Improvement On Performance Of Co₃O₄Anode Materials For Lithium Ion Batteries

With the energy crisis intensified, urging on the worldwide researches in batteries for energy storage and industrial application, especially on the lithium ion batteries. Co3O4has a good electrochemical behavior and high theoretical capacity (890mAh g-1). The main objective in this research is to develop methods for enhancing the initial coulombic efficiency and cycling performance of3d transition metal oxide. We develop several methods to improve the electrochemical performances of Co3O4, such as preparation of nanostructure, surface modification and composites.Co3O4/C core/shell nanowire arrays on nickel foam substrate are directly prepared by facial hydrothermal synthesis and magnetron sputtering. It is clearly observed that a carbon layer is well coated on the surface of Co3O4nanowire and the thickness of carbon layer is about18nm from the TEM picture. The Co3O4/C core/shell nanowire array delivers an initial discharge capacity of1330.8mAh g-and exhibits a good capacity retention without obviously capacity fading. It can still remain989.0mAh g-1after50cycles, while the pure Co3O4nanowire fades quickly, remains only490.5mAh g-1after50cycles. Obviously, the amorphous carbon layer with good conductivity could enhance the electrode/electrolyte interface stability, and effectively buffer the volume change of Co3O4during lithium ion insertion/extraction, leading to improved electrochemical properties.Hierarchical Co3O4-NiO composite nanowire arrays grown directly on nickel foam are synthesized via two step facial hydrothermal synthesis. This novel composite structure exhibits a high reversible capacity of1563.9mAh g-1in the initial cycle and good cycling performance of980.4mAh g-1after50cycles at a current density of100mA g-1, while the pure Co3O4nanowire fades quickly, remains only810.3mAh g-1after50cycles. The improved electrochemical performance of Co3O4-NiO composite nanowire arrays could be attributed to the unique hierarchical nanostructure and synergistic effect of composite. On the one hand, the nanowire array configuration enables the full exposure of both active materials to the electrolyte. On the other hand, the NiO nanosheet direct grown in the Co3O4nanowire, making both the Co3O4nanowire and NiO nanosheet accessible to the electrolyte.