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Tackling Thermal Runaway in EVs

Electric Vehicles (EVs) are an integral piece of the climate change puzzle, with its market exponentially growing in the past decade. EVs hold numerous advantages including overall environmental impact and lower running costs, more and more people are opting for EVs over Internal Combustion Engine (ICE) powered vehicles. However, there’s significant focus upon the dangers of thermal runaway and thermal propagation within EVs.

07/12/22
The Challenge

 

Most electric vehicles are powered via lithium-ion battery (LIB) technology, which is rechargeable due to the reversibility of electrochemical reactions in the system. LIBs are extremely powerful and have been around for a long time but were only introduced for use in vehicles in this century. With the extensive research around LIBs over the years, electric vehicles are extremely safe fundamentally. LIBs are an excellent solution to powering a car due to its extraordinary energy density, its anode cell voltage can be up to 3-4V, which is at least double the value of most developed rechargeable battery systems. However, possible failures could occur due to a design flaw or battery cell damage, resulting in extreme heat and/or penetration of the battery cell wall.

The two main failure mechanisms of LIBs in EVs are via penetration of the battery enclosure and thermal runaway propagation, with both leading to an internal short circuit. When a short circuit occurs, it can lead to a vicious cycle of exothermic reactions – thermal runaway, within battery cells which can lead to ignition or even explosion. As these cells are densely packed within a battery enclosure, thermal runaway of a single cell can propagate to neighbouring cells, setting the whole battery assembly on fire.

How do we support the prevention and delay thermal runaway and propagation events within EV batteries?

 

Our flameproof coatings can be applied onto battery enclosures, which can help delay and prolong the thermal runaway propagation event, slowing the reaction reaching the casing (i.e. Aluminium) to extend the amount of time of failure. Our ceramic coating can withstand 7 minutes of exposure to 1,200°C (temperature of thermal runaway propagation), delaying the effect from spreading, giving time for driver to remove themselves from the vehicle and to safety. Typically, this is applied onto enclosures and battery boxes.

We have also developed polymer or plasma applied coatings with various dielectric properties, which can insulate and prevent heat transfer between neighbouring cells to minimise the risk of thermal runaway and propagation. This solution can be engineered with varying dielectric strengths to support different requirements and geometries, and can be applied onto cooling plates, bracketry, and cooling snakes.

In addition to ceramic coatings, another solution that we offer is our ZircoFlex® ceramic heat shield, which is the highest performing heat shield by weight and thickness that’s available on the market. Its patent protected characteristics make it a unique offering that meet the needs of EV applications perfectly, with high thermal protection where the space envelope is minimal and operating temperature exceeding 600°C. Our flexible ceramic heat shield can be installed around the battery pack, and offset the high levels of heat emitted by the battery, to help maintain the battery temperature around its optimal working temperature ~40°C. Our ZircoFlex® can offer up to 85% heat reduction and with it being extremely thin and lightweight (only up to 1.5kg/m2) which is advantageous over the conventional, far heavier heat shielding alternatives used in cars, increasing the vehicle platform range.

Diagram

It’s also important to note that the automotive industries’ approach to reaching net-zero targets is not solely pinned on EV’s alone. We work on numerous commercial and government funded projects to tackle the thermal challenges that arise from the development of alternative fuels such as hydrogen fuels cells and compressed natural gas (CNG), as they continue to play a vital role in building sustainable transportation solutions for the future.

Contact us to find out more about our solutions for EVs and alternative fuels.