Wound Secondary Battery Case Pressing for Lithium Plating Control
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Solution Overview
Problem
There is an increasing demand for secondary batteries with improved durability and long lifespan, and a need to inhibit the precipitation of metallic lithium more effectively.
Innovation Solution
A secondary battery configuration that includes a flat wound electrode body with a protruding portion or spacer to intensively press the insufficiently stacked region, preventing local increases in inter-electrode distance and inhibiting metallic lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
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 the insufficiently stacked region experiences pressing failure leading to metallic lithium precipitation
Solution Approach 1:
The patent applies different pressing intensities to different regions of the wound electrode body. The protruding portion creates a localized high-pressure zone specifically at the insufficiently stacked region, while other regions maintain standard pressing pressure. This local quality differentiation ensures adequate pressure is applied where needed without over-pressing other areas, preventing metallic lithium precipitation while maintaining overall battery capacity.
Solution Approach 2:
The protruding portion is formed on the battery case before the wound electrode body is installed, creating a pre-positioned pressing structure. This preliminary action ensures that when the electrode body is placed in the battery case, the insufficiently stacked region is immediately and uniformly pressed, preventing pressing failure and metallic lithium precipitation before the battery operates.
2Shape
If the negative electrode starting end portion is extended toward the curved portion, then the thickness variation of the flat portion is reduced, but an insufficiently stacked region is created in the flat portion
Solution Approach 1:
The patent creates a localized pressing structure (protruding portion) that specifically addresses the insufficiently stacked region. This allows the negative electrode to be extended for better thickness uniformity while the protruding portion compensates for the localized stacking deficiency, maintaining both shape improvement and manufacturing precision.
Solution Approach 2:
The protruding portion acts as an intermediary element between the battery case and the insufficiently stacked region. It transfers and concentrates the pressing force precisely where needed, mediating between the extended electrode configuration and the requirement for adequate stacking pressure, thus resolving the contradiction between thickness uniformity and stacking precision.
Data Source
AI summary
According to the present disclosure, a secondary battery capable of inhibiting precipitation of metallic lithium is provided. A secondary battery disclosed herein includes a wound electrode body, and a battery case. An insufficiently stacked region is formed in the vicinity of a positive electrode starting end portion in a flat portion of the electrode body. In the insufficiently stacked region, the total number of layers of a positive electrode plate and a negative electrode plate is smaller than in other regions in the flat portion. In addition, in the secondary battery, a protruding portion protruding toward at least a part of the insufficiently stacked region is formed on an inner surface of the battery case. As a result, it is possible to prevent pressing failure in the insufficiently stacked region and inhibit precipitation of metal Li due to a local increase in an inter-electrode distance.