Researchers from Renmin and Tsinghua Universities in China have developed a novel shape-memory current collector (SMCC) that they say can stop battery thermal runaway in an overheated battery. Their paper, Early Braking of Overwarmed Lithium-Ion Batteries by Shape-Memorized Current Collectors, is published in the ACS journal Nano Letters.
Unlike traditional current collectors made of copper foils, the SMCC is made of a micropatterned shape-memory micron-sized film with copper deposition. According to the researchers, it displays ideal conductivity at normal temperatures and becomes insulative at overheating temperatures; a battery containing an SMCC normally runs at temperatures lower than 90° C (194° F), but if it overheats, it quickly performs self-shutdown before the occurrence of battery combustion and explosion.
The research was conducted by covering a thermally responsive shape-memory polymer with a conductive copper spray, resulting in a material that transmits electrons most of the time but switches to being an insulator when excessively heated.
When the battery reached a temperature of about 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 and prevented a potential fire.
The researchers say that at normal operating temperatures, the battery with the new SMCC maintains high conductivity, low resistivity and a cycling life span similar to that of a traditional battery cell. With this technology, they say, batteries can be safer with no sacrifice in performance.