Identifying the Cause of Rupture of Li-Ion Batteries during Thermal Runaway.

Donal P Finegan,Thomas M M Heenan,Nghia T Vo,Michael Drakopoulos,Paul R Shearing,Dan J L Brett,Rhodri Jervis,Alexander Rack,Marco Di Michiel,Oxana V Magdysyuk,Matthew Keyser,Bernhard Tjaden,Josh J Bailey,Eric Darcy,Gareth Hinds

doi:10.1002/advs.201700369

Abstract

As the energy density of lithium‐ion cells and batteries increases, controlling the outcomes of thermal runaway becomes more challenging. If the high rate of gas generation during thermal runaway is not adequately vented, commercial cell designs can rupture and explode, presenting serious safety concerns. Here, ultra‐high‐speed synchrotron X‐ray imaging is used at >20 000 frames per second to characterize the venting processes of six different 18650 cell designs undergoing thermal runaway. For the first time, the mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent at the base, which is shown to avoid the critical stages that lead to rupture. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs.

Highlights

The uptake of electric and hybrid electric vehicles (EVs and HEVs) brings forth a rapid increase in the demand for lithiumion batteries alongside an acute need for improvements in their safety and perforper second to characterize the venting processes of six different 18650 cell mance.[1]
The current interrupt devices (CIDs) vent disk on each cell consisted of a conducting plate with a domed structure that was concave with respect to the electrode assembly
The positive temperature coefficient (PTC) switch consisted of a conductive polymer layer between two metallic annular disks that greatly increased in electrical resistance at elevated temperatures

Summary

Introduction

The uptake of electric and hybrid electric vehicles (EVs and HEVs) brings forth a rapid increase in the demand for lithiumion batteries alongside an acute need for improvements in their safety and perforper second to characterize the venting processes of six different 18650 cell mance.[1] As the energy density of batdesigns undergoing thermal runaway. The mechanisms that lead to the most catastrophic type of cell failure, rupture, and explosion are identified and elucidated in detail. The practical application of the technique is highlighted by evaluating a novel 18650 cell design with a second vent teries rises, their safety and reliability becomes increasingly important. The insights yielded in this study shed new light on battery failure and are expected to guide the development of safer commercial cell designs. Amounts of heat which can lead to thermal runaway, accompanied by fire and/or explosion.[2,3,4] the risk of a single cell failing is extremely low, the risk of cell failure within an EV becomes significant

Methods

Results

Conclusion