Thermal Abuse Tests on 18650 Li-Ion Cells Using a Cone Calorimeter and Cell Residues Analysis

Energies

Sofia Ubaldi¹  Maria Paola Bracciale¹  Paola Russo¹  Maria Luisa Mele¹  Maria Laura Santarelli¹  Michele Mazzaro²  Cinzia Di Bari³ 

[1] Department of Chemical Engineering Materials Environment, Sapienza University of Rome, Eudossiana 18, 00184 Rome, Italy;Direzione Centrale per la Prevenzione e la Sicurezza Tecnica, Corpo Nazionale dei Vigili del Fuoco, 00178 Rome, Italy;ENEA DTE-PCU-STMA, CR Casaccia, Anguillarese 301, 00123 Rome, Italy;

关键词: lithium-ion cell;    thermal runaway;    cone calorimeter;    SoC;    over-discharge;    DSC;   

DOI  :  10.3390/en15072628

来源: DOAJ

【 摘 要 】

Lithium-ion batteries (LIBs) are employed when high energy and power density are required. However, under electrical, mechanical, or thermal abuse conditions a thermal runaway can occur resulting in an uncontrollable increase in pressure and temperature that can lead to fire and/or explosion, and projection of fragments. In this work, the behavior of LIBs under thermal abuse conditions is analyzed. To this purpose, tests on NCA 18,650 cells are performed in a cone calorimeter by changing the radiative heat flux of the conical heater and the State of Charge (SoC) of the cells from full charge to deep discharge. The dependence of SoC and radiative heat flux on the thermal runaway onset is clearly revealed. In particular, a deep discharge determines an earlier thermal runaway of the cell with respect to those at 50% and 100% of SoC when exposed to high radiative heat flux (50 kW/m²). This is due to a mechanism such as an electrical abuse. Cell components before and after tests are investigated using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy—Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-ray Diffraction (XRD) to determine the structural, morphological, and compositional changes. It results that the first reaction (423–443 K) that occurs at the anode involves the decomposition of the electrolyte. This reaction justifies the observed earlier venting and thermal runaway of fully charged cells with respect to half-charged ones due to a greater availability of lithium which allows a faster kinetics of the reaction. In the cathode residues, metallic nickel and NO are found, given by decomposition of metal oxide by the rock-salt phase cathode.

【 授权许可】

Unknown