Wound Electrode Assembly With Lithium Pre-Intercalated End Regions
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Solution Overview
Problem
In lithium-ion secondary batteries, the unpaired regions of the negative electrode plate lead to lithium ion migration, resulting in 'dead lithium' formation, causing capacity loss and deteriorating cycle and storage performance, especially at high temperatures.
Innovation Solution
A wound electrode assembly with a negative electrode plate featuring active material layers in both paired and unpaired regions, where a metallic lithium layer is applied to the unpaired regions to form a pre-intercalation compound, reducing lithium migration and 'dead lithium' formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous coating electrode plates are used to improve production efficiency and reduce cost, then productivity increases, but unpaired regions form at the ends of the wound negative electrode plate causing lithium migration and dead lithium formation
Solution Approach 1:
The patent applies different treatments to different regions of the negative electrode plate. Specifically, the unpaired regions at both ends of the wound negative electrode plate are coated with a lithium-containing coating layer, while the paired regions maintain the original electrode structure. This local differentiation prevents lithium migration in the unpaired regions without affecting the overall electrode design and production efficiency.
Solution Approach 2:
The lithium-containing coating layer is applied in advance to the unpaired regions before the battery assembly process. This preliminary action pre-establishes lithium reserves in the unpaired regions, preventing lithium migration and dead lithium formation during subsequent charge-discharge cycles, thereby improving cycle performance and storage performance.
2Ease of manufacture
If unpaired regions are present in the negative electrode plate, then the electrode structure is simpler and manufacturing is easier, but lithium ions migrate to unpaired regions forming dead lithium and causing capacity loss
Solution Approach 1:
The patent applies a lithium-containing coating layer specifically to the unpaired regions at both ends of the wound negative electrode plate, while leaving the paired regions unchanged. This localized treatment prevents lithium migration and dead lithium formation in the unpaired regions without complicating the overall manufacturing process, maintaining ease of manufacture while reducing capacity loss.
Solution Approach 2:
The patent converts the harmful effect of unpaired regions (which cause lithium migration and dead lithium formation) into a beneficial structure by coating them with lithium-containing material. The previously harmful unpaired regions now serve as lithium reserves that prevent lithium migration, transforming the defect into a feature that improves battery performance.
3Device complexity
If lithium migration occurs in unpaired regions, then the electrode structure remains simple, but storage performance deteriorates due to dead lithium formation, especially at high temperatures
Solution Approach 1:
The patent applies a lithium-containing coating layer specifically to the unpaired regions at both ends of the wound negative electrode plate, while maintaining the simple structure of the paired regions. This localized treatment prevents lithium migration and dead lithium formation in the unpaired regions, significantly improving storage performance especially at high temperatures without increasing overall electrode structure complexity.
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 solution effectively reduces capacity loss and enhances cycle and storage performance of lithium-ion secondary batteries, maintaining high performance even at elevated temperatures.
Implementation Method 1
a first metallic lithium layer is disposed on the surface of one or both of the two active material layers in the unpaired region, so that to form a first lithium pre-intercalation compound in either or both of the active material layers in the two unpaired region
Data Source
AI summary
The present application discloses a wound electrode assembly, wherein the negative electrode plate thereof includes a negative electrode current collector and a negative active material layer which includes a negative active material disposed on two opposite surfaces of the negative electrode current collector; and the two negative active material layers respectively include active an material layer in an unpaired region and an active material layer in a paired region distributed successively in the length direction of the negative electrode plate, and two active material layers in the unpaired regions are arranged at both ends in the length direction of the negative electrode plate, and a first metallic lithium layer is disposed on the surface of one or both of the active material layers in the unpaired regions, so that to form a first lithium pre-intercalation compound in either or both of the active material layers in the unpaired regions.