Thermal runaway of batteries

24-01-2024 | Posted by Joaquín Martí

Thermal runaway in batteries refers to a self-accelerating and uncontrolled increase in temperature that can occur when a battery undergoes a cascading failure, often resulting in the release of significant amounts of heat, gases, and potentially leading to a fire or explosion. This phenomenon is a major safety concern in various battery-powered devices and electric vehicles.

Thermal runaway is most commonly associated with lithium-ion batteries. Such batteries are widely used due to their high energy density and relatively low weight, but they are also more susceptible to thermal runaway compared to other battery types.

The thermal runaway process can be triggered by various internal and external factors, including:

1. Overcharging: Continuous charging beyond the battery’s capacity can lead to the formation of metallic lithium, causing internal short circuits and initiating thermal runaway.
2. External heat sources: Exposure to high ambient temperatures, such as leaving a battery in a hot car or direct sunlight, can accelerate the onset of thermal runaway.
3. Physical damage: Mechanical abuse or impact to the battery can damage its internal components, resulting in short circuits and triggering thermal runaway.
4. Manufacturing defects: Faulty manufacturing processes or impurities in the battery materials can weaken the battery’s stability, making it more prone to thermal runaway.
5. Internal cell variations: Variations in the manufacturing of individual cells within a battery pack can lead to imbalanced charging and discharging, potentially causing thermal runaway.

Once thermal runaway begins in a single cell of a battery, it can spread rapidly to neighbouring cells due to a chain reaction, causing a catastrophic failure of the entire battery pack. During the process, the temperature can rise significantly, leading to the release of flammable electrolytes, toxic gases, and the risk of fire or explosion.

To mitigate the risk of thermal runaway, battery manufacturers and device designers implement various safety measures, including:

1. Thermal management systems: Installing cooling mechanisms or heat dissipation materials to regulate battery temperature during operation.
2. Battery Management System (BMS): Using advanced control systems to monitor and balance individual cell voltages, temperatures, and charging levels to prevent imbalances.
3. Mechanical safeguards: Incorporating physical protections to reduce the risk of physical damage to the battery cells.
4. Enhanced battery materials: Developing more stable battery chemistries and materials that are less prone to thermal runaway.
5. Safety standards and regulations: Implementing safety testing and certification to ensure battery products meet specific safety requirements.

For the moment, thermal runaway remains a challenge as battery technology continues to advance, with electric vehicles and large-scale energy storage systems becoming increasingly prevalent. As a result, ongoing research and development efforts are focused on improving battery safety and mitigating the risk of thermal runaway incidents.

In this environment Principia has been more than an onlooker. We have carried out thermal, fluid, and mechanical analyses in support of various manufacturers trying to achieve better battery designs and we have even contributed to the design of a facility for testing batteries in extreme situations, including thermal runaway, fires, and explosions.