Preparation of a carbon nanofiber/natural graphite composite and an evaluation of its electrochemical properties as an anode material for a Li-ion battery
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摘要: 制备一种炭纳米纤维-天然石墨复合材料，以改善作为锂离子电池阳极材料的天然石墨的倍率性能。通过优化控制天然石墨上炭纳米纤维的生长量及其形状提高了天然石墨的循环性能和倍率性能。与天然石墨原料相比，炭纳米纤维天然石墨复合材料第一次放电容量达到了95%。炭纳米纤维的生长量被严格地控制在天然石墨质量的15%以下。研究发现：由于炭纳米纤维对充放电过程中阳极的体积膨胀和收缩程度的控制作用，天然石墨表面边位上生长的类似常青藤形的炭纳米纤维对倍率性能的提高最为有效。提出采用炭纳米纤维-天然石墨复合材料的原理结构模型解释重复充放电过程中电极的体积稳定性。通过在石墨表面上生长类常青藤形炭纳米纤维而使得SEI（固体电解质界面）变薄并减少了充放电过程中阳极的体积变化，因而提高了倍率性能。Abstract: A carbon nanofiber (CNF)/natural graphite (NG) composite was prepared to improve the rate capability of asreceived NG to be used as the anode material in a Li-ion battery. Optimum control over both the amount and shape of the CNFs to enable their growth on NG remarkably improved the cycle performance and rate capability of the as-received NG. The first-cycle discharge capacity of the CNF/NG composite was 95% of that of the asreceived NG. The amount of grown CNFs was controlled to be less than 15% of the as-received NG. CNF growth on the surface edges of NG in an ivy leaf shape proved to be most effective in improving the rate capability by controlling the extent of volumetric expansion and shrinkage occurring in the charge and discharge processes. Schematic structural models of the as-received NG and CNF/NG composite were proposed to account for the volumetric stability of the electrode in repeated charge-discharge processes. The improved rate capability is ascribed to the thin solid electrolyte interphase and reduced volumetric change of the anode in the charge/discharge processes, both of which are achieved by growing ivy-like CNFs over the graphite surface
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Key words:
- Natural graphite /
- Li-ion battery /
- Carbon nanofiber /
- Rate capability /
- Volumetric stability
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