Over the last decade, the electric vehicle (EV) has significantly changed the car industry globally, driven by the fast development of Li-ion battery technology. However, the fire risk and hazard associated with this type of high-energy battery has become a major safety concern for EVs. This review focuses on the latest fire-safety issues of EVs related to thermal runaway and fire in Li-ion batteries. Thermal runaway or fire can occur as a result of extreme abuse conditions that may be the result of the faulty operation or traffic accidents. Failure of the battery may then be accompanied by the release of toxic gas, fire, jet flames, and explosion. This paper is devoted to reviewing the battery fire in battery EVs, hybrid EVs, and electric buses to provide a qualitative understanding of the fire risk and hazards associated with battery powered EVs. In addition, important battery fire characteristics involved in various EV fire scenarios, obtained through testing, are analysed. The tested peak heat release rate (PHHR in MW) varies with the energy capacity of LIBs ($$E_{B}$$ in Wh) crossing different scales as $$PHRR = 2E_{B}^{0.6}$$. For the full-scale EV fire test, limited data have revealed that the heat release and hazard of an EV fire are comparable to that of a fossil-fuelled vehicle fire. Once the onboard battery involved in fire, there is a greater difficulty in suppressing EV fires, because the burning battery pack inside is inaccessible to externally applied suppressant and can re-ignite without sufficient cooling. As a result, an excessive amount of suppression agent is needed to cool the battery, extinguish the fire, and prevent reignition. By addressing these concerns, this review aims to aid researchers and industries working with batteries, EVs and fire safety engineering, to encourage active research collaborations, and attract future research and development on improving the overall safety of future EVs. Only then will society achieve the same comfort level for EVs as they have for conventional vehicles.

A review of battery fires in electric vehicles

A review on recent progress, challenges and perspective of battery thermal management system

A perspective on sustainable energy materials for lithium batteries

The evolving global landscape for electrical distribution and use created a need area for energy storage systems (ESS), making them among the fastest growing electrical power system products. A key element in any energy storage system is the capability to monitor, control, and optimize performance of an individual or multiple battery modules in an energy storage system and the ability to control the disconnection of the module(s) from the system in the event of abnormal conditions. This management scheme is known as “battery management system (BMS)”, which is one of the essential units in electrical equipment. BMS reacts with external events, as well with as an internal event. It is used to improve the battery performance with proper safety measures within a system. Therefore, a safe BMS is the prerequisite for operating an electrical system. This report analyzes the details of BMS for electric transportation and large-scale (stationary) energy storage. The analysis includes different aspects of BMS covering testing, component, functionalities, topology, operation, architecture, and BMS safety aspects. Additionally, current related standards and codes related to BMS are also reviewed. The report investigates BMS safety aspects, battery technology, regulation needs, and offer recommendations. It further studies current gaps in respect to the safety requirements and performance requirements of BMS by focusing mainly on the electric transportation and stationary application. The report further provides a framework for developing a new standard on BMS, especially on BMS safety and operational risk. In conclusion, four main areas of (1) BMS construction, (2) Operation Parameters, (3) BMS Integration, and (4) Installation for improvement of BMS safety and performance are identified, and detailed recommendations were provided for each area. It is recommended that a technical review of the BMS be performed for transportation electrification and large-scale (stationary) applications. A comprehensive evaluation of the components, architectures, and safety risks applicable to BMS operation is also presented.

Review of Battery Management Systems (BMS) Development and Industrial Standards

Mechanism, modeling, detection, and prevention of the internal short circuit in lithium-ion batteries: Recent advances and perspectives

Thermal runaway characteristics and failure criticality of massive ternary Li-ion battery piles in low-pressure storage and transport

Thermal decomposition of pine branch: Unified kinetic model on pyrolytic reactions in pyrolysis and combustion

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.

Thermal-Runaway Propagation over a Linear Cylindrical Battery Module

Pyrolysis of forest combustibles is an elementary process in the ignition and spread of forest fires, and particle size is an important parameter which affects the pyrolysis kinetics. In this work, samples of pine needle (PN), pine branch (PBr) and pine bark (PB) were subject to thermogravimetric experiments, in order to examine the effect of particle size on pyrolysis characteristics. For all the samples, one peak and two shoulders are observed in all of the mass loss curves, at different positions for different levels of particle size. The observation of the mass loss curves and the analysis of peak temperatures by Kissinger method indicated that the major mass loss steps in different heating rates have consistent pyrolysis kinetics. For all the samples, the particle size has no obvious effect on the temperatures of the major peaks. Basically, the peak mass loss rate increases with increasing particle size for smaller particles, however the increased temperature gradient inside the sample may have a remarkable suppression on the mass loss rate when the particle size exceeds a certain level. The mass loss rates for the two shoulders show complex variations for different samples and particle sizes, which reflects the difference in chemical components. A kinetic model which includes three pseudo components was used to simulate the pyrolysis for different dimensions, and the obtained kinetic parameters were compared and discussed in details. By industrial analysis the products of ashes for different particle sizes were compared, and especially it was implied that to some extent the activation energy and ash content involve negative correlation.

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Niu Huichang

Papers

A review of battery fires in electric vehicles

Thermal runaway characteristics and failure criticality of massive ternary Li-ion battery piles in low-pressure storage and transport

Thermal decomposition of pine branch: Unified kinetic model on pyrolytic reactions in pyrolysis and combustion

Thermal-Runaway Propagation over a Linear Cylindrical Battery Module

Effect of Particle Size on Pyrolysis Kinetics of Forest Fuels in Nitrogen