Supporting Information

Transcription

1 Supporting Information Extremely Stable Polypyrrole Achieved via Molecular Ordering for Highly Flexible Supercapacitors Yan Huang, Minshen Zhu, Zengxia Pei, Yang Huang, Huiyuan Geng, and Chunyi Zhi *,, Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Hong Kong, China. State Key Laboratory of Advance Welding and Joining, Harbin Institute of Technology, Harbin , China Shenzhen Research Institute, City University of Hong Kong, Shenzhen , China S-1

2 Method S1. Physiochemical characterization of the supercapacitor. The microstructure and morphology of electrodes were characterized by scanning electron microscope (SEM) (JEOL JSM-6335F) with an acceleration voltage of 5 kv. Raman spectroscopy spectra were obtained by RENISHAW Raman microscope with an excitation wavelength of 633 nm. X-ray diffraction studies were performed on a Philips X'Pert High Resolution Materials Research Diffractometer using Cu Kα radiation (λ = 1.54 Å). In-situ TEM (JEOL 3000F, Nanofactory TEM sample holder equipped with STM tip) was utilized to observe if there is any volumetric change during charging. FTIR (AVATAR 380) was used to get the spectra of the as-synthesized PPy. S-2

3 Figure S1. Various potential windows of CVs for e-ppy. When the potential window is higher than 0.6 V, CVs are distorted with the expansion of potential window. S-3

4 Figure S2. Cycling stability performance of supercapacitors made of e-ppy and c-ppy: capacitance retention at specific currents of 3 A/g and 5 A/g (e-ppy), 0.27 A/g and 0.33 A/g (c- PPy). When the charging current of e-ppy is 5 A/g, the cycle life is much shorter than that of e-ppy at 3 A/g. Similary, the lifetime of c-ppy at 0.33 A/g is shorter than at 0.27 A/g. Therefore, lower charging/discharging rate favors the cycling result. S-4

5 Figure S3. In situ TEM of c-ppy. a) Before the charging/discharging test. b) After repetitive charging/discharging tests in contact with ionic liquid (IL). After charging/discharging in contact with ionic liquid, some ionic liquid flows to side of c- PPy, filling some pores in the c-ppy and making the surface of c-ppy a bit smoother. However, there is no volumetric change observed for the much less stable c-ppy, indicating that supercapacitors are featured with longer cycling life-time in comparison to batteries. S-5

6 Figure S4. FTIR spectra of the as-synthesized e-ppy and c-ppy. Both polymers show very similar featured bands, suggesting their identical species of PPy. The broad band from 1320 to1210 cm -1 is attributed to C H or C N in-plane vibrations. The region at around 1120 cm -1 corresponds to the breathing vibration of the pyrrole ring. The peak at around 1080 cm -1 corresponds to the mode of in-plane deformation vibration of NH + 2 which forms on the PPy chains via protonation. The bands at 990 cm -1 and 950 cm -1 are attributed to C H and N H in-plane ring deformation vibration, and C C out-of-plane ring deformation vibration. S-6

7 Figure S5. Flexibility tests of supercapacitors made of e-ppy. a) CVs under various deformations. b) GCDs under various deformations. c) Capacitance ratio under various deformations. (Insets are photos of the supercapacitor under various deformations.) The e-ppy supercapacitors were subjected to a consecutive deformation test in the order of straight, bend, fold, twist, knot, and again straight. All CVs and GCDs overlay well under all deformations and long cycles. There is no capacitance loss during all these deformations. After being conformed to complex nonplanar surfaces in these deformations, the supercapactor recovers to the original straight shape with 100% performance preserved, revealing an excellent flexibility and recoverability. S-7

8 S-8

9 Figure S6. Flexibility cycling tests of supercapacitors made of e-ppy. a) CVs after various times of being bent. b) GCDs after various times of being bent. c) CVs after various times of being fold. d) GCDs after various times of being fold. e) CVs after various times of being twisted. f) GCDs after various times of being twisted. g) CVs after various times of being knotted. h) GCDs after various times of being knotted. i) Capacitance retention of the supercapacitor after each deformation. Cycling tests under these mechanical deformations were conducted. The e-ppy supercapacitor retains almost 100% of initial capacitance after 1000 times under all deformations. This is impressive in comparison with what most studies on flexible and wearable devices, in which usually the device flexibilities were only demonstrated by bending or slight twisting without cycling tests. S-9

10 Figure S7. Scalability tests of supercapacitors made of e-ppy. a) CVs of 1 to 3 supercapacitors in parallel. b) GCDs of 1 and 3 supercapacitors in parallel. c) Capacitances in parallel with repect to the number of devices. d) CVs of 1 to 3 supercapacitors in series. e) GCDs of 1 to 3 supercapacitors in series. f) Capacitances in series with repect to the number of devices. To meet voltage and current needs in practical applications, three e-ppy supercapacitors were assembled both in parallel (Fig. S7a-c) and in series (Fig. S7d-f). Compared with a single supercapacitor with an operating voltage of 0.6 V, the current and discharging time of the three supercapacitors connected in parallel increases by a factor of three. The overall capacitance of the parallel assembly linearly increases with the number of supercapacitors. Similarly, the threein-series assembly exhibits a three-fold wider charging/discharging voltage window (1.8 V) with a similar discharging time. The overall capacitance of the in-series assembly linearly decreases with the reciprocal of the number of supercapacitors, suggesting a good scalability. S-10

11 Table S1. Comparison of cycling stability of PPy-based supercapacitors. Ref. This study Electrode materials e-ppy Capacitance retention (%) Cycle number Specific current (A/g) S1 exfoliated graphite/e-ppy Scan Rate (V/s) S2 Carbon/e-PPy S3 c-ppy/mos S4 e-ppy S5 e-ppy/nanoporous gold S6 PPy ~ S7 PPy/PANI S8 e-ppy/reduced graphene oxide S9 e-ppy S10 e-ppy/carbon fiber paper S11 e-ppy/mno S12 c-ppy 14.3 c-ppy/carbon 45.4 S13 PPy S-11

12 Supplementary References S1. Song, Y.; Liu, T. Y.; Xu, X. X.; Feng, D. Y.; Li, Y.; Liu, X. X. Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors. Adv. Funct. Mater. 2015, 25, S2. Liu, T.; Finn, L.; Yu, M.; Wang, H.; Zhai, T.; Lu, X.; Tong, Y.; Li, Y. Polyaniline and Polypyrrole Pseudocapacitor Electrodes with Excellent Cycling Stability. Nano Lett. 2014, 14, S3. Tang, H. J.; Wang, J. Y.; Yin, H. J.; Zhao, H. J.; Wang, D.; Tang, Z. Y. Growth of Polypyrrole Ultrathin Films on MoS 2 Monolayers as High-Performance Supercapacitor Electrodes. Adv. Mater. 2015, 27, S4. Zhao, C.; Wang, C. Y.; Yue, Z. L.; Shu, K. W.; Wallace, G. G. Intrinsically Stretchable Supercapacitors Composed of Polypyrrole Electrodes and Highly Stretchable Gel Electrolyte. ACS Appl. Mater.Interfaces 2013, 5, S5. Meng, F. H.; Ding, Y. Sub-Micrometer-Thick All-Solid-State Supercapacitors with High Power and Energy Densities. Adv. Mater. 2011, 23, S6. Hussain, A. M. P.; Kumar, A. Enhanced Electrochemical Stability of All-Polymer Redox Supercapacitors with Modified Polypyrrole Electrodes. J.Power Sources 2006, 161, S7. Clemente, A.; Panero, S.; Spila, E.; Scrosati, B. Solid-State, Polymer-Based, Redox Capacitors. Solid State Ion. 1996, 85, S8. Khoh, W. H.; Hong, J. D. Solid-State Asymmetric Supercapacitor Based on Manganese Dioxide/Reduced-Graphene Oxide and Polypyrrole/Reduced-Graphene Oxide in a Gel Electrolyte. Colloids Surf. A 2014, 456, S-12

13 S9. Zhao, C.; Wang, C. Y.; Gorkin, R.; Beirne, S.; Shu, K. W.; Wallace, G. G. Three Dimensional (3D) Printed Electrodes for Interdigitated Supercapacitors. Electrochem. Commun. 2014, 41, S10. Yang, C. Y.; Shen, J. L.; Wang, C. Y.; Fei, H. J.; Bao, H.; Wang, G. C. All-Solid-State Asymmetric Supercapacitor Based on Reduced Graphene Oxide/Carbon Nanotube and Carbon Fiber Paper/Polypyrrole Electrodes. J. Mater.Chem.A 2014, 2, S11. Tao, J. Y.; Liu, N. S.; Ma, W. Z.; Ding, L. W.; Li, L.Y.; Su, J.; Gao, Y. H. Solid-State High Performance Flexible Supercapacitors Based on Polypyrrole-MnO 2 -Carbon Fiber Hybrid Structure. Sci. Rep. 2013, 3:2286, 1-7. S12. An, H. F.; Wang, Y.; Wang, X. Y.; Zheng, L. P.; Wang, X. Y.; Yi, L. H.; Bai, L.; Zhang, X. Y. Polypyrrole/Carbon Aerogel Composite Materials for Supercapacitor. J. Power Sources 2010, 195, S13. Hussain, A. M. P.; Saikia, D.; Singh, F.; Avasthi, D. K.; Kumar, A. Effects of 160 MeV Ni 12+ Ion Irradiation on Polypyrrole Conducting Polymer Electrode Materials for All Polymer Redox Supercapacitor. Nucl. Instr. and Meth. in Phys. Res. B 2005, 240, S-13