Understanding Thermal Runaway in Lithium-ion Batteries

When you hear about Lithium-ion battery safety, Thermal runaway is a very commonly talked about term. The purpose of this article and the attached video is to explain Thermal runaway in an intuitive way, so that the fear around it is a little less and the understanding a little more.

As the name suggests, thermal runaway is a negative cyclic reaction that leads to a high temperature and pressure environment inside a Lithium-ion cell. This in its most extreme case can cause a fire, although many times the thermal runaway cycle is broken much before that through safety features built inside the cell and in surrounding electronics like the Battery Management System.

Thermal runaway takes place in multiple stages. It needs to start with a trigger, which can either be a rule violation caused by the product or improper use of the product or in some cases an internal cell failure as well.

Once the first stage of thermal runaway in activated, the reactions that take place inside the cell are exothermic in nature. These reactions then further catalyse stage 2 followed by stage 3 of thermal runaway. At each stage, there can be safety checkpoints put in place to stop the negative chain reaction and hence stop thermal runaway.

If all of these safety checkpoints fail for a single cell, another safety measure a battery pack maker should integrate into the design is to impede cell to cell failure propagation. So that if one cell goes into thermal runaway, the temperature of the surrounding cells is still controlled within limits so as to isolate the failure as much as possible.

Battery safety is a growing concern as we see more energy dense Lithium-ion batteries being used in automobiles, aerospace, defence, stationary storage and portable electronics. We've encapsulated lessons from such recent failures in the form of a course to assist manufacturers in strengthening their internal Battery design and QA processes to ensure safety of devices, vehicles and consumers. Check out this course below to learn more.