Lithium-air batteries are attractive because they could have up to five times the energy density of lithium-ion batteries. However, they have inherent shortcomings. In a lithium-air battery, the lithium anode reacts with oxygen from the air, with energy stored in the chemical bonds of oxide compounds. However, one of the products is lithium peroxide, an insoluble substance that clogs the battery’s electrode.
Looking to address the problem, battery scientists at Argonne National Laboratory have developed a prototype that, they claim, only produces lithium’s superoxide as the battery discharges, not the peroxide. Lithium superoxide breaks down easily into lithium and oxygen, holding the prospect of a battery with high efficiency and good cycle life.
While the Argonne group designed the battery to consume one electron, rather than two, and hence to produce the superoxide, UIC researcher Amin Salehi-Khojin said it was difficult to prove the reaction had taken place.
Using mass spectroscopy to follow the reaction in situ, the Illinois researchers showed that one electron was produced per oxygen atom, indicating lithium superoxide was forming in the battery. They also showed that no other lithium compounds were generated as by products.
Salehi-Khojin said: “Not only can we analyse the products of the electrochemical reaction, we can also elucidate the reaction pathway. If we know the reaction pathway, we’ll know how to design the next generation of that battery for energy efficiency and cost effectiveness.”
