ZIF-67衍生Co-NC多孔碳材料的可控制备及其在锂-硫二次电池中的应用研究

doi:10.15541/jim20180338

摘要/Abstract

摘要：

以ZIF-67为模板制备了一系列具有不同金属Co负载量的S/Co-NC复合材料, 并将其应用于锂-硫电池正极中进行电化学性能研究。采用扫描电镜(SEM)和透射电镜(TEM)对Co-NC材料的多面体形貌及多孔结构进行表征; 采用X射线衍射(XRD)分析了Co-NC中金属Co的结晶状态; 采用氮气吸脱附方法分析了Co-NC材料的比表面积及孔结构。研究表明, 当刻蚀时间为48 h, 即Co含量为15.93wt%时, 复合硫正极呈现出最佳的循环性能以及倍率性能, 在0.2C电流密度下从第50圈到200圈循环的容量保持率为94.84%, 5.0C高倍率下的放电比容量为718.8 mAh?g ^-1。

关键词: 金属-有机框架材料, 氮掺杂多孔碳, 锂-硫电池, 循环稳定性

Abstract:

This work reported a facile strategy for preparing S/Co-NC composite sulfur cathode materials with different Co loadings derived from ZIF-67, which were applied as cathode materials for Li-S batteries. SEM and TEM were used to observe the morphology and pore structure of Co-NC composite. XRD analysis was employed to investigate the crystalline state of cobalt embedded in porous carbon materials. N₂ adsorption-desorption techniques was used to characterize the BET surface area and pore volume of Co-NC samples. Experimental results showed that the Co-NC with Co content of 15.93wt% exhibited the superior electrochemical performance. The cathode equipped with optimized composite showed a high capacity retention rate of 94.84% between 50 ^th to 200 ^th cycles at 0.2C current density, and even at high current density (5.0C), a high discharge capacity of 718.8 mAh?g ^-1 could still be obtained.

Key words: metal-organic frameworks (MOFs), N-doped porous carbon, Li-S battery, cycle stability

中图分类号:

TM911

罗世强, 郑春满, 孙巍巍, 谢威, 柯剑煌, 刘双科, 洪晓斌, 李宇杰, 许静. ZIF-67衍生Co-NC多孔碳材料的可控制备及其在锂-硫二次电池中的应用研究[J]. 无机材料学报, 2019, 34(5): 502-508.

Shi-Qiang LUO, Chun-Man ZHENG, Wei-Wei SUN, Wei XIE, Jian-Huang KE, Shuang-Ke LIU, Xiao-Bin HONG, Yu-Jie LI, Jing XU. Controllable Preparation of Co-NC Nanoporous Carbon Derived from ZIF-67 for Advanced Lithium-sulfur Batteries[J]. Journal of Inorganic Materials, 2019, 34(5): 502-508.

图/表 9

图1 S/Co-NC(0~48 h)复合材料合成示意图

Fig. 1 Schematic illustration of the preparation process of S/Co-NC(0~48 h) composites

图2 (a~b) ZIF-67前驱体和(c~d) Co-NC(48 h)的(a,c) SEM、(b,d) TEM照片; S/Co-NC复合材料的(e) TEM照片和(f)EDS元素面扫描图

Fig. 2 (a,c) SEM and (b,d) TEM images of (a-b) ZIF-67 precursors and (c-d) Co-NC (48 h); (e) TEM image and (f) EDS elemental mappings of S/Co-NC (48 h) composite

图3 (a) ZIF-67前驱体、(b) Co-NC(0~48 h)以及(c) S/Co-NC (48 h)复合材料的XRD图谱

Fig. 3 XRD patterns of (a) ZIF-67 precursor, (b) Co-NC(0~ 48 h) and (c) S/Co-NC(48 h) composites

表1 ZIF-67和Co-NC复合材料的BET结果

Table 1 BET results of ZIF-67 and Co-NC composites

Sample	BET surface area/(m²?g^-1)	Pore diameter /nm	Pore volume /(cm³?g^-1)
ZIF-67	1481.22	1.9919	0.7252
Co-NC(0 h)	272.15	8.2433	0.5608
Co-NC(6 h)	301.73	8.7121	0.6571
Co-NC(24 h)	344.41	9.6929	0.7016
Co-NC(48 h)	360.50	9.7984	0.8124

图4 ZIF-67前驱体和Co-NC(0~48 h)样品的(a)氮气吸脱附等温线、(b)孔径分布曲线以及(c) Co-NC(0~48 h)复合材料随刻蚀时间延长BET比表面积及孔体积的变化曲线

Fig. 4 (a) N2 adsorption-desorption isotherms and (b) pore size distributions of ZIF-67 and Co-NC(0~48 h) samples, (c) curves of variation trend of BET surface area and pore volume of Co-NC composites with increased etching time

表2 Co-NC复合材料中各元素质量含量及N/C比

Table 2 Elemental content of Co and N in Co-NC composites and N/C ratio data

Sample	Co-NC(0 h)	Co-NC(6 h)	Co-NC(24 h)	Co-NC(48 h)
Co/wt%	37.55	23.29	16.24	15.93
N/wt%	6.68	8.36	8.79	8.78
N/C	0.1070	0.1089	0.1056	0.1045

图5 S/Co-NC复合材料的硫含量分析

Fig. 5 TGA curves of S/Co-NC composites

图6 不同Co含量的S/Co-NC(0~48 h)电极的(a) CV曲线和(b)恒电流充放电曲线

Fig. 6 (a) CV curves and (b) discharge-charge profiles of S/Co-NC(0~48 h) electrodes with different Co contents

图7 不同Co含量的S/Co-NC(0~48 h)电极的(a)循环性能曲线、(b)倍率性能曲线以及(c)S/Co-NC(48 h)电极在1.0C电流密度下的长周期循环性能曲线

Fig. 7 (a) Cycle performances and (b) rate capabilities of S/Co-NC(0~48 h) electrodes with different Co contents; (c) Long-cycle performance of S/Co-NC(48 h) at 1.0C current density

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