Fuel cells and batteries provide electricity by generating and coaxing positively charged ions from a positive to a negative terminal which frees negatively charged electrons to power cellphones, cars, satellites, or whatever else they are connected to. A critical part of these devices is the barrier between these terminals, which must be separated for electricity to flow.
Improvements to that barrier, known as an electrolyte, are needed to make energy storage devices thinner, more efficient, safer, and faster to recharge. Commonly used liquid electrolytes are bulky and prone to shorts, and can present a fire or explosion risk if they’re punctured.
Research led by University of Pennsylvania engineers suggests a different way forward: a new and versatile kind of solid polymer electrolyte (SPE) that has twice the proton conductivity of the current state-of-the-art material. Such SPEs are currently found in proton-exchange membrane fuel cells, but the researchers’ new design could also be adapted to work for the lithium-ion or sodium-ion batteries found in consumer electronics.
The study, published in Nature Materials, was led by Karen I. Winey, TowerBrook Foundation Faculty Fellow, professor and chair of the Department of Materials Science and Engineering, and Edward B. Trigg, then a doctoral student in her lab. Demi E. Moed, an undergraduate member of the Winey lab, was a coauthor.
They collaborated with Kenneth B. Wagener, Georg
e B. Butler Professor of Polymer Chemistry at the University of Florida, Gainesville, and Taylor W. Gaines, a graduate student in his group. Mark J. Stevens, of Sandia National Laboratories, also contributed to this study, as well as Manuel Maréchal and Patrice Rannou, of the French National Center for Scientific Research, the French Alternative Energies and Atomic Energy Commission, and the Université Grenoble Alpes.
A variety of SPEs already exists. Nafion, which is widely used in proton-exchange membrane fuel cells, is a sheet of flexible plastic that is permeable to protons and impermeable to electrons. After absorbing water, protons can flow through microscopic channels that span the film.
A thin, SPE like Nafion is especially enticing for fuel cells in aerospace applications, where every kilogram counts. Much of the bulk of portable batteries comes from shielding designed to protect liquid electrolytes from punctures. Systems using liquid electrolytes must separate the electr
odes further apart then their solid electrolyte counterparts, as metal build-up on the electrodes can eventually cross the channel and cause a short.