Stable cycling of Li-S batteries by simultaneously suppressing Li dendrites growth and polysulfides shuttle enabled by a bioinspired separator
Lithium-sulfur (Li-S) batteries are very promising candidates for next-generation high-energy-storage devices. However, the uncontrollable Li dendrites growth and notorious polysulfides shuttle severely hinder their real world applications. Here, we report a bioinspired separator to address these issues simultaneously. The separator is prepared by successive deposition of silicone nanofilaments and polydopamine on the Celgard@2400 separator. The separator has a 3D crosslinked network with abundant O, N-containing groups and Si-O groups, which can redistribute the Li+ in electrolyte at the molecular level to realize fast Li+ diffusion and uniform Li+ flux. Thus, long-term stable Li stripping/plating is achieved even at a high current density of 10 mA cm−2. Meanwhile, these polar groups can act as lithiophilic sites to effectively suppress polysulfides shuttle by forming Li-O and Li-N bonds with polysulfides. Consequently, the separator enables stable cycling of the Li-S battery with high S loading CNTs/S cathode (4.3 mg cm−2). The battery features slow capacity decay (0.018% per cycle over 1000 cycles at 1.0 C), high specific energy density (569.2 W h kg−1) and high average Coulombic efficiency (98.71%). This study demonstrates the potential of advanced separators for high-performance Li-S batteries by realizing stable electrochemical interfaces at anode and cathode.