Efficient polysulfides trapping and redox enabled by Co/N-carbon implanted Li+-montmorillonite for advanced lithium-sulfur batteries

Abstract

Li-S batteries are very promising next-generation energy storage systems due to their high theoretical capacity and energy density, but suffer from sluggish redox kinetics and serious polysulfides (PS) shuttle. Herein, Co/N-carbon implanted Li+-montmorillonite (Co/NC@Li-MMT) is designed to inhibit PS shuttle and maximize PS redox kinetics in Li-S battery. The Co/NC@Li-MMT 2D nanomaterial is fabricated by exfoliation of the Li-MMT nanosheets using melamine and Co(II)(acac)2, followed by one-step thermal reduction. The exfoliated Co/NC@Li-MMT with high Li+ and electrical conductivity can expose abundant active sites for efficient PS adsorption via Co-S and Si-S and Li bonds and for fast PS electrocatalytic conversion via Co and CoNC catalytic active sites. The Co/NC@Li-MMT modified PP (Co/NC@Li-MMT@PP) separator with a thin Co/NC@Li-MMT layer of 2.2 μm (0.3 mg cm−2 mass loading) features high Li+ conductivity, fast Li+ diffusion, superior electrolyte wettability as well as efficient PS trapping and fast PS redox kinetics as verified by various analytical techniques. Consequently, the Li-S battery with the Co/NC@Li-MMT@PP separator shows high initial capacity (1447 mAh/g), good rate performance, excellent cycling stability (0.027 % capacity fade per cycle at 1C over 300 cycles) and ultralow self-discharge.