During our work within Global Technical Regulations on EV safety and various international standards, a new approach towards thermal runaway/propagation testing of advanced battery packs and systems was developed. We have pioneered a rapid heating testing methodology and in this talk, we will work through its theory and testing criteria while providing examples at the full operational pack and system level. The methodology and related test requirements have been adopted by a number of test agencies worldwide.

The presentation reports numerical and experimental studies of thermal runaway (TR) induced by thermal/nail penetration abuse. It includes some measurements as well as the development and validation of a CFD model for TR evolution and transport of the ejected hot sparks in an enclosed cell cluster. Further analysis in which the validated model is used to fill important experimental gaps will also be discussed in the context of battery thermal management.

Thermal runaway behavior was evaluated by two methods, both using Accelerating Rate Calorimetry (ARC). With the Heat-Wait-Seek (HWS) test, thermal abuse was studied and exothermal reaction temperature rates were evaluated and compared for different cathode materials and states of charge. In addition, nail penetration tests were performed to evaluate the safety during mechanical abuse by puncturing and short-circuiting the cell with a steel nail, accompanied by temperature and video recording.

Safety events are often preceded by some weakly observable electrochemical indicating, for example, plated lithium or an internal short. To detect such a signal, we propose algorithms combining aging reference models and real-time measurements. Reference models indicate the expected performance and aging behavior, while real-time measurements provide corrections to the model and flag unexpected behavior. Machine learning is used both to identify models and interpret measurements.

This talk focuses on the thermochemical behavior of Li-ion batteries and includes three parts: first, the threshold condition of thermal runaway is computationally identified based on minimum ignition energy. Second, mild combustion is introduced, to mitigate thermal runaway and guide battery design. Last, a reaction-conduction theory is developed to describe thermal runaway initiation and propagation.

The temperatures experienced by a cell during operation are critical to safety, performance, and lifetime. To better understand thermal properties and their effects on cell performance we expand on conventional single point measurement to internal temperature monitoring through in situ sensoring, with complimentary cell mapping via thermal imaging. With this enhanced understanding of localised temperatures, improvements in safety and performance, particularly in fast charging, high power application, can be achieved.

Wevo develops and produces resin systems as well as adhesives and sealants primarily for use in electrical and electronic equipment, and in particular for automotive electronics. Here, Wevo products protect sensitive electronic components against humidity, chemicals, high temperatures, dust and foreign matter. In short, Wevo products ensure safety and efficiency.

The Chinese government mandates that passengers must have a 5-minute window to exit their vehicle after detection of thermal runaway. While this is a step forward, a better goal is to stop thermal propagation. Single-cell thermal runaways that propagate to module-, pack-, or vehicle-level will, even at low incident rates, dampen acceptance of BEVs. Discover how aerogel-based thermal barrier materials can help achieve this goal within space, weight, and cost constraints.

Your product is only as good as the battery! Unfortunately, battery product failures can happen at any time. What should you do when you experience a battery failure? Why even bother with battery failure analysis? What can it teach you about selecting the correct battery solution – and battery supplier – for your products? Should your battery supplier or a 3rd party be used to conduct the investigation? One of the compelling reasons for a detailed failure analysis is it results in better yields, profitability, and better business. Failure analysis leads to knowledge, which leads to improvement

The fire and smoke components released during a lithium-ion fire have been characterized and the challenges of putting out such a fire will be discussed. Cells of different cathode chemistries and at different states of charge were taken into thermal runaway and the smoke and fire composition was analyzed. ASTM methods were used to determine the lower flammability limits for the gases released and the data will be shared during the talk.

Despite having multifarious Electric Vehicle (EV) battery testing standards, there have been, few severe accidents noticed recently that have resulted in some reservations by the EV consumers, hindering the deployment of the EV. Hence, it becomes crucial to experimentally investigate the speed at which the batteries are crushed to understand its failure mechanism and to look into the safety of EV consumers and the necessity for the harmonization of multifarious globally available standards.

Understanding the risks associated with thermal runaway of LIBs is critical for designing safe cells and battery systems. The thermal response of cells can greatly vary for identical cell designs tested under identical conditions, the distribution of which is costly to fully characterize experimentally and cannot be captured by deterministic models. The Battery Failure Databank contains robust, high-quality data from hundreds of abuse tests spanning numerous commercial cell designs and abuse testing conditions. Data was gathered using a fractional thermal runaway calorimeter and contains the fractional breakdown of heat and mass from ejected and non-ejected cell contents, as well as high-speed radiography of the internal structural response of cells during thermal runaway. This presentation will provide an overview of the Battery Failure Databank as well as insights gained from in situ radiography of internal causes of outlier battery failure events.

Safety is critical to the wide adoption of lithium battery technology in all applications.  This talk focuses on how an internal fuse, called SafeCore, within the individual battery cell can help prevent thermal runaway due to overcharge or internal short and can delay thermal runaway in certain high temperature environments.  Cell abuse data, Accelerating Rate Calorimetry testing and SEM images on cells with SafeCore and without will be reviewed.  

Practicing and utilizing concepts in lean methodologies lead naturally to safer, and more efficient battery testing. By creating scenarios for managing high-density testing in small batches, it increases safety and reduces cost per channel.

Behind-the-Meter Storage (BTMS) systems are envisioned to be the solution that can minimize grid stability challenges posed by high penetration of electrical vehicles in the market. However, the hazards associated with lithium-ion batteries used in BTMS applications become reality. In light of this, a strategy based on leveraging advanced thermal design and battery management system is being developed to enable a fail-safe rack design.

Characterizing propagation of a thermal runaway hazard in cell arrays and modules is critical to understanding fire hazards in energy storage systems. In this talk, the thermal runaway propagation of a pouch cell array has been examined by developing a 1D finite difference model.

To protect passengers from the negative impact of thermal runaways, standards like GB 38031-2020 are introduced. One way to comply with these is to prevent hot particles, created by cell explosion, from being ejected into the environment, so they cannot ignite flammable gas/air mixtures outside the pack. Adding hot particle filter functionality to venting units as shown in the presentation is an innovative solution addressing these new requirements.

I will present LMFP/NMC cells that can provide a total solution to safety, capacity, power, life and cost issues with EV batteries. The 4V olivine-structured LMFP, which we synthesized, had a discharge capacity of 150 mAh/g as well as excellent rate capability (>15C) and life >5000 cycles. We found that LMFP/NMC cells with a dual-layer electrode structure exhibited much improved safety, rate capability and cycle life, compared with the LMFP/NMC blend and NMC counterparts. The underlying mechanisms will be discussed.