Battery Pack Thermal Management Using MFM-PCM Composite Blocks
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Solution Overview
Problem
High heat generation in lithium-ion battery packs during continuous high-current discharge leads to performance degradation, longevity issues, and safety concerns, particularly in space-limited assemblies where effective cooling is challenging, resulting in derating of discharge currents and increased cool-down times.
Innovation Solution
The integration of microfibrous media (MFM) with phase change materials (PCM) and active cooling structures within battery packs, where MFM is sintered with active cooling structures to enhance heat transfer, and multiple PCM layers with different melting points are used for thermal management and flame retardancy, optimizing heat dissipation and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If cells are discharged at high currents in a battery pack, then power output is improved, but heat generation increases causing safety issues and performance degradation
Solution Approach 1:
The patent utilizes the harmful heat generated during high-current discharge as a beneficial resource by incorporating phase change materials (PCMs) that absorb this heat through phase transition. The PCMs are positioned in thermal contact with the cells to capture and store the generated heat, thereby enabling high-power discharge while preventing thermal runaway and maintaining safety.
Solution Approach 2:
The patent employs phase change materials (PCMs) that undergo phase transitions (solid-liquid or liquid-gas) at specific temperatures to absorb and store the heat generated during high-current discharge. This phase transition mechanism provides passive thermal management, allowing the battery pack to maintain safe operating temperatures even under high-power conditions.
2Temperature
If traditional cooling tubes are used in battery packs, then heat dissipation is achieved, but device complexity and space requirements increase
Solution Approach 1:
The patent extracts the active cooling tubes from the thermal management system and replaces them with passive phase change materials. This removal of complex active cooling components simplifies the overall device structure while maintaining effective heat dissipation through the PCM's phase transition mechanism, thereby reducing device complexity and space requirements.
Solution Approach 2:
The phase change materials provide self-service thermal management by automatically absorbing heat through phase transition when temperature increases occur. This passive mechanism requires no external control systems, pumps, or complex infrastructure, thereby simplifying the device while achieving effective heat dissipation.
3Quantity of substance
If cells are closely packed to increase energy density, then space utilization is improved, but heat transfer and cooling become difficult
Solution Approach 1:
The patent nests the phase change materials within the battery pack structure in close proximity to the cells, effectively embedding the thermal management function within the energy storage structure itself. This nested arrangement allows close cell packing for high energy density while ensuring that PCMs are positioned to efficiently capture heat from multiple cells simultaneously.
Solution Approach 2:
The phase change materials act as thermal intermediaries between the closely packed cells, absorbing excess heat and preventing direct thermal coupling between adjacent cells. This intermediary function enables high energy density packing while maintaining effective heat transfer management through the PCM's heat absorption capacity.
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 significantly improves heat transfer efficiency, allowing higher discharge currents while maintaining safety, reducing derating and cool-down times, and providing effective thermal management and flame retardancy within battery packs.
Implementation Method 1
The MFM-PCM in the battery pack contain multiple blocks or sections with different functionalities. For example, one or more of the PCM in an MFM-PCM block may serve as a flame retardant to prevent the battery pack from catching on fire
Implementation Method 2
The MFM is a sintered 3D network made of micron-sized metal fibers. It typically has a high void volume of 70-99.5 vol %. For heat transfer purposes, the fibers are made of thermally conductive metals such as copper, nickel, aluminum, and their alloys
Implementation Method 3
the fibers are made of thermally conductive metals such as copper, nickel, aluminum, and their alloys and have a fiber diameter less than 100 microns
Implementation Method 4
the MFM and the active cooling structure(s) are thermally integrated by sintering them together. This sintering step generally occurs prior to the infusion of PCM into MFM. Due to the sintering, the heat transfer at the interface of MFM and active cooling structure can be significantly improved.
Data Source
AI summary
Battery packs for high energy density batteries (cells), particularly arrays of such batteries are described herein. The battery packs include a microfibrous media (MFM)-phase change materials (PCM) composite block and one or more active cooling structures. The MFM is typically sintered to the active cooling structures. The battery packs may contain more than one MFM-PCM composite block. Additionally or alternatively, the MFM-PCM composite block may contain different layers containing different MFM-PCM composites, which have different functionalities. In a preferred embodiment, at least one layer contains a flame retardant PCM, while at least one other layer contains a PCM with a lower melting temperature. The cells may be arranged in a repeating square or equilateral triangle pattern, with one or more active cooling structures in the geometric center of the square or triangle.