221st ecsmeeting-220
TRANSCRIPT
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7/30/2019 221st ECSMeeting-220
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All-Solid Thin-Filmed Li-Ion Rechargeable Battery with
Aligned Carbon Nanotube Anode
M. Baba1,2, F. Izumida1,2, R. Ye2, J. Yoshida2, T.
Ushirokawa2, K. Ohta2 and M. Kusunoki31
Graduate School of Engineering, Iwate University,
Morioka 020-8551, Japan2 Electronics Course, Iwate Industrial Technology Junior
College, Yahaba, Iwate 028-3615, Japan3 EcoTopia Science Institute, Nagoya University, Nagoya
464-8603, Japan
We reported the thin-filmed, solid-state
rechargeable battery composed of a LiMn2O4 positive
electrode, a Li3PO4 solid electrolyte and a V2O5 negative
electrode.1 We have also investigated the lithium-ion (Li+)
battery using porous silicon anode.2
Here, another new
type of lithium-ion (Li+) battery using carbon nanotube
(CNT) anode is reported, exhibiting an efficient solid-
state rechargeable operation. The CNTs which were
discovered by S. Iijima in 19913 are expected to be usedto anode material of Li-ion rechargeable batteries4 as one
of the various applications.
In the present experiment, the CNT layer was
formed on a SiC wafer by the SiC surface decomposition
(SSD) method.5 Furthermore, the CNT surface was
modified by Ar-ion sputtering method6 in order to work
efficiently as an anode. Figures 1(a) and (b) show FE-
SEM images of a surface and a cross section of a CNT
layer formed on a 6H-SiC wafer after the Ar-sputter with
40W-30s under 110-4Torr. In this case, the SiC wafer
was heated at 1700 C for 30min in a vacuum (110- 4
Torr) and thereafter the CNT layer was sputtered at RTfor 30s under 110
- 4Torr of Ar pressure. In Fig.1(a), the
surface becomes grainy more with diameter of ~30 nm
and in Fig.1(b), such grainy bundle consisting of several
CNTs were aligned vertical to the SiC wafer with a height
of ~220nm and the top surface was modified smoothly.
Fig.1 FE-SEM images of a surface (a) and a cross section
(b) of a CNT layer on a 6H-SiC wafer.
A Li3PO4 film (300nm thick) and then a
LiMn2O4 film (350nm thick) were deposited on the CNT
layer by a magnetron RF sputtering method7, and finally a
Ti metal film (160nm thick) in order to keep an electrical
contact was deposited by a magnetron DC sputtering
method. Figure 2(a) shows a typical thin-filmed Li-ion
rechargeable battery with CNT anode ( thin-filmed CNT
battery). The operating area of the present battery is
6mm2. Figure 2(b) shows charge-discharge characteristic
curves of the thin-filmed CNT battery with charge-
discharge current of 0.4A (current density of 6.7A/cm2)
and cut-off voltages of 4.0 and 0.5V. Here, judging from
the large difference8
of the intercalation/de-intercalation
potentials of a Li+ ion between LiMn2O4 cathode and C-
like CNT anode, such a high voltage plateau around 4.0
3.6V is reasonable for the present battery. In addition,
this figure which seems to be only a few lines contains 64
curves from the first to 64the cycle. These charge-
discharge curves were measured after the acceleration test
of 3000 cycles with a narrow voltage window as
described later. Estimating from the thickness of the
cathode layer, the discharge capacity density is
390mAh/cm3.
Fig.2 Overview (a) and charge-discharge characteristics
(b) of a thin-filmed CNT battery.
Figure 3(a) shows Charge and discharge
characteristics of the thin-filmed CNT battery after a
long-term cyclic performance under the acceleration test.This figure contains 230 curves from the 1831st to
2030the cycle. The test condition is as follows; charge-
discharge current is 0.4A, and cut-offs of 4.0V for
charge and 20min for discharge, resulting a voltage
window range is between 4.0 and 3.75V. Figure 3(b)
shows a cell voltage at the each discharge end under the
acceleration test during 2000 cycles. The good
cycleability of the thin-filmed CNT battery was obtained.
Fig.3 Charge and discharge characteristics (a) and cell
voltage at the discharge end (b) under the acceleration test
of a thin-filmed CNT battery.
In conclusion, we found out for the first time that
a carbon nanotube layer efficiently intercalates and de-
intercalates Li ions and as a result, it acts well as an anode
of a Li-ion rechargeable battery. The CNT anode of thepresent battery gives excellent properties of high Li-
accommodation, efficient release of a volume change, a
good role common between a negative active material and
a electrical contact, and a potential use as a monolithic
power source to integrated circuits on a SiC tip.
1M. Baba, et al, Electrochem. & Solid-State Lett. 2, 320
(1999).2M. Baba, T. Ushirokawa, R. Ye and K. Ohta, 216th ECS
Meeting, Vienna, Austria (2009).
3S. Iijima, Nature 354, 56 (1991).4 B. Gao, A. Kleinhammes, X.P. Tang, C. Bower, L.
Fleming, Y. Wu, and O. Zhou, Chem. Phys. Lett. 307,
153 (1999).5M. Kusunoki, J. Shibata, M. Rokkaku, and T. Hirayama,
Jpn. J. Appl. Phys. 37, L605 (1998).6F. Izumida, R. Ye, K. Ohta, M. Baba and M. Kusunoki,
Physics Procedia 14, 164-166 (2011).7M. Baba, et al, J. Power Sources 97-98, 798 (2001).8Tang Xin-cun, et al, Trans. Nonferrous Met. Soc. China
16(2006).
0.0 0.5 1.0 1.5 2.0
0
1
2
3
4
5
CellVoltage(V)
Charge-discharge Time (h)
1st - 64th
cut-off: 4.0 - 0.5V 6.7A/cm2
(a) (b)
0 5 10 15 20
2.5
3.0
3.5
4.0
4.5
1st - 230th (1831st - 2030th)
Cycle Number
CellVoltage(V)
cut-off: 4V/20min 6.7A/cm2
(a)
0 500 1000 1500 2000
0
1
2
3
4
5
6.7A/cm2
CellVoltageatDischargeEnd(V)
Cycle Number
cut-off: 4V/20min
(b)
(b)(a)
Abstract #220, 221st ECS Meeting, 2012 The Electrochemical Society