A LiAlO₂/nitrogen-doped hollow carbon spheres (NdHCSs) modified separator for advanced lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have gained significant attention due to their ultrahigh theoretical specific capacity and energy density. However, their practical commercialization is still facing many intractable problems, of which the most difficult is the shuttle effect of dissolved polysulfides. To restrict the shuttle of polysulfides, herein, a novel double-layer lithium aluminate/nitrogen-doped hollow carbon sphere (LiAlO₂/NdHCSs)-modified separator was designed. The upper NdHCSs layer on the separator works as the first barrier to physically and chemically adsorb polysulfides, whereas the bottom LiAlO₂ layer acts as the second barrier to physically block the polysulfides without restricting the Li⁺ transport due to the high ionic conductivity of LiAlO₂. Cells with the LiAlO₂/NdHCSs-modified separator showed an initial discharge capacity of 1500 mA h g^-1 at 0.2C, and a discharge capacity of 543.3 mA h g^-1 was obtained after 500 cycles at 2C. Especially, when the areal density of the active material was increased to 4.5 mg cm^-2, the cells retained a discharge capacity of 538.6 mA h g^-1 after 100 cycles at 0.5C. The outstanding electrochemical performance of Li-S cells with the LiAlO₂/NdHCSs-modified separators show a new approach for the applications of Li-S batteries.