Structural Directed Growth of Ultrathin Parallel Birnessite on

Structural Directed Growth of Ultrathin Parallel Birnessite on β-mno 2 for High-Performance Asymmetric Supercapacitors Shi Jin Zhu 1, Li Li 2, Jia Bin Liu 3, Hong Tao Wang 3, Tian Wang 1, Yu Xin Zhang*,1, Lili Zhang*,, Rodney S Ruoff 5, 6,7, Fan Dong 8 1 College of Materials Science and Engineering, Chongqing University, Chongqing, China 2 College of Chemistry and Chemical Engineering, Chongqing University, Chongqing, China 3 School of Materials Science and Engineering, Zhejiang University, Hangzhou 327, China Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Jurong Island 627833, Singapore 5 Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan 919, Republic of Korea 6 Department of Chemistry, Ulsan National Institute of Science and Technology Ulsan 919, Republic of Korea 7 School of Materials Science and Engineering, Ulsan National Institute of Science and Technology 8 College of Environment and Resources, Chongqing Technology and BusinessUniversity, Chongqing, 67, China *Correspondence to: zhangyuxin@cqu.edu.cn; zhang_lili@ices.a-star.edu.sg; Preparation of AGO The activated graphene was prepared via a modified microwave exfoliated method that has been previously reported by the Ruoff group 1. Briefly, graphite oxide (GO) cake was synthesized from purified natural graphite (SP-1, BayCarbon, MI) by the Hummers method. Microwave exfoliated graphite oxide (MEGO) was prepared by irradiating the GO in a microwave oven (GE) in ambient conditions. Upon microwave irradiation, the very large volumetric expansion of the GO cake yields a black and fluffy MEGO powder. The as-prepared MEGO powder was then dispersed and soaked in aqueous KOH solution, followed by filtration and drying, to form the MEGO/KOH mixture for chemical activation. That mixture was then put in a tube furnace, and heated under flowing argon at a pressure of about Torr to 8 C and held at that temperature for one hour to increase the specific surface area.

Determining the mass ratio between birnessite and β-mno 2 We measure the weight of the substrate (MnOOH) before reaction and also the weight of the final composite (β-mno 2 /parallel birnessite) after the reaction. MnOOH is fully converted to beta-mno 2. Therefore, the mass ratio between the birnessite and beta MnO 2 is calculated according to the following equation: C birnessite/beta =(m 2-87m 1 /88)/( 87m 1 /88) Where m 1 is weight of MnOOH, m 2 is weight of β-mno 2 /parallel birnessite composite.

Intensity (a.u.) 2 3 5 6 7 8 2 theta (degree) Supplementary Figure S1 (a) SEM image of MnOOH nanowires; XRD pattern of MnOOH nanowires (purple); theoretical structure values are in red

Intensity (a.u.) 1 2 3 5 6 7 8 2 theta (degree) Supplementary Figure S2 (a) Digital image of MnOOH nanowires after they were treated with KMnO solution (5 µl concentrated sulfuric acid) at room temperature for 3 min; XRD pattern of the same nanowires.

Intensity (a.u.) (a) Sample 1 Sample 2 Sample 3 Sample Sample 5 Intensity (a.u.) Sample 6 Sample 7 Sample 8 Sample 9 1 2 3 5 6 7 8 2 theta (degree) 1 2 3 5 6 7 8 2 theta (degree) Intensity (a.u.) (c) Sample 1 Sample 2 Sample 3 Sample Sample 5 Intensity (a.u.) (d) Sample 6 Sample 7 Sample 8 Sample 9 1 11 12 13 1 15 16 1 11 12 13 1 15 16 2 theta (degree) 2 theta (degree) Supplementary Figure S3 XRD patterns of β-mno 2 /parallel birnessite core/shell nanorod samples.

Supplementary Figure S SEM image of β-mno 2 /parallel birnessite core/shell nanorods (Sample 7).

Quantity Absorbed (cm 3 g -1 STP) 25 (a) 2 15 5 Adsorption Desorption..2..6.8 1. Relative Pressure(P/P ) DV/dD (cm3g-1nm-1).8.6..2. 1 2 3 5 Pore Diameter (nm) Supplementary Figure S5 (a) Nitrogen adsorption and desorption isotherms; their corresponding pore-size distribution curves (adsorption part) of β-mno 2 /parallel birnessite core/shell nanorods (Sample 7).

Transmittance (%) 38 1638 1116 527 7 36 3 2 18 12 6 Wavenumber (cm -1 ) Supplementary Figure S6 FTIR spectra of β-mno 2 /parallel birnessite core/shell nanorods (Sample 7).

Supplementary Figure S7 TEM image of β-mno 2 /parallel birnessite core/shell nanorod (cross section) (Sample 7)

Parallel birnessite (a) Parallel birnessite after 5 cycles Mn 2p O 1s Na 1s K 2p C 1s Intensity (a.u.) Na 1s F 1s as prepared Intensity (a.u.) Common birnessite after 5 cycles after 5 cycles 12 8 6 2 Binding Energy (ev) 176 17 172 17 168 166 Binding Energy (ev) Parallel birnessite- K 2p (c) Common birnessite- K 2p (d) as prepared Intensity (a.u.) as prepared Intensity (a.u.) after 5 cycles 298 296 29 292 29 Binding Energy (ev) after 5 cycles 298 296 29 292 29 Binding Energy (ev) Raw data Mn 3+ Fitting data Mn + Mn 2+ (e) Ra w da ta Mn 3+ Fit tin g da ta Mn + Mn 2 + (f) Intensity (a.u.) Common birnessite as prepared aft d isch arge Intensity (a.u.) Parallel birnessite as prepared aft discharge aft charge aft charge 655 65 65 6 635 Binding Energy (ev) 655 65 65 6 635 Binding Energy (ev) Supplementary Figure S8. (a) XPS wide scan of parallel birnessite. Na 1s core-level XPS spectra for common and parallel birnessite after 5 charge-discharge cycles. (c) K 2p core-level XPS spectra for parallel birnessite before and after charge-discharge cycles. (d) K 2p core-level XPS spectra for common birnessite before and after charge-discharge cycles. (e) Mn 2p spectra for commonl birnessite and (f) parallel birnessite electrodes at different states during the charge-discharge processes

Intensity (a.u.) O(KLL) Mn(LMM) Mn2p O1s C1s K2p K2s (a) Mn3p Mn3s 8 6 2 Binding energy (ev) Weight (%) 11 15 95 9 85 8 2. % 5.2 % beta-mno 2 /parallel birnessite 75 5 15 2 25 3 35 Temperature ( o C) Supplementary Figure S9 (a) Survey XPS spectrum and TGA of beta-mno 2 /parallel birnessite.

Supplementary Figure S1 (a) common birnessite and parallel birnessite that was grown from β-mno 2.

Supplementary Figure S11 (a) SEM images of β-mno 2 /common birnessite core/shell nanorod; TEM images of a β-mno 2 /common birnessite core/shell nanorods.

Capacitance (F g -1 ) 2 15 1 5-5 -1-15 35 3 25 2 15 5 5 mv s -1 1 mv s -1 2 mv s -1 5mV s -1 mv s -1..2..6.8 (a) (c) Parallel birnessite Common birnessite 5 1 15 2 25 3 35 Z''(ohm) 1..8.6..2. -.2 2 15 5.2 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 5 15 2 25 3 Z''(ohm) 2 15 1 5 Time (s) (d) Parallel birnessite Common birnessite 5 1 15 2 Z'(ohm) 5 15 2 Z'(ohm) Supplementary Figure S12 Electrochemical properties of β-mno 2/common birnessite core/shell nanorods measured in 1 M Na2SO aqueous electrolyte in a three-electrode system (a,b); Variation of the capacitance with current density ( c ) and Nyquist plots (d) of β-mno 2/parallel birnessite core/shell nanorods and β-mno 2/common birnessite core/shell nanorods.

Frequency number 12 1 8 6 2 16 17 18 19 2 21 22 Thickness (nm) Frequency number 12 1 8 6 2 29 3 31 32 33 3 35 Thickness (nm) Frequency number 12 1 8 6 2 39 1 2 3 5 Thickness (nm) 12 12 12 Frequency number 1 8 6 2 6 8 5 52 5 56 Thickness (nm) Frequency number 1 8 6 2 6 66 68 7 72 7 76 Thickness (nm) Frequency number 1 8 6 2 8 87 9 93 96 99 12 Thickness (nm) Frequency number 12 1 8 6 2 12 15 18 111 11 Thickness (nm) Frequency number 12 1 8 6 2 116 12 12 128 132 136 Thickness (nm) Frequency number 12 1 8 6 2 11 1 17 15 153 Thickness (nm) Supplementary Figure S13 TEM images of individual nanorods in each of (a) Sample 1; Sample 2; (c) Sample 3; (d) Sample ; (e) Sample 5; (f) Sample 6; (g) Sample 7; (h) Sample 8; (i) Sample 9.

1 8 6 2-2 - -6-8 5 mv s -1 5 mv s - 1 1 mv s - 1 mv s -1 2 mv s - 1..2..6.8 (a) 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 2 3 5 Time (s) Capacitance (F g -1 ) 8 6 2 (c) 5 1 15 2 25 3 35 12 8 6 2 Coulombic efficiency(%) Supplementary Figure S1 Electrochemical properties of β-mno 2/parallel birnessite core/shell nanorod (Sample1) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c)variations of the capacitance and coulombic efficiency with current density.

1 8 6 2-2 - -6-8 5 mv s -1 5 mv s -1 1 mv s -1 mv s -1 2 mv s -1..2..6.8 (a) 1..8.6..2. -.2 2 6 8 Time (s) Supplementary Figure S15 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 2) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with current density..25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 Capacitance (F g -1 ) 2 21 18 15 12 9 6 3 (c) 5 1 15 2 25 3 35 12 8 6 2 Coulombic efficiency(%)

12 5 mv s -1 5 mv s -1 (a) 9 6 3-3 -6-9 1 mv s -1 mv s -1 2 mv s -1..2..6.8 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 2 6 8 12 Time (s) Capacitance (F g -1 ) 2 2 16 12 8 (c) 12 8 6 2 5 1 15 2 25 3 35 Coulombic efficiency(%) Supplementary Figure S16 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 3) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

Current density (A g ) 12 5 mv s -1 5 mv s -1 (a) 9 6 3-3 -6-9 1 mv s -1 mv s -1 2 mv s -1..2..6.8 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 2 6 8 12 Time (s) Capacitance (F g -1 ) 27 2 21 18 15 12 9 6 3 (c) 12 8 6 2 5 1 15 2 25 3 35 Coulombic efficiency(%) Supplementary Figure S17 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample ) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

16 5 mv s -1 5 mv s -1 (a) 12 8 - -8-12 1 mv s -1 mv s -1 2 mv s -1..2..6.8 1..8.6..2. -.2 5 15 2 Time (s).25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 5 1 15 2 25 3 35 Supplementary Figure S18 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 5) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density. Capacitance (F g -1 ) 36 32 28 2 2 16 12 8 (c) 12 8 6 2 Coulombic efficiency(%)

2 16 12 8 - -8-12 -16 5 mv s -1 5 mv s -1 1 mv s -1 mv s -1 2 mv s -1..2..6.8 (a) 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 5 15 2 Time (s) Capacitance (F g -1 ) 35 3 25 2 15 5 (c) 12 8 6 2 5 1 15 2 25 3 35 Coulombic efficiency(%) Supplementary Figure S19 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 6) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

2 15 1 5-5 -1-15 5 mv s -1 5 mv s -1 1 mv s -1 mv s -1 2 mv s -1..2..6.8 (a) 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 5 15 2 25 Time (s) Capacitance (F g -1 ) (c) 12 3 8 2 6 2 5 1 15 2 25 3 35 Coulombic efficiency(%) Supplementary Figure S2 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 7) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

2 15 1 5-5 -1 5 mv s -1 5 mv s -1 1 mv s -1 mv s -1 2 mv s -1 (a) 1..8.6..2..25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 Capacitance (F g -1 ) 5 35 3 25 2 15 5 (c) 12 8 6 2 Coulombic efficiency(%) -15..2..6.8 -.2 5 15 2 Time (s) 5 1 15 2 25 3 35 Supplementary Figure S21 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 8) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

15 5 mv s -1 5 mv s -1 (a) 1 5-5 -1 1 mv s -1 mv s -1 2 mv s -1..2..6.8 1..8.6..2. -.2.25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 5 15 2 Time (s) Capacitance (F g -1 ) 5 35 3 25 2 15 5 (c) 5 1 15 2 25 3 35 12 8 6 2 Coulombic efficiency(%) Supplementary Figure S22 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 9) measured in 1 M Na2SO aqueous electrolyte in a three-electrode system: (a) Cyclic voltammograms at different scan rates; Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with the current density.

25 -.1-.9 V -.1-1.2 V (a) -.1-1. V -.1-1.25 V 2 -.1-1.1 V -.1-1.3 V 15 1 5-5 -1-15 -.2..2..6.8 1. 1.2 1. 1.2 1..25 A g -1.5 A g -1.8 1. A g -1.6 2. A g -1.. A g -1.2. -.2 8 16 2 32 Time (s) Capacitance (F g -1 ) 5 (c) 12 8 3 6 2 2 5 1 15 2 25 3 35 Coulombic efficiency(%) Supplementary Figure S23 Electrochemical properties of β-mno 2 /parallel birnessite core/shell nanorod (Sample 7) measured in 1 M Na2SO aqueous electrolyte in three-electrode system: (a) Cyclic voltammograms with different potional windows (-.1-1.3 V); Galvanostatic charge-discharge curves at different current densities; (c) Variations of the capacitance and coulombic efficiency with current density.

Supplementary Table S1 A comparison between the electrochemical performance of the β-mno2/birnessite core/shell nanorod electrode and other MnO 2 -based electrodes. Samples C(Fg -1 ) Electrolyte Testing condition references Amorphous MnO 2 11 2 M NaCl 5 mv s -1 2 Birnessite MnO 2 11.1 M K 2 SO 2 mv s -1 3 α-mno 2 hollow urchins 123.5 M Na 2 SO 2 mv s -1 Ambigel MnO 2 13 2 M NaCl 5 mv s -1 5 α-mno 2 nanorod 152 1 M Na 2 SO 5 mv s -1 6 MnO 2 nanorod 168 1 M Na 2 SO 5 mv s -1 7 MnO 2 nanowire 176 1 M Na 2 SO 5 mv s -1 8 MnO 2 nanosheet 182.1 M Na 2 SO.1 A g -1 9-1 1 GHCS/MnO 2 18 1 M Na 2 SO.1 A g -1 11 MnO 2 microsphere 19 1 M Na 2 SO.5 A g -1 12 MnO 2 /CNTs/RGO 193 1 M Na 2 SO.2 A g -1 13 α-mno 2 sphere 2.25 M Na 2 SO 1 A g -1 1 Graphene/Honeycomb MnO 2 21 1 M Na 2 SO.5 A g -1 15 α-mno 2 nanorod 25 1 M KOH 1 A g -1 16 α- MnO 2 spherical-like particle 258.7 1 M Na 2 SO.1 A g -1 17 Graphene Hydrogel/ MnO 2 266.8.5 M Na 2 SO 1 A g -1 18 Mesoporous α-mno 2 network 283 1 M Na 2 SO 2 mv s -1 19 MnO 2 nanowire 3 1 M Na 2 SO 5 mv s MnO 2 tubular nanostructure 315 1 M Na 2 SO.2 A g-1-1 21 α-mno 2 ultralong nanowire 35.5 M Na 2 SO 1 A g -1 22 MnO 2 nanoflower 37 1 M Na 2 SO 5 mv s -1 23 MnO 2 hollow structure 366 1 M Na 2 SO 5 mv s -1 2 Co 3 O /MnO 2 8 1 M LiOH 2.67 A g β-mno 2 /parallel birnessite core/shell nanorod 36 1 M Na 2 SO.25 A g -1 This work 2

2 2 16 12 8 - -8-12 Actived Graphene Oxide Beta-MnO 2 /Birnessite core/shell nanorod -1. -.8 -.6 -. -.2..2..6.8 1. 1.2 Supplementary Figure S2 Cyclic voltammograms of β-mno 2 /parallel birnessite core/shell nanorod (Sample 7) (positive electrode) and amego (negative electrode).

8 (a) - -8-12 -1. -.8 -.6 -. -.2. Potental (V). -.2 -. -.6 -.8-1. 5 15 2 25 3 35 Time (s) Supplementary Figure S25 Electrochemical properties of amego measured in 1 M Na2SO aqueous electrolyte in three-electrode system: (a) Cyclic voltammograms with a scan rate of 5 mv s -1 ; galvanostatic charge-discharge curves at a current density of 1. A g -1.

3 2 1-1 -2-3 2. 1.5 1..5. -1. V -1.6 V -1.2 V -1.8 V -1. V -2. V (a)..5 1. 1.5 2. 2 6 8 12 Time (s) (c).25 A g -1.5 A g -1 1. A g -1 2. A g -1. A g -1 Current density (A g-1) Capacitance (F g -1 ) 15 12 9 6 3-3 -6-9 75 6 5 3 15 5 mv s -1 5 mv s -1 1 mv s -1 mv s -1 2 mv s -1 2 mv s -1..5 1. 1.5 2. 9 (d) 1 2 3 5 6 7 8 9 12 8 6 2 Coulombic efficiency(%) Supplementary Figure S26 Capacitance performances of an asymmetric supercapacitor with β-mno 2 /parallel birnessite core/shell nanorod (Sample 7) as positive electrode and amego as negative electrode: (a) CV curves at different cell voltages a scan rate of 5 mv s-1; CV curves recorded at different scan rates with a maximum cell voltage of 2. V; (c) Galvanostatic charge-discharge curves at different current densities between and 2. V; (d) Variations of the capacitance and coulombic efficiency with current densitiy.

Specific capacitance (F g -1 ) 5 5 35 3 25 2 15 1 5 85.7% retained 2 3 5 Cycle number Supplementary Figure S27 Variations of the capacitance with cycle number of the as-assembled supercapacitor.

Sample 7 before dry at 12 o C Sample 7 after dry at 12 o C Intensity (a.u.) 1 2 3 5 6 7 8 2 theta (degree) Supplementary Figure S28 XRD pattern of β-mno 2 /parallel birnessite core/shell nanorod (sample 7) before and after dried at 12 o C for 12 h.

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