AN ENERGY STORAGE DEVICE AND METHOD THEREOF
TECHNICAL FIELD
The present disclosure is related to hybrid capacitors specifically to PbO2/Activated Carbon
hybrid ultracapacitors. The hybrid ultracapacitor of the present disclosure is simple to assemble,
bereft of impurities and can be fast charged/discharged with high faradiac efficiency.
BACKGROUND
Supercapacitors (also termed as ultracapacitors) are being projected as potential devices that
could enable major advances in energy storage. Supercapacitors are governed by the same
physics as conventional capacitors but utilize high-surface-area electrodes and thinner dielectrics
to achieve greater capacitances allowing energy densities greater than those of conventional
capacitors and power densities greater than those of batteries. Supercapacitors can be divided
into three general classes, namely electrical-double-layer capacitors, pseudocapacitors and
hybrid capacitors. Each class is characterized by its unique mechanism for charge storage,
namely faradaic, non-faradaic and the combination of the two. Faradaic processes, such as
oxidation-reduction reactions, involve the transfer of charge between electrode and electrolyte as
in a battery electrode while a non-faradaic mechanism does not use a chemical mechanism and
rather charges are distributed on surfaces by physical processes that do not involve the making or
braking of chemical bonds "similar to electrical "double-layer. A hybrid supercapacitor combines
a battery electrode where the energy is stored in chemical form and an electrical-double-layer
electrode where the energy is stored in physical form. A PbO2/Activated Carbon supercapacitor
comprises a positive plate akin to a lead acid cell and a high surface-area activated carbon
electrode as negative plate. The charge- discharge reactions at the positive and negative plates of
such a hybrid supercapacitors are as follows.
(+) plate: PbSO4+2H2O↔PbO2 + H2SO4 + 2H+ + 2e-
(-) plate: 2C + 2H++2e-↔2(C-Hads
+)dl
Accordingly, the net charge-discharge reactions for the hybrid supercapacitor can be written as
follows.
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PbSO4+2H2O+2C↔PbO2+ H2SO4+2(C-Hads
+)dl
The (+) plate is realized by electrochemical plating and cycling in sulpuric acid/ perchloric
acid while the (-) plate is prepared by pasting activated carbon onto a lead sheet. The said
hybrid supercapacitor stores energy both in chemical and physical forms.
The hybrid capacitors known in the prior art employ conventional PbO2 plates that require
sizing and mixing of the active materials of - appropriate compositions, pasting, drying, curing
and formation. Such electrodes are not fully amenable to fast charge/discharge processes
desirous of a capacitor.
STATEMENT OF DISCLOSURE
The present disclosure is in relation to an energy-storage device (1) comprising: a substrateintegrated-
lead-dioxide electrode (2), an activated-carbon electrode (3), and a separator (4)
soaked in an electrolyte (5) and placed in-between the substrate-integrated-lead-dioxide electrode
and the carbon electrode in a container (6); an energy storage device (7) comprising plurality of
energy storage device (1) of claim 1 connected in series; a method of preparing substrateintegrated
lead dioxide comprising acts of, a) etching pre-polished lead sheets; b) washing the
etched lead sheets with deionized water; c) immersing the washed lead sheets in mixture of
sulphuric acid and perchloric acid to obtain a layer of lead sulphate; and d) oxidizing the lead
sulphate to lead dioxide to obtain substrate-integrated lead dioxide; a method of manufacturing
an energy storage device (1), comprising acts of: a) preparing substrate-integrated-lead-dioxide
electrode (2), b) preparing activated-carbon electrode (3), and c) mounting the substrateintegrated-
lead-dioxide electrode (2), the activated-carbon electrode (3) in a container (6) with
separator (4) soaked in an electrolyte (5) in-between the substrate-integrated-lead-dioxide and
the carbon electrodes to manufacture the energy-storage device; a method of using energystorage
device (1 or 7), said method comprising act of conjugating said energy-storage device
with electrical device for generating electrical energy to devices in need thereof for working.
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1: Schematic diagram of substrate-integrated PbO2/activated-carbon ultracapacitor.
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Figure 2: Schematic diagram of substrate-integrated PbO2/activated-carbon ultra capacitors
connected in series.
Figure 3: Schematic diagram of electrochemical cell employed for preparing substrate-integrated
PbO2 electrodes.
Figure 4: XRD patterns for the positive electrodes.
Figure 5: Cyclic voltammograms for a PbO2/Activated Carbon Hybrid Ultracapacitor.
Figure 6: Constant current charge/discharge cycles.
Figure 7: Life-cycle test.
Figure 8: Constant current charge/discharge characteristics.
Figure 9: Constant-potential charge and constant-current discharge characteristics.
Figure 10: Cycle-life test for PbO2/PVDF-bonded Activated-Carbon Hybrid Ultracapacitor.
Figure 11: Constant-current discharge characteristics for 6V/40F PbO2/Activated Carbon Hybrid
Ultracapacitor.
DESCRIPTION OF DISCLOSURE
The present disclosure is in relation to an energy storage device (1) comprising:
a) a substrate-integrated-lead-dioxide electrode (2),
b) an activated-carbon electrode (3), and
c) a separator (4) soaked in an electrolyte (5) and placed in-between the substrateintegrated-
lead-dioxide electrode and the carbon electrode in a container (6).
In an embodiment of the present disclosure, the energy storage device (1) is a hybrid capacitor.
In still another embodiment of the present disclosure, the separator (4) is made of material
selected from a group comprising porous glass and porous polymers, preferably porous glass.
In yet another embodiment of the present disclosure, the electrolyte is selected from a group
comprising sulphuric acid, methanesulfonic acid, perflurosulphonic acid, and preferably
sulphuric acid.
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In yet another embodiment of the present disclosure, the sulphuric acid is concentrated in range
from about 4M to about 7M, preferably about 6M.
In yet another embodiment of the present disclosure, the energy storage device (1) is of faradiac
efficiency ranging from about 94% to about 96%, preferably 95%.
The present disclosure is also in relation to an energy-storage device (7) comprising plurality of
energy-storage device (1) connected in series.
The present disclosure is also in relation to a method of preparing substrate-integrated lead
dioxide comprising acts of,
a) etching pre-polished lead sheets;
b) washing the etched lead sheets with deionized water;
c) immersing the washed lead sheets in mixture of sulphuric acid and perchloric acid
to obtain a layer of lead sulphate; and
d) oxidizing the lead sulphate to lead dioxide to obtain substrate integrated lead
dioxide.
In still another embodiment of the present disclosure, the etching is carried out using Nitric acid.
In yet another embodiment of the present disclosure, the Nitric acid is of concentration ranging
from about 0.5M to about 1.5M, preferably about 1M.
In yet another embodiment of the present disclosure, the sulphuric acid is concentrated in the
range from about 4M to about 7M, preferably about 6M.
In yet another embodiment of the present disclosure, the perchloric acid is concentrated in the
range from about 0.05M to about 0.2M, preferably about 0.1M.
In yet another embodiment of the present disclosure, the oxidation of lead sulphate to lead
dioxide is by using the lead sulphate as an anode in an electrochemical cell.
The present disclosure is also in relation to a method of manufacturing an energy-storage device
(1), comprising acts of:
a) preparing substrate-integrated-lead-dioxide electrode (2),
b) preparing activated carbon electrode (3), and
c) mounting the substrate-integrated-lead-dioxide electrode (2), the activated carbon
electrode (3) in a container (6) with separator(4) soaked in an electrolyte (5) inbetween
the substrate-integrated lead dioxide and the carbon electrode to
manufacture the energy storage device.
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In yet another embodiment of the present disclosure, the container (6) is made of material
selected from a group comprising porous glass and porous polymer, preferably porous glass.
The present disclosure is also in relation to a method of using energy-storage device (1 or 7), said
method comprising act of conjugating said energy-storage device with electrical device for
generating electrical energy to devices in need thereof for working.
The present disclosure is related to realizing substrate-integrated PbO2/Activated-carbon hybrid
ultracapacitor bereft of impurities. The hybrid ultra capacitors of the present disclosure are
simple to assemble, bereft of impurities, and can be fast charged / discharged with faradaic
efficiencies as high as 95%.
In the current disclosure, the positive electrodes, substrate-integrated PbO2 are made by
electrochemical formation of pre-polished and etched lead metal sheets. Specifically, the
substrate-integrated PbO2 is obtained by oxidizing PbSO4 which is formed when lead sheets
come in contact with sulfuric acid. Subsequent to their formation, the electrodes are washed
copiously with de-ionized water to wash off all the impurities. The XRD patterns for the formed
electrodes were recorded and found to be free of impurities. The XRD patterns provided in the
figure 4 clearly suggest the formation of lead dioxide. The negative electrode is an activated
carbon electrode.
In the current disclosure of PbO2/Activated carbon hybrid ultracapacitor, PbO2 electrode is a
battery-type electrode and activated carbon is a double-layer-capacitor electrode. Figure 5 is a
cyclic voltammogram for PbO2/activated carbon hybrid ultracapacitor at a scan rate of 10 mV/s
showing a peak for the oxidation of PbSO4 to PbO2 at 2V during the anodic scan and the
corresponding reduction of PbO2 to PbSO4 at 1.5V during the cathodic scan. The oxidation and
reduction peaks reflect the PbO2/Activated carbon to be a hybrid device.
Generally, the battery electrodes are charged at C/10 rate (10h duration) and discharged at C/5
rate (5h duration). If the battery electrodes are charged/discharged at C rate or at higher rates
their cycle-life is affected. Faradaic efficiency of the battery electrodes depends on the particle
size of the active materials, porosity of the electrode, internal resistance of the electrode, etc. The
battery electrodes have low faradaic efficiency.
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The present disclosure provides, electrochemically formed and substrate-integrated PbO2 as
battery-type electrode that can be charged and discharged at higher rates with faradiac
efficiencies as high as 95%. The same has been illustrated in Figure 8. The figure 8 shows
current charge and discharge curve at 50 mA for the substrate-integrated PbO2/Activated hybrid
ultracapacitor exhibiting faradiac efficiency as high as 95%.
Figure 6 shows the charge and discharge polarization curves at 25 mA, 50 mA and 100 mA for a
substrate-integrated PbO2/Activated carbon hybrid ultracapacitor prepared by using Teflon as
binder in the carbon electrodes. The capacitance is calculated from the discharge curve using the
equation:
C(F) = I(A) x t(s)/(V2-V1)
where V2 is the voltage at the beginning of discharge and V1 is the voltage at the end of
discharge. It is found that the hybrid ultracapacitor has a capacitance of 10.79F at 25mA, 10.05F
at 50 mA and 9.738F at 100 mA.
The figure 7 shows the cycle-life data for the substrate-integrated PbO2//Activated carbon hybrid
ultracapacitor at 0.1 A suggesting the hybrid ultracapacitors to have high cycle-life. The cyclelife
test involves the following four steps.
Step 1. Charging the ultracapacitor at 2.3V for 10 min.
Step 2. Open-circuit voltage measurement for 5s.
Step 3. Discharge the ultracapacitor at constant current at 0.2A.
Step 4. Open-circuit voltage measurement for 30s.
Figure 10 shows the cycle-life data for the substrate-integrated PbO2/Activated-carbon hybrid
ultracapacitor.
Figure 9 illustrates the discharge curves at varying currents for the substrate-integrated
PbO2/Activated-carbon hybrid ultracapacitor followed by their charging at 2.3V for 10min.
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The hybrid capacitor of the present disclosure is connected in series to obtain capacitors wherein
the cell voltage gets added up while their effective capacitance decreases akin to conventional
capacitor. Figure 11 shows the discharge curves at 0.2A current for substrate-integrated
PbO2/Activated-carbon hybrid ultracapacitor cell comprising two and three cells connected in
series. The figure indicates that the cell voltage is added up when two or more cells are
connected in series while their effective capacitances decrease akin to conventional capacitors.
The method of manufacturing substrate-integrated PbO2/activated-carbon hybrid ultracapacitor
(1) essentially comprises: preparing substrate integrated lead dioxide electrode (2), preparing
activated-carbon electrode (3), and mounting the substrate-integrated-lead-dioxide electrode (2),
the activated-carbon electrode (3) in a container (6) with separator(4) soaked in an electrolyte (5)
in-between the substrate-integrated lead dioxide and the carbon electrode to manufacture the
energy-storage device.
The devices of the present disclosure can be easily conjugated with electrical devices for
generating electrical energy to devices in need thereof for working.
The technology of the instant application is elaborated in detail with the help of following
examples. However, the examples should not be construed to limit the scope of the disclosure.
Example:
Preparation of substrate-integrated PbO2/Activated Carbon Hybrid Ultracapacitors
A. Preparation of Substrate-Integrated PbO2 Electrodes.
Substrate-integrated- PbO2 electrodes are prepared by etching pre-polished lead sheets (thickness
300 μm) in 1M HNO3 for 60s and subsequently washed copiously with deionized water. The
sheets were then immersed in 6 M aqueous H2SO4 with 0.1 M HClO4 as additive at room
temperature. On immersing in aqueous sulfuric acid, a thin layer of lead sulfate is formed on the
surface of the lead sheet which is oxidized to PbO2 by using it as anode in an electrochemical
cell fitted with a counter electrode. The process is repeated for about five times to prepare the
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fully-formed substrate-integrated PbO2 electrodes. The electrochemical cell employed for this
purpose is connected to a constant current dc supply as shown schematically in figure3.
B. Preparation of PVDF bonded activated carbon electrodes.
Activated-carbon electrodes are prepared by pasting activated carbon ink containing
polyvinylidene difluoride as a binder. In brief, a carbon paste was obtained by mixing 85% of
high-surface-area carbon (BET surface area is about 2000 m2/g and particle size < 10 nm) with
10 wt. % of carbon black (particle size is about 1 μm) and 5 wt. % of binder like PVDF
dissolved in an appropriate quantity of dimethylformamide solvent or teflon. Typically, 0.1 g of
PVDF is dissolved in 10 ml of DMF and 1.7 g of high surface area carbon (Meadwestvaco
090177) and 0.2 g of carbon black was added. The mixture was mixed well in an ultrasonicator
for 5 min. The resulting carbon ink was brush coated onto two graphite electrodes of area 3.5 cm
x 6.0 cm with that had a tag area of 1cm width and 3 cm length. The carbon paste was applied on
both sides of the carbon electrodes so that each side of the electrode in order to get a 0.5 g of
active material. Then the electrodes were dried in air oven for overnight (about 10 h) at 80oC.
C. Assembly of Substrate-Integrated PbO2-AC Hybrid Ultracapacitors (HUCs)
a) 6V substrate-integrated PbO2-AC hybrid ultracapacitor.
6V substrate-integrated PbO2-AC HUCs were assembled by connecting three 2V HUCs in series.
2V/100F substrate-integrated PbO2/PVDF-bonded AC HUCs comprising a substrate-integrated
PbO2 electrode of size 3.5cm x 6 cm with a tag of 1cm width and 3 cm length formed by
aforementioned method and a PVDF-bonded carbon electrode prepared as described above were
assembled using a 3 mm thick AGM (adsorbed glass mat) soaked with 6 M H2SO4 acid as the
separator and electrolyte. The complete assembly, PbO2 - (AGM+H2SO4) - AC, was then
assembled into a plexiglass container. The cell was then tested for its electrochemical
characteristics.
b) 12V substrate-integrated PbO2-AC hybrid ultracapacitor.
12V PbO2-AC HUCs were assembled by connecting six HUCs in series. The details for
assembling the HUCs are given as under.
1 0
2V/100F substrate-integrated PbO2/PVDF-bonded AC HUCs comprising a substrate-integrated
PbO2 electrode of size 3.5cm x 6 cm with tags (6a, 6b) of 1cm width and 3 cm length formed by
aforementioned method and a PVDF-bonded carbon electrode prepared as described above were
assembled using a 3 mm thick AGM (adsorbed glass mat) soaked with 6 M H2SO4 acid as the
separator and electrolyte. The complete assembly, PbO2 - (AGM+H2SO4) - AC, was then
assembled into a plexiglass container. The cell was then tested for its electrochemical
characteristics.
c) 12V substrate-integrated PbO2-AC hybrid ultracapacitor.
A 12V substrate-integrated PbO2/Activated carbon hybrid ultracapacitor was realized by
connecting six single cells in series in a commercial lead-acid battery container. Each cell of this
12V hybrid ultracapacitor comprises 9 positive and 8 negative plates of size 4.5cm x 7 cm with
the tag (6b) area of 0.5cm x 0.5 cm and 0.3mm thickness for the positive plate and 0.8mm
thickness for negative plates (6a); 1mm thick AGM sheets were used as separator. A unique
method was used to interconnect the graphite electrodes. The tag portion of the negative
electrodes (6a) is electroplated with Tin followed by electroplating with lead which facilitates the
graphite electrode tags (6b) to solder with each other. The graphite electrodes in each cell were
soldered with lead by torch-melt method using an appropriately designed group-burning fixture.
Subsequently, the cells were interconnected in series.
It is found that these hybrid ultracapacitors yield a capacitance value of 120F at 5C rate of
discharge.
While various aspects and embodiments have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The various aspects and embodiments
disclosed herein are for purposes of illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following claims.

WE CLAIM:

1.An energy storage device (1) comprising:
a) a substrate-integrated-lead-dioxide electrode (2),
b) an activated carbon electrode (3), and
c) a separator (4) soaked in an electrolyte (5) and is fixed in-between the substrateintegrated-
lead-dioxide electrode and the carbon electrode in a container (6).

2.The energy-storage device as claimed in claim 1, wherein the energy storage device (1) is a
hybrid capacitor.

3.The energy-storage device as claimed in claim 1, wherein the separator (4) is made of material
selected from a group comprising porous glass and porous polymers, preferably porous glass.

4. The energy-storage device as claimed in claim 1, wherein the electrolyte is selected from a
group comprising sulphuric acid, methanesulfonic acid, perflourosulphonic acid, preferably
sulphuric acid.

5. The energy storage device as claimed in claim 4, wherein the sulphuric acid is concentrated in
range from about 4M to about 7M, preferably about 6M.

6. The energy storage device as claimed in claim 1, wherein the energy storage device (1) is of
faradiac efficiency ranging from about 94% to about 96%, preferably 95%.

7. An energy storage device (7) comprising plurality of energy storage device (1) of claim 1
connected in series.

8. A method of preparing substrate-integrated-lead-dioxide comprising acts of,
a. etching pre-polished lead sheets;
b. washing the etched lead sheets with deionized water;
c. immersing the washed lead sheets in mixture of sulphuric acid and perchloric acid to obtain
a layer of lead sulphate; and
d. oxidizing the lead sulphate to lead dioxide to obtain substrate-integrated lead dioxide.

9. The method of preparation of substrate-integrated lead dioxide as claimed in claim 8, wherein the etching is carried out using nitric acid.

10. The method of substrate-integrated lead dioxide as claimed in claim 9, wherein the nitric
acid is of concentration from about 0.5M to about 1.5M, preferably about 1M.

11. The method of preparation of substrate integrated lead dioxide as claimed in claim 8, the sulphuric acid is concentrated in the range from about 4M to about 7M, preferably about 6M.

12. The method of preparation of substrate integrated lead dioxide as claimed in claim 8,
wherein the perchloric acid is concentrated in the range from about 0.05M to about 0.2M,
preferably about 0.1M.

13. The method of preparation of substrate-integrated lead dioxide as claimed in claim 8,
wherein the oxidation of lead sulphate to lead dioxide is by using the lead sulphate as an anode in an electrochemical cell.

14. A method of manufacturing an energy storage device (1), comprising acts of:
a) preparing substrate-integrated lead dioxide electrode (2),
b) preparing activated carbon electrode (3), and
c) mounting the substrate-integrated lead dioxide electrode (2), the activated carbon
electrode (3) in a container (6) with separator(4) soaked in an electrolyte (5) inbetween
the substrate-integrated lead dioxide and the carbon electrode to manufacture the energy storage device.

15. The method as claimed in claim 14, wherein the container (6) is made of material selected
from a group comprising porous glass and porous polymer, preferably porous glass.

16. A method of using energy-storage device (1 or 7), said method comprising act of conjugating said energy-storage device with electrical device for generating electrical energy to devices in need thereof for working.