Battery Cell Frames Equalize Pressure and Conduct Heat
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Solution Overview
Problem
Battery modules in electric vehicles face performance degradation due to unequal temperature and pressure between battery cells, leading to reduced charge transfer and overall module performance.
Innovation Solution
A lithium ion battery module with a cell assembly that includes pouch battery cells held by cell frames, thermally conductive sheets, and end plates to equalize pressure and facilitate heat dissipation, using a thermally conductive base and thermal pads for efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If battery cells are assembled in a battery module without equalization mechanisms, then the battery module can be manufactured with simpler structure, but unequal temperature and pressure between battery cells leads to performance degradation
Solution Approach 1:
The cell assembly is divided into multiple cell assemblies, each containing a specific number of battery cells (e.g., three cells per assembly). This segmentation allows for localized equalization mechanisms within each assembly while maintaining overall module performance. The frame structure is also segmented into multiple frames that can independently apply compression forces to different cell groups.
Solution Approach 2:
A frame structure acts as an intermediary between the battery cells and the compression mechanism. The frame includes compression elements that distribute pressure evenly across multiple cells, and thermal elements that facilitate heat transfer from cells to cooling structures. This intermediary structure enables equalization of temperature and pressure without requiring direct modification of each individual cell.
2Reliability
If compression force is applied to battery cells to maintain contact, then charge transfer between cells is improved, but unequal pressure distribution causes some cells to experience excessive compression
Solution Approach 1:
The compression force is applied locally through individual compression elements on each frame, allowing for optimized pressure distribution. Each compression element can be independently adjusted or designed with different properties to match the specific requirements of the cells it contacts. This local quality approach ensures that each cell receives appropriate compression without over-compressing adjacent cells.
Solution Approach 2:
The compression force parameters are optimized by adjusting the stiffness, geometry, and material properties of the compression elements. The frames are designed with specific elastic moduli and structural configurations that allow them to distribute compression forces according to the actual needs of the battery cells during operation, maintaining optimal pressure without excessive force on any single cell.
3Temperature
If thermal management structures are added to equalize temperature, then battery cell temperature uniformity is improved, but heat dissipation efficiency may be reduced due to additional thermal resistance
Solution Approach 1:
The frame structure merges multiple functions into a single component: mechanical support, compression force application, and thermal conduction. By integrating thermal management features directly into the compression frames, the patent eliminates separate thermal management components that would add thermal resistance. The frames conduct heat from the battery cells to cooling structures while simultaneously providing mechanical compression.
Solution Approach 2:
The frame structure serves multiple purposes: it provides mechanical support for the cells, applies compression force to maintain contact between cells and electrodes, and acts as a thermal conduction path for heat dissipation. This multi-functionality reduces the need for additional dedicated thermal management components, thereby minimizing thermal resistance while achieving temperature equalization.
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
The solution ensures consistent pressure and temperature across battery cells, enhancing performance and longevity by maintaining equalization of pressure and temperature, thereby improving the overall efficiency and reliability of the battery module.
Implementation Method 1
thermally conductive sheets interleaved with the plurality of battery cells... thermally conductive sheet includes a planar portion disposed between the battery cell and the adjacent cell... thermal pad in contact with the conductive base... epoxy layer disposed between the thermal pad and the cell assembly
Data Source
AI summary
A lithium ion battery module includes a housing having a thermally conductive base and a cell assembly disposed within the housing and comprising pouch battery cells, a plurality of layers interleaved with the pouch battery cells, and a pair of end plates disposed on opposite ends of the cell assembly to compress the pouch battery cells. The battery cells are held within the cell assembly by cell frames. Each cell frame is formed from two frame pieces. The plurality of layers comprises a plurality of foam sheets and a plurality of thermally conductive sheets. The foam sheets are configured to allow swelling of the pouch battery cells while enabling a substantially constant level of compression of the pouch battery cells by the pair of end plates. The thermally conductive sheets conduct heat from the battery cells toward the thermally conductive base of the housing.