Thermally conductive potting compound for batteries and BMS
In battery modules and BMS, thermal management is crucial for performance, lifespan, and safety. Thermally conductive potting and gap-filler materials dissipate cell heat and can delay fire spread in the event of a fault. This article outlines the requirements – and where the real limits lie.
To the point
What is needed is a material that simultaneously thermally conductive, electrically insulating, flexible, and flame-retardant – usually a dispensable gap filler between the cell stack and the housing or cooling plate. Pure thermal conductivity is not sufficient; the entire heat path and mechanical compatibility with cell respiration are crucial.
What makes battery applications special
Heat path to the cooling plate
A gap filler fills the gap between the cell stack and the housing or cooling plate, creating a continuous, heat-conducting path. What's important is not just the thermal conductivity, but complete, gapless contact – air pockets negate even the best performance characteristics.
Cellular respiration and mechanical compatibility
Cells change their volume through charge/discharge cycles and aging. The material must accommodate this movement with minimal stress, without putting strain on the cells – an overly stiff, highly filled material will negatively impact their lifespan.
Safety and fire spread
In the event of a fault (thermal runaway), the material should delay the spread from cell to cell as much as possible; some types are formulated to form an insulating barrier at runaway temperatures. Fire spread in stationary storage systems is assessed, among other things, by UL 9540A; for vehicle batteries, additional requirements such as UNECE R100 apply, and for transport, UN 38.3.
| Requirement | Why |
|---|---|
| Thermally conductive + electrically insulating | Dissipate heat without electrically bridging cells |
| Flexible, low module | Cellular respiration and vibration absorption with minimal stress |
| Flame retardant | Delay fire spread in case of a fault |
| Low density, dispensable | Save weight, dose reliably |
Material selection and honest classification
We do not stock dedicated thermally conductive gap fillers for batteries – we select these materials application-specifically and procure them according to thermal conductivity, flame retardancy class, and processing requirements. For the thermal interface of smaller assemblies or sensors, a thermal paste such as DOWSIL 340 available. A general comparison of thermal material classes can be found under Thermal Interface Materials.
Frequently Asked Questions
Gap filler or potting compound? Gap fillers are highly thermally conductive and fill defined gaps to the cooling plate; a full potting compound provides additional mechanical protection and protection against media, but adds more weight and heat capacity.
Why isn't high thermal conductivity enough? Because the heat path as a whole counts: air inclusions, poor connection, or excessively thick layers impair cooling despite good thermal conductivity.
What does flame-retardant mean in this context? The material is intended to delay the spread of thermal runaway; some types decompose to form a barrier. The decisive factor is the testing required for your system.
Advice
Tell us the cell format, gap size, required thermal conductivity, and flame retardancy class – we'll select the right type and procure it for you. Contact us or write to info@silitech.ch.
