Biomedical Engineering Reference
In-Depth Information
3.0
(b)
(a)
Crystalline ntTiO
2
(900 nm)
onto Ti foil
Amorphous ntTiO
2
(900 nm)
onto Ti foil
3.0
2.7
50
th
4
th
1
st
50
th
1
st
2.7
2.4
2.4
2.1
2.1
1.8
1.8
1.5
1.5
1.2
1.2
0.9
50
th
4
th
2
nd
1
st
0.9
50
th
2
nd
1
st
0
20
40
60
80
100
120
0
10
20
30
40
50
Areal Capacity /
µ
A h cm
-2
Areal capacity /
µ
A h cm
-2
(c)
(d)
50
th
1
st
Charge
4
th
Cha
r
ge
1
st
1
st
50
th
4
th
1
st
Discharge
Discharge
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
Voltage / V
Voltage / V
Figure 5.15
Galvanostatic discharge/charge curves vs. composition of TiO
2
nanotube layers: (a) as-formed and (b) annealed using 20
μ
A cm
-
. Voltage
2
limits: 2.6-1.0 V. Derivative curves during the 1
st
, 2
nd
, 3
rd
, and 4
th
discharge/
charge of (c) crystalline ntTiO
electrodes. Note
that the bottom part indicates the lithiation (discharge) process and the
upper part shows the delithiation (charge) process.
and (d) amorphous ntTiO
2
2
with 900 nm length heated at 450°C
is tested in lithium cell, the voltage plateaus are observed during
the discharge and charge (Fig. 5.15a) at potential of 1.72 and 2.0 V,
respectively. The plateaus are attributed to insertion and deinsertion
of Li
When sample of ntTiO
2
+
from tetrahedral and octahedral sites of crystalline anatase
TiO
nanotubes. The deinsertion potential is slightly higher than
in crystalline anatase [89]. After the first discharge, the capacity
is 50 μAh cm
2
-
2
and the reversible capacity is 38 μAh cm
-
2
leading
to an irreversible capacity of 12 μAh cm
. In its derivative curves
(Fig. 5.15c), one can see clearly the peaks, which are very intense
and narrow, and correspond to reduction/oxidation steps of anatase
when cycling. It is worth noting that the intensity of the peaks is
maintained on further cycling and, thus, indicates that crystalline
anatase is accommodating lithium reversibly in its structure on
further cycles (Fig. 5.15a-d shows 50 cycles).
-
2
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