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