Doubling the capacity of iron oxide-type cathodes for cost-effective Li-ion batteries

A research group has demonstrated a high-energy lithium-ion (Li-ion) cathode, potentially paving the way for cost-effective, safe and high-capacity Li-ion batteries.

Li-ion batteries are ubiquitous in electronics and electric vehicles, and will play a prominent role in charging a sustainable future. But Li-ion batteries rely on transition metals such as cobalt and nickel. And supplies of these expensive materials are limited to a handful of countries. Developing transition metals from earth-abundant elements is therefore a critical task for scientists.

Olivine-type lithium-iron phosphates (LiFePO₄) have shown promise in recent years as a cost-effective alternative. But their storage capacity is limited since the material relies on iron’s single electron transfer, i.e., iron redox.

Because of this, the group explored the antifluorite-type lithium-iron oxide (Li₅FeO₄). First reported on in 1999, Li₅FeO₄, has a theoretical capacity twice that of LiFePO₄ because it involves an oxygen redox and an iron redox. But utilizing both the iron and oxygen redox is difficult to achieve.

To overcome this, the group employed a mechanochemical alloying approach to bring Li₅FeO₄ to a metastable phase. The fabricated metastable Li₅FeO₄ exhibited iron and oxygen redox, and demonstrated double the capacity of LiFePO₄.

“Our approach turned the theoretical into reality, and sets us on a path to developing high-energy cathode materials,” says Dr. Hiroaki Kobayashi, lead author of the paper and professor at Tohoku University’s Institute of Multidisciplinary Research for Advanced Materials. “This will lead to cost-effective, high-capacity Li-ion batteries based on abundant materials.”

The research was conducted as a joint-research project between Tohoku University and the Nagoya Institute of Technology. Details were published in the journal Advanced Energy Materials on January 15, 2023.