School of Metallurgy and Environment, Central South University , Changsha, 410083, P.R. China.
ACS Appl Mater Interfaces. 2018 Jan 31;10(4):3590-3595. doi: 10.1021/acsami.7b16402. Epub 2018 Jan 22.
A novel cathode material, carbon nanotube (CNT)-decorated NaV(PO) (NVP) microspheres, was designed and synthesized via spray-drying and carbothermal reduction methods. The microspheres were covered and embedded by CNTs, the surfaces of which were also covered by amorphous carbon layers. Thus, a carbon network composed of CNTs and amorphous carbon layers formed in the materials. The polarization of a 10 wt % CNT-decorated NVP (NVP/C10) electrode was much less compared with that of the electrode with pristine NVP without CNTs. The capacity of the NVP/C10 electrode only decreased from 103.2 to 76.2 mAh g when the current rates increased from 0.2 to 60 C. Even when cycled at a rate of 20 C, the initial discharge capacity of the NVP/C10 electrode was as high as 91.2 mAh g, and the discharge capacity was 76.9 mAh g after 150 cycles. The charge-transfer resistance and ohmic resistance became smaller because of CNT decorating. Meanwhile, the addition of CNTs can tune the size of the NVP particles and increase the contact area between NVP and the electrolyte. Consequently, the resulted NVP had a larger sodium ion diffusion coefficient than that of the pristine NVP.
通过喷雾干燥和碳热还原法设计并合成了一种新型阴极材料，即碳纳米管（CNT）修饰的 NaV(PO)（NVP）微球。微球被 CNT 覆盖和嵌入，其表面也被无定形碳层覆盖。因此，在材料中形成了由 CNT 和无定形碳层组成的碳网络。与没有 CNT 的原始 NVP 电极相比，10wt%CNT 修饰的 NVP（NVP/C10）电极的极化要小得多。当电流密度从 0.2 增加到 60 C 时，NVP/C10 电极的容量仅从 103.2 下降到 76.2 mAh g。即使以 20 C 的速率循环，NVP/C10 电极的初始放电容量也高达 91.2 mAh g，经过 150 次循环后，放电容量为 76.9 mAh g。由于 CNT 的修饰，电荷转移电阻和欧姆电阻变小。同时，CNT 的添加可以调整 NVP 颗粒的尺寸并增加 NVP 与电解质之间的接触面积。因此，得到的 NVP 的钠离子扩散系数比原始 NVP 大。
