Lawrence Berkeley National Laboratory scientists developed a new conductive polymer coating which could provide longer lasting and more powerful lithium-ion batteries for electric vehicles.
The polymer coating, called HOS-PFM, can simultaneously conduct electrons and ions to give electric vehicle batters high charge and discharge rates, according a March 7 article issued by Berkeley Lab. The coating also is showing promise as a battery adhesive to extend average lithium-ion battery lifespan from the usual 10 years to 15.
"The advance opens up a new approach to developing EV batteries that are more affordable and easy to manufacture," Gao Liu, senior scientist in Berkeley Lab’s Energy Technologies Area who led the coating's development, said in the article.
HOS-PFM is made of a nontoxic polymer that undergoes a transformation at the atomic level when it is heated. Before the heat exposure, HOS-PFM's alkyl end-chains on its polymer chain limit lithium ion movement, the article reported.
When heated to about 842 degrees Fahrenheit, the alkyl end-chains melt away to create vacant or "sticky" area that grabs onto silicon or aluminum at the atomic level and the polymer chains self-assemble into spaghetti-like hierarchically ordered structures, according to the article.
"Like an atomic expressway, the HOS-PFM strands allow lithium ions to hitch a ride with electrons," the article said. "These lithium ions and electrons move in synchronicity along the aligned conductive polymer chains."
During their experiments, researchers demonstrated the HOS-PFM coating significantly prevents silicon- and aluminum-based electrodes from degrading during battery cycling while at the same time delivering high battery capacity over 300 cycles. That performance rate is on a par with modern state-of-the-art electrodes, the article reported.
HOS-PFM coating could allow use of electrodes in electric vehicle batteries that contain up to 80% silicon, high enough to increase energy density of lithium-ion batteries by at least 30%, according to the article. Silicon is cheaper than graphite, the standard material for electrodes currently used, so using silicon over graphite would mean cheaper batteries that could significantly increase availability of entry-level electric vehicles.
The Berkeley Lab team, whose research is supported by the U.S. Department of Energy's Vehicle Technologies Office and Toyota Research Institute, plans to partner with companies to scale up HOS-PFM for mass manufacturing, the article said.
