By Sarah Lozanova, Clean Energy Copywriter
Fires in electric vehicles (EVs) and Energy Storage Systems (ESS) have gained significant media attention in recent years. In a high-profile move, GM recalled Bolt batteries in 2020 and 2021, costing the company $1.9 billion. Battery defects were contributing to thermal runaway, but GM was not alone. Hyundai and Ford also recalled batteries for causing fires, costing the companies hundreds of millions of dollars each.
Likewise, there is a risk of building fires from residential, commercial, and utility-scale energy storage batteries. For example, due to fire hazard concerns, LG Energy Solutions recalled roughly 10,000 RESU 10H storage batteries in 2021. In addition, in 2019, an ESS caused an explosion at an Arizona Public Service (ASP) site, injuring several firefighters.
Although manufacturer defects have contributed to this issue, clean energy technicians need to create a thermal management strategy to prevent the risk of thermal runaway and the associated fire danger.
What Is Thermal Runaway?
Thermal runaway can be unforgiving if left unchecked. Thermal runaway is a process that involves increased temperature. Then, the release of energy causes a greater increase in temperature. Then, the cycle repeats itself, and this uncontrolled positive feedback can have a destructive result.
This phenomenon occurs in chemical engineering with exothermic reactions and electrical engineering with increased current flow and power dissipation. In civil engineering, thermal runaway occurs when large amounts of excess heat are released from curing concrete or in astrophysics with runaway nuclear fusion reactions in stars.
What Is Thermal Runaway In A Battery?
Thermal runaway in lithium-ion battery pack technology can occur when damage in a battery cell causes the release of toxic or flammable gases. This can then create a chain reaction as the decomposition of one battery cell spreads, causing further chemical reactions. In the process, heat builds up more quickly than it can dissipate. Finally, the battery ignites or even explodes.
One critical component in a lithium-ion battery is the separator, a porous membrane separating the anode and cathode sides of the battery while allowing ion transfer. However, separator breakdown, often caused by heat, can lead to thermal runaway.
Abuse factors on batteries are also often the trigger of thermal runaway. Common abuse factors include overcharging, overheating, battery misuse, manufacturer defects, and short circuits.
Often, excess heat accumulates faster than it is expelled. This causes the electrolyte in the battery to turn from a liquid into a gas. As the gas expands, it increases the internal pressure in the battery faster than it can be vented.
If there is intervention at this point and the abuse factor stops, this can prevent thermal runaway. However, if the separator in the battery is damaged, the positive and negative sides of the battery start mixing. The cracking of the separator causes smoke, which signals that failure is imminent and thermal runaway occurs.