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The investigation of thermal runaway propagation of lithium‑ion batteries under different vertical distances Changfa Tao1 · Guangyu Li1 · Jianbo Zhao1 · Guang Chen2 · Zhigang Wang2 · Yejian Qian1 · Xiaozhang Cheng1 · Xiaoping Liu3 Received: 6 September 2019 / Accepted: 2 January 2020 © Akadémiai Kiadó, Budapest, Hungary 2020

Abstract The time of safety valve cracks and thermal runaway propagation are influenced seriously by vertical distance and the stage of charge (SOC). In this study, a series of experiments with four lithium-ion batteries has been finished to evaluate the fire hazards by in situ calorimeter. The temperature of safety valve crack is inversely proportional to the SOC. For upper batteries of 0, 50 and 100% SOC, the safety valve was not cracked at 3, 5 and 8 cm, respectively. The safety valve crack time is an exponential function of distance for 50% and 100% SOC. The ­SO2 can be obviously found under a high temperature for the fully charged batteries. Keywords  Safety valve crack · Thermal runaway propagation · Lithium-ion batteries · Vertical distances

Introduction Lithium-ion batteries (LIBs) have been used in numbers of electric equipment and systems, such as electric vehicles and electric boat [1]. Comparing to traditional battery, the LIBs can provide a higher energy density and longer cycle life [2]. There are some potential safety problems for the LIB. LIB abuse inevitably occurs in daily life, such as overcharge, crush, nail, fall, immersion and overheating [3–5], which will lead to fire and explosion eventually. Moreover, when the batteries are used in energy storage, once the thermal runaway of battery occurs, more serious fire disaster will be brought. Huang et al. [6] tracked the fire spread behavior over several 50 Ah LIBs and also numerically investigated the critical temperature of TR propagation using the measured data from C80 calorimeter. They focus on the thermal runaway propagation of vertically adjacent LIBs, while the LIB is put at horizontal direction. Thermal runaway brings * Xiaoping Liu [email protected] 1



School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei 230009, Anhui, China

2



State Grid Electric Power Research Institute (NARI Group Corporation), Nanjing 210003, China

3

School of Civil Engineering, Hefei University of Technology, No. 193, Tunxi Road, Hefei 230009, Anhui, China



a high temperature inside the battery, with a series of chemical reactions, such as decomposition of solid electrolyte interface layer (SEI) at 90–120 °C and reaction of intercalated lithium with the electrolyte at elevated temperature (> 120 °C) [6]. With the increase in temperature, internal short circuit occurs while some oxygen released from the decomposition of cathode material. It has been taken lots of attention by the safety accidents of LIBs [7]. In the previous studies, most of the attention was focused on the reasons of thermal runaway and thermal stability of anode, cathode, separator and electrolyte [8–13]. Chen et al. [14] demons