《厦门大学学报（自然科学版）》

硅材料具有高理论比容量(4 200 mAh/g),是最具希望的下一代锂离子电池负极材料之一,但是硅材料巨大的体积效应(> 300%)和较差的导电性严重影响其电化学性能,阻碍其实际应用.为此,采用海藻酸水凝胶充当固定剂和碳源,将硅纳米颗粒和氧化石墨烯进行组装,制备了硅/还原氧化石墨烯/碳(Si/rGO/C)复合材料,采用粉末X射线衍射(XRD)、拉曼(Raman)光谱、热重分析(TGA)、比表面积测试、扫描电镜(SEM)和透射电镜(TEM)等表征材料的结构、化学组成及形貌,并对材料进行电化学性能测试.结果表明:rGO在复合材料内部构建了分散良好的导电网络,Si纳米颗粒填充在导电网络中并通过碳层牢固地锁定在rGO片层上.rGO与碳层的复合作用有效缓冲了Si纳米颗粒在充放电时的体积变化,并且显著提高了复合材料的导电性,因此,Si/rGO/C复合材料用作锂离子电池负极时表现出优异的电化学性能:以1.0 A/g电流密度循环100圈,保持约1 000 mAh/g的高可逆比容量以及77.6%的容量保持率.

Silicon is generally regarded as one of the most promising anode materials of lithium-ion batteries because of its high theoretical capacity(4 200 mAh/g).However,the huge volume change(>300%)and poor electronic conductivity seriously affect its electrochemical performance and hinder its practical application.In this study,the silicon/reduced graphene oxide/carbon(Si/rGO/C)anode composite was synthesized via the alginate hydrogel process:the alginate hydrogel was used as the stabilizer and carbon source,and it bundled both the Si nanoparticles and graphene oxide(GO)together and transformed to the carbon layer after high temperature carbonization.The structure,chemical composition and morphology of the composite were characterized using powder X-ray diffraction(XRD),Raman spectrum,thermogravimetric analysis(TGA),specific surface area test,scanning electron microscopy(SEM)and transmission electron microscopy(TEM),and the electrochemical properties of the composite were tested.The results showed that inside the Si/rGO/C composites,the rGO sheets were highly disperse as a conductive network and the Si nanoparticles were firmly locked on the rGO sheets with the carbon layer.The carbon layer and rGO significantly improved the electrical conducti-vity of the composite,serving as a buffer for the large volume change of Si nanoparticles.The Si/rGO/C composite used as an anode material demonstrated superior electrochemical properties,which delivered a high reversible capacity of about 1 000.0 mAh/g and 77.6% capacity retention at 1.0 A/g current density after 100 cycles.

引言
1 实验
2 结果与讨论
3 结论

图1 复合材料的制备流程示意图<br/>Fig.1 Schematic illustration of composite preparation

图1 复合材料的制备流程示意图
Fig.1 Schematic illustration of composite preparation

图2 纳米Si、Si/C、Si/rGO/C复合材料的XRD(a)和Raman(b)谱图<br/>Fig.2 XRD patterns(a)and Raman spectra(b)of nano-Si,Si/C and Si/rGO/C composites

图2 纳米Si、Si/C、Si/rGO/C复合材料的XRD(a)和Raman(b)谱图
Fig.2 XRD patterns(a)and Raman spectra(b)of nano-Si,Si/C and Si/rGO/C composites

图3 纳米Si、Si/C和Si/rGO/C复合材料的TGA曲线<br/>Fig.3 TGA curves of nano-Si,Si/C and Si/rGO/C composites

图3 纳米Si、Si/C和Si/rGO/C复合材料的TGA曲线
Fig.3 TGA curves of nano-Si,Si/C and Si/rGO/C composites

图4 纳米Si(a,b)、Si/C(c,d)、Si/rGO/C(e,f)复合材料的SEM图以及Si/rGO/C的TEM图(g,h)<br/>Fig.4 SEM images of nano-Si(a,b),Si/C(c,d),Si/rGO/C(e,f)composites and TEM images of Si/rGO/C(g,h)

图4 纳米Si(a,b)、Si/C(c,d)、Si/rGO/C(e,f)复合材料的SEM图以及Si/rGO/C的TEM图(g,h)
Fig.4 SEM images of nano-Si(a,b),Si/C(c,d),Si/rGO/C(e,f)composites and TEM images of Si/rGO/C(g,h)

图5 纳米Si、Si/C和Si/rGO/C复合材料的电化学性能<br/>Fig.5 The electrochemical properties of nano-Si,Si/C and Si/rGO/C composites

图5 纳米Si、Si/C和Si/rGO/C复合材料的电化学性能
Fig.5 The electrochemical properties of nano-Si,Si/C and Si/rGO/C composites

表1 不同方法制备Si/rGO/C复合材料的循环性能对比<br/>Tab.1 Comparison of the cycling performance of the Si/rGO/C composites prepared by different methods

表1 不同方法制备Si/rGO/C复合材料的循环性能对比
Tab.1 Comparison of the cycling performance of the Si/rGO/C composites prepared by different methods

图6 Si/rGO/C电极前5圈充放电CV曲线(a)以及纳米Si、Si/C、Si/rGO/C电极的EIS测试(b)<br/>Fig.6 CV curves of Si/rGO/C electrode in the initial five cycles(a),and EIS tests of nano-Si,Si/C and Si/rGO/C electrodes(b)

图6 Si/rGO/C电极前5圈充放电CV曲线(a)以及纳米Si、Si/C、Si/rGO/C电极的EIS测试(b)
Fig.6 CV curves of Si/rGO/C electrode in the initial five cycles(a),and EIS tests of nano-Si,Si/C and Si/rGO/C electrodes(b)

图7 纳米Si、Si/C和Si/rGO/C电极极片100次循环前后的SEM图<br/>Fig.7 Surface SEM images of the nano-Si,Si/C and Si/rGO/C electrodes before and after 100 cycles

图7 纳米Si、Si/C和Si/rGO/C电极极片100次循环前后的SEM图
Fig.7 Surface SEM images of the nano-Si,Si/C and Si/rGO/C electrodes before and after 100 cycles

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备注

引言

1 实验

2 结果与讨论

3 结论

学报简介

备注

引言

1 实 验

2 结果与讨论

3 结 论

学报简介

1 实验

3 结论