Lithium-ion batteries are a popular choice for rechargeable batteries for use in many applications such as portable electronics, electric vehicles, small and large appliances, and energy storage systems thanks to the large amount of energy they can store in a small space. However, a fire and explosion would likely result if the battery were subjected to overheating where separator shrinkage routinely causes an internal short circuit.
To address this problem, a team of researchers from China has proposed a possible solution using new technology that can quickly brake a Li-ion battery and shut down the battery if it gets too hot.
When multiple lithium-ion cells are daisy-chained together – as in electric vehicles – thermal runaway can spread from one unit to the next, resulting in a very large, difficult-to-fight fire. So the researchers wanted to develop a lithium-ion battery that would turn itself off quickly, but would work just as well as existing technologies.
For the new research, the researchers used a thermally-responsive shape-memory polymer covered in a conductive copper spray to create a material that transmits electrons most of the time but becomes an insulator when heated excessively.
At temperatures below 90 °C, a microscopic 3D pattern programmed into the polymer appeared, breaking the copper layer and stopping the flow of electrons. This shut down the cell permanently, but prevented a potential fire. At this temperature, however, conventional cells continued to run, which put them at risk of thermal runaway if they got hot again.
Under normal operating temperatures, the battery with the new polymer maintained high conductivity, low resistivity and a cycle life similar to that of a conventional battery cell. The researchers say this technology could make Li-ion batteries safer without sacrificing performance.
Magazine reference:
- Jichen Jia, Hao Liu, Shenglong Liao, Kai Liu, and Yapei Wang. Premature braking of overheated lithium-ion batteries using shape memory pantographs. Nano Letters, 2022; DOI: 10.1021/acs.nanolett.2c03645
