Atomic and Molecular Layer Deposition for Superior Lithium-Sulfur Batteries: Strategies, Performance, and Mechanisms

Lithium-sulfur (Li-S) batteries hold great promise for powering future electric vehicles, given their high theoretical specific energy of 2600 Wh/kg and low cost. However, the commercialization of Li-S batteries is being hindered by several serious technical challenges including the corrosion of lithium metal anodes, the formation of lithium dendrites, the shuttle effect of lithium polysulfides, the decomposition of electrolyte, and low conductivity of sulfur and lithium sulfide. In the past decade, atomic layer deposition (ALD) as a new research thrust has been demonstrated to be a very effective technique in dramatically improving the performance of lithium-ion batteries (LIBs), featuring many unique advantages in fabricating sub-nano to nanoscale inorganic films. Stimulated by ALD's benefits, recently more and more research efforts have been reported in ALD for addressing the technical issues of Li-S batteries and show very promising outcomes. Analogous to ALD, molecular layer deposition (MLD) is a thin-film technique exclusively for polymeric films. Some of the latest studies have uncovered that MLD is an alternative tool for tackling the challenges of Li-S batteries with exceptional effectiveness. In this review, for the first time, we systematically summarized the progresses of both ALD and MLD in developing superior Li-S batteries, covering their technical strategies, resulting performance, and the underlying mechanisms. In terms of the functionalities of ALD and MLD in Li-S batteries, we focus our discussion in two main complementary aspects: (i) surface coatings and (ii) electrode designs.