Why do batteries have "thermal problems"
During the charging and discharging of lithium-ion batteries, electrochemical reactions continue to occur inside the battery cells：
- During fast charging, the current is high and Joule heating is concentrated
- Internal resistance heating during discharge
- Inconsistent temperature between battery cells, resulting in "hot spots"
- Temperature increases → internal resistance increases → hotter → lithium deposition/electrolyte decomposition/thermal runaway
There is a consensus in the industry:
Batteries are not afraid of heat, they are afraid of "large temperature differences, concentrated hot spots, and broken heat dissipation paths".
That's why simply "thickening aluminum plates" is not perfect - they are heavy, take up space, cannot adhere to curved surfaces, and have limited lateral heat sharing ability.
What type of "graphite sheet" is used in battery thermal management
| Type | Typical form | Battery scenario |
| Natural flexible graphite paper/foil | 0.1–2.0 mm, Flexible | Module to module thermal pad, insulation buffer layer, sealed thermal conductive layer |
| Highly oriented synthetic graphite film | 0.025–0.5 mm, Surface thermal conductivity of 1500+W/m · K | Consumer batteries, power devices, thin-walled module heat dissipation |
| Multi layer graphite paper (MLGP) | 3-5 layer composite | EV battery pack horizontally evenly heats up and delays heat spread |
6 core advantages of graphite sheets in battery thermal management
1. Extremely fast heat conduction within the surface, spreading out the 'hot spot'
The most ruthless aspect of graphite sheets:
- In-plane thermal conductivity: natural graphite paper 100-600 W/m · K, highly oriented synthetic film 1500-1900 W/m · K
- Copper about 400 W/m · K, aluminum about 237 W/m · K
A layer of graphite sheet is attached to the side of the battery cell, and local heat will spread out along the XY direction, resulting in a decrease in peak temperature and a reduction in module temperature difference.
According to battery factory data, the multi-layer graphite paper system can reduce the temperature difference inside the module from 8-10 ℃ to within 3 ℃.
2. Ultra thin, lightweight, not taking up battery pack space
In electric vehicle battery packs, every 1mm is expensive.
Graphite sheets can achieve:
- 0.025 mm / 0.05 mm / 0.1 mm
- The density is much lower than that of copper and aluminum
- Can be die cut, curved, and sandwiched between battery cells and liquid cooled plates
Same heat dissipation effect, much lighter than aluminum fins. NeoGraf solutions can even reduce the weight of bicycle cooling structures by 20-40 kg.
3. Flexible application to eliminate "air gap thermal resistance"
The metal sheet is hard, and there will be air gaps at the corners of the battery cell.
Air gap is a major thermal resistor.
Graphite flakes can:
- bend
- edge binding
- Die cutting irregular shapes
- Stick the side of the battery cell/ear area/under the Busbar
- Composite with PSA backing adhesive, PI film, and insulation film
Result: Tighter contact and lower interface thermal resistance.
4. Strong horizontal thermal conductivity and weak vertical thermal conductivity, which is actually suitable for battery packs
This may sound like a disadvantage, but it is actually a structural dividend:
- On the surface: delivering heat to the cold plate/shell
- Vertical direction: 5-15 W/m · K, without directly pouring heat into adjacent cells
Engineers use it for a combination of "horizontal uniform heating+vertical insulation":
Graphite sheets are responsible for spreading heat, while liquid cooled plates/phase change materials/PCMs are responsible for removing heat.
5. Preventing thermal runaway propagation in fast charging scenarios
4680, Kirin, Blade, CTC/CTP battery pack all have a pain point:
If a battery cell loses control of heat, don't bring neighboring cells to collapse.
Graphite paper+silicone TIM, graphite paper+PCM, graphite paper+nano alumina coating, can:
- Extend the propagation time of thermal runaway
- Reduce peak temperature
- Leave reaction windows for BMS and fire protection
In some tests, the 5-layer graphite paper scheme reduced the peak temperature of 10C fast charging from 65 ℃ to 52 ℃, and extended the propagation time of thermal runaway to over 30 minutes.
6.Wide temperature resistance, chemical stability, compatible with flame retardant solutions
Graphite can withstand temperatures above 2000 ℃ in an inert atmosphere; Conventional flexible graphite in the air can also withstand the working temperature range of battery packs.
Overlay again:
- Expandable graphite (fire barrier)
- PI film coating
- ceramic coating
- Halogen-free flame retardant layer
You can upgrade from "heat dissipation material" to "thermal safety material".
Typical battery application scenarios
1. Consumer electronics battery
Mobile phones, tablets, and laptops:
The battery and motherboard CPU share graphite film, which lays the battery side heat and SOC heat together on the middle frame.
2. Power battery module
- Graphite sheet on the side of the battery cell
- Module top cover uniform heating layer
- TIM below Busbar
- Thermal transition layer between the cold plate and the battery cell
3. Energy Storage System (ESS)
Energy storage cabinets are most afraid of "cell consistency collapse".
Graphite felt/graphite paper is used for:
- Uniform heating between modules
- Battery cluster separator
- Liquid cooled plate interface
- Fire barrier layer
4. Low temperature scenario
-There is also modified graphite paper (with CNT added) in the 30 ℃ blade battery, which increases the effective discharge capacity from 72% to 85%.
End
In battery thermal management, the value of graphite sheets is not to 'take the heat away', but to first spread the heat and then hand it over to the cold plate/shell/PCM for processing.
Whoever can stabilize the "uniform heating+lightweight+die-cutting+flame retardant composite" will be able to tap into the incremental market of EV and energy storage heat dissipation.
