FI70490B - ELEKTRODER FOER BLYACKUMULATOR SAMT FOERFARANDE FOER FRAMSTAELLNING AV EN ELEKTROD - Google Patents

Description

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Patent ::. 31 lal at 10 00 1086 (51) Kv.lk. '/ Lnt.CI. * H 01 M k /] k FINLAND —FINLAND (21) Patent application - Patentansöknlng 780067 (22) Application date - Ansökningsdag 09.01.78 (FI) (23) Starting date - Giltighetsdag 09.01 .78 (41) Has become public - Blivit offentlig 1 6.08.78

National Board of Patents and Registration / 44) Date of publication and date of publication. - 27.03.86

Patent and registration authorities '' Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. trap (32) (33) (31) Privilege claimed - Begärd priority ^ 5.02.77, 28.03.77 USA, / 68909, 781762 Proven-Styrkt (71) Solargen Electron ies, Ltd., 562 Fifth Avenue, New York, New York 1 0036, USA (72) Rudolf Hradcovsky, Long Beach, New York,

Otto R. Kozak, Long Beach, New York, USA (US) (7 * 0 Oy Borenius & Co Ab (5 * 0 Lead-acid battery electrodes and method of electrode production -

Electrode for a battery accumulator for the purpose of the frame11

The invention relates to a lead battery electrode, a negative electrode made therefrom and a method for manufacturing the electrode. More specifically, the invention uses an active mass to make such electrodes, wherein this active mass is a mixture of crystalline and polycrystalline lead peroxide. The invention also relates to a method of manufacturing an electrode comprising an active mass.

The structure and operation of the electric cell are known per se. Such a cell, which is either a primary cell or a secondary cell, is an electrochemical device having two plates of conductive material embedded in an electrolyte. The purpose of the primary cell is to generate electrical voltage and to convert chemical energy into electrical energy in a disposable manner. The secondary cell, on the other hand, operates reversibly and can convert chemical energy into electrical energy or vice versa. Secondary cells are commonly referred to as "battery cells".

When the battery cell releases electrical power, the cell is said to "discharge", whereby the chemical energy is converted into electrical energy. While the battery cell receives electrical energy, the process is reversed and the cell is said to be "charging."

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Two or more cells connected to each other either in series or in parallel form a battery, and a battery made by connecting several battery cells together is called a battery.

There are two common types of batteries, namely a lead-acid type battery, which is simply referred to as a "lead battery", and a nickel-lye type or Edison type battery, commonly referred to as an "alkaline battery". The invention relates to the first-mentioned type of battery.

The cells of the lead-acid battery consist of a positive plate of lead oxide and a plate of a negative lead fungus immersed in a dilute sulfuric acid solution (electrolyte). The active mass or material of each plate is the part of the plate that chemically changes as electricity flows through the battery. This active mass is supported by a frame or lattice which is pure lead or a lead alloy, e.g. an alloy of lead and antimony, which has the dual function of supporting the active mass and conducting an electric current. The invention relates in particular to a new, unique and improved active mass.

The charge and discharge cycles of a typical lead-acid type battery can be described by the following reversible reaction:

Ph02 + 2H2SO4 + Pb -> 2PbSO4 + 2H2O (+) plate (-) plate

The active material of the positive plate is brown, porous lead oxide, while the active mass of the negative plate is gray, spongy and porous pure lead.

Lead-acid batteries available on the market today have limited performance, so numerous attempts and suggestions have been made in the past to improve these batteries. Thus, the improvements in the charge and discharge characteristics of these batteries, the increase in their current discharge rate, and the reduction of the internal resistance of the battery cells are some of the numerous characteristics to which considerable attention has been paid by those skilled in the art. Some have focused on electrodes, while 3,70490 others have suggested various electrolytes to improve the overall performance of cells and batteries containing them.

Accordingly, U.S. Patent No. 2,933,547 discloses a battery made of a plurality of solid state electrochemistry consisting of silver and zinc electrodes having a solid solvated cation exchange resin film interposed between these electrodes.

U.S. Patent No. 3,468,719 discloses a solid state ionic conductor made of a polycrystalline material in which a structural lattice box is formed of a combination of aluminum and oxygen ions and sodium ions that migrate relative to the lattice box by an electric field. This material is used as a semi-cell separator in the structure of batteries, as further explained in Example 3 of this patent.

U.S. Patent No. 3,499,796 discloses a ceramic deposit interposed between two electrochemically and cationically conductive crystalline components which are in cation-exchanged relationship with a cationically conductive, electronically non-conductive crystalline component therebetween, and further discloses battery devices formed from such cells.

U.S. Patent 3,709,820 discloses an organic solid electrolyte having a crystalline electron donating and accepting complex of ionic crystals of 7,7,8,8-tetracyanoquinodimethane, an aromatic amine, and a liquid impregnated in this ionic lattice box. The electrolyte described in this patent is used in capacitors to reduce their resistance.

U.S. Patent No. 3,765,915 discloses the use of a polycrystalline ceramic product of beta-alumina as an electrolyte in the construction of Atrium-sulfur type battery cells.

The aforementioned patents represent only a few of the numerous patents that describe research and practice in the art. Nevertheless, the basic structure of the lead-acid battery and its cells has remained largely unchanged. Today, as well as several decades ago, lead-acid batteries are manufactured by connecting a series of cells (usually 4,70490 3 or 6) in which the active plate is a porous lead oxide as the active mass and the negative plate is a spongy porous lead and the dilute sulfuric acid is the electrolyte.

It is an object of the present invention to provide even better battery cells and instruments made therefrom.

It is also an object of the invention to provide a battery in which the active mass of the positive electrode is a unique material made of crystalline and polycrystalline lead oxide. This polycrystalline or "polycrystalline" lead dioxide is a material in which lead is present as crystals of different degrees of growth and development of lead oxide. These batteries will hereinafter be referred to as "lead-crystal batteries" to distinguish them from previously known lead-acid batteries.

It is also an object of the invention to provide new and unique lead crystal batteries with superior performance characteristics over conventional lead batteries.

It is also an object of the invention to provide lead crystal batteries which have an even lower internal resistance and a higher potential difference (electromotive force) than previously known lead-acid batteries.

Yet another object of the invention is to provide lead-acid batteries which have an even higher current charge and discharge capacity and which can be charged in a considerably shorter time than the previously known lead-acid batteries.

It is also an object of the invention to provide lead crystal batteries which are characterized by a significantly lower sulfation compared to a lead-acid battery.

It is also an object of the invention to provide a process for the preparation of crystalline and polycrystalline lead oxide in active pulp.

It is also an object of the invention to provide a unique positive plate used to construct battery cells and batteries made from such cells.

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It is also an object of the invention to provide positive plates comprising a support plate made of e.g. lead, an alloy of lead and antimony or a non-conductive carrier material and having a conductive coating, and the surface of this support plate has crystalline and polycrystalline lead oxide.

More specific objects of the invention appear from the appended claims and are set forth in the following description with reference to the accompanying drawings, which form a part of this application.

According to the invention, a battery cell is obtained in which the active mass of the positive electrode of the cell is a mixture of crystalline and polycrystalline lead peroxide (PbO 2). First, the mixture of lead and cadmium is lowered or otherwise suitably applied as a uniform adhesive layer to a support plate made of lead, an alloy of lead and antimony, or a suitable inert, non-conductive material coated with lead or an alloy of lead and antimony. The lead-cadmium mixture can be applied to the support plate by hot spraying, applying the so-called by a "powder metallurgical" process or by electroplating, all of which are explained in more detail below.

The support plate coated with a mixture of lead and cadmium is then immersed in a tank in which the electrolyte is a dilute solution of sulfuric acid and in which a lead plate or sheet is cathode. The support plate is then connected to the positive terminal of the power source and the lead plate is connected to the negative terminal of this source. As the electric current passes through the plates, the lead in the lead-cadmium layer oxidizes to lead peroxide, which occurs as a crystalline and polycrystalline mass, while cadmium reacts with sulfuric acid to form cadmium sulfate, which settles on the lead plate as a spongy material. The support plate is then removed from the solution, rinsed clean with water and dried.

The three support plates prepared as described above are then immersed in a second container containing a dilute sulfuric acid solution. The middle support plate is connected to the positive terminal of the power supply, while the other two support plates together are connected to the negative terminal of this power supply. As an electric current passes through the combination, the middle support plate becomes positively charged, and the lead peroxide remains unchanged, while the lead oxide of the other two plates is reduced to lead and becomes negatively charged.

6 70490 The power supply is removed after a few minutes, at which point the electromotive force of the cell decreases from 2.9 volts to about 2.4 volts and remains essentially constant at this value. The cell is now charged and stores power for later release.

Three or more such cells may be combined to form a lead-acid battery according to the invention.

Figure 1 schematically illustrates a process according to the invention for the preparation of active mass, i.e. crystalline and polycrystalline lead oxide.

Figure 2 illustrates in a schematic diagram the formation of positive and negative plates and a cell having such plates.

Figure 3 shows two curves comparing the properties of a lead crystal cell made according to the invention with the properties of a conventional lead acid type cell.

It has now surprisingly been found that the performance of battery cells can be greatly improved by equipping the cells with a unique positive plate with crystalline and polycrystalline lead oxide PbOg as the active mass. Thus, lead crystal batteries made from such cells have superior performance characteristics as compared with conventional lead acid batteries.

The invention will be explained in detail below, in particular on the basis of a battery cell and a battery made of such cells.

This. however, the description does not limit the scope of the invention in any way, as there are other battery devices which can be constructed on the basis of the principles described above and which therefore fall within the scope of the present invention.

It has now been found that a battery cell constructed in accordance with the invention has properties which have hitherto not been achievable in prior art battery cells, so that devices, e.g. batteries formed by connecting such cells in series, also have superior performance over conventional lead-acid batteries. These improved properties include lower internal resistance, higher activity, 70490 7 lower sulfation, better charge and discharge properties, higher capacity, faster charge and higher electromotive force per cell. However, this list of features is by no means exhaustive.

The unique active mass produced by the process of the invention consists essentially of crystalline and polycrystalline lead oxide (PbCl 2), in which lead has a maximum electron valence 4, and which is referred to as lead peroxide to distinguish PbO, in which lead has a lower electron valence 2.

As used herein, the term "polycrystalline" means a composition of simple lead peroxide pulps in which these crystals are in varying stages of growth and development. Thus, the active pulp of the invention is a mixture of simple crystalline pulps of lead peroxide and such polycrystalline compositions.

According to an embodiment of the invention, shown in particular in Figure 1, a support plate 1, typically made of pure lead (Pb) or an alloy of lead and antimony (Pb-Ob), is coated with a layer Pb-Cd as described below and immersed in an electrolyte tank 3 dilute sulfuric acid solution. The support plate used herein is suitably a sheet about 0.2 mm thick made of an alloy of lead and antimony. However, the thickness of the support plate may vary somewhat, depending on the particular design and intended use of the battery device.

Before the support plate 1 is immersed in the sulfuric acid solution, a hot melt of lead and cadmium is sprayed onto the surface of the sheet by means of a conventional spray gun or some other suitable spray gun to form a smooth and adhesive layer of lead and cadmium on both surfaces of the sheet. A reducing gas, e.g. hydrogen, is used in the spraying of the hot melt, and the spraying is stopped when the thickness of the layer formed on each surface reaches a value of about 0.5 mm. This thickness can also vary somewhat, depending on the construction of the instrument, the desired resistance and the intended use. In general, the thickness of the Pb-Cd layer on each surface can vary within about 0.1 ...

2 mm, suitably in the range of about 0.5 to about 1.2 mm, and the most suitable thickness is about 1 mm.

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The Pb-Cd melt is prepared by electrolytically or galvanically coating a cadmium wire about 1 mm thick to a lead to cadmium weight ratio of about 1: 1, after which the formed wire is melted, sprayed onto the surface of the sheet in the next adhesive temperature melting point, but lower than the melting point of lead and antimony in the special alloy from which the support plate is made in that Pb-Cd sintered to the surface of the support plate.

In order to make the Pb-Od layer better adhere to the surface of the support plate 1, the support plate can first be sandblasted for several minutes to form a roughened surface so that the integrated Pb-Cd mixture binds better to the surface of the plate.

Figure 1 shows a container 3 made of a non-conductive material (such as glass, plastic, etc.) and containing as a electrolyte a dilute sulfuric acid solution having approximately the same specific gravity as those sulfuric acid solutions used in conventional type lead-acid batteries. This container 3 also has a lead plate 5 which acts as a negative electrode, i.e. a cathode. A support plate 1 prepared as described above is immersed in the electrolyte as shown in Figs. 1 and connected to a positive terminal of an electric source 7 having a voltage of 3 volts (e.g. a battery), while a lead plate 3 is connected to the negative terminal of this voltage source. Although a plurality of support plates can be embedded in the electrolyte and connected to an electrical source, the invention will be explained and described in connection with the manufacture of a single positive plate for the sake of clarity.

when the circuit is closed as described, the cadmium in the Pb-Cd layer of the support plate reacts with sulfuric acid to form cadmium sulfate, which settles as a porous sponge-like mass on the lead plate 5. Water decomposes into hydrogen (Hr,) and oxygen (O 2). Hydrogen appears as gas bubbles on the surface of the negative electrode, while oxygen reacts rapidly and continuously with lead to lead peroxide (PbO 2) as a crystalline and polycrystalline mass. The formation of the active mass is thus completed in a few minutes, after which the support plate is removed, rinsed clean and dried. It is now ready for use in a lead crystal cell or battery according to the invention.

The active mass of crystalline and polycrystalline lead peroxide is a dark brown ... black material. It is hard, homogeneous, 9 70490 very porous, and its internal resistance is quite low.

When producing a support plate in which the active mass is crystalline and polycrystalline lead peroxide, it is critical for the formation of this mass that the Pb-Sb plate is coated with a sintered Pb-Cd layer. Thus, care must be taken to avoid the formation of a Pb-Cd alloy when the support plate is coated by sintering or hot-spraying according to this embodiment of the invention. The presence of cadmium in the sintered pulp is also critical because it contributes to or promotes the formation of PbOg crystals and Moniki pathways. In addition, it should be noted that although cadmium reacts with the sulfuric acid in tank 3 to form cadmium sulfate and is removed from this tank, cadmium residues still remain in the active mass.

To produce a lead crystal battery according to the invention, three similar support plates 1a, 1b and 1c, prepared as described above, are immersed in the container 9 as shown in Fig. 2.

This container 9 is similar in structure to a lead-acid battery and contains a dilute sulfuric acid solution conventionally used in such batteries. The support plates 1a and 1c are connected together by a conductor 11 and connected by a conductor 13 to the negative terminal of a 3-volt power source 15 (e.g. battery or battery charger, etc.), while the support plate 1b is connected to the positive terminal 15 of this voltage source 15 by conducting the circuit. and PbOg in 1c is reduced to Pb, and the plates are negatively charged, while the PbOg in support plate 1b remains chemically unchanged and becomes positively charged.

Thus, the lead plates will act as negative electrodes, i.e. the cathode, and the lead peroxide plate will act as the positive electrode, i.e. the anode.

After a few minutes, when the cell has become fully charged, the power source 15 is removed, reducing the electromotive force of the cell from 2.9 volts to about 2.4 volts, and remaining substantially constant at this value. The cell is now charged and stores power for later release.

When a cell manufactured as described above is connected in series with other cells, e.g., 3 cells, each cell containing a plurality of plates, usually 17 or 19 connected in parallel, a lead crystal battery having 51 or 57 plates is formed, depending on the number of plates in each 10,70490 cells. . Obviously, more than 3 cells, e.g. 6 cells, etc. can be connected in series as needed.

The lead crystal batteries of this invention have superior performance compared to lead acid batteries. Thus, a lead crystal battery containing 31 or 57 plates can receive about 10 to about 15 times more electric current than a lead acid battery due to its lower internal resistance. As a result, a lead crystal battery can be charged much faster than a lead acid battery. Likewise, the discharge rate of a lead crystal battery has improved because it can supply significantly more electric current faster than a lead acid battery.

Figure 3 shows the discharge curve of a lead crystal cell according to the invention and the discharge curve of a typical lead acid cream. In this figure, the discharge curve of the lead crystal cell is shown in solid lines, while the discharge curve representing the lead acid cell is shown in broken lines. A comparison of these two curves shows that during the first 16 minutes (i.e. corresponding to a discharge cycle of about 80 '/ j) the electromotive force of the lead crystal cell remains constant and then decreases very little from 2.32 to about 2.30 volts, while the electromotive force of the lead acid cell the force decreases continuously over the same period from 2.1 to about 2.0 volts. This difference is particularly significant in batteries made from such cells and shows that a lead crystal battery can retain a higher electromotive force than a lead acid battery, so it has superior performance.

In addition, the lead crystal battery of the invention has about 25 to about 30% more capacity than a conventional lead acid battery. In addition, the lead crystal cell is capable of much more complete charging and discharging without any after-reaction or self-charging, compared to a lead acid cell. Thus, a lead crystal battery has a much higher electrical capacity than a lead acid battery of comparable weight and volume. Cells made according to the above principles generate about 0.1 to about 0.2 volts more electromotive force than the conventional battery creams from which lead acid batteries are made.

As described above, sintered lead and cadmium were deposited on the surface of the support plates by hot spraying to form a homogeneous, uniform and adhesive Pb-Cd layer on this surface. Two other methods for forming such Pb-Cd layers on the surface of a Pb-Sb support plate are explained below.

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According to another embodiment of the invention, a soft granular 1: 1 mixture of lead and cadmium with a particle size of about 100 to almost 500 micrometers is dissolved and mixed into a suitable organic liquid, such as methanol (or ethanol), as a paste. This paste is then applied to the surface of the support plate by means of a suitable sieve. The methanol is then evaporated, the plate is dried and the Pb-Cd is sintered for about 3 seconds in a press at a temperature of about 300 to about 400 ° G. Even now, the temperature and pressure during sintering must be carefully monitored to avoid the formation of a Pb-Cd alloy.

The thickness of the Pb-Cd layer on the support plate can be adjusted by appropriate selection of the screen and by spreading a suitable amount of paste evenly on the surface of the plate. Thus, a layer of Pb-Cd about 0.5 mm thick can be laid on both sides of the support plates.

After the desired thickness layer is formed on the support plate, it is immersed in a container containing a dilute sulfuric acid solution and a lead plate, as already described above with reference to Fig. 1, whereby crystalline and polycrystalline lead peroxide (PbO 2) is similarly formed on the support plate surface. Cadmium from the Pb-Cd layer reacts with sulfuric acid and precipitates as cadmium sulfate, from which cadmium can be recovered and reused, after which one or more support plates are used to prepare a lead crystal battery as described above with reference to Figure 2.

According to another embodiment of the invention, a hard dense lead-cadmium alloy is deposited on the support plate electroplated in a fluoroborate bath. Thus, two electrodes are obtained, one made of lead-antimony alloy as the cathode and the other made of lead-cadmium alloy as the 1: 1 anode, which are then immersed in a fluoroborate bath having the following composition: lead fluoroborate, Pb (BF 2) 2 119 g of metallic lead , Pb 65 · 'fluoroboric acid, HBF ^ 1.0 g boric acid 8.0 g cadmium urofluoroborate Cd (BP ^) 32.5 g 12 70490 cadmium metal Cd 12.0 g ammonium fluorohydrate 8.0 g water 134 g The electrodes were then connected at 5 volts to the positive and negative terminals of the voltage source for one hour until a uniform layer of cadmium and lead, about 0.1 mm thick, had formed on each surface of the cathode. The power supply was then turned off, the cathode removed from the bath, rinsed clean with water and dried.

To prepare three support plates with crystalline and polycrystalline lead peroxide on the surfaces, three cathode support plates prepared as described above were immersed in an electrolyte formed by dilute sulfuric acid, after which they were treated, e.g., as described in connection with Fig. 1. The support plates thus obtained were then used to make a lead crystal cell as described above with reference to Fig. 2.

From the detailed description given above, it is clear that the lead crystal battery according to the invention is considerably superior to the lead acid battery. In addition to the numerous unique features described above, a lead crystal battery is usually about 15 to about 30% lighter than a lead acid battery of comparable size and capacity, and the lead crystal battery has a capacity of about 25 to about 30% greater compared to a lead acid battery of similar size and weight. . The ability of the battery according to the invention to receive much more power in a much shorter time due to the significantly lower internal resistance and higher activity of this battery makes it particularly suitable for use in vehicles requiring fast acceleration, e.g. electric vehicles and cars and other electric power sources.

The lead crystal batteries according to the invention have little or no sulphation. This means, as a practical fact, that these batteries can discharge to a point approaching zero voltage. Instead, sulfation is a fairly common phenomenon in lead-acid batteries, so lead-acid batteries cannot be discharged below a voltage of about 1.5 to 1.8 volts because otherwise permanent sulfation will occur in those lead states that hold the active mass paste in place.

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It should also be borne in mind that although the invention has been described and illustrated in some detail above, numerous changes and / or modifications may be made which are apparent from the foregoing description and thus fall within the spirit and spirit of the present invention.

Thus, instead of using Ph-3b support plates, an inert non-conductive support plate (e.g., a suitable plastic, or cellulosic material) can be used on which lead or a mixture of lead and antimony can be calculated as described above. Such support plates are considerably lighter than Ph-Sb support plates, and therefore batteries made from them will also be considerably lighter.

Although the invention has been described above with reference to a Ph: Cd weight ratio of 1: 1, this ratio can range from about 30% to about 70% by weight, and suitable results are obtained in the range of about 45% to about 55% by weight. However, optimal results are obtained if approximately equal amounts of weight of both components are used.

If the mixture is predominantly lead, e.g. 70% by weight, the Pb-Cd layer will be softer and less porous, whereas if the cadmium component is used predominantly, e.g. 70% by weight of the mixture, the formed Pb-Cd layer will be harder and more porous. Optimal hardness and porosity of the Pb-Cd layer are achieved in the case where the mixture ratio is approximately 1: 1 by weight.

Claims (8)

14 70490 An electrode for lead-acid batteries, which electrode is formed from a conductive support coated with lead dioxide, characterized in that lead dioxide is present not only in the usual crystalline form of lead dioxide but also in polycrystalline form as crystals at different stages of growth and development. A negative electrode for a lead-acid battery according to claim 1, characterized in that it is prepared by converting a lead-dioxide coating on a conductive support in which lead dioxide is present not only in the usual crystalline form of lead dioxide but also in polycrystalline form as crystals of different growth and development stages. A method of manufacturing an electrode according to claim 1, characterized in that the support is coated with a lead-cadmium mixture, after which the lead of the mixture is anodized in sulfuric acid to lead dioxide, whereby cadmium is substantially soluble in sulfuric acid, and lead is used as the cathode. A method according to claim 3, characterized in that the lead-cadmium layer is sprayed onto the support hot in a reducing atmosphere. A method according to claim 3, characterized in that the paste formed in the organic liquid reducing lead and cadmium is applied to the support and the liquid is evaporated off. Method according to Claim 3, characterized in that the lead-cadmium layer is applied galvanically. Process according to Claim 4, characterized in that the melt contains 30 to 70% by weight, preferably 45 to 55% by weight, of lead. Process according to Claim 4 or 7, characterized in that the weight ratio of lead to cadmium in the melt is 1: 1. 70490 15