Researchers from the University of Surrey (UK) have found that catalysts based on common metals - iron and molybdenum - can perform in lithium-carbon dioxide batteries no worse than, and in some respects better than, materials containing precious metals. The work was published in the Journal of Power Sources.
Lithium-carbon dioxide batteries (lithium-CO2) are seen as a promising replacement for modern lithium-ion batteries: in theory they can store significantly more energy at the same weight. However, the technology is still at an early stage, and commercial lithium-ion batteries surpass it in reliability and service life.
One of the main problems is catalysts, that is, substances that speed up chemical reactions. Many effective catalysts contain expensive and rare metals: platinum, ruthenium, iridium. This raises questions about cost and the possibility of mass production.
In experiments, the team's best catalyst provided almost four times the discharge capacity (the amount of charge a battery delivers on discharge) of an unmodified reference material. On recharge, 93% of the charge was recovered, and 92 charge-discharge cycles were also completed in the laboratory. The amount of charge in each cycle was deliberately limited.
To obtain the catalysts, iron was added to a molybdenum-based compound, which was then heated to different temperatures to check how changes in structure affect battery performance. The best result came from heating to 500 degrees: a combination of molybdenum oxide and iron phosphate formed, which helped the charge and discharge reactions proceed more efficiently.
According to study co-author Daniel Commander, lithium-CO2 batteries are still far from appearing in everyday devices, but the results are an encouraging step forward. The scientists showed what the materials can achieve in the laboratory, and the next task is to ensure stable operation over a much longer time.
The researchers now intend to improve the performance and durability of the catalysts, as well as study the possibility of their use in other carbon dioxide conversion technologies.