May 30 2018
New ways to stabilize a new battery with a record-high charge capacity has been discovered by researchers at Northwestern University.
A schematic illustration of the battery's cathode structure in which lithium is red, oxygen is green, manganese is purple, chromium is dark blue and vanadium is light blue. (Credit: Northwestern University)
Based on a lithium-manganese-oxide cathode, the innovation could enable smartphones and battery-powered automobiles to last over twice as long between charges.
This battery electrode has realized one of the highest-ever reported capacities for all transition-metal-oxide-based electrodes. It’s more than double the capacity of materials currently in your cell phone or laptop.
Christopher Wolverton, the Jerome B. Cohen Professor of Materials Science and Engineering, Northwestern’s McCormick School of Engineering
“This sort of high capacity would represent a large advancement to the goal of lithium-ion batteries for electric vehicles.” added Christopher.
The research was reported online May 18th in Science Advances.
Lithium-ion batteries work by ferrying lithium ions back and forth between the cathode and the anode. The cathode is produced from a compound that includes lithium ions, a transition metal, and oxygen. The transition metal, usually cobalt, efficiently stores and discharges electrical energy when lithium ions ferry from the anode to the cathode and back. The cathode’s capacity is then restricted by the number of electrons in the transition metal that can partake in the reaction.
A French research team first identified the large-capacity lithium-manganese-oxide compound in 2016. By substituting the traditional cobalt with less costly manganese, the researchers created a cheaper electrode with twice as much capacity. But it was not without its limitations. The battery’s performance degraded so greatly within the first two cycles that scientists deemed it as not viable for the market. They also did not completely understand the chemical origin of the degradation or the large capacity.
After creating a comprehensive, atom-by-atom picture of the cathode, Wolverton’s team found the reason behind the material’s high capacity: It forces oxygen to partake in the reaction process. By using oxygen — besides the transition metal — to store and discharge electrical energy, the battery has a greater capacity to store and utilize more lithium.
Next, the Northwestern team turned its attention to stabilizing the battery so as to prevent its rapid degradation.
Armed with the knowledge of the charging process, we used high-throughput computations to scan through the periodic table to find new ways to alloy this compound with other elements that could enhance the battery’s performance.
Zhenpeng Yao, the paper’s co-first author and a former Ph.D. student, Wolverton’s laboratory
The computations identified two elements: vanadium and chromium. The team estimates that blending either element with lithium-manganese-oxide will create stable compounds that maintain the cathode’s unparalleled high capacity. Next, Wolverton and his collaborators will experimentally examine these theoretical compounds in the laboratory.
This study was supported as a part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Science under award number DE-AC02-06CH11357. Yao, presently a postdoctoral researcher at Harvard University, and Soo Kim, a postdoctoral researcher at the Massachusetts Institute of Technology, are both former members of Wolverton’s laboratory and served as the paper’s co-first authors.