• PDF / 2,632,009 Bytes
• 17 Pages / 439.37 x 666.142 pts Page_size
• 0 Downloads / 176 Views

DOWNLOAD

REPORT

---

Thermal-Runaway Propagation over a Linear Cylindrical Battery Module Huichang Niu*, Caixing Chen, Dan Ji, Lei Li and Zhao Li, Institute of Industry Technology, Guangzhou & Chinese Academy of Sciences, Guangzhou, China Yanhui Liu and Xinyan Huang*, Research Center for Fire Engineering, Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China Received: 30 September 2019/Accepted: 24 March 2020

Abstract. Thermal-runaway propagation in battery systems can escalate the battery fire hazard and pose a severe threat to global users. In this work, the thermal-runaway propagation over 18650 cylindrical lithium-ion battery was tested in the linear-arranged module with a 3-mm gap. State of charge (SOCs) from 30% to 100%, ambient temperatures from 20°C to 70°C, and three tab-connection methods were investigated. Results indicate that the battery thermal-runaway propagation speed was about 0.35 ± 0.15 #/ min, which increased with SOC and ambient temperature. The critical surface temperature of thermal runaway ranged from 209°C to 245°C, which increased with ambient temperature while decreased with SOC. Compared to the open-circuit module, the flat tab connection could cause an external short circuit to accelerate the thermal-runaway propagation, and the non-flat tab connection was more likely to trigger an explosion. A heat transfer analysis was proposed to qualitatively explain the speed and limiting conditions of thermal-runaway propagation, as well as the influence of SOC, ambient temperature, and tab connection. This work reveals the thermal-runaway propagation characteristics under well-controlled environments, which could provide scientific guidelines to improve the safety of the battery module and reduce battery fire hazards. Keywords: Lithium-ion battery, Thermal runaway, Critical temperature, Propagation speed, 18650 battery List of Symbols A c E h m n Q Q_ r

Heat transfer area (m2) Specific heat (J/kg K) Electric energy (J) Heat transfer coefficient (W/m2/K) Mass (kg) Number of cells (–) Heat (J) Heat release rate (W) Propagation rate (#/min)

* Correspondence should be addressed to: Huichang Niu, E-mail: [email protected]; Xinyan Huang, E-mail: [email protected]

1

Fire Technology 2020 Rt t T

Total heat resistance (m2/W) Time (min) Temperature (°C)

Subscripts 0 a b es

Initial Ambient Battery External short circuit

Abbreviations ARC EV LIB SOC TC TR

Adiabatic rate calorimeter Electric vehicle Lithium-ion battery State of charge Thermocouple Thermal runaway

1. Introduction Lithium-ion batteries (LIBs) are widely used in electronic facilities and electric vehicles (EVs) for the merits of high energy density and long cycle life. However, fire or explosion hazards of LIBs initiated by the thermal runaway, when exposed to extreme conditions such as heat abuse, overcharge, crush, etc., present significant threats over lives [1–5]. Consequently, there is a big fire-safety concern on LIBs. Despite lots of understandings of the mechanism of thermal runaway and the developments o