In this study, hydrothermal synthesis of sea urchin-like NiCo2O4 was successfully demonstrated by a versatile charge-driven self-assembly strategy using positively charged poly(diallydimethylammonium chloride) (PDDA) molecules. Physical characterizations implied that sea urchin-like microspheres of ~ 2.5 μm in size were formed by self-assembly of numerous nanoneedles with a typical dimension of ~ 100 nm in diameter. Electrochemical performance study confirmed that sea urchin-like NiCo2O4 exhibited high reversible capacity of 663 mAh g-1 after 100 cycles at current density of 100 mA g-1. Rate capability indicated that average capacities of 1085, 1048, 926, 642, 261, and 86 mAh g-1 could be achieved at 100, 200, 500, 1000, 2000, and 3000 mA g-1, respectively. The excellent electrochemical performances were ascribed to the unique micro/nanostructure of sea urchin-like NiCo2O4, tailored by positively charged PDDA molecules. The proposed strategy has great potentials in the development of binary transition metal oxides with micro/nanostructures for electrochemical energy storage applications.
Keywords: Hydrothermal synthesis; Lithium-ion batteries; NiCo2O4; Self-assembly.