Film: A Pseudocapacitive Material with Superior Performance

Transcription

1 Supporting Information for Three-Dimentional Porous NanoNi/Co(OH) 2 Nanoflake Composite Film: A Pseudocapacitive Material with Superior Performance X. H. Xia, J. P. Tu*, Y. Q. Zhang, Y. J. Mai, X. L. Wang*, C. D. Gu, and X. B. Zhao State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou , China tujp@zju.edu.cn; wangxl@zju.edu.cn Figure S1. Schematic illustration for the formation of 3D porous nanoni/co(oh) 2 nanoflake composite film.

2 Figure S2. SEM image of side view of 3D porous nanoni/co(oh) 2 nanoflake composite film (the fine feature in inset).

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4 (d) Ni (111) -Co(OH) 2 Intensity / a.u. (001) (100) Ni (200) (110) Ni (220) / degree Figure S3. (a), (b) SEM and (c) TEM images of Co(OH) 2 nanoflake film grown on the nickel foam substrate; (d) XRD pattern of Co(OH) 2 nanoflake film grown on the nickel foam substrate.

5 (a) Ni 2p3/ Intensity / a.u Binding Energy / ev (b) O 1s Ni-OOH Intensity / a.u. NiO Binding Energy / ev Figure S4. XPS spectra of the 3D porous nanoni film after CV test: (a) Ni 2p 3/2 and (b) O 1s. Ni 2p 3/2 peak includes two components, one at ev due to Ni O bonds and the other one at ev due to Ni-OOH bands, respectively. The Ni-OOH bands mainly come from higher valence nickel hydroxides such as NiOOH, or

6 4Ni(OH) 2 NiOOH xh 2 O. In O1s spectra, the peak at ev reveals the existence of Ni-OOH bands, which are consistent with Ni 2p 3/2 spectrum.

7 Current density / A cm A 1 (0.186 V) A 2 X 1 (0.397 V) X 2 (0.434V) C 1 (0.145 V) C 2 (0.324 V) Potential / V (vs. Hg/HgO) Figure S5. CV curve of 3D porous nanoni film and 3D porous nanoni/co(oh) 2 nanoflake composite film in the potential region of V at a scanning rate of 1 mv s 1.

8 (a) Potential / V (vs. Hg/HgO) ma cm ma cm ma cm ma cm ma cm Time / s (b) Potential / V (vs. Hg/HgO) ma cm -2 4 ma cm ma cm ma cm ma cm Time / s Figure S6. Discharge curves of (a) 3D porous nanoni film and (b) nickel foam at different discharge current densities The specific capacitance is calculated according to the following equation:

9 C= I t M V where C (F g 1 ) is specific capacitance, I (ma) represents discharge current, and M (mg), ΔV (V) and Δt (sec) designate mass of active materials, potential drop during discharge and total discharge time, respectively. Energy density (E) was derived from the CV curves using the following equation: E C V where C is the specific capacitance of the active material, and V is the voltage across the electrode. Power density (P) was calculated from the following equation: E P t where E is the energy density, and Δt is the discharge time.

10 2500 Speciic capacitance / F g Porous nanoni/co(oh) 2 film Co(OH) 2 film on nickel foam Current density / A g -1 Figure S7. Specific capacitances at different discharge current densities.

11 (a) Discharge electric quantity / C cm Cycle number (b) Discharge electric quantity / C cm Cycle number Figure S8. Cycling performances of discharge electric quantity of (a) 3D porous nanoni film and (b) 3D porous nanoni/co(oh) 2 nanoflake composite film at 2 ma cm 2 (corresponding to 2 A g 1 based on mass of Co(OH) 2 ).

12 The discharge electric quantity (Q) of Co(OH) 2 in the composite film during cycle is obtained by Figure S6b minus Figure S6a. Interestingly, the 3D porous nanoni film exhibits stable discharge electric quantity at 2 ma cm 2 during cycling, meaning that it will not affect the cycling trend of Co(OH) 2 in the composite film. We calculated the specific capacitance during cycle according to the equation: Q C V where C is specific capacitance, and V is voltage across the electrodes, and finally got the cycling performance of specific capacitance of Co(OH) 2 in the composite film (Figure 5). For nickel foam-supported Co(OH) 2 film, the nickel foam contributes little to the specific capacitance of the films and does not have influence on the cycling characteristics of Co(OH) 2 nanoflakes grown on nickel foam.

13 Porous nanoni/co(oh) 2 film Co(OH) 2 film on nickel foam Z im / Z im / Z re / Z re / Figure S9. EIS plots of two film electrodes at 100 % depth of discharge (magnified EIS plot of porous nanoni/co(oh) 2 film in inset).