DE1771634A1 - Plate for use as an electrode base plate and process for their manufacture - Google Patents

Description

DP ».- IN ·. OIPL.-IN ·. M. »C. HÖGER - LEGAL RIGHTS - GRiESSBACH - HAECKER

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U.S.Ser.No.656,667

Texas Instruments Incorporated, Dallas, Texas, U.S.A.

Plate for use as an electrode base plate and method for making the same.

The invention relates to a porous plate for use as a base plate for accumulators with a porous, electrically conductive support member to which metal particles are connected by sintering, and a method for their manufacture »

In the known method for the production of plate materials for use as an electrode base plate

a finely divided metal powder is used for accumulators such as carbonyl nickel powder on a porous,

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June 18, 1968

deposited electrically conductive metal screen. The powder and the sieve are then heated to make the metal powder by sintering to connect with the sieve and thereby create a porous plate. If such a plate is then used for Formation of a battery electrode is used, this plate is placed in an appropriate bath to fill the plate pores immersed with nickel hydroxide material. Some of this nickel hydroxide material is deposited from the bath, in which the plate is immersed, and part of this nickel hydroxide is formed as a result of corrosion of the sintered nickel particles of the plate by reaction with the bath. All these nickel hydroxide parts are then cathodically converted into electrochemically active beta-nickel (III) hydroxides (active / 3-nickelic hydroxides) converted to thereby the to produce the desired battery electrode. It is found that, although excessive corrosion, the panel strength decreases would reduce, a certain amount of plate corrosion is desirable inasmuch as this leads to the formation of the electrochemical active material contributes and increases the charge capacity of the resulting accumulator electrode.

However, Ee was found to be during the usual electrode-forming Process in which nickel hydroxide

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is accumulated in the plate pores, very little corrosion in the plate material within plate pores occurs below a minimum size. It was also found that in the known plates a considerable part of their pore volume with such pores this minimum size or a smaller size turn off. If, therefore, the usual sintered plates

en while the electrode formation is corroding we.rdT, so is this corrosion is limited to a small part of the available plate surface area, and the corrosion

of the plate makes only a limited contribution to the charge capacity of the resulting electrode.

The invention is now based on the object of creating a base plate of this type in which a larger one Corrosion and thus a greater charge capacity can be achieved. This task is carried out at the beginning mentioned plate according to the invention solved in that Measured against the total volume, the plate has a predominant proportion of pores and only a small proportion of the pores smaller than a predetermined maximum transverse dimension,

is preferably less than 7 AX in the maximum transverse dimension. Such a plate can then to a considerable extent

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can be corroded without a noticeable reduction in the strength of the plate, this plate thereby a considerable Contributes to the charging capacity of the battery electrode. Such plates are strong and cheap in their manufacture.

The invention also relates to a simple and an inexpensive method for producing such sintered Manufacture of metal plates, and the novelty is seen according to the invention that a metal powder with a heat-decomposable powder is mixed into a powder mixture that the powder mixture on a porous, electrically Conductive support member is applied and that the object thus created is heated to the heat-decomposable To decompose powder and to bond the metal component to the support member by sintering.

The novel and improved method according to the invention for the production of porous, sintered plates thus has a process step after the finely divided metal powder, such as carbonyl Mckel powder, with a finely divided heat decomposable powder is mixed vigorously. For example, if the metal powder is carbonyl nickel powder contains, the decomposable powder is preferably a compound of this metal, for example

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wise nickel oxide ^! ticke formate or nickel carbonate powder. If necessary, a liquid carrier of the powder mixture can be used can be added to form a pulp. The powder mixture is then made up in dry or porridge form applied to a porous, electrically conductive support member, such as a woven wrapping screen, so as to Layer of even thickness on both sides of this support link to build. The powder mixture and screen are then heated to remove the heat decomposable material to decompose and to bond the metal components of the powder mixture to the carrier member by sintering, so that there is now a sintered plate with a high proportion of porosity, with the pores in only one minimum number below a predetermined pore size. Daa heat decomposable material in the powder mixture, as described above, preferably has a compound of the metal powder in question, so that the subsequent decomposition of the thermally decomposable material leaves a residual material that consists of the same Material like the metal powder is. This reat material is particularly important in the electrode-forming process reactive or corrodible and makes a significant contribution to the loading capacity of one of such Plate made electrode.

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The method according to the invention is simple and cheap

in its implementation and still results in a sintered plate with improved pore characteristics. In other words, the new and improved, sintered plate according to the invention has a high proportion of pores on the one hand, and on the other hand only a small proportion of this total pore volume consists of pores that are smaller than a predetermined size. In the subsequent use of the sintered plate according to the invention in the manufacture of accumulator electrodes the corrosion of the plate material can occur within substantially all of the pores of this plate, whereby

the charging capacity of the electrode thus formed is increased considerably, for example up to $ 15. Since the sintered Plate according to the invention also has pores of a more uniform size, so essentially all of the surface areas during the manufacture of the battery electrode can be partially corroded from this plate without overcorroded or weakened areas in the Plate emerge.

Further features and advantages of the invention will become apparent from the following description, which refers to preferred Embodiments relates,

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With the usual well-known, sirted nickel plates, which are used in the manufacture of battery electrodes, a finely divided carbonyl nickel

powder connected to a porous, electrically conductive sieve by sintering. If the height of the porosity and the pore size of such a known plate are measured, it is found that about 80 $ of the plate volume is occupied by pores which vary in size between 1 and 20 / u or more in their maximum transverse dimension. It has been found particularly important that up to 40 to 75 $ of this total pore volume are pores of less than about 10 / U and up to 30 $ of the pores are less than 7 Ax in their maximum transverse dimension.

In when such known, sintered plates an impregnation bath in the usual process for the production of electrodes are thrown, so nickel hydroxide collects in these plate pores. Part of this nickel hydroxide results from the nickel ions of the impregnation bath, while an additional part of this nickel hydroxide is the result of corrosion

of the plate material is formed by the impregnation bath. Diee means that the baths are usually alternated Baths made from ilitrate and alkaline solutions can be one

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Oxidation of the nickel surfaces of the plate will cause some of it to accumulate in the pores To form nickel hydroxide. When this nickel hydroxide is subsequently converted into an electrochemically active material this plate corrosion contributes to the charging capacity of the electrode from this plate.

It was found, however, that essentially No corrosion occurs in the known sintered plate material within plate pores that are smaller than 7 / u. and only limited corrosion in pores smaller than 10 / U. This means that when the Plate in an impregnation bath for the production of electrodes from this plate essentially all of the plate corrosion enters the plate pores, which are larger than about 7 / u are in their transverse dimension. Although it is evident that excessive plate corrosion is undesirable in this respect is, as this reduces the strength of the plate, it is nevertheless advantageous to use the entire surface of the plate in to a limited extent to corrode so as to obtain a maximum charge capacity of the electrode being formed, without that the plate construction is excessively corroded in some specific area and thereby weakened.

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Sintered nickel plates are therefore used according to the invention and the like. With a high proportion of porosity and with of a controllable Pren size created, so that essentially the entire ITickel surfaces of the plate in be corroded to a predetermined extent during the conversion of the plate to an electrode. This means, that the novel and improved plate according to the invention

is such that only an insignificant part of the pore volume consists of pores that are smaller than 7 / u in transverse dimension aind. In contrast, the proportion of the plate pore volume with pores of approximately 10 - 20 / u is kept at a maximum level, in order to ensure that a high and even plate porosity is achieved.

According to the invention, this novel, sintered plate is produced in that a finely divided, heat-decomposable Material such as nickel carbonair, mckelformate or nickel oxide powder is mixed with finely divided carbonyl nickel powder so as to form a plate powder mixture. Preferably, a sufficient amount of heat decomposing

used powder, so that the heat-decomposable powder about 7-18 mole percent of the resulting powder mixture

having. The various types of powder preferably have small particles in such a way that the powder is flaky and

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has a low density per unit volume. For example, the carbonyl nickel powder preferably has an average one Particle size between 3.4 - 3.6 / U and a weight of approximately 0.5 - 1.0 g per cubic centimeter. Preferably, the heat decomposable powder also has a small one Particle size and a low density per unit volume. For example, a nickel carbonate powder is preferred all particles are much smaller than 40 / ü and which has a density of approximately 0.4 grams per cubic centimeter. If nickel format powder in a similar way as heat decomposable Powder is used, this powder preferably has an average size of about 12 and one Volume weight of approximately 2.5 g per cubic centimeter. Preferably, the heat decomposable powder is suitable for at a temperature substantially below about 1093 ° C.

This plate powder mixture is then punched on a or a porous, electrically conductive support member such as a nickel screen woven from wire. In In one embodiment of the method according to the invention, this plate powder mixture is applied to the carrier member in dry form applied by dipping the support member in a sufficient amount of the dry powder mixture becomes that the powder mixture all surface parts

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touches the support member. In a preferred embodiment of the method, the powder mixture is first with mixed with a sufficient amount of a volatilizable liquid additive, for example a mixture from water and alcohol, so that a paste with the consistency of a homogeneous paste is formed. This pulp will then spread out on the support member so that the pores of the support member are filled and the entire surfaces of the support member are covered. The slurry is then preferably used to remove the liquid additive and heated to preliminarily attach the powder mixture to the support member. About this temporary attachment of the powder mixture To improve on the carrier member, a binder, such as, for example, can still be used in the liquid carrier of the slurry Polyethylene oxide or methyl cellulose, are dissolved, which serves to hold the powder particles on the support surfaces after the liquid additive has been removed.

The "plate powder mix" and the carrier member are then in a reducing atmosphere of a hydrogen gas, an exothermic gas or the like. Heated to so joining the carbonyl nickel metal particles to the support member by sintering and forming the desired porous plate create. Preferably, the powder and the support member are heated to a temperature between about 760 ° C and about 1093 ° C

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Heated for 15-30 minutes to perform this sintering process. This sintering can also take place at temperatures

can be carried out down to 427 ^° C. if longer sintering times are used. At these temperatures, the binding material, for example polyethylene oxide or methyl cellulose or the like, which achieves the preliminary binding, is rapidly burned off from the covered support member. In addition, the heat decomposable compound in the plate powder mixture is decomposed. This results in the formation of a very large number of pores of at least a predetermined minimum size in the plate sintered in this way. This means that this plate now consists of up to 84.3 $ of its total volume of pores and down to 22 $ of this pore volume are pores whose size is less than 10 / u, and less than about 15 $ of these pores are pores of less as 7 Ai, when the heat decomposable powder is a metal compound of the metal powder of the powder mixture, the decomposition of this compound results in a metal residue which is also bonded to the support member and to the other metal particles of the powder mixture by sintering. This metal residue forms a very desirable part of the resulting plate construction because this residue material is very reactive and very easily corroded when the plate is then used to manufacture electrodes.

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Preferably, relatively high sintering temperatures of the order of magnitude of 1065 ⁰ G "are used in the method according to the invention in order to form a plate with high strength and high resistance to flaking. The use of a higher sintering temperature also tends to reduce the size of the If such a temperature is used when sintering the powder mixture according to the invention, these high sintering temperatures also result in the tendency for the number of plate pores to be in the desired size range between 10 to 20 / rev

to bring a maximum share without this there is a noticeable loss of the entire plate porosity,

Example A.

Carbonyl nickel powder having a density of about 1 g per cubic centimeter is thoroughly mixed with a sufficient amount of a nickel carbonate powder such that the niocel carbonate powder is about 18 mole percent of the resulting plate powder mixture. A liquid carrier is then produced by dissolving approximately 10% by weight of polyethylene oxide or methyl cellulose in a solvent of 80% methanol and 20% water. The powder mixture is then mixed with the liquid carrier to form a slurry that has a smooth paste cone

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Has. The slurry is then spread on both sides of a 20 mesh wire nickel woven screen. The screen wire is approximately 0.178 mm thick. A sufficient amount of slurry is placed on this screen to form a covered screen with a total thickness of 0.635 mm. After the pulp has been dried by a slight heating to remove the liquid carrier, the covered sieve is ^{heated to about 1 ^ 065 0} G for about 15 minutes in order to burn off the polyethylene oxide component of the pulp, to decompose the nickel-carbonate powder and also the metal component of the To connect powder mixture by sintering with the sieve and thus produce the desired plate. The residual nickel, which is left over from the decomposition of the nickel carbonate powder, is also connected by sintering to the sifcb during heating. The resulting plate has a porosity ^ of 84.3 ^, and less than about 22 # of this pore volume are pores of less than about 10 Ai . Thus, in this plate, less than 12 # of the total pore volume are pores of less than 1 Ax, The plate has sufficient and advantageous strength and is characterized by the fact that it lacks any noticeable weakened areas. If the plate is subsequently corroded in a conventional electrode-forming process, the plate will corrode approximately 5 # more than the known one

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sintered plate and thus results in an electrode with a 9 $ higher capacity than an electrode made by the same method from a common and well-known sintered plate is made. It is believed that essentially all of the residual nickel passed through the decomposition of nickel carbonate powder remains while the formation of the electrode is corroded,

Example B.

In a preferred embodiment of the invention, nickel carbonate and carbonyl nickel powder are added to one another mixed in a powder mixture, with approximately 14 mole percent of the nickel carbonate powder being present. After mixing this powder mixture with a liquid carrier according to example A is the powder mixture on the Surfaces made of a woven wire nickel screen of 20 mesh,

as described above, applied and ^{sintering carried out at a temperature of approximately 1065 °} C. for 15 minutes. The resulting plate has an overall porosity

from about $ 83.6, with less than about $ 26.5 this Pore volume pores of less than about 10 / U and less than $ 11 of the total pore volume pores of

are less than 7 / u. With the subsequent corrosion of this Plate in the usual electrode-forming process, this plate corrodes about $ 10 more than the known ones

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sintered plates, and it was found that such an electrode was manufactured as a 15 $ higher capacity than an electrode that had been produced by the same process from a conventional known sintered plate is made. This record had

also excellent in strength and showed no flaking.

Example C

When a similar powder blend is made using about 7 mole percent nickel carbonate powder in combination with carbonyl nickel powder, the panel made by the above described process has a total porosity of about $ 81.75. About 31 $ of this pore volume form pores of less than about 10 / u and less than about 15 $ of the total pore volume are pores that are smaller than about 7 / u. This plate has about 5 $ more corrosion than the known sintered plates and results in an electrode with about 2 $ more capacitance than an electrode from a conventional plate.

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Example p

If a similar plate powder mixture is made using 10 mole percent nickel oxide powder in combination with carbonyl nickel powder, this plate has a total porosity of about $ 80.5 and only about $ 34 of the pore volume are pores less than "IQ AX, When this plate is converted by the usual, known electrode process, this plate corrodes about $ 2 more than a known sintered plate and results in an electrode which has a capacitance of $ 7 greater than an electrode made from a known sintered plate by the same process .

It turns out that the use of a heat decomposable powder in combination with metal powders for Formation of sintered plates results in a plate construction, which by an improved porosity and in particular an improved pore size distribution is characterized. These improved panels lead in context with the usual methods for electrode production to electrodes with an increased charge capacity per unit volume. This means that the plates according to the invention largely corrode when performing the electrode manufacturing process, so that the corroded plate material!

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in a considerable and significant way to the loading capacity which contributes electrodes made from such plates. Because this achieved improved corrosion properties are that more surface areas of the plates participate in this corrosion process, these result in improved Corrosion properties do not result in excessive weakening of the plate structure during electrode manufacture, When the "heat decomposable powder according to the invention Contains metal compounds of the same metal, which forms the main part of the sintered plate, so leaves behind the decomposition of this decomposable powder is a metal residue, which is particularly important when the load capacity is increased of the electrodes made from this improved sheet. The method according to the invention is also easy and inexpensive to perform, so that the process can be improved with a small increase in cost be achieved.

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Claims (1)

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11.6.68 Claims Porous plate for use as a base plate for accumulators with a porous, electrically conductive support member, to which metal particles are connected by sintering, characterized in that the plate has a predominant proportion of pores in relation to the total volume and only a small proportion of the pores are smaller than a predetermined maximum transverse dimension , preferably smaller than f / t in the maximum transverse dimension. 2. Plate according to claim 1, characterized in that the proportion of pores is at least about So% . 3. Plate according to claim 1 or 2, characterized in that less than 15% of the pore proportion pores with a maximum transverse dimension of less than 7 ^ '. k. Plate according to one of the preceding claims, characterized in that the electrically conductive support member is a sieve, preferably a metal sieve. - 30- 109887/0571 h - 137 11.6.68 5. Plate according to one of the preceding claims, characterized in that the electrically conductive Support member and / or the metal particles are made of nickel, 6. A method for producing a plate according to any one of the preceding claims, characterized in that a metal powder with a heat decomposable powder is mixed into a powder mixture, that the powder mixture is applied to a porous, electrically conductive support member and that the article thus created is heated to the heat-decomposable powder decompose and bond the metal component to the support member by sintering. 7. The method according to claim 6, characterized in that the heat-decomposable powder is a compound of the metal that is present in the metal powder. 8. The method according to any one of the preceding claims 6 or 7, characterized in that the metal powder is made of nickel. 9. The method according to any one of _the preceding claims 6-8, 109887/0571 " ²¹ - A 36 419 h • h - 137 24 11.6.68 heat _ characterized in that the, decomposable powder is a nickel compound, in particular nickel carbonate and / or nickel formate and / or nickel oxide. 10. The method according to any one of the preceding claims 6-9 » characterized in that the powder mixture comprises nickel powder and nickel carbonate powder. 11. The method according to any one of the preceding claims 6- lo, characterized in that the support member is a nickel screen. 12. The method according to any one of the preceding claims 6-11, characterized in that the heat-decomposable powder and the metal powder has particles of such a size that their density is less than 3 grams per cubic centimeter is. 13. The method according to any one of the preceding claims 6-12, characterized in that the heat-decomposable powder and the metal powder have particles of such a size that the density is approximately 1 gram per cubic centimeter or smaller. Method according to one of the preceding claims 6- 13 109887/0571 22nd A 36 419 h • h - 137 11.6.68 characterized in that the heat decomposable powder constitutes 7-18 mole percent of the powder mixture. 15. The method according to any one of claims 6-14, characterized in that when using nickel carbonate powder this 14 Mbl percent of the total powder mixture ^ matters. 16. The method according to any one of the preceding claims 6-15, characterized in that the powder mixture is mixed together with a liquid carrier to form a slurry which is applied to the carrier member, whereupon the liquid carrier is expelled by heating will. 17. The method according to any one of the preceding claims 6-16, ™ characterized in that the powder shoe and the Support member to a temperature between 427 ° C. and Io93 ° C. 109 ** 7/0571