In-operando high-speed tomography of lithium-ion batteries during thermal runaway.

Donal P Finegan,Gareth Hinds,Gregory J Offer,James B Robinson,Bernhard Tjaden,Marco Di Michiel,Mario Scheel,Thomas J Mason,Jason Millichamp,Ian Hunt,Paul R Shearing,Dan J.L Brett

doi:10.1038/ncomms7924

Abstract

Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries. Here, we demonstrate for the first time the application of high-speed synchrotron X-ray computed tomography and radiography, in conjunction with thermal imaging, to track the evolution of internal structural damage and thermal behaviour during initiation and propagation of thermal runaway in lithium-ion batteries. This diagnostic approach is applied to commercial lithium-ion batteries (LG 18650 NMC cells), yielding insights into key degradation modes including gas-induced delamination, electrode layer collapse and propagation of structural degradation. It is envisaged that the use of these techniques will lead to major improvements in the design of Li-ion batteries and their safety features.

Highlights

Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries
The reconstructed tomograms consist of grey-scale image stacks in which the most highly X-ray-attenuating materials are displayed as white and the least attenuating as black; steel and copper are highly attenuating materials and are displayed as white in the tomography and radiography images
The nickel manganese cobalt oxide (NMC) electrode material is displayed as bright grey

Summary

Introduction

Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries. A temperature increase within the cell can trigger thermally induced degradation; for example, between 90 °C and 120 °C heat generation and gas evolution at the negative electrode occurs due to breakdown of the solid electrolyte interphase (SEI) and reaction between the lithiated carbon and the electrolyte[8,9]. There have been studies on compositional and structural evolution of electrode materials at elevated temperatures[19,20], there is limited understanding of the change in the internal architecture of commercial cells leading up to and during thermal runaway and failure. Improved understanding of the internal structural dynamics during failure and thermal runaway of commercial cells should help cell developers to design effectively against the initiation and propagation of failure

Methods

Results

Conclusion