Safe lithium-sulphur batteries at high temperatures

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Researchers at the University of Western Ontario, in collaboration with a team from the Canadian Light Source, have leveraged a coating technique dubbed molecular layer deposition (MLD) that promises to lead to safe and durable high-temperature Lithium-sulphur (Li-S) batteries.

Li-S batteries have been pursued as an alternative to lithium-ion (Li-ion) batteries for powering electric vehicles due to their ability to hold up to four times as much energy per unit mass as Li-ion.

However, the sulphur in the electrode of Li-S batteries can be depleted after only a few charge-discharge cycles. Also, the electrolyte can be fouled by polysulphides passing through the cathode. Another issue Li-S batteries face is the difficulty of ensuring safe operation at high temperatures as they have low boiling and flash temperatures.

The researchers’ MLD technique is essentially an adaptation of the conventional atomic layer deposition (ALD) techniques that have been used to deposit thin inorganic oxide films. Where MLD varies from its predecessor is that it can incorporate organic components into the films, making it possible to create hybrid organic-inorganic thin films. MLD is a technique that has proven itself applicable for use in energy storage systems; it is said to provide a high level of control over film thickness and the chemical composition of the target material at a molecular scale.

The researchers fabricated safe, high-temperature Li-S batteries on universal carbon-sulphur electrodes using an MLD alucone coating

Andy Xueliang Sun, who led the research at the University of Western Ontario, said: “We demonstrated that MLD alucone coating offers a safe and versatile approach toward lithium-sulphur batteries at elevated temperature.”

In the experiments, the researchers demonstrated that the MLD alucone coated carbon-sulphur electrodes remained stable and even showed improved performance at temperatures as high as 55°C. The researchers expect that these performance figures should significantly prolong battery life for high-temperature Li-S batteries.