Supporting Information

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1 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 2018 Supporting Information Interweaving Metal-organic Frameworks Templated Co-Ni Layered Double Hydroxide Nanocages with Nanocellulose and Carbon Nanotubes to Make Flexible and Foldable Electrodes for Energy Storage Device Chao Xu* [a,b], Xueying Kong [a,b], Shengyang Zhou [b], Bing Zheng* [a], Fengwei Huo [a], Maria Strømme* [b] a. Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing , China. E- mail: b. Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Uppsala SE-75121, Sweden. Experimental Section Materials: Cladophora cellulose (CC) powder was provided by FMC Biopolymer (Philadelphia, USA). Other chemicals and solvents were purchased from Sigma-Aldrich and used without further purification. Synthesis of ZIF-67. The ZIF-67 nanoparticles were prepared as follows: cobalt nitrate hexahydrate (3.0 mmol, g, 99 % purity) was dissolved in 30 ml of methanol. Separately, 2-methylimidazole (24.0 mmol, g, 99 % purity) was dissolved in 20 ml of methanol. Then, the two solutions were mixed and the mixture was stirred for 3 minutes. The mixture was kept undisturbed for 12 hours at room temperature. After that, the obtained purple precipitates were collected and washed several time with methanol, and dried at 70 for 12 hours. Synthesis of ZIF-CC-CNT. Cladophora cellulose (5 mg) and multi-wall carbon nanotubes (15 mg, >98 % carbon basis) were dispersed in water (30 ml) using a high-energy ultrasonicator for 20 minutes. A suspension of ZIF-67 nanocrystals (10 mg) in 2 ml of ethanol was subsequently added to the above dispersion followed by ultrasonic dispersion for additional 2 minutes. The mixture was collected on a Durapore PVDF membrane filter (pore size: 0.45 μm, diameter: 9 cm) and thoroughly washed with water and methanol. After drying the composite 1

2 at 70 for 12 hours, a freestanding ZIF-CC-CNT nanosheet (thickness: 9 μm, areal density: mg cm 2 of ZIF) was obtained. To prepare thicker ZIF-CC-CNT nanosheets with higher areal densities, formula of 30 mg ZIF-67/15 mg CC/45mg CNT and 90 mg ZIF-67/45 mg CC/135 mg CNT were applied. Synthesis of LDH-CC-CNT. The as-prepared ZIF-CC-CNT nanosheet was immersed in a solution of nickel nitrate hexahydrate (98.5 % purity) in ethanol at 75 for 3 hours, where the molar ratio of ZIF-67:Ni(NO3)2 6H2O was 1:2. The obtained nanosheet was thoroughly washed by ethanol and dried at 70 for 12 hours, denoted as LDH-CC-CNT. Preparation of CC-CNT. A similar procedure as for preparing ZIF-CC-CNT was employed to make CC-CNT nanosheets; by filtering dispersions of 5 mg CC/15 mg CNT, 15 mg CC/45 mg CNT, and 45 mg CC/135 mg CNT in water, denoted as CC-CNT-1, CC-CNT-2, and CC-CNT- 3, respectively. Preparation of electrodes: Freestanding LDH-CC-CNT nanosheets (1 cm 2 cm) were pressed onto graphite paper current collectors (1 cm 2 cm) at a pressure of 150 MPa. The compact composite was denoted as LDH-CC-CNT. CC-CNT electrodes were prepared in the same manner. To prepare LDH-PVDF-CNT electrodes for the comparative study, the mixture of LDH nanocage, polyvinylidene fluoride, and CNT with the mass ratio 8:1:1 was ground carefully to form a slurry, and it was coated onto a graphite paper current collector and dried at 75 for 24 hours. Electrochemical study on electrodes: the electrochemical analyses were carried out in a conventional three-electrode set-up in a 1 M KOH electrolyte, with an Hg/HgO electrode and a platinum wire as the reference electrode and counter electrode, respectively. Cyclic voltammetry (CV) and chronopotentiometry (CP) were performed with an Autolab/GPES instrument (ECO Chemie, The Netherlands) at room temperature. The Electrochemical impedance spectroscopy (EIS) measurements were carried out on a CH Instruments 660D 2

3 potentiostat (CH Instruments, Inc., USA). The frequency was varied between 100 khz and 0.01 Hz with an ac amplitude of 5 mv. The gravimetric capacitance (Cg) of LDH was calculated from CV curves of LDH-CC-CNT and LDH-PVDF-CNT electrodes using the following equations: Cg = 2 ΔQ / (ΔV m). (1) ΔV is the voltage window, m is the mass of LDH in the electrode, ΔQ is the integrated charge from the entire voltage range, calculated from the CV curves using the following equation: ΔQ = I t = IdV/ν. (2) Here I is the current, t is the time, and ν is the scan rate. To calculate the capacitance of LDH in LDH-CC-CNT electrodes, the contribution of CC-CNT for charge storage was deducted. The areal capacitance (Ca) of the LDH-CC-CNT electrodes were calculated from galvanostatic charge-discharge (GCD) curves using the following equation: Ca = I Δt / (S ΔV), (3) where I is the current density, t is the discharge time, V is the voltage range, and S is the area of the entire electrode. Fabrication and electrochemical study of the all-solid-state hybrid energy storage device (ESD) LDH-CC-CNT//CC-CNT: An LDH-CC-CNT electrode (1 cm 2 cm, mg 2 of LDH) and a CC-CNT electrode (1 cm 2 cm, mg cm 2 of CNT) were used as positive electrode and negative electrode, respectively. A piece of filter paper (1.2 cm 2.5 cm) was used as a separator. The KOH/PVA gel as solid electrolyte was prepared by mixing 1 g PVA, g KOH, and 10 ml DI water at 90 C under vigorous stirring. Then, the positive electrode, the negative electrode, and the separator were immersed in the PVA/KOH gel solution for 20 minutes. Subsequently, the separator was sandwiched between the positive and negative electrodes. The asymmetric device in a coffee-bag arrangement was made as previously described. CV and GCD measurements of the hybrid ESD were conducted in a two-electrode 3

4 system with an Autolab/GPES instrument (ECO Chemie, The Netherlands). The areal capacitance (Ca) of the hybrid ESD was calculated from GCD curves using equation (3), while the volumetric capacitance (Cv) was calculated using the following equations: Cv = I t / (V V), (4) where V is the volume of the entire device. Energy density (E) and power density (P) of the device were calculated according to the following equations: E = C ( V) 2 / 2 (5) P = E / t. (6) Here C is the areal capacitance or volumetric capacitance. Characterization: Powder X-ray diffraction (XRD) patterns were collected on a Bruker Focus D8 diffractometer. Scanning electron microscopy (SEM) images were recorded on a fieldemission scanning electron microscope (LEO 1530, Germany). Thermogravimetric analysis (TGA) curves were carried out on a TGA/SC 3+ instrument (Mettler Toledo, Switzerland) under N2 or air flow. X-ray photoelectron spectroscopy (XPS) spectra were recorded on a PHI Quantera II instrument (Physical Electronics, USA). N2 sorption measurements were carried out on a Micromeritics ASAP 2020 analyzer (USA). 4

5 Fig. S1 (a) TGA curves of pure Co-Ni LDH, Cladophora cellulose and CNTs. (b) TGA curves of ZIF-CC-CNT-1, -2 and -3 with different thicknesses, the calculated areal densities of ZIF- 67 are 0.305, 0.754, mg cm 1, respectively. (c) TGA curves of LDH-CC-CNT-1, -2 and -3 with different thicknesses, the calculated areal densities of LDH are 0.225, 0.481, mg cm 2, respectively. All TGA curves were recorded under a flow of air. 5

6 Fig. S2 (a) XRD patterns of ZIF-67 nanocrystals, CC-CNT, and ZIF-CC-CNT nanosheets with different areal densities of ZIF-67. (b) XRD patterns of CC-CNT, and LDH-CC-CNT nanosheets with different areal densities of LDH. 6

7 Fig. S3 EDS spectrum of a selected area on a LDH-CC-CNT nanosheet. Fig. S4 XPS survey spectrum of LDH-CC-CNT. 7

8 Fig. S5 (a) N2 sorption isotherms and (b) pore size distributions of CC, CNTs, and CC-CNT. (c) N2 sorption isotherms and (d) pore size distributions of ZIF-CC-CNT nanosheets with different areal densities of ZIF-67. (e) N2 sorption isotherms and (f) pore size distributions of LDH-CC-CNT nanosheets with different areal densities of LDH. The sorption isotherms were recorded at 77 K. The pore size distributions were calculated from the adsorption branches using density functional theory model. 8

9 Fig. S6 SEM image of (a) as synthesized ZIF-67 nanocrystals, (b) ZIF-CNTs, (c) ZIF-CC-CNT, (d) LDH-PVDF-CNT, and (e) LDH-CC-CNT. 9

10 Fig. S7 Plots of peak current (ip) vs. square root of the scan rate (ν 1/2 ) for LDH-CC-CNT electrodes with various LDH loadings. The peak current is well linearly fitted with the square root of the scan rate. 10

11 Fig. S8 (a) CV curves of an LDH-PVDF-CNT electrode at different scan rates. (b) A comparison of gravimetric capacitance of LDH in LDH-PVDF-CNT and LDH-CC-CNT (0.225 mg cm 2 of LDH) electrode. The values on the vertical axis in panel b are normalized with respect to the LDH content of the electrode. 11

12 Fig. S9 CV curves of LDH-CC-CNT electrodes with different areal densities (a) mg cm 2 of LDH, (b) mg cm 2 of LDH, (c) mg cm 2 of LDH and the corresponding (d) CC- CNT-1, (e) CC-CNT-2, and (f) CC-CNT-3 electrodes at various scan rates. Each LDH-CC- CNT electrode has the same contents of CC and CNTs as the corresponding CC-CNT electrode. By comparing the CV curves, the contribution of CC and CNTs to the capacitance in LDH-CC- CNT electrode can be evaluated. 12

13 Fig. S10 GCD curves of LDH-CC-CNT electrodes with different areal densities (a) mg cm 2 of LDH, (b) mg cm 2 of LDH, (c) mg cm 2 of LDH) and the corresponding (d) CC-CNT-1, (e) CC-CNT-2, and (f) CC-CNT-3 electrodes at various current densities. Each LDH-CC-CNT electrode has the same contents of CC and CNTs as the corresponding CC-CNT electrode. The contribution of LDH and CC-CNT to the areal capacitances of the entire electrodes (g) mg cm 2 of LDH, (h) mg cm 2 of LDH, (i) mg cm 2 of LDH calculated based on the discharge time of LDH-CC-CNT electrodes and the corresponding CC- CNT electrodes. 13

14 Fig. S11 CV curves of the assembled hybrid energy storage device of LDH-CC-CNT // CC- CNT at different scan rates. 14

15 Table S1. Comparison of areal capacitance, power and energy density for the flexible energy storage devices based on LDH-CC-CNT electrode and other reported electrodes Electrode Areal capacitance (mf cm -2 ) Current density (ma cm -2 ) Electrode Power density (mw cm -2 ) Energy density (mwh cm -2 ) ZIF-PPy ZIF-PPy NiCo-LDH NSs@Ag@carbon cloth NiCo-LDH NSs@Ag@carbon cloth MOF-MnOx NiCo-LDH NFAs@NSs/Ni fabric NiCo-LDH/CFC NiCo2S4@NiMn- LDH/GS PANI-ZIF-67-carbon cloth Ni(OH)2 fiber LDH/CC-CNT (This work) nmof LDH/CC-CNT (This work) ESD = energy storage device; CC = Cladophora cellulose; CNT = carbon nanotube; LDH = layered double hydroxide; PANI = polyaniline; PPy = polypyrrole; CFC = carbon fiber cloth; NFAs = nanoflake arrays; NSs = nanosheets; GS = graphene sponge. Reference: 1. X. Xu, J. Tang, H. Qian, S. Hou, Y. Bando, M. S. A. Hossain, L. Pan and Y. Yamauchi, ACS Appl. Mater. Interfaces, 2017, 9, S. C. Sekhar, G. Nagaraju, and J. S. Yu, Nano Energy, 2017, 36, Y.-Z. Zhang, T. Cheng, Y. Wang, W.-Y. Lai, H. Pang and W. Huang, Adv. Mater., 2016, 28, T. Wang, S. Zhang, X. Yan, M. Lyu, L. Wang, J. Bell and H. Wang, ACS Appl. Mater. Interfaces, 2017, 9, L. Wang, X. Feng, L. Ren, Q. Piao, J. Zhong, Y. Wang, H. Li, Y. Chen and B. Wang, J. Am.Chem. Soc., 2015, 137, Goli Nagaraju, S. Chandra Sekhar, L. Krishna Bharat,and Jae Su Yu, ACS Nano, 2017, 11, H. Wan, J. Liu, Y. Ruan, L. Lv, L. Peng, X. Ji, L. Miao and J. Jiang, ACS Appl. Mater. Interfaces, 2015, 7, X. Dong, Z. Guo, Y. Song, M. Hou, J. Wang, Y. Wang and Y. Xia, Adv. Funct. Mater., 2014, 24, K. M. Choi, H. M. Jeong, J. H. Park, Y.-B. Zhang, J. K. Kang and O. M. Yaghi, ACS Nano, 2014, 8,