Binder-free anodes composed of electrospun carbon fibers were prepared for lithium-ion batteries. Nickel-cobalt binary hydroxide (Ni-Co(OH)(2)) was coprecipitated on the electrospun carbon fibers to form a hierarchical structure with Ni-Co(OH)(2) nanoflakes vertically attached on the fiber surface. When the composite fibers were annealed in air, Ni-Co(OH)(2) nanoflakes were converted to NiCo2O4 nanosheets at 300 degrees C. Further increasing the annealing temperature to 400 degrees C resulted in the aggregation of NiCo2O4 on the fiber surface, causing the loss of NiCo2O4 nanostructures. When used as anodes, the composite fibers exhibited the higher specific capacity than the pristine carbon fibers. This was attributed to the hierarchical structure of the composite fibers in which the high surface area and rich mesopores of Ni-Co compounds provided easily accessible ion transport across electrolyte/electrode interfaces and additional lithium storage, respectively. Additionally, Ni-Co compounds possessed the high theoretical capacities. By contrast, the interconnected carbon fibers served as a conductive path for charge transfer. They also acted as a buffer to alleviate the Ni-Co-compound volume expansion and contraction during discharging and charging. Among all the samples, the composite fibers annealed at 300 degrees C exhibited the highest capacity of 734 mAh g(-1) at a current density of 150 mA g(-1). (c) 2017 The Electrochemical Society.