Development of sulfonated-carbon nanotubes/graphene three-dimensional conductive spongy framework with ion-selective effect as cathode in high-performance lithium-sulfur batteries

Abstract

The shuttle effect of soluble intermediate polysulfide toward lithium anode, the sluggish redox kinetics of polysulfides conversion and the low lithium ion/electrical conductivity severely limited the commercialization of lithium-sulfur (Li-S) battery. To overcome the bottleneck, herein we designed a Nickel foam/graphene/sulfonated carbon nanotubes (NG/CNTs-SO3−) three-dimensional (3D) interconnected electrode. Nickel foam weaved with 1D multi-wall carbon nanotubes (MWCNT) and 2D graphene (named as NG/CNTs) is used as the host for sulfur accommodation, forming a continuously ion-electronic conductive 3D network and boosting fast redox reaction kinetic. Moreover, the negatively charged –SO3− groups transform the cathode surface from hydrophobic to hydrophilic, and it not only acts as constructing ion-selective layer for suppressing the shuttle effect of polysulfides, but also accelerates the polysulfides conversion process by strong adsorption sites to anchor polysulfides. In addition, the grafted –SO3− groups reinforce the rapid transportation of lithium-ion five times than none negatively charged groups decorated ones. The Li-S batteries with NG/CNTs-SO3− cathode delivers an initial capacity of 1380 mAh g−1 at 0.2 C, retaining a capacity of 1043.5 mAh g−1 after 100 cycles. Furthermore, the cells with NG/CNTs-SO3− cathode also exhibits excellent cycling stability with capacity decay of 0.031% at 2 C and rate capability, which confirms it is outstanding to improve the electrochemical performance and inhibit the shuttle effect.