DE2262935A1 - ELECTRODE - Google Patents

Description

December 20, 1972 • Gzy / Ra.

Union Carbide Corporation, New York, N.Y. 1001? / UNITED STATES

electrode

The invention relates to continuous manganese dioxide containing Electrodes, a process for their manufacture and electrochemistry see devices in which these electrodes are used.

Particulate manganese dioxide mixed with powdered charcoal and / or graphite is widely used as a cathodic material or as a depolarizer, commercially available; Batteries used. It is relatively cheap and provides satisfactory energy. However, experience has shown that in the manufacture of such batteries, the cathodic mixtures containing marigandioxide cannot be compressed into molded bodies that have sufficient strength to be self-supporting, if they are wetted by the electrolyte. Therefore r.an provided electrodes containing manganese dioxide with a kind of mechanical support if such electrodes are to be used in contact with a liquid aqueous electrolyte. Such mechanical supports include metal containers surrounding annular electrodes and the compression of a stack of flat electrodes. Without such a carrier, electrodes containing manganese dioxide disintegrate fairly quickly in liquid electrolytes, especially in alkaline solutions. Decomposition also takes place over time if a good binding agent is used for the cathode, for example Portland cement, as described in US Pat. No. 2,962,540 . Electrodes containing cement also require a mechanical mechanism

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e.g. a steel container surrounding the cathode. The decay the cathode presents difficulties especially when the electrode is used in a rechargeable cell that is alternately charged and discharged. The expansion of the grid when discharging and the contraction when charging, Charges, which occur especially with manganese dioxide, also contribute to the decay of the electrode.

Since electrodes containing manganese dioxide come into contact with the Electrolytes do not have the required strength and cohesion So far it has not been possible to use manganese dioxide as a depolarizer in the form of a thin layer, though this form is the most effective for the active utilization of the electrochemical material. Because of these disadvantages, manganese dioxide became Usually used as a depolarizer only in those electrochemical cells that have low and medium discharge currents supplied, notwithstanding the fact established by experiments, that manganese dioxide had a high current-supplying power Has capacity.

The main aim of the invention are electrodes containing manganese dioxide with improved cohesion, in particular with Contact with aqueous electrolytes. Another object of the invention is contiguous thin manganese dioxide containing Electrodes. Another object of the invention are electrodes containing manganese dioxide which have a high discharge rate. Yet another object of the invention is a more efficient electrochemical one Exploitation of manganese dioxide in electrochemical cells. Another object of the invention are electrochemical cells, which have an improved resistance to changes in temperature. Another object of the invention are electrochemical cells

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BATH ORIGINAL

wit improved behavior at low temperatures. lv ^T och an object of the invention manganese dioxide containing electrode having improved when alternating charging and discharging characteristics are maintained.

The invention relates to a coherent electrode for use in electrochemical cells which contain an aqueous electrolyte. The electrode contains particulate manganese dioxide, colloidal electrically conductive material and particulate electrically conductive material. These substances are connected by a binding agent consisting of a polymer which can be wetted by the electrolyte. The colloidal electrically conductive material ensures electrical contact with a particle within the electrode . the other. J) he electrode is characterized by its resistance to swelling in aqueous electrolytes.

The principles of the invention are detailed below explained with reference to the figures; These figures show:

Fig. 1 is a perspective view of a flat manganese dioxide containing electrode according to the invention.

Fig. 2 shows in perspective in a disassembled state the components of a cell according to the invention.

FIG. 3 shows in section a cell according to FIG. 2.

FIG. H shows another cell according to the invention in the disassembled state.

^309850/0785 BAD ORDINAL

Fig. 5 shows the ratio of the discharge velocity depending on the utilization of the manganese dioxide and the total capacitance in a inventiveness geraäßen Zn / KOH / MnO "graphically shows cell according to the invention compared with a Zn / K0H / _o Mn0 cell of the known Art.

6 shows graphically the dependence of the discharge time of the tension for freshly made according to the invention Zn / KOü / MnOg cells of flat shape and such cells after one month of storage at about 50 C, in comparison with the behavior of common Zn / KOJU / MnOg cells.

Fig. 7 is a graph showing the dependence of the discharge time of the voltage in the present invention and conventional Zn / KOH / MnOg cells flat shape at Haumtemperatür, at ⁰ C and -12 ⁰ C.

Fig. 8 graphically shows the behavior of a rechargeable, flat, inventive Cd / KOH / MnOg cell when alternating Charging and discharging.

9 and 10 graphically show the behavior of chargeable, flat Zn / KOH / MnOg cells according to the invention when alternating Charging and discharging.

11 shows graphically the dependence of the discharge time on the voltage in the case of the invention.
in various stroiodiclites.

the voltage in Zn / KOli / MnO “cells according to the invention

BAD ORIGfNAL 309850/0785

FIGS. 12 and 13 graphically show the dependence of the discharge times of the voltage in the present invention, wet MgZMgBr ZMnO _{0 0 0} -Ze11en and PbZu SO.ZMn0 ~ _o cells.

Fig. Lh the behavior of a erfindungsgsmäßen ZnZKOIlZMnO graphically shows ₀ -ZeIIe when pulsating removing high currents.

15 shows a perspective view of one according to the invention. Cell unit, the electrodes being connected in parallel.

Fig, 16 shows in perspective a battery case, the eight Cell units according to FIG. 15 are connected in line target.

FIG. 17 graphically shows the dependence of the discharge time on the voltage in a cell unit according to FIG. 15 and in a standard lead-acid cell.

Fig. 18 graphically shows the behavior of a cell unit according to 15 when a strong current is pulsed,

19 shows an idealized cross section on an enlarged scale part of a manganese dioxide-containing electrode according to the invention.

Fig. 1 shows a flat manganese dioxide according to the invention containing electrode 21 with an embedded, as a current collector serving metal mesh 22. The method of! production • Such an electrode is described in detail below will. Figures 2 and 3 show a flat cell with a

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Manganese dioxide-containing electrode 21 according to FIG. 1. The cell contains an electrode 21 between two zinc grids 23 and 2k _f , the electrode 21 and the grids 23 and 2k being separated from one another by separators 25 and 26, for example made of regenerated cellulose reinforced with fibers. A suitable electrolyte is absorbed in separators 25 and 26. The cell is located in a housing 27 made of a suitable plastic such as polystyrene. When charged, the manganese dioxide-containing electrode 21 is the cathode and the grid 23 and 24 are the anodes.

A flat anode and a flat cathode by separators are separated from each other and are housed in a housing made of plastic, as shown in FIGS. 2 and 3, can be used are used for the production of flat cells, which consist of at least two flat, manganese dioxide containing electrodes and consist of at least two flat metallic electrodes, the electrodes usually connected in parallel with one another are.

FIG. K shows a type of round cell with an electrode according to the invention containing manganese dioxide. When charged, the cell contains a rolled up, manganese dioxide-containing cathode 28, which is attached to a current collector 29 made of a wire mesh, and an anode 3i made of zinc foil, the two electrodes being separated from one another by a suitable separator, e.g. one or two Modified acrylic fiber layers 32 and 33. The rolled up electrodes are arranged in a cylindrical steel container 3 **. Of the

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Electrolyte is absorbed in the sheaths32 and 33,

Fig. 15 shows a cell unit made up of several alternating ones flat, manganese dioxide containing cathodes and anodes made of pressed stone powdered zinc, with the electrodes parallel are connected to each other and separated from each other by separators. The cell unit is located in a housing 35 Plastic, the cathodic current collector 36, the anodisehe Current collector 37 and an opening 38 for pulling over that The upper part of the housing 35 extend outwards.

Fig. L6 shows a housing 39 for a battery, the eight cell units according to Fig. 15? connected in series target. Each of these cell units is located in a compartment which is formed by the partition walls M.

19 shows a cross-section through on an enlarged scale an electrode according to the invention containing mangandioxyclic. Particle 42 of manganese dioxide and parts 43 of acetylene black as particulate electrically conductive material are embedded in a porous matrix · 44 of a polymeric binder. That polymeric binder 44 contains to produce the conductivity colloidal graphite. The mixture of the binder and the colloidal graphite fulfills two tasks. First, it's supposed to be mechanical the particles 42 of manganese dioxide and the particles 43 of acetylene black join together so that the electrode at Contact with an aqueous electrolyte does not swell. Secondly this is intended to create electrical contact between the individual Particles within the electrode can be guaranteed.

BATH ORIGINAL 309850/0785

The electrodes according to the invention, containing manganese dioxide, can be prepared so that a polymeric binder, a colloidal electrically conductive material, particulate Manganese dioxide and a particulate electrically conductive material mixes and then forms this mixture into a coherent electrode.

For example, can proceed such that two grams of an epoxy resin, diglycidyl ether of bisphenol A, together with one serving as liärter amine in lh g of a suspension of colloidal graphite in an alcohol, eg IsopropylalJkohol be solved. A mixture of 90% by weight of particulate manganese dioxide and 10% by weight of a particulate electrically conductive material, for example 8% graphite powder and 2 % acetylene black, is then mixed with the mixture of the epoxy resin and the colloidal graphite in a ratio of 30 g of the Manganese dioxide-containing mixture, mixed to 12 g of the mixture of the epoxy resin and the colloidal graphite. The mixture had a putty-like consistency so that it could easily be spread on a metal grid serving as a current collector. If desired, pressure can be applied to more evenly fill the holes in the grid and to ensure good contact between the mixture and the current collector. The mixture is then heated on the grid serving as a support for about 1/2 hour at about 50 ° C. in order to drive off the liquid contained in the mixture and to cure the epoxy resin. The connected electrode can then be built into an electrochemical cell in the usual way.

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The polymeric binder according to the invention should be used in the finished product Electrode make it possible for the electrode to be wetted by the electrolyte used in the cell, but should at the same time be such that the electrode does not swell when it comes into contact with the electrolyte, to avoid the weakness of the usual manganese dioxide containing electrodes »The term" wetting "means such a design of the surface, that the electrolyte can penetrate into the pores of the electrode in order to achieve maximum ionic contact between the electrolyte and the active material in the electrode.

Besides the already mentioned epoxy resins, the polymeric binder can be made of other polymers, "B z _B from Gopolymeren of acrylonitrile, butadiene and styrene, from polymeric acrylates such Polymetliylmethacrylat .anderen or polymers of lower alkyl esters of acrylic acid or methacrylic acid where the alkyl radicals ₉

For example, contain 1 to h carbon atoms, from melamine-formaldehyde resin, from urea-foraldehyde resin, from chlorinated polyethers with recurring structural units of the formula

CH ₀ Cl

t *

-0-CH ₀ -C-CH ₀ -CH ₂ Cl

from polycarbonates, from Phe.nol <~ formaldehyde resins, - polysulfones », from polystyrenes, from copolymers ^ of styrene with monomers such as acrylonitrile, from vinyl resins »such as polyvinyl chloride from polyvinyl alcohol, from copolymers of vinyl chloride and vinyl acetate ;, from Copolymers of styrene and butadiene »

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The polymeric binder can contain the usual additives, such as stabilizers and plasticizers, which are inert to the other substances in the electrochemical cell.

The respective binders should be resistant to the electrolytes contained in the cell, for example Polyvinyl alcohol, copolymers of acrylonitrile, butadiene and styrene, urea-formaldehyde-iiarze, and phenol-formaldehyde-iiarze Do not use in alkaline cells as they are not resistant to the alkali for a long period of time are. The resistance of the polymeric binder to the electrolyte is either known or can easily be determined by Attempts to be determined. To the opposite of an alkaline Electrolyte resistant binders include polysulfones, acrylic polyincre such as polymethyl methacrylate, epoxy resins, and polystyrene .

When preparing the mixture for the electrode, it is advisable to to use the polymeric binder in a liquid carrier to ensure uniform and intimate mixing of the ingredients to facilitate. So it is desirable to use the binder in the form of a solution because most of these polymers are solid substances. Even when using epoxy resins, which are liquid before curing, it is preferable to use a solution because most epoxy resins are at room temperature are quite viscous. A solution of an epoxy resin can produce a uniform mixture more easily than the undiluted viscous one Resin. Another possibility is to use the polymeric binder in the form of a powder, if desired can be dispersed in a liquid.

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- ii

The kind of liquid used as a solvent or a dispersant for the polymeric binder depends to a certain extent Dimensions depend on the type of polymeric binder. The liquid should not just be a solvent or a dispersant for the polymeric binder, but should also be inert to the other components of the electrode. For example, the liquid should not be oxidized by the manganese dioxide contained in the mixture. To such Usable liquids include organic liquids such as isopropyl alcohol, t-buty! alcohol, liexy! alcohol, and others Alcohols. Other liquids that can be used are ketones such as acetone, methyl ethyl kelon and methyl isobutyl ketone. Chlorinated Hydrocarbons such as methylene dichloride, chloroform, trichlorethylene, Perchlorethylene and other solvents such as tetrahydrofuran can also be used according to the invention. In some In some cases it is advisable to use a mixture of liquids. The liquid must be volatile. The term "fleeting" means here that the liquid is practically completely evaporable at moderate temperatures, e.g. at temperatures up to 100 ° C.

Another component used in the method iiidungsgemäßen erf is the colloidal electrically conductive material _β Such materials include graphite, carbon black and powdered metals such as silver and nickel. The colloidal electrically conductive material is preferably η j form of a colloidal dispersion used in a liquid ,, is well known that the individual particles of colloidal electrically conductive material diameter of less than i micron _β as the liquid for the colloidal dispersants ■ yaw electrically conductive material can

BATH ORIGINAL

309850/0785

Above mentioned liquids are used as solvents or dispersants serve for the polymeric binder. Colloidal graphite is the preferred colloidal electrically conductive material. It is preferred as a colloidal dispersion in a chlorinated hydrocarbon such as trichlorethylene or used in an alcohol such as isopropyl alcohol.

The third essential component of the electrodes according to the invention is the particulate manganese dioxide. The usual Forms of manganese dioxide are used, e.g. natural ores such as pyrolusite, chemically treated natural ores, electrolytically manufactured manganese dioxide and chemically manufactured manganese dioxide.

Particulate electrically conductive material is also used in the electrodes containing manganese dioxide. Here can use the usual depolarizing agents contained in manganese dioxide Mixtures of substances used are needed. These include acetylene black and powdered graphite,

In the electrodes according to the invention, this is the manganese dioxide electrochemically active material. The polymeric binder gives the electrode cohesion and strength and allows wetting of the electrode by the electrolyte. The particulate Electrically conductive material serves the same purpose as the acetylene black or the powdered graphite in the well-known, manganese dioxide containing depolarizer mixtures. This purpose is to improve the electrical conductivity of the electrode. The colloidal electrically conductive material is used to eliminate difficulties associated with the use of a polymeric binder

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disfigured by means of the electrode. The binder tends to separate the individual particles of the manganese dioxide Hnci of the particulate electrically conductive material to be coated. Since the polymers used as binders do not conduct electricity, so, in the absence of the colloidal electrically conductive material, the binder would form an insulating layer around the manganese dioxide and particulate individual particles Form electrically conductive material. This tendency is overcome by the colloidal material and an electric one Contact between the individual particles within the electrode is ensured. In other words, it means that the colloidal Material mixed with the polymer makes the binder conductive.

The colloidal electrically conductive material, the polymeric binder and the particulate electrically conductive material are used in so small amounts that just the above-mentioned effects are achieved. It is desirable that the electrode contains as much of the manganese dioxide as possible to achieve a maximum capacity in ampere-hours per unit weight of the cell.

The minimum amount of the electrode should be about 1 to 2% by weight of the colloidal electrically conductive material, about 5 to 10% by weight of the particulate electrically conductive material, about 1 to Contain 2 wt .- $ of the polymeric binder, the order consists of manganese dioxide. These amounts are based on the weight of the finished electrode without the current collector. How one sees, the electrode can be at least 85 or 90 wt .- ^ manganese dioxide contain, usually at least about 70% by weight. the conventional electrode mixtures contain a maximum of about 70 to 80 wt .- # manganese dioxide. '

309850/0785

The above-mentioned ingredients are used in the manufacture of connected electrodes containing manganese dioxide. The components are first mixed intimately. Preferred- It is wise to mix the polymeric binder with the colloidal oil first electrically conductive material, and then releases the other components added. This creates an optimal electrically conductive contact between the colloidal electrically conductive material and the particles of manganese dioxide and the particulate electrically conductive material secured, the mixing needs to be carried out only for a short time.

The type of mixing used during manufacture is not critical. In in most cases, a simple stir is sufficient to mix the ingredients evenly.

An electrode is then formed from the mixture. In most In some cases it is advisable to shape the electrode so that the mixture is placed on a metal grid serving as a current collector or coal is applied, usually in the form of a proportionate thick paste. The usual methods can be used here. In a preferred embodiment of the invention the electrode is made by layering it on top of each other of two grids or fabrics serving as pantographs with the mixture between them. This will avoid difficulties which occur when gas is evolved when the cell is overcharged. In many cases it is appropriate during manufacture Use pressure to improve the contact between the mixture and the pantograph. If desired, the

Schm i erin i 11 e 1 pantograph also silver applied with a substance such as / graphite, sintered metal powder or by electroplating be coated to make electrical contact between the

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Electrode mixture and your grid serving as a current collector to enhance. The pantograph can be made of any material that is inert in the system. Steel, nickel, coal, Silver and steel coated with nickel or silver can be used to make pantographs.

After the electrode has been formed, the liquids contained in the mixture are removed. This can be done by simply air drying, although moderate warming is desirable in some cases. Moderate heating is also desirable to effect curing when the polymeric binder is a thermosetting resin such as an epoxy resin. Epoxy resins can often harden at room temperature, but hardening is accelerated considerably by heating. It may take half as long to warm up for one hour at about 40 to 5O ⁰ C.

To improve the contact between the electrical mixture and the current collector and to remove bubbles from the device For example, the electrode may be pressed prior to drying, using pressures from about 5 atmospheres to ten times and above being suitable are.

Before the liquids are completely removed from the mixture and before the hardenable resins are hardened, the inventive Electrodes can be brought into various physical forms. They can be spiraled, for example roll them up, they can be bent, or they can simply be made in the form of flat electrodes.

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One of the important features of the invention is that the connected electrodes containing manganese dioxide thin layers can be formed. For example, electrodes containing manganese dioxide can be used with the invention Make thicknesses from about 0.25 to about 1.25 mm. This fact is significant because the active in thin electrodes Material can be used effectively electrochemically, and because it allows cells with an unusually high discharge rate with relatively extensive use of the Manganese dioxide can be produced. All electrodes according to the invention, including thin ones, can be used in rechargeable cells that can withstand prolonged repeated charging and discharging.

The electrodes according to the invention are porous. They absorb about 20 to about kO wt .-?! * (Based on the weight of the electrode) of electrolytes. In most cases, the porosity is achieved by the evaporation of the liquid contained in the mixture. If no volatile liquids are used in the production of the electrical mixture, the porosity can be achieved by other measures known per se, for example by incorporating substances into the mixture which decompose at lower temperatures with the formation of gases. Ammonium carbonate is an example of such a substance.

The electrodes according to the invention, containing manganese dioxide, are built into electrochemical cells by known methods. These electrodes can be used as a cathode in conjunction with known anodes, such as zinc, magnesium, cadmium, aluminum, and lead. Either alkaline

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or acidic aqueous electrolytes are used what on the kind of cell, and in some cases of the kind the anode depends.

In the examples below, method i was used, if not otherwise said.

Procedure 1
Pantograph

A 0.125 dm thick grid of tempered nickel plated Steel is used as a pantograph. It is used to improve the adhesion of the electrical mixture to the grid expedient to use an adhesive. The adhesive contains conductive material such as colloidal graphite and a polymer which is softened by the solvent in the electrode mixture. The following compositions can be used as Adhesives can be used in such electrodic mixtures containing either polymethyl methacrylate or a "polysulfone";

Adhesive 1:

5 grams of polymethyl methacrylate
100 ml solvent (trichlorethylene, chloroform

Dichloromethane or mixtures of these substances) 300 grams of a suspension of colloidal graphite, which consists of 10 wt ..- ^ graphite in trichlorethylene.

Adhesive 2:

10 grams of Polj ^ sulfon
100 ml dichloromethane,
300 grams of a suspension of colloidal graphite.

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The colloidal graphite used in these examples is, unless otherwise stated, a commercial product, under the designation "DAG No. 155" from the Acheson Colloids Division of Acheson Industries, Inc., Port Huron, Michigan, is distributed.

Instructor to use a lubricant to maintain adhesion to the Enhancing the grid can be done by plating the nickel-plated grid with silver prior to applying the adhesive Behavior of the electrode can be improved at high current consumption. Only a very thin plating of silver is required.

Mixture containing manganese dioxide

Electrolytically produced manganese dioxide is used. Graphite powder with part diameters below 0.075 is now used as a partially electrically conductive material. This fabric is commercially available under the designation "Dixon Air-Spun Graphite, Type 200-09" and is sold by the Joseph Dixon Crucible Company of Jersey City, New Jersey. In some cases, fibers made from modified acrylic compounds or from carbon are added to improve the cohesion of the electrical mixture. If the electrode mixture is to have better conductivity and / or to absorb hydrogen, Ag ₂ O is added. The following composition can be used:

1000 gioiiiin electrolytically produced manganese dioxide 100 grams of graphite powder,
20 grams of fibers made from modified acrylic compounds

with lengths of approx. 3 mm (optional) 10 grams Ag ₀ O (optional)

309850/0785 bad original

Composition of the binder

The polymeric binders used had the following compositions:

Composition with polysulfone:

10 grams of a 10 wt% solution of polysulfone in diclilorinethane and / or triclilorethylene

10 grams of a 10-percent _e - $ suspension of colloidal graphite in trichlorethylene.

This composition is preferably just before use manufactured.

Composition with polymethyl methacrylate:

10 grams of a 5% by weight solution of polymethyl methacrylate in chloroform ₉ dichlorinethane and / or trichlorethylene

10 grams of a 10 ~ wt% suspension of colloidal Graphite in trichlorethylene.

This composition should be just before use, for example within half an hour before use.

Electrodic mixture

The following compositions are typical of those in US Pat Examples of the electrical mixture used

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Mixture containing polysulfone:

30 grams of the composition with manganese dioxide. 18 grams of the composition with polysulfone

Mixture containing polymethyl methacrylate:

30 grams of the composition with manganese dioxide. 18 grams of the composition with polymethyl methacrylate

After spreading the mixture on the grid provided with the adhesive, the electrode is placed between two plates, a layer of absorbent paper being placed between the electrode and the plates. The electrode is pressed for one minute at a pressure of 350 at, and then the pressure is increased to 700 at for one minute. The electrode is then dried in air to remove the volatile solvents. If the organic liquid consists entirely or predominantly of trichlorethylene, it is advisable to heat to 40 ° C. for about an hour to remove all of the liquid.

If the electrode is to be formed, for example, to be wound spirally so that happens after pressing and prior to drying.

The dried plates have a thickness of about 0.50 to 0.75 mm when the mixture was applied in a thickness of about 2.5 mm . The dried plates have a weight of about

0.20 to about 0.25 g / cm, einschlieülich a single serving as current collector metal grid having a weight of

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0.03 g / cm ² .

The electrode described above with a polysulfone as a binding agent contains about 80 to 85% by weight of manganese dioxide _? about 9 to 10 w & w. ~ fo Grapiiitpulver, about 2.5 to 3 wt .- $> polysulfone and about 2.5 to 3 wt .-% colloidal graphite. The electrode with polymethyl methacrylate contains about 82 to 87 percent by _e - '% manganese dioxide, about 9 to 10 wt .-% of graphite powder, about 1.2 to 1.5 wt .- # polymethyl methacrylate and about 2 to 3 wt .-% colloidal graphite .

Procedure 2

This other method can be applied to ms according to the invention To make coherent electrodes containing manganese dioxide:

1 · .Conductive polymeric binder ; 100 grams of a NG-wt. ~ ..- follow solution of polysulfone in a mixture of 60 ^c / o trichlorethylene and 30% chloroform with 100 grams of a 10 wt .- ^ mixed suspension of colloidal graphite in trichlorethylene.

2. Conductive polymeric binder together with, graphite powder; 200 grams of graphite powder are mixed with that much trichlorethylene. mixed to form a paste. Then 200 grams of the conductive polymeric binder is added and mixed well. Place the mixture in an oven kept at -0 ° C with a good hood and dry. After drying, the mixture is removed from the oven and ground to a powder.

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3. Partially and conductively connected graphite together with Ma ng a η di ο xy d :

150 grams of the powder obtained in process step 2 are immediately with 850 grams of electrolytically produced manganese dioxide mixed. The powder and manganese dioxide must be mixed well.

k. Bonding and making the mixture sticky : Trichlorethylene is finely sprayed into the mixture obtained after process step 3 with continuous mixing until the mixture is moist. Without drying it, cathodes are then made in molds, using a pressure of about kO at, according to method j, which are similar to those according to method 1,

5. Removal of the solution : The cathodes are dried for 15 minutes at 50 ° C. in an oven with a good hood.

This method can only be used if a binder which is solid under normal conditions is used, which can be re-softened or redissolved by adding small amounts of a solvent after process step k.

example 1

According to the invention, thin electrodes can be made in which manganese dioxide can be used very effectively. This example shows the effective use of manganese dioxide in a thin electrode produced according to the invention.

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A flat cell similar to that shown in Figures 2 and 3 was made. It contained two anodes made of expanded zinc sheet with a thickness of 0.125 mm and a manganese dioxide-containing cathode which was produced according to method 1 using polymethyl methacrylate as a binder. The mixture contained no silver oxide. The cathode had a thickness of about 0.625 mm, a size of about 10 cm, and contained about 2.0 g of the cathodic device with 80% by weight of manganese dioxide. A 9 normal aqueous solution of KOIl was used as the electrolyte. These and various other similar composite cells with initial closed voltages of about 1.4 volts were discharged at different speeds, had fallen to the voltage on I ₅ O volts.

The discharge times of these cells were plotted against the cell voltage at various current densities with a constant discharge, and based on the milliamperes per gram of manganese dioxide, as FIG. 11 shows. For example, a thin, manganese dioxide-containing cathode which 1.6 g of manganese dioxide, 80% results in a mixture of 2 g containing, while 2J2 hours a constant ^'y

/ Current of 0.1 amps (62.5 mA per g of manganese dioxide) to a separation voltage of 1.0 volts, which corresponds to ₅ O 22 ampere-hours (see the curve for 100 mA in FIG. 11) "Theoretically this should electrode 0.496 ampere-hours provide "(0.496 χ 0.31 = 1.6, assuming that is converted in the reaction in the cell, the MnO ₀ when unloading in Mn O ,, _{0 s} and that this reaction is completed, wherein 1 g of manganese dioxide supplies about 0.31 ampere-hours.) The utilization of the manganese dioxide in this electrode up to a separation voltage of 1.0 volt is about 45 % of theory.

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Figure 5 compares the mean behavior of thin manganese dioxide-containing cathodes according to the invention in flat cells of the type described above with the behavior of commercial size D alkaline round cells containing manganese dioxide. Each of these latter cells contained 35 g of manganese dioxide in the cathodic mixture inside the steel container. The current decrease in cells which had this type of cathode containing manganese dioxide, with a current supply of 62.5 mA per g of manganese dioxide, would reach 2.2 amperes (35 x 0.0625). In experiments it was found that 1.5 ampere-hours were obtained from such cells with a constant current decrease of 2.2 ampere for 0.7 hours. The theoretical value would be 35 x 0.3t = 10.85 ampere-hours. The mean utilization of the manganese dioxide in the diesel "cell is thus 1h fo. In this comparative experiment, a separation voltage of 0.7 volts at 2.2 amperes was used in the usual cell, since the voltage drop is higher than in the internal resistance due to the internal resistance The thin cathode according to the invention used a separation voltage of 1.0 V. Fig. 5 also shows that at higher discharge rates, the mean utilization of manganese dioxide in conventional cells decreased rapidly compared with that in ei ~ thin electrodes according to the invention.

This example shows the extraordinarily high utilization of the electrochemical energy of manganese dioxide, which can be found in thin electrodes according to the invention. In thin electrodes according to the invention, containing manganese dioxide, at least 25%, in many cases at least 35 %, of the electrochemistry.

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Electrode made of zinc using a 9 nm aqueous solution of KOH as the electrolyte, before the voltage drops below about 0.9 volts. The electrochemical energy of the manganese dioxide is the theoretical amount of electricity, expressed in ampere-hours ₉ , which could be achieved with the complete conversion of MnO ₀ to Mn ₀ C ₇ , "when discharging the cell"

Example 2

The electrodes according to the invention are relatively stable even at high and low temperatures ,, This example describes these advantages. There were flat cells with alternating arranged flat anodes and cathodes according to Figures 2 and 5 used 5 which were connected in parallel «each of the flat Cells contained three thin, flat ones containing manganese dioxide Cathodes made by Method 1 described above was. Each cathode contained 2 grams of the cathodic mixture (about 1.6 grams of manganese dioxide) and each had an area

ο
of about 10 cm. The four anodes consisted of "zinc, - a 9-molar aqueous solution from KOJI was used as the electrolyte. The separators consisted of regenerated cellulose reinforced by pasers»

After storage at a higher temperature of about 5Q ° C and at lower temperatures of from 0 ° and -12 ⁰ C the behavior is this flat cells compared with the behavior of commercial alkaline cells of the dimensions AA _5, MnO _2, and contained zinc. The content of this comparative cells was comparable to the contents of the flat cells ₀ Each of the cells of the invention had a weight of i6 to 19 _s g while the standard cells including the Staiilbe-

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containers had a weight of 2h g each. Each of the flat cells contained 6 g of manganese dioxide, each of the commercially available cells with the dimensions AA contained about 7 g of manganese dioxide.

The flat cells according to the invention and the commercially available ones AA cells were measured at a constant current decrease of 350 mA discharged at home temperature, both immediately after the Manufacture as after one month of storage at approx. 50 ° C. The results of these tests are shown in FIG. 6, in which the voltage is plotted against time. After a month The inventions had storage at about 50 C flat cells have a considerably higher proportion of the original Maintains effectiveness than the commercially available alkaline AA cells.

The flat cells according to the invention and the commercially available AA cells were at a constant current of 220 inA discharged at room temperature, at 0 C and at -12 C »In der 7 are the voltages plotted against time. Behaviour the flat cells of the invention at low temperature is considerably better than the behavior of commercially available AA cells, although the behavior at room temperature is similar is.

B e is j x iel 3

The cells according to the invention can be used as secondary or re- rechargeable cells can be used. The following two attempts show the rechargeability of inventive Cells:

BATH ORIGINAL

309 8 50/0 7 85

A. Mn0 ₂ / K0H / Cd cell _ffl -

A flat cell with alternately arranged anodes and cathodes according to FIGS. 2 and 35 which were connected in parallel, was made from two thin, manganese dioxide-containing cathodes by Method 1. The cell contained three commercially available Cadmium anodes and a 9 molar aqueous solution of KOH as an electrolyte. Each of the cathodes weighed 2.2 grams with about 1.6 grams of manganese dioxide and were about

10 centimeters . The cells were repeatedly discharged and charged at a constant current of 0.2 amps, where the Charging began when the cell was discharged to a voltage of 0.8 volts and stopped when a voltage was reached 1.5 volts was reached «, the cathodic current density was

2
per cm at 10 JIIA, and the discharge rate was 50 mA per g of the cathodic mixture _o The Pig _o 8 shows the behavior at 100 times of discharging and recharging "Like the Spannungsdiagraamie / are reached approximately 75% of the discharge during the first 40 cycles . As the cycles continued, the discharge decreased to about 50%. . ·

The cell gave a total of 180 cycles, but after 130 cycles it decreased
/ internal resistance increased and the recharge time decreased

below the practical limits, B. MnOg / KOH / Zn cell.

A cell with a thin, manganese dioxide-containing cathode according to FIG. 1, which was produced by the method 1, with a A gelled anode made from zinc powder and an electrolyte from a 9-inolar aqueous solution of KOH was made. The cathode had a weight of 2 * g (about 1.6 g of manganese dioxide), and one

309850 / 078S

Area of about 6.5 cm. The electrodes were separated from each other through two layers of regenerated cellulose. The cell took 1 hour to discharge and recharge at a constant current of 0.1 amps.

9 shows the behavior of the cell here at 58 cycles and at a constant current density of 50 mA per g of manganese dioxide, the current intensity during charging and discharging at 0.1 amps. The cell withstood 55 cycles under the conditions described. Then the cathode only took a low one Charge and dendrites of zinc had formed.

With a lower discharge, for example 25 mA / g manganese dioxide, a considerably higher number of cycles can be achieved. FIG. 10 shows, for example, the behavior of a cell similar to that described, but which contained two thin cathodes containing manganese dioxide connected in parallel instead of one cathode. The anode was located between the cathodes as similarly shown in FIGS. The currents during charging and discharging were O ₅ I amps. A discharge of 25 mA per gram of manganese dioxide in the cathodic mixture would correspond to a current of 1.0 ampere in a D-size cell. The maximum recommended discharge current for a typical commercially available rechargeable D-cell with MnO ₂ / KüM / Zn is 0.625 amperes. This comparison shows the good behavior of the cells according to the invention.

The example also shows that a long life when charging and discharging cells with the invention Electrodes can be reached. As a rule, rechargeable cells can be made with electrodes containing manganese dioxide.

309850/0786

the invention measured at least 150 charges and discharges
withstand if they are discharged up to 30% with a constant current decrease of 100 inA / g maxigand dioxide before the
Cathode fails. The failure of the cathode is shown by a poor absorption of current, by an increase in the static energy and the ions. /

example k

Flat rolled up (liuciienrolle) alkaline MnOp-Zn cells

A primary alkaline zinc round size cell C _9, the illustrated corresponds to the _s. H in Fig was a using
Zinc sheet as an anode, modified acrylic fibers as a separator and a binder containing as polymethyl methacrylate and as an active material of manganese dioxide cathode prepared The mixture was applied to a grid according to the method 1 ₉ ~ ge

(Cake roll)
squeezes into a spiral / rolled up and into a container

Brought steel. An aqueous 9-normal was used as the electrolyte
Solution of koii with 1 & ew _a -% ZnO used cathodic The mixture contained 2 percent "- $> the binder" The cathode had
a length of about 20 cm, "a width of about 3 _S 2 cm and a thickness of about 0.5 mm" The dimensions of the anode were similar.

In comparison with a commercially available alkaline D-cell, the smaller C ° = line according to the invention showed better behavior in that it had a constant current of h amperes during, for example
1 hour gave ₃ when the standard cell at the same current load SOLION after 10 minutes failed _o In both cases was the original voltage 1 ₉ 5 volts and 0.8 volts -Abtrennspannung.

_ 30 -

A cell of this type with a rolled-up cathode containing manganese dioxide and an anode made of zinc is comparable to a nickel-cadmium cell with regard to the output of stroia
a rolled up cathode made of sintered nickel oxide. The cell with the manganese dioxide surpasses the nickel-cadmium cell
with regard to the original capacity and behaves considerably better after storage at elevated temperatures.

These and other examples show the high discharge capacity that characterizes cells with thin,
Have manganese dioxide containing electrodes. The thin electrodes according to the invention can be discharged above about 0.9 volts at a constant current of at least 250 niA per g
Manganese dioxide against a comparison electrode made of zinc using a 9 normal aqueous solution of KOH as the electrolyte. At this high discharge, the thin, manganese dioxide can come out
containing electrode of the invention is at least about 15 inches
in some cases at least about 20 % of the electrochemical energy of the manganese dioxide in the electrode can be utilized.

iel "5

Mg / MgBr ₀ /> iii0 ₀ cell (90 fo MnO ₀ in a mixture)

wet

A / Mg / MgBr ₉ / MiiO ₉ cell was made using

a plate made of magnesium as anode, a normal aqueous solution of MgBr ₀ as electrolyte, and two thin cathodes containing manganese dioxide of the type shown in FIG. 1, for the production of which a composition containing silver oxide was used according to method i . The only difference was that 60 g of graphite powder was used instead of 100 g. Polymethyl methacrylate served as the binder. That

309850/0786

■ _ 31'-

· Behavior during discharge when removing a continuous stream of 0.5 amps is shown in FIG _e - illustrated 12- »-.

Example 6

A cell of the invention with 20 wt _o =% aqueous sulfuric acid as an electrolyte, an anode of lead of a conventional battery, and with two thin, manganese dioxide, as described in Example 5 containing cathode of FIG. 1 of the same composition, was prepared , with the exception that a polysulfone was used as the binding agent,

The behavior at a constant current decrease of 0.6 amperes is shown in Fig. 13 »

Example 7

Behavior at high current consumption

The behavior of thin, en binder and manganese dioxide containing cathodes at exceptionally high current taps was examined in a box-shaped cell of Figure 15 at a _o Strömabnahme of k ampere-hours in pulsing experiments that corresponded to the indexing movement of a machine.

The cell contained six thin cathodes containing manganese dioxide and seven gelled anodes containing zinc powder connected in parallel. Each electrode was about 5 cm long, about 5 * 7 cm wide, and about 0.5 to 0.6 mm thick. The six cathodes were prepared by the method 1, contained a total of 21 g of manganese dioxide, together with 9 g of conductive material and binding agent (2 wt _o - $

Polysulfone). The seven anodes contained a total of 20 grams of zinc powder and 10 g of a starch-gelled electrolyte of 9-normal KOH applied to tin-plated copper grids as current collectors were pressed on. In addition, 20 g of a 9-normal aqueous solution of KOH were used in each cell. Modacrylic fiber separators were adjacent to the cathodes and fibrous cellulose was adjacent the zinc anodes.

A suitable container has a weight of 20 g. The total weight the cell unit is 100 g (1/9 of a battery of 9 cells with 12 volts). The capacity of the cell unit is nominally at 5 watt-hours, which is about! 55 watt-hours / kg at 3 hours of discharging down to a separation voltage of 0.9 volts is equivalent to.

14 shows the discharge at 20 amperes for 6 minutes of such a cell, which was carried out for 3 minutes in 12 pulses of 5 seconds each, with 1/6 of the total capacity being removed from the cell (a fresh cell operates at 20 amperes Continuously for 6 minutes until the voltage reaches 0.9 volts). After charging and discharging 20 times at the 12th pulse of the 20th series, the cell reached a voltage of 0.9 volts, which is shown by the dashed curves in FIG. 1h . This means excellent behavior, taking into account the fact that a standard acidic lead cell of comparable size achieves a voltage of 0.9 volts during a series of discharges with 20 amperes per pulse (20 ampere-minutes). It should also be noted that acid lead batteries can withstand high pulses in daily succession, but that the current consumption is very poor if they are stored after such an experiment.

3O98S0 / 07B5

The changes in the capacity of this cell at different Current draws can be seen from the following:

6 hours
4 amp hours 3 amp hours 1.5 amp hours

3 hours

4 amp hours 2 amp hours 1 amp hour 0.5 amp hours

1 hour

4 amp hours

6 minutes

2 amp hours

(Discharge with a current of 0.7 A)

40 - 60 cycles 80 - 100 cycles 200 cycles

(Discharge with a current of 1.33 A)

60 - 80 cycles 150 cycles
300 cycles
more than 800 cycles

(Discharge with a current of 4 A)

20-30 cycles

(Discharge with a current of 20 A)

12-15 cycles

Example 8

Cathodes containing manganese dioxide produced according to the invention showed that they had retained 90% of their current absorption capacity after 6 months of storage at 45 ° C. in 9 normal aqueous solution of KOH *

Alkaline batteries according to FIG. 16 with manganese dioxide and Zixik _s, where the electrodes were according to the invention, also showed a noticeably better capacity in the first cycles during continuous discharge compared with commercially available lead acid batteries of the same nominal voltage and design. With a constant current decrease with a resistance of

3098S0 / 078S

The batteries containing aclitic alkaline MnO _{2 worked for} 4 to 6 minutes until a separation voltage of 0.9 volts per cell unit was reached, compared with 45 seconds to 1 minute for corresponding acidic lead batteries with 12 volts. The alkaline cell units were constructed as shown in FIG. They contained eight compartments in a battery according to Fig. 16, each having the dimensions of 8.4 5.5 x If05 cm. Each cell unit contained six thin cathodes containing manganese dioxide and five anodes made of expanded zinc grains. The cathodes, which were 0.5 mm thick, contained the following components:

% By weight of the finished component parts electrodes

35.8 g of electrolytically produced manganese dioxide 82

3.6 g graphite powder 8.2

0.72 g fibers (modacrylic or

Graphite) 1.6

1.8 g polystyrene 4.1

1.8 g colloidal graphite 4.1

Tetrahydrofuran was used as the solvent for the polystyrene used. The cathodic current collectors were made of silver plated Stole. The anodic pantographs were made of tin-plated steel. The electrolyte used was a 9 — normal aqueous solution of KOH with 1% by weight of ZnO is used. "Perinion'-ί separator, manufactured by Radiation Application, Inc. of Long Island City, New York were used. The "Permiorf-Scheider are commercially available membranes made of grafted cellulose. That through radiation Aif-grafted monomer can be, for example, a methacrylate.

309850/0785

_ 35 - '

17 shows the behavior of cell units according to FIg ₀ 15 with regard to the voltage when the current is decreased with a resistance of 0.6 ohm from a battery of 8 cells, compared with the behavior of a cell unit from a commercially available acidic lead battery with 6 Cells »The cell unit according to the invention with manganese dioxide and tin had a slightly lower voltage, but could be operated much longer than with the same current consumption of an acidic lead cell. Under these conditions, 20 cycles could be carried out with the cells according to the invention ₉ compared with only a few cycles, for example five, under the same conditions with acidic lead cells.

The same cells according to FIG. 15 _f, ^{which have} just been described, were also tested in a pulsating manner with pulses of 25 amperes of 0.5 seconds each once per minute. The behavior during the discharge of various typical cells is shown in FIG. This shows that up to four recharges of 350 pulses can be achieved at a cut-off voltage of 0.9 volts.

Example 9

In order to determine the influence of a liquid aqueous electrolyte on electrodes with binders, the following experiment was carried out. . Several slices ^ the 78 wt ~% manganese dioxide, 6 wt .-% Portland cement as a binder and l6 wt .- $ carbon powders contained ^ were prepared "Other wheels contained 80 weight" - $ manganese dioxide, 2 wt _o ~ $ Poly »methylinethacrylat as a binder and 18 wt ₀ - fo colloidal and non-colloidal conductive material "These latter

309 8 5 0/0785

Disks were made according to Method 1. Pattern of
each type of these disks were in
immersed in a 9 normal aqueous solution of KOH. After this time, the disks with Portland cement had started to crumble, while the disks according to the invention with the polymer as binder showed no sign of disintegration.

309850/0786

Claims (22)

- 37 - ■ · - ,,. 'Claims 1. Coherent electrode for an electrochemical pre- , direction containing an aqueous electrolyte, characterized in that it (a) particulate manganese dioxide, (b) colloidal electrically conductive material, the particles of which are in electrical contact with one another, (c) particulate f A shaped electrically conductive material and (d) one which can be wetted by the aqueous electrolyte but is in contact contains polymeric binder which does not swell with it. Electrode according to Claim 1, characterized in that it is a copolymer of acrylonitrile, butadiene _v and styrene, an epoxy resin, a polymer of a lower alkyl ester of acrylic acid or methacrylic acid _{as the binder.} a melamine-formaldehyde resin, a urea-formaldehyde resin, a chlorinated polyether, a polycarbonate, a phenol-formaldehyde resin, a polysulfone, a polystyrene, a copolymer of styrene and acrylonitrile, a polyvinyl chloride, a copolymer of vinyl chloride and vinyl acetate , a polyvinyl alcohol, a copolymer of styrene and butadiene, or two or more of these substances. 3. Electrode according to claim 1 or 2, characterized in that that it contains graphite, carbon or a powdered metal as a colloidal electrically conductive material. 4. Electrode according to one of claims 1 to 3, characterized in that that it contains graphite or carbon as a particulate electrically conductive material. BAD ORIGINAL 309 850/0785 5. An electrode according to any one of claims 1 to 4, characterized in that it comprises at least 1 wt% ~ of the colloidal electrically conductive material, at least 5 parts by weight 5 "of the particulate electrically conductive material, at least 1 percent - of the ^c / o.. Binder and at least 70% by weight of manganese dioxide. 6. Electrode according to one of claims 1 to 5, characterized in that that it has a thickness of about 0.25 to about 1.25 µm. 7. Electrode according to one of claims 1 to 6, characterized in that at a constant discharge current of 100 milliamps per gram of manganese dioxide against a comparison electrode made of zinc when using a 9-normal aqueous solution of potassium hydroxide as the electrolyte, at least 25 % of the electrochemical energy of the Manganese dioxide exploits before the voltage drops below about 0.9 volts. 8. Electrode according to claim 7 »characterized in that it uses at least 35 " / »of the electrochemical energy of the manganese dioxide. 9. Electrode according to one of claims 1 to 8, characterized in that it withstands at least 150 successive charges and discharges if the discharges are carried out at a discharge current of 100 milliamps per gram of manganese dioxide up to 30 % of the full discharge, BATH ORIGINAL 309850/0785 10. Electrode according to one of claims 1 Ms 9s, characterized in that at a constant discharge current of 250 milliamperes per gram of manganese dioxide against a comparison electrode made of zinc when using a 9 normal aqueous solution of potassium hydroxide as the electrolyte, at least 15 % of the electrochemical energy . of manganese dioxide exploits before the voltage falls below about 0 _? 9 volts sinks " Ho Electrochemical device with an anode, a cathode and an aqueous electrolyte in contact with the anode and the cathode, characterized in that the cathode in the charged state is an electrode according to one of Claims 1 to 10. 12. Electrochemical device according to claim II _5, characterized in that the anode consists of zinc, cadmium, lead, aluminum or magnesium. 13. Electrochemical device according to claim 11 or 12, characterized characterized in that the anode consists of zinc or cadmium and the electrolyte is an aqueous alkaline solution is. lh, Eleictrocliemische device according to claim 11 or 12, characterized in that the anode consists of lead and the electrolyte is an aqueous acidic solution « 15. Electrochemical device according to claim 11 or 12, characterized characterized in that the anode consists of magnesium and the electrolyte is an aqueous solution of magnesium bromide is. BATH 30985Q / 078S 16. Method for IIci "position of an electrode according to one of the Claims 1 Ms JO, characterized in that the Binder, the colloidal electrically conductive Matsri & l, the manganese dioxide and the particulate electrically conductive Mixes the material and forms the electrode from this mixture. 17. The method according to claim 16, characterized in that one first preparing a mixture of the binder and the colloidal electrically conductive material and this mixture the particulate electrically conductive material and the manganese dioxide are added, 18. The method according to claim 16 or 17, characterized in that that the mixture of the components with a current collector connects. 19. The method according to any one of claims J6 to 18, characterized in that that the binder in the form of a solution or Dispersion in a volatile solvent used. 20. The method according to any one of claims Io to 19, characterized in that that the graphite is used in the form of a dispersion in a volatile solvent. 21. The method according to any one of claims i6 to 20, characterized in that that the mixture of ingredients is brought to the electrode under pressure. 22. The method according to any one of claims 19 to 21, characterized in that that one from the shaped electrode, the volatile solvent by evaporation with formation removed from pores in the electrode. BATH ORIGINAL 309850/0785 Blank page