Battery Pack Thermal Management Using Flexible Graphite Heat Spreaders
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Solution Overview
Problem
Prismatic lithium-ion battery packs face challenges in thermal management, particularly in maintaining optimal operating temperatures, which affects their efficiency, lifespan, and capacity due to the stacked configuration that hinders effective heat transfer from interior cells to exterior surfaces.
Innovation Solution
Incorporating flexible graphite heat spreaders between prismatic lithium-ion cells in a stacked configuration and a heat sink with enhanced thermal conductivity, where the heat spreaders contact at least 30% of the heat sink's thickness, facilitating uniform heat distribution and transfer to the surroundings or a heat sink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If prismatic lithium-ion battery cells are arranged in a stacked configuration to increase capacity, then the battery pack achieves greater energy storage capacity, but heat transfer from interior cells to exterior surfaces is hindered
Solution Approach 1:
Heat spreaders made from flexible graphite sheets are introduced as intermediary components between the battery cells and the heat sink. These heat spreaders facilitate thermal energy transfer from the interior cells to the exterior heat sink, resolving the heat transfer bottleneck created by the stacked configuration while preserving the high capacity benefits.
Solution Approach 2:
The patent extends thermal management from a two-dimensional surface contact to a three-dimensional heat sink structure that penetrates through the battery pack. The heat sink includes a thru-thickness channel that allows heat to be extracted from the interior of the stacked configuration, effectively adding a third dimension to heat dissipation pathways.
2Volume of moving object
If heat spreaders are made thin to reduce space occupation, then the battery pack density is improved, but heat transfer effectiveness may be reduced
Solution Approach 1:
The heat spreaders are constructed from flexible graphite, a material with exceptional in-plane thermal conductivity. This composite material property allows the heat spreaders to achieve high heat transfer effectiveness despite their thin profile, as the graphite structure efficiently conducts heat laterally across the cell surfaces before transferring it to the heat sink.
3Temperature
If the heat sink is made larger to improve heat dissipation, then thermal management is enhanced, but the battery pack volume increases
Solution Approach 1:
The heat sink design incorporates a thru-thickness channel that penetrates through the battery pack in the third dimension. This allows heat to be extracted from the interior cells without requiring a larger external heat sink footprint, as the heat dissipation pathway extends vertically through the pack rather than requiring additional lateral space.
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 configuration improves thermal management by reducing thermal gradients, extending the battery pack's life cycle, maintaining optimal operating temperatures, and enhancing energy storage capacity and efficiency.
Implementation Method 1
Incorporating flexible graphite heat spreaders between prismatic lithium-ion cells in a stacked configuration and a heat sink with enhanced thermal conductivity, where the heat spreaders contact at least 30% of the heat sink's thickness, facilitating uniform heat distribution and transfer to the surroundings or a heat sink
Data Source
AI summary
A battery pack includes a plurality of prismatic format batteries in a stacked configuration. Flexible graphite sheet heat spreaders are interposed between adjacent prismatic batteries in the stack. A heat sink extends the length of the stack of prismatic format batteries. Both heat spreader major surfaces contact the heat sink at contact areas and thereby extend into the heat sink by at least 30 percent of the thru-thickness of the heat sink.