Rational design of multi-functional CoS@rGO composite for performance enhanced Li-S cathode

Lithium-sulfur battery has drawn widely attention due to its high theoretical energy density, in addition to the abundant and affordable sulfur. However, the battery performances are still not satisfied due to the undesired shuttle effect of polysulfides, the sluggish reaction kinetics, together with the intrinsic non-conductivity of active materials. Thus, the preparation of sulfur host materials with polar, catalytic and conductive properties can be an effective tactics. In this work, a cobalt sulfide@reduced graphene oxide composite has been designed and synthesized by a facile method, in which the CoS nanoparticles can provide more polar and catalytic sites to adsorb the polysulfides and accelerate the kinetics of polysulfides conversion. The rGO can serve as composite skeleton that could not only enhance the conductivity of electrodes, but also provide a sheet structure, preventing the aggregation of CoS nanoparticles. Moreover, the C-S bonds between CoS and carbon can further promote charge transfer and stabilize the composite. Benefiting from the trifunctional sulfur-host, the as-prepared cathode exhibits low self-discharge, good cycling stability and high rate performance for 602.0 mAh g(-1) at 2 C. This sulfur-host design can be considered an effective and simple strategy for advanced Li-S battery.