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Description  |
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FIELD OF INVENTION
The present invention relates to a permanently doped polyaniline and its
method of production. More specifically, the present invention relates to
a permanently doped polyaniline as a film and its production by the
electropolymerization of a solution of aniline and an organic dopant, such
as an organic sulfonate, and the use of the film in electrical
transmission and storage, e.g. as an electrode in an advanced electrical
storage battery.
DESCRIPTION OF RELATED ART
During the last five years, a great deal of effort has been expended to
develop polyaniline-based rechargeable polymer batteries, especially in
conjunction with a lithium anode in nonaqueous electrolytes. The doping
rate of polyaniline is about twice that of any other conducting polymers,
and the stability of polyaniline is probably the best. Recently, the first
commercial, coin-shaped polyaniline/lithium battery suitable as a memory
back-up power source was developed by T. Kita et al. for
Bridgestone/Seiko. See "Properties of Polyaniline Secondary Battery,"
Abstract No. 24, 170th Electrochemical Society Meeting, San Diego, Calif.,
October 1986. Table 1 summarizes typical performance characteristics of
three secondary battery systems (i.e. lead-acid, nickel-cadmium, and
Bridgestone's new polyaniline battery).
The following references relate to Table 1:
A. G. MacDiarmid et al. (1986), Extended Abstracts, Vol. 86, Abstract #2,
170th Electrochemical Society Meeting, San Diego, Calif., October 19-24.
A. Kitani et al., (1986), Journal of the Electrochemical Society, Vol 133,
#6, pp. 1069-1073.
N. Koura et al., Denki Kagaku, Vol. 55, #5, pp. 386-391.
TABLE 1
__________________________________________________________________________
COMPARISON OF DIFFERENT POLYANILINE ELECTRODES
MacDiarmid
Kitani
and Yang
et al. Koura and Kijima
SRI
(1986) (1986) (1987) (Preliminary data)
__________________________________________________________________________
Polyaniline electrode
powder e.c. polymer
powder powder e.c. polymer
Starting materials
aniline
0.1 M aniline
0.5 M aniline
0.5 M aniline
0.1 M aniline
(NH.sub.4).sub.2 S.sub.2 O.sub.8
0.1 M H.sub.2 SO.sub.4
0.1 M HC1
0.1 M H.sub.2 SO.sub.4
1 M tosylate
Preparation method
chemical
PC.sup.d /Pt
CP.sup.f /graph
CP.sup.f /graph
PC.sup.i /Pt
Weight of polyaniline (g)
-0.04 (2 .times. 2 cm)
5? 5 -0.024
Electrolyte PC/LiCiO.sub.4
1 M ZnSO.sub.4
AlCl.sub.3 BPC.sup.g
0.5 M ZnSO.sub.4
1 M ZnSO.sub.4
(pH 4.6) (pH 2.3)
Anode (negative elec-
Li Zn (beads)
A1 Zn sheet
Zn sheet
trode)
Open-cell voltage (V)
3.3 -1.1 1.7 1.4 1.5
Short-circuit current (mA)
-- -- -- -- 3.0
Capacity (Ah/kg)
147.7.sup.b
<108 130 100 -36
Capacity.sup.a (Ah/kg)
92.7 -- -- -- --
Power density (kW/kg)
-- -- -- -- 0.2
Energy density (Wh/kg)
539.2.sup.a
<111 180 -140 -39
Energy density.sup.a (Wh/kg)
338.3 -- -- -- --
Coulomb efficiency (%)
-- 100.sup.e
85-90.sup.h
-85.sup.i
-86.sup.k
Cycle life (cycles)
-- <2000.sup.e
-60.sup.h
<60.sup.i
>400.sup.l
Self-discharge rate
57 -- 6 -- high
(%/month)
__________________________________________________________________________
.sup.a Including the weight of electrolyte.
.sup.b Discharge rate of 0.2 mA/cm.sup.2.
.sup.c At an average discharge voltage of 3.65 V.
.sup.d Potential cycle (100 mV/s) for 1000 times between -0.2 and +0.8 V
vs. SCE.
.sup.e Cycled between 1.35 V and 0.75 V at a constant current density of
mA/cm.sup.2.
.sup.f Constant potential of 1 V vs. SCE for 72 hours using graphite
electrode.
.sup.g 2:1 mixture of AlCl.sub.3 and lbutylpyridinium chloride.
.sup.h At .+-.4 mA/cm.sup.2.
.sup.i At .+-.2 mA/cm.sup.2.
.sup.j Potential cycle (100 mV/g) for 4 hours between -0.2 V and +0.8 vs
SCE at 30.degree. C.
.sup.k Cycled between 1.35 V and 0.75 at .+-.10 mA/cm.sup.2.
.sup.l At .+-.10 mA/cm.sup.2.
The T. Kita/Bridgestone polyaniline battery offers attractive
characteristics such as high operating voltage, good cycle life and low
self-discharge rate. In addition, polyaniline batteries in general appear
to be intrinsically superior to other existing secondary batteries because
of potentially high charge capacity and high energy density (features not
yet realized in the Bridgestone battery). Furthermore, although the
polyaniline/lithium nonaqueous battery developed by Bridgestone/Seiko is
said to exhibit excellent shelf-life, i.e. little self-discharge, there
are difficulties associated with the use of a nonaqueous solvent (e.g.
propylene carbonate) in conjunction with a lithium electrode in
rechargeable batteries, including:
1. Low capacity (less than 0.004 Ah) and low current output (less than
5mA).
2. Corrosion is a problem: the lithium surface is gradually covered by some
passive film such as Li.sub.2 CO.sub.3 during the repeated cycling of
charge and discharge.
3. The high cathodic potential of the Li/Li+ couple often causes solvent
decomposition.
Japanese patent application [JP 62/12073] by Hitachi/Showa Denko discloses
the use of tosylate in conjunction with polyaniline. It is apparent that
the two batteries are quite different in terms of their fundamental
principles. The Hitachi/Showa Denko battery is essentially a conventional
polyaniline/Li nonaqueous battery, in which anions such as ClO.sub.4 - are
dopants in the positive polyaniline electrode. The tosylate is used merely
as a sacrificial material (Anions with a larger ionic radius, such as
tosylate, are added during electropolymerization of aniline. The grown
polyaniline film is rinsed thoroughly with water to get rid of the added
anions, leaving the polyaniline with a high microporous channel structure
through which small anions, e.g. ClO-.sub.4, can easily diffuse in and
out).
Organic conducting polymers such as polypyrrole (PPy), polythiophene (PTP),
polyaniline (PAn or PAN) and their derivatives are gaining in popularity
for potential use in optical, electronic and electrochemical devices. See,
for example, F. Garnier et al., Journal of Electroanalytical Chemistry
(1983), Vol. 148, p. 299; H. Kaezuka, et al., Journal of Applied Physics
(1983), Vol. 54, p. 2511; and A. Mohammadi et al., Journal of the
Electrochemical Society (1986), Vol. 133, p. 947.
A major disadvantage of these electrically conducting polymers in any
configuration is that they usually have poor mechanical properties. See,
for example, O. Niwa, et al., Journal of the Chemical Society (1984), p.
817; S. E. Lindsey, et al., "Synthetic Methods," (1984/1985), Vol 10, p.
67; F.R.F. Fan, et al., Journal of the Electrochemical Society, Vol 133,
p. 301; and R. M. Penner, et al., Journal of the Electrochemical Society
(1986), Vol. 133, p. 310.
Several approaches may be useful to improve the physical and mechanical
properties of the conducting polymers. For instance, the polymerization of
pyrrole in thick electroactive polymer networks such as
poly(vinylchloride), poly(vinyl alcohol), NAFION and NAFION.RTM., a
trademark of the E.I. DuPont Co., Inc. of Wilmington, Del., for a
perfluorinated sulfonic acid material and membrane, and
NAFION.RTM.-impregnated GORE-TEX.sup.R, where GORE-TEX.sup.R is a
trademark of W. F. Gore and Associates of Elkton, Md., for a porous
polytetrafluoroethylene material. has been reported in the literature.
T. Harai, et al., Journal of the Electrochemical Society (1988), Vol. 135
(#5), p. 1132-1137 reported that the anodic polymerization of pyrrole,
3-methylthiophene and aniline at NAFION .RTM.-coated electrodes gives
electrically conducting polyaniline (NAFION) composite films. These
composites show an improvement of the polypyrrole electrochromic response
and by the efficient utilization of stored charge by the composite film
electrodes.
All of the disclosure in the references cited herein are incorporated
herein by reference.
These references do not teach or suggest a permanently doped polyaniline
for use as a secondary battery as is described in the present invention.
SUMMARY OF THE INVENTION
The present invention relates to an electrically conducting polymer having
essentially permanent self-doping properties, said polymer comprising:
(a) electrically polymerized polyaniline matrix chemically combined with
(b) an organic dopant having at least one sulfonic acid functional group.
In a preferred embodiment of the present invention, the electrically
conducting polymer combination, the organic dopant is independently
selected from benzenesulfonic acid, toluenesulfonic acid, benzenesulfonyl
chloride, 2-ethylbenzenesulfonic acid, vinyl sulfonic acid,
dodecylbenzenesulfonic acid, poly(vinylsulfonic) acid,
trifluoromethanesulfonic acid, 1-butanesulfonic acid, modified NAFION
.RTM. solution, 2,3,5-trichlorobenzenesulfonic acid or vinylphenylsulfonic
acid or the alkali metal salts thereof.
In another embodiment, the present invention is a method to produce a
water-insoluble polyaniline to which an organic dopant is chemically bound
to the polyaniline, which method comprises:
(a) electropolymerizing aniline in an aqueous solvent which contains the
organic dopant
Additional embodiments are found in the description below and in the claims
.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a schematic diagram of the rechargeable polyaniline battery.
FIG. 2A shows the resistance of various conventional polyaniline films as a
function of gate potential, V.sub.G, between two adjacent
micro-electrodes.
FIG. 2B shows the resistance of permanently doped polyaniline-tosylate
films as a function of gate potential, V.sub.G, between two adjacent
micro-electrodes.
FIG. 3 over all shows typical cyclic voltammograms of aniline during
polymerization and grown polyaniline films in aqueous solution FIG. 3A
shows aniline/sulfuric acid during polymerization on a 3-dimensional
electrode substrate (e.g., fat posts). FIG. 3B shows aniline/tosylate
during polymerization on a 3-dimensional fat posts electrode. FIG. 3C
shows polyaniline/ sulfuric acid film production in aqueous 0.5M sodium
sulfate at pH 1.2. FIG. 3 D shows polyaniline/tosylate film
electropolymerization in aqueous 0.5M sodium sulfate at pH 1.2.
FIG. 4 shows an X-ray fluorescence spectroscopic analysis (EDAX) spectrum
of the polyaniline/tosylate.
FIG. 5 shows a scanning electron micrograph (SEM) of the
polyaniline/tosylate.
FIG. 6 shows a comparison of the long-term charge discharge curves (cell
voltage versus time) at .+-. 10 milliamperes/centimeter2 in 1M zinc
sulfate at pH 2.3. FIG. 6A self-doped polyaniline/tosylate (1M in tosylate
and 0.1 M aniline on a 3-dimensional fat post electrode with a
zinc-dispersed NAFION .RTM. film as an anode. FIG. 6B shows a conventional
(undoped) polyaniline film (0.1M sulfuric acid and 0.1 M aniline) on a
3-dimensional fat COCO electrode with a zinc sheet anode.
FIG. 7 shows the coulomb efficiency and capacity of various polyaniline
electrodes as a function of charge-discharge current density in 1M zinc
sulfate. FIG. 7A shows the coulomb efficiency of the half cell battery.
FIG. 7B shows the capacity when zinc is used as an anode.
FIG. 8 shows the resistance of various polyaniline films as a function of
gate potential, V.sub.G, between two adjacent platinum electrodes.
FIG. 9 shows typical cyclic voltammograms of polyaniline/benzenesulfonic
acid. FIG. 9A shows the electropolymerization of 0.1 M aniline and 1M
benzene-sulfonic acid. FIG. 9B shows the electropolymerization of
polyaniline/benzenesulfonic acid film in aqueous 0.5M sodium sulfate at pH
1.2.
FIG. 10 shows scanning electron micrographs of polyaniline/benzenesulfonic
acid film. FIG. 10A is at the 200 micrometer scale. FIG. 10B is at the 40
micrometer scale.
FIG. 11 shows a graph of the resistance of polyaniline/benzenesulfonic acid
as a function of gate potential, V.sub.G, (in volts versus SCE) between
two adjacent micro-electrodes.
FIGS. 12 a and b shows graphs of the coulomb efficiency and capacity of
polyaniline/benesulfonic acid electrode as a function of charge-discharge
current density in 1M sulfuric acid.
FIG. 13 shows typical cyclic voltammograms of polyaniline/polyvinylsulfonic
acid. FIG. 13A is the voltammogram during polymerization 0.1 M aniline and
12.5% polyvinylsulfonic acid. FIG. 13A is the voltagram for
polyaniline/polyvinylsulfonic acid film in aqueous 0.5M sodium sulfate at
pH 1.2.
FIG. 14 shows scanning electron micrographs of
polyaniline/polyvinylsulfonic acid film. FIG. 14A is a 200 micrometers.
FIG. 14B is at 40 micrometers.
FIG. 15 is a graph of the resistance in ohms of
polyaniline/polyvinylsulfonic acid as a function of gate potential,
V.sub.G, (in volts versus SCE), between two adjacent micro-electrodes.
FIG. 16 shows four plots of coulomb efficiency and capacity of various
polyaniline/polyvinylsulfonic acid electrodes as a function of
charge-discharge currently density in 1M sulfuric acid. FIG. 16A is
coulomb efficiency of a various half cell batteries. FIG. 16B is the
capacity of various half cell batteries. FIG. 16C is coulomb efficiency of
zinc as an anode. FIG. 16D is the capacity of zinc as an anode.
FIG. 17 shows typical cyclic voltammograms of
polyaniline/trifluoromethanesulfonic acid. FIG. 17A is the voltammogram
during polymerization in 0.1 M aniline and 1M trifluoromethanesulfonic
acid. FIG. 17B is the cyclic voltammogram of
polyaniline/trifluoromethanesulfonic acid film in aqueous 0.5M sulfuric
acid at pH 1.2.
FIG. 18 are photographs of scanning electron micrographs of
polyaniline/trifluoromethanesulfonic acid film. FIG. 18A is at 200
micrometers. FIG. 18B is at 40 micrometers.
FIG. 19 shows a plot of the resistance in ohms of
polyaniline/trifluoromethanesulfonic acid as a function of gate potential
V.sub.G, between two adjacent micro-electrodes.
FIG. 20 shows graphs of coulomb efficiency and capacity of various
polyaniline/trifluoromethanesulfonic acid electrodes as a function of
charge-discharge current in 2M zinc sulfate. FIG. 20A is a graph of the
coulomb efficiency, half cell battery. FIG. 20B is a graph of the
capacity, half cell battery. FIG. 20C is a graph of the coulomb
efficiency, zinc as an electrode. FIG. 20D is a graph of the capacity
having zinc as anode.
FIGS. 21a, b, c, d shows a plot of accelerated stability tests for four
self-doped polyaniline electrodes, PAN/Bs, PAN/PVSA, PAN/Ts, and
PAN/TFMSA.
FIGS. 22a and b shows a graph of long term charge/discharge curves at+or
-15mA cm.sup.2 in 1M ZnSO.sub.4 (pH 2.3) with a zinc anode.
FIG. 23 shows a graph of the open circuit voltage as a function of time for
self-doped polyaniline-zinc batteries.
FIG. 24 shows photographs of the surface morphology of two self-doped
polyanilines PAN/TFMSA and PAN/Ts at 200.mu.m and 40.mu.m.
FIG. 25 shows photographs of the surface morphology of two self-doped
polyanilnes PAN/PVSA and PAN/Bs at 200.mu.m and 40.mu.m.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
Definitions
As used herein:
"Aliphatic dopant" refers to aliphatic, unsaturated, cyclic, bridged and/or
fluorine substituted organic compounds having from 1 to 20 carbon atoms,
preferably having from to 12 carbon atoms, and more preferably having from
1 to 6 carbon atoms.
"Aromatic dopant" refers to those organic compounds which have a 5, 6, or 7
membered aromatic (e.g., benzene, toluene, naphatalene, chlorobenzene,
nitrobenzene, and the like) or heteroaromatic (e.g., pyrrole, pyridine,
quinoline and the like) sulfonic acid compounds. Aromatic compounds are
preferred.
"Organic dopant" refers to aliphatic unsaturated, cyclic, bridged, aromatic
heteroaromatic organic sulfonic acids (--SO.sub.3 H), acid chlorides
(--SO.sub.2 Cl), or alkali salts (--SO.sub.3 M, wherein M is, for example,
sodium or potassium). Organic means that at least one carbon atom is
present, e.g. trifluoromethanesulfonic acid.
The present invention is an almost all polymer solid state battery
comprising a permanently-doped polyaniline polymeric cathode (e.g.,
polyaniline/dopant), an optional solid polymer (e.g. NAFION .RTM. film)
and a zinc anode (e.g., zinc microparticles dispersed in a NAFION film).
FIG. 1 schematically represents the rechargeable polymer battery. A major
advantage of using a permanently-doped polyaniline cathode is that it
requires only the hydrogen ions be incorporated and expelled during the
discharge/charge cycle, because the negative charge sites, i.e., anions
are designed to be immobilized in the polyaniline polymer matrix.
In the discussion below, the polyaniline-dopant copolymer produced has a
number of different forms. In a preferred embodiment, a substantially
smooth polymer is formed which is useful in electrical transmission and/or
storage, e.g., as a battery electrode. In another embodiment, a "flakey"
type of product is obtained. This flakey material is useful to conduct or
store electricity after it is pressed into a wire or pellet form using
heat and/or pressure methods which are conventional in the art.
P-Toluenesulfonic Acid Dopant and Polyaniline
Comparison of Self-Doped Polvaniline/Tosylate (Toluenesulfonic Acid) and
Conventional Polyaniline made with Sulfuric Acid--The polyaniline/tosylate
polymer is synthesized electrochemically in an aqueous solution containing
about 0.1 M aniline and about 1 M tosylate (p-toluenesulfonic acid), which
produces a pH=0.65, using a potential-cycling method, from -0.2 V to +0.8
V at a rate of 0.1 V/second for 5.5 hours. FIG. 2A compares the resistance
of various conventional polyaniline films as a function of the applied
potential measured using an interdigitated microelectrode array. FIG. 2B
has the surprising feature in that the permanently doped
polyaniline/tosylate polymer is much more conductive (of the order of
about 1 to 100 S/cm). The residual electrical proeprties are seen in FIG.
2B in the region of about 0.6 to 1.3 volts. FIG. 3B shows a typical cyclic
voltammo-gram (CV) during the polymerization. Unlike the relatively
featureless polymerization CV curve of a polyaniline made from 0.1M
aniline and 0.1M H.sub.2 SO.sub.4, shown in FIG. 3A, polyaniline/tosylate
shows an additional redox peak about 0.2 V, which is due to the oxidation
of polyaniline by the incorporation of tosylate, i.e. SO.sub.3 -group. The
presence of the sulfonic groups (SO.sub.3 -) within the
polyaniline/tosylate polymer system was also confirmed by an EDAX
analysis, which showed the presence of a large amount of elemental sulfur
(see FIG. 4). FIGS. 3C and 3D compare cyclic voltammograms of 0.5 M
Na.sub.2 SO.sub.4 of the two grown films. While the polyaniline/tosylate
system shows a mostly featureless CV curve, however, with a large
double-layer charging current (more than 50 mA/cm.sup.2) (FIG. 3D), the
polyaniline/H.sub.2 SO.sub.4 shows an additional peak around 0.3 V that is
due to the conventional anion doping (FIG. 3C). FIG. 5 shows the
morphology of the self-doped polyaniline/tosylate polymer. The surface
exhibits an ultrafine microstructure with a highly electroactive surface,
which accounts for the observed high electrochemical capacitance.
The polyaniline/tosylate film is chemically more stable than conventionally
made polyanilines. Indeed, FIG. 6A demonstrates that the Zn
polyaniline/tosylate polymer battery shows no sign of degradation after
400 charge/discharge cycles at .+-.10 mA/cm.sup.2, while the conventional
polyaniline made in H.sub.2 SO.sub.4 using the same potential-cycling
method shows a degraded performance after only 50 cycles in about 6,000
seconds, FIG. 6B.
The charge/discharge reaction of the polyaniline/tosylate polymer electrode
may be written as:
##STR1##
where P denotes polyaniline. In the mechanism proposed in Eq. (1), only
small H.sup.+ ions are mobile, because the mechanism assumes that
tosylates containing SO.sub.3 - groups are immobilized in the polymer
chains. This immobilization results in a more reversible electrode
kinetics, better chemical stability, and a higher energy density than the
conventional polyaniline electrodes, in which anions must diffuse in and
out during a charge/discharge process, imparting some mechanical stress to
the polymer film. Moreover, the mechanism of Eq. (1) should allow the use
of a solid polymer electrolyte, e.g. Nafion, which provides better
chemical stability, less resistance (especially when a thin film is used),
and is easier to handle than the conventional organic and aqueous
electrolytes.
Table 1 above summarizes typical performance characteristics of different
polyaniline electrodes reported in the literature as well as the present
polyaniline/tosylate polymer. It is misleading, however, to directly
compare data from different laboratories because there may be many
differences in fabrications, operations, and evaluation of batteries (for
example, the weight of the present polyaniline electrode includes the
weight of a considerable amount of water because the polyaniline is not
removed from the electrode substrate).
______________________________________
Exhibit 1
DEFINITION OF SOME IMPORTANT
BATTERY PARAMETERS
______________________________________
(a) Dopant Concentration y (%)
##STR2##
where W (mg) is the weight of a polyaniline electrode, Q
(coulomb) is the total charge involved, M (g/mol) is the
molecular weight (92 for C.sub.6 H.sub.4 NH), and F (coulomb/mol) is
Faraday's constant (9.65 .times. 10.sup.4).
(b) Power Density P.sub.max (kW/kg)
P.sub.max = V.sub.oc .times. I.sub.ac /(4 .times. W .times. 10.sup.-3)
where V.sub.oc is open-circuit cell voltage and I.sub.ac is short-circui
current.
(c) Energy Density, E.sub.out (Wh/kg); Capacity Q.sub.total,out
(Ah/kg)
E.sub.out = V.sub.d .times. Q.sub.total,out /W .times. 10.sup.-3
where V.sub.d is the cell voltage during discharge. The charging input
energy is given by:
E.sub.in = V.sub.c .times. Q.sub.total,in /W .times. 10.sup.-3
where V.sub. c is the cell voltage during charge.
(d) Energy Efficiency (.eta..sub.Wh); Coulomb Efficiency (.eta..sub.Ah)
Energy efficiency: .eta..sub.Wh = E.sub.out /E.sub.in
Coulomb efficiency: .eta..sub.Ah = Q.sub.total,out /Q.sub.total,in
______________________________________
Some important battery performance parameters are defined in Exhibit 1. The
data indicate that the performance (e.g. capacity and energy density) of
the polyaniline-polymer/Zn battery is already comparable to that of a
typical lead-acid battery. However, in comparison with batteries made
using polyaniline/H.sub.2 SO.sub.4 films, it is clear that the performance
of the polyaniline/tosylate/zinc battery is nearly comparable in terms of
capacity, energy density, and self-discharge rate. The relatively low
energy density and capacity observed with the polyaniline/tosylate is
attributed to the relatively heavy weight of tosylate (FW 172).
POLYMERIZATION CONDITIONS FOR THE POLYANILINE/TOSYLATE
1. Solution Temperature During Polymerization
The effect of the solution temperature during polymerization (20.degree.,
30.degree., and 40.degree. C.) is examined. The results are summarized in
Table 2. For comparison, the performance of the conventional polyaniline
polymer electrode made with H.sub.2 SO.sub.4 is presented.
As the solution temperature increases, the kinetics of the electrochemical
polymerization for the aniline/tosylate becomes faster, and less time is
required to grow the films. However, increasing the solution temperature
also encourages the chemical reaction, which competes with the
electrochemical polymerization reaction, to form an insulating film. When
the solution temperature is 40.degree. C., a very flaky polymer film is
formed, PAN 85, which results in a degraded battery performance. Among the
three polyaniline/tosylate polymer electrodes studied, the best result in
terms of change capacity is obtained when the solution temperature is room
temperature, i.e. 20.degree. C. (PAN 83); however, the coulomb efficiency
(about 60 percent) is poorer than that of the conventional polyaniline
electrode at the low current density of .+-.2mA/cm.sup.2.
TABLE 2
__________________________________________________________________________
SUMMARY OF EFFECT OF THE SOLUTION TEMPERATURE DURING
POLYMERIZATION ON THE HALF-CELL BATTERY PERFORMANCE.sup.a
OF THE POLYANILINE/TOSYLATE ELECTRODES
AT .+-.2 mA/cm.sup.2
PAN 86 PAN 83 PAN 81 PAN 85
__________________________________________________________________________
Electrode substrate
3D fat posts
3D fat posts
3D fat posts
3D fat posts
Starting materials
0.1 M aniline
0.1 M aniline
0.1 M aniline
0.1 M aniline
0.1 M H.sub.2 SO.sub.4
1 M tosylate
1M tosylate
1 M tosylate
Solution pH 1.4 0.65 0.65 0.65
Solution temperature (.degree.C.)
20 20 30 40
Preparation method
PC.sup.b
PC.sup.b
PC.sup.b
PC.sup.b
Total coulombs
4 hr., 2.4 C
4 hr., 18.0 C
4 hr., 23.4 C
0.75 hr., 18 C
Weight (mg) 0.6 18.3 24.3 11.8.sup.c
V.sub.oc (V) 0.46 0.43 0.45 0.39
I.sub.sc (mA/cm.sup.2)
0.04 0.02 0.13 0.07
Capacity (Ah/kg)
74.1 21.8 17.1 16.5
Coulomb eff. (%)
94 59 52 82
E.sub.out (Wh/kg)
35.8 10.8 8.3 8.4
__________________________________________________________________________
.sup.a Half-cell battery test was performed in 1 M ZnSO.sub.4 (pH 2.3) by
cycling potential between 0.35 V and 0.8 V vs. SCE at a constant
chargedischarge rate of .+-.2 mA/cm.sup.2.
.sup.b Potential cycled at 100 mV/sec between -0.2 V and +0.8 V vs. SCE.
.sup.c Film was flaky and loose, some material lost during rinsing after
polymerization.
The coulomb efficiency of the polyaniline/tosylate polymer electrodes
improves dramatically as the charge-discharge current density increases,
reaching almost 100 percent at .+-.10 to .+-.20 mA/cm.sup.2 [see FIG. 7B].
Moreover, the charge capacity of the polyaniline/tosylate electrodes
remain relatively unchanged with an increase of the current density, while
the capacity of the conventional polyaniline electrode quickly degrades
[see FIG. 7A]. This indicates that the polyaniline/tosylate electrodes are
chemically more stable, presumably because the fixed anion (SO.sub.3 -)
sites allow H.sup.+ ions to be primarily mobile ions during the
charge-discharge process, forming a useful cathode in an aqueous,
high-current-density polymer battery.
ELECTROPOLYMERIZATION
The electrochemical polymerization method (potential-cycling method vs.
constant voltage method) as well as the effect of pretreatment (cycling
potential in 0.1 M H.sub.2 SO.sub.4 prior to the testing) is summarized in
Table 4.
TABLE 4
__________________________________________________________________________
SUMMARY OF EFFECT OF THE COMPOSITION
OF THE STARTING POLYMERIZATION SOLUTION
ON THE HALF-CELL BATTERY PERFORMANCE.sup.a
OF THE POLYANILINE/TOSYLATE ELECTRODE AT .+-.2 mA/cm.sup.2
PAN 96 PAN 93 PAN 92 PAN 95
__________________________________________________________________________
Electrode substrate
flat flat 3D flat
flat
Starting materials
0.05 M aniline
0.1 M aniline
0.2 M aniline
0.2 M aniline
1 M tosylate
1 M tosylate
1 M tosylate
0.8 M tosylate
Solution pH 0.65 0.65 0.65 1.1
Solution temperature (.degree.C.)
20 20 20 20
Preparation method
PC.sup.b
PC.sup.b
PC.sup.b
PC.sup.b
Total coulombs
12 hr, 6.1 C
4 hr, 3.7 C
6.5 hr, 7.0 C.
4 hr. 3.2 C
Weight (mg) 8.4 3.9 6.4 2.9
V.sub.oc (V) 0.43 0.43 0.03.sup.c
0.45
I.sub.sc (mA/cm.sup.2)
0.46 0.76 0.3 0.13
Capacity (Ah/kg)
17.9 24.9 25.1 26.8
Coulomb eff. (%)
87 86 93 90
E.sub.out (Wh/kg)
9.1 12.7 12.6 13.1
__________________________________________________________________________
.sup.a Half-cell battery test was performed in 1 M ZnSO.sub.4 (pH 2.3) by
cycling potential between 0.35 V and 0.8 V vs. SCE at a constant
chargedischarge rate of .+-.2 mA/cm.sup.2.
.sup.b Potential cycle at 100 mV/sec between -0.2 V and +0.8 V vs. SCE.
.sup.c The film partly peeled off.
The polyaniline/tosylate prepared by applying a constant potential of 0.7 V
vs SCE (PAN 103) exhibits fair performance (Table 5). When the potential
is increased to 0.8 V, the resulting film is very powdery and peels off as
soon as it is blown dry. When a constant potential of 0.65 V is used, the
film takes a long time to grow, and the battery performance is not very
good (PAN 104). The best results are obtained when the films grown by the
potential-cycling method are pretreated by cycling between -0.2 V and 0.8
V at 100 mV/second in 0.2 M H.sub.2 SO.sub.4 for 2 hours (PAN 99).
Pretreatment improves the half-cell battery performance by about 50
percent over the previous data (e.g. PAN 95); capacity and energy density
became -40 Ah/kg and about 20 Wh/kg, respectively. This improvement is
likely due to leaching out of the excess of tosylate ions, which are not
incorporated into the polyaniline matrix reducing the effective weight of
the electrode. No further improvement is observed when the pretreatment
was continued for 12 hours (PAN 100).
TABLE 5
__________________________________________________________________________
SUMMARY OF EFFECT OF ELECTROCHEMICAL POLYMERIZATION METHOD
AND PRETREATMENT ON THE HALF-CELL BATTERY PERFORMANCE.sup.a
OF THE POLYANILINE/TOSYLATE ELECTRODE AT .+-.2 mA/cm.sup.2
PAN 103 PAN 104 PAN 99 PAN 100
__________________________________________________________________________
Electrode substrate
flat flat flat flat
Starting materials
0.2 M aniline
0.2 M aniline
0.1 M aniline
0.1 M aniline
0.8 M tosylate
0.8 M tosylate
1 M tosylate
1 M tosylate
Solution pH 1.1 1.1 0.65 0.65
Solution temperature (.degree.C.)
20 20 20 20
Preparation method
0.7 V for 0.5 hr
0.65 V for 4 hr
PC.sup.b for 4 hr
PCV.sup.b for 4 hr
Total coulombs (C)
4 4 4.1 4.1
Weight (mg) 2.7 3.5 4.7 4.5
Pretreatment -- -- 2 hr.sup.c
12 hr.sup.c
Capacity (Ah/kg)
29.1 17.1 38.4 40.3
Coulomb eff. (%)
93 96 96 87
E.sub.out (Wh/kg)
14.8 8.2 19.4 19.7
__________________________________________________________________________
.sup.a Half-cell battery test was performed in 1 M ZnSO.sub.4 (pH 2.3) by
cycling potential between 0.35 V and 0.8 V vs. SCE at a constant
chargedischarge rate of .+-.2 mA/cm.sup. 2.
.sup.b Potential cycle at 100 mV/sec between -0.2 V and +0.8 V vs. SCE.
.sup.c Cycled in 0.1 M H.sub.2 SO.sub.4.
The most striking feature of the polyaniline/tosylate polymer films is
that, in addition to being highly conductive, they exhibit a second
conductive region (permanently conductive), which extends to a higher
potential region, up to 1.5 V. This also means that the polyaniline/
tosylate films are chemically more stable than conventionally made
polyanilines. The unique resistance vs. voltage characteristics of the
polyaniline/tosylate is also used to design new molecular electronic
devices such as an organic transistor and memory device.
In another preferred embodiment, the polymer is produced under the
following conditions wherein the aniline is at a starting concentration of
about 0.1M, the p-toluensesulfonic acid is at a starting concentration of
about 1M, the potential range is between about -0.1 and +0.9 V versus SCE,
the scan rate is about 0.1V per second, the total coulomb is about 1.1,
and the time is about 15 minutes.
In a preferred embodiment the polymer is prepared wherein the aniline is at
a starting concentration of about 0.1M, the p-tolunesulfonic acid is at a
concentration of about 1M, the potential range is between about -0.2 and
+0.8 V versus SCE, the scan rate is about 0.1 V per second, and the total
coulombs is 6.0 and the time is about 6.5 hours.
In another preferred embodiment, the self-doped polyaniline is produced
having about a 0.1M starting concentration of aniline and about 1M
p-toluenesulfonic acid, a potential range of between about -0.2 and +0.8
volts versus SCE and a scan rate of about 0.1 volt per second. The
produced polymer is a function of time and the size of the electrode. In a
more preferred embodiment of the above reaction conditions, the time is 3
hr. and the total coulomb is 6.1.
In a more preferred embodiment, the self-doped polyanine is produced having
about a 0.1M starting concentration of aniline and 1M starting
concentration of aniline and 1M benzenesulfonic acid, a potential range of
between about -0.1 to +0.9 volts versus SCE, and a scan rate of about 0.1
volts per second. The thickness of the produced polymer is a function of
time and size of the electrode. In a more preferred embodiment of the
above reaction conditions, the time is hr. and the total coulomb is 5.5.
In a preferred embodiment the self-doped polyaniline is produced having a
starting aniline concentration of 0.1M, a 12.5 percent by volume starting
polyvinylsulfonic acid concentration, a potential range of between about
-0.2 to +0.8 V (versus SCE) and a scan rate of about 0.1 V per second. The
thickness of the polymer is a function of the time of reaction and size of
the electrode. In a more preferred embodiment of the above conditions, the
time is for about 16 hr. and a total coulomb is 5.4.
In a preferred embodiment, the self-doped polyaniline is produced having
about a 0.1M starting concentration of aniline, a 1M starting
concentration of trifluoromethanesulfonic acid, a potential range of about
-0.1 to +0.9 versus SCE and a scan rate of 0.1 V per second. The thickness
of the polymer is a function of the time and the size of the electrode. In
a more preferred embodiment of the above conditions, the time is about 2.5
hr. and the total coulomb is about 6.1.
The NAFION.RTM.-Polyaniline/Tosylate Composite Electrodes
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