
Data Source
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AI summary
A nonaqueous electrolyte solution secondary battery (100) disclosed herein includes a wound electrode body (20) including a positive electrode (22) with a band shape and a negative electrode (24) with a band shape. The negative electrode (24) includes a negative electrode active material layer (24a). The negative electrode active material layer (24a) includes a first high-resistance region (A1) extending from one end part toward a central part in a winding axis direction (Y) and having a resistance value that is 1.5 times or more higher than that in a periphery. When a length of the negative electrode active material layer (24a) is La and a length of the first high-resistance region (A1) is L1 in the winding axis direction (Y), a ratio (L1/La) of the length L1 to the length La is 0.35 or less.