Electrochemically active separators with excellent catalytic ability toward high-performance Li–S batteries

Abstract

Separator modification has been proven to be a promising technology to realize high sulfur-utilization and long-life Li–S batteries. However, only relying on the chemisorption of polar materials or the conductivity of carbon materials cannot effectively accelerate polysulfide redox kinetics. Therefore, it's urgent to propose an effective strategy to solve the above problems simultaneously so as to accomplish high-performance Li–S batteries. Hence, in this paper, we present a new separator, which could not only show strong chemisorption with polysulfides but also accelerate polysulfide redox kinetics. What's more, VS₄/graphene (VS₄/G) coating materials are electrochemically active in Li–S battery systems, which could provide extra capacity for Li–S batteries. Attributed to the strong adsorption, fast lithium ion diffusion, reduced polarization potential and facile lithium ion transfer rate across the separator, the batteries with VS₄/G coating modified separators exhibited enhanced electrochemical performance. When cycled at 2C, they could deliver an initial specific capacity of 810 mA h g⁻¹, and when subjected to 2500 charge–discharge cycles, they could retain a decay rate as low as 0.021% per cycle.