Wound Nonaqueous Battery Electrode Layout for High-Resistance Control
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Solution Overview
Problem
Nonaqueous electrolyte solution secondary batteries face challenges in reducing the resistance of the negative electrode active material layer, particularly due to the formation of high-resistance regions which can lead to a drastic decrease in battery characteristics, as the electrolyte solution permeation is limited to the central part of the wound electrode body, resulting in uneven film formation and increased resistance.
Innovation Solution
The battery design includes a wound electrode body with a negative electrode active material layer that has a first high-resistance region extending from the end towards the center, with a controlled length ratio (L1/La) of 0.35 or less, preventing overlap with central high-resistance regions and suppressing the formation of ultrahigh-resistance areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving 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 bending radius and bending position of negative electrode tabs to specifically manage the formation and distribution of high-resistance regions. By making the high-resistance region length L1 satisfy L1/La ≤ 0.35, the invention ensures that high-resistance regions do not overlap in the central part, thereby maintaining acceptable electrical performance while achieving compact battery design through stacked and bent tabs
2Device complexity
If the nonaqueous electrolyte solution is supplied from only both end parts in the winding axis direction, then the battery structure is simplified, but the electrolyte solution permeates less easily into the central part resulting in high resistance
Solution Approach 1:
The patent applies preliminary action by controlling the bending process of negative electrode tabs to pre-determine the position and extent of high-resistance region formation. By setting L1/La ≤ 0.35 before battery operation, the invention prevents overlap of high-resistance regions in the central part, thereby proactively addressing the permeation issue without modifying the electrolyte supply structure
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 formation of ultrahigh-resistance regions, thereby maintaining battery characteristics by ensuring adequate electrolyte solution permeation and uniform film formation across the negative electrode active material layer.
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
the nonaqueous electrolyte solution permeates less easily into a central part in the winding axis direction
Implementation Method 3
the nonaqueous electrolyte solution permeates less easily into a central part in the winding axis direction
Data Source
AI summary
A nonaqueous electrolyte solution secondary battery disclosed herein includes a wound electrode body including a positive electrode with a band shape and a negative electrode with a band shape. The negative electrode includes a negative electrode active material layer. The negative electrode active material layer includes a first high-resistance region extending from one end part toward a central part in a winding axis direction 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 is La and a length of the first high-resistance region is L1 in the winding axis direction, a ratio (L1/La) of the length L1 to the length La is 0.35 or less.