Integrated primary-auxiliary electrodes formed on catalytic mesh-matrix-plaque with single-side-active-surface

An integrated primary-auxiliary electrode is provided for packaging into a battery container. The electrode includes a carrier substrate formed with a catalytic material. The electrode further includes a primary electrode which is formed on a first side of the carrier substrate with active electro-chemical materials for carrying out a charging-discharging cycle for the battery. The electrode further includes an auxiliary electrode which is formed on a second side of the carrier substrate by exposing the catalytic material of the carrier substrate thus acting to reduce an internal pressure of the battery when packaged into a battery container.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to the electrode structure and manufacture 
processes of rechargeable batteries. More particularly, this invention 
relates to an improved structure and manufacture process of battery 
electrode to provide battery with better performance while reducing the 
battery internal pressure and providing a more streamline manufacture 
processes to produce batteries at lower cost. 
2. Description of the Prior Art 
High internal pressure in the sealed battery cells often creates a 
hazardous conditions, when the pressure exceeds certain thresholds, which 
becomes a severe product liability concern for battery manufactures. 
Especially, since the sealed battery cells are now being widely used for 
every conceivable consumer products, to assure that the internal cell 
pressure would not exceed a limit in its entire life becomes a public 
safety issue. However, in the design and manufacture of different types of 
batteries, the internal pressure caused by gases produced by chemical 
reactions in the discharge or charge cycles still is a major technical 
difficulty. The inability and lack of effective solution to this problem 
often limits the product yield and unnecessarily increases the production 
costs of batteries. 
Matsumoto et al. disclose in U.S. Pat. No. 4,251,603 entitled `Battery 
Electrode` (Issued on Feb. 17, 1981), a battery electrode includes a 
plaque made of a sponge-like porous metal matrix having a multiplicity of 
cells connected with each other three-dimensionally. The sectional area of 
the gratings making up the sponge-like metal porous plaque decreases 
continuously along the thickness of the plaque from the surface toward the 
central part and an active material is impregnated in the porous plaque. 
The object of the patented invention is to provide a battery electrode 
comprising a plaque of a sponge-like porous metal matrix with high density 
of an active material impregnated in the plaque and the plaque can be 
produced at a low cost. Matsumoto et al. disclose a fundamental method of 
making battery electrodes. The basic technique as disclosed however does 
not provide an electrode to reduce the gas-pressure generated from 
chemical reactions with the battery cells. 
Dinker et al. disclose in U.S. Pat. No. 4,460,666, entitled "Coated 
Substrate, Preparation Thereof, and Use Thereof" (issued on Jul. 17, 
1984), a conductive substrate with major surfaces embossed and with at 
least on of the surfaces processed with a sintered porous metal powder 
coating. The special embossed surface increases the sintering speed, 
provides better handling in electrochemical cleaning and impregnation, and 
strengthens the adhesion of the active material to the surfaces of the 
substrate thus improves the integrity of the electrode. The difficulty of 
high cell gas pressure are not resolved by the use of special electrodes 
formed with such coated substrate. 
Kober et al. disclose in U.S. Pat. No. 4,707,911, entitled "Porous 
Electrodes and Method of Making Same" (issued on Nov. 24, 1987), porous 
electrodes for lead-add storage batteries without supporting plates or 
grids. Improved performance characteristics are achieved because these 
batteries are lighter in weight, having minimum internal resistance, 
providing higher rate of discharge, and more resistant to corrosion. The 
use of foams, metal nets, porous substrate, paste type of electrodes, and 
the fabrication methods of making those electrodes are disclosed in 
patents such as: U.S. Pat. Nos. 4,687,553, 5,455,125, 5,434,023, 
5,434,019, 5,432,031, 5,405,719, 5,384,216, 5,374,491, 5,348,823, 
5,329,681, 5,324,333, 5,248,510, 5,244,758, 5,098,544, 5,077,149, 
4,978,431, 4,975,230, 4,957,543, and 4,929,520. These disclosures provides 
a broad spectrum of techniques of making improved electrodes and 
batteries. Yet, none of them provides a solution to the technical 
difficulties of high gas cell pressure in a sealed battery. 
In order to reduce internal pressure, `auxiliary electrodes` are employed. 
As disclosed in Section 13.3.3 in `Battery Design` (See "Maintenance-Free 
Batteries-A Handbook of Battery Technology" by Brant, published by 
Research Study Press, Ltd. in year 1993) a prismatic sealed nickel-cadmium 
battery with auxiliary electrode is shown as that shown in FIG. 1. The 
negative (Cd) electrode is split into two plates, with an untilled nickel 
fiber electrode (A) interposed between the adjacent cadmium electrode. The 
negative electrodes are separated from a positive electrode (Ni) by 
spacers (S). The untilled plaque, i.e., the auxiliary electrode A, acts as 
a catalytic site for rapid oxygen reduction. The arrow indicated the main 
pathway for the oxygen in the gas phase to reach the untilled nickel 
substrate. As shown in FIG. 1, auxiliary electrode A which is composed by 
nickel fiber without impregnation are covered on both sides by the cadmium 
(Cd), i.e., the active hydrogen storage material for the negative 
electrode. 
The basic configuration as that shown in FIG. 1 becomes a typical electrode 
configuration when nickel mesh or sponge-like porous metal matrix are used 
in forming the negative electrode with the nickel fiber serves as 
auxiliary electrode. Please refer to FIG. 2 for the structure of a 
conventional electrode 10. This conventional electrode 10 includes a three 
layer structure, i.e., a first active layer 20 and a second active layer 
30 formed on two opposite sides of a carrier layer 40. The active layers 
20 and 30 are generally formed with hydrogen storage alloys and the 
carrier layer 40 is typically formed with nickel mesh or sponge-like 
porous metal matrix. Such structure is commonly employed in the electrodes 
as disclosed in the above prior art patents. The difficulty of high 
internal cell pressure is not resolved by this type of electrode 
construction. 
FIG. 3 shows an improved electrode 50 from the conventional electrode as 
shown in FIG. 2. The electrode 50 includes two primary electrodes 
consisting of a three layer structures, i.e., first primary electrode 
includes layers 60, 70, and 80, and second primary electrode includes 
layers 70, 80, and 90. These two primary electrodes are disposed on both 
sides, with an auxiliary electrode 95 disposed between them. The auxiliary 
electrode 95 provides a catalyst section to reduce the internal pressure. 
This configuration had the disadvantage that the manufacture of such an 
electrode is more complicate and more costly, and the surface areas 
provided for by the auxiliary electrode 95 is not sufficient to assure low 
internal pressure can be consistently achieved. 
Therefore, a need still exists in the art of design and manufacture of 
battery electrodes to provide an improved structural configuration and 
method of fabrication of electrodes. The improved electrodes must be 
effective to reduce the internal gas pressure and is simple to fabricate 
such that the time and cost of manufacture can be reduced. 
SUMMARY OF THE PRESENT INVENTION 
It is therefore an object of the present invention to provide an integrated 
primary-auxiliary electrode formed on a catalytic mesh-matrix plaque with 
a single-side-active-surface configuration which would enable those of 
ordinary skill in the art to overcome the aforementioned difficulties and 
limitations encountered in the prior art. 
Specifically, it is an object of the present invention to provide an 
integrated primary-auxiliary electrode formed on a catalytic mesh-matrix 
plaque with a single-side-active-surface configuration which provides 
simpler structure of the electrodes thus reducing the time and cost of 
battery manufacture. 
Another object of the present invention is to provide an integrated 
primary-auxiliary electrode formed on a catalytic mesh-matrix plaque with 
a single-side-active-surface configuration wherein the auxiliary electrode 
is provided with bigger area such that the internal pressure of a 
rechargeable battery is effectively reduced. 
Another object of the present invention is to provide an integrated 
primary-auxiliary electrode formed on a catalytic mesh-matrix plaque with 
a single-side-active-surface configuration for reducing the internal 
pressure thus eliminating the performance problems which may be caused by 
high internal pressures as that provided in the conventional batteries. 
Briefly, in a preferred embodiment, the present invention includes an 
integrated primary-auxiliary electrode for packaging into a battery 
container. The electrode include a carrier substrate formed with a 
catalytic material for gas reduction. The electrode further includes a 
primary electrode which is formed on a first side of the carrier substrate 
with active electro-chemical materials for carrying out a 
charging-discharging cycle for the battery. The electrode further includes 
an auxiliary electrode which is formed on a second side of the carrier 
substrate by exposing the catalytic material of the carrier substrate thus 
acting to reduce an internal pressure of the battery when packaged into a 
battery container. 
It is an advantage of the present invention that it provides an integrated 
primary-auxiliary electrode formed on a catalytic mesh-matrix plaque with 
a single-side-active-surface configuration which provides simpler 
structure of the electrodes thus reducing the time and cost of battery 
manufacture. 
Another advantage of the present invention is that it provides an 
integrated primary-auxiliary electrode formed on a catalytic mesh-matrix 
plaque with a single-side-active-surface configuration wherein the 
auxiliary electrode is provided with bigger area such that the internal 
pressure of a rechargeable battery is effectively reduced. 
Another advantage of the present invention is that it provides an 
integrated primary-auxiliary electrode formed on a catalytic mesh-matrix 
plaque with a single-side-active-surface configuration for reducing the 
internal pressure thus eliminating the performance problems which may be 
caused by high internal pressures as that provided in the conventional 
batteries. 
These and other objects and advantages of the present invention will no 
doubt become obvious to those of ordinary skill in the art after having 
read the following detailed description of the preferred embodiment which 
is illustrated in the various drawing figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 4 for an electrode 100 which has a novel and improved 
structure according to the teaching of the present invention. The 
electrode 100 include an integrated primary electrode 110 and an auxiliary 
catalytic electrode 120 disposed on two side of the electrode 100. The 
primary electrode 110 is formed with active hydrogen storage material to 
perform hydrogen absorption and desorption during the charging and 
discharging cycles. The auxiliary electrode 120 which formed on the 
opposite side of the primary electrode 110 on the electrode 100 is 
composed of nickel mesh, sponge-like porous metal matrix or other types of 
catalytic layer provided for gas, e.g., hydrogen and oxygen, reduction. 
The advantage of the integrated primary-auxiliary electrode structure as 
that shown for the electrode 100 in FIG. 4 is the expanded area of the 
auxiliary electrode 120. This expanded area of the auxiliary electrode 120 
serves as additional catalytic sites for enhancing the absorption of 
oxygen thus becomes very effective in reducing the internal pressure. 
FIGS. 5A and 5B show the microscopic pictures of the structure of the 
surface of the primary electrode 110 and the auxiliary electrode 120 
respectively. On the surface of primary electrode 110, uniform 
distribution is shown for a hydrogen storage material such as typical 
AB.sub.2 or AB.sub.5 material combinations formed thereon. In contrast, on 
the surface of the auxiliary electrode 120, a non-uniform distribution is 
shown wherein the white spots represent the exposed nickel-mesh or the 
sponge-like porous metal matrix which can be used as catalytic sites for 
reducing the oxygen on the entire surface. 
For the primary electrode which is formed on the first side of the 
integrated primary-auxiliary electrode, active hydrogen storage materials 
of AB.sub.2 and AB.sub.5 types of alloys can be applied which are 
disclosed in many U.S. Patents since 1980. Few examples of these 
inventions are: (1) U.S. Pat. No. 4,228,145 (issued on Oct. 14, 1980) 
claiming a hydrogen storage binary alloy. Laves phase intermetallic 
compound with a hexagonal MgZn2 (C14) type crystal structure with 
specified crystal structure parameters of a and c, and includes Zr & Mn, 
Ti & Mn, or Ti, Zr, & Mn. (2) U.S. Pat. No. 4,3710,163 (issued on Jan. 25, 
1983) claiming a hydrogen storage alloy, Ti.sub.1-x A.sub.x Fe.sub.y-z 
B.sub.z wherein A is Hf & Zr, B is from Cr, Cu etc. (3) U.S. Pat. No. 
4,551,400 (issued on Nov. 5, 1985) claiming active material for hydrogen 
storage electrode comprising the composition formula selected from the 
group consisting of: (a) (TiV.sub.2-x Ni.sub.x).sub.1-y M.sub.y where 
0.2.ltoreq.x.ltoreq.1.0, 0.0.ltoreq.y.ltoreq.0.2 & M=Al or Zr; (b) 
Ti.sub.2-x Zr.sub.x V.sub.4-y Ni.sub.y where 0..ltoreq.x.ltoreq.1.5, 
0.6.ltoreq.y.ltoreq.3.5; (c) Ti.sub.1-x Cr.sub.x V.sub.2-y Ni.sub.y where 
0..ltoreq.x.ltoreq.0.75, 0.2.ltoreq.y.ltoreq.0.1; and (d) TiV.sub.2-x 
Ni.sub.x where 0.4.ltoreq.x0.45. (4) U.S. Pat. No. 4,656,023 (issued on 
Apr. 7, 1987) claiming a hydrogen storage material comprising a ternary 
ahoy of Zr.sub.1-x Ti.sub.x CrFe.sub.y where 0.1.ltoreq.x.ltoreq.0.3, 
1.2.ltoreq.y.ltoreq.1.4; (5) U.S. Pat. No. 4,699,856 (issued on Oct. 13, 
1987) claiming a sealed rechargeable electrochemical cell includes a 
negative electrode which has a CaCu5-structure and the compositional 
formula AB.sub.m C.sub.n where m+n is between 4.8 and 5.4, n is between 
0.05 and 0.6 and (a) A consists of Mischmetall or one or more elements 
selected from the group consisting of Y, Ti, Hf, Zr, Ca, Th, La, and the 
remaining rare earth metals, in which the total atomic quantities of the 
elements Y, Ti, Hf, and Zr may not be more than 40% of A, Co) B consists 
of two or more elements selected from Ni, Co, Cu, Fe and Mn where the 
maximum atomic quantity per gram atom of A is for Ni:3.5, for Co:3.5, for 
Cu:3.5, for Fe 2.0, and for Mn:1.0, and (c) C consists of One or more 
elements selected from Al, Cr, & Si in the indicated atomic quantities: 
Al:0.05-0.6, Cr:0.05-0.5, and Si:0.05-0.5, characterized in that the 
electrochemically active material additionally comprises one or more 
metals selected from the group formed by P d, Pt, It, and Rh, the atomic 
quantity per gram atom of A being from 0.001 to 0.5; (6) U.S. Pat. No. 
4,728,586 (issued on Mar. 1, 1988) claiming a hydrogen storage alloy with 
composition (Ti.sub.2-x Zr.sub.x V.sub.4-y Ni.sub.y)Cr.sub.1-z where 
0.0.ltoreq.x.ltoreq.1.5, 0.6.ltoreq.y.ltoreq.3.5 & z is an effective 
amount less than 0.2, where at least one of the components is soluble in 
the alkaline media, and the alloy includes chromium as a modifier to 
inhibit the corrosion; and (7) U.S. Pat. No. 4,849,205 (issued on Jul. 18, 
1989) claiming a material for hydride hydrogen storage and a hydride 
electrode, the material comprising composition formula selected from four 
groups consisting of alloys made from different combinations of Ti, Cr, 
Zr, Ni, V, Mn, etc. These active hydrogen storage materials are well known 
examples of alloy compositions which may be applied as to the surface on a 
surface of the substrate carrier to form a primary electrode. 
Table 1 shows a comparison of the performance characteristics of a 
conventional electrode and an electrode of the present invention. 
Significant improvements are achieved in pressure reduction by the use of 
an integrated primary-auxiliary electrode 100 of the present invention. 
The greater catalytic active areas are provided for inducing and enhancing 
recombination are provide by the auxiliary electrode 120 which now 
constitutes the entire second surface of the electrode 120. 
TABLE 1 
______________________________________ 
Comparison of Internal Pressures in Battery Cells 
______________________________________ 
Battery Capacity 
1100 mAh 1100 mAh 
Positive Electrode 
Sinter Sinter 
Process (1100 mAh) 
Process (1100 mAh) 
Negative Electrode 
(1900 mAh) (1900 mAh) 
Conventional Integrated Primary - 
Electrode Auxiliary Electrode 
Internal Pressure 
20 to 30 Kg/cm.sup.2 
3 to 10 kg/cm.sup.2 
Charging Condition for 
1100 mAh for 2 Hrs 
1100 mAh for 2 Hrs 
Pressure Measurement 
______________________________________ 
The present invention discloses an integrated primary-auxiliary electrode 
100 which is for packaging into a battery container. The electrode 100 
includes a carrier substrate 120 formed with a catalytic material. The 
electrode 100 further includes a primary electrode 110 which is formed on 
a first side of the carrier substrate with active electro-chemical 
materials for carrying out a charging-discharging cycle for the battery. 
The electrode 100 further includes an auxiliary electrode 120 which is 
formed on a second side of the carrier substrate 120 by exposing the 
catalytic material of the carrier substrate thus acting to reduce an 
internal pressure of the battery when packaged into a battery container. 
An integrated primary-auxiliary electrode 100 as that shown in FIG. 4 
further provides an electrode structure which can be fabricated with 
simplified fabrication processes. The electrode can be fabricated by 
either a dry or wet process (see FIGS. 6A and 6B). In either processes the 
hydrogen storage material which can be of well known AB.sub.2 or AB.sub.5 
combinations are first processed by performing high temperature high 
vacuum alloy metallurgy process. Mixture combinations of Mn, V, Cr, Zr, 
Ni, Ti, and other metal elements to form a hydrogen storage alloy are 
deposited into a graphite container which is then placed in a high vacuum 
condition of approximately 10.sup.-6 TORR. An inductive heating process is 
performed by melting these metals at about 1700.degree. C. for more than 
thirty minutes. The melted alloy is poured into another container and 
cooled and then powderized by hydration and de-hydration processes. The 
alloy is further processed by ball-milling and crushed then sifted to form 
small particles in a particle size of approximately 70 .mu.m in diameter. 
In a dry process, the hydrogen storage fine particles of alloys are mixed 
with additive agents such as binder composed of PTFE which is further 
evenly distributed over one surface of the carrier substrate. The alloy 
particles together with the additive agent are then pressed to formed a 
primary electrode surface on the carrier substrate. The integrated 
primary-auxiliary board are then cut into a desire size for making 
negative electrode. In a wet process, the hydrogen storage alloy particles 
are mixed with binding material to form a paste-like mixture. The paste 
mixture is then spread over a surface of the carrier substrate to form the 
primary electrode surface of the integrated primary-auxiliary electrode. 
The spread paste over the carrier substrate is then dried and pressed. 
Which is then sintered at 800.degree. to 950.degree. C. for about three 
hours or cured at 300.degree. to 450.degree. C. for about one to three 
hours. The processed sample is then cut to a desirable size for making the 
negative electrode thus completing the wet process of making an integrated 
primary-auxiliary electrode. This one-sided structure with only one of the 
two surfaces formed with an active hydrogen storage layer which is either 
being spread or pressed thereon simplify the fabrication process and 
reduce the cost of electrode fabrication. 
Therefore, the present invention discloses an integrated primary-auxiliary 
electrode formed on a catalytic mesh-matrix plaque with a 
single-side-active-surface configuration which would enable those of 
ordinary skill in the art to overcome the difficulties and limitations 
encountered in the prior art. Specifically, the integrated 
primary-auxiliary electrode formed on a catalytic mesh-matrix plaque with 
a single-side-active-surface configuration as disposed in this invention 
provides simpler structure of the electrodes thus reducing the time and 
cost of battery manufacture. Additionally, on this integrated 
primary-auxiliary electrode which is formed on a catalytic mesh-matrix 
plaque with a single-side-active-surface, an entire catalytic surface is 
used as the auxiliary electrode which provides bigger area as an auxiliary 
electrode such that the internal pressure of a rechargeable battery can be 
effectively reduced. Furthermore, by the use of the electrodes as provided 
in this invention, with the reduced internal pressure in the rechargeable 
batteries, many of the performance problems caused by the pressure 
difficulties as encountered in the conventional batteries are eliminated. 
Although the present invention has been described in terms of the presently 
preferred embodiment, it is to be understood that such disclosure is not 
to be interpreted as limiting. Various alternations and modifications will 
no doubt become apparent to those skilled in the art after reading the 
above disclosure. Accordingly, it is intended that the appended claims be 
interpreted as covering all alternations and modifications as fall within 
the true spirit and scope of the invention.