Iron oxygen drives more lithium ions.

Christopher Wolverton's Super lithium battery can theoretically work. In a difficult task, the battery uses oxygen to drive chemical reactions. The researchers previously believed that this would cause the battery to become unstable, but the experiment found that not only can the battery work properly, but it also has high performance.

In collaboration with researchers at Argonne National Laboratory, the Wolverton Research Group at Northworth University has developed a rechargeable lithium-iron-oxide battery, which has a lithium ion cycle that is more common than normal lithium-cobalt oxide batteries. It can be made into higher capacity batteries and can keep smart phones and electric cars alive.

"Our predictive calculations of this type of battery reaction are very promising, but there are many sceptics that will appear if there is no experimental process to confirm," said Wolverton, professor of materials science and engineering at the McCormick School of Engineering at Northwest University. "It actually played a very significant role."

Lithium-ion batteries work by shuttling lithium ions back and forth between the anode and the cathode. When the battery is charged, the ions move back to the anode, where they are stored. The cathode is made of lithium ions, transition metals and oxygen compounds. When lithium ions move from the anode to the cathode and return, cobalt can effectively store and release electrical energy, and the cathode capacity is subsequently limited by the number of electrons in the transition metal involved in the reaction.

"Traditionally, transition metals can react," Wolverton said. "Because each cobalt represents only one lithium ion, there is a limit to the amount of storage, and even worse, At present, batteries in mobile phones or laptops usually use only half of the lithium in the cathode. "

Lithium-cobalt oxide batteries have been on the market for 20 years, but researchers are looking for cheaper, higher-capacity alternatives. Wolverton's team used two strategies to improve ordinary lithium-cobalt oxide batteries: replacing cobalt with iron and forcing oxygen to participate in the reaction process.

If oxygen can also store and release electricity, the battery will have a more efficient ability to store and use lithium. Although other research groups have tried this strategy in the past, few people have achieved this. "The problem is that if you try to involve oxygen in the reaction, the compound becomes unstable," Yao said. "Oxygen will be released from the battery and the reaction will be irreversible. "

Through calculations, Wolverton and Yao found a reversible formula. First of all, they use iron instead of cobalt, which is extremely advantageous because it is one of the cheapest elements in the periodic table. Second, by calculation, they found the correct balance of lithium ions, iron ions and oxygen ions so that oxygen and iron ions drive reversible reactions at the same time without letting oxygen escape.

Wolverton said: "Not only does the battery have an interesting chemical reaction, because we get electrons from metal and oxygen, not iron. It is possible that better batteries will also be cheaper. More importantly, fully rechargeable batteries are powered by four lithium-ions, and the current reaction can reversibly use one of these lithium-ions, significantly exceeding the capacity of today's batteries. However, using iron and oxygen to drive the reaction will make all four cycles very promising.

Wolverton said: "Each metal contains four lithium-ions-this will change all lithium batteries. This means that your mobile phone can last eight times longer, or your car can continue to drive eight times. If electric cars can compete with and even surpass gasoline-powered cars in terms of scope and cost, this will change the world energy market.

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