Modeling Li-Ion Battery Temperature and Expansion Force during the Early Stages of Thermal Runaway Triggered by Internal Shorts

Thermal runaway of Li-ion batteries is a major safety issue. It is a complex process involving high heat generation, fast temperature rise and significant amounts of generated gas. Modeling thermal runaway will enable a better understanding and earlier detection of the phenomenon. Since the majority of the thermal runaway incidents are triggered by an internal short circuit, this paper presents a model describing lithium-ion battery thermal runaway triggered by an internal short. In this study, two internal short circuit experiments were conducted on two nickel manganese cobalt oxide pouch cells, one that was fully charged and one half charged. The fully charged cell went into a quick thermal runaway, while the half-charged cell evolved only into a slow, self-discharge process. Both of these experiments demonstrate that a huge battery swelling force signal can be detected prior to the surface temperature rise during an internal short circuit event. This thermal runaway model is the first attempt to connect gas generation with force signal, and successfully capture the early stages of thermal runaway, including the early rise of force signal, after parameter tuning. This model's use of force measurement enables higher confidence in the early detection of thermal runaway induced by an internal short. (C) The Author(s) 2019. Published by ECS.

锂离子电池的热失控是一个主要的安全问题。它是一个复杂的过程，涉及高热量产生、快速升温以及大量气体生成。对热失控进行建模将有助于更好地理解这一现象并实现更早的检测。由于大多数热失控事件是由内部短路引发的，本文提出了一个描述由内部短路引发的锂离子电池热失控的模型。在这项研究中，对两个镍锰钴氧化物软包电池进行了两次内部短路实验，一个是完全充电的，一个是半充电的。完全充电的电池迅速发生热失控，而半充电的电池仅演变成一个缓慢的自放电过程。这两个实验都表明，在内部短路事件中，在表面温度升高之前可以检测到巨大的电池膨胀力信号。这个热失控模型首次尝试将气体产生与力信号联系起来，并在参数调整后成功捕捉到热失控的早期阶段，包括力信号的早期上升。该模型利用力的测量，能够更可靠地早期检测由内部短路引发的热失控。（C）作者2019年。由美国电化学会（ECS）出版。