NEW YORK – A new nanomaterial developed by a team of researchers at Rensselaer Polytechnic Institute, located in the city of Troy, 150 miles (241 km) north of New York City, could lead to a new breed of lithium-ion batteries that recharge 40 times faster than current power packs for electric vehicles.
RPI researchers call the new material “nanoscoop.” Its shape looks like a cone with a scoop of ice cream on top. Nanoscoops enable Li-ion batteries to accommodate high rates of charge and discharge that would cause conventional electrodes to quickly fail.
Nikhil Koratkar, an RPI professor, says the nanoscoop electrode can be charged and discharged 40-60 times faster than conventional battery anodes and still maintain comparable energy density. The RPI team has achieved this through more than 100 continuous charge/discharge cycles.
“This technology could potentially be ramped up to suit the demanding needs of batteries for electric automobiles,” Koratkar says.
Current EVs use supercapacitors for power-intensive modes, including starting and accelerating vehicles, while the battery pack provides power for cruising, and Koratkar says nanoscoops may allow combining the separate systems into a single battery pack.
The researchers say charging and discharging have the opposite effect on battery anodes, causing a buildup of stress and premature failure of batteries. The nanoscoop was engineered to withstand this type of stress buildup.
It has a carbon nanorod base topped with a thin layer of nanoscale aluminum and a scoop of nanoscale silicon. This segmented structure transfers the strain from the carbon base to the aluminum layer and finally to the silicon scoop.
The strain gradation also creates a less abrupt transition in stress across the interfaces and improves structural integrity of the electrode. Additionally, the nanoscale size of the scoop makes the structure less susceptible to cracking than bulk materials.
“Due to their nanoscale size, our nanoscoops can soak and release lithium at high rates far more effectively than the macroscale anodes used in today's Li-ion batteries,” Koratkar says.
“This means our nanoscoop may be the solution to a critical problem facing auto companies and other battery manufacturers: How do you increase power density of a battery while still keeping the energy density high?”
Koratkar admits nanoscoop architecture is limited at present by the relatively low total mass of the electrode. His team will attempt to solve this by growing longer scoops with greater mass or develop a way of stacking nanoscoops on top of each other.
Toh-Ming Lu, an RPI professor, and Rahul Krishnan, a graduate student at the institute, collaborated in the research, which was funded by the National Science Foundation and the New York State Energy Research and Development Authority.