JPH0365624B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrodes for use in electrochemical energy cells.

Bifunctional air electrodes for metal-air batteries, such as iron-air batteries, generally consist of three components. These three ingredients are described in U.S. Patent No. 4152489 issued to Chottiner et al.
As disclosed in the specification, a two-component active layer comprising: a hydrophobic layer that allows air flow and retains the electrolyte; a two-component active layer that is attached to the hydrophobic layer and contains a catalytically active pasty material; and a plurality of porous metal fiber current collectors containing a substance. This hydrophobic layer is preferably a sheet of porous, unsintered, fully fibrillated polytetrafluoroethylene alone or combined with a plasticizer such as polymethyl methacrylate and dialkyl phthalate. , a sheet of unfibrillated fluorinated ethylene propylene, fibrillated polytetrafluoroethylene, and polypropylene fibers.

The active pasty material is disclosed in U.S. Patent No. 4,152,489 to Chottiner et al.
No. 1 and U.S. Pat. No. 3,977,901 to Buzzelli.
WS ₂ coated with oxygen-absorbing/reducing carbon with a BET total surface area per gram of 30-1500 m ² and a suitable catalyst, e.g. 1-20% by weight Co (cobalt).
or WC, and a polytetrafluoroethylene dispersion which acts as a non-wetting binder. The active paste consisting of the above mixture is mixed with deionized water, but no particle size change or weight change is made in the thickness direction of the active layer.

In order to improve the operating characteristics of the battery, the electrolyte must sufficiently penetrate inside the electrode and reach the inner surface of the electrode.
Requires contact with air or other gas in the presence of a catalyst. At the same time, the electrode must have sufficient electrolyte-repellent properties to prevent electrolyte flooding, ie, electrolyte overflowing from the pores of the electrode. Fluctuation of the electrolyte has always been a problem with air electrodes, and the structure proposed by Chyotteiner and the active paste composition proposed by Buselli, described in the prior U.S. patents cited above, are sufficient to accommodate the above-mentioned problem. Although it provides stable electrical properties over approximately 100 usage cycles, an improved structure or improved composition is strongly desired, especially to reduce electrolyte flattening. It is desired to avoid this completely.

U.S. Patent No. 1, issued to Darland Jr., et al.
It is disclosed in the specification of No. 3423247. One zone adjacent to the gas supply consists of low surface area large particles of 30-70% by volume polytetrafluoroethylene, which is non-wetting and does not contain catalyst. The other area adjacent to the electrolyte consists of wet-functional, high surface area, small particle size catalyst-attached particles. The area adjacent to the gas supply is provided with a single mesh size current collector. However, such structures do not completely achieve the intended purpose, and there is a need for electrodes for metal-air cells and fuel cells that provide maximum output and minimal flooding.

Accordingly, the present invention provides an electrode for use in an electrochemical energy cell, comprising a porous support sheet;
a catalytically active layer adhered to the porous support sheet and having an electrolyte permeable side surface and a side surface in contact with the support sheet, the catalytically active layer comprising a hydrophobic mass and a hydrophilic mass. consisting of a mixture and a catalyst, the particle size of the hydrophobic aggregates and hydrophilic aggregates increasing from the electrolyte permeable side toward the support sheet contacting side, and from the electrolyte permeable side toward the support sheet contacting side. It is an object of the present invention to provide an electrode characterized by an increased weight ratio of hydrophobic substance to hydrophilic substance.

In one embodiment of the invention, the electrode is an air electrode, the support sheet of the air electrode is hydrophobic, and a catalytically active layer is laminated to the hydrophobic support sheet;
At least two porous metal current collectors are arranged in the catalytic active layer, and the hydrophobic aggregates are oxygen absorbing/reducing carbon particles with a total surface area of 30 to 300 m ² per gram;
Consisting of a catalyst, a substance with low oxygen overpotential and a non-wetting binder based on fluorocarbons, the active hydrophilic mass has a total surface area of 30 to 300 m2 ^per gram of oxygen absorption/
It consists of reduced carbon particles, a catalyst and a low oxygen overpotential material, a non-wetting binder based on fluorocarbons, and an organic dispersant that lowers the surface tension of the liquid between the active hydrophilic masses, The active hydrophilic substance:active hydrophobic substance weight ratio was varied from a ratio of 1:0.2 on the side with high electrolyte permeability to a ratio of 1:5 on the side in contact with the hydrophobic support sheet. It is being

Preferably, a suitable catalyst, such as silver, is deposited and coated onto the carbon particles.

Initially, all active substances are hydrophilic, but when a portion of the active substance is heat-treated to decompose the dispersant into fluorocarbon, this hydrophilic substance turns into a hydrophobic substance and the surface tension of the dispersant decreases. is no longer present, the flow of the electrolyte due to capillary action increases, and the electrolyte is retained by the hydrophobic substance. The weight percentage ratio of active hydrophilic substance to active hydrophobic substance in the active layer is generally 40%:60%. Variation in the thickness direction of the active layer of the electrode (active hydrophilic substance):
The weight ratio of (active hydrophobe) is in the range from 1:0.2 on the side in contact with the electrolyte to 1:5 on the side in contact with air. By adopting such a structure, the catalyst is dispersed throughout the active layer, achieving a good balance between hydrophobic and hydrophilic areas, and maintaining the three-phase structure of electrolyte, air, and catalyst throughout the thickness of the active layer. Interfacial contact can be maximized. As used herein, the term "air" is used to include oxygen. In metal-air cells, current is collected from all metal support current collectors simultaneously. It was dramatic that stable electrical properties were obtained for up to about 300 cycles without problems with electrode flattening or peeling due to trapped gases.

In order that the invention may be more fully understood, preferred embodiments will now be described by way of example with reference to the accompanying drawings, in which: FIG.

In FIG. 1, the illustrated cell 10 is a general example of a metal/air cell according to the present invention employing a bifunctional air electrode. The metal/air battery 10 has a case 11 that holds an air electrode, a metal electrode, and an electrolyte. The case 11 is preferably made of a non-conductive material such as ABS plastic that is stable or resistant to electrolytes and reaction products such as oxygen and hydrogen. The battery 10 has a pair of air electrodes 12 and 13, each electrode covered with a hydrophobic sheet 14.
and 16, each hydrophobic sheet being in contact with the atmosphere or other air or oxygen source. Air electrodes 12 and 13 have a plurality of active material sections 17 and 18, each active material section consisting of an active material contained in a porous metal plaque. These sections have integral metal current collectors 19 and 21.
is installed. The active layer is made up of multiple active material sections. Electrodes 12 and 13
are housed in frames 22 and 23, preferably made of ABS resin, and have electrical leads 24 and 26, respectively.
is attached.

The metal/air cell 10 is made of a material such as iron, cadmium, zinc, etc., preferably iron, and is spaced apart from the air electrodes 12 and 13, with electrical leads 2
It has a metal electrode 27 with 8 attached. The metal/air battery 10 contains an electrolyte 29.
9 is inserted between the metal electrode 27 and the air electrodes 12 and 13, and the metal electrode 27 and the air electrode 1
2 and 13, respectively. Electrolyte 29 consists of alkali hydroxide, preferably potassium hydroxide.

Details of the electrode 12 shown in FIG. 1 are shown in FIG. As shown in FIG. 2, this electrode has a layered structure. The illustrated anode 12 includes an active layer 17 and a porous hydrophobic support sheet 14 laminated with the active layer 17.
and a plurality of active substance categories. metal/
The current collector 19 used in the air battery is inserted into the active layer 17 as shown and electrically connected to the circuit. In a preferred embodiment, at least two current collectors are used. The active substance 30 includes both hydrophilic masses 31 and hydrophobic masses 32 which cover and are associated with the current collector 19 and are not shown to simplify the drawing. has at least partially penetrated the current collector 19.

Current collector 19 can be made from drawn metal, such as nickel. It can also be made from iron or steel coated with drawn nickel. Preferably, it is made from nickel-coated iron or steel fiber metal or uncoated nickel, iron or steel fiber metal, such as nickel or steel wool.
The most preferred metal fibers are fibers that are 1.5 inches or longer in length and are bonded together by diffusion bonding. Typical fiber diameter is approximately 0.0051~0.127mm
(0.0002 to 0.005 inch). Diffusion bonding techniques are well known and are described in detail in US Pat. No. 4,152,489. Plate-shaped current collector 19 made by diffusion bonding nickel fiber wool in this way
The porosity is 75%~95%, the thickness is 0.127~1.27mm
(0.005 to 0.050 inch). When used as an electrode for a fuel cell, the current collector may be omitted.

The thickness of active layer 17 when used in metal-air cells is 0.254-3.81 mm (0.010-0.150 inch); the thickness of active layer 1 when used in fuel cells is
7 thickness is 0.127~0.762mm (0.005~0.030 inch)
It is. The thickness of the porous hydrophobic support sheet 14 is
0.127 to 0.508 mm (0.005 mm for metal-air batteries)
~0.020 inch), 0.051~ for fuel cells
Make it 0.508mm (0.002-0.020 inch). The porous support sheet 14 may be a layer or sheet formed by compressing powdered polytetrafluoroethylene, a sheet consisting only of polytetrafluoroethylene fibers ground into fibrils, or a sheet made of polytetrafluoroethylene fibers that have been subjected to fibrilization treatment. untreated fluorinated ethylene/propylene fibers, carbon powder or carbon fibers, polypropylene, polyethylene, and other well-known analogues, either one or two or more of them in any combination; A sheet made of tetrafluoroethylene fibers can be used.

The plurality of active material sections forming the active layer 17 are:
For example, they can be formed by individual cold pressing, which is particularly suitable for metal-air battery applications, and then brought together by hot pressing or roll lamination into a strong laminated structure. Then 1.76~ at 190℃~350℃
By applying air pressure of 52.7 Kg/cm ² (25 to 750 psi), the solidified active layer 17 and the hydrophobic sheet 14 can be integrated by pressure or roll lamination.
Alternatively, a porous support sheet may be applied during the active layer lamination process.

As can be seen from FIG. 2, the catalytically active material 30 forming the active layer is composed of a mixture of a hydrophobic substance with catalytic activity and a hydrophilic substance with catalytic activity.
Both of these agglomerates increase in particle size from the side 33 of the electrode in contact with the electrolyte to the side 34 in contact with air. Furthermore, the weight percentage of the hydrophobic substance in the active layer 17 increases from the electrolyte contacting side 33 to the air contacting side 34 . The weight percentage of (active hydrophilic substance): (active hydrophobic substance) inside the active layer 17 is approximately (30% to 50%): (50% to 70%), typically approximately 40%:60%. It is. The weight ratio of (active hydrophilic substance) to (active hydrophobic substance) in the thickness direction of the active layer 17 is approximately 1:0.2 on the side in contact with the electrolyte.
, to a ratio of about 1:5 on the side in contact with the air, ie, on the side contacting the porous support sheet.

By way of example, active substance category A has a particle size of approximately
1.5 parts of 800 micron hydrophilic material and particle size approx.
and 0.5 part of a 650 micron hydrophobic substance. Active material segment B shall contain 1.5 parts of a hydrophilic material with a particle size of about 800 microns and 1.5 parts of a hydrophobic material with a particle size of about 650 microns. Category C is a hydrophilic substance with a particle size of approximately 1000 microns 1.0
1 part and 2.0 parts of a hydrophobic material with a particle size of about 700 microns. Category D is particle size approx.
0.5 parts of hydrophilic material of 1100 microns and particle size approx.
2.5 parts of a 1100 micron hydrophobic substance. As a result, the particle size of the hydrophilic substance increases from 650 microns on side 33 to 1100 microns on side 34, and the hydrophilic:hydrophobic weight ratio increases from 1:0.5 on side 33 to 1:5 on side 34. The configuration will be increased.

The essential requirements of the present invention are that the active layer has electrochemical activity as a whole, that the active substance in each active segment consists of a homogeneous mixed composition of both hydrophilic and hydrophobic substances, and that the electrolyte There is a size gradient of agglomerated particles and a weight ratio gradient throughout the active layer of the electrode structure from the side in contact with the air to the side in contact with air. This technical concept significantly reduces the problem of electrolyte flooding after long-term use cycles, and almost idealizes the three-phase interfacial contact between the electrolyte, air or oxygen, and catalyst contained in the active layer throughout the active material. It can be in a state of As used herein, the phrase "hydrophilic material" refers to a mass through which an electrolyte can flow. The term "hydrophobic material" refers to a mass that retains or prevents the passage of electrolyte, but allows air to pass through easily. What is important here is that the catalyst is evenly distributed throughout the active layer and that the porous support layer 14
The catalyst distribution is the same in section D adjacent to
The non-wetting binder is also equally distributed throughout the active layer, and also in section A adjacent to the electrolyte contact side 33. This point will be discussed later.

The catalytically active material contained in each active material segment A, B, C and D, designated 30 in Figure 2, preferably has a total BET surface area per gram of approximately
30 to about 300 m ² of oxygen-absorbing/reducing carbon, a suitable catalyst such as silver, preferably coated on the surface of the carbon particles or contained inside the carbon particles, and preferably a metal with a low oxygen overvoltage. Adducts such as _CoWO4 , _WS2 , nickel spinels, preferably NiS, Fe, _WO4 ,
WC and a metal adduct such as WC coated with 1 to 20% by weight of Co (cobalt) and a fluorocarbon-based particulate dispersant as a non-wetting binder, preferably a polytetrafluoroethylene dispersant. A dispersant is a substance that evaporates or decomposes when heated, reducing the surface tension between the fluorocarbon particles and other particles and increasing the flow of the electrolyte by capillary action between the particles in the active material. It is a substance that promotes Examples of dispersants that can be used include, for example, sodium aralkyl polyester sulfonate, sodium aralkyl polyester sulfate, sodium aralkyl ether sulfate, aioctyl sodium sulfosuccinate,
Anionic surfactants such as phosphoric acid esters in acid form or mixtures thereof, such as octyl phenol ether alcohol, octyl phenol polyether alcohol, nonyl phenol polyether alcohol, alkyl phenol polyether alcohol, etc.
Polyether/alcohol, alkylaryl/
Mention may be made of nonionic surfactants, such as polyethylene glycol ethers or mixtures thereof, and mixtures of nonionic and anionic surfactants, which are well known in the art. It is a drug. Cationic surfactants with a negative charge tend to interfere with electrolyte penetration and are not particularly suitable for use.

Preferred carbons for use in the present invention are in the form of fluff, consisting of a plurality of independent particles linked together in a chain, examples of which include acetylene black. When using pressurized material in pellet form, it may be ground to a particle size suitable for use. 176Kg/ ^cm2
The low resistivity of acetylene black at (2500 psi) is 0.57-3.60 ohm/ ^cm3 (0.035-0.22 ohm/cm3).
It has a low value (in cubic inches) and is an excellent electronic conductor. The bulk specific gravity of acetylene black is approximately 0.019
g/cm ³ (1.20 lbs/cubic foot) and the particle size is 0.005 to 0.13 microns, with each particle having several open pores with dimensions at the outer surface of 0.002 microns or more. Most of the surface area of acetylene black is occupied by the outer surface, with only a few channels. Some type of channel carbon black may also be used. The preferred BET total surface area range of carbon is 30-300 m ² per gram.

When used as a bifunctional air electrode in a metal-air cell, the carbon acts as a surface that generates oxygen during electrode charging. Depending on the electrode application, the carbon can also serve as a support surface for silver, nickel, platinum, or other suitable catalysts that can be attached to the carbon. One method of depositing silver, the preferred catalyst for use in metal-air cells, is to deposit carbon.
Mix with AgNO ₃ solution and use hydrazine to precipitate the silver onto the carbon. Various forms of carbon, BET for surface area measurements (Brunauer,
A more complete description of the Emmett and Teller process, as well as various low oxygen overpotential metal adducts, is provided in US Pat. No. 3,977,901.

A very important feature is that after mixing all the ingredients, all the above catalytically active materials are heated at 25°C to 30°C.
Air dry for 12 to 48 hours to make everything an active hydrophilic material. Next, a part of this hydrophilic substance is
Heat treatment is performed by drying in an oven at 250° C. to 325° C. for about 1 to 3 hours in air or in a flowing gas atmosphere. Through this heat treatment, the dispersant for the fluorocarbon is thermally decomposed or evaporated to become a hydrophobic substance. This hydrophobic substance retains the electrolyte because it has a low surface tension because there is no dispersant, which is usually a surfactant, and the electrolyte flows easily due to capillary action.

The particle size of the air drying part and the heat treatment part is divided into multiple particle groups ranging from 150 microns to 2000 microns for metal-air batteries, and 30 to 300 microns for fuel cells. into particle populations. These several particle populations are mixed in appropriate amounts to create a weight ratio gradient within the range described above. The term "agglomerates" refers to extremely fine carbon particles, coarse-grained fluorocarbon materials associated with these carbon particles, and metal adduct particles that are particularly useful in metal-air battery applications. It means a complex agglomerate consisting of. The particle size of the agglomerates ranges from 0.5 to 50 microns for metal-air cells and from 50 to 200 microns for fuel cells.

The amount of fluorocarbon-based non-wetting binder (on a solids basis) in both the hydrophilic and hydrophobic materials may vary from about 10% to about 50% by weight of the total composition. I can do it. Generally, fluorocarbon dispersions contain about 50% to 60% fluorocarbon solids and 5%
~10% dispersant, with the balance being water. Add 0.25 to 5 of a substance with low oxygen overvoltage to 1 part of carbon.
part can be added. These materials may also act as pore formers and prevent catalyst dissociation. 2% to 10% by weight, preferably 2% by weight on carbon
It is common to include up to 5% by weight of silver or other suitable catalysts.

The above-mentioned electrodes are particularly suitable for use in electrochemical energy cells, in combination with metal electrodes of iron, zinc, cadmium or aluminum, etc., with the intermediate part of the electrode in contact with both electrodes. A battery can be made by adding an alkaline hydroxide electrolyte.

The electrodes described above can be used as electrodes within a variety of fuel cells, such as room temperature alkaline fuel cells and high temperature phosphoric acid fuel cells, which are well known in the art. In a fuel cell, a fuel electrode is in contact with a fuel such as hydrogen gas, an air electrode is in contact with air or oxygen, and an electrolyte is in contact with the fuel electrode and the air electrode. For this type of application, the electrode of the present invention can be used as either a fuel electrode or an air electrode.
An electrolyte such as potassium hydroxide or phosphoric acid is placed between the fuel electrode and the air electrode. A complete description of fuel cell operation and standard electrode construction can be found in US Pat. No. 3,935,029, which is incorporated herein by reference.

The invention will now be illustrated by way of examples.

Example An air electrode measuring 11.4 cm x 14.3 cm was made. The BET surface area is approximately 60 to 70 m ² /1 g [Shawinigan Products Corporation (Shawinigan
Products Corp.) with the trade name Syaouinigan.
Dry acetylene black particles (commercially available under the name Shawinigan Black) were mixed with AgNO ₃ in a wet slurry. Hydrazine was then added to deposit silver onto the carbon particles. Excess water was then removed by vacuum and the paste was air-dried for 24 hours. Sufficient amount of AgNO ₃ solution was used to bring the silver content on the carbon particles to 3-4% by weight. 4.5 g of NiS and 4.5 g of FeWO ₄ to 30 g of these silver-deposited carbon particles.
and 4.5 g of WC coated with 12 wt% Co, 7.
adding 12 g of polytetrafluoroethylene aqueous dispersion containing 2 g of solid polytetraethylene and about 1.0 g of octylphenol polyester alcohol nonionic surfactant dispersant and 170 ml of water; A slurry was formed. The slurry was air dried on a screen at 25° C. for 24 hours to obtain the active hydrophilic material.

A low oxygen overpotential mixture was present at 0.45 parts per part carbon, and about 14% by weight of the air-dried catalyst-containing material was used as polytetrafluoroethylene solids. Approximately 60% by weight of the air-dried, catalyst-coated material was placed in an oven for 300 min.
C. for 2 hours to evaporate and decompose the nonionic surfactant, creating a heat-treated active hydrophobe. Since the surfactant is no longer present, this material has little penetration of the electrolyte into the capillary tubes. Although equal amounts of catalyst and polytetrafluoroethylene were present in the active hydrophilic and active hydrophobic materials, both materials were sieved to a particle size of 793.
It was divided into batches of hydrophilic agglomerates of micron and particle size 1098 microns and batches of hydrophobic agglomerates of particle size 660 micron, particle size 793 micron and particle size 1098 micron.

An air electrode with a structure similar to that shown in Figure 2 was constructed using four 11.4 cm x 11.4 cm x 0.025 cm dispersively bonded nickel fiber wool plates with a porosity of 94% as current collectors. . Electrical lead tabs were welded to the top edges of all plates. Multiple catalytically active material categories were stacked as shown below. Note that HL below indicates an active hydrophilic substance, and HP indicates an active hydrophobic substance.

Category A (adjacent to electrolyte) HL with particle size 793 microns
1.2g of HP with a particle size of 660 microns and 0.8g of HP with a particle size of 793 microns.Nickel fiber plate section B (adjacent to section A) HL with a particle size of 793 microns.
1.2g of HP with a particle size of 660 microns and 1.8g of HP with a particle size of 1098 microns. Nickel fiber plate section C (adjacent to section B)
1.0 g of HL, 1.5 g of HP with a particle size of 660 microns and 0.5 g of HP with a particle size of 793 microns Nickel fiber plate section D (adjacent to the air contact side) 0.8 g of HL with a particle size of 1098 microns and HP with a particle size of 1098 microns 0.5
1.7 g of HP with a particle size of 793 microns on a nickel fiber plate. Each section consisting of the active material with attached catalyst is cold pressed into the corresponding nickel fiber plate at a pressure of 176 kg/cm ² (2500 psi) and placed on the plate. coated,
At least a portion was allowed to penetrate inside the plate.

At this point, the carbon black particles and polytetrafluoroethylene are mixed in a crusher, the polytetrafluoroethylene is crushed into fibrils, and the crushed mixture is crushed under a pressure of 176 kg/cm ² (2500 psi). A hydrophobic sheet was created by cold pressing into a sheet shape. This hydrophobic sheet was placed on the platen of a heated bed press and sections D, C, B and A were stacked on top to form an electrode stack. This entire pile was pressed to 281Kg/ ^cm2 using a heated bed press.
The electrode was heated and pressed at 300° C. under a pressure of 4000 psi to obtain an integrated air electrode having a structure similar to that shown in FIG.

The active layer of the obtained air electrode consists of 38% by weight of hydrophilic substance and 62% by weight of hydrophobic substance, excluding the weight of the nickel fiber plate, and the weight of active hydrophilic substance: active hydrophobic substance is The ratio is 1.2:0.8 or 1:0.67 in the section adjacent to the side in contact with the electrolyte and 0.8:(0.5+1.7) or 1:2.5 in the section adjacent to the hydrophobic sheet in contact with air. It was hot. Regarding the particle sizes on the electrolyte side and the air side, the particle size of the hydrophilic substance increased from 793 microns to 1098 microns, and the particle size of the hydrophobic substance increased from 660 microns to 1098 microns.

A compacted air electrode with four active substance sections and four current collectors was used as one side of a rectangular plastic container filled with an electrolyte consisting of a 25% KOH solution, and a hydrophobic sheet was used as the air source. and section A of the air electrode was brought into contact with the electrolyte. As shown in Figure 1, the air electrode is incorporated into the plastic frame, so the active surface size is approximately 8.3
cm x 9.5 cm (3 1/4 inches x 3 3/4 inches). The opposite side of the cell is formed of a flat nickel sheet, which acts as the counter electrode. The side surface of the nickel counter electrode was covered with a polytetrafluoroethylene sheet to prevent contact with the electrolyte. A Hg/HgO reference electrode was inserted into the electrolyte between the nickel sheet and the air electrode and electrically connected as appropriate. This cell with an air electrode according to the invention was used 250 times, each cycle being discharged for 4 hours at 25 mA/cm ² and 12.5
A charging operation was performed at mA/cm ² for 4 hours.

Oxygen reduction voltage vs. number of cycles in Figure 3 and Figure 4
In the graph showing the oxygen generation voltage versus the number of cycles shown in the figure, curve A is a graph showing the operating characteristics of the battery using the air electrode according to the present invention. As can be seen from the drawings, the air electrode according to the present invention, which has stepwise changes in both dimensions and weight across the active layer, exhibits stable electrical characteristics without exhibiting large voltage changes. This indicates that there is no uncontrolled electrolyte flooding in any of the active sections and no delamination of the structure due to oxygen scavenging in any of the active sections. The test was continued and the curve remained stable until 300 times. These remarkable results demonstrate the superiority of the electrode according to the invention and its suitability for use in non-flooding metal-air cells. B in each graph
The comparative product shown in will be explained next.

A 11.4 cm x 11.4 cm dispersion-bonded 94% porous nickel fiber wool plate was used as a current collector and a 11.4 cm x 11.4 cm dispersion-bonded 94% porous nickel fiber wool plate was used as the current collector.
created an air electrode. The ingredients and amounts used as materials for the active substance were the same as in the examples, and the amount of the mixture of substances with low oxygen overvoltage was about 0.45 parts per part of carbon, and the amount of the mixture of substances with low oxygen overvoltage was about 0.45 parts to 1 part of carbon. The weight equivalent to 14% by weight was accounted for by solid polytetrafluoroethylene. A portion of the air-dried catalyst-deposited material was calcined to produce a hydrophobic material as described in the Examples. The amount of catalyst and the amount of polytetrafluoroethylene present in both the active hydrophilic substance and the active hydrophobic substance are the same, and both substances are sieved to form hydrophilic lumps and hydrophobic lumps with a particle size of about 2500 microns. I got something.

The catalytically active material categories were stacked as described below. HL indicates a hydrophilic substance, and HP indicates a hydrophobic substance.

Category A (adjacent to electrolyte) Particle size approximately 2500 microns
1.5g of HL in nickel fiber plate section B (adjacent to section A) with a particle size of approximately 2500 microns.
1.5g of HL on a nickel fiber plate section C (adjacent to section B) with a particle size of approximately 2500 microns.
1.5g of HL in nickel fiber plate section D (adjacent to the air contact side) 1.5g of HL with a particle size of approximately 2500 microns and HP with a particle size of approximately 2500 microns
0.4 g of the nickel fiber plate. That is, unlike the example, there is no homogeneous mixture of hydrophilic and hydrophobic aggregates in the active layer, and the particle size or weight ratio in the direction across the active layer is There are also no gradual changes.

As in the examples, each section of the catalyst-adhered active layer was cold-pressed into a corresponding nickel fiber plaque, stacked, and compacted by heating and pressing onto a hydrophobic sheet to form 4 active material sections and 4 sections. A monolithic air electrode with several current collectors was obtained. The comparative air electrode obtained in this way was used as an air electrode of a battery, and the same procedure as in the example was carried out, at a rate of 25 mA/cm ^{2 .}
A cycle of discharging for 4 hours at 12.5 mA/cm ² and charging for 4 hours at 12.5 mA/cm 2 was repeated 250 times.

Graphs of oxygen reduction voltage and oxygen generation voltage with respect to the number of cycles shown in FIGS. 3 and 4 were drawn. Curve B in each graph shows the operating characteristics of a battery using this comparative air electrode. As can be seen from the figures, curve B in both graphs shows large voltage changes, indicating instability during 250 cycles.

As mentioned above, the multilayer laminated electrode according to the present invention in which the particle size and weight ratio are graded can also be applied to fuel cells.

[Brief explanation of drawings]

FIG. 1 is a perspective view, in cross-section, of a portion of one type of air/metal cell employing electrodes according to the present invention. FIG. 2 is an enlarged cross-sectional view of the electrode of FIG. 1, showing the particle size gradient of hydrophobic and hydrophilic substances throughout the active layer. FIG. 3 is a comparative graph showing oxygen generation voltage versus number of cycles. FIG. 4 is a comparative graph showing oxygen generation voltage versus number of cycles. 10... Battery, 11... Case, 12, 13...
...Air electrode, 14,16...Hydrophobic sheet, 1
7, 18... Active substance section, 19, 21... Metal current collector, 22, 23... Plastic frame, 24, 26... Electrical lead, 27... Metal electrode, 29... Electrolyte.

Claims (1)

[Scope of Claims] 1 Comprising a porous support sheet and a catalytically active layer attached to the porous support sheet and having an electrolyte permeable side surface and a side surface in contact with the support sheet, the catalytically active layer is composed of a mixture of hydrophobic lumps and hydrophilic lumps and a catalyst, and the particle size of the hydrophobic lumps and hydrophilic lumps increases from the electrolyte-permeable side to the supporting sheet contact side, and the electrolytic An electrode characterized in that the weight ratio of hydrophobic substance to hydrophilic substance increases from the liquid-permeable side surface to the support sheet contact side surface. 2. An organic dispersant in which the hydrophobic substance consists of carbon particles and a carbon fluoride substance, and the hydrophilic substance functions to reduce the surface tension of a liquid between the carbon particles, the carbon fluoride substance, and the hydrophilic aggregate. An electrode according to claim 1, characterized in that the catalyst is distributed equally throughout the active layer. 3. The electrode is an air electrode, the support sheet of the air electrode is hydrophobic, a catalytic active layer is laminated on the hydrophobic support sheet, and at least two porous metal current collectors are disposed within the catalytic active layer. The hydrophobic mass consists of oxygen-absorbing/reducing carbon particles with a total surface area of 30 to 300 m2 ^per gram, a catalyst, a substance with low oxygen overpotential, and a non-wetting binder based on fluorocarbons. , a catalytically active hydrophilic mass with a total surface area of 30 to 300 m ² per gram of oxygen-absorbing/reducing carbon particles, a catalyst, a substance with a low oxygen overpotential, a non-wetting binder based on hydrogen fluoride, a catalytically active and an organic dispersant that acts to reduce the surface tension of the liquid between the hydrophilic aggregates, and the weight ratio of the catalytically active hydrophilic substance to the catalytically active hydrophobic substance is 1: on the side with high electrolyte permeability. 3. An electrode according to claim 1, characterized in that the ratio varies from 0.2 to 1:5 on the side surface in contact with the hydrophobic support sheet. 4. The current collector in the active layer is a metal fiber structure,
The catalyst in the active layer functions to decompose peroxides, and the substance with low oxygen overvoltage in the active layer is CoWO ₄ ,
WS ₂ , spinel type nickel, NiS, FeWO ₄ , WC
The electrode according to claim 3, wherein the electrode is WC coated with 1 to 20% by weight of Co, or a mixture thereof. 5. Claim No. 5, characterized in that the fluorocarbon binder in the active layer is polytetrafluoroethylene, the catalyst in the active layer is silver, and the silver is deposited on the carbon particles. The electrode according to item 3 or 4. 6. The electrode according to claim 3, 4, or 5, wherein the organic dispersant is an anionic surfactant, a nonionic surfactant, or a mixture thereof. 7 The organic dispersant is octyl phenol ether alcohol, octyl phenol polyether alcohol, nonyl phenol polyether alcohol, alkyl polyether alcohol, alkylaryl polyethylene glycol ether, or a mixture thereof. The electrode according to claim 6, characterized in that: 8. The electrode according to any one of claims 3 to 7, wherein the particle diameter of the agglomerates in the active layer is within the range of 150 to 2000 microns. 9. A patent claim characterized in that the active layer is divided into at least two sections, and a current collector is disposed in the middle of each adjacent section and in the middle of the support sheet and the section adjacent to the support sheet. The electrode according to any one of the ranges 3 to 8.