Expanded Graphite Thermal Interface Material with Embedded Reinforcement

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Solution Overview

Problem

Existing thermal interface materials (TIMs) used in electric mobility applications are heavy, expensive, and inefficient in thermal management, leading to suboptimal service life of energy storage devices in electric vehicles due to limited thermal conductivity and manufacturing complexities.

Innovation Solution

A thermal interface material comprising a plate made of expandable graphite with a reinforcement embedded within, utilizing a thermally conductive material like aluminum with a mesh structure to enhance thermal conductivity and stability, while minimizing weight and avoiding damage to adjacent structures through controlled compression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gap filler pastes are used to bridge the gap between battery tray and battery module, then the gap can be filled and thermal management is enabled, but the TIM becomes heavy and expensive

Engineering Contradiction:

Improvethermal management effectivenessVSAvoidTIM weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent uses expanded graphite as the base material for the TIM, which provides good thermal conductivity while being lightweight. The graphite is compressed to form a dense structure that can effectively fill gaps and transfer heat, replacing heavier traditional gap filler pastes while maintaining thermal management effectiveness

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent achieves weight reduction by changing the material composition from traditional heavy pastes to expanded graphite. The graphite is compressed to specific density ranges (0.6-1.8 g/cm³) to optimize both weight and thermal conductivity, creating a TIM that is lighter than conventional solutions while maintaining gap-filling capability

Inventive Principle:

Principle #35Parameter changes

2Weight of moving object

If expanded graphite is used as TIM, then weight is reduced and thermal conductivity is improved, but handling strength and structural stability are insufficient

Engineering Contradiction:

ImproveTIM weightVSAvoidhandling strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The patent creates a composite structure by embedding reinforcement elements (such as metal meshes, fabrics, or three-dimensional structures) within the compressed expanded graphite matrix. This combination provides both the lightweight, thermally conductive properties of graphite and the structural strength of the reinforcement material, solving the handling strength issue

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The reinforcement is strategically placed within the TIM structure to provide strength where needed during handling and installation, while the expanded graphite maintains its lightweight and thermally conductive properties in other areas. The reinforcement may be positioned as a mesh or fabric throughout the graphite matrix to provide localized structural support

Inventive Principle:

Principle #3Local quality

3Reliability

If compression force is increased to improve thermal contact, then thermal conductivity improves, but adjacent structures may be damaged

Engineering Contradiction:

Improvethermal contact qualityVSAvoiddamage to adjacent structures

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent controls the density of the compressed expanded graphite within specific ranges (0.6-1.8 g/cm³) to achieve optimal thermal conductivity while limiting the compression force applied to adjacent structures. This parameter control ensures sufficient thermal contact without exceeding damage thresholds

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The compressed expanded graphite structure acts as a cushioning element that distributes compression forces evenly across the contact surface. The material's compressible nature allows it to deform and fill irregularities in the gap while limiting peak stresses on adjacent components, preventing damage before it occurs

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Reliability

If traditional gap filler pastes are used, then gap filling is achieved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improvegap filling capabilityVSAvoidmanufacturing simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses compressed expanded graphite which can be manufactured as a ready-to-install component and disposed of or replaced if needed, eliminating the need for complex application processes and cleanup associated with traditional pastes. The material is provided in a pre-compressed form that requires minimal installation effort

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent simplifies manufacturing by providing the TIM as a pre-compressed graphite element with controlled density and thickness, which can be directly installed in the gap without requiring mixing, application tools, or curing processes. This parameter-controlled approach enables straightforward manufacturing and installation

Inventive Principle:

Principle #35Parameter changes

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 provides efficient heat dissipation, extended service life, and ease of manufacturing, with improved handling strength and reduced weight, ensuring effective thermal management in electric vehicles without exceeding pressure thresholds that could damage battery components.

Implementation Method 1

a thermal interface material (TIM), in particular for an energy storage device... heat is transferred to a battery tray located below a battery module... Currently, gap filler pastes are used for this purpose. These pastes typically offer a thermal conductivity of around 3 W/MK

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The reinforcement can, for example, be made of a thermally conductive material whose thermal conductivity is at least equal to that of the expandable graphite... the reinforcement can have a conductivity of approximately 200 W/mK... by being made of aluminum, the reinforcement can have a thermal conductivity of 190–230 W/mK

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

allows compression at low, defined forces, thus preventing damage to adjacent structures... The TIM can, for example, be compressed to a thickness of 1 mm

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentEP4112582A1Thermal interface material, energy storage device with thermal interface material and method of manufacturing the same

Publication Date: 2023.01.04 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

Figure 1~2c
Figure 2d~2e
Figure 3a~3d

AI summary

The invention relates to a thermal interface material (TIM) (1), in particular for an energy storage device, comprising a plate (2) made of expanded graphite, wherein a reinforcement (3) is embedded in the plate (2). The invention also relates to an energy storage device with such a TIM (1) and to methods for producing the TIM (1) and the energy storage device.