Secondary Battery Electrode Layout to Prevent Lithium Deposition
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Solution Overview
Problem
Existing secondary batteries face limitations in capacity and energy density, particularly due to lithium deposition issues in the negative electrode sheet, which compromises safety and efficiency.
Innovation Solution
The design includes a negative electrode sheet with a thinned region and a protruding portion of the positive active material layer, with a controlled thinning depth and thickness uniformity, ensuring the negative electrode sheet's capacity is maximized while preventing lithium deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative active material layer is made thinner to increase energy density, then the energy density is improved, but the capacity limit of the negative electrode sheet is reduced and lithium deposition risk increases
Solution Approach 1:
The negative active material layer is designed with non-uniform thickness: a thinned region (5-15 μm) at the overlapping area with positive electrode and a straight region (15-25 μm) at the non-overlapping area. This local quality variation allows increased energy density in the overlapping region while maintaining sufficient capacity in the non-overlapping region to prevent lithium deposition.
2Reliability
If the negative active material layer thickness is increased to improve capacity, then the capacity limit is improved, but the energy density is reduced
Solution Approach 1:
The thickness variation of the negative active material layer creates different functional zones: the thinned region maximizes energy density in the overlapping area, while the straight region provides sufficient capacity buffer in the non-overlapping area to prevent lithium deposition during charging.
3Productivity
If the positive active material layer has a protruding portion extending beyond the negative electrode, then the capacity utilization is improved, but the structural complexity increases
Solution Approach 1:
The positive active material layer extends beyond the negative electrode sheet in the lateral dimension, creating a protruding portion that overlaps with the thinned region. This dimensional extension allows the positive electrode to fully utilize the increased capacity of the negative electrode without requiring complex three-dimensional structures.
Data Source
AI summary
A secondary battery, a battery assembly, and an electronic device are provided. The secondary battery includes a negative electrode sheet, a positive electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The negative electrode sheet includes the negative active material layer includes a negative straight region and a negative thinned region located at one end of the negative straight region in a first direction. The positive electrode sheet includes the positive active material layer includes a positive straight region and a positive thinned region located at one end of the positive straight region away from the first direction. In the first direction, the positive active material layer includes a protruding portion that extends beyond the negative straight region. The protruding portion overlaps with an orthogonal projection of the negative thinned region in a second direction perpendicular to the first direction.