Electrodes containing conductive metal oxides

An electrode suitable for use as a lead-acid battery plate contains an inorganic metal oxide additive which enhances the formation of the plate. The additive is electrically conductive, stable in aqueous solutions of sulfuric acid, but does not participate in the electrode reaction. Suitable metal oxides include conductive oxides such as TiO.sub.2-x, WO.sub.3-x, MoO.sub.3-x, V.sub.2 O.sub.5-x, Nb.sub.2 O.sub.5-x, wherein x is greater than 0 and less than or equal to 1, mixtures thereof and mixed conductive oxides of these elements. The conductive oxides may also be used in electrodes for bipolar lead-acid batteries.

TECHNICAL FIELD 
This invention relates to electrode materials of the type used in an acid 
electrolyte. More particularly this invention relates to conductive oxide 
electrode materials for use in a sulfuric acid electrolyte as an additive 
for lead-acid battery plates or as a bipolar substrate additive. 
BACKGROUND OF THE INVENTION 
Conventional lead acid battery plates include a positive electrode 
(PbO.sub.2 plate) and a negative electrode (Pb plate) immersed in a 
sulfuric acid electrolyte and having a separator interposed therebetween. 
As a means of improving the ease of manufacture of such batteries, a 
variety of conductive additives have been proposed for incorporation into 
the plates. Lead dioxide has been proposed as an additive for paste 
mixtures containing tetrabasic lead sulfate, as described in Reich, U.S. 
Pat. No. 4,415,410, issued Nov. 15, 1983. Lead dioxide has also been 
formed in battery pastes by a reaction between lead monoxide and a 
persulfate salt (Reid, U.S. Pat. No. 2,159,226, issued May 23, 1939) or 
with ozone (Parker, U.S. Pat. No. 4,388,210, issued June 14, 1983, and 
Mahato et al, U.S. Pat. No. 4,656,706, issued Apr. 14, 1987). Lead dioxide 
enhances positive plate formation but provides no substantial advantages 
in the resulting battery because it participates in the positive plate 
reaction. During charging of the battery, lead sulfate is converted into 
lead dioxide, and the reverse reaction occurs during discharge. 
Battery plate grids comprising a composite article on which a flowable 
plastics material is molded to engage portions of a conductive material, 
such as lead or a lead alloy, are also known. Buckethal et al, U.S. Pat. 
No. 4,118,553 issued Oct. 3, 1978. Also known is a lead-acid rechargeable 
cell having a positive electrode wherein a titanium alloy replaces lead as 
the supporting member for the active lead peroxide and is covered with a 
nonpolarizing film of gold or other suitable material. See, Ruben, U.S. 
Pat. No. 3,615,831 issued Oct. 26, 1971. 
Carbon has been used as a lead-acid paste additive, and has been used in 
combination with plastic materials in electrodes for bipolar lead-acid 
batteries, as described in Biddick, U.S. Pat. No. 4,098,967, issued Jul. 
4, 1978. Carbon, however, is not stable as a positive electrode material 
because it tends to oxidize. Thus, bipolar electrodes solely utilizing 
carbon as the conductive filler are not generally satisfactory for long 
term use. 
Unitary plate electrodes comprising fiberglass coated with tin dioxide, 
lead dioxide, and a thin film of lead or graphite filled resin are 
described in Rowlette et al, U.S. Pat. No. 4,547,443 issued Oct. 15, 1985. 
That use does not, however, suggest the uses of transition metal 
conductive oxides in the manner described herein 
The present invention involves the use of conductive oxides, preferably 
those of titanium, tungsten, molybdenum, vanadium and niobium. Certain 
oxides of these transition metals exist or can be prepared in a 
non-conductive state. Reduction of these non-conductive oxides, such as in 
a hydrogen atmosphere, at elevated temperatures, creates a conductive 
class of materials whose use in batteries or electrodes as described 
herein has not heretofore been recognized. 
Certain conductive metal oxides have been used in applications, for 
example, in polymeric compositions for electrical components as described 
in Penneck et al, U.S. Pat. No. 4,470,898, issued Sept. 11, 1984, and in 
corrosion-resistant coatings as described in Tada, U.S. Pat. No. 
4,352,899, issued Oct. 5, 1982. 
Voss et al, in U.S. Pat. No. 3,096,215 issued Jul. 2, 1963 discloses the 
use of a sintered titanium dioxide electrode, impregnated with silver, as 
an auxiliary electrode for eliminating gases formed during operation of 
the battery. The electrode is formed with a cavity communicating with a 
gas space of the battery so that gas produced during formation or 
discharge can be absorbed. The auxiliary electrode is coupled electrically 
to the positive or negative plates of the battery, depending on which 
electrode is causing the problem gas generation. 
Certain metal oxides have also been suggested for use in fuel cells to 
serve as substitutes for the more expensive platinum as a catalyst 
material See, Nestor, U.S. Pat. No. 3,480,479 issued Nov. 25, 1929 (a 
molybdenum oxide mixed with tungsten disulfide); Broyde, U.S. Pat. No. 
3,544,378 issued Dec. 1, 1970 (a rare earth tungsten oxide M.sub.x 
WO.sub.3 where x is between 0 and 1 and M is a rare earth element). 
An oxygen reducing negative active material for a storage cell which 
includes a molybdenum oxide having an average valency between 4 and 6 is 
discussed in Gabano et al, U.S. Pat. No. 3,871,917 issued Mar. 18, 1975. 
The oxide is supported by mechanical compression. A conductive body (e.g. 
graphite) and binding agents may be employed. The material is used with 
conventional positive electrode systems (i.e., PbO.sub.2,PbSO.sub.4 
/H.sub.2 SO.sub.4,H.sub.2 O. 
Further, the use of bulk titanium oxide having the formula TiO.sub.x where 
x is 1.55 to 1.95 has been suggested for electrode use in electrochemical 
cells. See, Hayfield, U.S. Pat. No. 4,422,917 issued Dec. 27, 1983. Solid, 
bulk titanium oxide materials are discussed for electrode applications 
including storage batteries, bipolar cells for chlorate production, etc. 
Tin dioxide (SnO.sub.2) has also been suggested as a coating for fiberglass 
strands of unitary electrodes. See, for example, Rowlette et al, U.S. Pat. 
No. 4,547,443, issued Oct. 15, 1985 This coating has proven somewhat 
useful, but it fails to completely meet the need for a conductive additive 
which is economical, enhances plate formation and also improves the 
properties of the resulting lead-acid battery. 
The present invention provides novel electrodes used in lead-acid batteries 
which are not appreciated by the foregoing art and which overcome the 
deficiencies of the aforementioned systems. 
SUMMARY OF THE INVENTION 
The invention provides an electrode containing an electrically conductive 
material, specifically a sulfuric acid-resistant, inorganic metal oxide, 
preferably a transition metal oxide in a reduced state, for example, 
certain oxides of titanium, tungsten, molybdenum, vanadium and niobium, 
mixtures of these conductive oxides, or conductive mixed oxides of these 
elements. Electrodes according to the invention include lead-acid battery 
electrodes, such as plates, tubular electrodes or bipolar electrodes. 
In a positive lead-acid battery plate of the invention, the conductive 
material serves as an additive which enhances the formation of a lead-acid 
battery plate. The conductive material in combination with a binder may 
also serve as a plate support grid. The conductive material additive does 
not participate in the electrode reaction, for example, in the manner of 
lead dioxide in positive lead-acid battery plates, but rather serves only 
as a conductive material. An electrode according to the invention is 
especially suitable for use as the positive plate of a lead-acid battery 
in combination with a negative plate containing carbon as the conductive 
additive. 
According to further aspects of the invention, a bipolar electrode for use 
in a bipolar lead-acid battery includes a substrate and layers of positive 
and negative active material disposed on opposite sides of the substrate. 
The substrate contains the foregoing conductive oxide as a filler, and a 
polymeric binder.

DETAILED DESCRIPTION 
According to the invention, an electrically conductive oxide selected from 
the class of inorganic oxides generally known as being non-conductive are 
used in electrodes, especially in electrodes for use in sulfuric acid 
electrolytes. For such uses, the oxide must first be converted to a 
conductive state. Conductivity is essential to enhancing lead-acid battery 
plate formation and for use as an electrode in electrolytic processes. For 
purposes of the present invention, "conductive" means a conductivity of at 
least about 0.1 ohm.sup.-1 cm.sup.-1, preferably at least about 10 
ohm.sup.-1 cm.sup.-1. The processes for converting the oxides to their 
conductive states are described below. 
Second, the oxide should be stable in water and aqueous sulfuric acid 
solutions. For purposes of the present invention, "sulfuric 
acid-resistant" means stable in dilute aqueous sulfuric acid having 
specific gravities in the range of about 1 to 1.4, as commonly used in 
lead-acid batteries, at temperatures in the range of about -40.degree. C. 
to 80.degree. C. Stability in up to 12 molar sulfuric acid solution at 
such temperatures is preferred. If the oxide is attacked by the acid 
electrolyte, the structure of the resulting plate will be adversely 
affected. 
Finally, the oxide usually needs to be electrochemically inert, i.e., it 
should not participate in the electrochemical reaction occurring in the 
battery or electrolytic process. Absent this characteristic, the oxide has 
no lasting effects in the battery, or is consumed as part of the 
electrolytic process. 
When used in a positive electrode in a lead-acid battery, the conductive 
oxide according to the invention preferably has an oxygen overpotential 
about the same as or greater than lead dioxide under like conditions, 
particularly when used in a lead-acid battery wherein the sulfuric acid 
electrolyte has a specific gravity in the range of about 1.001 to 1.4 at a 
temperature in the range of from about 20.degree. C. to 80.degree. C., 
especially -40.degree. C. to 80.degree. C. 
Few inorganic oxides have all of the foregoing characteristics. Several are 
described in commonly owned, co-pending U.S. patent application Ser. No. 
07/345,993 filed May 2, 1989 and entitled "Electrodes Containing 
Conductive Metal Oxides" by N. K. Bullock and W. Kao. Barium metaplumbate 
is the preferred material in that application which principally involves 
perovskite structure oxides of the formula 
EQU A.sub.a B.sub.b O.sub.c 
wherein A is Sr, Ba, Zn, Cd, Ra or a combination thereof, B is Zr, Sn, or 
Pb, and 0.5.ltoreq.a.ltoreq.1, 0.5.ltoreq.b.ltoreq.1, and 
2.ltoreq.c.ltoreq.3, optionally containing small amounts of other elements 
such as Bi, Ag, K, Li, Ti, Nb, Al, Cr, Zn, Mn, Mg or Ca, and the resulting 
compound is substantially stable in sulfuric acid, has a conductivity of 
at least about 0.1 ohm.sup.-1 cm.sup.-1, and can be used as an electrode 
in an aqueous sulfuric acid solution without generating excessive oxygen 
when used in a positive electrode, or without reacting to generate 
excessive hydrogen if used as a negative electrode. 
The transition metals include elements from Sc to Cu, Y to Ag and Hf to Au 
in the first, second and third series, respectively. According to the 
invention, it has been discovered that a variety of transition metal 
oxides can be prepared which are both sulfuric acid resistant and 
electrically conductive. These compounds tend to be transition metal 
oxides wherein the metal is in an oxidation state lower than its group 
oxidation state. For example, the transition metals of Groups 4, 5 and 6 
typically form stable, non-conductive oxides such as TiO.sub.2, WO.sub.3, 
MoO.sub.3, V.sub.2 O.sub.5, and Nb.sub.2 O.sub.5. In each of these 
compounds the metal is in its group oxidation state, namely (IV) for Ti, 
(V) for V and Nb, and (VI) for W. By contrast, reduced metal oxides, such 
as TiO, Ti.sub.2 O.sub.3, VO, V.sub.2 O.sub.3, VO.sub.2, WO.sub.2, W.sub.2 
O.sub.5, MoO.sub.2, Mo.sub.2 O.sub.5, and NbO.sub.2, wherein the metal 
atom is in an oxidation state lower than its group oxidation state, are 
electrically conductive. 
In the present invention oxides of titanium, tungsten, molybdenum, vanadium 
and niobium which are non-conductive in their most stable form, i.e. when 
the metal is in its group oxidation state, can be converted to conductive 
metal oxides by, for example, reducing stoichiometric powders in a 
hydrogen atmosphere at elevated temperatures. Such techniques are, in and 
of themselves, well known and need not be described in detail herein (see, 
for example, the aforementioned Gabano and Hayfield patents). 
For definitional purposes, the materials which are useful in the present 
invention will be described as "conductive oxides". The most preferred 
conductive oxides for use in the invention include conductive oxides of 
titanium, tungsten, molybdenum, vanadium and niobium represented by the 
formulas TiO.sub.2-x, WO.sub.3-x, MoO.sub.3-x, V.sub.2 O.sub.5-x and 
Nb.sub.2 O.sub.5-x where x is greater than 0 and less than or equal to 1, 
particularly about 0.001 to 1, mixtures thereof, and the conductive mixed 
oxides of these elements. For V.sub.2 O.sub.5-x, x may range from 0.001 to 
3, although the range of 0.001 to 1 is preferred. 
The reduction temperatures used for the preparation of the various 
conductive oxides may vary between about 300.degree. C. to over 
1000.degree. C., and the amount of reduction may be selected to optimize 
conductivity properties for the desired application. As will more fully be 
discussed below, if binders are used, resistivity may be controlled by 
varying both or either the stoichiometry or the percentage of the 
conductive oxide used in the binder. For example, using a conductive 
tungsten oxide WO.sub.2 (commercial grade, for example), resistivity drops 
from 1.70 ohm-cm at 22.5% (volume percent) in a polyethylene binder to 
0.033 ohm-cm at 53.8% (volume percent) conductive oxide powder. Particle 
size will also affect resistivity. 
Lead-acid battery electrodes are commonly made by applying a paste 
containing lead compounds to a lead grid. The conductive oxides of the 
invention may be incorporated directly into positive lead-acid battery 
paste mixtures. In such pastes, the amount of the conductive oxide 
according to the invention, based on the total solids is generally in the 
range of from about 0.01 to 50 wt. %, preferably about 0.05 to 8 wt. % for 
positive plates. Formation enhancement effects level out at about 8 wt. % 
and at concentrations less than 0.1%, the improvement in formation becomes 
minimal. 
The conductive oxides of the invention are conveniently added to the paste 
mixture in powder form. The particle size of the conductive oxides used to 
make a paste according to the invention is not critical, but the particles 
should generally be sufficiently small to allow the conductive oxide to be 
evenly distributed throughout the paste and in the resulting layer of 
positive active material. Conductive oxide particles ground to an average 
particle size (diameter) in the range of from about 0.1 to 300 microns, 
more preferably from about 0.1 to 40 microns are useful for purposes of 
the present invention. The conductive oxides can also be used in other 
forms, for example, as a coating for fibers or as a composite material. 
It is not usually necessary that the conductive oxides according to the 
invention for use in lead-acid battery plates be of high purity. 
Impurities such as unreduced starting materials may be present. However, 
the purity of the oxide should be taken into account when determining the 
amount to be used. 
Standard paste ingredients, including lead oxide (PbO, Pb.sub.3 O.sub.4, 
etc.), sulfuric acid, water and various well-known additives, such as 
fibers and expanders, may be used in conventional amounts. A solid mixture 
for making a battery paste according to the invention may contain, as 
solids, up to 0.5 wt. %, especially 0.05 to 0.4 wt. % fiber, 0.01 to 50 
wt. % of the conductive oxide according to the present invention, and the 
balance lead oxide(s), including any free lead present in the lead oxide. 
Preferably, these ranges are 0.05 to 0.4 wt. % fiber, 0.05 to 8 wt. % of 
the conductive oxide according to the invention, and the balance lead 
oxides. 
Fibers may be used in positive paste mixes as a binder to improve the 
handling characteristics of the battery plates after pasting. Suitable 
fibers include fiberglass, tin or tin dioxide-coated fiberglass, carbon 
fibers, synthetic plastic fibers such as modacrylic fibers, and mixtures 
thereof. Such fibers typically have a fineness of about 2 to 4 denier and 
lengths in the range of 0.15 to 0.35 cm. The density of the modacrylic 
fibers useful in pastes according to the invention is in the range of 
about 1.2 to 1.5 g/cc. 
In one embodiment of a lead-acid battery according to the present 
invention, the positive electrode contains a conductive oxide according to 
the invention and the negative electrode does not. However, negative plate 
formation poses problems if the lead oxide used to make the paste has a 
very low free lead content, i.e. less than about 0.2 wt. % of the lead 
oxide. This problem can be remedied by incorporating therein an amount of 
high surface area carbon (or other expanders) effective to enhance the 
formation process without adversely affecting battery performance. For 
this purpose, from about 0.05 to 0.5 wt. %, especially 0.1 to 0.2 wt. % 
of carbon, based on the total solids present may be incorporated into the 
negative paste mixture. The foregoing amounts are in addition to any 
carbon already present in the expander mixture. 
A typical paste mixture according to the invention contains (1) a lead 
sulfate compound selected from lead sulfate, and mono-, tri- or tetrabasic 
lead sulfate, (2) a lead oxide compound selected from o-PbO, t-PbO, and 
Pb.sub.3 O.sub.4, (3) an amount of the conductive oxide material according 
to the invention sufficient to enhance the formation and/or other 
properties of the resulting plate, (4) water in an amount effective to 
provide a flowable paste, and optionally (5) other additives such as 
carbon and fiber. A preferred battery paste for making positive plates 
according to the invention contains, as solids and after a portion of the 
initial lead monoxide has reacted with sulfuric acid to form lead 
sulfate(s), about 55-60 wt. % lead sulfate or basic lead sulfate(s), 40-44 
wt. % PbO, and 0.05-8 wt. % of the conductive oxide according to the 
invention, optionally also including 0.1 to 0.2 wt. % of carbon, and 
0.001-0.002 wt. % fiber. The water content of such a paste is in the range 
of about 0.15-0.2 ml/g of solids. 
Battery plates used in lead-acid batteries according to the invention may 
be made by any well-known process, for example, by applying the foregoing 
paste to the surface of a battery plate grid and forming the paste into an 
active material. In general, the paste is made by adding sulfuric acid and 
water to lead oxide to form lead sulfate or basic lead sulfate compounds 
in a mixture with excess unreacted lead oxide, optionally containing free 
lead, lead dioxide, and other conventional additives. This may be done by 
first weighing out a predetermined amount of lead oxide into a weigh 
hopper and dumping the lead oxide into a batch mixer, such as a mulling 
mixer. Dry additives such as fiber, expander and the conductive oxide 
according to the invention are directly added into the mixer. The 
resulting mixture is dry mixed for several minutes so that the additives 
are dispersed throughout the lead oxide. Water is then added as needed to 
make a paste of the desired consistency. Excessively moist or dry paste 
renders pasting impossible. The wet mixture is mixed for a short time to 
wet out the lead oxide. Sulfuric acid is then added as mixing continues 
until the temperature peaks at about 65.degree. C. and then drops to the 
range of 43.degree.-49.degree. C. The acid is added gradually to prevent 
the paste from overheating. The resulting paste is then cooled by 
evaporation of water and conduction to the mixer. Such a lead-acid battery 
paste is generally made in a batch reactor, although continuous processes 
have been proposed and could be used. 
Referring to FIG. 1, an electrode (positive plate) 10 of the invention is 
made by the conventional process of applying the foregoing paste to a flat 
grid 11 comprising grid elements 12 made of a lead alloy, such as 
lead-antimony or lead-calcium. The conductive oxide according to the 
present invention is then incorporated into the paste. The plate is then, 
if necessary, flash-dried and cured. Thereafter, the plate is formed 
(charged) to obtain a layer of active material 13 containing the 
conductive oxide of the invention homogenously dispersed therein. 
Formation may be carried out either before or after the plate is assembled 
into a battery casing together with a negative plate, a separator, and the 
electrolyte. 
Another method of making a positive battery plate, commonly called the 
tubular plate process, is used in the manufacture of traction and 
stationary batteries. In this process, tubes are constructed from woven, 
braided or felt polyester, glass, or other sulfuric acid and 
oxygen-resistant fibers. The tubes are shaped in a suitable solution under 
thermal treatment. The current collector, commonly called the spine, is a 
hard lead alloy rod centered in each tube by, for example, star 
protrusions. The spine is typically made by casting molten lead under high 
pressure. The tubes are pulled over the spines and then filled with lead 
oxide materials such as t-PbO and o-PbO mixed with Pb.sub.3 O.sub.4 in 
either a powder or slurry form. The lead oxide mixture is vibrated to 
settle it into a more compact form inside the tube. 
Following the tube filling process, the tubular plate is immersed in 
sulfuric acid solution for several days. During this process, lead sulfate 
and basic lead sulfates form and Pb.sub.3 O.sub.4 decomposes to lead 
sulfate materials and PbO.sub.2, thus enhancing the conductivity of the 
paste. The use of Pb.sub.3 O.sub.4 thus improves the efficiency of the 
formation process by forming PbO.sub.2. In a tubular electrode according 
to the present invention, the conductive oxide of the invention is 
incorporated into the lead oxide mixture, reducing or eliminating the need 
to add Pb.sub.3 O.sub.4. 
FIG. 2 illustates a tubular electrode 20 of the invention made according to 
the foregoing process for use in a lead-acid battery Electrode 20 includes 
a central current collector rod 21, a tubular sheath of fabric mesh 22, 
and annular layer of active material 23 interposed between collector 21 
and mesh 22. Active layer 23 contains a conductive oxide material 
according to the invention. An electrode of this type need not be 
symmetrical, and can include a series of spaced collectors 21. 
Referring to FIG. 3, the foregoing electrode plates are combined with 
several other components to make the lead-acid battery 30. Battery 30 
according to the invention includes a conventional casing 37 which houses 
two or more cells defined by a partition 31. Each cell includes a positive 
lead dioxide electrode 32 containing a conductive oxide according to the 
invention, a negative lead electrode 33, a separator 34 interposed between 
the electrodes, and an aqueous sulfuric acid electrolyte in which the 
electrodes and separator are immersed. Electrodes 32, 33 each comprise 
lead alloy grids 35 having active material 36 deposited thereon. The 
casing, separator, negative electrode (plate) and the electrolyte may be 
of conventional design and need not be described in detail. See, for 
example, Biagetti, U.S. Pat. No. 3,765,943, issued Oct. 16, 1973, the 
contents of which are hereby expressly incorporated by reference herein. 
The electrolyte may be a liquid, or may be gelled or immobilized by 
absorption in the separator. 
A conductive oxide according to the invention can also be used as a filler 
material in a bipolar electrode substrate for a bipolar lead-acid battery, 
for example, of the type described in Biddick, U.S. Pat. No. 4,098,967 or 
Poe, U.S. Pat. No. 3,795,543, the entire contents of which patents are 
hereby expressly incorporated herein by reference. 
Referring to FIG. 4, a bipolar electrode 40 of the invention generally 
comprises a substrate (plate) 41 made of a sulfuric acid-resistant plastic 
matrix in which fine particles of the conductive oxide are dispersed. 
Layers 42, 43 of positive and negative active lead materials, 
respectively, are formed on opposite sides of substrate 41. The average 
particle size of the particles used in substrate 41 is generally in the 
range of from about 0.1 to 300 microns, preferably from about 0.1 to 40 
microns, and more preferably from 0.1 to 5 microns. For purposes of the 
present invention, polyethylene, polypropylene, fluorinated derivatives 
thereof, and similar plastics having suitable strength and resistance to 
sulfuric acid can be used. In particular, a preferred polyethylene 
according to the invention has a molecular weight of from 200,000 to 
300,000, a peak melting point of about 135.degree. C. or higher, and a 
strength of from 3000 to 5000 psi. Such PE plastic also typically has a 
conductivity of about 10.sup.-16 ohm.sup.-1 cm.sup.-1, a density of about 
0.96 g/cm.sup.3, and an elastic modulus of about 50,000-80,000 psi. 
In a bipolar battery according to the invention, the carbon filler 
described in the Biddick et al. patent is replaced with a conductive oxide 
according to the invention in comparable amounts, for example about 10 to 
about 95% by volume, particularly about 15 to about 60% by volume in the 
bipolar electrode. Otherwise, a bipolar battery of like configuration to 
Biddick et al, including a stack of bipolar electrodes coated on opposite 
sides with positive and negative lead-acid active materials and having 
separators interposed therebetween, may be constructed according to the 
present invention. 
A conductive oxide of the present invention accordingly can avoid the 
drawbacks of carbon as a conductive additive for a bipolar electrode. For 
example, a large amount of carbon must be used to obtain the desired level 
of conductivity, but this can make the resulting material too porous for 
use as a bipolar electrode substrate. Carbon also has poor stability in 
sulfuric acid electrolyte when used in a positive electrode. 
Several embodiments of the invention are hereafter illustrated in the 
following experimental examples: 
EXAMPLE 1 
Certain conductive oxides of tungsten were prepared in a polyethylene 
matrix and the resistivity of the resultant material was determined as 
shown in Table I. The materials were prepared by first reducing 
non-conductive WO.sub.3 to various levels, thereby obtaining a conductive 
oxide powder. Thereafter from about 25% to about 35%, by volume, of the 
conductive oxide powder was added to melted polyethylene. The mixture was 
then mixed until a consistent mass was obtained. The mass was allowed to 
dry. Then the 4-point resistivity of the mass was obtained. The results 
indicated that conductive oxides having the general formula WO.sub.3-x, 
wherein x is greater than 0 and less than or equal to 1, have excellent 
conductive properties. 
TABLE I 
______________________________________ 
Conductive 
Volume % Density Resistivity 
Oxide Oxide (g/cm.sup.3) 
(ohm-cm) 
______________________________________ 
WO.sub.2.89 
33.5 7.17 2.04 
WO.sub.2.55 
30.2 8.3 0.52 
WO.sub.2.39 
30.2 8.45 0.45 
WO.sub.2 25.2 10.75 0.38 
______________________________________ 
EXAMPLE 2 
A control paste (100 grams) was prepared by combining the following 
ingredients: 
______________________________________ 
o-PbO (powder, no free lead) 
78.0 gm 
Sulfuric acid, specific gravity 1.325 
6.6 ml 
Modacrylic fibers, 1/16" long, 1.3 gm/cc 
0.05 gm 
Water 12.8 ml 
______________________________________ 
The sulfuric acid used contained about 42-43% by weight acid, the balance 
being water. The solids were premixed. The water was then added to the dry 
mixture followed by thorough mixing to obtain a uniform consistency. The 
acid was added last and mixed therein to cause the sulfate reaction to 
proceed. Mixing continued to obtain a uniform paste. 
A paste according to the invention was prepared in the same manner, except 
that 3.9 gm (about 5 wt. % based on the solids) of TiO.sub.1.77 powder was 
added to the mixture. 
The control and test pastes were uniformly coated on respective 
conventional lead-calcium alloy electrode grids of dimensions 6 by 4 by 
0.13 cm to a thickness of about 0.1 to 0.15 cm, and allowed to dry by 
standing at room temperature over night. The resulting grids (7 controls 
and 7 plates according to the invention) contained about 11-13 grams of 
active material. 
The grids were immersed in 150 ml of 1.185 specific gravity (SG) aqueous 
sulfuric acid in a standard lead acid battery including a pair of negative 
plates and a polypropylene separator, so that the positive plate was 
sandwiched between the two negative plates and separated therefrom by the 
separator, which was folded over both sides of the negative plate. A 
Hg/Hg.sub.2 SO.sub.4 reference electrode was also immersed in the acid 
electrolyte to one side of the test element. A current of 700 mA, which 
amounted to about 13.3 mA/cm.sup.2 when both sides of the positive grid 
were included, was applied to affect formation of the plates. Formation 
was continued for 8 hours The plates according to the invention were 
completely formed at the end of this time period. The control plates, 
however, were not completely formed, as indicated by their appearance. 
After formation, the plates were discharged at a 2 hour rate and the 
capacity of the plates was determined. The percent of PbO.sub.2 utilized 
was then calculated based upon the capacity. The plates according to the 
invention showed significant formation enhancement with the formation 
efficiency being very near 100%. Particularly, the plate according to the 
invention utilized 35-38% of the PbO.sub.2 while the control o-PbO plates 
utilized only 8-10% of the PbO.sub.2. 
EXAMPLE 3 
Several o-PbO plates having a paste coating according to the invention were 
prepared as described in Example 2. These plates and chemset plates 
(conventional battery plates) were immersed in 1.265 specific gravity 
sulfuric acid in sufficient quantity to completely cover the plate. The 
plates were then formed by conventional procedures. Thereafter, the plates 
were discharged, at a 2-hour rate, to a cut-off voltage of 1.75 volts. The 
capacities of the discharged plates were then determined. Then, the plates 
were recharged at a 2-hour rate with a 10% overcharge. This process of 
discharging, determining capacity, and recharging was repeated numerous 
times to determine the cycle life of the plates according to the invention 
as compared to conventional lead acid battery plates. The results 
indicated that the plates according to the invention were comparable to 
conventional battery plates in terms of cycle life. Thus, the plates 
according to the invention were found to enhance formation (as set forth 
in Example 2) with little to no effect on cycle life. 
EXAMPLE 4 
Several conductive tungsten oxides according to the present invention 
having various stoichiometries were obtained by heating commercial grade 
WO.sub.3 at various temperatures for various lengths of time, thus 
reducing the compound in accordance with the invention. The stabilities of 
each of the resulting powders were then determined by digesting a 
predetermined weight of the powder mixed with an equal weight of PbO.sub.2 
in sulfuric acid having a specific gravity of 1.305 g/cm.sup.3. The 
percent of the material which dissolved was determined after 9 days in 
those tests conducted at room temperature, and after 7 days in tests 
conducted at elevated temperatures. The results obtained are provided in 
Table II below. The data for commercial grade WO.sub.3 is provided for 
comparison. Nearly all percentage values obtained were under the threshold 
value of 1%, indicating that the conductive oxide compounds according to 
the present invention are stable. 
TABLE II 
______________________________________ 
Material Temp. (.degree.C.) 
Time/Days % Dissolved 
______________________________________ 
WO.sub.3 20 9 0.1 
60 7 0.1 
WO.sub.2.9 
20 9 0.7 
60 7 0.8 
WO.sub.2.6 
20 9 1.1 
60 7 0.9 
WO.sub.2 20 9 0.6 
40 7 0.6 
60 7 0.4 
______________________________________ 
EXAMPLE 5 
Several samples of titanium dioxide (TiO.sub.2) powder were reduced at 
various elevated temperatures and under a hydrogen atmosphere to various 
stoichiometries. Two of these samples were then incorporated into a 
polyethylene matrix by the process described in Example 1 in the amount of 
60% (volume percent). The resistivities of the resultant products, in 
either pure form or in a polyethylene matrix, were then determined as 
shown in Table III below. 
TABLE III 
______________________________________ 
Reduction 
Temperature Resultant Resistivity 
(.degree.C.) Stoichiometry 
(ohm-cm) 
______________________________________ 
850 *TiO.sub.1.86 
10.sup.6 
1100 *TiO.sub.1.77 
1.0 
1100 **TiO.sub.1.8 
2.31 
1160 **TiO.sub.1.76 
0.86 
______________________________________ 
*Denotes pure material 
**Denotes conductive oxide in polyethylene matrix 
EXAMPLE 6 
A 150 ml beaker was placed on a 370.degree. C. hot plate, covered with a 
watchglass, and allowed to heat. 2.0 g of polyethylene (melting index=45) 
were added to the beaker and melted. Enough conductive oxide having the 
general formula TiO.sub.1.77 was added to yield a resultant mixture 
containing 60% by volume of conductive oxide. The mixture was rubbed, 
mixed, and kneaded with a broadbladed steel spatula until a consistent 
mass was obtained. The mass was placed into a mold (preheated to 
370.degree. C. on a hot plate) and pressure was slowly applied with a 
press until the material flowed from the vent (between 5,000 and 10,000 
psi). The mold was cooled while in the press with water circulated through 
the platens. The resulting sheet substrate contained about 60% by volume 
powdered TiO.sub.1.77 in polyethylene. The sheet substrate was then 
immersed in a container filled with sulfuric acid having a specific 
gravity of 1.265. A constant voltage of 1.35 V vs. a Hg/Hg.sub.2 SO.sub.4 
reference was applied for 200 hours. The resistivity of the sheet 
substrate was periodically tested, as was the corrosion current within the 
container. It was observed that over the test period the corrosion current 
stayed low and the resistivity stabilized to about 9.2 ohm-cm at 200 
hours. 
EXAMPLE 7 
Samples of conductive oxides according to the invention were prepared to 
determine the effect on conductivity of volume percent of conductive oxide 
in a binder, such as polyethylene. Particularly, conductive oxides of 
molybdenum and tungsten were prepared by reduction of the MoO.sub.3 and 
WO.sub.3 in a hydrogen atmosphere. Varying amounts of the resultant 
powders having the general formulas of MoO.sub.3-x and WO.sub.3-x wherein 
X is greater than 0 and less than or equal to 1 were added to a 
polyethylene matrix as described in Example 1. The resisitivities of the 
various products were then determined, and the results are shown in Table 
IV below. It is clear that the resistivity of the conductive oxides 
according to the present invention when used in binders is dependent upon 
the volume percent of the conductive oxide. 
TABLE IV 
______________________________________ 
Conductive Volume % of Resistivity 
Oxide Conductive Oxide 
(ohm-cm) 
______________________________________ 
WO.sub.2 22.5 1.70 
25.8 0.66 
33.3 0.30 
53.8 0.03 
MoO.sub.2.12 15.0 29.41 
20.0 0.11 
30 0 0.01 
______________________________________ 
EXAMPLE 8 
A conductive oxide of niobium having the general formula Nb.sub.2 
O.sub.4.55 was prepared in a polyethylene matrix, as described in Example 
1. About 57% (volume percent) of the conductive oxide was utilized in the 
polyethylene matrix. The resistivity of this resultant material as 
determined by using the 4-point resistivity test was found to be 3.3 
kilo-ohm-cm. This resistivity illustrates that conductive oxides of the 
invention having the formula Nb.sub.2 O.sub.5-x, where x is greater than 0 
and less than or equal to 1, have fair to good conductive properties. 
It will be understood that the foregoing description is of preferred 
exemplary embodiments of the invention, and that the invention is not 
limited to the specific forms described. Modifications may be made to the 
methods and materials disclosed without departing from the scope of the 
invention as expressed in the appended claims.