The Pacific Northwest National Laboratory in Richland, Washington, seems to have an industrious group of researchers who come up with ever-improved forms of batteries. One of their creations, a hybrid graphite/lithium anode, was featured in this blog last year. Now, Frances White reports from the PNNL that one of the researchers involved with that work has led another team to an innovative approach to a new electrolyte for lithium batteries. According to Ms. White, “PNNL physicist Jason Zhang (Ji-Guang “Jason” Zhang) and his colleagues have developed a new electrolyte that allows lithium-sulfur, lithium-metal and lithium-air batteries to operate at 99 percent efficiency, while having a high current density and without growing dendrites that short-circuit rechargeable batteries.” This is a real breakthrough because, for lithium batteries overall, the chemistries that give higher performance are generally more volatile. This new material avoids those issues and gives top performance with great safety. Earlier electrolytes reacted with the lithium electrode to grow little spikes that …
Bulletproof Batteries?
Researchers announce that a “New battery technology from the University of Michigan should be able to prevent the kind of fires that grounded Boeing 787 Dreamliners in 2013.” The use of the word “should” is instructive, since scientist usually couch such announcements in more guarded terms. Battery separator materials are usually not the glamorous part of cell development, most headlines given to electrode and electrolyte breakthroughs. Kevlar may be a way, within batteries, of preventing a breakthrough. Nanofibers extracted from Kevlar, that impenetrable material in bullet-proof vests, “stifles the growth of metal tendrils that can become unwanted pathways for electrical current,” according to a University of Michigan report. Separator material stands between layers of other battery materials and ideally allows the passage of ions between electrodes in the battery. As the researchers report, “The innovation is an advanced barrier between the electrodes in a lithium-ion battery.” The nanofiber material has openings large enough to allow transfer of ions between anode …
Suppressing Those Pesky Dendrites
Dendrites in the human body are tree-branch-like protuberances that help transmit synapses, defined as tiny transmitters and receivers for chemical messages between the cells. In this setting they are beneficial and necessary for brain and nervous system development. In batteries, however, such protuberances send mixed and negative messages that short out connections between the components of the host battery. This is a serious enough issue that it’s kept lithium-metal batteries from serious development, dendrites growing between dissimilar metals being a malady of such cells, and even causing fires that make lithium batteries a bit fearsome. The blog has reported on efforts by Berkeley Lab researchers to reduce dendrite growth. To enable visualization of these growths, Clare Grey, a professor of chemistry at Cambridge University, teamed up with NYU chemist Alexej Jerschow to develop a way of imaging batteries through magnetic resonance imaging (MRI). As Popular Mechanics explained in 2012, “These moss-like crystalline growths, called dendrites, are the bane of battery builders. …
Dendrites Grow Like Kudzu
Getting your fiber is a good idea for digestion and general health, but what if those fibers get you first? Or at least destroy your battery? This is the situation as described by a report from the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), in which the writer tells us that dendrites are hairy little lithium fibers that “sprout from the surface of the lithium electrode and spread like kudzu across the electrolyte until they reach the other electrode.” These 3D reconstructions show how dendritic structures that can short-circuit a battery form deep within a lithium electrode, break through the surface and spread across the electrolyte. Besides resembling a fast-growing invasive plant, the dendrite bridge across the electrodes can cause an internal short circuit and possible fires in the battery, making dendrites extremely unwanted intruders. Because they pop up from the surface of electrodes, dendrites might easily have been understood as a surface phenomenom. Nitash Balsara, …