A soft solution to the hard problem of energy storage
It’s great in the lab, but will it actually work? That’s the million-dollar question perpetually leveled at engineering researchers. For a family of layered nanomaterials, developed and studied at Drexel University—and heralded as the future of energy storage—that answer is now, yes.
For some time, researchers have been working on using two-dimensional materials, atomically thin nanomaterials, as components for faster-charging, longer-lasting batteries and supercapacitors. But the problem with the existing techniques for doing so are that when the thickness of the material layer is increased to about 100 microns—roughly the width of a human hair, which is the industry standard for energy storage devices—the materials lose their functionality.
Recently published research from Drexel and the University of Pennsylvania, shows a new technique for manipulating two-dimensional materials that allows them to be shaped into films of a practically usable thickness, while maintaining the properties that make them exceptional candidates for use in supercapacitor electrodes.
The study, published in the journal Nature, focuses on using soft materials—similar to those in the liquid crystal displays of phones and televisions—as a guide for self-assembly of MXene sheets. MXenes, are a class of nanomaterials discovered at Drexel in 2011, that are particularly well-suited for energy storage.
“Our method relies on a marriage between soft material assembly and functional 2-D nanomaterials,” said Yury Gogotsi, Ph.D., Distinguished University and Bach professor in Drexel’s College of Engineering, who was a co-author of the research. “The resulting electrode films show rapid ion transport, outstanding rate handling, and charge storage equal to or exceeding commercial carbon electrodes.”
An Open Channel
According to co-author Yu Xia, Ph.D., a postdoctoral fellow in Penn’s School of Engineering and Applied Science, the challenge of maintaining the energy density (how much energy the devices can store) and power density (how fast the device can charge) of a charge storing material lies in maintaining clear channels for ion movement as the materials are scaled up to larger sizes.
“The ion diffusion problem in energy storage devices,” Xia says, “including batteries and supercapacitors, has been long recognized as one of the major issues impeding the industrial development of new batteries and supercapacitors with higher energy and power density. Conventionally, 2-D materials intend to stack on top of each other like sheets of paper in a book, resulting in a prolonged ion diffusion length, which suppresses their performance when the thickness of the electrode approaches industrial standards.”
