Application of magnetron sputtering to deposit a multicomponent separator with polysulfide chemisorption and electrode stabilization for high-performance lithium‑sulfur batteries

Abstract

Lithium‑sulfur battery has attracted immense attention because of its extraordinary high energy density and theoretical capacity. However, its practical application has been seriously hindered by the rapid capacity degradation associated with the “shuttle effect” and unstable electrodes. Such negative issues during charge-discharge process could be alleviated by modification of the separator, which is demonstrated in this paper. Here, we report a sandwich-type vanadium nitride/polyvinylidene fluoride-polymethylmethacrylate/hexagonal boron nitride separator (VN/PVDF-PMMA/hBN) by electrospinning of PVDF-PMMA nanofiber membrane, followed by magnetron sputtering of VN and hBN layer at the opposite size of the membrane. Compared to conventional coating method, magnetron sputtering led to an ultrathin coating layer of 200 nm. The sputtered VN/PVDF-PMMA/hBN separator showed higher porosity (68.7%) than commercial polypropylene (PP) separator (44.5%), and significantly high electrolyte uptake (335.8% s. 175.9%), which can lead to rapid transportation of lithium ions. In the meantime, the membrane showed clear benefit in inhibiting polysulfide diffusion and lithium metal electrode stabilization due to the presence of polar CO groups that interact with the polysulfides. As a result, the LiS battery with VN/PVDF-PMMA/hBN separator showed a high initial discharge capacity of 1077.4 mAh g−1 at 0.2C, which only slightly decreased to 905.1 mAh g−1 after 200 cycles. Significantly higher than the battery with commercial PP separator.