The growth direction, morphology and microstructure of carbon nanotubes (CNTs) play key roles for their potential applications in electronic and energy storage devices. However, effective synthesis of CNTs in high crystallinity and desired microstructure still remains a tremendous challenge. Here we introduce an electric field for controlling the microstructure formation of CNTs. It reveals that the electric field not only make CNTs aligned parallel but also improve the density of CNTs. Especially, the microstructures of CNTs gradually change under electrical field. That is, graphite sheets are transformed from the “herringbone” structure to a highly crystalline structure, facilitating the transportation of electrons. Due to the improved aligned growth direction, high density and highly crystalline microstructure, the electrochemical performance of CNTs is greatly improved. When the CNTs are applied in supercapacitors, they present a high specific capacitance of 237 F/g, three times higher than that of the CNTs prepared without electrical field. Such microstructure modulation of CNTs by electric field would help to construct high performance electronic and energy storage devices.

碳纳米管（CNT）的生长方向，形态和微结构对其在电子和能量存储设备中的潜在应用起着关键作用。然而，以高结晶度和所需的微结构有效地合成CNT仍然是巨大的挑战。在这里，我们介绍了一种用于控制CNT微观结构形成的电场。结果表明，电场不仅使碳纳米管平行排列，而且提高了碳纳米管的密度。特别是，碳纳米管的微观结构在电场作用下逐渐变化。即，石墨片从“人字形”结构转变为高度结晶的结构，从而促进了电子的传输。由于改善了取向生长方向，高密度和高度结晶的微观结构，碳纳米管的电化学性能大大提高。当将CNT用于超级电容器中时，它们呈现出237 F / g的高比电容，是没有电场制备的CNT的三倍。通过电场的碳纳米管的这种微结构调制将有助于构造高性能的电子和能量存储设备。