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Novel graphene electrode improves already promising lithium-air battery technology

(Nanowerk Spotlight) Lithium-ion batteries have been widely used in many electronic devices that are important to our daily life. However, after a steady improvement of some 10-15% during the last two decades, the energy density of lithium-ion batteries is now approaching its theoretical limit set by the energies of cathode and anode materials used in these batteries. Therefore, in recent years, the pursuit of the next generation of energy storage systems has been intense globally.

One such system is metal/air batteries, which have much higher specific energies than most currently available primary and rechargeable batteries.

“Metal/air batteries are unique in that the cathode active material is not stored in the battery” Dr. Ji-Guang Zhang, a researcher at Pacific Northwest National Laboratory’s Transformational Materials Science Initiative, explains to Nanowerk. “Instead, oxygen from the environment is reduced by catalytic surfaces inside the air electrode, forming either an oxide or peroxide ion that further reacts with cationic species in the electrolyte. The Li/O2 couple is especially attractive because it has the potential for the highest specific energy among all the known electrochemical couples.”

Among various electrochemical energy storage systems explored to date, the lithium-air (Li-air) battery is one of the most promising technologies, with a theoretical energy density nearly ten times that of conventional lithium-ion batteries. This is because lithium metal as an anode has a capacity ten times higher than that of conventional graphite anodes, and oxygen as the cathode of a Li-air battery can be absorbed freely from the environment leading to a significant reduction in the weight and the cost of the battery.

For use in practical devices such as electric cars, researchers expect that Li-air batteries achieve an energy density of about 800 Wh/kg – which is three times as large as those of the state of the art Li-ion batteries. Therefore, Li-air batteries have a good potential to be used in many applications which requires an energy storage system beyond those of Li-ion batteries, such as long range electrical vehicles which can run more than 500 kilometers per charge.
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