Abstract:
Supercapacitor has been highlighted and pointed as the most selectable energy
storage devices due to its capability and potentiality to charge and recharge in few
seconds. Graphene/nickel (graphene/Ni) is the new innovation of hybrid materials
for supercapacitor which has the potential to improve the performance of the
commercial supercapacitor. In this research, graphene/Ni composite has been
prepared via two methods; ball-milling and hydrothermal, and subjected to
structural, morphology and electrochemical characterizations. The grapheme and
graphene/Ni composite were successfully synthesized without any impurity. The asreceived
Ni nanoparticle from Sigma Aldrich contained NiO, whereas pure phase of
Ni nanoparticle was obtained when prepared via hydrothermal method. The Ni
nanoparticle loadings in the graphene/Ni composite prepared via ball-milling method
were estimated to be 27, 34 and 48 wt.%, whereas for hydrothermal method, the
graphene/Ni composite was found to be approximately 9, 23 and 38 wt.%. The Ni
nanoparticles with particle size of approximately 2 μm, were well dispersed on the
graphene layers without any agglomerations. Electrochemical results showed that the
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specific capacitance exhibited by the graphene/Ni 34 wt.% composite prepared via
ball-milling was 275 F g−1 at a current density of 2 A g−1, which is higher than the
specific capacitance of bare graphene (145 F g−1) and bare Ni (3 F g−1). Graphene/Ni
34 wt.% electrode also showed superior performance at a high current density,
exhibiting a capacitance of 190 F g−1 at a current density of 5 A g−1 and a capacitance
of 144 F g−1 at a current density of 10 A g−1. For hydrothermal method, the specific
capacitance ofis 203, 150 and 102 F g-1 at 2, 5 and 10 A g-1, respectively, was
obtained by graphene/Ni 9 wt.% composite. Graphene/Ni 34 wt.% and graphene/Ni
9 wt.% synthesized from the respective methods, retains ~91% and ~85% of its
initial capacitance value after 1000 cycles compares to other electrodes with low
equivalent series resistance. The enhanced performance of these hybrid materials is
best described by the synergistic effect, i.e. dual charge-storage mechanism, which is
demonstrated by electrical double layer and pseudocapacitance materials.
