Why Thermal Silicone Oil Became the “Invisible Champion” in EV Battery Packs-Iota

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News > Dynamic industry > Why Thermal Silicone Oil Became the “Invisible Champion” in EV Battery Packs

Why Thermal Silicone Oil Became the “Invisible Champion” in EV Battery Packs

With the rapid growth of electric vehicles (EVs) and large-scale energy storage systems, battery thermal management has become more critical than ever. High temperatures, dense current flow, and long-term cycling impose strict requirements on the safety and lifespan of battery packs. As a core component of thermal interface materials (TIMs), thermal silicone oil has emerged as an “invisible champion”, playing a key role in heat dissipation, insulation, and aging resistance.

Thermal pastes and gels are composed of highly thermally conductive fillers (e.g., aluminum oxide, boron nitride) dispersed in a base silicone oil. Silicone oil not only acts as a dispersion medium but also ensures filler wetting, minimizes interface thermal resistance, and forms uniform thermal paths. At the interface between cells and heat sinks, silicone oil enables high filler packing density and low void ratio, facilitating rapid heat transfer.

Key technical advantages:

Low volatility and high flash point
Volatile or low-flash-point silicone oils may migrate or dry out under high temperature, compromising thermal performance. EV-grade silicone oils use low-volatility formulations and high flash point designs, maintaining stable TIM performance above 150℃.
Excellent compatibility
Silicone oil must be highly compatible with fillers like aluminum oxide and boron nitride to ensure uniform dispersion. Domestic manufacturers achieve this through narrow molecular weight distribution and surface activity optimization, ensuring high filler density under low shear while avoiding phase separation or sedimentation.
Controllable rheology
Viscosity directly affects application and heat transfer. Too low viscosity leads to oil migration; too high results in uneven spreading and trapped air, increasing thermal resistance. Optimal viscosity (typically 500–2000 cSt) allows rapid leveling under assembly pressure, forming ultra-thin, dense thermal films.

Industry data shows that battery packs using high-quality thermal silicone oil maintain stable thermal resistance after cyclic thermal aging. Key components such as IGBTs and power modules show a temperature drop of 3–5℃, significantly improving safety margin and service life.

“In EV battery packs, even small amounts of thermal silicone oil are critical,” says a thermal management engineer. “Choosing the right silicone oil means considering not just thermal conductivity but filler compatibility, low volatility, and long-term stability.”

As high-voltage platforms and higher thermal densities become common, thermal silicone oil is evolving from a supporting material into a core barrier for battery thermal management. Industry experts recommend that procurement and design teams prioritize base silicone properties and filler compatibility rather than cost alone—because every degree of temperature reduction matters for battery safety.

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