Identifying the vapour cloud research breakthrough for lithium-ion battery safety

With billions of lithium-ion (Li-ion) batteries in circulation, safety is of paramount importance. While catastrophic Li-ion battery fires remain extremely rare, the vital work of safety expert Professor Paul Christensen is ensuring that first responders know how to tackle incidents correctly and, potentially, to save lives.

MATT GOODING

Faraday Institution

Professor Paul Christensen is the Professor of Pure and Applied Electrochemistry at the UK’s Newcastle University and the leader of its research as part of the Faraday Institution’s SafeBatt Project.

He advises fire services, local authorities, and other government agencies about the risks posed by Li-ion batteries and what to do in the event of an emergency. He also works with automakers to develop firesensing and extinguishing systems for their batteries.

In 2020, he and his team were responsible for a major breakthrough when they highlighted the previously unknown hazard of vapour cloud explosion from Li-ion batteries in thermal runaway.

When overheated, crushed, or overcharged, gases can be produced in Li-ion cells and, in certain circumstances, their temperature can increase very suddenly. This results in the venting of a vapour cloud that includes hydrogen, carbon monoxide, carbon dioxide, and very small drops of the organic solvents used in the cells. First responders had previously mistaken these clouds for steam or smoke, but their composition means they create the potential for a vapour cloud explosion, which can be more dangerous than the initial fire.

Since then, Professor Christensen has been delivering training and guidance to first responders around the world on how to deal with these vapour clouds safely. He has worked with 36 different fire and rescue services across the UK, Australia, and New Zealand, training hundreds of firefighters. He was also a speaker at the 2022 AFAC Knowledge Event Series, sponsored by the Motorola Solutions Foundation.

Rates of catastrophic failure in Li-ion batteries remain extremely low, with estimates suggesting that only one in 40 million suffers such a failure. But with an increasing range of uses spanning electric vehicles, consumer electronics, and second life applications (where existing batteries are reconditioned and reused in new scenarios, such as in the power grid), the potential for problems is increasing.

As well as protecting end users, better battery safety has economic benefits. Increasing the reliability of Li-ion battery systems could allow automakers to reduce the complexity of their systems; save space, weight, and costs; and cut the warranty burden on automakers—which is likely to be around £780 million in the UK by 2030.

Professor Christensen said that the likelihood of an electric vehicle catching fire is very low, but “we currently don’t have the data on ageing batteries from cars that have been in use for a while. And as we put more and more electric vehicles on the road, there are going to be crashes, and crashes that involve electric vehicles present very different challenges for first responders.”

The Faraday Institution’s £1.5-million SafeBatt project, led by Professor Paul Shearing of University College London and which got underway in 2021, is taking a broad look at the science of battery safety. The project has three elements: „ studying sub-cell level events and the interplay between degradation and safety „ discovering how cell failure propagates within a battery „ carrying out large-scale experiments on full-size battery packs to observe how they behave under stress.

By understanding these processes, automakers will be able to design and build more-reliable battery packs in the future. The SafeBatt project builds on the previous work of the Faraday Institution

“It is really vital that stakeholders across the industry know how to use these batteries safely and what to do if things go pear-shaped. This becomes particularly important as we look at more second-life use cases for Li-ion batteries.”

Degradation and ReLiB (recycling and reuse of Li-ion batteries) projects.

As part of SafeBatt, the Newcastle University team recently spent time testing fire extinguishers proposed for use with Li-ion batteries, with the help of firefighters from the Durham and Darlington Fire and Rescue Service. The extinguishers were used on Li-ion batteries of a size representing typical residential battery energy storage systems.

Professor Christensen is now expanding his research to address how to tackle vapour clouds generated by Li-ion batteries that fail in indoor settings such as tunnels, car parks, and residential buildings.

The growing popularity of e-bikes and e-scooters is a particular concern in this respect; 170,000 of the bikes were sold in the UK in 2020, a 70% year-on-year increase. As these vehicles are usually fitted with Li-ion batteries, and routinely kept and charged indoors by their owners, a fire could have devastating consequences, particularly in shared accommodation in urban areas where access is limited. Professor Christensen is in the process of applying for funding from the Fire Service Research and Training Trust for this research, and he plans to study the vapour clouds by conducting experiments in the full-sized buildings located at the Fire Service College.

“It is really vital that stakeholders across the industry know how to use these batteries safely and what to do if things go pear-shaped. This becomes particularly important as we look at more second-life use cases for Li-ion batteries,” he said.

“This is the most important work I’ve done in my career to date and it’s great to feel I’m doing something valuable and making a difference.”

Professor Christensen’s presentation at the AFAC Knowledge Event Series sponsored by the Motorola Foundation is available to view on AFAC YouTube: www.youtube.com/ channel/UCu18lYmKgFcL27XBKFI7Klw

Find out more about The Faraday Institution’s SafeBatt project: www.safebatt.ac.uk.

This article was republished with permission from the Faraday Institution. See the original article and download the research paper: www.faraday.ac.uk/ success-stories/research-breakthroughincreases-safety-of-lithium-ion-batteries.

Left Professor Christensen presents his findings on Li-ion battery failure events at the AFAC office in Melbourne.