SafeBatt – Science of Battery Safety

Even with billions of Li-ion batteries (LiBs) in circulation there are very few accidents involving them, which is testament to how safe they are. Whilst battery fires are rare, they can occur under various conditions of mechanical, thermal or electrical stress or abuse. Operation of batteries under abnormal conditions can lead to a significant temperature rise, as well as the venting of toxic, flammable gases, which can ignite, leading to a fire.

Safety control and countermeasures are built into the design of today's LiB systems, but this adds complexity, cost and weight. As the use of LiBs expands further into automotive, stationary storage, aerospace and other sectors, there is a need to decrease the risk associated with battery usage further and to enable the simplification of safety systems. This can only be achieved through enhanced understanding of the “science of battery safety”.

This project will improve the fundamental understanding of the root causes of cell failure and the mechanisms of failure propagation. Working closely with industry partners, a multi-scale approach is being taken, from the material to the cell and module scale. This is necessary because the triggers for cell failure are varied and may result from microscopic, internal heterogeneities (e.g., lithium metal plating during charge or manufacturing defects) or from external factors, such as vehicle crash or external heating. Whilst the nucleation of failure may be a microscopic event, the propagation of failure, in particular cell-to-cell propagation, is macroscopic. Research spans time frames from the degradation of materials over hundreds of charging cycles, down to the nucleation and propagation of failure with characteristically sub-second events.

The project is also developing an improved understanding of processes occurring during real world failure, including the environmental consequences of LiB fires, which will inform the further development of fire sensing and protection systems for warehouse storage and battery energy storage systems (BESS) and help develop a consensus around the optimal method of fighting large LiB fires, be they the result of traffic collisions or at LiB recycling facilities.

The project builds from the success of an industry sprint and builds on research previously carried out in the Faraday Institution Battery Degradation and ReLiB Recycling and Reuse projects in what is a new co-ordinated research effort beginning in April 2021.

Project funding
£1.52m
1 April 2021 – 31 March 2023
Principal Investigator
Professor Paul Shearing
UCL
Project Leader
Dr Julia Weaving
UCL
University Partners
UCL (Lead)
University of Cambridge
Imperial College London
Newcastle University
University of Sheffield
University of Warwick
+ 2 Industry Partners

Objectives

The project will:

At the materials level:

  • Identify the safety signatures of state-of-the-art Li-ion cells and examine how these signatures are affected by cell design and how they change over cell lifetime.
  • Consider how transition metal migration and deposition influences battery lifespan and safety.
  • Develop an improved understanding of redeposition of copper from the anode current collector to inform design strategies that minimise the potential for short circuits.
  • Improve the understanding of the signatures of degradation and rapid cell failure as a result of fast charging and operation at extreme temperatures. This will provide a toolbox to evaluate new materials/components and operational strategies to mitigate the risk of catastrophic failure.

Understand catastrophic cell failure:

  • Use state-of-the-art measurement and characterisation techniques as well as high speed synchrotron facilities, including those at Diamond Light Source, to compare the behaviour of as-manufactured (fresh) and degraded cells to correlate degradation and safety behaviours. This will give insight into cell failure modes and how they might change with cell ageing/degradation, as well as how they translate to multi-cell modules.
  • Understand how materials and architectures affect failure modes, thermal signatures and gas evolution.
  • Develop an advanced single cell model to infer reactions and kinetics during failure, and predict off-gas release behaviour and the structural origins and pathway of thermal runaway.
  • Inform computer modelling capabilities of UK industry partners, allowing industry partners to refine battery pack designs computationally before choosing the most promising designs and building physical test articles to be destructively tested. This will lead to a faster, cheaper, more efficient battery pack development process.

At a systems and processes level:

  • Conduct responsive failure analysis to inform best practices and improve first responders’ understanding of LiB fires. With close interaction between industry, government and first responders, these findings will be disseminated via publications and the development of new standards and policies.
  • Assess the behaviour of domestic BESS, both new and repurposed, in fires.
  • Investigate the potential application of sensing (e.g., gas, temperature) for human and asset protection in facilities using LiBs.
  • Assess the efficacy and environmental consequences of specialist LiB fire extinguishing and suppression systems.
  • Contribute to the development of new standards for cell and module qualification in collaboration with national measurement institutes, e.g., NPL (UK) and NIST (US).

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