Energy storage systems including supercapacitors and lithium ion batteries typically appear in a rigid plate which is unfavorable for many applications, especially in the fi elds of portable and highly integrated equipments which require small size, light weight, and high fl exibility. [1][2][3] As a result, fl exible supercapacitors and batteries mainly in a fi lm format have been widely investigated, while wire-shaped energy storage devices are rare. [ 4 , 5 ] However, compared with the conventional planar structure, a wire device can be easily woven into textiles or other structures to exhibit unique and promising applications. The limitation is originated from the much stricter requirement for the electrode such as a combined high fl exibility and electrochemical property in wire-shaped devices. [ 6 , 7 ] It remains challenging but becomes highly desired to obtain wire-shaped supercapacitors and batteries with high performances.On the other hand, due to the unique structure and remarkable mechanical and electrical properties, carbon nanotubes (CNTs) have been widely studied as electrode materials in conventional planar energy storage devices. [ 8 , 9 ] However, CNTs are generally made in a network format in which the produced charges had to cross a lot of boundaries with low effi ciencies. It is critically important to improve the charge transport in CNT materials. [8][9][10][11][12][13] Herein, we have developed wire-shaped micro-supercapacitors and micro-batteries with high performances by using aligned multi-walled carbon nanotube (MWCNT) fi bers as electrodes. The micro-supercapacitor wire was fabricated by twisting two aligned MWCNT fi bers and showed a mass specifi c capacitance of 13.31 F/g, area specifi c capacitance of 3.01 mF/cm 2 , or length specifi c capacitance of 0.015 mF/cm at 2 × 10 − 3 mA (1.67 A/g). The wire-shaped battery was produced by twisting an aligned MWCNT fi ber and a lithium wire which functioned as positive and negative electrodes, respectively. The specifi c capacity was calculated as 94.37 mAh/cm 3 or 174.40 mAh/g at 2 × 10 − 3 mA. The energy and power densities in both supercapacitors and batteries could be further greatly improved by incorporation of MnO 2 nanoparticles into MWCNT fi bers. For instance, the charge and discharge energy densities achieved 92.84 and 35.74 mWh/cm 3 while the charge and discharge power densities were 3.87 and 2.43 W/cm 3 at 2 × 10 − 3 mA in the wire-shaped micro-battery.Spinnable MWCNT arrays were fi rst synthesized by chemical vapor deposition, and aligned MWCNT fi bers could then be spun from the array with controlled diameters from 2 to 30 μ m and lengths up to 100 m. Figure S1a shows a typical scanning electron microscopy (SEM) image of MWCNT fi ber with uniform diameter of 20 μ m. Figure 1 a further shows that MWCNTs are highly aligned in the fi ber, which enables high tensile strengths up to 1.3 GPa and high electrical conductivities of 10 3 S/cm. Therefore, the MWCNT fi bers had been further used as electrodes to deposit MnO 2 on the MWCN...

A hollow graphene/conducting polymer composite fiber is created with high mechanical and electronic properties and used to fabricate novel fiber-shaped supercapacitors that display high energy densities and long life stability. The fiber supercapacitors can be woven into flexible powering textiles that are particularly promising for portable and wearable electronic devices.

Flexible and portable devices are a mainstream direction in modern electronics and related multidisciplinary fields. To this end, they are generally required to be stretchable to satisfy various substrates. [1,2] As a result, stretchable devices, such as electrochemical supercapacitors, [3][4][5][6] lithium-ion batteries, [7] organic solar cells, [8] organic light-emitting diodes, [9,10] field-effect transistors, [11] and artificial skin sensors [12] have been widely studied. However, these stretchable devices are made in a conventional planar format that has largely hindered their development. For the portable applications, the devices need to be lightweight and small, though it is difficult for them to be made into efficient microdevices. In particular, it is challenging or even impossible for them to be used in electronic circuits and textiles that are urgently required also in a wide variety of other fields, such as microelectronic applications.Recently, some attempts have been made to fabricate wire-shaped microdevices, such as electrochemical supercapacitors. They have been generally produced by twisting two fiber electrodes with electrolytes coated on the surface. [13][14][15][16][17][18][19] Several examples have been also successfully shown to make fiber-shaped supercapacitors with a coaxial structure. [20,21] Compared with their planar counterparts, the wire or fiber shape enables promising advantages such as being lightweight and woven into textiles. Although the wire and fiber-shaped supercapacitors are also flexible with high electrochemical performance, they are not stretchable, which is critically important for many applications. For instance, the resulting electronic textiles could easily break during the use if they were not stretchable.To the best of our knowledge, herein we have, for the first time, developed a novel family of highly stretchable, fibershaped high-performance supercapacitors. Aligned carbon nanotube (CNT) sheets that are sequentially wrapped on an elastic fiber serve as two electrodes. The use of aligned CNT sheets offers combined remarkable properties including high flexibility, tensile strength, electrical conductivity, and

No abstract

The advancement of modern electronic devices depends strongly on the highly efficient energy sources possessing high energy density and power density. In this regard, supercapacitors show great promise. Due to the unique hierarchical structure, excellent electrical and mechanical properties, and high specific surface area, carbon nanomaterials (particularly, carbon nanotubes, graphene, mesoporous carbon and their hybrids) have been widely investigated as efficient electrode materials in supercapacitors. This review article summarizes progress in high-performance supercapacitors based on carbon nanomaterials with an emphasis on the design and fabrication of electrode structures and elucidation of charge-storage mechanisms. Recent developments on carbon-based flexible and stretchable supercapacitors for various potential applications, including integrated energy sources, self-powered sensors and wearable electronics, are also discussed.