Researchers, including one of Indian-origin, have developed a prototype of a next-generation lithium-sulphur battery which takes its inspiration in part from the cells lining the human intestine. The batteries, if commercially developed, would have five times the energy density of the lithium-ion batteries used in smartphones and other electronics, the study said.
Working with collaborators at the Beijing Institute of Technology, the Cambridge University researchers based in Vasant Kumar’s team in the Department of Materials Science and Metallurgy developed and tested a lightweight nanostructured material which resembles villi, the finger-like protrusions which line the small intestine.
In the human body, villi are used to absorb the products of digestion and increase the surface area over which this process can take place. In the new lithium-sulphur battery, a layer of material with a villi-like structure, made from tiny zinc oxide wires, is placed on the surface of one of the battery’s electrodes.
This can trap fragments of the active material when they break off, keeping them electrochemically accessible and allowing the material to be reused. “This gets us a long way through the bottleneck which is preventing the development of better batteries,” said study co-author Paul Coxon from Cambridge’s Department of Materials Science and Metallurgy.
Sulphur and lithium react differently, via a multi-electron transfer mechanism meaning that elemental sulphur can offer a much higher theoretical capacity, resulting in a lithium-sulphur battery with much higher energy density. However, when the battery discharges, the lithium and sulphur interact and the ring-like sulphur molecules transform into chain-like structures, known as a poly-sulphides.
As the battery undergoes several charge-discharge cycles, bits of the poly-sulphide can go into the electrolyte, so that over time the battery gradually loses active material. By preventing the degradation of the battery caused by the loss of material within it, the new design, reported in the journal Advanced Functional Materials, overcomes one of the key technical problems hindering the commercial development of lithium-sulphur batteries.