Hydrothermal Preparation and Electrochemical Properties of Co-S alloys

doi:10.3724/SP.J.1077.2014.13514

Abstract

Abstract:

The Co-S alloys were prepared by a hydrothermal method and the process parameters were optimized. The surface morphology and phase structure of Co-S alloys were characterized by SEM and XRD. The electrochemical properties of Co-S alloys were investigated by galvanostatic charge and discharge tests, cyclic voltammetry and AC impedance. The results indicated that the as-prepared Co-S alloy, which was synthesized using a 70% packing volume of the reaction solution at 160℃ for 12 h, showed good crystallinity. This alloy consisted of metallic Co and Co₉S₈phases with a cross-linked lamellar morphology of about 50 nm in thickness. It possessed a maximum discharge capacity of 536 mAh/g at charge and discharge current density of 150 mA/g and a good cycling stability with capacity retention rate of 77.4% after 50 cycles. The redox reactions between Co and Co(OH)₂ were the main reaction during charge and discharge. Partial dissolution of Co reduced the active material and led to capacity decay.

Key words: hydrothermal method, Co-S alloy, process parameters, electrochemical properties

CLC Number:

TQ174

HU Li-Na, ZHAO Xiang-Yu, LI Jia-Jia, YANG-Meng, MA Li-Qun, ZHANG Li-Yan. Hydrothermal Preparation and Electrochemical Properties of Co-S alloys[J]. Journal of Inorganic Materials, 2014, 29(7): 747-752.

Figures/Tables 9

Fig. 1 Cycling stability of the Co-S alloys prepared with different packing volumes after heat-treatment at 160℃ for 12 h

Fig. 2 Cycling stability of the Co-S alloys prepared with 70% packing volumes after heat-treatment at different temperatures for 12 h

Fig. 3 Cycling stability of the Co-S alloys prepared with 70% packing volumes after heat-treatment at 160℃ for different time

Fig. 4 XRD patterns of the Co-S alloys prepared with 70% packing volumes after heat-treatment at 160℃ for different time

Fig. 5 SEM images of the Co-S alloys prepared with 70% packing volumes after heat-treatment at different temperatures for 12 h (a) 150℃; (b) 160℃; (c) 170℃

Fig. 6 Charge and discharge curves of the Co-S electrodes at current density of 150 mA/g

Fig. 7 Cyclic voltammetry curves of Co-S electrodes

Fig. 8 XRD patterns of the Co-S electrodes after charge and discharge

Fig. 9 EIS spectra of the Co-S electrodes (a) Nyquist plots; (b) Bode-phase plots

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