High electrochemical performances of hierarchical hydrangea macrophylla like NiCo 2 O 4 and NiCo 2 S 4 as anode materials for Li-ion batteries

Abstract In this work, hierarchical hydrangea macrophylla like NiCo 2 O 4 has been synthesized by solvothermal method followed by calcination treatment in air. By using Na 2 S as sulfur source, the NiCo 2 O 4 is converted into NiCo 2 S 4 . Such hierarchical NiCo 2 O 4 exhibits a high specific capacity and excellent cycling stability (928 mAh g −1 at a current density of 100 mA g −1 after 100 cycles). Even at high current density of 2000 mA g −1 , the electrode still delivers a specific capacity of 371 mAh g −1 after 50 cycles. When the NiCo 2 S 4 is used as anode materials for lithium-ion batteries, a high discharge capacity of 1204 mAh g −1 can be achieved. Meanwhile, the NiCo 2 S 4 electrode displays good cycling stability and rate capability. The excellent electrochemical performances can be attributed to the unique porous structure, which can effectively reduce the diffusion length for lithium ions and electrons, and alleviate volume expansion during the charge-discharge processes.