The commercial use of lithium−sulfur (Li−S) batteries is hampered by the shuttle phenomenon in cathodes and the uncontrolled growth of Li dendrites in anodes. Designing functional material-coated separators is gaining importance in the effort to tackle these issues in both of the electrodes simultaneously. Here, an initiated chemical vapor deposition (iCVD) technique is introduced in Li−S batteries for the first time to homogeneously deposit a polyvinylimidazole (pVIDZ) nanolayer on the separator. An ultrathin and ultralight-weight polymer coating nanolayer with a thickness of 70−100 nm and a weight of 0.055 mg cm −2 was achieved. Furthermore, the pVIDZ layer on the separator was observed to perform a bifunctional role in stabilizing the anode by alleviating Li dendrite growth and also to improve the cycle stability of the cathode by inhibiting the shuttle phenomenon. Consequently, even with high sulfur loading electrodes of 4 mg cm −2 , the use of iCVD-derived bifunctional separators exhibits an initial discharge capacity of 881 mA h g −1 at a rate of 1.0 C while maintaining 84.5% of its initial capacity after 300 cycles corresponding to a capacity decay of only 0.051% per cycle.
Despite their capability, sub‐10 nm periodic nano‐patterns formed by strongly segregating block copolymer (BCP) thin films cannot be easily oriented perpendicular to the substrate due to the huge surface energy differences of the constituent blocks. To produce perpendicular nano‐patterns, the interfacial energies of both the substrate and free interfaces should be controlled precisely to induce non‐preferential wetting. Unfortunately, high‐performance surface modification layers are challenging to design, and different kinds of surface modification methods must be devised respectively for each neutral layer and top coat. Furthermore, conventional approaches, largely based on spin‐coating processes, are highly prone to defect formation and may readily cause dewetting at sub‐10 nm thickness. To date, these obstacles have hampered the development of high‐fidelity, sub‐5 nm BCP patterns. Herein, an all‐vapor phase deposition approach initiated chemical vapor deposition is demonstrated to form 9‐nm‐thick, uniform neutral bottom layer and top coat with exquisite control of composition and thickness. These layers are employed in BCP films to produce perpendicular cylinders with a diameter of ≈4 nm that propagate throughout a BCP thickness of up to ≈60 nm, corresponding to five natural domain spacings of the BCP. Such a robust approach will serve as an advancement for the reliable generation of sub‐10 nm nano‐patterns.
Front Cover: In article 1900514 by Joona Bang, Sung Gap Im, and co‐workers, a robust neutralization methodology is developed to neutralize the two interfaces in a block copolymer film via initiated chemical vapor deposition. A highly uniform film of crosslinked AB‐type random copolymers, sandwich an AB‐type block copolymer film to produce perpendicular sub‐5 nm nanodomains.
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