Dr James Edmondson of IDTechEx shares his thoughts and research findings on interface materials in EV batteries
Dr James Edmondson, research director at IDTechEx, says that the key to electric vehicles being used more widely is lower-cost models with more affordable retail prices. A way of achieving this is by producing cheaper EV batteries, as it is the most expensive part of producing electric cars. Cheaper packing of these batteries will also have the same impact, as it allows for higher energy storage, as higher energy density batteries are expensive to produce. Thermal interface materials (TIMs) are materials inside battery packs to help transfer heat from the cells to the cooling mechanism.
Cell-to-pack TIM reduction intensity
Cell-to-pack is the most widely used method of reducing materials in battery packs. This is done by stacking all of the cells together without individual modules. This reduces the amount of materials needed for housing and internal connections within the battery pack.
This method only requires a single layer of TIM between cells and cold plates, instead of inside every single unit, reducing the amount of TIM required for electric vehicles to be manufactured. This can result in a nearly 50% reduction in TIM required according to IDTechEx.
CATL’s CTP 3.0 design has seen a drastic reduction in TIM usage, as it uses expandable coolant channels that sit between the cells. This makes sufficient thermal contact with the cells to reduce its heat and transfer it away from the battery cell without the need for TIMs. A small amount of TIMs is required for the edges of these coolant channels, but that is all.
TIMs are not just important for temperature regulation, as they are also important in the structure. These components require stronger adhesive qualities, such as thermally conductive adhesive, compared to other solutions that use a modular design, which uses a more gel-like gap filler.
Gap filler products are cheaper per kg than thermally conductive adhesives, meaning that although some value is lost via material reduction, it can be recuperated through higher material costs.
Alternative cooling approaches to remote TIMs
Xerotetch has manufactured batteries that use coolant channels between cylindrical cells that are made from a polymer instead of aluminium. These channels can expand, allowing them to fill gaps between cells and make contact with them, allowing for thermal conduction.
Miba has designed a product called FLEXCooler. This replicates cold plates and TIMs but with flexible channels which expand around cells, with claims that this reduces raw materials by 80%.
Immersion cooling can also result in no longer needing TIMs. Dielectric coolant is used to immerse the cells, removing the need for cold plates. This does create new problems around fluid sealing, pump selection and added complexity. IDTechEx predicts that this method will only be used for high-performance, power-dense battery packs due to the problems with it.
