Tailoring nickel–cobalt bimetallic alloy as highly effective catalyst in modified separators for high-performance lithium-sulfur batteries

Abstract

Lithium–sulfur batteries (LSBs) are anticipated as most prospective new generation energy storage systems due to their high theoretical specific capacity, high energy density and low cost. However, their practical applications are seriously hindered by the sluggish redox kinetics of soluble liquid polysulfide intermediates during discharge-charge. Herein, nickel-cobalt bimetallic alloy/bamboo-like carbon nanotubes composite (NiCo/BCNTs) is rationally developed by a one-step calcination method toward this challenge. The results indicate that the Ni and Co nanoparticles not only strongly confine the lithium polysulfides (LiPSs) but also effectively catalyze its conversion reactions by lowering the energy barrier, while the BCNTs enable a large surface area for more active site exposure and provide fast electron/ion pathways. As expected, LSBs with NiCo/BCNTs electrocatalyst modified separators present a reversible specific capacity with 1495.6 mAh g−1 at 0.1 C. More importantly, a high reversible capacity of 544.8 mAh g−1 over 1000 cycles with a low capacity damping of 0.063% per cycle at 2 C is also acquired. This work provides a deeper insight into the regulation of polysulfide redox kinetics in electrocatalysts for LSBs.