Could new iron-based catalysts bring lithium-CO₂ batteries closer to reality?

Lithium-CO₂ batteries are being explored as a promising alternative to today's lithium-ion batteries because, in theory, they could store substantially more energy for the same weight. However, the technology is still in the early stages of development, with commercial lithium-ion batteries currently outperforming them in areas such as reliability and lifespan. 

One of the biggest challenges with lithium-CO₂ batteries is finding catalysts – materials that speed up chemical reactions – that can help them charge and discharge efficiently. Many of the most effective catalysts rely on expensive and scarce precious metals such as platinum, ruthenium and iridium, raising concerns about their cost and suitability for large-scale production.  

In a study published in the Journal of Power Sources, Surrey researchers have shown that catalysts made using more widely available metals, including iron and molybdenum, can perform in a way that is comparable to, and in some measures better than, previously reported catalysts containing expensive precious metals. 

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 and completed 92 charge-discharge cycles in the laboratory, where the amount of charge released during each cycle was deliberately limited.

To develop the catalysts, the Surrey team introduced iron into a molybdenum-based compound before heating it to different temperatures to see how changes in its structure affected battery performance. 

They found that heating the material to 500°C produced the best results, creating a combination of molybdenum oxide and iron phosphate that helped the chemical reactions involved in charging and discharging take place more efficiently. 

The team now hopes to build on the findings by improving the performance and durability of the catalysts, while also exploring whether they could be used in other technologies that convert carbon dioxide. 

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Notes to editors 

• Dr Siddharth Gadkari is available for interview; please contact mediarelations@surrey.ac.uk to arrange. 
• The full paper can be found here: https://www.sciencedirect.com/science/article/abs/pii/S0378775326024298