This schematic shows a lithium-air battery cell consisting of a lithium metal anode, an air-based cathode and a solid ceramic polymer electrolyte (CPE). On discharge and charge, lithium ions (Li+) travel from the anode to the cathode, then back. Image: Argonne National Laboratory.
This schematic shows a lithium-air battery cell consisting of a lithium metal anode, an air-based cathode and a solid ceramic polymer electrolyte (CPE). On discharge and charge, lithium ions (Li+) travel from the anode to the cathode, then back. Image: Argonne National Laboratory.

Many owners of electric cars have wished for a battery pack that could power their vehicle for more than a thousand miles on a single charge. Researchers at the Illinois Institute of Technology (IIT) and the US Department of Energy (DOE)’s Argonne National Laboratory have now developed a lithium-air battery that could make that dream a reality. The team’s new battery design could also one day power domestic airplanes and long-haul trucks.

The main new component in this lithium-air battery is a solid electrolyte instead of the usual liquid variety. Batteries with solid electrolytes are not subject to the safety issue that bedevils the liquid electrolytes used in lithium-ion and other battery types, which can overheat and catch fire.

More importantly, compared with conventional lithium-ion batteries, the team’s battery chemistry with the solid electrolyte can potentially boost energy density by as much as four times, which translates into a longer driving range. The researchers report their work in a paper in Science.

“For over a decade, scientists at Argonne and elsewhere have been working overtime to develop a lithium battery that makes use of the oxygen in air,” said Larry Curtiss, a distinguished fellow at Argonne. “The lithium-air battery has the highest projected energy density of any battery technology being considered for the next generation of batteries beyond lithium-ion.”

In past lithium-air designs, lithium ions from a lithium metal anode move through a liquid electrolyte to combine with oxygen during battery discharge, yielding lithium peroxide (Li2O2) or lithium superoxide (LiO2) at the cathode. During charging, the lithium peroxide or superoxide is broken back down into its lithium and oxygen components. This chemical sequence stores and releases energy on demand.

The team’s new solid electrolyte is composed of a ceramic polymer material made from relatively inexpensive elements in nanoparticle form. This new solid facilitates chemical reactions that produce lithium oxide (Li2O) on discharge, rather than lithium peroxide or superoxide.

“The chemical reaction for lithium superoxide or peroxide only involves one or two electrons stored per oxygen molecule, whereas that for lithium oxide involves four electrons,” said Argonne chemist Rachid Amine. More electrons stored means a higher energy density.

The team’s novel lithium-air battery is the first to achieve a four-electron reaction at room temperature. It also operates with oxygen supplied by air from the surrounding environment. The capability to utilize the oxygen in air avoids the need for oxygen tanks, a problem with earlier designs.

The team employed many different techniques to establish that a four-electron reaction was actually taking place. One key technique was transmission electron microscopy (TEM), which they used to study the discharge products on the cathode surface. This was carried out at Argonne’s Center for Nanoscale Materials, a DOE Office of Science user facility. The TEM images provided valuable insight into the four-electron discharge mechanism.

Past lithium-air test cells suffered from very short cycle lives. The team established that this shortcoming is not the case for their new battery design, by building and operating a test cell for 1000 cycles, demonstrating its stability over repeated charging and discharging.

“With further development, we expect our new design for the lithium-air battery to also reach a record energy density of 1200 watt-hours per kilogram,” said Curtiss. “That is nearly four times better than lithium-ion batteries.”

This story is adapted from material from Argonne National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.