Lithium-air breakthrough promises new class of batteries
Lithium-air batteries promise greater energy density than lithium-ion batteries, but research on lithium-air batteries has so far demonstrated drawbacks that have stalled their introduction. One such drawback is the formation of lithium peroxide ((LiO2), a solid precipitate that clogs the pores of the lithium-air battery electrode.
Now, Argonne battery scientists Jun Lu, Larry Curtiss, and Khalil Amine, along with American and Korean collaborators, have been able to produce stable crystallized lithium superoxide – instead of lithium peroxide – during battery discharging. Unlike lithium peroxide, lithium superoxide can easily dissociate into lithium and oxygen, leading to high efficiency and good cycle life.
"This discovery really opens a pathway for the potential development of a new kind of battery," says Curtiss. "Although a lot more research is needed, the cycle life of the battery is what we were looking for."
The major advantage of a battery based on lithium superoxide is that it allows, at least in theory, for the creation of a lithium-air battery that consists of what chemists call a ‘closed system.’ Open systems require the consistent intake of extra oxygen from the environment, while closed systems do not – making them safer and more efficient.
The lattice match between LiO2 and Ir3Li may be responsible for the LiO2 discharge product found for the Ir-rGO cathode material. Credit: Argonne/Larry Curtiss
"The stabilization of the superoxide phase could lead to developing a new closed battery system based on lithium superoxide, which has the potential of offering truly five times the energy density of lithium ion," says Amine.
Curtiss and Lu attributed the growth of the lithium superoxide to the spacing of iridium atoms in the electrode used in the experiment. "It looks like iridium will serve as a good template for the growth of superoxide," Curtiss says.
"However, this is just an intermediate step," says Lu. "We have to learn how to design catalysts to understand exactly what’s involved in lithium-air batteries."
For more, see the paper in the journal Nature: "A lithium–oxygen battery based on lithium superoxide."
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