Polydopamine-assisted synthesis of hollow NiCo ₂ O ₄ nanospheres as high-performance lithium ion battery anodes

Hollow NiCo2O4 nanospheres with the outer diameter of about 60 nm and inner diameter of around 40 nm are prepared using monodisperse polydopamine spheres as the templates followed by a calcination process. The shell of the obtained NiCo2O4 is composed of nanoparticles with inter-particle spaces of below 10 nm. When they are employed as an anode in lithium-ion batteries, the hollow NiCo2O4 nanospheres with mesoporous shells exhibit superior electrochemical performances in terms of high reversible capacity, excellent rate capability and cycling stability. When galvanostatic discharging/charging at 0.2, 0.6, 1.0 and 2.0 A g−1, the anode can deliver discharge capacities as high as 1210, 1053, 923 and 659 mA h g−1, respectively. Moreover, the reversible capacity could be maintained at 695 mA h g−1 under the current density of 2.0 A g−1 for 200 cycles. These make the hollow NiCo2O4 nanospheres promising candidates for anode materials in high-energy and high-power lithium ion batteries.