VC/WC Heterogeneous Carbides Synergistically with Nitrogen-Doped Carbon Nanotubes for Enhanced Polysulfide Conversion Kinetics

Abstract

Lithium–sulfur (Li–S) batteries are regarded as a promising candidate for next-generation high-energy-density storage systems due to their high theoretical energy density and the abundant availability of sulfur resources. However, practical applications are severely constrained by the shuttle effect of soluble lithium polysulfides (LiPSs) and the sluggish kinetics of Li2S deposition/decomposition. To address the challenge of simultaneously optimizing adsorption capacity and catalytic activity toward sulfur species conversion, this work proposes an interfacial electronic structure regulation strategy and constructs a composite host comprising VC/WC heterogeneous carbides and nitrogen-doped carbon nanotubes (W-VC@NCNTs). Through hydrothermal assembly and high-temperature carbonization, VC and WC nanocrystallites were in situ fabricated on the surface of nitrogen-doped carbon nanotubes. Benefiting from the moderate downshift of the d-band center induced by electron transfer from V to W at the VC/WC heterointerface, the composite achieves effective chemical anchoring of LiPSs while avoiding product poisoning caused by excessively strong adsorption, thereby realizing an optimal balance between adsorption strength and catalytic activity. Combined with the continuous electron/ion transport pathways provided by the defect-rich nitrogen-doped carbon network, the bidirectional energy barriers for Li2S nucleation and oxidative decomposition are significantly reduced. Experimental results demonstrate that the W-VC@NCNTs electrode exhibits faster charge transfer, lower interfacial polarization, and superior Li2S nucleation/decomposition kinetics, with a capacity decay rate of only 0.062% per cycle over 500 cycles at 1 C. This study elucidates the mechanism by which interfacial electronic modulation in heterogeneous carbides promotes polysulfide catalytic conversion, offering an effective strategy for the design of sulfur host materials for high-performance Li–S batteries.