Fire protection materials for EV batteries

Nicola Brittain

EV batteries need to be made from fire resistant materials, here we explore some of the available options.

Safety is of the upmost importance for car manufacturers and with the exponentially increasing demand in the electric vehicle market, the awareness of thermal runaway and potential fires from batteries is increasing simultaneously. A recent report from consultancy company IDTechEx called ‘Fire Protection Materials for EV Batteries 2024-2034: Markets, Trends, and Forecasts’ explores different battery technologies and fire-resistant materials as emerging options for dealing with the risks.

Recalls of electric vehicles, although rare, have happened over the past few years due to risks relating to thermal runaway. As might be expected, some of these fires have occurred during crashes or fast charging, but somewhat unexpectedly, they have also occurred when the vehicle is stationary and not undergoing any obvious operations. This highlights the unpredictability of these incidents.

One issue might be cell-to-pack batteries, popular because they improve energy density, reduce part counts, and decrease costs. However, stacking all of the cells directly together leads to a greater risk in propagation of thermal runaway.

Multi-functional materials

At the cell-level, with the transition to cell-to-pack, there is a need to incorporate materials that can achieve multiple functions. Ideal materials for mitigating these issues are those that provide thermal and electrical isolation, conformability, and even structure while being lightweight, thin, and low-cost. Options might include encapsulating foams to get between cells, or compression pads with fire protection to protect pouch-type cells. These materials can aid in preventing the propagation of thermal runaway from cell to cell within the pack.

Various materials can also be applied under the lid, on top of modules, or on the outside of the battery pack to provide further protection beyond the cell-level. Examples include ceramic blankets or mica sheets below the lid and various types of fire-protective coatings on the enclosure.

Thermal management is another option for reducing fire hazards. Active liquid cooling and refrigerant have already replaced air-cooled batteries to allow for greater control of battery temperature. Cold plates within the pack are not commonplace, but new battery chemistries could also be a way to help with thermal management. This might include the switch to sodium-ion from lithium-ion and despite the fact that this type of battery still comes with a risk, early studies report a lower chance of thermal runaway. Their ability to be transported at 0V (Volts) also makes them lower risk than lithium-ion when considering transport and assembly.

Solid-state batteries could also replace the liquid electrolyte in traditional lithium-ion cells with a better operating temperature range, meaning they are less likely to overheat.

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