Construction of NiCoO₂-(Ni,Co)Se₂ hybrid nanorods as an effective bifunctional interlayer for lithium‑sulfur batteries

The practical application of lithium‑sulfur (Li[sbnd]S) batteries is hindered by the shuttle effect caused by the dissolution of polysulfides in the electrolyte during the charge-discharge process, and the sluggish kinetic conversion of polysulfides. In this work, we present a novel hybrid material, nanorod-shaped NiCoO₂-(Ni,Co)Se₂ hybrid (NCOSe), synthesized through simple hydrothermal and further selenization methods. These NCOSe hybrid nanorods were uniformly coated onto a commercial polypropylene (PP) separator via vacuum filtration for application in Li[sbnd]S batteries. In the hybrid structure, the NiCoO₂ nanorod component exhibits strong polysulfides adsorption due to its high polarity, while (Ni,Co)Se₂ part promotes favorable polysulfides conversion due to superb catalytic conversion properties. Electrochemical testing reveals that the Li[sbnd]S full cell with the bifunctional NCOSe/PP separator delivers an initial specific capacity of 1277 mAh g⁻¹ at a current density of 0.1C (1C = 1675 mA g⁻¹). After 200 cycles at 0.2C, the specific capacity reaches 793 mAh g⁻¹, with a low average capacity decay of just 0.123 % per cycle. With a higher sulfur loading of 3.0 mg cm⁻², the cell achieves a specific capacity of 455 mAh g⁻¹ after 220 cycles at 0.5C, and with a maximum sulfur loading of 4.4 mg cm⁻² at 0.5C, it still maintains 72 % (311 mAh g⁻¹) of its initial capacity after 400 cycles. This study introduces a novel hybrid material with dual functionalities-enhanced polysulfides adsorption and accelerated polysulfides conversion, offering improved cycling stability of Li[sbnd]S batteries.