Battery Pack Thermal Interface with Insulating Granules
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Solution Overview
Problem
Rechargeable battery packs in vehicles are prone to thermal runaway events due to battery shorts, which can lead to fires and propagate throughout the pack, posing risks to people and property.
Innovation Solution
A battery pack design featuring a thermally and electrically conductive epoxy layer with dispersed granules, such as alumina or silica, that maintains electrical insulation and high thermal conductivity, preventing battery shorts during thermal runaway by keeping batteries separated from heat sinks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a thermally conductive epoxy layer is used to thermally couple batteries to the heat sink, then heat transfer efficiency is improved, but electrical insulation is lost leading to battery shorts
Solution Approach 1:
The patent uses a composite material consisting of thermally conductive epoxy mixed with electrically insulating granules (such as alumina or silica). This composite maintains the thermal conductivity of the epoxy while adding electrical insulation properties through the granules, thereby resolving the contradiction between heat transfer efficiency and electrical insulation.
2Reliability
If batteries are thermally coupled to heat sinks using conductive material, then thermal runaway propagation is reduced, but electrical shorts between batteries and heat sink occur
Solution Approach 1:
The composite material of thermally conductive epoxy with electrically insulating granules creates a thermal interface that allows heat to flow from the battery to the heat sink while the insulating granules prevent electrical contact, thus eliminating electrical shorts while maintaining thermal runaway control.
Solution Approach 2:
The epoxy layer with insulating granules acts as an intermediary between the battery and heat sink, mediating thermal energy transfer while blocking electrical current flow. This intermediary material enables thermal coupling without electrical shorting.
3Temperature
If highly thermally conductive epoxy is used, then heat dissipation is improved, but electrical conductivity increases causing battery shorts
Solution Approach 1:
The patent creates a composite where thermally conductive epoxy is combined with electrically insulating granules. The granules do not significantly impede thermal conduction while providing electrical insulation, thus maintaining heat dissipation capability while preventing electrical shorts.
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 effectively minimizes the risk of battery shorts and thermal runaway propagation, enhancing safety and reducing property damage by maintaining electrical insulation and efficient heat transfer even under extreme temperatures.
Implementation Method 1
a layer of thermally conductive and electrically insulative epoxy that contacts and is thermally coupled to a lower portion of each of the subset of batteries
Implementation Method 2
a plurality of granules dispersed throughout the region of the epoxy layer, where the granules have a melting point that is higher than the melting point of the thermally conductive epoxy
Data Source
AI summary
A battery pack is provided that is configured to minimize the risk of battery shorts during a thermal runaway event. The battery pack uses a layer of a thermally conductive, electrically non-conducting epoxy to transfer heat from each of the pack's batteries to an underlying heat sink/heat spreader. A plurality of electrically non-conductive granules, for example fabricated from alumina or silica, is dispersed throughout at least a region of the epoxy layer. As a result of the granules, even if the epoxy layer softens sufficiently during a thermal runaway event to allow movement of the batteries, the granules will prevent the batteries from contacting the underlying heat sink/heat spreaders and shorting out, one benefit of which is decreasing the likelihood of an initial thermal runaway event propagating throughout the entire battery pack.