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/CoSe 2 ) composite as an anode material for lithium‐ion batteries. The prepared composite shows a wrinkled morphology with the CoSe 2 nanoparticles tightly anchored/wrapped on/in the rGO sheets. The rGO/CoSe 2 composite exhibits enhanced electrochemical performance with higher capacity, better rate capability, and cycling performance compared to pure CoSe 2 . The rGO/CoSe 2 composite delivers a high initial reversible capacity of 726 mAh g −1 and a very high capacity of 1577 mAh g −1 after 200 cycles at a current density of 200 mA g −1 (0.38 C). 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 CoSe 2 during discharge/charge processes, resulting in improved lithium‐storage performances.