In-situ growth of LiFePO4 nanocrystals on interconnected carbon nanotubes/mesoporous carbon nanosheets for high-performance lithium ion batteries
In-situ growth of LiFePO4 nanocrystals on interconnected carbon nanotubes/mesoporous carbon nanosheets for high-performance lithium ion batteries
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DOI：
10.1016/j.electacta.2014.12.028
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发表时间：
2015-01
影响因子：
6.6
通讯作者：
Ruofei Wu;G. Xia;S. Shen;F. Zhu;F. Jiang;Junliang Zhang
中科院分区：
文献类型：
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作者：
Ruofei Wu;G. Xia;S. Shen;F. Zhu;F. Jiang;Junliang Zhang
采用软模板法在互连的碳纳米管/介孔碳纳米片（LFP@CNTs/CNSs）上原位生长磷酸铁锂（LiFePO 4）纳米晶体，该方法包括三嵌段共聚物、CNTs、甲阶酚醛树脂和LFP前体的多组分共组装，然后进行热处理。采用X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和N2吸附-脱附技术对材料的结构和形貌进行了表征。当用作锂离子电池的正极时，LFP@CNTs/CNSs复合材料表现出比仅用CNSs（命名为LFP/CNSs）或用CNTs（命名为LFP/CNTs）改性的样品更优异的上级倍率性能和循环稳定性。这主要是由于碳纳米管和碳纳米管的独特结构所引起的协同效应，形成了相互连接的导电网络，使电子和锂离子快速传输，从而显著改善了电极动力学。首先，纳米尺寸的LFP原位生长在CNT/CNSs框架上，其可以充当有效的基质以（i）抑制LFP在热处理过程中的尺寸生长和（ii）防止它们在循环期间聚集。其次，将CNT/CNSs骨架引入LFP电极中显著增加了复合材料的电子电导率，从而允许改善的高倍率充放电性能。最后，CNT/CNSs框架中的开放介孔性也为锂离子扩散到LFP提供了有效的传输途径。
Lithium ion phosphate (LiFePO4) nanocrystals are successfully in-situ grown on interconnected carbon nanotubes/mesoporous carbon nanosheets (designated as LFP@CNTs/CNSs) with a soft-templated method, which involves the multi-constituent co-assembly of a triblock copolymer, CNTs, resol and precursors of LFP followed by thermal treatment. X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy and N2adsorption-desorption techniques are used to characterize the structure and morphology of the as-synthesized materials. When used as the cathode of lithium ion batteries, the LFP@CNTs/CNSs composite exhibits superior rate capability and cycling stability, compared with the samples modified only with CNSs (designated as LFP/CNSs) or with CNTs (designated as LFP/CNTs). This is mainly attributed to the synergetic effect between CNTs and CNSs caused by their unique structure, which forms interconnected conductive network for fast transport of both electrons and lithium ions, and thus remarkably improves the electrode kinetics. Firstly, nano-sized LFP are in-situ grown on the CNTs/CNSs framework, which can serve as an effective matrix to (i) restrain the size growth of LFP during the thermal treatment process and (ii) prevent them from aggregating during cycling. Secondly, the incorporation of CNTs/CNSs framework into the LFP electrode significantly increases the electronic conductivity of the composite, and thus allow for improved high-rate charge-discharge performance. Finally, open mesoporosity in the CNTs/CNSs framework also provides an efficient transport pathway for lithium ions diffusion to LFP.