Flat Wound Electrode Body Preventing Lithium Precipitation
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Solution Overview
Problem
Secondary batteries face challenges in inhibiting the precipitation of metallic lithium due to local increases in inter-electrode distance, leading to reduced durability and lifespan, particularly in regions with insufficient layers of electrode plates near curved portions.
Innovation Solution
The configuration of a flat wound electrode body with overlapping regions of the positive and negative electrode plates, along with a porous separator, ensures uniform surface pressure distribution and prevents partial pressing failures, thereby inhibiting metallic lithium precipitation. This includes adjusting the positions of electrode starting and terminating end portions and using a porous separator with a specific porosity to absorb thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the flat portion of the wound electrode body is pressed from the outside to reduce inter-electrode distance, then the battery capacity is improved, but pressing failure occurs in thinner regions near curved portions leading to metallic lithium precipitation
Solution Approach 1:
The patent applies local quality by creating a stepped configuration where the electrode plates have different heights in different regions. Specifically, the electrode plates are configured to have a first height in a first region and a second height different from the first height in a second region. This allows the pressing force to be distributed differently across regions, preventing pressing failure in thinner areas near curved portions while still achieving adequate compression in thicker regions, thereby maintaining uniform pressing without compromising battery capacity.
2Volume of moving object
If the electrode plates are made thinner to reduce overall battery thickness, then the battery size is reduced, but the inter-electrode distance becomes insufficient leading to metallic lithium precipitation
Solution Approach 1:
The patent implements local quality by configuring electrode plates with varying heights across different regions. The electrode plates have a first height in a first region and a second height in a second region, allowing precise control of inter-electrode distance in each region. This stepped configuration ensures that even though the overall battery thickness is reduced, the inter-electrode distance is maintained at appropriate levels in all regions, preventing metallic lithium precipitation while achieving compact battery size.
3Ease of manufacture
If the negative electrode starting end portion is folded back to prevent overlap with positive electrode, then the electrode arrangement is optimized, but variation in thickness of flat portion increases
Solution Approach 1:
The patent applies local quality by creating a stepped configuration that accommodates the folded negative electrode starting end portion. The electrode plates have different heights in different regions, with the stepped configuration specifically designed to handle the folded portion. This allows the negative electrode to be folded back to prevent overlap with the positive electrode while the stepped structure compensates for the resulting thickness variation, maintaining overall shape uniformity and facilitating manufacturing.
Data Source
AI summary
According to the present disclosure, a secondary battery capable of inhibiting precipitation of metallic lithium is provided. The secondary battery disclosed herein includes a flat wound electrode body. A positive electrode starting end portion inside the electrode body has a first region extending along a flat portion of the electrode body. On the other hand, a negative electrode starting end portion inside the electrode body has a second region extending along the flat portion, a folded portion folded back from an end portion of the second region, and a third region extending from an end portion of the folded portion. In addition, the electrode body has an electrode starting end stacked portion in which the first region, the second region, and the third region overlap. According to such a configuration, it is possible to prevent a partial pressing failure from occurring and inhibit the precipitation of metallic lithium.