Supplementary Information
Electrostatic Induced Stretch Growth of Homogeneous β-Ni(OH)2 on Graphene
with Enhanced High-Rate Cycling for Supercapacitors
Zhong Wu1,2, Xiao-Lei Huang1, Zhong-Li Wang1, Ji-Jing Xu1, Heng-Guo Wang1 &
Xin-Bo Zhang1
1
State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of
Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
2
University of Chinese Academy of Sciences, Beijing 100124, China.
Correspondence and requests for materials should be addressed to X.Z.
([email protected]).
1
Specific capacitance calculation. The specific capacitance is calculated by
integrating the area under the CV curves, that is to say, the specific capacitance (Cs, F
g-1) values at different scan rates (mV s-1) in the CV measurements are calculated
using the following equation:
Vc
1
Cs 
iVdV (1),1

vw(V ) Va
Where ΔV (V) is the applied potential window (Va to Vc), v (mV s-1) is the scan rate,
and w (g) is the weight of the active material.
Specific capacitance could also be calculated from the galvanostatic discharge
curves, using the following equation:
C
It
(2),1
mV
Where I (A) is charge or discharge current, Δt (s) is the time for a full charge or
discharge, m (g) indicates the mass of the active material, and ΔV represents the
voltage change after a full charge or discharge.
2
Figure. S1 | FESEM and TEM images of (a, b) precursor Ni(OH)2，and (c, d)
pure Ni(OH)2.
3
Figure S2 | Schematic illustration of disordered stack stretch growth on
graphene to form ordered stack.
4
Figure. S3 | N2-adsorption-desorption isotherms of (a) Ni(OH)2/GS-5 and (b)
pure Ni(OH)2. (c) Thermogravimetric analysis curves of Ni(OH)2/GS-5 and
Ni(OH)2.
In addition, the N2-adsorption-desorption isotherm and the pore-size distribution
are collected. Specific surface area is calculated by the Brunaure-Emmert-Teller
(BET) method. The BET surface area of Ni(OH)2/GS is found to be 53.92 m2 g-1. In
addition, the isotherms (Figure S3a) shows a slight rise at low P/P0 and a hysteresis
loop in the high P/P0 range of 0.4-1.0. The hysteresis loop in the low pressure range is
assigned to the presence of micropores and that in the high pressure range is assigned
to the presence of mesopores and macropores. The pore diameter distribution is
estimated by a Barrett–Joyner–Halenda method using the isotherm adsorption branch
(Figure S3a) and a total pore volume of Ni(OH)2/GS is found to 0.13 cm3 g-1.
According to the pore-size distribution, it is clearly observed that mesopores with a
wide size range (2-50 nm) are dominated in the composite, which would facilitate the
electrolyte diffusion to form a uniform interface between the electrode material and
the electrolyte for the reversible redox processes. Figure S3b demonstrates that the
BET surface area of pure Ni(OH)2 is found to be 43.587 m2 g-1, and a total pore
volume of pure Ni(OH)2 is 0.207 cm3 g-1.
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Figure. S4 | (a) Galvanostatic discharge curves of Ni(OH)2/GS-5, (b)
Galvanostatic discharge curves of pure Ni(OH)2, (c) Average specific
capacitances of Ni(OH)2/GS-5 and pure Ni(OH)2 at various current densities, (d)
Ragone plot (power density vs energy density) of Ni(OH)2/GS-5 and pure
Ni(OH)2 electrodes.
In addition to CV curves, galvanostatic discharge curves (GC) (Figure S4) are also
employed to estimate the specific capacitances of Ni(OH)2/GS-5 and pure Ni(OH)2.
The specific capacitances of Ni(OH)2/GS-5 and pure Ni(OH)2 electrodes are 1597 and
1138 F g-1 at 1 A g-1. At different current densities, the specific capacitance of
Ni(OH)2/GS-5 is higher than pure Ni(OH)2, which is in accordance with CV results. It
can be attributed to the improved electrical conductivity and facilitated ion transport
and diffusion rate. Figure S4d is the ragone plot of the Ni(OH)2/GS-5 supercapacitor,
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which shows the relation-ship between energy density (Wh kg-1) and power density
(kW kg-1). At a scan rate of 50 mV s-1, the device can achieve a high energy density of
17.9 Wh kg-1 at a high power density of 6.4 kW kg-1. Remarkably, the maximum
energy density can exhibit an impressive high specific energy density of 52.2 Wh
kg-1.
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Figure. S5 | (a) Galvanostatic discharge curves of Ni(OH)2/GS-20, Ni(OH)2/GS-5,
and Ni(OH)2/GS-2 at 1 A g-1. (b) Galvanostatic discharge curves of
Ni(OH)2/GS-20 at various current densities, (c) CV curves of Ni(OH)2/GS-20 at
various scan rates. (d) Galvanostatic discharge curves of Ni(OH)2/GS-2 at
various current densities. (e) CV curves of Ni(OH)2/GS-2 at various scan rates.
As shown in Figure S5, galvanostatic discharge curves (GC) and CV curves are
also employed to estimate the specific capacitance of Ni(OH)2/GS-20, Ni(OH)2/GS-5,
and Ni(OH)2/GS-2 composites.
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Table S1 Specific capacitances of pure Ni(OH)2 and Ni(OH)2/GS composites.
2 mV s-1
20 mV s-1
50 mV s-1
100 mV s-1
200 mV s-1
Ni(OH)2/GS-5
1503
693
515
395
299
Ni(OH)2
1064
458
306
209
142
Ni(OH)2/GS-20
1052
522
366
266
193
Ni(OH)2/GS-2
1334
527
380
279
199
Specific capacitances (F g-1) are calculated from CV curves.
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Table S2 Specific capacitances of pure Ni(OH)2 and Ni(OH)2/GS composites.
1 A g-1
4 A g-1
10 A g-1
40 A g-1
100 A g-1
Ni(OH)2/GS-5
1597
1220
825
291
174
Ni(OH)2
1138
609
333
102
57
Ni(OH)2/GS-20
1243
759
492
---
75
Ni(OH)2/GS-2
1280
885
499
---
96
Specific capacitances (F g-1) are calculated from galvanostatic discharging curves.
For comparison, Table S1 and S2 summarize the specific capacitances of
Ni(OH)2/GS-20, Ni(OH)2/GS-5, Ni(OH)2/GS-2 composites and pure Ni(OH)2
calculated from CV curves and galvanostatic discharge curves. It is found that the
specific capacitances of pure Ni(OH)2 is much lower to these of the Ni(OH)2/GS-5
composite at all tested conditions, providing another evidence for the superiority of
the Ni(OH)2/GS composite. Moreover, neither excess Ni(OH)2 nor excess graphene is
favorable to enhance their capacitive behavior. On the one hand, excess Ni2+ ions around
GO prevent themself from dispersing on GO nanosheets well thus resulting in low capacitance.
On the other hand, excess GO in Ni(OH)2/GS-2 induce the aggregation of graphene
sheets and the lower capacitance of graphene ascribe to EDLC behavior compromise
the capacitance base on the total mass of the composite. The optimal ratio of GO to
Ni(OH)2 is 1:5 by mass.
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Reference
1. Wang, H., Casalongue, H. S., Liang, Y. & Dai, H. Ni(OH)2 nanoplates grown on
graphene as advanced electrochemical pseudocapacitor materials. J. Am. Chem. Soc.
132, 7472-7477 (2010).
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