Rational Design of Bi2Se3@NiSe2 Heterostructures on N-Doped CNTs as a Dual-Functional Polysulfide Mediator for High-Performance Li–S Batteries

The practical implementation of lithium–sulfur (Li–S) batteries is still impeded by two fundamental challenges: the low conductivity of lithium sulfide species (Li2S2/Li2S) and the shuttling of soluble lithium polysulfides (LiPSs). To tackle these issues, we propose an efficient polysulfide regulation strategy via a functional separator coated with Bi2Se3@NiSe2 heterostructures anchored on nitrogen-doped carbon nanotubes (N-CNTs). The rationally constructed Bi2Se3@NiSe2 interfaces not only offer strong chemisorption toward LiPSs but also act as highly active electrocatalysts to facilitate their conversion kinetics, particularly the nucleation and decomposition of Li2S. Coupled with the three-dimensional conductive network of N-CNTs, which ensures rapid electron/ion transport, the designed separator significantly suppresses the shuttle effect and enhances redox efficiency. As a result, Li–S batteries equipped with the Bi2Se3@NiSe2/N-CNT-modified separator achieve a remarkable initial discharge capacity of 1418.24 mAh g–1 at 0.1 C and outstanding long-term cyclability with a minimal decay rate of 0.083% per cycle over 500 cycles at 1 C. In situ X-ray diffraction further verifies the reversible phase evolution between α-S8 and Li2S during cycling. This work highlights the potential of bimetallic selenide heterostructures as multifunctional catalytic interlayers and provides a feasible pathway toward advanced separators for durable Li–S batteries.