Progress to Lithium Air Battery With 4X Energy Density of Lithium Batteries

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. The Argonne Lab team’s lithium-air design is the first lithium-air battery that has achieved a four-electron reaction at room temperature. It also operates with oxygen supplied by air from the surrounding environment. The capability to run with air avoids the need for oxygen tanks to operate, a problem with earlier designs.

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 charge and discharge.

“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.”

Science – A room temperature rechargeable Li2O-based lithium-air battery enabled by a solid electrolyte.

An enabling composite electrolyte
Lithium-air batteries have scope to compete with gasoline in terms of energy density. However, in most systems, the reaction pathways either involve one- or two-electron transfer, leading to lithium peroxide (Li2O2) or lithium superoxide (LiO2), respectively. Kondori et al. investigated a lithium-air battery that uses a ceramic-polyethylene oxide–based composite solid electrolyte and found that it can undergo a four-electron redox reaction through lithium oxide (Li2O) formation and decomposition (see the Perspective by Dong and Lu). The composite electrolyte embedded with Li10GeP2S12 nanoparticles shows high ionic conductivity and stability and high cycle stability through a four-electron transfer process. —MSL

Abstract
A lithium-air battery based on lithium oxide (Li2O) formation can theoretically deliver an energy density that is comparable to that of gasoline. Lithium oxide formation involves a four-electron reaction that is more difficult to achieve than the one- and two-electron reaction processes that result in lithium superoxide (LiO2) and lithium peroxide (Li2O2), respectively. By using a composite polymer electrolyte based on Li10GeP2S12 nanoparticles embedded in a modified polyethylene oxide polymer matrix, we found that Li2O is the main product in a room temperature solid-state lithium-air battery. The battery is rechargeable for 1000 cycles with a low polarization gap and can operate at high rates. The four-electron reaction is enabled by a mixed ion–electron-conducting discharge product and its interface with air.