Battery Pack Spacer Structure for Electrode Contraction
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Solution Overview
Problem
In battery packs, water infiltration through the sealing portion can react with lithium ions, causing electrode contraction and reducing the binding pressure, which makes it difficult to maintain appropriate inter-electrode distance and decreases the capacity maintenance rate.
Innovation Solution
The battery pack design includes a spacer with a top projection that presses the side wall of the adjacent battery cell at a position corresponding to the upper curved portion of the electrode body, increasing the binding pressure and maintaining the inter-electrode distance even with electrode contraction, and the projections are equal in height and extend continuously parallel to the upper edge of the flat portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the protrusions of the spacers are made elastically deformable in the arrangement direction of the battery cells, then the binding force applied to the side wall of the case is reduced, but this allows the spacer to accommodate electrode contraction; however, this makes it difficult to maintain the appropriate inter-electrode distance when water infiltration causes electrode contraction
Solution Approach 1:
The spacer is designed with different regional properties: the pressing portion has high rigidity to maintain binding pressure against electrode contraction, while the cushioning portion has elastic deformability to accommodate volume changes. This local differentiation resolves the contradiction by providing both stability and adaptability in appropriate locations.
Solution Approach 2:
The spacer is divided into functionally distinct segments: a pressing portion with pressing protrusions that maintain inter-electrode distance, and a cushioning portion that absorbs expansion/contraction forces. This segmentation allows each part to specialize in its function, resolving the contradiction between maintaining distance and accommodating contraction.
2Force
If the protrusions press the side wall of the case at the position corresponding to the upper edge of the electrode body, then the binding pressure is maintained, but water infiltration causes electrode contraction that reduces this binding pressure
Solution Approach 1:
The cushioning portion is designed in advance to compensate for future electrode contraction caused by water infiltration. When contraction occurs, the cushioning portion absorbs the volume change, preventing loss of binding pressure at the pressing portion and maintaining stable electrode compression throughout the battery's service life.
3Force
If the spacer presses the side wall at multiple positions, then the binding pressure is distributed, but the binding pressure at the upper edge position is reduced
Solution Approach 1:
The spacer is segmented into a pressing portion with concentrated pressing protrusions at the upper edge, and a cushioning portion that distributes compression forces along the electrode body. This segmentation ensures the pressing portion maintains high binding pressure where needed while the cushioning portion provides distributed support.
Data Source
AI summary
A battery pack includes battery cells and a spacer. Each battery cell includes an electrode body and a case accommodating the electrode body in a state sealed by a sealing portion. The battery cells are arranged in an arrangement direction. The spacer is arranged between the case of one of the battery cells and the case of an adjacent battery cell. The battery cells are bound together in a state in which a binding pressure is applied to the battery cells. The electrode body includes a flat portion. The spacer includes a base plate and projections projecting from the base plate toward the case of the adjacent battery cell. The projections include a top projection that presses the case of the adjacent battery cell at a position located upward from an upper edge of the flat portion where the sealing portion is the closest.