Lithium Battery Negative Electrode Protrusions for Expansion Control
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Solution Overview
Problem
Lithium secondary batteries with wound electrode groups face challenges in reducing negative electrode expansion during charging, leading to stress and uneven expansion due to the deposition of lithium metal, which affects discharge capacity and cycle characteristics.
Innovation Solution
The battery design incorporates a negative electrode current collector with protrusions on both surfaces, where the area rate of outer-circumference-side protrusions is greater than inner-circumference-side protrusions, creating spaces for lithium deposition and reducing stress, thereby minimizing expansion and enhancing charge-discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is deposited on the negative electrode during charging, then the battery capacity is increased, but the negative electrode expands and causes stress and deterioration of battery characteristics
Solution Approach 1:
The patent applies preliminary action by forming protrusions on the negative electrode current collector surface before lithium metal deposition. These protrusions pre-create spaces between them that accommodate lithium metal during charging, preventing the negative electrode from expanding and maintaining structural stability throughout charge-discharge cycles.
2Manufacturing precision
If the negative electrode current collector surface is made smooth, then lithium metal deposition is improved, but the battery characteristics deteriorate due to lack of space for lithium accommodation
Solution Approach 1:
The patent applies local quality by creating protrusions with specific geometric features (height, width, spacing) on the negative electrode current collector surface. These localized structures provide spaces for lithium metal accommodation while maintaining overall surface quality, ensuring both smooth lithium deposition and structural stability during operation.
3Stability of the object's composition
If protrusions are added to the negative electrode current collector, then spaces for lithium deposition are created and expansion is reduced, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the negative electrode current collector surface into multiple protrusions distributed across the surface. This segmentation creates numerous small spaces for lithium deposition throughout the electrode, effectively controlling expansion while maintaining a relatively simple overall structure that can be manufactured using conventional techniques.
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 negative electrode expansion, maintains high discharge capacity, and prevents lithium peeling, thereby improving the overall efficiency and longevity of the battery.
Implementation Method 1
Lithium metal is deposited on the negative electrode during charging, and the lithium metal is dissolved in the nonaqueous electrolyte during discharging
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A lithium secondary battery comprises an electrode group and a nonaqueous electrolyte having lithium-ion conductivity. A negative electrode current collector has a first surface facing outward of winding of the electrode group and a second surface facing inward of the winding of the electrode group. At least the first surface or the second surface includes a first region and a second region that is closer to an innermost circumference of the winding of the electrode group than the first region. Protrusions include outer-circumference-side protrusions disposed on the first region and inner-circumference-side protrusions disposed on the second region. In at least the first surface or the second surface, a first area rate is larger than a second area rate.