Electrode could enable electric cars that charge in minutes
Black phosphorus anode enables long-lasting, fast charging batteries
by Prachi Patel
This article was originally published by Chemical & Engineering News
Every year, electric vehicles’ driving range grows. But the hours it takes to recharge their batteries slows them down. Researchers now report a battery electrode based on 2D black phosphorus that they say could be used to make batteries that could power a car for 600 miles, and charge in under 10 minutes (Science 2020, DOI: 10.1126/science.aav5842).
Today’s electric vehicle batteries have a graphite anode and a lithium metal oxide cathode. These materials need to be good at three things: holding a lot of lithium ions, moving them around quickly, and maintaining stability over the battery’s lifetime. A battery that maximizes all three metrics is the highest goal of battery research, says Hengxing Ji, a chemist at the University of Science and Technology of China. But improving one usually comes at the expense of the others.
Prioritizing the need to extend electric vehicles’ driving range, researchers have spent years improving battery cathodes. Only recently has focus shifted to the anode, and to charging speeds. Lithium ions move sluggishly through graphite, slowing down charging, and the material also can’t hold much lithium, which limits how much energy it can store, a metric called energy density.
Ji, Xiangfeng Duan at the University of California Los Angeles, and their colleagues are focusing on a new anode contender: black phosphorus. The highly conductive material shares some of the advantages and drawbacks of another emerging anode material, silicon. Its energy density is quite high, but as with silicon, this can be a liability. Both materials swell drastically as they take up large amounts of lithium ions during charging—eventually they deteriorate under the stress. Various black phosphorus-based anodes made so far have yet to meet the material’s potential, Ji says.
He and his colleagues—including Nobel Prize–winning battery chemist John B. Goodenough—made their anodes with composite particles of black phosphorus and graphite coated with a thin polyaniline gel. Black phosphorus particles are made of layered nanoflakes, the edges of which tend to deform, hindering the movement of lithium ions. But the new material has a stronger structure because of covalent bonds between phosphorus and carbon atoms, which eases ion transport. The polyaniline soaked up the electrolyte and formed a thin, stable protective layer at the anode. This layer conducted lithium ions but prevented the formation and build-up of less conductive inorganics such as lithium. It also suppressed the anode’s volume changes.
Understanding the resistance of NRAS-mutated melanomas: Lo is investigating ways to block multiple resistance routes in melanomas with the NRAS gene mutation and to combine and sequence targeted therapies and immunotherapies. By characterizing and co-targeting genomic, epigenomic, proteomic and immunologic alterations that resist therapies, the team will be able to reveal the landscape of resistance.
- Targeting ferroptosis to block the de-differentiation resistance escape route: One way cancers escape targeted treatments is to de-differentiate, or change the type of cell they are into an earlier stage of development. This change of identity allows the cells to be less dependent on the pathway that was otherwise being effectively targeted. Graeber is investigating cell subtypes that de-differentiate and have shown sensitivity to a type of self-inflicted cell death called ferroptosis, which can potentially block melanoma cells attempting to take this escape route. Using ferroptosis-inducing drugs in combination with current standard treatments could potentially strengthen the response rate.
- Studying resistance mechanisms in PD-1 blockade immunotherapy: This project, led by Ribas, is looking at how interferon-gamma, an immune response–stimulating signaling molecule that helps activate immune cells, guides the treatment response in people with advanced melanoma who are treated with one of the leading immunotherapies, called PD-1 blockade. Understanding how interferon-gamma genes work can potentially be used to predict a response to immunotherapy and for rationalizing new combination treatments that induce interferon signaling that can be used to treat more patients.
“All of our research addresses problems that require integrated and collaborative work with one another,” Lo said. “Sharing resources has been instrumental in moving our work forward, and this grant will help us move faster in the lab, enabling us to create therapies for more people who desperately need it.”
Ribas, Lo and Graeber are all members of the UCLA Jonsson Comprehensive Cancer Center and the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.
When paired with a conventional cathode and tested in a battery, the anode showed a charge capacity of 500 mAh/g at a high current density of 13 A/g, and kept 90% of this capacity after 2000 charge cycles. With the right cathode materials and careful engineering, this could lead to a lithium-ion battery that charges in minutes and has an energy density that is 50% higher than today’s best batteries, enabling a driving range of 600 miles between charges.
The new anode has an impressive combination of properties, says Yury Gogotsi, a materials scientist and engineer at Drexel University. The challenge now is to make the material practical. “Black phosphorus is more difficult to manufacture compared to graphite or silicon,” he says. Making practical battery cells will also require developing matching high current density cathodes, which could be difficult. Nonetheless, “this is smart engineering,” Gogotsi says. “This shows that there may be an alternative to silicon-based anodes.”