Lithium-iron oxide battery is available to extend battery life

Wolverton's team worked with researchers at Argonne National Laboratories to develop a rechargeable lithium-iron oxide battery that circulates more lithium ions than conventional lithium cobalt oxide batteries.

The result is a larger capacity battery that will keep battery-powered electric cars and smart phones working longer.

Wolverton, a professor of materials science and engineering at Northwestern University's McCormick School of Engineering, said: "We are very excited about the calculation of the battery, but if there is no experiment confirmed, there will be many skeptics who doubt its scientific nature. In fact, his role is very significant.

The research, supported by the US Department of Energy's Energy Frontier Research Center program, was recently published in Nature Energy. The Phut students in the Wolverton lab, ZhenpengYao and Argonne's postdoctoral ChunZhan, were the first authors of the paper. Argonne led the experimental part of the study, and Wolfton and Yao Ming were responsible for computational development.

Lithium-ion batteries work by shuttle lithium ions back and forth between the anode and the cathode. When the battery is charged, ions move to the anode. The cathode is formed from a compound consisting of a transition metal, lithium ions, and oxygen. The transition metal is typically cobalt, which effectively stores and releases electrical energy as it passes from the anode to the cathode and then back. The capacity of the cathode is then limited by the amount of electrons in the transition metal.

Lithium-cobalt oxide batteries have been commercially available for 20 years, but researchers have long been looking for larger, cheaper alternatives. Wolverton's team used two strategies to enhance the ordinary lithium cobalt oxide battery: using iron instead of cobalt to force oxygen into the reaction process.

If oxygen also store and release electrical energy, the battery will have a larger capacity to store and then use more and more lithium. Although other research teams have tried this method in the past, only a few have succeeded.

“The problem was that if you tried to get oxygen into the reaction, the compound would become unstable,” Yao said. "Oxygen will be released from the battery, making the reaction irreversible.

Wolverton and Yao found a formula that made the work reversible. They first replaced iron with iron, which is beneficial because it is one of the cheapest elements on the periodic table. Through calculations, they discovered the correct balance of lithium, iron and oxygen ions, so that iron and oxygen simultaneously drive the reversible reaction and prevent the escape of oxygen.

Wolverton said, "Because we get electrons from metals and oxygen, and the metal we use is iron, our batteries not only have interesting chemical composition, but also make it possible to make cheaper batteries."

Another important aspect is that a fully charged battery does not start with one lithium ion but starts with four lithium ions. The current reaction is to be able to reversibly utilize one of the lithium ions, mainly to increase the capacity of existing batteries. However, the possibility of driving the entire reaction by using oxygen and iron is indeed attractive.

“Every metal has four lithium ions, which will change everything,” Wolverton said. “This means that your phone can be extended by 8 times, or your car can be opened 8 times. If the electric car can compete with gasoline-powered cars in terms of mileage and cost, then this will change the world.”

Wolverton has filed a temporary patent for batteries with Northwestern University's Office of Innovation and Venture Capital. Looking ahead, Wolfton and his team plan to discover other compounds to prove that this strategy works.

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