Ultra-thin film significantly improves the service life of lithium-sulfur batteries

by:CTECHi     2021-07-22

Compared with existing lithium-ion batteries, lithium-sulfur batteries with elemental sulfur as the positive electrode and metal lithium as the negative electrode have higher energy density, lower raw material costs, and better environmental compatibility. However, due to the short cycle life, lithium-sulfur batteries have not yet been practically applied in the field of large-scale energy storage and electric vehicles. Recently, 'Proceedings of the National Academy of Sciences' published an online article stating that scientists brushed an ultra-thin and ultra-light surface composite film onto the surface of the sulfur electrode, thereby significantly increasing the service life of the lithium-sulfur battery.

In an interview with reporters, Liu Wen, the first author of the paper and a professor at the Faculty of Science of Beijing University of Chemical Technology, said that in theory, lithium-sulfur batteries can achieve three times the current lithium-ion batteries. Energy storage density relieves the 'mileage anxiety' of electric vehicles. However, the charge and discharge intermediate products of the sulfur electrode will dissolve in the electrolyte solution, causing sulfur loss and side reactions, causing the lithium-sulfur electrode to fail after a few weeks of use. From the advent of lithium-sulfur batteries in the 1960s to the present, scientists have been committed to improving the stability of sulfur electrodes.

Wen Liu and Hailiang Wang, assistant professor of chemistry at Yale University, have developed a simple and easy method, namely dendrimers and graphene containing specific functional groups (amides) Simply mix, and then apply to the surface of the sulfur electrode to form a composite film. Through the protection of the surface composite film, the lithium-sulfur battery can achieve more than 1000 stable cycles. Through this technology, it is expected to produce lighter weight, better performance, and cheaper car batteries to improve the endurance of electric vehicles.

In addition, the research team also investigated the interaction between the composite membrane and the battery charge and discharge intermediate products through experiments and theoretical calculations, and determined the chemical sulfur fixation mechanism in the lithium-sulfur battery. Compared with existing research reports, the composite membrane can effectively improve the cycle performance of lithium-sulfur batteries without adding extra volume or weight, making lithium-sulfur batteries one step closer to practicality.

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