An atomic layer deposited (ALD) Al 2 O 3 coating applied to sulfur cathodes has been studied in this paper. It is demonstrated that the Al 2 O 3 coating improves the cycling stability of Li-sulfur batteries. The underlying mechanism by synchrotron-based X-ray photoelectron spectroscopy was investigated. The coating layer not only protects the polysulfide from dissolution, but also facilitates the utilization of sulfur, demonstrating improved electrochemical performances. Li-sulfur batteries

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... been considered as one of the most promising power storage systems for electric vehicles, owing to their overwhelming advantages in specic capacity and energy density. 1-5 Moreover, sulfur is attractive in its low cost, abundance, and environmental benignity. 1-5 Nevertheless, the present Li-sulfur batteries suffer from two major problems, which seriously hinder their commercial application. 6-12 One major issue is the inherent insulating nature of sulfur and discharge products Li 2 S n (n < 2), which greatly limits the performance of Li-sulfur batteries. 6-12 Another issue is that polysulde species, the dissolved intermediate product, will migrate between two electrodes and chemically react with lithium metal or sulfur cathode directly, leading to a drastic corrosion of lithium metal and loss of sulfur active material. This phenomenon is known as "shuttle effect". [6] [7] [8] [9] [10] [11] [12] To improve the conductivity of sulfur cathodes, the prevailing strategies are addition of carbon materials, which has been endeavoring to the prosperity of Li-S batteries. 6-14 On the other hand, it has been widely accepted that the "shuttle effect" could be alleviated by coating S-based composites with conductive polymer, 14,15 metal oxides, 16,17 as well as graphene and carbon papers, 13,18-21 et al. Atomic layer deposition (ALD) is a thin lm