Researchers at the University of Surrey have developed iron-based catalysts that could help make rechargeable lithium-CO₂ batteries cheaper and more sustainable by reducing reliance on precious metals. In a study published in the Journal of Power Sources, the team reported that catalysts made using iron and molybdenum performed comparably to, and in some measures better than, previously reported catalysts containing expensive precious metals.
Why lithium-CO₂ batteries need new catalysts
Lithium-CO₂ batteries, which use carbon dioxide, are being explored as an alternative to today’s lithium-ion batteries because, in theory, they could store substantially more energy for the same weight. The technology remains at an early stage of development, however. Commercial lithium-ion batteries currently outperform it in areas such as reliability and lifespan.
A central challenge is finding catalysts, materials that speed up chemical reactions, that allow the batteries to charge and discharge efficiently. Many of the most effective options rely on scarce and expensive metals such as platinum, ruthenium and iridium. This raises concerns about their cost and suitability for large-scale production.
Climate Global News has previously reported on University of Surrey research into lithium–CO₂ ‘breathing’ batteries.
Laboratory results for the iron-based catalysts
In tests, the team’s best-performing catalyst delivered nearly four times the discharge capacity of an unmodified reference material, meaning it could release substantially more electrical charge. It also recovered 93 per cent of the electrical charge during recharging.
The catalyst completed 92 charge-discharge cycles in the laboratory. During these tests, the amount of charge released in each cycle was deliberately limited.
Dr Siddharth Gadkari, Senior Lecturer in Chemical Engineering at the University of Surrey and corresponding author of the study, said: “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.
“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.”
How heat treatment changed performance
To develop the catalysts, the team introduced iron into a molybdenum-based compound. They then heated it to different temperatures to see how changes in its structure affected battery performance.
Heating the material to 500°C produced the best results. This created a combination of molybdenum oxide and iron phosphate that helped the chemical reactions involved in charging and discharging take place more efficiently.
Dr Mahsa Masoudi, Research Fellow at the University of Surrey’s School of Engineering and lead author of the study, said: “We found that even relatively simple changes to how these materials are prepared can make a big difference to how well they perform. 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.”
Durability remains the next challenge
The researchers stressed that commercial use is still some way off. Dr Daniel Commanduer, a Lecturer at the University of Surrey and corresponding author of the study, said: “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. 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 now hopes to build on the findings by improving the performance and durability of the iron-based catalysts. It also plans to explore whether they could be used in other technologies that convert carbon dioxide. The full paper in the Journal of Power Sources is available online.
Frequently asked questions
What are lithium-CO₂ batteries?
Lithium-CO₂ batteries are rechargeable batteries that use carbon dioxide. They are being explored as an alternative to lithium-ion batteries because, in theory, they could store substantially more energy for the same weight.
Why do lithium-CO₂ batteries need new catalysts?
Many of the most effective catalysts for these batteries rely on expensive and scarce precious metals such as platinum, ruthenium and iridium. This raises concerns about cost and suitability for large-scale production.
What did the University of Surrey study find?
Catalysts made using iron and molybdenum performed comparably to, and in some measures better than, previously reported precious-metal catalysts. The best-performing catalyst delivered nearly four times the discharge capacity of an unmodified reference material and recovered 93 per cent of the electrical charge during recharging.
How were the iron-based catalysts made?
The team introduced iron into a molybdenum-based compound and heated it to different temperatures. Heating to 500°C gave the best results, creating a combination of molybdenum oxide and iron phosphate.
Where was the research published?
The study was published in the Journal of Power Sources.
