Reduced Graphene Oxide/Marcasite-Type Cobalt Selenide Nanocrystals as an Anode for Lithium-Ion Batteries with Excellent Cyclic Performance

We report a graphene/cobalt selenide (rGO/CoSe2) composite as an anode material for lithium-ion batteries. The prepared composite shows a wrinkled morphology with the CoSe2 nanoparticles tightly anchored/wrapped on/in the rGO sheets. The rGO/CoSe2 composite exhibits enhanced electrochemical performance with higher capacity, better rate capability, and cycling performance compared to pure CoSe2. The rGO/CoSe2 composite delivers a high initial reversible capacity of 726 mAhg(-1) and a very high capacity of 1577 mAhg(-1) after 200 cycles at a current density of 200 mAg(-1) (0.38C). The rGO sheets in the composite play important roles for the improvement in electrochemical properties, for example, the rGO sheet not only enhances the electrical conductivity of the whole electrode, but also alleviates the structure degradation caused by volume expansion of CoSe2 during discharge/charge processes, resulting in improved lithium-storage performances.