Pineapple-shaped ZnCo2O4 microspheres as anode materials for lithium ion batteries with prominent rate performance

Pineapple-shaped ZnCo2O4 (ZCO) microspheres with a porous nanostructure are synthesized by a typical hydrothermal method and used as high performance anodes in Li-ion batteries. The microspheres show excellent cycling and rate performance. The initial discharge capacity of 1596.2 mA h g(-1) and the reversible discharge capacity of 1132 mA h g(-1) can be maintained after 120 cycles at a current density of 100 mA g(-1). More interestingly, the reversible capacity as high as 800 mA h g(-1) can be retained at a high current density of 1000 mA g(-1) after 200 cycles. Surprisingly, the pineapple-shaped ZCO electrode exhibits a prominent rate performance, a reversible specific capacity of 1237 mA h g(-1) and 505 mA h g(-1) at current densities of 500 mA g(-1) and 6000 mA g(-1) respectively. In addition, the influence of distilled water and urea on the phase and morphology of the material is investigated by SEM and EDS. The results indicate that adding distilled water into the solvent could ensure the high purity of products with no loss of the Zn element. At the same time, the cycle performance can be effectively improved because of the more regular surface and the more stable structure of the microspheres with urea-assistance.