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Preparation and Electrochemical Lithium Intercalation Performance of Segmented Carbon Nanofibers
Wu Guotao,Wang Miao*,Li Zhenhua,Chen Weixiang,Xu Zhude,Li Wenzhu,Chen Maohui,You Jinkua,Lin Zugeng
Author NameAffiliationE-mail
Wu Guotao Department of Physic, Zhejiang University, Hangzhou 310027; Department of Chemistry, Xiamen University, Xiamen 361005  
Wang Miao* Department of Physic, Zhejiang University, Hangzhou 310027 miaowang@css.zju.edu.cn 
Li Zhenhua Department of Mechanics, Zhejiang University, Hangzhou 310027  
Chen Weixiang Department of Chemistry, Zhejiang University, Hangzhou 310027  
Xu Zhude Department of Chemistry, Zhejiang University, Hangzhou 310027  
Li Wenzhu Department of Physic, Zhejiang University, Hangzhou 310027  
Chen Maohui Department of Chemistry, Zhejiang University, Hangzhou 310027  
You Jinkua Department of Chemistry, Xiamen University, Xiamen 361005  
Lin Zugeng Department of Chemistry, Xiamen University, Xiamen 361005  
Abstract:
Segmented carbon nanofibers were prepared by pyrolysis of acetylene on foam Ni at 600 and 700℃ in a fixed bed flowed-reactor. The morphology, microstructure and lithium insertion properties of these carbon nanofibers were investigated by TEM, XRD, Raman and electrochemical methods. Through TEM observations, it was found that this kind of carbon nanofibers was composed of lens-like segments with nearly equal separation stacking along the nanofiber axis. When the reaction temperature was 600℃, segmented carbon nanofibers were the major production. However, when the reaction temperature increased to 700℃, the content of segmented carbon filaments decreased and their diameter became smaller. The crystallite size d002 and Lc were determined by the 002 carbon Bragg peak of XRD patterns using the Bragg and Scherrer formulas. The intensity ratios of the 1350 cm-1line and the 1580 cm-1 line (R=ID/IG) was used to evaluate the La value, which was inversely proportional to the effective crystallite size in the direction of the graphite plane (La). With the reaction temperature increased, the d002 value decreased, La and Lc values increased, which indicated the degree of crystallinity increased. Segmented carbon nanofibers were used as positive electrodes of C/Li cells. The first charge capacities of C/Li cells were 480 and 300 mAh/g for samples produced at 600 and 700℃, respectively. The samples at 600℃showed capacities higher than the theoretical value of graphite, which was attributed to accommodation of more lithium at the edge of graphene layers and on the surface of graphene layers according to the mechanisms of lithium insertion in carbons prepared by low-temperature pyrolysis of hydrocarbons. As confirmed by the XRD and Raman spectra, the samples at 700℃ had larger La and Lc, which led to the capacity decreasing.
Key words:  Carbon nanofibers, Chemical vapor deposition, Li-ion battery, Negative electrode materials
FundProject:国家自然科学基金(60271009)、浙江省自然科学基金(501109, 200053)资助项目.
竹节状纳米碳纤维的制备及嵌锂性能研究
吴国涛,王淼*,李振华,陈卫祥,徐铸德,李文铸,陈茂惠,尤金跨,林祖赓
摘要:
以泡沫镍为催化剂,在600和700℃下,以CVD法热解乙炔气体制备大量的纳米碳纤维.随着制备温度增加,纳米碳纤维直径变小,竹节状含量减少, d002值减小,微晶片层平面Lc和La值增大,碳材料的可逆容量则下降.分别用透射电镜、 X射线衍射和拉曼光谱观察和测定了纳米碳纤维的形貌、微结构,发现在不同条件下生长的纳米碳纤维有不同的形貌和结构.对纳米碳纤维的电化学嵌锂性能的研究表明,纳米碳纤维的结构对其电化学嵌锂容量和充放电循环寿命起重要影响,制备温度越低,纳米碳纤维的石墨化程度越差,可逆嵌锂容量相应要高一些.
关键词:  碳纤维  化学气相沉积  锂离子电池  负极材料
DOI:10.1088/1674-0068/16/4/299-302
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