344
R. R. Deshmukh et al.
while the constant discharge capacity of over 3000 mAh g
−1 was retained from the
second to the tenth cycle (Chan 2008). Porous-doped Si-NWs produced by direct
etching of boron-doped silicon wafers show large pore size and high porosity that
can retain its structure after lithium ion intercalation while having low stress, and
which gives high capacity and long cycle retention. The capacity remained stable
above 1100, 1600 and 2000 mAh/g at current rates of 18, 4 and 2 A/g, respectively,
even after 250 cycles (Ge et al. 2012). Nanoscroll buffered hybrid nanostructural
(HNS) VO 2 composed of nanobelts and nanowires exhibited long-life performance
with capacity retention over 82% after 1,000 cycles at ~9 C (1,000 mA g
−1 ), and high
rate up to ∼20 C (2,000 mAh g
−1 ) (Mai et al. 2013). Similarly, Li 2 MnO 3 nanowire
anode material for Li batteries had the reversible capacity that can reach 1279 mAh
g
−1 at a current density of 0.5 mAh g
−1 after 500 cycles, more than pure MnO 2
nanowires (Wang et al. 2014).
In case of supercapacitors, it was reported that single-crystalline Co 3 O 4 nanowire
array on a nickel and single-crystalline NiCo 2 O 4 nanoneedle arrays on conductive
substrates (such as Ni foam and Ti) had a high specific capacitance of 599 F/g and
1118.6 F g
−1 respectively (Xia et al. 2012; Zhang et al. 2012). Vertically aligned
PANI nanowire arrays have great potential applications in electrode materials of
supercapacitor. The specific capacitance can keep high value 950 F g
−1 even at the
large current density 40 A g
−1 . By using different electrolytes like LiTFSI, HClO 4
aqueous solution, and nonsolvent electrolyte EMITFSI ionic liquids, the capacitive
behavior of PANI nanowire arrays were also investigated. They show a quite stable
capacitance in ionic liquids during the cyclic life test, which may guide to the finding
of a suitable electrolyte for their future applications (Wang et al. 2014).
4.2 Nanorods for ESS
The nanorods are similar to nanowires except the fact that the height is restricted
in case of nanorods. Therefore, nanorods/nanopillars surface area ratio is limited
compared to nanowires/nanofibers; but the neighboring structure of the individual nanorod/nanopillar significantly lowers chances of collapse making them more
accessible to the electrolyte, which increases the ionic conductivity.
Mesoporous silicon nanorods and SnO 2 nanorod arrays were prepared using
MWCNTs template and flexible metallic substrates (Fe–Co–Ni alloy and Ni foil)
respectively. The silicon nanorods showed a reversible capacity as high as 1038
mAh g
−1 after 170 cycles while SnO 2 nanorod had 580 mAh g
−1 after 100 cycles
(Liu et al. 2009). Using electron-cyclotron-resonance CVD process, free-standing Si
nanorods are prepared on a copper substrate which shows capacity of 2911 mAh g
−1
and a coulombic efficiency of 95% during the first discharge with capacity retention
of 84% after 25 cycles. Also, using electron-cyclotron-resonance plasma-enhanced
CVD method, bundles of Si nanorods were fabricated which had discharge capacity of 2990 mAh g
−1 with a coulombic efficiency of 92% (Chen et al. 2018). TiO 2
nanorod film when used as Li-ion battery electrode had initial reversible discharge
R. R. Deshmukh et al.
while the constant discharge capacity of over 3000 mAh g
−1 was retained from the
second to the tenth cycle (Chan 2008). Porous-doped Si-NWs produced by direct
etching of boron-doped silicon wafers show large pore size and high porosity that
can retain its structure after lithium ion intercalation while having low stress, and
which gives high capacity and long cycle retention. The capacity remained stable
above 1100, 1600 and 2000 mAh/g at current rates of 18, 4 and 2 A/g, respectively,
even after 250 cycles (Ge et al. 2012). Nanoscroll buffered hybrid nanostructural
(HNS) VO 2 composed of nanobelts and nanowires exhibited long-life performance
with capacity retention over 82% after 1,000 cycles at ~9 C (1,000 mA g
−1 ), and high
rate up to ∼20 C (2,000 mAh g
−1 ) (Mai et al. 2013). Similarly, Li 2 MnO 3 nanowire
anode material for Li batteries had the reversible capacity that can reach 1279 mAh
g
−1 at a current density of 0.5 mAh g
−1 after 500 cycles, more than pure MnO 2
nanowires (Wang et al. 2014).
In case of supercapacitors, it was reported that single-crystalline Co 3 O 4 nanowire
array on a nickel and single-crystalline NiCo 2 O 4 nanoneedle arrays on conductive
substrates (such as Ni foam and Ti) had a high specific capacitance of 599 F/g and
1118.6 F g
−1 respectively (Xia et al. 2012; Zhang et al. 2012). Vertically aligned
PANI nanowire arrays have great potential applications in electrode materials of
supercapacitor. The specific capacitance can keep high value 950 F g
−1 even at the
large current density 40 A g
−1 . By using different electrolytes like LiTFSI, HClO 4
aqueous solution, and nonsolvent electrolyte EMITFSI ionic liquids, the capacitive
behavior of PANI nanowire arrays were also investigated. They show a quite stable
capacitance in ionic liquids during the cyclic life test, which may guide to the finding
of a suitable electrolyte for their future applications (Wang et al. 2014).
4.2 Nanorods for ESS
The nanorods are similar to nanowires except the fact that the height is restricted
in case of nanorods. Therefore, nanorods/nanopillars surface area ratio is limited
compared to nanowires/nanofibers; but the neighboring structure of the individual nanorod/nanopillar significantly lowers chances of collapse making them more
accessible to the electrolyte, which increases the ionic conductivity.
Mesoporous silicon nanorods and SnO 2 nanorod arrays were prepared using
MWCNTs template and flexible metallic substrates (Fe–Co–Ni alloy and Ni foil)
respectively. The silicon nanorods showed a reversible capacity as high as 1038
mAh g
−1 after 170 cycles while SnO 2 nanorod had 580 mAh g
−1 after 100 cycles
(Liu et al. 2009). Using electron-cyclotron-resonance CVD process, free-standing Si
nanorods are prepared on a copper substrate which shows capacity of 2911 mAh g
−1
and a coulombic efficiency of 95% during the first discharge with capacity retention
of 84% after 25 cycles. Also, using electron-cyclotron-resonance plasma-enhanced
CVD method, bundles of Si nanorods were fabricated which had discharge capacity of 2990 mAh g
−1 with a coulombic efficiency of 92% (Chen et al. 2018). TiO 2
nanorod film when used as Li-ion battery electrode had initial reversible discharge