US researchers have developed a new lithium-air battery with a solid electrolyte that has the potential to achieve a record energy density nearly four times that of lithium-ion batteries. The test cell showed stability over 1,000 charge and discharge cycles.
The solid electrolyte consists of a ceramic polymer material made of relatively inexpensive elements in the form of nanoparticles. More specifically, the new composite electrolyte is based on Li10GeP2S12 nanoparticles embedded in a modified polyethylene oxide polymer matrix, enabling chemical reactions that produce lithium oxide (Li2O) in connection with dismantling.
In previous lithium-air models, the lithium in the lithium metal anode moves through the liquid electrolyte and combines with oxygen during the discharge to form lithium peroxide (Li2O2) or superoxide (LiO2) at the cathode. The lithium peroxide or superoxide is then broken down back into the lithium and oxygen components during charging. This chemical sequence stores and releases energy as needed.
“The chemical reaction of lithium superoxide or peroxide involves only one or two electrons stored per oxygen molecule, while the chemical reaction of lithium oxide involves four electrons,” said Argonne chemist Rachid Amine.
In the new model, the reaction of four electrons is enabled by the ion-electron conductive mixed discharge product and its interface with air.
More electrons stored means higher energy density. In theory, a lithium-air battery based on Li2O formation can produce an energy density comparable to that of gasoline. It has the highest projected energy density of any battery technology being considered for next-generation batteries other than lithium-ion.
“With further development, we expect our new lithium-air battery model to also achieve a record energy density of 1,200 watt-hours per kilogram,” said Larry Curtiss, Argonne Distinguished Fellow. “It’s almost four times better than lithium-ion batteries.”
The team’s new design is also the first lithium-air battery to achieve a four-electron reaction at room temperature. In addition, it runs on oxygen from ambient air, eliminating the need for oxygen tanks, which was a problem with earlier structures.
Previous lithium-air test cells have suffered from very short lifespans. But US researchers say this is not the case with their new battery design, as their test cell showed stability over 1,000 charge and discharge cycles.
They discussed their research findings, “Room-Temperature Rechargeable Li2O-based lithium-air battery with solid electrolyte,” published in a recent issue Science.