Supporting Information

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1 Supporting Information Flexible Solid-State Supercapacitor Based on a Metal-Organic Framework Interwoven by Electrochemically-Deposited PANI Lu Wang,, Xiao Feng,, Lantian Ren, Qiuhan Piao, Jieqiang Zhong, Yuanbo Wang, Haiwei Li, Yifa Chen, and Bo Wang*, Key Laboratory of Cluster Science, Ministry of Education of China, School of Chemistry, Beijing Institute of Technology, 5 South Zhongguancun Street, Beijing , P. R. China School of Chemical Engineering and Technology, Tianjin University, 92 Weijin Ave., Tianjin , P. R. China These authors contributed equally Contents Section A. Materials and methods Section B. Experimental section Section C. Supplementary spectra (Figure S1-S9) Section D. Supporting references! S1

2 Section A. Materials and methods Materials: All reagents and starting materials were obtained commercially and were used as received without any further purification, except aniline, which was distilled under reduced pressure before use. Co(NO 3 ) 2 6H 2 O was purchased from Sinopharm Chemical Reagent Co. Ltd. 2-Methylimidazole and KCl (extra pure) were purchased from J&K Chemical Co. N-methyl pyrrolidinone (NMP), 98% H 2 SO 4 and ethanol were purchased from Beijing Chemical Works. Carbon cloth was purchased from CeTech (Taiwan). Deionized (DI) water was used throughout all the experiments. The rated voltage of red light-emitting-diode (LED) is 2.5 V. Powder X-ray diffraction (PXRD) pattern was analyzed with monochromatized Cu-Kα (λ = Å) incident radiation by a D8 Advance Bruker powder diffractometer operating at 40 kv voltage and 50 ma current. Field-emission scanning electron microscopy (FE-SEM) was performed on a JEOL model JSM-7500 F operating at an accelerating voltage of 5.0 kv. The electrochemical characteristics were evaluated using an electrochemical workstation (CHI 760E: CH Instrumental Inc.). Nitrogen sorption isotherms were measured at 77 K on a Quantachrome Instrument ASiQMVH002-5 after pretreatment by heating the samples under vacuum at 120 C for 6 h. X-ray photoelectron spectroscopy (XPS) was performed on the Thermo Scientific ESCALab 250Xi using 200 W monochromated Al Kα radiation. The 500 µm X-ray spot was used for XPS analysis. Typically the hydrocarbon C1s line at ev from adventitious carbon is used for energy referencing. All of the electrochemical performances of PANI-ZIF-67-CC and ZIF-67-CC electrode were studied in a three-electrode cell in 3 M KCl electrolyte, with Ag/AgCl and Pt plate as the reference electrode and counter electrode, respectively. The Nyquist plots of ZIF-67-CC and PANI-ZIF-67-CC was studied in a frequency range of 10 mhz to 100 khz at an open circuit potential of 10 mv. Calculation of specific capacitance derived from CV curves: In general, gravimetric capacitance is calculated using the following equation C = 2 ΔQ / (ΔV m) (1) Where ΔQ is the charge integrated from the whole voltage range, ΔV is the whole voltage difference, and m is the mass of activated material on an electrode. 1 As for areal capacitance, equation (1) can be changed to the following equation: C = 2 ΔQ / (ΔV S) (2)! S2

3 Where S is the apparent area of activated material. ΔQ = I t (3) Where I is the current and t is the time. Based on the CV curves, equation (3) can be modified to the following equation: ΔQ = IdV/v (4) So, according to equation (2) and (4), the areal capacitance derived from CV curves can be calculated using the following equation: C = 2 ( IdV) / (ν S ΔV) (5) The specific capacitance of solid-state supercapacitor derived form galvanostatic charge/discharge curves was calculated according to the following equation: C = 2I s V dt V f V 2 V i! Where I s is the discharge current density, t is the discharging time, V f = 0, V i = 1 V. The voltage window square takes absolute value. The numerator was calculated by integrating the current area of discharging process. 2 The energy density (E) and power density (P) were calculated from the following equations: E = C stack (ΔV) 2 /(2 3600), P = (ΔV) 2 /4RV. E is the specific energy density in Wh cm -3. P is the specific power density (W cm -3 ). V is volume (cm -3 ) of device, which is calculated from the total volume of device (including the active material, carbon cloth substrate and the gel electrolyte separator).! is operating window voltage window in volt (obtained from the discharge curve excluding the IR drop). The internal resistance of the device (R) was calculated from the IR drop. 3! S3

4 Section B. Experimental section Synthesis of ZIF-67: ZIF-67 nanocrystals were synthesized via a hydrothermal process reported previously. 4 Briefly, 0.9 g cobalt nitrate hexahydrate was dissolved in 6 ml of deionized (DI) water; then 11 g 2-methylimidazole (Hmim) was dissolved in 40 ml of DI water. Those two solutions were mixed (Co 2+ :Hmim:H 2 O = 1:58:1100) and stirred for 6 h at room temperature, then the resulting purple precipitates were collected by centrifuging, washed with water and ethanol subsequently for 3 times, and finally dried under vacuum at 80 C for 24 h. Fabrication of ZIF-67-CC: ZIF-67 samples (70 wt%) as the active material, Super P (20 wt%) as the conducting agent and poly (vinylidene fluoride) (10 wt%) as a binder were mixed in N-methyl pyrrolidinone (NMP) solution to form slurry. After that, the resulting paste was cast onto a piece of carbon cloth (1 2 cm 2 ) and dried under vacuum at 120 C for 12 h. Typically, about 7 mg ZIF-67 was coated on a 1 2 cm 2 carbon cloth. Fabrication of PANI-ZIF-67: PANI was synthesized via an electrochemical process reported previously. 5 In a typical procedure, the ZIF-67-CC was used as a working electrode. Potentiodynamically synthesis of polyaniline was performed in 3 M KCl solutions containing 0.1 M aniline, by the cycling of the potential for 75 cycles between -0.2 and 1.0 V versus Ag/AgCl at a 10 mv s -1 scan rate at 25 C. The resultant PANI-ZIF-67-CC was washed by DI water for several times and dried at 80 C. Typically, about 1.0 mg PANI was coated on a 1 2 cm 2 carbon cloth. The mass of PANI was calculated based on the mass difference before and after PANI deposition. The mass of MOF was calculated based on the mass difference before and after MOF coating. During the process, we measured the weight through a balance (METTLER TOLEDO, ME104) with precision of 0.1 mg. Moreover, to prevent the random error, we prepared a batch of samples and measured several times of each sample in parallel. Then we calculated the mean value and obtained high consistency throughout the experiments.! S4

5 Fabrication of all-solid state flexible supercapacitor: The gel electrolyte was prepared as follow. PVA (1799, Aladdin Chemicals) and H 2 SO 4 (analytical grade) were used as received. 1.5 g PVA was dissolved in 10 ml 1.0 M H 2 SO 4 water with stirring at 85 C under vigorous stirring until the solution became clear. The resulting gel was poured onto a polytetrafluoroethylene plate and dried in air. After evaporation of the excess water at room temperature, the jelly-like gel was solidified and it could be peeled off. The gel electrolyte was then cut into pieces matching the size of the electrodes. The symmetrical SSC device was fabricated by sandwiching the self-supporting solidified gel (serving as a separator and the electrolyte) with two pieces of identical PANI-ZIF-67-CC electrodes.! S5

6 Section C. Supplementary spectra (Figure S1-S9) Figure S1. SEM image of as-synthesized ZIF-67 nanoparticles.! S6

7 Figure S2. Cyclic voltammograms of electropolymerization process of aniline on ZIF-67-CC.! S7

8 Figure S3. SEM images of the carbon cloth fibers (a) after coating with ZIF-67 and (b) after electropolymerization of aniline.! S8

9 Figure S4. Powder X-ray diffraction patterns of simulated ZIF-67, as-synthesized ZIF-67, ZIF-67-CC, PANI-ZIF-67-CC before C/D and PANI-ZIF-67-CC after C/D. C/D represents for charge/discharge.! S9

10 Figure S5. N 2 adsorption/desorption isotherms of as-synthesized ZIF-67, inset: pore size distribution of as-synthesized ZIF-67. The BET surface area of as-synthesized ZIF-67 is 1717 m 2 g -1. Correlation coefficient r is and C constant is The pore width distribution is calculated based on DFT method; Calc. Model is N 2 at 77 K on carbon (slit/cylindr. pores, QSDFT adsorption branch).! S10

11 Figure S6. (a) N 2 adsorption/desorption isotherms of ZIF-67-CC, (b) pore size distribution of ZIF-67-CC, (c) N 2 adsorption/desorption isotherms of PANI-ZIF-67-CC, (d) pore size distribution of PANI-ZIF-67-CC. For ZIF-67-CC: the BET surface area is 450 m 2 g -1 ; correlation coefficient r is and C constant is ; the pore width distribution is calculated based on DFT method; Calc. Model is N2 at 77 K on carbon (slit/cylindr. pores, QSDFT adsorption branch). For PANI-ZIF-67-CC: the BET surface area of is 73 m 2 g -1 ; correlation coefficient r is and C constant is 4.467; the pore width distribution is calculated based on DFT method; Calc. Model is N2 at 77 K on carbon (cylindr. pores, NLDFT equilibrium model).! S11

12 Figure S7. N 1s XPS core-level spectra of the (a) PANI-ZIF-67 and (b) ZIF-67.! S12

13 Figure S8. Equivalent circuit of ZIF-67 and PANI-ZIF-67. R s is the equivalent internal resistance, including resistance of the electrolyte and the internal resistance of the electrode. C DL is double-layer capacitance, W o is the finite-length Warburg diffusion element, R CT is charge transfer resistance, and C F is the faradic capacitance. 6! S13

14 Figure S9. Cyclic votammograms collected of (a) untreated carbon cloth electrode at the scan rate of 0.01 V s -1 in 3 M KCl, (b) ZIF-67-CC electrode at the scan rate of 0.01 V s -1 in 3 M KCl, and (c) PANI-CC electrode at different scan rate in 3 M KCl. The capacitance of the untreated carbon cloth is very low and can be neglected in this system. ZIF-67-CC has a capacitance of 1.47 mf cm -2, while PANI-CC achieved the maximum areal capacitance of 727 mf cm -2. (d) Calculated areal capacitance of PANI-ZIF-67-CC plotted as a function of scan rate.! S14

15 Table S1. Typical results of electrode areal capacitance obtained from flexible solid-state supercapacitors 7 Specific Electrolyte Scan Configuration Type of electrode capacitance rate/current Ref. (mf cm -2 ) density Graphene M H 2 SO 4 1 A g -1 two-electrode 7a graphene-cellulose paper 81 1 M H 2 SO 4 1 mv s -1 two-electrode 7b CNTs/bacterial nano 18.8 [EMIM][N 100 mv s -1 two-electrode 7c Tf 2 ] Carbon nanopartcle/mno M 5 mv s -1 three-electrode 7d Na 2 SO 4 VN/CNTs M 1.1 ma cm 2 three-electrode 7e Na 2 SO 4 TiO M 10 mv s -1 three-electrode 7f Na 2 SO 4 Co-Al LDH-NS/GO 7 1 M KOH 5 mv s -1 three-electrode 7g ZnO@C@MnO M 1 ma cm 2 three-electrode 7h Na 2 SO 4 ZnO NWs M KNO mv s -1 two-electrode 7i VS 2 -micro 4.7 BMIMBF 4 two-electrode 7j PPy/nanoporous gold 1.8 HClO mv s -1 two-electrode 7k PANI-NWs/CC M H 2 SO A g -1 three-electrode 7l PANI/Au/paper M H 2 SO 4 1 ma cm 2 three-electrode 7m Activated carbon cloth 88 1 M H 2 SO 4 10 mv s -1 three-electrode 7n PANI-CC M KCl 10 mv s -1 three-electrode * ZIF-67-CC M KCl 10 mv s -1 three-electrode * PANI-ZIF-67-CC M KCl 10 mv s -1 three-electrode ** * Control experiment ** This work! S15

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