Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2016. Supporting Information for Adv. Energy Mater., DOI: 10.1002/aenm.201601814 Nitrogen-Doped Core-Sheath Carbon Nanotube Array for Highly Stretchable Supercapacitor Zhitao Zhang, Lie Wang, Yiming Li, Yuhang Wang, Jing Zhang, Guozhen Guan, Zhiyong Pan, Gengfeng Zheng, and Huisheng Peng*
Supporting Information Experimental Section Preparation of the original carbon nanotube array. The carbon nanotube (CNT) array was synthesized by chemical vapor deposition. A silicon wafer deposited with Fe (1.2 nm)/al 2 O 3 (3 nm) was used as catalyst. Ethylene (90 cm 3 min -1 ) was used as the carbon source, and a mixed gas of argon (400 cm 3 min -1 ) and hydrogen (30 cm 3 min -1 ) was performed as the carrier gas. The reaction was carried out at 740 ºC for 10 min. Preparation of the PVA fiber: After achieving the PVA solution, the PVA solution was injected into a heat-shrinkable tube, followed by curing at 40 C for 3 h. Finally, a PVA fiber was pulled out of the heat-shrinkable tube for the stress-strain test. Characterization. The structures were characterized by scanning electron microscopy (Hitachi, FE-SEM S-4800 operated at 1 kv), transmission electron microscopy (JEOL, JEM-2100F operated at 200 kv), and Raman spectroscopy (Renishaw in Via Reflex instrument with an excitation wavelength of 633 nm and laser power of 20 mw). X-ray photoelectron spectroscopy was recorded from an AXIS ULTRA DLD XPS System with MONO Al source. Galvanostatic charge-discharge characterizations and cyclic voltammograms were recorded from an electrochemical analyzer system (CHI 660D). The stretchability was tested by an HY0350 Table-top Universal Testing Instrument. S1
Figure S1. Schematic illustration to the structure of a highly stretchable supercapacitor. S2
Figure S2. SEM image of the original CNT. S3
Figure S3. TEM image of the original CNT. S4
Figure S4. TEM images of the original CNT (left) and NCNT (right). The green line indicates the boundary between the origin CNT wall and the re-grown N-doped layer. S5
Figure S5. TEM image of a CNT bundle grown with the N-doped layer. S6
Figure S6. Energy-dispersive X-ray spectroscopy images of the NCNT array. a) SEM image of the NCNT array. b) The dispersion of C element. c) The dispersion of N element. S7
Figure S7. SEM images of the stretchable supercapacitors. a, b) NCNT/PU film at low and high magnifications, respectively. c) NCNT/PU film after coat with PVA gel electrolyte. d) Cross-sectional image of a supercapacitor. S8
Figure S8. Stress-strain curve of a PVA fiber. S9
Figure S9. Photographs of an NCNT/PU film before (a) and after (b) bending, respectively. S10
Figure S10. SEM images of the NCNT/PU film before (a) and after (b) stretching for 1000 cycles at a strain of 200%. S11
Figure S11. Dependence of the variation of the electrical resistance on bending number. R 0 and R correspond to the electrical resistance before and after bending, respectively. S12
Figure S12. Dependence of electrical resistance on strain for the stretchable NCNT/PU film with re-growing times increased from 0 and 15 to 20 min. S13
Figure S13. Dependence of electrical resistance on strain for the stretchable NCNT/PU film at a re-growing time for 40 min. S14
Figure S14. Dependence of electrical resistance on stretched cycle number. R 0 and R correspond to the electrical resistances before and after stretching at a strain of 200%, respectively. S15
Figure S15. Dependence of specific capacitance on re-growing time for the highly stretchable supercapacitor. S16
Figure S16. SEM image of a CNT/PU film. S17
Figure S17. Electrochemical impendence spectroscopy (scatterplots) curves and the related fitted results (lines) of the stretchable supercapacitor with different re-growing times. S18
Figure S18. The equivalent circuit and fitted calculation values. S19
Figure S19. Dependence of specific capacitance on current density for the highly stretchable supercapacitor. S20
Figure S20. Photograph of the highly stretchable supercapacitor with the strain increased from 0 to 400%. S21
Figure S21. Dependence of the specific capacitance of the supercapacitor on bending cycle number. S22
Figure S22. The cross-sectional SEM image of contact interface between NCNT/PU film and PVA electrolyte after stretching for 1000 cycles at a strain of 200%. S23