Diamond-shaped carbon-coated CoCO3 (CoCO3/C) particles were prepared by a simple hydrothermal method, and carbon coating was realized using glucose as the carbon source. This study focuses on the electrochemical performance of CoCO3/C as an anode material. Its surface morphology and crystal lattice structure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The content and structure of the carbon coating layer were further investigated by the thermogravimetry-differential thermal analysis (TG-DTA) technique and Raman spectroscopy. The pore size distribution was characterized using the Barrett-Joyner-Halenda (BJH) method. The results show that the carbon coating process creates not only a layer of amorphous carbon on the surface of CoCO3, but also a porous structure with pore size of ~30 nm. The amorphous carbon layer enhances the structural stability during the charging and discharging process, and the porous structure facilitates the movement of ions in the electrolyte, and thus improves its electrochemical performance. When the cycling performance was tested for 500 cycles, this CoCO3/C material maintained a capacity of 539 mAh•g-1 at 0.90C (1.00C = mAh•g-1), showing its excellent cycling capacity. When the current rate was increased to 3.00C, the capacity was 130 mAh•g-1. When the current rate was returned to 0.15C, its capacity was 770 mAh•g-1, demonstrating the great rate performance and stability of CoCO3/C.
Received: 12 December 2014
Published: 08 June 2015
Fig 1 (a) XRD patterns of CoCO3 and CoCO3/C; (b) BJH plots of CoCO3/C and CoCO3; (c) Raman spectrum of CoCO3/C (the inset showing the Raman spectrum of pristine CoCO3); (d) thermogravimetric-differential thermal analysis (TG-DTA) curves of CoCO3/C
Fig 2 SEM images of (a) CoCO3 and (b) CoCO3/C; (c) TEM and (d) high resolution TEM images of CoCO3/C
Fig 3 (a) Cyclic voltammograms of CoCO3/C at a scan rate of 0.01 mV•s-1 at a voltage range of 0.01-3.00 V; (b) the first three charge and discharge curves of CoCO3/C at 0.09C rate; (c) cycling performance and coulombic efficiency of CoCO3/C and CoCO3 at 0.90C rate; (d) cycling performance of CoCO3/C at various discharge rates
Fig 4 Electrochemical impedance spectroscopy (EIS) Nyquist plots of CoCO3/C and CoCO3
Ding P. ; Xu Y. L. ; Sun X. F. Acta Phys. -Chim. Sin 2013, 29 (2), 293.