Supporting Information

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1 Supporting Information Hierarchical Porous N-doped Graphene Monoliths for Flexible Solid-State Supercapacitors with Excellent Cycle Stability Xiaoqian Wang, Yujia Ding, Fang Chen, Han Lu, Ning Zhang*, and Mingming Ma*, CAS Key Laboratory of Soft Matter Chemistry, ichem (Innovation Center of Chemistry for Energy Materials), Department of Chemistry, University of Science and Technology of China, Hefei, Anhui , China Department of Biology and Environmental Engineering, Hefei University, Hefei, Anhui , China Corresponding author s: S-1

2 1. Reagents and materials Natural graphite was purchased from Qingdao Graphite Company. Other chemical reagents were of analytical grade and purchased from Sinopharm Group Co., Ltd.. 2. Characterization methods The morphology of M-NGM was characterized by field-emission high-resolution transmission electron microscopy (FETEM, JEOL JEM-2100F), and SEM (JSM-6700F) at an acceleration voltage of 5 kv. The thickness of NG sheet was characterized by Cypher ES Environmental atomic force microscopy (AFM). The chemical structures of GO, NGM and M-NGM were analyzed by ATR-IR spectroscopy (Thermo scientific OMNIC Nicolet is5), X-ray powder diffraction (XRD, Rigaku D X-ray diffractometer with Cu Kα radiation (λ= Å)), and X- ray photoelectron spectra (XPS, Thermos ESCALAB 250 using Al Kα (hγ= ev) radiation exciting source). The Raman spectrums of NGM and M-NGM were measured by using LabRam HR instrument. The N 2 adsorption-desorption isotherms of M-NGM were performed at 77 K using ASAP2020M+C (Micromeritics), and the specific surface area was calculated from the BET plot of the N 2 adsorption isotherm. S-2

3 Figure S1. The schematic diagram of the M-NGM supercapacitor. Figure S2. The C 1s XPS spectra of graphene oxide. S-3

4 Figure S3. The XPS survey spectrum for NGM and M-NGM. S-4

5 Figure S4. The EDS mapping of M-NGM sample showing the elemental distribution of C, O and N. S-5

6 Figure S5. The AFM image of nitrogen doping graphene (NG) sheets. S-6

7 Figure S6. The Raman spectrum of M-NGM. S-7

8 Figure S7. (a, c, e) Cross-sectional SEM images of M-NGM with the thickness of ~360 µm. (b, d, f) Cross-sectional SEM images of M-NGM with the thickness of ~2 mm. S-8

9 Figure S8. (a) Nitrogen adsorption and desorption isotherms and (b) related pore size distribution of M-NGM. Figure S9. (a) An equivalent circuit. The equivalent circuit is used to fit the Nyquist spectrum data. (b)the raw impedance spectrum and fitting data of M-NGM. S-9

10 Figure S10. The variation of specific capacitance in different current densities at different mass loadings in 1.0 M H 2 SO 4. S-10

11 Figure S11. The GCD curves of M-NGM SC (2.46 mg cm -2 ) at different current densities ranging from 0.5 A g -1 to 10 A g -1 in PVA-H 2 SO 4 electrolyte. S-11

12 Figure S12. The electrochemical performance of M-NGM SCs with PVA-H 2 SO 4 electrolyte. (a) The cycle voltammetry curves (b) and the galvanostatic charge-discharge curves of M-NGM supercapacitor with a mass loading of 2.29 mg cm -2 measured in different scan rates and current densities. (c) The CV curves (d) and the GCD curves of M-NGM supercapacitor with a mass loading of 3.00 mg cm -2 measured in different scan rates and current densities. S-12

13 Figure S13. Two assembled M-NGM SCs connected in series to simultaneously light up the red LEDs. S-13

14 Figure S14. The GCD curves of the flexible M-NGM supercapacitor at different bending angles. S-14

15 Table S1. The elemental analysis results of GO, NGM and M-NGM. C wt% N wt% H wt% GO NGM M-NGM S-15

16 Table S2. The comparison of free-standing graphene supercapacitors electrochemical Samples Voltage (V) Discharge Rate (A g -1 ) Two-electrode capacitance (F g -1 ) Areal capacitance (mf cm - 2 ) Cycle stability Reference M-NGM ~100% (10000) This work performance. S-16

17 3D freezecasting of cellular graphene film 3D graphene hydrogel film % (10000) 91.6% (10000) HGF % (10000) 3 RGO film ma cm -2 / % (5000) 4 RGO film from leavening / / 5 FGHs / GO-GNP- SiO CF-MSP (based on the mass of entire device) 81.3 (based on the mass of entire device) / / 86% (10000) 95.5% (10000) 97.6% (10000) N,P-CHF / Stable (4000) 9 3DG / / Movie S1. The M-NGM SCs light up a red LED indicator. S-17

18 References (1) Shao, Y.; El Kady, M. F.; Lin, C. W.; Zhu, G.; Marsh, K. L.; Hwang, J. Y.; Zhang, Q.; Li, Y.; Wang, H.; Kaner, R. B. 3D Freeze Casting of Cellular Graphene Films for Ultrahigh Power Density Supercapacitors. Adv. Mater. 2016, 28, (2) Xu, Y.; Lin, Z.; Huang, X.; Liu, Y.; Huang, Y.; Duan, X. Flexible Solid-State Supercapacitors Based on Three-Dimensional Graphene Hydrogel Films. ACS Nano 2013, 7, (3) Xu, Y.; Lin, Z.; Zhong, X.; Huang, X.; Weiss, N. O.; Huang, Y.; Duan, X. Holey Graphene Frameworks for Highly Efficient Capacitive Energy Storage. Nat. Commun. 2014, 5, (4) Xiong, Z.; Liao, C.; Han, W.; Wang, X. Mechanically Tough Large Area Hierarchical Porous Graphene Films for High Performance Flexible Supercapacitor Applications. Adv. Mater. 2015, 27, (5) Niu, Z.; Chen, J.; Hng, H. H.; Ma, J.; Chen, X. A Leavening Strategy to Prepare Reduced Graphene Oxide Foams. Adv. Mater. 2012, 24, (6) Xu, Y.; Lin, Z.; Huang, X.; Wang, Y.; Huang, Y.; Duan, X. Functionalized Graphene Hydrogel Based High Performance Supercapacitors. Adv. Mater. 2013, 25, (7) Zhu, C.; Liu, T.; Qian, F.; Han, T. Y.-J.; Duoss, E. B.; Kuntz, J. D.; Spadaccini, C. M.; Worsley, M. A.; Li, Y. Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores. Nano Lett. 2016, 16, (8) Zhang, F.; Liu, T.; Li, M.; Yu, M.; Luo, Y.; Tong, Y.; Li, Y. Multi-Scale Pore Network Boosts Capacitance of Carbon Electrodes for Ultrafast Charging. Nano Lett. 2017, 17, (9) Chen, L. F.; Huang, Z. H.; Liang, H. W.; Gao, H. L.; Yu, S. H. Three Dimensional S-18

19 Heteroatom Doped Carbon Nanofiber Networks Derived from Bacterial Cellulose for Supercapacitors. Adv. Funct. Mater. 2014, 24, (10) Zhao, J.; Jiang, Y.; Fan, H.; Liu, M.; Zhuo, O.; Wang, X.; Wu, Q.; Yang, L.; Ma, Y.; Hu, Z. Porous 3D Few Layer Graphene Like Carbon for Ultrahigh Power Supercapacitors with Well Defined Structure-Performance Relationship. Adv. Mater S-19