The global transition toward clean energy has pushed electric vehicles (EVs) and Battery Energy Storage Systems (BESS) into the spotlight. At the heart of these technologies lie lithium-ion batteries and high-power electronics — components that generate massive amounts of heat during fast charging, high-speed driving, or heavy grid loading. Managing this heat is non-negotiable. This is where Thermal Interface Materials (TIMs), specifically thermal pads, become the unsung heroes of energy storage and e-mobility.
What Is a Thermal Pad?
Fig. 1 — Pre-formed thermal pad for battery and electronics cooling
A thermal pad is a pre-formed, solid square or rectangle of specialized material — often silicone or non-silicone petroleum-based polymers — filled with thermally conductive particles such as ceramic or metal oxides.
Unlike thermal paste, which is messy and prone to pumping out over time, thermal pads offer a clean, consistent, and highly durable solution. Their primary function is to conform to irregular surfaces, eliminating microscopic air gaps — which act as thermal insulators — between heat-generating components (like battery cells) and cooling systems (like liquid-cooled plates).
Air has extremely low thermal conductivity (~0.025 W/m·K). Even a thin air pocket between a battery cell and a cooling plate dramatically increases thermal resistance, causing localized hotspots that accelerate cell degradation and increase the risk of thermal runaway.
Thermal Pads in Electric Vehicles (EVs)
In an electric vehicle, space is at a premium and safety demands are absolute. Thermal pads are strategically deployed across several critical areas to maintain optimal operating temperatures and ensure system reliability.
Fig. 2 — Thermal pad between battery cells and cooling plate in an EV pack
1. Battery Pack Assembly
EV battery packs consist of hundreds or thousands of individual cells bundled into modules. Thermal pads serve two essential roles here:
Cell-to-Cooling Plate Transfer: Thermal pads are placed between the bottom of battery cells and the liquid cooling plate, ensuring heat generated during rapid acceleration or DC fast charging is quickly transferred away.
Vibration Dampening: The soft, compliant nature of thermal pads also helps absorb road shocks and mechanical vibrations, protecting delicate electrical connections throughout the pack.
2. Power Electronics and Inverters
The inverter converts DC power from the battery to AC power for the motor. The insulated-gate bipolar transistors (IGBTs) or Silicon Carbide (SiC) MOSFETs inside these inverters generate intense, localized heat. High-thermal-conductivity pads ensure these semiconductors do not exceed their maximum operating temperatures, preventing catastrophic drivetrain failures.
Fig. 3 — Thermal pad applied to OBC and DC-DC converter for heat dissipation and electrical isolation
3. On-Board Chargers (OBC) and DC-DC Converters
These components handle high voltages and currents daily. Thermal pads provide the necessary thermal dissipation while acting as an electrical insulator, preventing high-voltage shorts to the vehicle’s chassis — a critical safety requirement in 400V and 800V EV architectures.
Thermal Pads in Battery Energy Storage Systems (BESS)
Fig. 4 — Grid-scale BESS installation with thermal interface materials throughout battery racks and power systems
While both Electric Vehicles (EVs) and Battery Energy Storage Systems (BESS) rely on lithium-ion technology, their operational environments demand entirely different thermal management strategies. In an EV, components must withstand constant mechanical shock, tight spatial constraints, and dynamic drive cycles.
However, when transitioning to stationary BESS installations — designed to stabilize power grids and store massive amounts of renewable energy from solar and wind farms — the engineering focus shifts dramatically. The primary thermal challenges evolve from vibration resistance to sheer volumetric scale and decade-long component longevity.
1. Battery Racks and Modules: The Core Heat Source
Application: Thermal pads are strategically installed directly between battery cells/modules and liquid or air cooling plates.
Why it matters: Battery cells are prone to micro-surface irregularities. Air gaps between cells and the cold plate trap heat. High-compliance thermal pads eliminate these gaps, ensuring uniform heat transfer — preventing localized hotspots, mitigating thermal runaway risk, and extending the overall lifecycle of the battery rack.
2. Power Conversion Systems (PCS): Managing High-Power Semiconductors
Application: Thermal pads are applied to high-power semiconductor devices including IGBTs and MOSFETs responsible for bi-directional power conversion (AC↔DC during charging and discharging).
Why it matters: Modern PCS units handle massive currents, causing semiconductors to heat up within seconds. Thermal pads with high thermal conductivity (W/m·K) and excellent dielectric strength quickly pull heat away to the heatsink while providing crucial electrical isolation to prevent high-voltage short circuits.
3. Energy Management Systems (EMS): Protecting the Brain of BESS
Application: Thermal pads are utilized inside Electronic Control Units (ECUs), microprocessors, and communication modules that make up the EMS — which monitors state-of-charge (SoC), state-of-health (SoH), and controls power dispatch.
Why it matters: While the EMS generates less heat than battery modules, its electronic components are highly sensitive to thermal fluctuations. Excessive heat can cause signal drift, processing delays, or premature component failure, disrupting real-time data monitoring and grid control.
4. Thermal Management & HVAC Interfaces: Enhancing System Efficiency
Application: Thermal pads improve the mechanical and thermal contact between internal HVAC components, heat exchangers, and the main cooling structures of the BESS enclosure.
Why it matters: By minimizing thermal resistance at these critical joints, thermal pads optimize the overall Coefficient of Performance (COP) of the cooling system. This reduces the parasitic power consumption of the BESS, meaning more stored energy can be dispatched back to the grid rather than being wasted on running cooling fans and chillers.
Key Selection Criteria for EV & BESS Thermal Pads
Engineers must carefully balance several material properties when selecting the right thermal pad for a given application. The wrong choice can lead to premature system degradation, safety incidents, or significant efficiency losses.
| Property | Importance in EV & BESS |
|---|---|
| Thermal Conductivity (W/m·K) | Determines how fast heat travels. Ranges typically from 2.0 W/m·K to over 8.0 W/m·K for high-performance areas. Higher values are required for power semiconductors and fast-charging battery interfaces. |
| Hardness & Compliance (Shore Hardness) | Softer pads conform better to uneven cell surfaces under low compression force, reducing mechanical stress on battery cells. Critical for cell-to-cooling-plate interfaces in large battery packs. |
| Dielectric Breakdown Voltage | Must provide high electrical isolation to prevent short circuits in high-voltage (800V+) systems. Essential for OBC, DC-DC converters, PCS, and EMS applications. |
| Silicone-Free Options | Critical for certain automotive applications to prevent silicone oil migration, which can interfere with electrical contacts or paint processes in EV manufacturing environments. |
| Temperature Range | Must maintain performance from cold-weather startup (−40°C) to peak thermal events. Wide operating range ensures reliability in both EVs and outdoor BESS installations. |
| Long-Term Stability | BESS systems operate for 10–20+ years. Thermal pads must resist compression set, drying out, or material degradation over thousands of charge/discharge cycles. |
