Thermal insulation in battery systems are the barriers between cells and modules that slow the transfer of heat. Their most important job: when one cell goes into runaway, the heat must not drag the neighbouring cell along at once. This delay, in technical terms preventing thermal propagation, buys the system time and the occupants the seconds to get out. At GOBA such barriers are made as fabricated parts: aerogel composite, mica or fleece, cut and punched to the contour of the cell.
Why thermal insulation in battery systems matters
A lithium-ion cell works in a narrow temperature window. If it gets too hot, for example through an internal short, an overcharge or damage, it can tip into thermal runaway: a self-accelerating reaction in which the cell suddenly reaches several hundred degrees and vents gas. In a pack with hundreds of cells the decisive question is not whether a single cell fails, but whether it infects its neighbours. That is exactly what the thermal barrier prevents. It has a double role: it damps everyday heat so all cells age at an even temperature, and in the fault case it holds back the heat front.
Thermal runaway protection and cell-to-cell barriers
Protection against propagation acts between the cells. A barrier between two cells has to withstand two loads that rarely occur together: the short, extreme temperature surge above 600 degrees at the surface of the runaway cell, and the mechanical pressure when the cell swells. A good barrier does several things at once.
- It slows the heat flow to the neighbouring cell so it stays below the critical temperature.
- It survives extreme peaks for a short time without melting or burning through.
- It cushions the swelling of the cell and still holds its thickness in everyday use.
- It insulates electrically so the barrier does not itself become a bridge between potentials.
Thickness is a compromise. Every millimetre of barrier costs energy density in the pack, every missing millimetre costs safety reserve. So the battery engineer sizes the barrier as thin as possible and as thick as necessary, often below one to a few millimetres.
Materials for the thermal barrier
No single material can do everything. So battery makers use different materials depending on the requirement, often in a composite.
- Aerogel composites: extremely low thermal conductivity around 0.02 watts per metre and kelvin, usually a mat reinforced with fleece. The benchmark for thin, effective cell-to-cell barriers.
- Mica barriers: withstand over 800 degrees for a short time, dimensionally stable, and strongly insulating electrically. Proven as a heat shield at the hottest point.
- Fleece and fibre composites: elastic, affordable, good as pressure compensation and as a carrier for other layers. They cushion the swelling of the cell.
- Ceramic paper: high-temperature resistant above 1000 degrees, used where a hard heat front lies directly against it. Related to classic high-temperature insulation.
In practice a battery maker combines these layers: an aerogel core for damping, a mica layer against the heat peak, a fleece for pressure compensation. The result is a laminate that GOBA produces in one cut. The pure thermal insulation is only one of the functions the part fulfils.
Electrical plus thermal double function
Inside the cell, electrical and thermal insulation often come together in the same part. A barrier between two cells not only separates heat, it must also keep the voltage potentials apart, otherwise it becomes a short-circuit path. That is why many barrier materials are also good dielectrics, above all mica and ceramic paper. The difference lies in the goal: electrical insulation is meant to prevent a current flow, thermal insulation a heat flow. One material can do both, but the design follows separate parameters, dielectric strength on one side, thermal conductivity on the other. Anyone who checks only one value overlooks the other load. This double function ties the topic closely to battery insulation and to the separator films inside the cell, which separate the ion flow and keep the electrodes apart.
Fabricating the barriers
Whether aerogel, mica or laminate, the material arrives as a web or plate and must fit the contour of the cell. This step is the fabricator's job. GOBA cuts and punches the barriers so they fit into the cell stack without rework.
- Slitting the web to the required width, on thin aerogel mats with a guided blade so the edge does not fray.
- Punching the contour, the cut-outs for poles and sensors, and the tolerances the cell stack demands.
- Laminating several layers into a composite when damping, heat shield and pressure compensation should sit in one part.
- Checking for dimension and clean edges, because a frayed aerogel edge dusts and loses insulating effect.
Aerogel is tricky to cut, it dusts and the edge chips easily. We run the blade shaft slower here and guide the material cleanly, otherwise the edge frays. It is exactly this processing knowledge that separates a usable cut from one that causes trouble in the pack.
GOBA Takeaway
Thermal insulation in battery systems is no side issue, it decides whether a runaway cell becomes a manageable fault or a pack fire. The right barrier combines aerogel, mica and fleece into a thin laminate that slows heat, withstands peaks and separates electrically. GOBA has been cutting and punching these materials for decades and delivers the barriers as fabricated parts, fitted to the cell. Send us your cell dimension and the desired material via battery film slitting or our page on electromobility and automotive, and you will receive a technical quote with a sample cut.
