Electrochimica Acta 55 (2010) 8023–8029
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Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Electrochemical preparation and characterization of V
2
O
5
/polyaniline composite
film cathodes for Li battery
Kyung-Il Park
a
, Hahn-Mok Song
a
, Youna Kim
a
, Sun-il Mho
a,∗
, Won Il Cho
b
, In-Hyeong Yeo
c
a
Division of Energy Systems Research, Ajou University, Suwon 443-749, Republic of Korea
b
Battery Research Center, Korea Institute of Science and Technology, Seoul 130-650, Republic of Korea
c
Department of Chemistry, Dongguk University, Seoul 100-715, Republic of Korea
article info
Article history:
Received 28 October 2009
Received in revised form
19 December 2009
Accepted 21 December 2009
Available online 28 December 2009
Keywords:
V2O5/PANi composite film
Electrochemical method
Specific capacity
Charge/discharge cycle stability
abstract
Vanadium pentoxide/polyaniline (V
2
O
5
/PANi) composite films were prepared by a two-step electro-
chemical method and evaluated for their application in lithium batteries. As a first step the PANi film was
potentiodynamically grown in an acid solution containing aniline monomer, and secondly vanadium
oxide was oxidatively deposited on the polyaniline film in a temperature controlled VOSO
4
solution. The
increased current efficiency obtained with the larger anodic current in the high temperature solutions
results in high contents of V
2
O
5
in the composites, even if the oxidative dissolution of PANi also occurs.
The large value of the diffusion coefficient estimated from the cyclic voltammograms for the composite
film provides evidence for the synergistic effect of the conducting polymer and the inorganic composite.
The cell exhibited excellent cycle stability with a high charge storage capacity. The large increase in the
specific capacity for the composite film prepared in this work demonstrates that the conducting poly-
mer in the composite acts as a binding and conducting element by contributing its electroactivity. The
V
2
O
5
/PANi composite film cathodes show a large specific capacity (ca. 270 mAh/g) and improved cycla-
bility with an extremely small amount of capacity fading (ca. 3.4%) during repeated charge/discharge
cycles.
© 2010 Elsevier Ltd. All rights reserved.
1. Introduction
Layer-structured vanadium oxides have versatile redox depen-
dent properties and have found wide applications in catalysis,
electrochromism, and electrochemistry. Vanadium pentoxide has
been intensively investigated as one of the most promising cath-
ode materials in rechargeable lithium batteries [1–9]. The main
advantages of V
2
O
5
include its high theoretical specific capac-
ity, structural flexibility with lithium intercalation/deintercalation,
high thermal stability, and environmental friendliness. Lithium ion
can accommodate up to 3 moles (Li
x
V
2
O
5
;0< x < 3) into the V
2
O
5
lattices, producing various structures including some reversible
one, resulting in a long battery cycling life. The stability of the
capacitance with reversible phase changes corresponds to the
intercalation/deintercalation amounts of two equivalent lithium
atoms per V
2
O
5
, x = 2 in the phase -Li
x
V
2
O
5
(295 mAh/g). However,
the intercalation capacity and charge/discharge rate of vanadium
oxides as electrode materials for lithium batteries are limited by the
moderate electrical conductivity and the low diffusion coefficient
of lithium ions in the vanadium oxide matrix. The use of conducting
∗
Corresponding author. Tel.: +82 31 219 2599; fax: +82 31 219 1615.
E-mail address: mho@ajou.ac.kr (S.-i. Mho).
polymer and vanadium oxide composite materials as electrodes is
of great interest to improve the lithium ion intercalation capacity
and accessibility, mechanical flexibility, ion mobility and con-
ductivity of rechargeable lithium batteries [10–18]. Polyaniline
(PANi) is unique among the various conducting polymers in that it
can be easily produced with controlled morphological, structural,
and electronic properties by chemical or electrochemical means
[19–25]. Polyaniline and vanadium oxide composite powders are
normally prepared by adding the aniline monomer to the xero-
gel under appropriate conditions, since aniline monomer can be
oxidatively polymerized by V
2
O
5
[14–16]. Electrochemical meth-
ods of producing PANi offer additional variables for the control of
the polymer morphology [17–23]. As part of our current research
into the synthesis of metal oxide-conducting polymer composite
films that can be used for lithium batteries and flexible batteries in
the future, we carried out a systematic study of the preparation of
composite films and evaluated their performances as electrodes.
We present here the results of the optimization of the electro-
chemical process for vanadium oxide and polyaniline composite
(V
2
O
5
/PANi) films with controlled compositions in order to obtain
the best possible results for battery applications. We analyzed the
thermal, structural and electrochemical properties and present the
excellent properties of the V
2
O
5
/PANi composite film electrodes for
Li rechargeable batteries.
0013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2009.12.047