Facile synthesis of mesoporous NiCo2O4 nanoneedle arrays on three dimensional graphene thin film grown on Ni foam for a high-performance binder-free lithium-ion battery anode

Mesoporous NiCo 2 O 4 nanoneedle arrays on graphene film grown directly on a three-dimensional Ni foam have been fabricated by a facile hydrothermal method , accompanied by annealing under air atmosphere. The BET specific surface area of NiCo 2 O 4 @graphene film@Ni foam is as high as 47.65 m 2  g −1 . The porous composites served as a binder-free anode material for lithium-ion batteries display an excellent and stable electrochemical performance with high specific capacities of 1232 mAh g −1 at the current density of 500 mA g −1 over 100 cycles and 1493 mAh g −1 at the current density of 1500 mA g −1 after 230 cycles with Coulombic efficiency higher than 97%. Moreover, a fairly high rate capacity of 586 mAh g −1 retained even at a high current density of 8000 mA g −1 . The outstanding electrochemical performance should be attributed to synergetic effect of NiCo 2 O 4 nanoneedle arrays with mesoporous nature and high specific area as well as graphene substrate supporting, which can accommodate the volume variation during the electrochemical reactions and facilitate the ion and electron transmission.