Battery Module Mid-Plate Structure for Cell Stack Stiffness
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Solution Overview
Problem
Increasing the number of battery cells in a cell stack leads to increased dimension in the stacking direction, making it prone to bending deformation and distortion due to individual cell differences, while adding stiffeners to enhance stiffness results in a decrease in energy density.
Innovation Solution
A battery module design incorporating a mid-plate with recesses and belts to support the cell stack, along with stiffener plates, which increases stiffness without increasing size or weight, and accommodates additional components within the module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a battery module contains a large number of battery cells (e.g., 96 cells), then the battery pack capacity increases, but the distance between terminals increases leading to higher internal resistance and heat generation
Solution Approach 1:
The battery module is divided into multiple battery cell groups, where each group contains a subset of battery cells (e.g., 24 cells per group in a 96-cell module). This segmentation allows terminals to be positioned closer within each group, reducing internal resistance and heat generation while maintaining the overall high capacity of the complete module through the combination of multiple groups.
2Reliability
If battery cells are tightly fixed to prevent movement, then connection reliability improves, but stress concentration occurs at connection parts during thermal expansion
Solution Approach 1:
The battery holder is designed with differentiated local properties: rigid portions provide strong fixing force at critical connection locations to ensure reliable electrical connections, while elastic portions provide flexible support at other areas to accommodate thermal expansion and contraction. This local quality differentiation allows the structure to maintain connection reliability while preventing stress concentration that would occur with uniform rigid fixation throughout.
3Manufacturing precision
If rigid fixing structure is used to secure battery cells, then positioning precision improves, but stress concentration occurs during thermal expansion and contraction
Solution Approach 1:
The battery holder incorporates rigid portions strategically positioned to provide precise positioning and stable electrical connections where required, while elastic portions are positioned to absorb thermal expansion and contraction stresses. This local differentiation of rigidity allows the structure to achieve manufacturing precision for battery cell positioning while simultaneously resisting stress during thermal cycles through the compliant elastic regions.
4Productivity
If equal current collection is required from all battery cells, then battery performance optimizes, but connection structure complexity increases
Solution Approach 1:
Multiple battery cells are electrically connected in parallel within each battery cell group, merging their current collection paths. This configuration naturally equalizes current distribution across all cells in the group while maintaining a relatively simple connection structure. The parallel connection architecture allows the battery module to achieve optimized discharge rates through aggregated current capacity without requiring complex individual cell management systems.
Data Source
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AI summary
A battery module (1) includes: a cell stack (2) in which multiple battery cells (2a) are stacked along a predetermined stacking direction (Do); a pair of end plates (3) disposed on both end faces of the cell stack (2) in the stacking direction (Do); and a mid-plate (4) disposed in an intermediate portion of the cell stack (2) in the stacking direction (Do). The mid-plate (4) has a pair of main faces (4a) each facing the battery cell (2a), multiple side faces (4b) each connecting outer edges of the pair of main faces (4a), and a recess (4d) extending in a cross direction Dw that intersects the stacking direction Do on at least one of the side faces (4b).