University of Surrey researchers have developed iron- and molybdenum-based catalysts for lithium-CO₂ batteries. In lab tests, the best material, made by heating to 500°C, achieved almost four times a reference material’s discharge capacity, recovered 93% of charge and completed 92 cycles without precious metals. Published in the Journal of Power Sources.
Researchers at the University of Surrey have developed iron-based catalysts for lithium-carbon dioxide (Li-CO₂) batteries that performed as well as, or better than, previously reported precious-metal catalysts in laboratory tests.
The team at the [Guildford, UK-based] university says the catalysts, which use iron and molybdenum, could reduce the technology’s reliance on scarce and expensive metals such as platinum, ruthenium and iridium. The research is published in the Journal of Power Sources.
In lab testing, the best-performing material delivered almost four times the discharge capacity of an unmodified reference material. It recovered 93% of the electrical charge during recharging and completed 92 charge-discharge cycles under conditions in which the charge released in each cycle was deliberately limited.
Li-CO₂ batteries are being investigated as an alternative to lithium-ion technology because they could store more energy for a given weight. The chemistry is still at an early stage, with charging efficiency, reliability and service life yet to be resolved. Developing catalysts to support the charge and discharge reactions is one of the obstacles.
According to Dr. Siddharth Gadkari, senior lecturer in chemical engineering at the University of Surrey and a corresponding author of the paper, the work addresses one of those barriers. “Lithium-CO₂ batteries have the potential to store substantially more energy than today’s lithium-ion batteries, which could eventually mean longer-lasting electronic devices and electric vehicles that travel further without increasing battery weight,” he says. “Our research tackles one of the key barriers preventing these batteries from reaching that potential. We’ve shown that strong battery performance is possible without relying on expensive precious metals, opening up a promising route towards a new generation of more affordable and sustainable batteries.”
To make the catalysts, the team added iron to a molybdenum-based compound and heated the material at a range of temperatures to study how changes in its structure affected performance. Heating to 500°C (932°F) gave the best results, producing a combination of molybdenum oxide and iron phosphate that the researchers say helped the charge and discharge reactions.
“We found that even relatively simple changes to how these materials are prepared can make a big difference to how well they perform,” says lead author Dr. Mahsa Masoudi, a research fellow at the university’s School of Engineering. “The temperature we used changed the structure of the catalyst, and that had a significant impact on how efficiently the battery could charge and discharge. Understanding why those changes matter gives us a valuable starting point for improving these batteries further.”
The researchers say further work is needed to determine whether the materials can maintain their performance over longer periods and under more demanding operating conditions.
“There’s still a long way to go before we see lithium-CO₂ batteries in everyday devices, but these results are an encouraging step forward,” says Dr. Daniel Commanduer, a lecturer at the university and a corresponding author. “We’ve shown what these materials can achieve in the lab, and the next challenge is making sure they can deliver that performance consistently over much longer periods.”
The team plans to work on improving catalyst performance and durability, and to examine whether the materials could be used in other technologies that convert carbon dioxide.
