Journal of Power Sources 153 (2006) 165–169
Short communication
Lithium insertion into manganese dioxide electrode
in MnO
2
/Zn aqueous battery
Part III. Electrochemical behavior of -MnO
2
in aqueous
lithium hydroxide electrolyte
Manickam Minakshi
a,∗
, Pritam Singh
a
, Touma B. Issa
a
, Stephen Thurgate
a
, Roland De Marco
b
a
Division of Science and Engineering, Murdoch University, Murdoch 6150, WA, Australia
b
Department of Applied Chemistry, Curtin University of Technology, Bentley 6102, WA, Australia
Received 30 January 2005; accepted 11 March 2005
Available online 31 May 2005
Abstract
The electrochemical behavior of -MnO
2
in lithium hydroxide (LiOH) and potassium hydroxide (KOH) aqueous media has been studied
using slow-scan cyclic voltammetry (25 Vs
-1
) in conjunction with X-ray analysis (XRD) and scanning electron microscopy (SEM). The
reduction of -MnO
2
in aqueous LiOH results in intercalation of Li
+
forming a new phase of lithium intercalated MnO
2
(Li
x
MnO
2
). The
process is found to be reversible. In this regard, the reduction of -MnO
2
in LiOH is quite different from that in aqueous KOH, which is
irreversible and no lithium intercalation occurs. This difference in behavior is explained in terms of the relative ionic sizes of Li
+
and K
+
.
The Li
x
MnO
2
lattice is stable only for Li
+
because Li
+
and Mn
4+
are of approximately the same size whereas K
x
MnO
2
is not stable because
K
+
has almost double the size.
© 2005 Elsevier B.V. All rights reserved.
Keywords: Cyclic voltammetry (CV); -MnO
2
; Lithium insertion; Rechargeability; Ionic size; Aqueous battery
1. Introduction
Manganese dioxide (MnO
2
) is commonly used as a cath-
ode in aqueous zinc/MnO
2
batteries, which use KOH as the
electrolyte. MnO
2
undergoes reduction through a mechanism
involving proton insertion into the MnO
2
structure. In a re-
cent paper [1], we reported that when MnO
2
is discharged in
cells containing aqueous LiOH electrolyte the mechanism is
quite different, i.e. instead of H
+
insertion Li
+
intercalation
into the lattice of the host -MnO
2
occurs. This intercalation
was shown to be reversible. This finding is interesting be-
cause it opens up a new field of aqueous batteries utilizing
rechargeable -MnO
2
cathode.
∗
Corresponding author. Tel.: +61 8 9360 2379; fax: +61 8 9310 1711
E-mail addresses: minakshi@murdoch.edu.au (M. Minakshi),
p.singh@murdoch.edu.au (P. Singh).
In this paper, we report the results of a subsequent study,
specifically focusing on the mechanism of the intercalation
reaction. A cyclic voltammetric (CV) study together with
characterization by specialist techniques like X-ray diffrac-
tion (XRD) and scanning electron microscope (SEM) of the
materials that are formed during the electrochemical dis-
charge of -MnO
2
is carried out.
2. Experimental
The cell design, experiment details, and the method of
preparing X-ray, XPS and IR samples have been described
elsewhere [1,2].
2.1. Slow-scan cyclic voltammetry
For cyclic voltammetric experiments, a three-electrode
cell was used. The working electrode, consisted of a disk
0378-7753/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jpowsour.2005.03.184