I don’t really drive enough to make an electric vehicle (EV) a compelling value proposition, but if my commute was a bit longer it is something I would seriously consider.
However, there is one aspect of EVs that makes me a little nervous. Although rare, lithium-ion batteries can fail, resulting in a fire. This fire can spread to other cells, and can ultimately explode in a thermal runaway. This slight risk would probably cause me to think twice about charging an EV in my garage at night.
There are potential solutions to this problem. Last year I wrote about A Battery That Could Change The World, which was a story about the development of a solid-state lithium battery that won’t catch fire if damaged.
However, today’s lithium-ion batteries aren’t going away anytime soon. So, one company has developed a potential solution to the fires that can be spawned from lithium-ion battery failures.
California-based KULR Technology, in partnership with NASA, has developed a product to stop lithium-ion battery packs from exploding in thermal runaway.
NASA is interested in this problem because of the potential for a catastrophic failure in space. A runaway thermal event from these batteries may be a low-probability event, but on a spacecraft or in a spacesuit, the consequences could be devastating.
The solution that has been developed involves the placement of a vaporizing thermal capacitor next to the individual cells. If a cell fails and the temperature starts to climb rapidly, the heat will be dissipated in the thermal capacitor. You can think of it as analogous to an electrical fuse that will fail to stop a surge of electrical current.
In addition to the thermal capacitor, which they call the HYDRA thermal runaway shield (TRS), each cell also contains a flame arrestor to block the fire from reaching surrounding cells. This solution prevents adjacent cells from rising above 100°C. This is important, because at temperatures above 130°C, the chance for a short in adjacent cells rises substantially.
You can see a demonstration of some early NASA tests with the TRS. In this video, a failure is triggered in a single cell in a 50-cell pack. You can see the explosion at the 2:40 mark in the video. The temperature of the triggered cell reportedly rose above 1000°C, but neighboring cells all remained below 100°C.
There is certainly a need to get a better handle on understanding the root cause of these failures, because the number of these batteries in applications is growing exponentially. Even one failure in a billion is unacceptably high when there are billions of these cells in use.
As these battery packs become more powerful — and because of the potential for high-consequence incidents like a fire on an airplane — the need for fire suppression will grow. The long-range solution may be a new type of battery, but the solution developed by KULR and NASA could greatly enhance the safety of existing lithium-ion battery packs.
