Northwestern University (NU) researchers have developed a rechargeable lithium-iron-oxide battery that cycles more lithium ions than existing lithium-cobalt-oxide batteries.
The novel battery is the outcome of a collaboration between NU professor Christopher Wolverton’s group and Argonne National Laboratory scientists.
According to the research team, the new battery could enable smart phones and battery-powered automobiles to last much longer.
“Our computational prediction of this battery reaction is very exciting, but without experimental confirmation, there would be a lot of skeptics,” said Wolverton. “The fact that it actually works is remarkable.”
Wolverton and Zhenpeng Yao, a PhD student in Wolverton’s laboratory, led the computational development, while Argonne led the experimental component of the research.
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 from a compound that comprises lithium ions, a transition metal, and oxygen.
The transition metal, which is typically cobalt, effectively stores and releases electrical energy when lithium ions move from the anode to the cathode and back. The capacity of the cathode is then limited by the number of electrons in the transition metal that can participate in the reaction.
“In the conventional case, the transition metal is doing the reaction,” Wolverton said. “Because there is only one lithium ion per one cobalt, that limits of how much charge can be stored. What’s worse is that current batteries in your cell phone or laptop typically only use half of the lithium in the cathode.”
Thanks to computational calculations, Wolverton and Yao have found a way to replace cobalt with iron, which is advantageous because it’s among the cheapest elements on the periodic table.
Moreover, by using this same computation, they discovered the right balance of lithium, iron, and oxygen ions to allow the oxygen and iron to simultaneously drive a reversible reaction without allowing oxygen gas to escape.
“Not only does the battery have an interesting chemistry because we’re getting electrons from both the metal and oxygen, but we’re using iron,” Wolverton said. “That has the potential to make a better battery that is also cheap.”
More importantly, the fully rechargeable battery starts with four lithium ions, instead of one. The current reaction can reversibly exploit one of these lithium ions, significantly increasing the capacity beyond today’s batteries.
Image and content: Zhenpeng Yao/Northwestern University (NU)