Journal of New Materials for Electrochemical Systems 9, 333-338 (2006)
© J. New Mat. Electrochem. Systems
New Generation of the Zinc — Manganese dioxide cell
Zbigniew Rogulski, Maciej Chotkowski, ∗ Andrzej Czerwiński
Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw (Poland)
Industrial Chemistry Research Institute, Rydygiera 8, 01-793 Warsaw (Poland)
Received: February 14, 2006, Accepted: May 27, 2006
Abstract: The application of Reticulated Vitreous Carbon (RVC) as the cathode current collector and carrier of cathodic active
mass for the zinc - carbon cell was investigated. This modification improved all of operational parameters of the cell, e.g. voltage
stability during discharge and electrical capacity of the cathode. Additionally, the use of RVC as both anode and cathode active
masses holder in the Zn|ZnSO4|MnO2 battery system, allowed us to construct a new rechargeable battery system.
Keywords: zinc-carboncell, carbon, rechargeable zinc-manganese dioxide cell, reticulated vitreous carbon(RVC)
liness, which are expected from alkaline MnO2 /Zn primary
cells, are also a feature of RAM batteries [1-4].
It is well known that the main problem with storage
and operating of RAM battery in alkaline media are: zinc
corrosion and the formation of the electrochemically inactive products of manganese dioxide reduction [1-4]. In the
1990’s the aqueous ZnSO4 solution has been exploited as a
replacement for the conventional alkaline electrolytes with
some promising results [5-7]. The literature data shows
that in aqueous ZnSO4 electrolyte discharge and charge reactions of anode (Zn) and cathode (MnO2 ) are reversible.
Additionally, manganese dioxide can be discharged and
charged up to two-electron capacities.
In a series of papers [8-15] we demonstrated that reticulated vitreous carbon (RVC) can be used as reactive mass
carrier and the current collector in lead — acid batteries
[8,9], zinc — carbon batteries [11-15] and secondary cells
with NiOOH/Ni(OH)2 cathode [10].
In this paper we demonstrate the behavior of the primary zinc — carbon cell and a secondary battery system
(Zn|ZnSO4 |MnO2 ) with a new current collector. The traditional carbon (graphite) rod used normally in the cell
for the cathodic current collector has been substituted by
RVC. In our construction, RVC is used as the current collector and the carrier for the cathodic active mass for primary cell and as the current collector and the carrier for
the both anodic and cathodic active masses for secondary
cell.
1. INTRODUCTION
The zinc — manganese dioxide batteries have been well
known since 1866. The two types of zinc manganese dioxide cells that are the most popular now are: zinc chloride
and alkaline system [1,2]. These batteries are characterized as having low cost, ready availability and acceptable
performance for a great number of applications, strictly related to the properties of the cathode material (manganese
dioxide). These properties include: availability, relatively
low price, environment friendly, favorable charge density
and electrode potential.
The primary battery system was constantly improved
from the beginning of its discovery. Till the 60’s of the
last century, in every twenty years the electrical capacity
was increased by 100%. From the 80’s, it was established
that the capacity of zinc — manganese systems reached a
theoretical value [1].
The change of a primary manganese dioxide battery system into a secondary battery type was a technical challenge. In early 1980’s a new rechargeable alkaline manganese dioxide (RAM) was developed [1-4]. Over the
next few years, advancements of this technology has progressed rapidly. Intensive research activities [4] has resulted in considerable improvements. The cycle capacity has been more than doubled and mercury addition to
the anode has been eliminated. Today, the excellent shelf
life, high-temperatures performance, environmental friend∗ To
whom correspondence should be addressed: E-mail:
aczcrw@chem.uw.edu.pl, Fax: -48 22 82 25996
333
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Zbigniew Rogulski et al. / J. New Mat. Electrochem. Systems
2. EXPERIMENTAL
2.1. Materials
All chemicals were high quality grade. They were used
without further purification. The electrolyte was prepared from de-ionized water (Millipore) and from ZnCl2
(POCh, Poland), ZnSO4 (POCh, Poland), MnSO4 (POCh,
Poland), ZnO (POCh, Poland), and NH4 Cl (POCh,
Poland). The electrolyte for zinc — carbon cell contained
the substrates at concentrations given by the following
weight ratio (NH4Cl/ZnCl2/ZnO/H2O): 28/16/0.5/53.5.
The electrolyte for zinc sulphate battery contained the substrates concentrations given by the following weight ratio
(ZnSO4/MnSO4/H2O): 22/0.5/67.5.
The high—powered cell cathode contained the electrolytic
manganese dioxide to acetylene black dioxide in the weight
ratio of 45:1. The anode for secondary battery system
contained the following weight ratio of zinc to acetylene
black: 99/1. The commercially available elements needed
for batteries construction: AA size zinc cups and D size
steel cups, separators saturated with electrolyte, gaskets
and all construction elements mentioned above have been
supplied by CLAiO and Danish Polish Batteries (DPB).
2.2. Discharge measurements
Discharge measurements of the new zinc - carbon battery
were performed using procedures required by the international norms for zinc - manganese primary cells (IEC 861+A#) based on zinc chloride electrolyte (“Heavy Duty”
type). For comparison, a number of commercial HD batteries have been tested with the same procedures. The
discharge modes comprised the following tests:
• open circuit voltage (OCV) measurements.
norm is max. 1.725V
IEC
• 43 Ω discharge, simulated the work of portable radio
receivers (4 hours daily till 0.9 V). IEC norm is 27h
• 10 Ω discharge, simulated the work of portable tape
recorders and players (1 hours daily till 0.9 V). IEC
norm is 4h
• 3.9 Ω discharge, simulated the work of electric toys
(1 hour daily till 0.8 V). IEC norm is 1h
• 1.8 Ω discharge, simulated the work of flashlight (15
seconds per minute impulses till 0.9 V). IEC norm is
75 impulses
• leakage test before and after full discharge.
Discharge/charge tests of secondary battery system
(ZZn|ZnSO4 |MnO2 ) were performed using galvanostatic
technique with AUTOLAB 30 (Eco Chemie B.V Netherland) electrochemical analyzer. Scanning electron microscope LEO 435 VP was used to study the morphology of
the reticulated vitreous carbon.
Figure 1. Scanning electron microscopy picture of RVC,
magnification 100×.
3. RESULT AND DISCUSSION
3.1. Reticulated Vitreous Carbon (RVC)
Initially, reticulated vitreous carbon (RVC) was designed
as an acoustic isolator, but quickly it was applied as an
electrode material in electrochemistry. RVC is an open
pore foam material composed solely of vitreous carbon i.e.
glass-like carbon which combines some of the properties
of electron-conductive glass with some of those of normal
industrial carbons. Fig. 1 shows the morphology of RVC.
This material is available in several porosity grades from
5 to 1400 pores per inch (ppi) i.e. the pores have the sizes
from ca. 0.01 to 2.5mm. Its porous, honeycomb structure provides low density, high surface area, unusual rigid
geometry and a free void volume between 90% and 97%
depending on the ppi grade.
Application of RVC in the construction of electrochemical power sources may distinctly improve their characteristics. The two main advantages of this material: large
surface area and good electric contact with the electroactive species leads to the increase of the current density of
the discharching cell.
Based on the earlier works [11-15], we have used RVC of
20 ppi (pores per inch) porosity in the construction of the
modified zinc manganese dioxide cells.
3.2. Cell construction
The discharge mechanism of the zinc — carbon cell is
complex and there are products of the electrode reactions
such as ammonia complexes and oxychloride species which
are insoluble [1,2]. Precipitation of these compounds increases cell resistance. Insoluble complexes of zinc form a
solid layer between the anode and cathode of the cell. It
prevents the ion transport between the electrodes, which
would normally generate great pH changes. This is also
the reason for the rise of the concentration of the electrode
New Generation of the Zinc — Manganese dioxide cell
/ J. New Mat. Electrochem. Systems
Figure 2. Cross section of the modified zinc — carbon cells:
1. Carbon electric contact, 2. Plastic sleeve and closure,
3. RVC filled with MnO2 , acetylene black and electrolyte,
4. Separator, 5. Zinc can.
reaction products in the anode and the cathode areas. Figure 2 shows the construction details of the modified zinc —
carbon batteries.
In the classical cylindrical battery zinc can serve as the
cell container and the anode. The manganese dioxide is
mixed with carbon additives (e.g. acetylene black), wet
with electrolyte and compressed under pressure to form
a bobbin. A carbon rod is inserted into the bobbin and
serves as the current collector for the positive electrode.
The separator can be starch or a polymer coated absorbent
Kraft paper [2].
Compared to the standard construction of a round cell,
our battery contains a different type of the cathode [6]. We
have used reticulated vitreous carbon as a cathode current
collector and active mass holder. In this instance, each
pore of RVC acts as a semiseparate cell. If an unwanted
reaction take places in this semi cell e.g. precipitation of
insoluble compounds, only this small part of the cathode
area is switched off. Additionally, the carbon rod was significantly shortened just to function as the electric contact
between the porous current collector (RVC) and the outside battery pole (+). Due to this modification the amount
of the cathodic active mass (MnO2 + carbon black) has
been increased by ca. 10% and, in consequence, also the
electrical capacity has been raised.
Figure 3 shows the construction details of the modified
Zn|ZnSO4 |MnO2 secondary battery system.
In the proposed cell construction reticulated vitreous
carbon is used as the anode and cathode current collector. The mixture of manganese dioxide, acetylene black,
335
Figure 3. Cross section of the new rechargeable zinc — manganese dioxide cells: 1. Steel can (positive battery pole),
2. RVC filled with MnO2 , acetylene black and electrolyte,
3. Separator, 4. RVC filled with Zn, acetylene black and
electrolyte, 5. Anode current collector, 6. Closure.
and electrolyte based on zinc sulfate is pressed into RVC
ring. This electrochemical system (cathode) has a?? direct
contact with the steel can which is the positive cell’s pole.
In the middle of the cell there are RVC filled with mixture of zinc, acetylene black and electrolyte. The anode is
isolated from the cathode by paper separator soaked with
electrolyte that promotes ionic or electric conductivity.
3.3. Discharge/charge measurements
Fig. 4 shows the continuous discharge curve of modified zinc — carbon cell under the 43 Ω load. The obtained
discharge curve is characterized by a well-shaped plateau
and a longer discharge compared to normal batteries. It
is connected with the increased loading of cathodic active
mass.
Figs. 5 a-d show the discharge time of modified zinc
— carbon cell and commercial „Heavy Duty” batteries obtained in different test modes according to the IEC norms.
The modified zinc — carbon cell performed best in test
simulating the operation in portable radio receivers (43Ω
load) and electric toys (3.9Ω load). Only the results obtained in the test mode simulating flashlights were significantly behind those for the HD batteries but were still
satisfying international norms. The open circuit voltage
(OCV) measured for fresh batteries exceeded the international norms by ca. 0.025 V. This result is related to
the increase of manganese dioxide concentration in the cathodic mass. Another reasons could be higher purity of
chemicals used in our work in comparison to standard batteries or less internal resistivity. The OCV value did not
change during three-months storage. One of the results
of the RVC application as the cathodic active mass holder
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a
b
c
d
Figure 5. Discharge time parameters of zinc — carbon cells and commercial HD batteries in comparison to IEC norms.
Test modes: a. 43 Ω load, b. 10 Ω load, c. 3,9 Ω load, d. 1,8 Ω load.
Figure 4. Continuous discharge curves of zinc — carbon
cells under 43 Ω load.
was the change in the cathode constitution. It is commonly known that the amount of carbon additives used in
the commercial zinc — carbon batteries is about 9% (based
on the total weight of cathode material). Fig. 6 shows the
discharge curves for the modified zinc - carbon cell with
various concentrations of Acetylene Black in the cathodic
mixture in the 43 Ω test modes.
The decrease of carbon additives constitution (the conductive and electrolyte holding material) to the amount of
1.5% based on the total weight of cathode has not increased
the cell resistance. In consequence, the discharge time of
the modified cell rose by 15% in comparison to commercial
HD batteries.
The zinc — manganese dioxide rechargeable cells employing zinc as the anode and manganese dioxide as the
cathode have disadvantages connected with used materials [1,2]. Zinc is dissolved unevenly and irregularly during
the storage and discharging period. As a result, the zinc
electrode surface will become rougher with the progress of
the discharge, and the zinc electrode will become deformed.
Additionally, during the charging period, zinc deposits in a
tree-branch form. The dendrite will grow toward the cathode ultimately penetrating the separator and causing an
internal short-circuit. In addition to the above-mentioned
New Generation of the Zinc — Manganese dioxide cell
/ J. New Mat. Electrochem. Systems
337
Figure 6. Continuous discharge curves, under 43 Ω load
of zinc — carbon cells with various amounts of Acetylene
Black in the cathodic mixture.
problems related to zinc electrodes, there is a problem related to the operation of the manganese dioxide cathodes
caused by the irreversibility of cathodic processes. It is
connected with the loss of electrochemical activity of oneelectron discharge product (MnOOH). The causes of this
irreversibility can be explained in many ways including the
loss of surface conductivity, the increase of internal resistance of the reaction intermediate or product, and the production of Mn2 O3 , Mn3 O4 or ZnOMn2 O3 .
The use of reticulated vitreous carbon as the cathode
and anode materials holder allow us to avoid of these problems. The zinc sulfate electrolyte with manganese sulfate
addition applied in the presented cell construction makes
possible a two-electron reduction of manganese dioxide.
During the discharging period, manganese dioxide in a
solid state is reduced to manganese ion (II) in an aqueous
solution state (reaction in which two electrons are involved
with regard to one manganese atom). During the charging
period, the reverse reaction proceeds [5-7].
Fig. 7 shows the continuous discharge curve of new zinc
— manganese dioxide cell on the 50 mA and 30 mA drain.
The obtained discharge curves are characterized by a wellshaped plateau.
Fig 8 shows the discharge/charge curves at constant current of 30 mA. As mentioned above, the porous structure
of the used carbon material allow us to improve the charge
characteristics of the new zinc — manganese dioxide cell.
The obtained results are promising and we are working on
the optimization of this parameter.
Figure 7. Continuous discharge curves, under 30 mA and
50 mA draw, of the new rechargeable zinc — manganese
dioxide cell based on zinc sulfate electrolyte.
Figure 8. Discharge and charge curves, under 30 mA draw,
of the new rechargeable zinc — manganese dioxide cell based
on zinc sulfate electrolyte.
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4. CONCLUSION
The use of reticulated vitreous carbon as the cathode
and the carrier of cathodic active mass in the zinc — carbon
cell improved all its operation parameters. The changes
made the modified cell competitive for the better-classified
batteries “Heavy Duty” batteries. Additionally, the application of RVC in the zinc — manganese dioxide cell based
on zinc sulfate electrolyte allow us to avoid main disadvantages of standard zinc - manganese dioxide system e.g.
dissolution of Zn, dendritic grow of Zn during charging,
separator penetrating, and the loss of electrochemical activity of the reduction products. The constructed rechargeable batteries based on the zinc sulfate electrolyte showed
promissing results.
5. ACKNOWLEDGEMENT
This work was financially supported by the Polish Science Fund and The Ministry of Science and Information
Society Technologies through grant No. 3T09A 107 26.
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