Graphene-encapsulated cobalt sulfides nanocages with excellent anode performances for lithium ion batteries

A layer-by-layer assembled composite of graphene nanosheets (GNSs) wrapped monodisperse cobalt sulfides (CoS2) nanocages has been prepared via a solvothermal method. The flexible GNSs in the layered composite act as the effective matrix to encapsulate the monodisperse CoS2 nanocages, buffer the volume changes and prevent the aggregation of the CoS2 nanocages during electrochemical cycling. The loosely stacked GNSs, which are induced with the insertion of CoS2, are convenient for electrolyte wetting and serve as highway for the rapid electron and lithium transport. The monodisperse nanocages can supply additional space to tolerate the volume changes, shorten lithium diffusion path, and do not tend to aggregate. As a result, the specific sample can deliver a high capacity approaching 800 mA h g(1) after 150 cycles at 100 mA g(1) and 697 mA h g(1) after 300 cycles at 500 mA g(1), in addition to good capacity retention and excellent rate capability, making it a promising candidate as next-generation anode materials for lithium-ion batteries. (C) 2015 Elsevier Ltd. All rights reserved.