水热-溶胶-凝胶法合成多壁碳纳米管-Na3V2（PO4）3复合物及其作为锂离子电池正极材料的性能

采用水热和溶胶-凝胶相结合的方法，制备了具有良好电化学性能的新型多壁碳纳米管-Na₃V₂（PO₄）₃（MWCNT-NVP）复合材料（MWCNT的质量分数为8.74%）. 通过场发射扫描电子显微镜表征可知，MWCNT分散在NVP纳米颗粒之间，并起到“电子导电线”的作用. 与纯Na₃V₂（PO₄）₃相比，MWCNT-NVP具有更高的比容量和更优异的循环性能. 在0.2C（35.2 mA·g^-1）的电流密度下，3.0-4.5 V的电压范围内，MWCNT-NVP的初始比容量为82.2 mAh·g^-1. 循环100次以后，比容量为72.3 mAh·g^-1. 在1.0-3.0 V充放电时，MWCNT-NVP的初始容量为100.6 mAh·g^-1. 100次循环以后，其容量保持率高达90%. 同时，交流阻抗测试表明，由于MWCNT的存在，MWCNT-NVP的导电性有了显著的提高. 以上结果表明，MWCNT-NVP是一种良好的锂离子电池电极材料.

Hydrothermal Sol-Gel Method for the Synthesis of a Multiwalled Carbon Nanotube-Na3V2(PO4)3 Composite as a Novel Electrode Material for Lithium-Ion Batteries

We report the synthesis of a novel multiwalled carbon nanotube-Na₃V₂(PO₄)₃ (MWCNT-NVP) composite with excellent electrochemical performance. The composite material was prepared by a hydrothermal process combined with a sol-gel method. The MWCNT-NVP composite consists of Na₃V₂(PO₄)₃ (NVP) and a small amount of multiwalled carbon nanotubes (MWCNTs) (8.74%(w)). The MWCNTs were successfully dispersed between the NVP nanoparticles, which was confirmed by field-emission scanning electron microscopy, and served as a kind of "electronic wire". Electrochemical measurements show that the MWCNTNVP composite has enhanced capacity and cycling performance compared with pristine Na₃V₂(PO₄)₃. At a current rate of 0.2C (35.2 mA·g^-1), the initial reversible discharge capacity of the MWCNT-NVP was 82.2 mAh·g^-1, and 72.3 mAh·g^-1 was maintained after 100 cycles when cycled between 3.0 and 4.5 V. Good cycling performance was also observed when cycling between 1.0 and 3.0 V. The initial reversible capacity was 100.6 mAh·g^-1 and the capacity retention was 90% after 100 cycles. Additionally, electrochemical AC impedance showed that the electronic conductivity of MWCNT-NVP was significantly improved in the presence of the MWCNTs. These results indicate that the MWCNT-NVP composite has outstanding properties, and is thus a promising alternative for lithium-ion batteries with relatively low lithium consumption.