Engineering news
Researchers at Drexel University in Philadelphia think they’ve found a way to make it possible, by changing the way electrodes in batteries are designed.
A team led by Yury Gogotsi, a professor in the university’s college of engineering, used a highly conductive two-dimensional material called MXene to construct their new electrodes.
According to Gogotsi, MXene could help bring chemical storage devices up to the charging speed of supercapacitors, which don’t use chemical storage, and are employed for short bursts of energy such as camera flashes.
“We demonstrate charging of thin MXene electrodes in tens of milliseconds,” he said. “This is enabled by very high electronic conductivity of MXene. This paves the way to development of ultrafast energy storage devices than can be charged and discharged within seconds, but store much more energy than conventional supercapacitors.”
The capacity of a battery is determined by the number of sites where energy can be stored. The more of these ‘redox active sites’ a battery has, the more energy it can hold.
Researchers at the Université Paul Sabatier in France recently produced a hydrogel electrode design with more redox active sites, but the rate of charging was still a limiting factor.
The Drexel-led team got around this by designing more streamlined electrodes with many small openings, making each redox active site more accessible to ions. The researchers liken this to a system of motorways instead of single-lane roads.
"In traditional batteries and supercapacitors, ions have a tortuous path toward charge storage ports, which not only slows down everything, but it also creates a situation where very few ions actually reach their destination at fast charging rates," said Maria Lukatskaya, a lead author on the paper, which was published in the journal Nature Energy.
“The ideal electrode architecture would be something like ions moving to the ports via multi-lane, high-speed 'highways,' instead of taking single-lane roads. Our macroporous electrode design achieves this goal, which allows for rapid charging -- on the order of a few seconds or less."
Gogotsi agrees. “If we start using low-dimensional and electronically conducting materials as battery electrodes, we can make batteries working much, much faster than today,” he said. “Eventually, appreciation of this fact will lead us to car, laptop and cell-phone batteries capable of charging at much higher rates -- seconds or minutes rather than hours.”
Before this can become a real-world energy storage device, the team will need to scale up the production of their material. The team are currently producing 100 grams of the material per batch in the lab, but will need to scale that up to design energy devices incorporating MXenes.
The team are also working to increase the energy density of their material. “We are developing matching anodes to MXene cathodes that will further expand the voltage window—this means doubling the energy density,” said Gogotsi in an interview with IEEE Spectrum.