Drexel researchers developed electrode designs using MXene that allow for much faster charging because they open up paths for ions to quickly travel within the material.
Researchers in Drexel University’s College of Engineering are developing a new battery electrode design that will enable recharging in minutes…or even seconds.
The apparent key to solve the problem of uber-fast charging is to use a highly conductive, two-dimensional material called MXene. The team has demonstrated charging of thin MXene electrodes in tens of milliseconds.
At the same time, MXene will allow the storage of much more energy than conventional supercapacitors, (although the presser is silent about how much more). So for now it’s open question whether MXene has the potential to beat well known lithium–titanate chemistry.
There could be plenty of applications for recharging in minutes (at least at an affordable price), but we are not sure whether we can sacrifice any range in a electric vehicle application to solve the high-power requirement for that kind of charging (5 minutes recharge of 50 kWh pack needs 600 kW of power).
“The key to faster charging energy storage devices is in the electrode design. Electrodes are essential components of batteries, through which energy is stored during charging and from which it is disbursed to power electronic devices. So the ideal design for these components would be one that allows them to be quickly charged and store more energy.
To store more energy, the materials should have places to put it. Electrode materials in batteries offer ports for charge to be stored. In electrochemistry, these ports, called “redox active sites” are the places that hold an electrical charge when each ion is delivered. So if the electrode material has more ports, it can store more energy — which equates to a battery with more “juice.”
Collaborators Patrice Simon, PhD, and Zifeng Lin, from Université Paul Sabatier in France, produced a hydrogel electrode design with more redox active sites, which allows it to store as much charge for its volume as a battery. This measure of capacity, termed “volumetric performance,” is an important metric for judging the utility of any energy storage device.
To make those plentiful hydrogel electrode ports even more attractive to ion traffic, the Drexel-led team, including researchers Maria Lukatskaya, PhD, Sankalp Kota, a graduate student in Drexel’s MAX/MXene Research Group led by Michel Barsoum, PhD, distinguished professor in the College of Engineering; and Mengquiang Zhao, PhD, designed electrode architectures with open macroporosity — many small openings — to make each redox active sites in the MXene material readily accessible to ions.
“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 Lukatskaya, the first author on the paper, who conducted the research as part of the A.J. Drexel Nanomaterials Institute. “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.”
The overarching benefit of using MXene as the material for the electrode design is its conductivity. Materials that allow for rapid flow of an electrical current, like aluminum and copper, are often used in electric cables. MXenes are conductive, just like metals, so not only do ions have a wide-open path to a number of storage ports, but they can also move very quickly to meet electrons there. Mikhael Levi, PhD, and Netanel Shpigel, research collaborators from Bar-Ilan University in Israel, helped the Drexel group maximize the number of the ports accessible to ions in MXene electrodes.
Use in battery electrodes is just the latest in a series of developments with the MXene material that was discovered by researchers in Drexel’s Department of Materials Science and Engineering in 2011. Since then, researchers have been testing them in a variety of applications from energy storage to electromagnetic radiation shielding, and water filtering. This latest development is significant in particular because it addresses one of the primary problems hindering the expansion of the electric vehicle market and that has been lurking on the horizon for mobile devices.
“If we start using low-dimensional and electronically conducting materials as battery electrodes, we can make batteries working much, much faster than today,” Gogotsi 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.””