Wound Electrode Assembly Layout to Limit Lithium Plating at Corners
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving both improved energy density and reducing lithium ion precipitation on the negative electrode sheet during charging.
Innovation Solution
The electrode assembly is designed with a cuboid cell case that accommodates a wound assembly of positive and negative electrode sheets, where the positive electrode current collector at the corners has exposed portions without active material layers, and the negative electrode current collector at the corners is covered with active material layers, along with specific coating methods for the active material layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the wound electrode assembly is designed with a rectangular shape to reduce dead space in the battery case, then the energy density is improved, but lithium ions may precipitate onto the negative electrode sheet at the corner portions during charging
Solution Approach 1:
The patent applies local quality by creating a positive electrode exposed portion specifically at the corner portions of the electrode assembly, where the positive electrode active material layer is intentionally omitted. This localized modification addresses the lithium ion precipitation problem at corners without affecting the overall rectangular shape and energy density of the assembly. The exposed positive electrode current collector at corners provides a different local structure that prevents harmful lithium ion deposition while maintaining the beneficial rectangular wound configuration.
2Ease of manufacture
If the positive electrode active material layer is continuously coated on the positive electrode current collector, then the electrode structure is simple and manufacturing is easy, but the corner portions cannot prevent lithium ion precipitation
Solution Approach 1:
The patent applies segmentation by dividing the positive electrode active material layer coating into two regions: a continuous coating in the main body portions and an interrupted coating at the corner portions. This segmentation allows the manufacturing process to maintain simplicity through continuous coating methods while creating the necessary exposed portions at corners to prevent lithium ion precipitation. The active material layer is selectively omitted at corners through controlled interruption of the coating process.
Solution Approach 2:
The patent applies preliminary action by pre-defining the corner portions as regions where the positive electrode active material layer should not be coated during the manufacturing process. This preliminary designation of corner areas allows the continuous coating process to be easily controlled to skip these specific regions, thereby preventing lithium ion precipitation before charging occurs. The exposed positive electrode current collector at corners is created during the coating stage itself.
Data Source
AI summary
An electricity storage cell includes: an electrode assembly configured of a wound assembly including a positive electrode sheet and a negative electrode sheet that are wound through intermediation of a separator; and a cell case that accommodates the electrode assembly. The positive electrode sheet includes a positive electrode current collector, an inner positive electrode active material layer, and an outer positive electrode active material layer. The negative electrode sheet includes a negative electrode current collector, an inner negative electrode active material layer, and an outer negative electrode active material layer. The cell case is formed in a cuboid shape. The electrode assembly includes four corner portions. The positive electrode current collector at the corner portion includes a positive electrode exposed portion. The negative electrode current collector at the corner portion includes only a negative electrode covered portion.