Ulrich Wiesner, the Spencer T. Olin Professor of Engineering, led the group, which included researchers in engineering, chemistry and physics.
The group’s findings are detailed in a paper published in Science Advances, Jan. 29.
But these batteries are not in common use today because, when recharged, they spontaneously grow treelike bumps called dendrites on the surface of the negative electrode.
Over many hours of operation, these dendrites grow to span the space between the negative and positive electrode, causing short-circuiting and a potential safety hazard.
The technology – based on a covalent organic framework (COF) infused with an electronically conducting polymer thin film – could benefit numerous technologies including automotive, by speeding up the charging process, extending single-charge range and even incorporating the device into the body of the car itself.
Visiting scientists from the University of Virginia have used the facilities of the Cornell High Energy Synchrotron Source (CHESS) to observe their chemistry in action. By firing high-intensity X-rays into a sample in a process known as X-ray crystallography, CHESS scientists took a series of snapshots of a material as it crystallized, showing how changes in the formula affect the process of crystal growth.
Among those systems, lithium sulfur batteries are one of the most attractive candidates, because elemental sulfur has a high theoretical capacity of 1,672 mAh g-1, is abundant, inexpensive and environmentally benign. However, there are several challenges hindering the practical deployment of Li-S batteries.
Quinones, in general, and anthraquinones, in particular, are especially attractive due to their ability to reversibly exchange multiple electrons per formula unit. When used as the active electrode material in a real lithium-ion battery (LIB), crystalline anthraquinone (in powder form) reversibly changes crystal packing as a function of state-of-charge (redox state), with a well-defined voltage plateau appearing concomitantly with new structural phases.
Their potential application is, however, currently limited as HOIPs shows structural instability under high temperature, humidity, or even extended light exposure. Understanding of the perovskite structural stability and phase transitions is deemed both timely and essential.
Transition-metal oxides are a class of high-performance catalysts with great potential, but the way in which they govern electrochemical reactions that turn fuel into energy remains poorly understood. Jin Suntivich, assistant professor of materials science and engineering, hopes to change that by studying catalysts in a new way, and he has been awarded $750,000 by the U.S. Department of Energy’s 2017 Early Career Research Program.
Batteries store energy via chemical reactions for later use in electronics, transportation, and grid load leveling. Most commercial rechargeable batteries are based on mechanisms fairly well understood. To move forward in the development of better energy materials, new materials need to be developed to increase efficiency and lifetime of batteries. Tracking the structural changes, as a function of battery cycling, reveals the molecular mechanism used by the material for charge storage.
Joress is a PhD candidate in the Cornell Materials Science Department, and has been very active at CHESS since his arrival in the fall of 2012. His particular interest has been the study of fast processes in real time, especially chemical reactions and phase transitions in thin films, and he has co-authored over a dozen publications in this area.