To forge a path towards safer lithium ion batteries, a team at UCL set about studying the mechanisms that cause rapid and catastrophic failure in li-ion batteries
Collaborate To Innovate 2017
Category: Safety & security
Winner: Understanding failure: a path towards safer lithium ion batteries
Partners: UCL; NASA; NREL; European Synchrotron; UK National Physical Laboratory
The year 2013 was one to forget for a pair of high-profile OEMs whose use of lithium-ion batteries in big-ticket transportation technologies resulted in high-profile failure. In the spring of that year, Boeing’s fleet of 50 787 Dreamliners was grounded by regulators after batteries smouldered during a flight over a Japan, and others caught fire on a different aircraft parked at a US airport.
By the autumn, Tesla’s shares plummeted by six per cent after one of its vehicles struck an obstacle and burst into flames. The batteries hadn’t failed, but the collision was said to have set off a chain of events that caused the inferno. In 2015, three airlines halted bulk shipments of lithium-ion batteries in their cargo aircraft after tests by the US Federal Aviation Administration found overheating batteries could cause major fires.
By 2016 the highly competitive world of smartphones was brought into sharp focus by Samsung, which issued a global recall of all Galaxy Note 7 models due to well-publicised anomalies in the handset’s battery that caused phones to smoulder and burn.
Despite sometimes making headlines for the wrong reasons, lithium-ion batteries are a serious player in the energy-generation game. According to Variant Market Research, the global market for li-ion batteries is expected to reach $56bn by 2024 from $25bn in 2016; growing at a compound annual growth rate of 10.6 per cent.
Li-ion batteries are feted for their light weight and high-energy density, which can act against the ubiquitous energy source.
For this reason, a team at UCL set about studying the mechanisms that cause rapid and catastrophic failure in li-ion batteries. It was a journey that saw them work with partners in the UK, France and the US to share knowledge and develop an understanding of the batteries in order to mitigate the risks associated with them.
A key factor of li-ion battery failure is a phenomenon called thermal runaway, which occurs when the rate of heat generated inside a battery exceeds the rate of heat dissipation. When thermal runaway occurs, the battery can transform from being entirely intact to being completely destroyed within a fraction of a second.
Understanding what happens at initiation and during propagation is key to the design of safer li-ion batteries and the team at UCL was the first to hit upon an idea that would capture these events in real time.
One of the project’s leaders, Dr Donal Finegan, who now works at the National Renewable Energy Laboratory (NREL) in the US, said the UCL team combined the European Synchrotron Radiation Facility’s (ESRF) high-energy synchrotron X-rays plus thermal imaging to map changes to the internal structure and external temperature of two types of li-ion batteries that were exposed to extreme levels of heat.
The work built upon observations made previously with X-ray computed tomography (CT), a technique limited to capturing static images after thermal runaway had occurred. The new method, developed in collaboration with ESRF, led to an experimental design that allowed simultaneous high-speed X-ray imaging, thermal imaging and electrochemical spectroscopy while safely inducing catastrophic failure of commercial Li-ion batteries.
Despite this, Finegan said the team were, to an extent, ‘feeling in the dark’ because there was no way of inducing thermal runaway on demand and from a known location within a battery. What the UCL team needed was a device that could induce ‘worse-case scenarios’ on their terms.
A magazine article alerted Finegan to developments in the US, where in October 2015 NREL announced it had patented the internal short circuit (ISC) device, a tiny piece of equipment designed to induce the very conditions that UCL was looking for.
In doing so, the NREL team had provided a marked improvement on other methods of inducing failure that included nail and rod penetration, crushing the battery, applying voltage, or increasing the battery’s temperature.
Dr Eric Darcy, battery technical discipline lead at NASA’s Johnson Space Centre, teamed up with colleagues at NREL to co-develop ISC. Matthew Keyser, NREL senior engineer and one of ISC’s inventors, estimates that the risk of thermal runaway is extremely small: one to 10 in a million cells (one to 10 parts per million) for electronics. Despite the low risks, Finegan explained that they needed a device that would help inform the design and manufacture of li-ion batteries in safety-critical applications such as spacesuits.
Finegan was put into contact with NASA via NREL and was subsequently sent six samples to analyse in the synchrotron. Having the ISC in the batteries meant that the UCL team were able to observe runaway initiate and propagate on their terms. The resulting experiment was the first of its kind, using a custom-made multi-functional battery abuse system, the ISC device, and
X-ray imaging facilities.
The results were well received in the US and the resulting partnership saw NASA and NREL focus on developing and testing an approach that induces ‘worst-case’ failure within commercial and prototype battery designs. UCL and NPL prepare and carry out experiments, while ESRF continues to fine-tune and monitor the imaging conditions and experimental set-ups required for optimal results.
In practice, NREL manufactures the ISC device, carries out quality control and inserts them into prototype batteries with integrated safety devices that are representative of commercial designs. Finegan said the batteries are transported to the NASA Johnson Space Centre where thermal runaway is induced in a small number of ISC-loaded batteries to identify appropriate operating conditions and features of greatest interest to observe using high-speed X-ray imaging at the ESRF. The results and progress from NREL and NASA are conveyed to UCL during weekly conference calls, and the remaining ISC-loaded batteries, along with other samples of interest, are then shipped to UCL for lab-based X-ray CT inspection and preparation for the experiments at the ESRF. The team at UCL and ESRF then prepares and carries out the high-speed imaging experiments at the ESRF in France.
Finegan, who now works at NREL, concluded that UCL’s work with NPL, NASA and NREL has led to the identification of the safest commercial battery designs for aerospace and automotive applications, and that battery manufacturers are now supplying their battery and safety designs for testing.
Shortlisted – Safety & security
Project name: A Zonal CFD Approach for Fully Nonlinear Simulations of Two Vessels in Launch and Recovery Operations (SOCIP)
Partners: Plymouth University; Manchester Metropolitan University; and City University, London
Maritime rescue and recovery operations are often carried out in high sea states, which can result in injury or death if something goes wrong. Consequently, a collaborative project saw four universities and industrial partners investigate the development of a numerical model that can be applied routinely for the analysis of the motion and loadings of two bodies in close proximity, with or without physical connection in high sea states. Such a tool is needed to predict the risk of collisions and unacceptable motions, and to facilitate early testing of new concepts and systems. It is also required to predict loads and motion responses during the deployment of the smaller vessel (such as a lifeboat) from the deck of the larger vessel, and during recovery of the smaller vessel.
The project brought together computational fluid dynamics (CFD) specialists and experimentalists to develop a novel zonal (domain decomposition) modelling approach for launch and recovery, validated by a complementary laboratory programme. The project – made possible via a collaboration between Plymouth University, Manchester Metropolitan University, and City University London – will enable the safety of manoeuvres at sea to be improved and possible future development of real-time simulation tools and automation of operations.
Project name: KROMEK D3S PROJECT
Partners: Kromek; DARPA; Invincea Labs; PSI (Physical Sciences Inc)
The threat of a terrorist-activated radiological dirty bomb is an increasingly real possibility and the ability to detect potential threats against a cluttered and shifting background is immensely challenging.
Kromek, working on DARPA’s SIGMA project, developed an intelligent radiation network that can provide early warning of threat materials and devices made from them. The County Durham-based company combined its non-He3 compact thermal neutron detector and its gamma detector into the ‘Discreet Dual Detector’ (D3S), which is smaller than a mobile phone. This in itself overcame the limitations of existing detectors that are bulky with limited range. D3S identifies sources of radiation across a wide area network that enables specific isotopes to be identified together with their geo-location data, which can be plotted in real time at a centralised location.
The collaboration saw Kromek work with Invincea, the technical authority on the server hardware and network infrastructure; and PSI, the technical authority on the algorithm design. Kromek then worked with its US partners to conduct pilot programmes and real-world deployments during 2016 and 2017, including field testing of more than 1,000 mobile radiation detectors in Washington, DC, and another with the New York Police Department. The impact of this project has been a resounding success, with more than 10,000 detectors shipped so far.
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