Researchers from Renmin University and Tsinghua University in China have developed a novel shape-memorized current collector (SMCC), which can successfully brake battery thermal runaway at the battery internal overheating status.

Unlike traditional current collectors made of commercial copper foils, SMCC is made of a micropatterned shape memory micron-sized film with copper deposition. SMCC displays ideal conductivity at normal temperatures and turns to be insulative at overheating temperatures.

Jia et al.

Following this principle, the battery consisting of an SMCC can run normally at temperatures lower than 90 °C, while it quickly achieves self-shutdown before the occurrence of battery combustion and explosion. A paper on their work is published in the ACS journal Nano Letters.

A thermally-responsive shape memory polymer was covered with a conductive copper spray to create a material that would transmit electrons most of the time, but switch to being an insulator when heated excessively.

At around 197 ˚F, a microscopic, 3D pattern programmed into the polymer appeared, breaking apart the copper layer and stopping the flow of electrons. This permanently shut down the cell but prevented a potential fire.

At this temperature, however, traditional cells kept running, putting them at risk of thermal runaway if they became hot again. Under regular operating temperatures, the battery with the new polymer maintained a high conductivity, low resistivity and similar cycling lifetime to a traditional battery cell.

The researchers say that this technology could make Li-ion batteries safer without having to sacrifice their performance.

The authors acknowledge funding from the National Natural Science Foundation of China, the Tsinghua University-China Petrochemical Corporation Joint Institute for Green Chemical Engineering and the Tsinghua-Foshan Innovation Special Fund.

Resources

• Jichen Jia, Hao Liu, Shenglong Liao, Kai Liu, and Yapei Wang (2022) “Early Braking of Overwarmed Lithium-Ion Batteries by Shape-Memorized Current Collectors” Nano Letters doi: 10.1021/acs.nanolett.2c03645