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Having spent decades in academia, specialising in electrochemistry, Professor Paul Christensen is the ideal person to look at how lithium-ion battery fires and why there is so much more work to be done in this area to understand the risk to firefighters tackling these types of fires.
Drawing on decades of academic work in electrochemistry at Newcastle University, Paul started looking at lithium-ion battery production as part of an EU-funded project in the early days of the development of electric vehicles. Since then, he has shared examples of lithium-ion battery fires that he finds from across the world and provides commentary on the broader topic of the dangers when they go wrong.
Understanding the hazards
Paul sets out four hazards that come from battery fires: toxic gases, battery explosion, rocket like flames and vapour cloud explosions. “When you put them all together, that’s what makes EV fires particularly challenging,” he says. It’s not even a linear process where one hazard follows another and as a result, lithium-ion battery fires are unpredictable and the nature of the risk changes during the incident.
Paul regularly gives presentations to fire and rescue services, sharing his knowledge about battery fires. He is also associated with The Faraday Institution, which is the UK’s independent institute for electrochemical energy storage research.
He finds that most of his invitations come from enthusiasts who have read about his work or have spoken to others who are keen to learn about this emerging risk. He adds that he’s had little traction with ambulance services and police forces so far.
Related reading: Views on electric vehicles from The Emergency Services Show
What does the data tell us?
Fire and rescue services must record the detail of incidents that they respond to and in England they do so via the Home Office’s Incident Recording System (IRS). I had a look at the Home Office fire statistics and all I could find was fires whose cause was ‘electrical distribution’ which seemed about the closest approximation to a battery fire.
My conversation with Andy Butterfield from National Highways , reveals the number of electric cars breaking down on A roads and motorways is in the low hundreds. Paul mentioned statistics collated by EV Firesafe, an organisation funded by the Australian Department of Defence, which show that globally since 2010 there have only been 504 verified incidents of fires and explosions involving road registered EVs – cars, buses & trucks. Given that the number of EVs sold worldwide in 2022 alone was more than 10 million, according to EV FireSafe this makes EVs 10-20 less likely to go into catch fire than ICEVs.
Paul always tries to inform first responders of the risks and hazards but also to put EV fires in context, but usually only after some shock-and-awe in order to try and make them hesitate just long enough to re-assess the situation and hopefully keep them safe.
“Our understanding of the risks and hazards is lagging behind what it should be.”
The vapour cloud phenomenon
Paul discovered the concept of vapour clouds about four years ago when he was carrying out experiments with donated batteries from Envision-AESC (which had taken over the Nissan Battery plant).
“We realised that all lithium-ion batteries produced a vapour cloud and when the cloud vents it takes with it small droplets of organic solvent and hence looks like smoke or steam steam. If that burns immediately, it is replaced by a very thin fume, then black smoke when the plastics burn. If it doesn’t burn immediately and ignition is delayed, you can get a vapour cloud explosion.”
Paul continues to learn and has refined his understanding of vapour cloud explosion, dividing them into unconfined (exploding within the vehicle) and unconfined (exploding outside the vehicle).
Why is he telling me this? He says it’s important because the behaviour of the battery going through thermal runaway – an uncontrollable, self-heating state- can result in fire or explosion (including the explosion of the battery) and hence different challenges to first responders. Vapour cloud explosions, Paul says, are understated and as yet not entirely understood hazards for first responders.
So much more to learn
He mentions the car transporter fire on the M1 from early 2023 where firefighters from Nottinghamshire and Derbyshire Fire and Rescue Services responded when several electric vehicles were alight which led to the motorway being closed for many hours. The learning from that kind of incident is important as it’s unlikely to be a one-off.
“It’s very early in our journey of understanding about lithium-ion battery fires.”
He says we need to consider how much we have learned about combustion engine cars over the last century and how little time we’ve had to get to grips with the electric vehicle.
“We don’t know what the effect of usage and ageing is on the thermal stability of the battery.”
He adds, “About the only thing we do agree on, as academics, is that if you rapid charge lithium-ion batteries then you destabilise them as you cause what is called lithium metal plating on the annode.” He goes on to explain this can degrade the battery and cause them to malfunction and that this is ‘very bad news.’
As EV batteries age, they are no longer useful in cars but they do have second lives in other applications. Paul says there are no standards in place to control this usage and worries that it is a larger risk that is not properly understood and where stored in quantities, in turn could be a risk to first responders.
We talk a little about battery energy storage systems and the risk they represent. He mentions Maria Miller MP’s interest in this and her intervention in the debate on the Energy Bill reveals her concern about fire and rescue services not being consulted as part of planning applications for new storage facilities. She said that they posed a ‘significant risk to people, including firefighters,’ and asked that the regulatory regime reflect management of that risk.
“EVs have reignited, days or even weeks after an accident.”
He says that there is still trapped electrical energy in the battery and that means that it can reignite. That can happen on the back of a transporter or at the recovery yard.
I’m interested in the environmental impact of EV fires where the metals from the battery can enter the water course. Pauls says that pollutants come from the heavy metals in the cathode and can typically include cobalt, nickel and manganese. There is some research in this area, but as is often the case with this topic, it’s early days for this too.
Need for more research
It’s often the case with academia that more research is needed to further understanding of topics and EV battery fires are no different. He wants to know more about the role of the droplets of organic solvent in the vapour cloud and why they explode. Vapour cloud can mask the heat source so a firefighter using a thermal imaging camera won’t pick up the heat and as a result doesn’t have the full picture of the risk they face.
Armed with better evidence he can provide firefighters with what they should know when faced with an EV battery fire because firefighter safety is so very important.
This updated article originally appeared in the June 2023 print issue of Emergency Service Times.
