Operando Analysis of Thermal Runaway in Lithium Ion Battery during Nail-Penetration Test Using an X-ray Inspection System

Abstract

The thermal runaway of a lithium ion battery (LIB) during a nail-penetration test was investigated using an LIB internal short circuit observation system equipped with an X-ray scanner (LiSC scanner). Using high-speed moving images and high-precision voltage measurements, the layer-by-layer internal short circuit caused by the nail was clearly observed during nail motion. Following this motion, gas generation outside the cell, which is well-known in thermal runaway, was observed. The main causes of smoke are speculated to be the boiling of the electrolyte and/or decomposition of the active materials owing to heating by the short circuit current. The initial behavior of the short circuit before gas generation was clearly observed. Therefore, gas generation, which is well-known to indicate an internal short circuit of the cell, and the electrical behavior of the short circuit during the nail-penetration test were observed separately. This LiSC scanner allowed us to analyze the details of the internal short circuit of the cell, and it is expected to lead to significant advancements in the safety of LIBs.

On The Impact of the Locality on Short-Circuit Characteristics: Experimental Analysis and Multiphysics Simulation of External and Local Short-Circuits Applied to Lithium-Ion Batteries

“…[18][19][20] In order to reproduce such a field-like shorting scenario, the test must trigger the shorting only at a single site, set a low ohmic resistance, form over time/operation of the LIB, and should reveal sufficient reproducibility. Adjusting the locality of the short-circuit seems to be viable regarding the range of already existing test procedures including a complete or partial penetration the LIB with a nail or needle 21 or the insertion of local defects during assembly of the battery, 22 whereas controlling the shorting resistance may only be partly viable due to the variety of possible materials and contact conditions between the electrodes and current collectors 23 as well as possible changes during the shorting scenario. 24 The formation over time can hardly be recreated by experimental methods as the aforementioned defects form over the lifetime of LIBs and exceed practical operation times of safety tests by far.…”

“…24 The formation over time can hardly be recreated by experimental methods as the aforementioned defects form over the lifetime of LIBs and exceed practical operation times of safety tests by far. As a result, existing tests such as nail penetration 21,[24][25][26][27][28][29] or the more complex modification of LIB via insertion of local defects in the electrode stack/jelly roll 22,30 cannot satisfactorily simulate a real, field-like ISC scenario but at least approximate similar high current scenarios with a strong local heat generation.…”

Lithium-ion Battery Thermal Safety by Early Internal Detection, Prediction and Prevention

“…Current collector dissolution and gas generation influenced cell impedance and local heat transfer condition 40,41 . Electrode particle could delaminate during thermal runaway 42 , leading to abrupt drop in cell capacity and heat generation rate at the region of delamination. Current collector dissolution and electrode particle delamination observed in short circuit test can be found in Supplementary Fig.…”

X‐ray Tomography and Tomoscopy on Metals: A Review

“…[292] A greater challenge in the tomographic analysis of battery systems is the investigation of processes much faster than cycling as for example during cell failure. Yokoshima et al applied fast X-ray radioscopy for an operando analysis of thermal runaway in lithium-ion batteries during penetration by a nail [293] while Patel et al investigated the thermal runaway of a lithiumion battery combining accelerating rate calorimetry and multilength scale ex-situ laboratory X-ray tomography. [294] For the analysis of lithium-ion battery case ruptures Kong et al applied ex situ X-ray tomography.…”