TUT4: Managing and Understanding the Risks of Li-Ion Battery Safety



This tutorial provides insights regarding processes that lead to thermal runaway in Li-ion cells, why all thermal runaway processes are not the same and how thermal runaway can be better understood and managed. There are fundamental differences between how cells respond to various stresses and, unfortunately, still too-common misunderstandings of the causes of thermal runaway. These misunderstandings can seriously complicate battery safety management. The tutorial continues to provide the basis for a clearer understanding of cell- level processes that result in thermal runaway.

Increasingly, questions are arising regarding how thermal runaway in a single cell can lead to propagation in other cells in a battery pack. Many battery engineers are considering the viability of a “single-fault-tolerant” battery design as a realistic alternative (or at least a useful “what-if”) to a battery that never experiences any cell safety failures. In a single fault tolerant battery design, a single cell thermal runaway failure does not result in propagation of thermal runaway failures in any other cells in the pack. Increasingly the question of how to proactively design batteries that build in a single fault tolerance are arising.

As difficult as it can be to understand the different sides of thermal runaway for single cells, it is even more complex to understand how propagation occurs and what means are available to inhibit propagation. A larger array of factors is typically involved. Thermal runaway of an initial single cell in a battery pack involves release of (a variable amount of) thermal energy in the form of both gases and solids. These high temperature gases and ejecta, which can exhibit considerable variability in their characteristics, can trigger subsequent thermal runaway of other cells in a pack in a number of unexpected ways. Provision for safely managing these effects are required. It’s important to understand the factors involved in limiting propagation and to learn about some of the new tools being applied to this problem. The tutorial has added coverage of these topics.

The design of a single-fault-tolerant battery is subject to a wide variety of engineering considerations and can be very complicated, depending on the battery design options, especially as higher energy density cells are employed. The tutorial has added consideration of the factors that must be taken into account to limit propagation (or cascading) as well as to obtain better data to support engineering of safer battery packs with respect to propagation.


Barnett_BrianBrian Barnett, PhD, President, Battery Perspectives LLC

Brian Barnett recently founded Battery Perspectives LLC, a company providing consulting services related to battery technology and battery safety. Dr. Barnett has extensive experience in assessment, development and commercialization of battery technology and is recognized as both a technical and industry expert related to batteries and an expert in battery safety. He has directed a series of successful lab-based, highly multidisciplinary battery technology development programs that resulted in technology licensing or sale.

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