Lithium-sulfur (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, Li-S batteries don’t come without some problems. For instance, the sulfur in the electrode can become depleted after just a few charge-discharge cycles, or polysulfides can pass through the cathode and foul the electrolyte.
Another issue Li-S batteries face is the difficulty of ensuring that they operate safely at high temperatures due to their low boiling and flash temperatures. Now, researchers at the University of Western Ontario, in collaboration with a team from the Canadian Light Source, have leveraged a relatively new coating technique dubbed molecular layer deposition (MLD) that promises to lead to safe and durable high-temperature Li-S batteries.
This 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 departs 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 provides a high level of control over film thickness and the chemical composition of the target material at a molecular scale.
In research described in the journal Nano Letters, the Canadian researchers were able to fabricate safe, high-temperature Li–S batteries on universal carbon–sulfur electrodes using an MLD alucone coating
“We demonstrated that MLD alucone coating offers a safe and versatile approach toward lithium-sulfur batteries at elevated temperature,” said Andy Xueliang Sun, who led the research at the University of Western Ontario, in a press release.
In the experiments, the researchers demonstrated that the MLD alucone coated carbon-sulfur electrodes remained stable and even showed improved performance at temperatures as high as 55 degrees Celsius. The researchers expect that these performance figures should significantly prolong battery life for high-temperature Li-S batteries.