MXPA98000695A - A nickel battery electrode that has active multi-composition nickel hydroxide materials - Google Patents

Abstract

The present invention relates to a large cycle, high capacity life electrode which includes an electronically conductive substrate for conducting electricity through the electrode and an electrochemically active nickel hydroxide material in electrical contact with the electronically conductive substrate, Electrochemically active nickel hydroxide material is composed of at least two different solid solution nickel hydroxide materials and their relative compositions alter the local redox potential or porosity to force the discharge of the electrode in a manner similar to stages from the hydroxide material of the electrode. nickel removed from the network or conductive substrate, through any intermediate nickel hydroxide materials, to the nickel hydroxide material adjacent to the network or conductive substrate

Description

Nickel in the inventive electrodes exhibit multiple electron transfer. In rechargeable alkaline batteries, weight and portability are very important considerations. It is also advantageous for rechargeable alkaline batteries to have longer operating lives without the need for periodic maintenance. Rechargeable alkaline batteries are used in numerous consumer devices such as calculators, portable radios, and cell phones. They are often configured in a sealed energy package that is designed as an integral part of a specific device. Rechargeable alkaline batteries can also be configured as larger batteries that can be used, for example, in industrial, aerospace, and electronic vehicles applications. There are many types of Ni-based batteries such as nickel cadmium ("NiCd") batteries, nickel metal hydride ("Ni-MH"), nickel acid, nickel-zinc, and nickel-iron. NiCd rechargeable alkaline batteries are the most widely used although it seems that they will be replaced by Ni-MH batteries, Ni-MH batteries made of synthetically machined materials have higher operating parameters and contain non-toxic elements. Ni-MH batteries use a negative electrode that is capable of reversible electrochemical storage of hydrogen. Ni-MH batteries usually employ a positive electrode of the nickel hydroxide material. The positive and negative electrodes are separated from each other in the alkaline electrolyte. After the application of an electric potential between the Ni-MH battery, the Ni-MH material of the negative electrode is charged by the electrochemical absorption of hydrogen and the electrochemical discharge of a hydroxyl ion, as shown in equation (1). ): charge M + H20 + e "MVI-H + OH (1) * Discharge The reactions of the negative electrode are reversible After the discharge, the stored hydrogen is released to form a water molecule and release an electron. which take place in the positive electrode of nickel hydroxide of a stack of Nh-MH are shown in equation (2): Load Ni (OH) 2 + OH ".,] i» NiOOH + H20 + e ~ (2) Download The Ni-MH materials are discussed in detail in U.S. Patent No. 5,277,999 assigned to Ovshinsky, et al. , the contents of which are incorporated for reference. As mentioned previously, Stanford R. Ovshinsky is responsible for inventing new and fundamentally different electrochemical electrode materials. As predicted Ovshinsky, the detailed investigation of the team of Ovshinsky determines the dependence on simple, relativily pure compounds is a major deficiency of the prior art. . It was found that relatively pure crystalline compounds have a low density of hydrogen storage sites, and the type of available sites are presented accidentally and are not designed in the volume of the material. In this way, the storage efficiency of hydrogen and the subsequent release of hydrogen to form water is determined to be deficient. Applying these fundamental principles of disorder to the storage of electrochemical hydrogen, Ovshinsky drastically moves away from conventional scientific thinking and creates a disordered material that has an ordered local environment where the total volume of material is provided with catalytically active hydrogen storage sites. The short or local rank order is elaborated in U.S. Patent No. 4,520,039 assigned to Ovshinsky, tituted Compositionally Varied Materials and Method for Synthesizing the Materials, the contents of which are incorporated for reference. This patent discusses how disordered materiales do not require any periodic local order and how, using Ovshinsky's techniques, it is an additional distinguishable feature. In many disordered [materials] ... it is possible to control the short range order parameter and therefore achieve drastic changes in the physical properties of these materials, including forcing coordination numbers for elements ... S. R. Ovshinsky, The Shape of Disorder, 32 Journal of Non-Crytstalline Solids at 22 (1979) (emphasis added). By forming alloys of metal hydrides of such disordered materials, Ovshinsky and his team are able to increase the reversible characteristics of hydrogen storage required for efficient and economical battery applications, and to produce, for the first time, commercially viable batteries that have a high density of energy storage, efficient reversibility, high electrical efficiency, bulky hydrogen storage without structural carriage or poisoning, long cycle life, and deep discharge capacity. The improved characteristics of these alloys results from the assembly tailored to the local chemical order and hence the local structural order by the incorporation of selected modifying elements in a host matrix. Alloys of metal hydrides have a substantially increased density of catalytically active sites and storage sites compared to conventional ordered materials. These additional sites are responsible for the improved electrochemical charge / discharge efficiency and an increase in electrical energy storage capacity. The nature and number of storage sites can even be designed independently of the catalytically active sites. More specifically, these alloys of multiple disordered components are thermodynamically assembled to allow the storage of hydrogen atoms in a wide range of modulated bonding forces within the range of reversibility suitable for use in secondary battery applications. Based on these principles of disordered materials, as described above, a family of extremely efficient electrochemical hydrogen storage materials is formulated. These are the Ti-V-Zr-Ni type active materials as described by the Ovshinsky team in U.S. Patent No. 4,551,400 ("the" 400 patent "), the description of which is incorporated herein. For reference, these materials reversibly form hydrides in order to store hydrogen All the materials used in the "Patent 400" use a Ti-V-Ni composition, wherein at least Ti, V, and Ni are present with at least one or more Cr, Zr, and Al phases. The materials of the "Patent 400" are generally multi-phase polycrystalline materials, which may contain, but are not limited to, one or more phases of the Ti-V-Zr material with crystalline structures of the Type of C14 and C15 Other Ti-V-Zr-Ni alloys can also be used to fabricate negative rechargeable hydrogen storage electrodes One such family of materials is that described in U.S. Patent No. 4,728,586 ( "the" Patent 586"), you tula Enhanced Charge Retention Electrochemical Hydrogen Storage Alloys and an Enhanced Charge Retention Electrochemical Cell, the description of which is incorporated for reference. The surface roughness characteristic of the metallic electrolyte interface is a result of the disordered nature of the material. Since all the constituent elements, as well as many alloys and phases thereof, are present in all the metal, they are also represented on the surfaces and in the slits which are formed at the metal / electrolyte interface. In this way, the roughness characteristic of the surface is descriptive of the interaction of the physical and chemical properties of the host metals as well as the alloys and crystallographic phases of the alloys, in an alkaline environment. It is believed that the chemical, physical, and microscopic crystallographic parameters of the individual phases within the storage alloy material of hydrogen are important to determine their macroscopic electrochemical characteristics. In addition to the physical nature of its rough surface it has been observed that V-Ti-Zr-Ni alloys tend to reach a continuous state and particle size condition. This continuous state surface condition is characterized by a relatively high concentration of metallic nickel. These observations are consistent with a relatively high rate of elimination through the precipitation of the titanium and zirconium oxides from the. surface and a much slower speed of nickel solubilization. The resulting surface appears to have a higher concentration of nickel than would be expected from the bulky composition of the negative hydrogen storage electrode. Nickel in the metallic state is electrically conductive and catalytic, imparting these properties to the surface. As a result, the surface of the negative hydroponic storage electrode is more catalytic and conductive than if the surface contained a higher concentration of insulation oxides. In rechargeable alkaline batteries, the discharge capacity of a nickel-based positive electrode is limited by the amount of the active material, and the efficiencies of charge. The charging capacities of a negative Cd electrode and a negative MH electrode are both provided in excess, to maintain optimum capacity and provide overload protection. In this way, a goal to make a positive nickel electrode is to obtain it with as high a density of energy as possible. The volume of a positive nickel electrode is sometimes more important than the weight. The density of volumetric capacity is usually measured in mAh / cc and the specific capacity is written as mAh / g. In the present, positive electrodes of nickel hydroxide are used sintered or pasted in the NiCd and Ni-Mh batteries. The process for manufacturing sintered electrodes is well known in the art. Conventional sintered electrodes usually have an energy density of around 480-500 mAh / cc. In order to achieve a significantly higher load, the real tendency has been to move away from sintered positive electrodes and move towards foam or paste electrodes. The nickel-plated electrodes consist of nickel hydroxide particles in contact with a conducting network or substrate, preferably having a large surface area. There are several variants of these electrodes including the so-called nickel electrodes attached to plastic which use graphite as a microconductor and also including the so-called metal foam electrodes which use high porosity nickel foam as a substrate-loaded substrate. of spherical nickel hydroxide and additives that improve the conductivity of cobalt. Pasted electrodes of the metal foam type have penetrated the consumer market due to their low cost and higher energy density in relation to the sintered nickel electrodes. Conventionally, the reaction of the nickel battery electrode has been considered to be an electron process involving the oxidation of divalent nickel hydroxide to trivalent nickel oxyhydroxide in the charge and subsequent discharge of the trivalent nickel oxyhydroxide to divalent nickel hydroxide, as shown in equation 2 described later. Some recent evidence suggests that quadrivalent nickel is involved in the redox reaction of nickel hydroxide. This is not a new concept. In fact, the existence of quadrivalent nickel was first proposed by Thomas Edison on some of his first battery patents. However, the total utilization of quadrivalent nickel has never been investigated. In practice, the capacity of the electrode beyond the theoretical capacity of transfer of an electron is not usually observed. One reason for this is the incomplete use of the active material due to the electronic isolation of the oxidized material. Since the reduced nickel hydroxide material has a high electronic resistance, the reduction of the nickel hydroxide adjacent to the collector forms a less conductive surface that interferes with the subsequent reduction of the active material oxidisate that is removed. Ovshinsky and his team have developed materials for positive electrodes that have demonstrated reliable transfer of more than one electron per nickel atom. Such materials are described in U.S. Patent No. 5,344,728 and No. 5,348,822 (which disclose stabilized, disordered positive electrode materials) and copending U.S. Patent Application No. 08 / 300,610 filed on August 23, 1994, and U.S. Patent Application No. 08 / 308,764 filed on September 19, 1994. An object of the present invention is a nickel positron electrode with improved capacity and decreased cost. Another subject of this invention is a nickel hydroxide electrode resistant to swelling. Still another object is a nickel hydroxide electrode capable of maintaining the improved capacity throughout its cycle life while operating over a wide temperature range. These and other objects of the invention will be satisfied by the high capacity, high life positive electrode of the present invention. The electrode includes an electronically conductive active substrate to conduct electricity through the electrode and an electrochemically active nickel hydroxide material in electrical contact with the electronically conductive substrate, the electrochemically active nickel hydroxide material is composed of at least two hydroxide materials Nickel of solid solution different each having different compositions. The placement of the at least two different solid solution nickel hydroxide materials and their relative compositions alter the local redox potential or porosity to force the electrode discharge in a one-stage mode from the nickel hydroxide material remote from the network or conductive substrate, through any intermediate nickel hydroxide material, to the nickel hydroxide material adjacent to the conductive network or substrate. More specifically, the positive electrode of the present invention includes a conductive substrate and two or more compositionally distinct nickel hydroxide materials each having different amounts of the chemical additive content, such that the electrochemical capacity of the nickel battery electrode it is increased over the electrodes which contain a uniform composition of the nickel hydroxide material. The embodiments of this invention include thin film nickel hydroxide electrodes with layers of nickel hydroxide active material that differ in additive content, sintered nickel hydroxide electrodes with one stage impregnation of compositionally distinct nickel hydroxide materials. , and nickel-plated hydroxide electrodes containing nickel hydroxide particles with regions of compositionally distinct nickel hydroxide materials. In a preferred embodiment, the different solid solution nickel hydroxide materials are disposed in discrete detectable layers of different composition, which are placed inside the electrode such that a first of solid solution nickel hydroxide material is placed predominantly adjacent to the conductor substrate, a second nickel hydroxide material of solid solution, having a redox potential and / or greater porosity than the first nickel hydroxide material, is placed predominantly adjacent to the first nickel hydroxide material, still remote from the conductive substrate, and each successive nickel hydroxide material, if any, has a higher redox potential and / or porosity than the preceding material and is placed adjacent to the preceding material, still remote from all other preceding materials and the conductive substrate. Each of the different nickel hydroxide materials of solid solution can contain all the same elements as well as others and still contain different percentages of these elements or, on the other hand, one or more of the solid solution nickel hydroxide materials can contain at least one chemical modifying element not present in other materials. Chemical modifiers such as cobalt, manganese, and silver change the redox potential and consequently the discharge potential in the cathodic direction, this is to less positive potentials. Chemical modifiers such as cadmium, cerium, chromium, copper, iron, lanthanum, lead, yttrium, and zinc change the redox potential and consequently the discharge potential in the anodic direction, this is to more positive potentials. Chemical modifiers such as zinc, aluminum, and manganese appreciable solubility in basic solutions provide increased porosity. The chemical modifying element can be selected from the group consisting of Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Sr, Cd, Ce, La, Pb, Y, Se, Ag, Sn and Zn. Some particularly useful combinations of the nickel hydroxide materials include: 1) a first solid solution nickel hydroxide material including 5-15% Co as the chemical modifying element and a second solid solution nickel hydroxide material which includes 0-15% Zn as the chemical modifying element. 2) A first nickel hydroxide material of solid solution including 5-15% Mn as the chemical modifying element and a second solid solution nickel hydroxide material including 0-15% Zn as the modifying element chemical; and 3) a first nickel hydroxide material of solid solution including 5-15% Co as the chemical modifying element and a second solid solution nickel hydroxide material including 5-15% Mn as the element chemical modifier and a third solid solution nickel hydroxide material including 0-15% Zn as the chemical modifying element. Finally, one or more of the nickel hydroxide materials can be a disordered material having at least one structure selected from the group consisting of amorphous, mircrocrystalline, polycrystalline that lacks large range compositional order, or any combination thereof. BRIEF DESCRIPTION DB IOS DRAWINGS Figure 1. Shows the electronic isolation of oxidized nickel hydroxide material by reduced nickel hydroxide; Figure 2. Shows how the layers of the nickel hydroxide material furthest from the outlet apparatus can be more completely reduced without the intervention of a barrier of isolation of the reduced material; Figure 3. Shows the loading / unloading results for thin films of a-Ni (OH) 2 and ß-Ni (OH) 2 with and without 10% precipitated cobalt; and Figure 4. Describes a representation of a stratified nickel hydroxide particle of the present invention, specifically indicating the redox potential and / or different porosity of the individual layers. The use of quadrivalent nickel positive electrode materials could theoretically double the specific energy of a nickel battery electrode. Since only half of the active material could be necessary, this could simultaneously reduce the cost of the material. Despite this, there have been few attempts to develop such material for nickel battery electrodes. Without wishing to be bound by a theory, the inventors of the present believe that the factor limiting the reaction of the nickel electrode to equivalent capacities to one electron or less is the low utilization of the active material of nickel hydroxide. It is believed that the low utilization is caused by the electronic isolation of the oxidized nickel hydroxide material by the formation of highly resistant, dense, reduced nickel hydroxide adjacent to the active material and by deficient transport of ions to the inner portions of the electrode which they are far from the electrolyte. This is illustrated in fig. 1. The present invention solves such limitations of electronic isolation and ion transport through the use of a unique disordered nickel hydroxide material formulated using new chemical / structural modification techniques. It should be noted that the term "substrate" as used herein relates to any electronically conductive network, foam, grid, plate or sheet manufactured from any material. This includes conventional sheets, plates and nickel foams, as well as networks, fibers or carbon particles, and cobalt oxyhydroxide networks. In this invention, the electronic isolation of the active material is avoided by improving the dynamic electronic conductivity of the active material at the interface with the conductive substrate and by improving the porosity of portions of the nickel hydroxide far from the power outlet apparatus. The reduction of the nickel hydroxide for the insulation form is delayed at the interface of the active material by adjusting the redox potential to a level below that of the outer layer or layers. The redox potential for the oxidation-reduction reaction of nickel hydroxide can be adjusted by the addition of chemical additives such as cobalt or manganese which decrease the potential or zinc which raises the potential. The quantitative effects of cobalt, manganese, zinc, and aluminum on discharge potentials are given in Table 0.

With the adjustment of the redox potentials, the layers of the active material of nickel hydroxide furthest from the outlet apparatus can be further reduced completely without the intervention of the reduced material insulation barrier as shown in the Figure. 2. After the reduction of the outer layer or layers, the layer adjacent to the outlet apparatus is still reduced despite a slightly reduced potential. Due to its proximity to the outlet apparatus, the discharge of the inner layer is easier. Still, the discharge of the inner layer may be impeded slightly due to the limitations of ion transport through the outer layers. Ideally, this is also adjusted by increasing the porosity of the outer layer. This can be done through the use of so-called "subtractive" additives in the active material of nickel hydroxide such as zinc or aluminum which can be separated by leaching without harmful effects that provide increased porosity to the outer layers. This invention can be applied to all types of nickel battery electrodes including thin film electrodes, sintered nickel electrodes, and nickel plated electrodes. The application to thin-film electrodes is direct with a ultilap in such a way that the redox potential of an inner layer is less than that of an outer layer and / or porosity of an outer layer exceeds that of the inner layer. The nickel hydroxide layers can be sequentially deposited cathodically from deposition solutions of variable composition. Alternatively, the layers can be deposited by dipping in nickel salt solutions with various additives precipitated by subsequent dips in caustic solutions. In the sintered electrode embodiment of this invention, the compositionally distinct nickel hydroxide materials are incorporated into a sintered nickel plate substrate. The nickel hydroxide materials in direct contact with the nickel plate power outlet apparatus are ideally those with a lower redox potential and / or lower porosity than the nickel hydroxide materials remote from the power outlet apparatus of the nickel plate. The compositionally different nickel hydroxide materials can be incorporated conveniently in alternate impregnations by chemical and / or electrochemical methods. The first impregnation will tend to be in direct contact with the socket apparatus of the nickel plate. Subsequent impregnations will be incrementally removed from the power outlet apparatus. The application of this invention to nickel-plated electrodes is somewhat different. Pasted electrodes have included nickel hydroxide particles which may be spherical or irregular. The electronic current is attracted to the outer surface of these particles which are in direct contact with a conductive network such as particles of the graphite microconductor (as described in U.S. Patent Application No. 08 / 300,610), a conductive network of cobalt oxyhydroxide (as described in United States Patent Application No. 08 / 333,457), and / or other conductive networks. In this way, the outer surface or cover of the particles of the nickel hydroxide active material can preferably be comprised of nickel hydroxide with a decreased redox potential to avoid electronic isolation of the internal portions of the particles. Similarly, the inner portions of the particle of the nickel hydroxide active material can preferably be of improved porosity to allow the penetration of the electrolyte into the remote electrolyte particle portions. Thus, in this embodiment of the invention, the particles of Nickel hydroxide comprised of an inner cover of higher porosity and an outer shell of lower redox potential are incorporated into the nickel-plated hydroxide electrodes. See Figure 4. Alternatively, the individual compositionally distinct nickel hydroxide particles can be mixed to provide partial benefit of this invention by providing some ratio of the nickel hydroxide with a lower redox potential at the interface of the current collection apparatus so that prevents complete electronic isolation of active material during unloading. EXAMPLE I: BILOT FILMS WITH COBALT ADDITIVES The films of -Ni (OH) 2 are deposited on the inert Au sheets (1.2 x 1.4 cm) of a nickel nitrate solution with or without 10% cobalt nitrate. The deposition is at 20 mM (6 mA / cm2) per 100 seconds to produce films approximately 1 micron thick. The bilayer films are formed by deposition from a solution at 20 mA for 50 seconds followed by the deposition of a second solution at 20 mA for 50 seconds. The ß Ni (OH) 2 films are prepared by hydrothermal conversion of the a-Ni (OH) 2 films. This involves immersing the films a-Ni (OH) 2 >;, prepared as described above, for one hour in 0.01 m KOH heated at 95 ° C. Conversion to the ß-phase is confirmed by XRD and electrochemical behavior in cyclic voltometric measurements. For electrochemical measurement of the charge / discharge capacity, the gold electrode is placed in the center of a rectangular plexiglass stack that has nickel counter electrodes. The test stack contains 9 ml of 30 w / o KOH with 1.5 w / o LiOH. The reference electrode is Hg / HgO. The film on the gold electrode is charged at 2 mA beyond the point at which the evolution of oxygen occurs. The film is then downloaded at 2 mA at 0 V vs. Hg / HgO which takes approximately 10 minutes. The films for Ni and Co content are analyzed by atomic absorption (AA) measurements. A theoretical discharge capacity is obtained from the content of nickel and total cobalt and the number of electrons per metal atom is calculated. (It is generally known that cobalt does not participate in the charge-discharge process. However, this procedure includes the contribution of cobalt to the weight of the film and allows direct comparison of the specific capacities of the active materials). The nickel battery electrodes may be comprised of a-Ni (OH) 2. And ß Ni (OH) 2 and other phases. The loading-unloading results for thin films of a-Ni (OH) 2. Y ß Ni (OH) 2 with and without co-precipitate at 10% coprecipitated are shown in Figure 3. Higher discharge capacities are observed with a-Ni (OH) 2 films. . With both a-Ni (OH) 2 films. And ß-Ni (OH) 2, cobalt decreases charge and discharge voltages. The effect is more pronounced in ß Ni (OH) 2 films. Films of multiple compositions are prepared by depositing a-Ni (OH) 2 films. bilayers A layer comprised of nickel hydroxide without cobalt additive. The bilayer films with cobalt in either the outer or inner layer are prepared with a total film thickness of 1 micron and a total concentration of about 5% co-precipitated cobalt. For comparison, films of nickel hydroxide without cobalt and films of nickel hydroxide with a uniform concentration of about 10% cobalt are also prepared with a thickness of 1 micron. The bilayer films of ß Ni (OH) 2 are prepared by converting the bilayer films of a-Ni (OH) 2. a ß Ni (OH) 2 by hydrothermal treatment. Analytical measurements confirm that bilayer films are deposited. XPS is used to analyze the atomic composition of the surface layers of both films of a composition and bilayer films. XPS of the surface of a single film with 10% coprecipitated cobalt shows 20 atomic percent of nickel and 2 atomic percent of cobalt as expected for the 10: 1 ratio of coprecipitate. A similar atomic relationship is found with a bilayer film with 10% cobalt coprecipitated in the outer layer. XPS of the outer surface of a bilayer film with 10% coprecipitated cobalt in the inner layer shows only 22 atomic percent of nickel without cobalt detection. Cobalt is detected by EDS measurements which probe below the surface and in both layers. Quantitatively, it is shown that cobalt is present in the film at the level of about 5% by the ICP analysis of the dissolved film as expected. The results of the discharge capacity of batteries using bilayer films are shown in Table 1. The films are loaded at 2 mA with 2 minutes of overcharge and then discharged at 2 mA. The discharge capacities are expressed as electrons per metal atom (Ni + Co) in the bilayer nickel hydroxide films which differ in the content of the cobalt additive compared to the results with uniform additive content and results without additive. For a-Ni (OH) 2 arabos. and ß Ni (OH) 2, the bilayer films with cobalt in the inner layer provide a higher capacity than the films with a cobalt composition which in turn provides a higher capacity than the films with cobalt only in the outer layer. The best results are shown with cobalt in the inner layer. Strikingly, this invention allows a person to reduce the amount of the expensive cobalt additive by a factor of two or simultaneously increase the discharge capacity.

The role of the redox potentials in this example can be shown by comparing the discharge potentials of components of the bilayer films. The discharge potentials for films loaded with a-Nio9Coo? (OH) 2 and a-Ni (OH) 2 are 0.29 and 0.31 V against the reference electrode of Hg / HgO, respectively, when discharged at a ratio of 2 mA . The corresponding discharge potentials for films of ß-Ni09C? Or? (OH) 2 and ß-Ni (OH> 2 are 0.31 and 0.34 V, respectively.) The differences in the redox potentials will force the non-cobalt layers to be discharged. preferably before discharge of cobalt layers in bilayer films This should result in a decrease in the cobalt film discharge capacity in the outer layer due to its initial discharge from the inner layer leading to the electronic isolation of the layer This should also result in an increase in the capacity of discharge of bilayer films with cobalt in the inner layer due to the preferential discharge of the outer layer first leading to a smaller electronic isolation on the outer part of the film. effects are observed in Table 1. EXAMPLE II: BICAPA FILMS WITH ADDITIVES DF MANGANESE AND ZINC A series of films -Ni (OH). are deposited on inert Au sheets (1.2 x 1.4 cm) of a 0.1 M nickel nitrate solution with or without manganese nitrate and zinc. The films are deposited at 20 mM (6 mA / cm2) for 100 seconds producing films of approximately 1 micron in thickness. The bilayer films are deposited by deposition from a solution at 20 mA for 50 seconds followed by the deposition of a second solution at 20 mA for 50 seconds. The ß Ni (OH) 2 films are prepared by hydrothermal conversion of the a-Ni (0H) 2 films. The electrochemical measurements are performed as in Example 1. The films for Ni, Mn, and Zn content are analyzed by atomic absorption (AA) measurements. A theoretical discharge capacity of the total content of nickel, manganese and zinc is obtained and the number of electrons per atom of metal is calculated (it is generally known that manganese and zinc do not participate in the charge-discharge process. this procedure includes the contribution of manganese and zinc to the weight of the film and allows direct comparison of the specific capacities of the active materials). Analytical measurements confirm that bilayer films are deposited. XPS used to analyze the atomic composition of the surface layers shows nickel at 20 atomic percent and 5 atomic percent zinc, but not manganese in films that have internal layers with coprecipitated manganese and outer layers with coprecipitated zinc. ICP analyzes show that manganese is present in the film as expected. Analyzes of the films before and after the charge-discharge cycles show that the zinc is leached from the film during the operation producing considerable porosity to the outer layer of the films. The results of the discharge capacity with the thick bilayer films are given in Table 2. Again, the films are loaded at 2 mA with 2 minutes of over charge and then discharged at 2 mA. The discharge capacities are expressed as electrons per metal atom (Ni + Mn + Zn) in bilayer films of nickel hydroxide which differ in the content of the manganese and zinc additive compared to the results with uniform content of additive, results with Cobalt additive and results without additive. For both a-Ni (OH) 2. And ß-Ni (OH) 2 > bilayer films with manganese in the inner layer and zinc in the outer layer provide a film electrode of highly remarkable capacity. The capacity provided by a bilayer film with manganese and zinc additives according to this invention produces a capacity which is not only greater than those of the films without additives, but even considerably greater than those with the expensive additive of cobalt. It should be noted that this effect is not due to the combination of Mn and Zn alone, but requires multiple compositions spatially arranged as a bilayer.

The role of the redox potentials in this example can be shown by comparing the discharge potentials of components of the bilayer films. The discharge potentials for films loaded with a-Nio.9Mno.?(OH)2 and a-Nio ^ Zno.iiOH ^ are 0.31 and 0.38 V against the reference electrode of Hg / HgO, respectively, when discharged to a 2 mA ratio. The corresponding discharge potentials for films of ß-Nio.gMno OH ^ and ß- NÍ0.9Z110.1 (OH are 0.33 and 0.41 V, respectively.) The differences in the redox potentials will force the layers with zinc to be discharged preferably before of the discharge of the manganese layers in the bilayer films This should result in an increase in the capacity of discharge of bilayer films with manganese in the inner layer due to the preferential discharge of the outer layer leading to less electronic isolation in the part This is shown in Table 2. EXAMPLE III: BICAPA FILMS WITH COBALT AND ZTNC ADDITIVES A series of a-Ni (OH) 2 films are deposited on inert Au sheets (1.2 x 1.4 cm) of a 0.1 M nickel nitrate solution with or without cobalt zinc nitrate These films are deposited at 20 mM (6 mA / cm2) for 100 seconds producing films approximately 1 micron thick.

The bilayer films are deposited by deposition from a solution at 20 mA for 50 seconds followed by the deposition of a second solution at 20 mA for 50 seconds. The ß Ni (OH) 2 films are prepared by hydrothermal conversion of the a-Ni (OH) 2 films. The electrochemical measurements are performed as in Example 1. The films for Ni, Co, and Zn content are analyzed by atomic absorption (AA) measurements. A theoretical discharge capacity of the total content of nickel, cobalt is obtained and the number of electrons per atom of metal is calculated. (It is generally known that cobalt and zinc do not participate in the charge-discharge process.) However, this procedure includes the contribution of cobalt and zinc to the weight of the film and allows direct comparison of the specific capacities of the active materials. ). The results of the discharge capacity with the bilayer films are given in Table 3. Again, the films are loaded at 2 mA with 2 minutes of over charging and then discharging at 2 mA. The discharge capacities are expressed as electrons per metal atom (Ni + Co + Zn) in bilayer films of nickel hydroxide which differ in the content of the cobalt and / or zinc additive compared to the results with uniform content of additive, results with cobalt additive and results without additive. For both a-Ni (OH) 2. And ß-Ni (OH> 2, bilayer films with cobalt in the inner layer and zinc in the outer layer provide a film electrode of highly remarkable capacity.) The capacity provided by a bilayer film with manganese and zinc additives in accordance to this invention produces a capacity which is not only greater than those of the films without additives, but even considerably greater than those with the expensive cobalt additive.It should be noted that this effect is not due to the combination of Co and Zn alone, but it requires multiple compositions spatially arranged as a bilayer.

The role of the redox potentials in this example can be shown by comparing the discharge potentials of components of the bilayer films. The discharge potentials for films loaded with a-Nio.9C? O.? (OH) 2 and aNio.9Zno.?(OH) 2 are 0.29 and 0.38 V against the reference electrode of Hg / HgO, respectively, when they are discharged at a rate of 2 mA. The corresponding discharge potentials for ß-NiogCoo.iíOíTh films are 0.31 and 0.41 V, respectively. The differences in redox potentials will force the zinc layers to be discharged preferably before the cobalt layers are discharged into the bilayer films. This should result in an increase in the capacity to discharge bilayer films with cobalt in the inner layer due to the preferential discharge of the outer layer with zinc leading to less electronic insulation on the outside of the film. This effect is observed in Table 3. EXAMPLE IV; BICAPA FILMS WITH ALUMINUM ADDITIVES A series of a-Ni (OH) 2 films are deposited on inert Au sheets (1.2 x 1.4 cm) of a 0.1 M nickel nitrate solution with or without aluminum nitrate. These films are deposited at 20 mM (6 mA / cm2) for 100 seconds producing films approximately 1 micron thick. The bilayer films are deposited by deposition from a solution at 20 mA for 50 seconds followed by the deposition of a second solution at 20 mA for 50 seconds. The ß Ni (OH) 2 films are prepared by hydrothermal conversion of the a-Ni (OH) 2 films. The electrochemical measurements are performed as in Example 1. The films for Ni, and Al content are analyzed by inductively coupled plasma spectrometry (ICP). A theoretical discharge capacity of the total content of nickel, and aluminum is obtained and calculated the number of electrons per metal atom, (it is known that aluminum does not participate in the charge-discharge process.) However, this procedure includes the contribution of aluminum 'to the weight of the film and allows direct comparison of the capacities specific to the active materials). The results of the discharge capacity with the bilayer films are given in Table 4. Again, the films are loaded at 2 mA with 2 minutes of over charge and then off to 2 mA. The discharge capacities are expressed as electrons per metal atom (Ni + Al) in two-layer films of nickel hydroxide which differ in the content of the aluminum additive compared to the results with uniform content of additive, results with cobalt additive and results without additive. For both a-Ni (OH) 2. And ß-Ni (OH) 2? the bilayer films without additive in the inner layer and aluminum in the outer layer provide an improved capacity. This effect is not due to the Al additive alone, but requires multiple compositions spatially arranged as a bilayer. TA £ LA_ £ The role of the redox potentials in this example can be shown by comparing the discharge potentials of components of the bilayer films. The discharge potentials for films loaded with a-NiOH and a-Nio.gAlo. OIT are 0.31 and 0.40 V against the reference electrode of Hg / HgO, respectively, when discharged at a ratio of 2 mA. Presumably, aluminum also changes the redox potential of anodic ß-Ni (OH) 2 films. The differences in the redox potentials will force the aluminum layers to be discharged preferably before the discharge of the aluminum-free layers in the bilayer films. This should result in an increase in the discharge capacity of bilayer films with nickel hydroxide in the inner layer due to the preferential discharge of the outer layer with aluminum leading to less electronic insulation on the outside of the film. This effect is observed in Table 4. EXAMPLE V: TRICAPA FILMS WITH CO. Mn AND Zn ADDITIVES A series of a-Ni (OH) 2 films are deposited on inert Au sheets (1.2 x 1.4 cm) of a solution of 0.1 M nickel nitrate with or without cobalt, manganese, and / or 10% zinc nitrate. These films are deposited at 20 mM (6 mA / cm2) for 100 seconds producing films approximately 1 micron thick. The three-layer films are deposited by deposition from a 10% Co solution at 20 mA for 20 seconds followed by the deposition of a second solution of 10% Mn at 20 mA for 40 seconds, followed by deposition of a solution of 10% Zn at 20 mA for 40 seconds.

A series of ßNi (OH) 2 films are prepared by hydrothermal conversion of the α-Ni (OH) 2 films. The electrochemical measurements are carried out as in Example 1 and the films for Ni and various metallic additives are analyzed by ICP spectrometry. A theoretical discharge capacity of the total content of nickel and metallic additive is obtained and the number of electrons per metal atom is calculated. The results of the discharge capacity with the three-layer films are given in Table 5. The films are loaded at 2 mA with 2 minutes of over charge and then discharged at 2 mA. The discharge capacities are expressed as electrons per metal atom (Ni + Co + Mn + Zn) in three-layer nickel hydroxide films that differ in the additive content of cobalt, manganese and zinc compared to the results with uniform content of additive, results with cobalt additive and results without additive. The capacity achieved with the present invention substantially exceeds that of the spatially uniform electrodes without additives, with cobalt additive, and with mixed Co-Mn additive. TABLE 5 The role of the redox potentials in this example can be shown by comparing the discharge potentials of components of the trilayer films. The discharge potentials for a-Nio.gCoo.iCOíf, a-Nio.9Mno.?(OH)2 and a-Nio.gZno.iíOH are 0.29, 0.31 and 0.38 V, respectively. The discharge potentials for the films ß-Nio.C? O.? (OH) 2, ß-Nio.Mno.? (OH) 2 and ß-Nio.Zno íCOH ^ are 0.31, 0.33 and 0.41 V, respectively. The differences in the redox potentials will force the zinc layers to be discharged first before the discharge of the manganese layers which in turn are preferably discharged first before the cobalt layers in the three-layer films. This should result in an increase in the discharge capacity of trilayer films with nickel hydroxide in the inner layer due to the preferential sequential discharge of the outer layers leading to less electronic insulation on the outside of the film. This effect is observed in Table 5. EXAMPLE VI: SINTERED MULTIPLE COMPOSITION NICKEL ELECTRODES The sintered nickel electrodes are prepared by charging nickel hydroxide materials in the sintered nickel plate with a thickness of 0.037 inches and a porosity of 85 %. The size of these electrodes is 9/16 x% inches. The sintered plates are loaded sequentially with two nickel hydroxide compositions. The first impregnation of nickel hydroxide is done electrochemically by cathodic deposition of a 2.5 M nickel nitrate solution with or without 10% Co or Mn. This solution is maintained at a pH of 0.5 to 2 and maintained at a temperature of 45 ° C during loading at 60 mA / cm2 for 45 minutes. A load of 0.8 to 1 g / cc is reached. The second impregnation of the nickel hydroxide is made electrochemically by cathodic deposition of 2.5 M nickel nitrate with or without 10% Co or Zn. The pH of this solution is adjusted to 2. The temperature of this solution is adjusted to 45 ° C. After immersion in this solution for 1 hour, the electrode is dried at 60 ° C, and then the nickel hydroxide is precipitated by immersion in caustic solution (30 w / o NaOH) at 70 ° C for 30 minutes. The electrode is rinsed and dried and subjected to a second impregnation procedure. An additional load of 0.8 to 1 g / cc is reached, avoided by two chemical impregnations. These electrodes are tested in flooded piles containing 10 ml of Koh 30 p / o electrolyte without lithium additive. The counter electrodes are metal hydride electrodes spaced approximately 0.25 inches from either side of the working electrodes. In the first charge, the electrodes are charged at 200% capacity at a C / 2 ratio. They are then discharged at a C / 2 to 1 V ratio. Over subsequent cycles, they are charged to 115% of their discharge capacity and discharged, both at a C / 2 ratio. Three electrodes without additives provide an average of 1.05 electrons per nickel atom in the first five charge-discharge cycles. Four electrodes with 10% cobalt additives provide an average of 1.16 electrons per metal atom (Ni + Co) in the first five charge-discharge cycles. Three electrodes of the present invention impregnated first with nickel hydroxide containing 10% Mn and then with nickel hydroxide containing 10% Zn provide an average of 1.12 electrons per metal atom (Ni + Mn + Zn) in the first Five charge-discharge cycles. This is a remarkable result in which it is shown that the expensive cobalt additive can be completely replaced by inexpensive manganese and zinc additives without sacrificing capacity significantly. It should be noted that the nickel hydroxide materials in solid solution can preferably be disordered materials which have at least one structure selected from the group consisting of amorphous, microcrystalline, polycrystalline lacking large-scale compositional order, or any combination thereof . Also, while describing the specific chemical modifiers in the above examples, the modifiers of the group consisting of Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Sr can be selected. , Cd, Ce, La, Pb, Y, Se, Ag, Sn and Zn. It is understood that the description indicated herein is presented in the form of detailed embodiments for the purpose of making a full and complete description of the present invention, and that such details are not construed to limit the scope of this invention as indicated and defined in the attached claims.

Claims (4)

1. CLAIMS 1. A large-cycle, high-capacity positive life electrode for use in an alkaline rechargeable electrochemical cell characterized in that it includes: The electrode that includes at least two compositionally different nickel hydroxide materials; At least one of the hydroxide compositions. nickel having a multiphase structure comprising at least one gamma phase including a polycrystalline or microcrystalline unit stack comprising a pair of spatially arranged plates having a stable interlayer range that corresponds to a greater differential oxidation one; and At least three compositional modifiers incorporated in the material.
2. 2. The positive electrode according to claim 1, characterized in that it also includes an electrically conductive substrate in which the nickel hydroxide materials are incorporated. The placement of at least two compositionally different materials provides the discharge of the electrode in a in the form of stages from the nickel hydroxide material remote from the conductive substrate, through any intermediate nickel hydroxide materials, to the nickel hydroxide material adjacent to the conductive substrate.
3. 3. The positive electrode according to claim 1, characterized in that at least two compositionally different materials are arranged in discrete detectable layers of different composition.
4. 4. The positive electrode according to claim 2, characterized in that at least two compositionally different materials are arranged in discrete layers placed inside the electrode in such a way that: At least one main portion of a first of at least two compositionally different materials it is placed adjacent to the conductive substrate; At least one main portion of a second of at least two different materials, which has a higher redox potential than the material, is placed away from the conductive substrate and adjacent to the first material; Each successive material of at least two different nickel hydroxide materials, if any, that have a higher redox potential than the preceding material that is placed adjacent to the preceding material, still remote from all other preceding materials and the conductive substrate.