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.