USOO6077625A United States Patent (19) 11 Patent Number: 6,077,625 Yano et al. (45) Date of Patent: Jun. 20, 2000

54) NON-SINTERED NICKEL ELECTRODE FOR 0757395A1 2/1997 European Pat. Off.. ALKALINE STORAGE BATTERY 62-234867 10/1987 Japan. 1-272050 10/1989 Japan. 75 Inventors: Mutsumi Yano, Hirakata; Mitsunori 3-078965 4/1991 Japan. Tokuda, Osaka, Kousuke Satoguchi, 5-028992 2/1993 Japan. Tokushima; Shin Fujitani; Koji Nishio, WO both of Hirakata, all of Japan 96.14666A1 5/1996 WIPO. 73 Assignee: Sanyo Electric Co., Ltd., Osaka, Japan Primary Examiner Bruce F. Bell Attorney, Agent, or Firm-Birch, Stewart, Kolasch & Birch, 21 Appl. No.: 09/097,679 LLP 22 Filed: Jun. 16, 1998 57 ABSTRACT 30 Foreign Application Priority Data Non-sintered nickel electrodes for alkaline Storage batteries which can express high active material utilization efficiency Jun. 16, 1997 JP Japan ...... 9-176314 not only at the time of charging at ordinary temperature but Jun. 16, 1997 JP Japan ...... 9-176315 also at the time of charging in a high-temperature atmo Sphere are provided by using an active material powder (51) Int. Cl...... HO1 M 4/32 composed of composite particles each comprising a Sub 52 U.S. Cl...... 429/223; 429/59; 429/218.2; Strate particle containing nickel hydroxide, an inner coat 204/290 R layer covering the Substrate particle and comprising yttrium, 58 Field of Search ...... 429/223, 59, 218.2; Scandium or a lanthanoid, or an yttrium, Scandium or 204/290 R lanthanoid compound, and an outer coat layer covering the inner coat layer and comprising cobalt or a cobalt 56) References Cited compound, or composed of composite particles each com U.S. PATENT DOCUMENTS prising a Substrate particle containing nickel hydroxide, an 777,417 6/1957 Winkler. inner coat layer covering the Substrate particle and compris 5,466,543 11/1995 Ikoma et al...... 429/59 ing cobalt or a cobalt compound, and an outer coat layer 5,861.225 1/1999 Corrigan et al...... 429/223 covering the inner coat layer and comprising yttrium, Scan dium or a lanthanoid, or an yttrium, Scandium or lanthanoid FOREIGN PATENT DOCUMENTS compound. 0587973A1 3/1994 European Pat. Off.. 058797A1 3/1994 European Pat. Off.. 22 Claims, 6 Drawing Sheets U.S. Patent Jun. 20, 2000 Sheet 1 of 6 6,077.625

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6,077.625 1 2 NON-SINTERED NICKEL ELECTRODE FOR However, the non-sintered nickel electrodes mentioned ALKALINE STORAGE BATTERY above are disadvantageous in that the active material utili Zation efficiency, in particular in a high temperature BACKGROUND OF THE INVENTION atmosphere, is low. This is because, at high temperatures, the This application claims the priority of Japanese Patent 5 oxygen overVoltage of the electrode decreases and the Applications Nos. H09-176314 and H09-176315, both filed charging electrical energy is consumed not only by the on Jun. 16, 1997. charging reaction converting nickel hydroxide to nickel 1. Field of the Invention Oxyhydroxide but also by the oxygen-generating reaction The present invention relates to a non-sintered nickel resulting from decomposition of water (water in alkaline electrode for an alkaline Storage battery and, more electrolyte Solution). particularly, to an improvement in the active material with For removing this drawback, it has been proposed to add the aim of providing a non-sintered nickel electrode for an metallic cobalt, cobalt hydroxide and an yttrium compound alkaline Storage battery with which high active material to the nickel hydroxide powder to thereby provide non utilization efficiency can be achieved not only in charging at Sintered nickel electrodes capable of expressing high active ordinary temperature but also in charging in an elevated 15 material utilization efficiency over a wide temperature range temperature atmosphere. (0 to 45 ° C) (see Japanese Kokai Tokkyo Koho H05 2. Prior Art 28992). Sintered nickel electrodes produced by impregnating, However, an investigation made by the present inventors with an active material (nickel hydroxide), Sintered base has revealed that the non-sintered nickel electrodes dis plates obtained by Sintering a nickel powder on perforated closed in Japanese Kokai Tokkyo Koho H05-28992 have a Steel plates or the like are well known in the art as positive problem in that charging in a high-temperature atmosphere electrodes for use in nickel-hydrogen Storage batteries, of about 60° C. results in a markedly decreased active nickel-cadmium Storage batteries and the like. material utilization efficiency. For increasing the rate of packing or filling of an active 25 It is an object of the present invention made in view of the material in Sintered nickel electrodes, it is necessary to use foregoing to provide a non-sintered nickel electrode for the Sintered base plates with a high porosity. Since, however, the alkaline Storage battery which can express high active interparticle bond resulting from Sintering of nickel particles material utilization efficiency not only when charging is is weak, an increase in porosity of Sintered base plates conducted at ordinary temperature but also when charging is results in a tendency toward nickel particles falling away conducted in a high-temperature atmosphere. from the Sintered plates. Practically, therefore, it is impos SUMMARY OF THE INVENTION Sible to increase the porosity of Sintered base plates to a level higher than 80%. Sintered nickel electrodes thus have a In the non-sintered nickel electrode (electrode X of the problem in that the rate of active material packing is low. invention) for an alkaline storage battery as provided by the present invention, the active material powder comprises There is another problem. Namely, Since the pore size of 35 Sintered bodies from a nickel powder is generally Small, Say composite particles each composed of a Substrate particle 10 um or less, it is necessary to effect the packing of Sintered containing nickel hydroxide, an inner coat layer covering base plates with an active material by repeating Several Said Substrate particle and comprising yttrium, Scandium or times the Step of impregnation, which is complicated. a lanthanoid, or an yttrium, Scandium or lanthanoid compound, and an outer coat layer covering Said inner coat For Such reasons, non-sintered nickel electrodes have 40 recently been proposed. The non-sintered nickel electrodes layer and comprising cobalt or a cobalt compound. are produced by packing or filling base plates having a high In the non-sintered nickel electrode according to a further porosity with a kneaded mixture (paste) of an active material aspect of the invention (electrode Y of the invention), (nickel hydroxide) and a binder (e.g. aqueous Solution of arrangement of Said inner and outer coat layerS is reversed. methyl cellulose). In the case of non-sintered nickel 45 BRIEF DESCRIPTION OF THE DRAWINGS electrodes, base plates with a high porosity can be used (base plates with a porosity of 95% or more can be used), so that FIG. 1 is a graphic representation of the relationship the rate of active material packing can be increased. between the proportion of yttrium in the inner coat layer Furthermore, the active material packing into base plates is relative to the nickel hydroxide in Substrate particles and the easy. 50 active material utilization efficiency at the time of high However, when base plates having a high porosity are temperature charging. used for increasing the rate of active material packing in FIG. 2 is a graphic representation of the relationship non-sintered nickel electrodes, the current collecting prop between the proportion of yttrium in the inner coat layer erty of the base plates is worsened, hence the active material relative to the nickel hydroxide in Substrate particles and the utilization efficiency decreases. 55 discharge capacity. Therefore, for increasing the active material utilization FIG. 3 is a graphic representation of the relationship efficiency in non-sintered nickel electrodes, it has been between the proportion of the outer coat layer relative to the proposed to use, as an active material, composite particles composite particle and the discharge capacity. prepared by forming a coat layer consisting of cobalt FIG. 4 is a graphic representation of the relationship hydroxide on the Surface of nickel hydroxide particles, or 60 between the proportion of the inner coat layer relative to the composite particles prepared by forming a cobalt oxyhy Sum total of the Substrate particle plus the inner coat layer droxide layer on the Surface of nickel hydroxide particles and the discharge capacity. (Japanese Kokai Tokkyo Koho S62-234867 and Japanese FIG. 5 is a graphic representation of the relationship Kokai Tokkyo Koho H03-78965). These are attempts to between the proportion of yttrium in the outer coat layer improve the active material utilization efficiency by increas 65 relative to the nickel hydroxide in Substrate particles and the ing the electron conductivity (electric conductivity) on the active material utilization efficiency at the time of high Surface of active material particles. temperature charging. 6,077.625 3 4 FIG. 6 is a graphic representation of the relationship substrate particle is preferably 0.05 to 5% by weight. Then between the proportion of yttrium in the outer coat layer this proportion is below 0.05% by weight, it is difficult to relative to the nickel hydroxide in Substrate particles and the Satisfactorily Suppress the decrease in active material utili discharge capacity. Zation efficiency as resulting from charging in a high temperature atmosphere. When Said proportion exceeds 5% DETAILED DESCRIPTION OF THE by weight, the packing density of the active material (nickel INVENTION hydroxide) becomes low and the Specific capacity (discharge capacity) of the electrode decreases. The active material powder in the electrode X of the The outer coat layer covering the inner coat layer com invention comprises composite particles each composed of prises cobalt or a cobalt compound. AS the cobalt compound, a Substrate particle containing nickel hydroxide and coated there may be mentioned, for example, cobalt monoxide, with two layers, namely the inner and outer coat layers cobalt hydroxide, cobalt oxyhydroxide and a Sodium defined above. containing cobalt compound. The nickel hydroxide-containing Substrate particle As a method of forming an outer coat layer comprising includes Single-component particles consisting of nickel 15 cobalt hydroxide on the inner coat layer, there may be hydroxide alone, and Solid Solution particles derived from mentioned, for example, the method comprising adding a nickel hydroxide and at least one element Selected from nickel hydroxide powder the particle Surface of which has among cobalt, Zinc, cadmium, calcium, manganese, been coated with an inner coat layer, to an aqueous Solution magnesium, bismuth, aluminum, lanthanoids and yttrium. of a cobalt Salt (e.g. aqueous Solution of cobalt Sulfate), By forming Solid Solutions from nickel hydroxide and one or adjusting the pH to 9 to 12 (usually about 11) by adding more of the above-mentioned elements, the Swelling of dropwise an aqueous alkali Solution (e.g. aqueous Solution non-sintered nickel electrodes at the time of charging can be of Sodium hydroxide) with Stirring, and stirring the resulting Suppressed. mixture for a predetermined period while maintaining the The inner coat layer covering the Substrate particle com pH at a practically constant level by adding an aqueous prises yttrium, Scandium or a lanthanoid, or an yttrium, 25 alkali Solution from time to time when a decrease in pH is Scandium or lanthanoid compound. The yttrium compound found, to thereby cause deposition of cobalt hydroxide on includes yttrium hydroxide (Y(OH)), diyttrium trioxide the Surface of the inner coat layer. (YO), yttrium carbonate (Y2(CO) and yttrium fluoride The Outer coat layer comprising cobalt hydroxide can also (YF), among others. The Scandium or lanthanoid com be formed by the mechanical charging method which com pound includes hydroxides thereof (Sc(OH), LaCOH), prises dry blending the nickel hydroxide powder and a Ce(OH), Pr(OH), Nd(OH), Pm(OH), Eu(OH), Gd(OH) cobalt hydroxide powder in an inert gas using a compression , Tb(OH), Dy(OH), Ho(OH), Er(OH), Tm(OH), etc.), attrition mill. When, in carrying out this mechanical charg oxides thereof (ScC), La O, CeO2, PrO, NdO, ing method, a cobalt monoxide powder or a cobalt powder Sm2O, Eu2O3, Gd2O3, TbO7, Dy2O3, Ho-Os, Er-Os, is used in lieu of the cobalt hydroxide powder, an outer coat Tm2O, YbO, Lu-O, etc.), carbonates thereof (La(CO) 35 layer can be formed which comprises the cobalt monoxide , Ce(CO), Nd(CO), Sm(CO), etc.), and fluorides or cobalt, respectively. thereof (LaF, CeF, PrF, NdF, SmF, GdF., TbF, DyF, An Outer coat layer comprising cobalt oxyhydroxide can ErF, YbF, HoF., etc.). be formed, for example, by forming a cobalt hydroxide layer A method for forming an inner (oat layer comprising the on the Surface of the inner coat layer and then oxidizing Said hydroxide of yttrium, Scandium or a lanthanoid on the 40 cobalt hydroxide layer with an aqueous hydrogen peroxide Substrate particle Surface comprises, for example, adding a solution heated to about 40° C. An outer coat layer com nickel hydroxide powder to an aqueous Solution of a Salt of prising a Sodium-containing cobalt compound can be yttrium, Scandium or a lanthanoid (e.g. aqueous Solution of formed, for example, by adding an aqueous Sodium hydrox yttrium Sulfate), adjusting the pH to 9 to 12 (generally about ide Solution to a powder composed of particles having a 11) by adding dropwise an aqueous alkali Solution (e.g. 45 cobalt layer or a cobalt compound layer, Such as a cobalt aqueous Solution of Sodium hydroxide) with stirring, and hydroxide layer, cobalt monoxide layer or cobalt oxyhy Stirring the resulting mixture for a predetermined period droxide layer, on the Surface of the inner coat layer, followed while maintaining the pH at a practically constant level by by heat treatment in the presence of oxygen. Mere addition adding an aqueous alkali Solution dropwise each time there of the aqueous Sodium hydroxide Solution cannot attain is found a decrease in pH, to thereby cause deposition of the 50 formation of the coat layer comprising the Sodium hydroxide of yttrium, Scandium or the lanthanoid on the containing cobalt compound. Heat treatment in the presence Surface of the nickel hydroxide particle. of oxygen is essential. The heat treatment is preferably The inner coat layer comprising the hydroxide of yttrium, carried out at 50-200 C. When the heat treatment tempera Scandium or a lanthanoid can also be formed by the ture is below 50° C., CoHO showing a low conductivity is mechanical charging method which comprises dry blending 55 deposited in large amounts. On the other hand, when the heat a nickel hydroxide powder and the hydroxide, in powder treatment temperature exceeds 200 C., tricobalt tetraoxide form, of yttrium, Scandium or the lanthanoid in an inert gas (CoO), which is also low in conductivity, is deposited in using a compression attrition mill. When, in carrying out this increased amounts. When the cobalt compound layer is a mechanical charging method, yttrium, Scandium or a cobalt oxyhydroxide layer, heat treatment at below 50° C. lanthanoid, or the oxide, carbonate or fluoride thereof is 60 will not cause deposition of CoHO but makes the incorpo used, each in powder form, in lieu of the hydroxide, in ration of sodium difficult. The heat treatment time required powder form, of yttrium, Scandium or the lanthanoid, an depends on the quantity and concentration of the aqueous inner coat layer can be formed which comprises yttrium, Sodium hydroxide Solution used, the heat treatment tempera Scandium or the lanthanoid, or the oxide, carbonate or ture and other factors. Generally, however, said time is 0.5 fluoride thereof, respectively. 65 to 10 hours. The proportion of yttrium, Scandium or a lanthanoid in the AS typical examples of the Sodium-containing cobalt inner coat layer relative to the nickel hydroxide in the compound, there may be mentioned Sodium-containing 6,077.625 S 6 cobalt hydroxide, Sodium-containing cobalt oxyhydroxide there may be mentioned, for example, cobalt monoxide, and a mixture of these. The chemical structure of the cobalt hydroxide, cobalt oxyhydroxide and a Sodium Sodium-containing cobalt compound is not yet clearly containing cobalt compound. known to the present inventors. It is presumable, however, As a method of forming an inner coat layer comprising that this is not a simple mixture of a cobalt compound and cobalt hydroxide on the Substrate particle, there may be Sodium but might be a compound having a Special crystal mentioned, for example, the method comprising adding a Structure with Sodium incorporated in crystals of the cobalt nickel hydroxide powder to an aqueous Solution of a cobalt compound, Since it has a very high conductivity. The Sodium Salt (e.g. aqueous Solution of cobalt Sulfate), adjusting the content in the Sodium-containing cobalt compound is Suit pH to 9 to 12 (usually about 11) by adding dropwise an ably within the range of 0.1 to 10% by weight. When the aqueous alkali Solution (e.g. aqueous Solution of Sodium Sodium content is outside this range, the conductivity of the hydroxide) with stirring, and stirring the resulting mixture coat layer tends to decrease, and the active material utiliza for a predetermined period while maintaining the pH at a tion efficiency to decrease. practically constant level by adding an aqueous alkali Solu The proportion of the outer coat layer relative to the tion from time to time when a decrease in pH is found, to composite particle is preferably 3 to 15% by weight. When 15 thereby cause deposition of cobalt hydroxide on the Surface this proportion is below 3% by weight, the electron con of the Substrate particle. ductivity on the active material particle Surface becomes The inner coat layer comprising cobalt hydroxide can also insufficient, hence it becomes difficult to obtain a non be formed by the mechanical charging method which com Sintered nickel electrode with high active material utilization prises dry blending a nickel hydroxide powder and a cobalt efficiency. Then said proportion exceeds 15% by weight, the hydroxide powder in an inert gas using a compression packing density of the active material (nickel hydroxide) attrition mill. When, in carrying out this mechanical charg becomes Small and the Specific capacity of the electrode ing method, a cobalt monoxide powder or a cobalt powder becomes decreased. is used in lieu of the cobalt hydroxide powder, an inner coat layer can be formed which comprises the cobalt monoxide The electrode X of the invention, in which an active material powder composed of composite particles each 25 or cobalt, respectively. comprising a Substrate particle containing nickel hydroxide, An inner coat layer comprising cobalt oxyhydroxide can an inner coat layer comprising yttrium, Scandium or a be formed, for example, by forming a cobalt hydroxide layer lanthanoid, or an yttrium, Scandium or lanthanoid on the Surface of the Substrate particle and then oxidizing compound, which Suppresses the decrease in oxygen over Said cobalt hydroxide layer with an aqueous hydrogen Voltage on the occasion of high-temperature charging, and peroxide solution heated to about 40 C. An inner coat layer an Outer coat layer comprising cobalt or a cobalt compound, comprising a Sodium-containing cobalt compound can be which provides electron conductivity, shows Smaller reduc formed, for example, by adding an aqueous Sodium hydrox tions in active material utilization efficiency even when ide Solution to a powder composed of particles having a charging is conducted in a high-temperature atmosphere. cobalt layer or a cobalt compound layer, Such as a cobalt This is because the inner coat layer Suppresses the decrease 35 hydroxide layer, cobalt monoxide layer or cobalt oxyhy in oxygen overVoltage at the time of high-temperature droxide layer, on the Surface of the Substrate particle, charging and the charged electric energy is effectively followed by heat treatment in the presence of oxygen. Mere consumed in the charging reaction of the active material and, addition of the aqueous Sodium hydroxide Solution cannot at the same time, the electron conductivity of the active attain formation of the coat layer comprising the Sodium 40 containing cobalt compound. Heat treatment in the presence material particle Surface is increased by the outer coat layer. of oxygen is essential. The heat treatment is preferably In another aspect of the present invention, a non-sintered carried out at 50-200 C. When the heat treatment tempera nickel electrode for the alkaline storage battery (electrode Y ture is below 50° C., CoHO showing a low conductivity is of the invention) comprises an active material powder composed of composite particles each comprising a Sub deposited in large amounts. On the other hand, when the heat 45 treatment temperature exceeds 200 C., tricobalt tetraoxide Strate particle containing nickel hydroxide, an inner coat (CoO), which is also low in conductivity, is deposited in layer covering Said Substrate particle and comprising cobalt increased amounts. When the cobalt compound layer is a or a cobalt compound, and an outer coat layer covering Said cobalt oxyhydroxide layer, heat treatment at below 50° C. inner coat layer and comprising yttrium, Scandium or a will not cause deposition of CoHO but makes the incorpo lanthanoid, or an yttrium, Scandium or lanthanoid com 50 ration of sodium difficult. The heat treatment time required pound. depends on the quantity and concentration of the aqueous The active material of electrode Y of the invention com Sodium hydroxide Solution used, the heat treatment tempera prises composite particles each comprising a nickel ture and other factors. Generally, however, said time is 0.5 hydroxide-containing Substrate particle coated with two to 10 hours. layers, namely the inner and outer coat layerS defined above. 55 AS typical examples of the Sodium-containing cobalt The nickel hydroxide-containing Substrate particle compound, there may be mentioned Sodium-containing includes Single-component particles consisting of nickel cobalt hydroxide, Sodium-containing cobalt oxyhydroxide hydroxide alone, and Solid Solution particles derived from and a mixture of these. The chemical structure of the nickel hydroxide and at least one element Selected from Sodium-containing cobalt compound is not yet clearly among cobalt, Zinc, cadmium, calcium, manganese, 60 known to the present inventors. It is presumable, however, magnesium, bismuth, aluminum, lanthanoids and yttrium. that this is not a simple mixture of a cobalt compound and By forming Solid Solutions from nickel hydroxide and one or Sodium but might be a compound having a Special crystal more of the above-mentioned elements, the Swelling of Structure with Sodium incorporated in crystals of the cobalt non-sintered nickel electrodes at the time of charging can be compound, Since it has a very high conductivity. The Sodium Suppressed. 65 content in the Sodium-containing cobalt compound is Suit The inner coat layer covering the Substrate particle com ably within the range of 0.1 to 10% by weight. When the prises cobalt or a cobalt compound. AS the cobalt compound, Sodium content is outside this range, the conductivity of the 6,077.625 7 8 coat layer tends to decrease, and the active material utiliza comprising a Substrate particle containing nickel hydroxide, tion efficiency to decrease. an inner coat layer comprising cobalt or a cobalt compound, The proportion of the inner coat layer relative to the Sum which provides electron conductivity, and an outer layer total of the Substrate particle plus the inner coat layer is comprising yttrium, Scandium or a lanthanoid, or anyttrium, preferably 3 to 15% by weight. When this proportion is Scandium or lanthanoid compound, which Suppresses the below 3% by weight, the electron conductivity on the active decrease in oxygen overVoltage on the occasion of high material particle Surface becomes insufficient, hence it temperature charging, shows Smaller reductions in active becomes difficult to obtain a non-sintered nickel electrode material utilization efficiency even when charging is con with high active material utilization efficiency. When said ducted in a high-temperature atmosphere. This is because proportion exceeds 15% by weight, the packing density of the electron conductivity of the active material particle the active material (nickel hydroxide) becomes Small and the Surface is increased by the inner coat layer and the decrease Specific capacity of the electrode becomes decreased. in oxygen overVoltage at the time of high-temperature The outer coat layer covering the inner coat layer com charging is Suppressed owing to the outer coat layer and, at prises yttrium, Scandium or a lanthanoid, or an yttrium, Scandium or lanthanoid compound. The yttrium compound the same time, the charged electric energy is effectively includes yttrium hydroxide (Y(OH)), diyttrium trioxide 15 consumed in the charging reaction of the active material. (YO), yttrium carbonate (Y2(CO) and yttrium fluoride Meanwhile, the method disclosed in the above-cited pub (YF), among others. The Scandium or lanthanoid com lication Japanese Kokai Tokkyo Koho H05-28992 which pound includes hydroxides thereof (Sc(OH), LaCOH), comprises blending a nickel hydroxide powder with a pow Ce(OH), Pr(OH), Nd(OH), Pm(OH), Eu(OH), Gd(OH) der of metallic cobalt, cobalt hydroxide or an yttrium , Tb(OH), Dy(OH), Ho(OH), Er(OR), Tm(OH), etc.), compound cannot give Such non-sintered nickel electrodes oxides thereof (ScC), La O, CeO2, PrO, NdO, having excellent high-temperature charging characteristics Sm2O, Eu2O3, Gd2O3, TbO7, Dy2O3, Ho-Os, Er-Os, as electrodes X and Y of the present invention. This is Tm O, YbO, LuC), etc.), carbonates thereof (La(CO) because the electron conductivity providing effect of the , Ce(CO), Nd2(CO), Sma(CO), etc.), and fluorides metallic cobalt or cobalt hydroxide upon the nickel hydrox thereof (LaF, CeF, PrF, NdF, SmF, GdF., TbF, DyF, 25 ide particle Surface is lessened by the addition of the yttrium ErF, YbF, HoF., etc.). compound. A method for forming an Outer coat layer comprising the AS Suitable examples of the non-sintered nickel electrode hydroxide of yttrium, Scandium or a lanthanoid on the inner for the alkaline Storage battery as obtainable by applying the coat layer comprises, for example, adding a nickel hydrox present invention, there may be mentioned pasted nickel ide powder the particle Surface of which has been coated electrodes producible by applying a paste containing the with an inner coat layer, to an aqueous Solution of a Salt of active material to conductive core bodies, followed by yttrium, Scandium or a lanthanoid (e.g. aqueous Solution of drying. In that case, the conductive cores include, as typical yttrium Sulfate), adjusting the pH to 9 to 12 (generally about examples, foamed nickel, felt-like porous bodies made of 11) by adding dropwise an aqueous alkali Solution (e.g. metal fiber, and punching metals. The present invention can aqueous Solution of Sodium hydroxide) with stirring, and 35 also be Suitably applied to tubular nickel electrodes com Stirring the resulting mixture for a predetermined period prising the active material packed or filled in tubular metal while maintaining the pH at a practically constant level by conductors, pocket type nickel electrodes with the active material packed in pocket-shaped metal conductors, and adding an aqueous alkali Solution dropwise each time there nickel electrodes for button cells as producible by pressure is found a decrease in pH, to thereby cause deposition of the 40 hydroxide of yttrium, Scandium or the lanthanoid on the molding the active material together with gauze-like metal Surface of the nickel hydroxide particle. conductors, among others. The Outer coat layer comprising the hydroxide of yttrium, AS Suitable examples of the alkaline Storage battery in which electrode X or Y of the invention is used as the Scandium or a lanthanoid can also be formed by the positive electrode, there may be mentioned nickel-hydrogen mechanical charging method which comprises dry blending 45 the nickel hydroxide powder and the hydroxide, ir powder batteries (negative electrode: hydrogen-absorbing alloy form, of yttrium, Scandium or the lanthanoid in an inert gas electrode), nickel-cadmium batteries (negative electrode: using a compression attrition till. When, in carrying out this cadmium electrode) and nickel–zinc batteries (negative elec mechanical charging method, yttrium, Scandium or a trodes: Zinc electrode). lanthanoid, or the oxide, carbonate or fluoride thereof is 50 EXAMPLES used, each in powder form, in lieu of the hydroxide, in The following examples illustrate the present invention in powder form, of yttrium, Scandium or the lanthanoid, an further detail. They are, however, by no means limitative of outer coat layer can be formed which comprises yttrium, the Scope thereof. Various modifications may be made Scandium or the lanthanoid, or the oxide, carbonate or without departing from the Scope and Spirit of the invention. fluoride thereof, respectively. 55 Preliminary experiment The proportion of yttrium, Scandium or a lanthanoid in the A Sodium-containing cobalt compound was prepared by outer coat layer relative to the nickel hydroxide in the mixing cobalt hydroxide and a 25% (by weight) aqueous substrate particle is preferably 0.05 to 5% by weight. Then solution of sodium hydroxide in a weight ratio of 1:10 and this proportion is below 0.05% by weight, it is difficult to subjecting the mixture to heat treatment at 85 C. for 8 Satisfactorily Suppress the decrease in active material utili 60 hours, followed by washing with water and drying at 60° C. Zation efficiency as resulting from charging in a high The Sodium content in the thus-prepared Sodium-containing temperature atmosphere. When Said proportion exceeds 5% by weight, the packing density of the active material (nickel cobalt compound was determined by atomic absorption hydroxide) becomes low and the specific capacity (discharge analysis and was found to be 1% by weight. capacity) of the electrode decreases. 65 Example X-1 The electrode Y of the invention, in which an active An electrode X of the invention and an alkaline Storage material powder composed of composite particles each battery were produced by the following five-step procedure. 6,077.625 10 Step 1: A nickel hydroxide powder (mean particle size: 10 Solution), a metal can, a metal cell cover and So on. The size Alm) (100 g) was added to an aqueous Solution (1 liter) of the cadmium electrode was 85 mm (length)x40 mm containing 2.62 g of yttrium Sulfate. The pit of the liquid (width)x0.35 mm (thickness). For the purpose of investigat phase was adjusted to 11 by adding 1 M aqueous Sodium ing the characteristics of the non-sintered nickel electrode, hydroxide with Stirring and the reaction was allowed to the capacity of the negative electrode was made about 1.5 proceed for 1 hour while continuing stirring. The pH of the times that of the positive electrode. In the batteries fabri liquid phase was maintained at 11 by adequately adding 1 M cated in the Subsequent examples and comparative examples aqueous Sodium hydroxide at times when a certain decrease as well, the capacity of the negative electrode was about 1.5 in pH was found. In this case, pH monitoring was conducted times that of the positive electrode. using a glass electrode (pH meter) with an automatic tem perature compensation mechanism. Examples X-2 to X-17 Then, the precipitate was filtered off, washed with water Electrodes Xa2 to Xa 17 of the present invention and dried under vacuum to give a powder composed of (electrodes X of the invention) were produced and alkaline particles each comprising a nickel hydroxide particle storage batteries XA2 to XA17 were fabricated by proceed (Substrate particle) and an inner coat layer comprising 15 yttrium hydroxide as formed on the surface of the substrate ing in the same manner as in Example X-1 except that particle. The proportion of yttrium in the inner coat layer Scandium nitrate or a lanthanoid nitrate Specifically shown in relative to the nickel hydroxide in the Substrate particle was Table 1 was used in lieu of yttrium sulfate in step 1. determined by inductively coupled plasma atomic emission spectrometry and was found to be 1% by weight. TABLE 1. Step 2: The particulate powder obtained in step 1 (100 g) Nitrate of scandium or Amount of was added to an aqueous Solution (one liter) containing 13.1 Elect- lanthanoid used for forming nitrate used g of cobalt Sulfate. The pH of the liquid phase was adjusted rode the inner coat layer (g) to 11 by adding 1 M aqueous Sodium hydroxide with Stirring Xa2 Sc(NO) 4HO 13.75 and then the reaction was allowed to proceed for 1 hour with 25 Xa3 La(NO), 6HO 6.36 continued Stirring. Like in Step 1, the pH of the liquid phase Xa4 Ce(NO), 6HO 6.30 was maintained at 11 by adequately adding 1 M aqueous Xa5 Pr(NO), 6H.O 6.30 Xa6 Nd(NO), 6H.O 6.2O Sodium hydroxide at times when a certain decrease in pH Xa7 Pm(NO), 6HO 6.18 was found. Xa8 Sm(NO), 6HO 6.03 Then, the precipitate was filtered off, washed with water Xa Eu(NO), 6HO 5.99 Xa10 Gd(NO), 5HO 5.62 and dried under vacuum to give a powder composed of Xa11 Tb(NO), 5HO 5.82 particles each comprising the particle obtained in Step 1 and Xa12 Dy(NO), 5HO 5.51 a coat layer comprising cobalt hydroxide as formed on the Xa13 Ho(NO), 5HO 5.46 Surface of Said particle. Xa14 Er(NO), 5HO 5.41 35 Xa15 Tm(NO), 5HO 5.16 Step 3: The particulate powder obtained in Step 2 and a 25% Xa16 Yb(NO), 3HO 4.87 (by weight) aqueous Solution of Sodium hydroxide were Xa17 Lu(NO) 3H2O 4.84 mixed up in a weight ratio of 1:10, and the mixture was heat-treated at 85 C. for 8 hours, then washed with water and dried at 65 C. to give an active material powder composed of composite particles with an Outer coat layer 40 Comparative Example X-1 comprising a Sodium-containing cobalt compound as An electrode Xb for comparison was produced and a formed on the inner coat layer comprising yttrium hydrox battery XB for comparison was fabricated in the same ide. The content of Sodium in the outer coat layer was manner as in Example X-1 except that Step 1 was omitted. estimated to be 1% by weight based on the result of the preliminary experiment. The proportion of the Outer coat 45 Comparative Example X-2 layer relative to the composite particle was determined by determining the cobalt content by atomic absorption analysis A paste was prepared by kneading 100 parts by weight of and was found to be 5% by weight. nickel hydroxide, 7 parts by weight of metallic cobalt, 5 Step 4: A paste was prepared by kneading 100 parts by parts by weight of cobalt hydroxide, 3 parts by weight of weight of the active material powder (mean particle size: 10 50 diyttrium trioxide (mean particle size 1 um) and 20 parts by um) obtained in step 3 with 20 parts by weight of a 1% (by weight of a 1% (by weight) aqueous Solution of methyl weight) acqueous Solution of methyl cellulose as a binder. cellulose (as binder). This paste was packed into a porous This paste was packed into a porous conductive base plate conductive base plate made of foamed nickel (porosity 95%, consisting of foamed nickel (porosity 95%, mean pore size mean pore size 200 um), followed by drying and pressure 200 um), followed by drying and pressure molding, to give 55 molding, to give an electrode Xc for comparison. Then, a a non-sintered nickel electrode (electrode X of the battery XC for comparison was fabricated in the same invention) Xa1. The size of electrode Xa1 of the invention manner as in Example X-1 except that Said electrode Xc for was 70 mm (length)x40 mm (width)x0.70 mm (thickness). comparison was used in Step 5. The procedure employed in The non-sintered nickel electrodes produced in the Subse producing this battery is the one disclosed in Japanese Kokai quent examples all had the same size as mentioned above. 60 Tokkyo Koho H05-28992. Step 5: An AA-size alkaline Storage battery (battery capac ity: about 1,000 mAh) XA1 was fabricated using the elec Comparative Example X-3 trode Xa1 (positive electrode) produced in Step 4, a prior art An electrode Xd for comparison was produced and a pasted cadmium electrode (negative electrode) having a battery XD for comparison was fabricated in the same capacity 1.5 times that of the positive electrode, a nonwoven 65 manner as in Example X-1 except that StepS 2 and 3 were polyamide fabric (separator), a 30% (by weight) aqueous omitted and the Sodium-containing cobalt compound pre Solution of potassium hydroxide (alkaline electrolyte pared in the preliminary experiment was added to the 6,077.625 11 12 particulate powder prepared in Step 1 in an amount of 5 parts trium trioxide. The low active material utilization efficiency by weight per 100 parts by weight of nickel hydroxide in of electrode Xd for comparison at the time of charging at 25 Substrate particles. C. is presumably due to the fact that no outer coat layer was Active material utilization efficiency of each of the non formed and the Sodium-containing cobalt compound was Sintered nickel electrodes merely added, So that the electron conductivity of the nickel Each battery was Subjected to 10 charge/discharge cycles hydroxide particle Surface could not be increased effectively. each comprising 160% charging at 0.1 C at 25 C., followed Relationship between the proportion of yttrium in the inner coat layer relative to the nickel hydroxide in the Substrate by discharge until 1.0 V at 1 C at 25 C. The active material particle and the active material utilization efficiency at the utilization efficiency, for the 10th cycle, of the non-sintered time of high-temperature charging or the discharge capacity nickel electrode used in each battery was determined. Then, Non-sintered nickel electrodes Xe 1 to Xe7 were produced each battery was 160% charged at 0.1 C at 60° C. and and alkaline storage batteries XE1 to XE7 were fabricated in discharged until 1.0 V at 1 C at 25 C. and the active material the same manner as in Example X-1 except that, in Step 1, utilization efficiency following high-temperature atmo an aqueous Solution (1 liter) containing 0.079 g, 0.13g, 1.31 Sphere charging was determined. The active material utili g, 7.86 g., 13.1 g, 15.7g or 20.9 g of yttrium Sulfate was used Zation efficiency was calculated as follows: 15 in lieu of the aqueous Solution (1 liter) containing 2.62 g of yttrium sulfate. With each of non-sintered nickel electrodes Active material utilization efficiency (%)=discharge capacity Xe 1 to Xe7, the proportion of yttrium in the inner coat layer (mAh)famount of nickel hydroxide (g)x288 (mAh/g)x100 relative to the nickel hydroxide in the Substrate particle was The results thus obtained are shown in Table 2. In Table 2, determined by assaying yttrium by inductively coupled the active material utilization efficiency values are relative plasma atomic emission Spectrometry. AS shown in Table 3, indices with the active material utilization efficiency of the respective proportions were, in the order mentioned above, 0.03% by weight, 0.05% by weight, 0.5% by weight, electrode Xa1 of the invention being taken as 100. 3% by weight, 5% by weight, 6% by weight and 8% by TABLE 2 weight. 25 Active material TABLE 3 utilization Active material efficiency utilization Electrode Xe1 Xe2 Xe3 Xa1 Xe4 Xe5 Xe6 Xe7 at 10th cycle in efficiency Elect- Inner coat charge/discharge in charging Amount of O.O79 0.13 1.31 2.62 7.86 13.1 15.7 20.9 rode layer cycles at 25 C. at 60° C. yttrium Sulfate used Xa1 Y(OH), OO 68 (g) Xa2 Sc (OH), OO 65 Proportion O.O3 O.OS O.S 1. 3 5 6 8 Xa3 La (OH), OO 67 of yttrium Xa4 Ce (OH), 98 66 relative to nickel Xa5 Pr(OH), OO 67 35 Xa6 Nd (OH), OO 67 hydroxide Xa7 Pm (OH), 99 66 (% by weight) XaO Sm (OH), 99 67 Xa Eu (OH), OO 66 Xa10 Gd (OH), OO 66 Then, each battery was Subjected to the same charge/ Xa11 Tb (OH), 99 65 discharge test as mentioned above (10 cycles of charge and Xa12 Dy (OH), OO 67 40 discharge at 25 C., followed by one cycle of charge at 60 Xa13 Ho (OH), 99 67 Xa14 Er (OH), OO 68 C. and discharge at 25 C.) and the discharge capacity, for Xa15 Tm (OH), OO 67 the 10th charge/discharge at 25 C., of the non-sintered Xa16 Yb(OH), OO 66 nickel electrode used in each battery and the active material Xa17 Lu (OH) OO 65 utilization efficiency at the time of charging at 60° C. were Xb OO 60 45 determined. The respective results thus obtained are shown Xc 75 3O in FIG. 1 and FIG. 2. Xd 81 63 FIG. 1 is a graphic representation of the relationship between the proportion of yttrium in the inner coat layer As shown in Table 2, electrodes Xa1 to Xa17 of the relative to the nickel hydroxide in the Substrate particle and invention showed high active material utilization efficiency 50 the active material utilization efficiency at the time of in both cases of charging at 25 C. and charging at 60°C. On high-temperature charging, the ordinate denoting the active the contrary, electrode Xb for comparison showed lower material utilization efficiency at the time of charging at 60 active material utilization efficiency at the time of charging C. and the abscissa denoting the proportion (X by weight) of at 60 C. as compared with electrodes Xa1 to Xa 17 of the yttrium in the inner coat layer relative to the nickel hydrox invention although, at the time of charging at 25 C., it was 55 ide in the substrate particle. In FIG. 1, the active material comparable in active material utilization efficiency to elec utilization efficiency of electrode Xa1 of the invention at the trodes Xa1 to Xa 17 of the invention. This is presumably time of charging at 60° C. is also shown. The active material because the inner coat layer comprising yttrium hydroxide utilization efficiency data shown in FIG. 1 (ordinate) are was not formed on the surface of the nickel hydroxide relative indices with the active material utilization efficiency particle, hence the decrease in oxygen overVoltage at the 60 of electrode Xa1 of the invention at the time of charging at time of high-temperature charging was not Suppressed to a 60° C. being taken as 100. sufficient extent. The active material utilization efficiency of From FIG. 1, it is seen that, for obtaining a non-sintered electrode Xc for comparison at the time of charging at 25 nickel electrode showing high active material utilization C. and that at 60° C. were very low and this was presumably efficiency at the time of high-temperature charging, the due to the electron conductivity-providing effect resulting 65 proportion of yttrium in the inner coat layer relative to the from the addition of metallic cobalt and cobalt hydroxide nickel hydroxide in the substrate particle should preferably having been lessened by the Simultaneous addition of diyt be not less than 0.05% by weight. 6,077.625 13 14 FIG. 2 is a graphic representation of the relationship in the 10th cycle of charge/discharge at 25 C. and the between the proportion of yttrium in the inner coat layer abscissa denoting the proportion (% by weight) of the outer relative to the nickel hydroxide in the Substrate particle and coat layer relative to the composite particle. In FIG. 3, there the discharge capacity, the ordinate denoting the discharge is also shown the discharge capacity of electrode Xa1 of the capacity following charging at 25 C. in the 10th cycle and 5 invention following charging at 25 C. in the 10th cycle. The the abscissa denoting the proportion (% by weight) of discharge capacity data shown in FIG. 3 (ordinate) are yttrium in the inner coat layer relative to the nickel hydrox relative indices with the discharge capacity of electrode Xa1 ide in the substrate particle. In FIG. 2, there is also shown of the invention following charging at 25 C. in the 10th the discharge capacity of electrode Xa1 of the invention cycle being taken as 100. following charging at 25 C. in the 10th cycle. The discharge As seen from FIG. 3, it is preferred that, for obtaining a capacity data shown in FIG. 2 (ordinate) are relative indices non-sintered nickel electrode of great discharge capacity, the with the discharge capacity of electrode Xa1 of the invention following charging at 25 C. in the 10th cycle being taken proportion of the outer coat layer relative to the composite as 100. particle should be 3 to 15% by weight. From FIG. 2, it is seen that, for obtaining a non-sintered 15 Example Y-1 nickel electrode showing great discharge capacity, the pro An electrode Y of the invention was produced and an portion of yttrium in the inner coat layer relative to the alkaline Storage battery was fabricated by the following nickel hydroxide in the Substrate particle should preferably five-step procedure. be not more than 5% by weight. Step 1: A nickel hydroxide powder (100 g, mean particle size As seen from FIG. 1 and FIG. 2, it is preferred that the 10 um) was added to an aqueous Solution (1 liter) containing proportion of yttrium in the inner coat layer relative to the 13.1 g of cobalt sulfate, the pH of the liquid phase was nickel hydroxide in the Substrate particle should be 0.05 to adjusted to 11 by adding 1 M aqueous Sodium hydroxide 5% by weight. For scandium and lanthanoids, it has been with Stirring, and the reaction was then allowed to proceed Separately established that the proportions thereof in the for 1 hour with stirring. The pH of the liquid phase was inner coat layer relative to the nickel hydroxide in the 25 maintained at 11 by adequate addition of 1 M aqueous substrate particle should preferably be 0.05 to 5% by weight. Sodium hydroxide at times when a slight decrease in pH of Relationship between the proportion of the outer coat layer the liquid phase was observed. In that case, pH monitoring relative to the composite particle and the active material was performed using a glass electrode (pH meter) with an utilization efficiency at the time of high-temperature charg automatic temperature compensation mechanism. ing or the discharge capacity Then, the precipitate was collected by filtration, washed Non-sintered nickel electrodes Xf1 to Xf7 were produced with water and dried under vacuum to give a powder and alkaline storage batteries XF1 to XF7 were fabricated in composed of particles each comprising a nickel hydroxide the same manner as in Example X-1 except that, in Step 2, particle (Substrate particle) and a coat layer of cobalt an aqueous Solution (1 liter) containing 1.31 g, 5.25 g, 7.88 hydroxide as formed thereon. The proportion of cobalt g, 26.3.g., 39.4g, 44.7 g or 52.5g of cobalt Sulfate was used 35 hydroxide relative to the sum total of nickel hydroxide and in lieu of the aqueous Solution (1 liter) containing 13.1 g of cobalt hydroxide was determined by assaying cobalt by cobalt Sulfate. With each of non-sintered nickel electrodes atomic absorption analysis and was found to be 5% by Xf1 to Xf7, the proportion of the outer coat layer relative to weight. the composite particle was determined by assaying cobalt by Step 2: The particulate powder obtained in step 1 and a 25% atomic absorption analysis. AS shown in Table 4, Said 40 (by weight) aqueous Solution of Sodium hydroxide were proportion was 0.5% by weight, 2% by weight, 3% by mixed up in a weight ratio of 1:10, and the mixture was weight, 10% by weight, 15% by weight, 17% by weight or heat-treated at 85°C. for 8 hours, followed by washing with 20% by weight, in the same order as mentioned above. water and drying at 65 C., to give a powder composed of particles each having an inner coat layer of a Sodium TABLE 4 45 containing cobalt compound as formed on the Surface of the Substrate particle. The Sodium content in the Sodium Electrode Xf1 XF2 Xf3 Xa1 XF4 XFS Xf6 Xf7 containing compound was estimated to be 1% by weight Amount of 131 S.25 7.88 13.1 26.3 39.4 44.7 52.5 based on the result of the preliminary experiment mentioned cobalt Sulfate used hereinbefore. The proportion of the Sodium-containing (g) 50 cobalt compound (inner coat layer) relative to the Sum total Proportion 0.5 2 3 5 1O 15 17 2O of the nickel hydroxide and the Sodium-containing cobalt of the outer compound was determined by assaying cobalt by atomic coat layer relative to absorption analysis and was found to be about 5% by the weight. composite 55 Step 3: The particulate powder obtained in step 2 (100 g) particle was added to an aqueous Solution (1 liter) containing 2.62 g (% by weight) of yttrium Sulfate, the pH of the liquid phase was adjusted to 11 by adding 1 M aqueous sodium hydroxide with Then, each battery was Subjected to the same charge/ Stirring, and the reaction was allowed to proceed for 1 hour discharge test as mentioned above (10 cycles of charge and 60 with Stirring. The pH of the liquid phase was maintained at discharge at 25 C.), and the discharge capacity, for the 10th 11 by adequate addition of 1 M aqueous Sodium hydroxide charge/discharge at 25 C., of the non-sintered nickel elec at times when a Slight decrease in pH of the liquid phase was trode used in each battery was determined. The results thus observed, as in Step 1. obtained are shown in FIG. 3. FIG. 3 is a graphic represen Then, the precipitate was collected by filtration, washed tation of the relationship between the proportion of the outer 65 with water and dried under Vacuum to give an active coat layer relative to the composite particle and the dis material powder composed of composite particles each charge capacity, the ordinate denoting the discharge capacity comprising the particle obtained in Step 2 and an outer coat 6,077.625 15 16 layer of yttrium hydroxide as formed on the surface of said outer coat layer formed on the Surface thereof was produced particle. The proportion of yttrium in the outer coat layer by mixing 100 g of particulate powder obtained in Step 2 relative to the nickel hydroxide in the Substrate particle was with 2.04 of ytterbium (Yb), 2.32 g of diytterbium trioxide determined by assaying yttrium by inductively coupled (YbO), 2.71 g of ytterbium fluoride (YbF) or 3.10 g of plasma atomic emission spectrometry and was found to be ytterbium carbonate (Yb(CO)), each in powder form, by 1% by weight. the mechanical charge technique. Electrodes Ya18 to Ya21 Step 4: A paste was prepared by kneading 100 parts by (electrodes Y of the invention) were produced and alkaline weight of the active material powder obtained in Step 3 storage batteries YA18 to YA21 were fabricated in the same (mean particle size 10 um) and 20 parts by weight of a 1% manner as in StepS 4 and 5 of Example Y-1 except that the (by weight) acqueous Solution of methyl cellulose as a binder. active material powders obtained in the above manner were This paste was packed into a porous conductive base plate used. made of foamed nickel (porosity 95%, mean pore size 200um), followed by drying and press molding, to give a Example Y-22 non-sintered nickel electrode Ya1 (electrode Y of the Ytterbium nitrate (4.87 g) was dissolved in an aqueous invention). The size of electrode Ya1 of the invention was 70 15 solution (1,000 ml) containing 166.9 g of nickel sulfate. mm (length)x40 mm (width)x0.70 mm (thickness). The Following dropwise addition of aqueous ammonia, 1 M non-sintered nickel electrodes produced in the Subsequent aqueous Sodium hydroxide was added dropwise with Vig examples and comparative examples all had the same size as orous stirring, followed by Washing with water and drying, mentioned above. to give a powder composed of Solid Solution particles Step 5: An AA-size alkaline Storage battery (battery capac consisting of nickel hydroxide and ytterbium. An electrode ity: about 1,000 mAh) YA1 was fabricated using the elec Ya22 (electrode Y of the invention) was produced and an trode Ya1 (positive electrode) produced in Step 4, a prior art alkaline Storage battery YA22 was fabricated in the same pasted cadmium electrode (negative electrode) having a manner as in Example Y16 except that Said Solid Solution capacity 1.5 times that of the positive electrode, a nonwoven particle powder was used in lieu of the nickel hydroxide polyamide fabric (separator), a 30% (by weight) aqueous 25 Solution of potassium hydroxide (alkaline electrolyte powder. Solution), a metal can, a metal cell cover and So on. The size of the cadmium electrode was 85 mm (length)x40 mm Examples Y-23 to Y-26 (width)x0.35 mm (thickness). For the purpose of investigat Ytterbium nitrate (4.87 g) was dissolved in an aqueous ing the characteristics of the non-sintered nickel electrode, solution (1,000 ml) containing 166.9 g of nickel sulfate. the capacity of the negative electrode was made about 1.5 Following dropwise addition of aqueous ammonia, 1 M times that of the positive electrode. In the batteries fabri aqueous Sodium hydroxide was added dropwise with Vig cated in the Subsequent examples and comparative examples orous stirring, followed by Washing with water and drying, as well, the capacity of the negative electrode was about 1.5 to give a powder composed of Solid Solution particles times that of the positive electrode. 35 consisting of nickel hydroxide and ytterbium. Then, this solid solution particle powder was mixed with a 25% (by Examples Y-2 to Y-17 weight) aqueous Solution of Sodium hydroxide in a weight Electrodes Ya2 to Ya 17 of the present invention ratio of 1:10, and the mixture was heat-treated at 85 C. for (electrodes Y of the invention) were produced and alkaline 8 hours, followed by washing with water and drying at 65 storage batteries YA2 to YA17 were fabricated by proceed 40 C., to give a powder composed of particles each comprising ing in the same manner as in Example Y-1 except that the Solid Solution particle and an inner coat layer of a Scandium nitrate or a lanthanoid nitrate Specifically shown in Sodium-containing cobalt compound as formed on the Sur Table 5 was used in lieu of yttrium sulfate in step 3. face of Said particle. This particulate powder (100 g) was mixed with 2.04 g of ytterbium, 4.65 g of diytterbium TABLE 5 45 trioxide, 2.71 g of ytterbium fluoride or 3.10 g of ytterbium carbonate, each in powder form, by the mechanical charge Nitrate of scandium or Amount of Elect- lanthanoid used for forming nitrate used technique, to give an active material powder composed of rode the Outer coat layer (g) composite particles. Electrodes Ya23 to Ya26 (electrodes Y of the invention) were produced and alkaline Storage bat Ya2 Sc(NO), 4H2O 13.75 50 teries YA23 to YA26 were fabricated in the same manner as Ya3 La(NO), 6HO 6.36 Ya4 Ce(NO), 6HO 6.30 in steps 4 and 5 of Example Y-1 except that the active Ya5 Pr(NO), 6HO 6.30 material powders obtained in the above manner were used. Ya6 Nd(NO), 6H.O 6.2O Yaf Pm(NO), 6HO 6.18 Comparative Example Y-1 YaS Sm(NO), 6HO 6.03 YaS Eu(NO), 6HO 5.99 55 An electrode Yb for comparison was produced and a Ya10 Gd(NO), 5HO 5.62 Ya11 Tb(NO), 5HO 5.82 battery YB for comparison was fabricated in the same Ya12 Dy(NO), 5HO 5.51 manner as in Example Y-1 except that Step 3 was omitted. Ya13 Ho(NO), 5HO 5.46 Ya14 Er(NO), 5HO 5.41 Comparative Example Y-2 Ya15 Tm(NO), 5HO 5.16 60 Ya16 Yb(NO), 3HO 4.87 A paste was prepared by kneading 100 parts by weight of Ya17 Lu(NO) 3H2O 4.84 nickel hydroxide, 7 parts by weight of metallic cobalt, 5 parts by weight of cobalt hydroxide, 3 parts of diyttrium trioxide (mean particle size 1 um) and 20 parts by weight of Examples Y-18 to Y-21 65 a 1% (by weight) aqueous Solution of methyl cellulose as a An active material powders composed of composite par binder. This paste was packed into a porous base plate made ticles each comprising the particle obtained in Step 2 and an of foamed nickel (porosity 95%, mean pore size 200 um, 6,077.625 17 18 followed by drying and pressure molding, to give an elec trode Yc for comparison. Then, a battery for comparison YC TABLE 6 was fabricated in the Same manner as in Example Y-1 except Active material that said electrode Yc for comparison was used in step 5. The utilization Active material procedure for making this battery was as disclosed in efficiency utilization Japanese Kokai Tokkyo Koho H05-28992. at 10th cycle in efficiency Elect- Inner coat charge/discharge in charging Comparative Example Y-3 rode layer cycles at 25 C. at 60° C. Ya1 Y(OH), OO 70 An electrode Yd for comparison and a battery YD for Ya2 Sc (OH), OO 66 comparison were respectively produced in the same manner Ya3 La (OH) OO 67 as in Example Y-1 except that, in lieu of Step 3, yttrium Ya4 Ce (OH), 98 67 Ya5 Pr(OH), OO 66 hydroxide was added to the particulate powder obtained in Ya6 Nd (OH), OO 67 Step 2 in an amount of 1 part by weight, expressed as Yaf Pm (OH), 99 67 yttrium, relative to 100 parts by weight of the nickel 15 YaS Sm (OH), OO 66 YaS Eu (OH), OO 68 hydroxide in the powder obtained in Step 2. Ya10 Gd (OH), OO 68 Ya11 Tb (OH), 99 67 Comparative Example Y-4 Ya12 Dy (OH), OO 67 Ya13 Ho (OH), 99 66 An electrode Ye for comparison and a battery YE for Ya14 Er (OH), OO 67 Ya15 Tm (OH), OO 68 comparison were respectively produced in the same manner Ya16 Yb(OH), OO 68 as in Example Y-1 except that StepS 2 and 3 were omitted and Ya17 Lu (OH) 99 65 the particulate powder obtained in Step 1 itself was used as Ya18 Yb 99 66 the active material. The procedure for making this battery Ya19 YbO, OO 67 Ya2O YbF, 99 67 was as disclosed in Japanese Kokai Tokkyo Koho S62 25 Ya21 Yb2(CO) OO 65 234.867. Ya22 Yb(OH), OO 67 Ya23 Yb 99 67 Ya24 YbO, OO 68 Comparative Example Y-5 Ya25 YbF, OO 66 Ya26 Yb2(CO) 99 66 Ytterbium nitrate (4.87 g) was dissolved in an aqueous Yb OO 60 solution (1,000 ml) containing 166.9 g of nickel sulfate. Yc 75 3O Yd 92 61 Following dropwise addition of aqueous ammonia, 1 M Ye 74 27 aqueous Sodium hydroxide was added dropwise with Vig Yf 98 43 orous stirring, followed by Washing with water and drying, to give a powder composed of Solid Solution particles 35 consisting of nickel hydroxide and ytterbium. Then, this As shown in Table 6, electrodes Ya1 to Ya26 of the invention showed high active material utilization efficiency solid solution particle powder was mixed with a 25% (by in both cases of charging at 25 C. and charging at 60° C. weight) acqueous Solution of Sodium hydroxide in a weight Among then, electrode Ya1 of the invention showed the ratio of 1:10, and the mixture was heat-treated at 85 C. for highest active material utilization efficiency at the time of 8 hours, followed by washing with water and drying at 65 40 charging at 60° C., indicating that yttrium or an yttrium C., to give a powder composed of particles each comprising compound is most preferred as the material of the outer coat the Solid Solution particle and an inner coat layer of a layer. On the contrary, electrode Yb for comparison showed Sodium-containing cobalt compound as formed on the Sur lower active material utilization efficiency at the time of face of Said particle. An electrode Yf for comparison and a charging at 60° C. as compared with electrodes Ya1 to Ya26 battery YF for comparison were respectively produced in the 45 of the invention although, at the time of charging at 25 C., same manner as in Examples Y-23 to Y-26 except that said it was comparable in active material utilization efficiency to particulate powder was used as the active material powder. electrodes Ya1 to Ya26 of the invention. This is presumably Active material utilization efficiency of each of the non because the outer coat layer was not formed, hence the Sintered nickel electrodes decrease in oxygen overVoltage at the time of high Each battery was Subjected to 10 charge/discharge cycles 50 temperature charging was not Suppressed to a Sufficient each comprising 160% charging at 0.1 C at 25 C., followed extent. The active material utilization efficiency of electrode by discharge until 1.0 V at 1 C at 25 C. The active material Yc for comparison at the time of charging at 25 C. and that utilization efficiency, for the 10th cycle, of the non-sintered at 60° C. was very low and this was presumably due to the nickel electrode used in each battery was determined. Then, electron conductivity-providing effect resulting from the each battery was 160% charged at 0.1 C at 60° C. and 55 addition of metallic cobalt and cobalt hydroxide having been discharged until 1.0 V at 1 C at 25 C. and the active material lessened by the Simultaneous addition of diyttrium trioxide. utilization efficiency following high-temperature atmo The low active material utilization efficiency of electrode Yd Sphere charging was determined. The active material utili for comparison at the time of charging at 25 C. and at 60 Zation efficiency was calculated as follows: C. as compared with electrodes Ya1 to Ya21 is presumably 60 due to the fact that no outer coat layer was formed and the Active material utilization efficiency (%)=discharge capacity yttrium hydroxide was merely added, So that the oxygen (mAh)famount of nickel hydroxide (g)x288 (mAh/g)x100 Overvoltage at the time of charging could not be increased effectively. The markedly lower active material utilization The results thus obtained are shown in Table 6. In Table 6, efficiency of electrodes Ye and Yf for comparison at the time the active material utilization efficiency values are relative 65 of charging at 25 C. and at 60° C. as compared with indices with the active material utilization efficiency of electrodes Ya1 to Ya26 of the invention is presumably due to electrode Ya1 of the invention being taken as 100. the fact that no outer coat layer was formed, hence the 6,077.625 19 20 oxygen overVoltage at the time of charging was low and the particle and the active material utilization efficiency at the charged electric energy could not be effectively used in time of high-temperature charging or the discharge capacity charging the active material. Non-sintered nickel electrodes Ye1 to Ye7 and alkaline Relationship between the proportion of the inner coat layer storage batteries YE1 to YE7 were respectively produced in relative to the Sum total of the Substrate particle and inner the same manner as in Example Y-1 except that, in Step 3, coat layer and the active material utilization efficiency at the an aqueous Solution (1 liter) containing 0.079 g, 0.13g, 1.31 time of high-temperature charging or the discharge capacity g, 7.86 g., 13.1 g, 15.7g or 20.9 g of yttrium Sulfate was used Non-sintered nickel electrodes Yf1 to Yf7 and alkaline in lieu of the aqueous Solution (1 liter) containing 2.62 g of storage batteries YF1 to YF7 were respectively produced in yttrium Sulfate. For each of non-sintered nickel electrodes the same manner as in Example Y-1 except that, in Step 1, Ye1 to Ye7, the proportion of yttrium in the outer coat layer an aqueous Solution (1 liter) containing 1.31 g, 5.25 g, 7.88 relative to the nickel hydroxide in the Substrate particle was g, 26.3.g., 39.4g, 44.7 g or 52.5g of cobalt Sulfate was used determined by assaying yttrium by inductively coupled in lieu of the aqueous Solution (1 liter) containing 13.1 g of plasma atomic emission Spectrometry. AS shown in Table 8, cobalt Sulfate. For each of non-sintered nickel electrodes the respective proportions were, in the above-mentioned Yf1 to Yf7, the proportion of the inner coat layer relative to order, 0.03% by weight, 0.05% by weight, 0.5% by weight, the Sum total of the nickel hydroxide (Substrate particle) and 15 3% by weight, 5% by weight, 6% by weight and 8% by the inner coat layer was determined by assaying cobalt by weight. atomic absorption analysis. AS shown in Table 7, the respec tive proportions were found to be 0.5% by weight, 2% by TABLE 8 weight, 3% by weight, 10% by weight, 15% by weight, 17% by weight and 20% by weight in the above-mentioned order. Electrode Ye1 Ye Ye3 Ya1 Yea. Ye5 Ye6 Yef Amount of O.O79 0.13 1.31 2.62 7.86 13.1 15.7 20.9 TABLE 7 yttrium Sulfate used Electrode Yf1 Yf2 Yf Ya1 Yifa Yfs Yife Yf7 (g) Proportion O.O3 O.OS O.S 1. 3 5 6 8 Amount of 131 S.25 7.88 13.1 26.3 39.4 44.7 52.5 25 of yttrium cobalt relative to Sulfate used nickel (g) hydroxide Proportion 0.5 2. 3 5 1O 15 17 2O (% by weight) of the inner coat layer relative to Then, each battery was Subjected to the same charge/ the sum total of the discharge test as mentioned above (10 cycles of charge and composite discharge at 25 C., followed by one cycle of charge at 60 particle C. and discharge at 25 C.), and the active material utiliza and the inner 35 tion efficiency at the time of charging at 60° C. and the coat layer (% by weight) discharge capacity in the 10th charge/discharge cycle at 25 C. were determined for the non-sintered nickel electrode used in each battery. The respective results thus obtained are Then, each battery was Subjected to the same charge/ shown in FIG. 5 and FIG. 6. discharge test as mentioned above (10 cycles of charge and 40 FIG. 5 is a graphic representation of the relationship discharge at 25 C.), and the discharge capacity, for the 10th charge/discharge at 25 C., of the non-sintered nickel elec between the proportion of yttrium in the outer coat layer trode used in each battery was determined. The results thus relative to the nickel hydroxide in the Substrate particle and obtained are shown in FIG. 4. FIG. 4 is a graphic represen the active material utilization efficiency at the time of tation of the relationship between the proportion of the inner high-temperature charging, the ordinate denoting the active coat layer relative to the Sum total of the Substrate particle 45 material utilization efficiency at the time of charging at 60 and inner coat layer and the discharge capacity, the ordinate C. and the abscissa denoting the proportion (% by weight) denoting the discharge capacity in the 10th cycle of charge/ of yttrium in the outer coat layer relative to the nickel discharge at 25 C. and the abscissa denoting the proportion hydroxide in the Substrate particle. In FIG. 5, the active (% by weight) of the inner coat layer relative to the sum total material utilization efficiency of electrode Ya1 of the inven of the Substrate particle and inner coat layer. In FIG. 4, there 50 tion at the time of charging at 60° C. is also shown. The is also shown the discharge capacity of electrode Ya1 of the active material utilization efficiency data shown in FIG. 5 invention following charging at 25 C. in the 10th cycle. The (ordinate) are relative indices with the active material utili discharge capacity data shown in FIG. 1 (ordinate) are zation efficiency of electrode Ya1 of the invention in the 10th relative indices with the discharge capacity of electrode Ya1 cycle of charge/discharge at 25 C. being taken as 100. of the invention following charging at 25 C. in the 10th 55 From FIG. 5, it is seen that, for obtaining a non-sintered cycle being taken as 100. nickel electrode showing high active material utilization From FIG. 4, it is seen that, for obtaining a non-sintered efficiency at the time of high-temperature charging, the nickel electrode showing great discharge capacity, the pro proportion of yttrium in the Outer coat layer relative to the portion of the inner coat layer relative to Sum total of the nickel hydroxide in the substrate particle should preferably Substrate particle and inner coat layer should preferably be 60 be not less than 0.05% by weight. 3 to 15% by weight. It has been separately established that, FIG. 6 is a graphic representation of the relationship in cases where the Outer coat layer is mace of ytterbium between the proportion of yttrium in the outer coat layer hydroxide, the proportion of the inner coat layer relative to relative to the nickel hydroxide in the Substrate particle and the Sum total of the Substrate particle and inner coat layer the discharge capacity, the ordinate denoting the discharge should preferably be 3 to 15% by weight. 65 capacity following charging at 25 C. in the 10th cycle and Relationship between the proportion of yttrium in the outer the abscissa denoting the proportion (% by weight) of coat layer relative to the nickel hydroxide in the Substrate yttrium in the Outer coat layer relative to the nickel hydrox 6,077.625 21 22 ide in the substrate particle. In FIG. 6, there is also shown 7. An alkaline Storage battery which comprises, as a the discharge capacity of electrode Ya1 of the invention positive electrode, the non-sintered nickel electrode for an following charging at 25 C. in the 10th cycle. The discharge alkaline Storage battery according to any of claim 1. capacity ata shown in FIG. 6 (ordinate) are relative indices 8. The alkaline Storage battery according to claim 7, with the discharge capacity of electrode Ya1 of the invention wherein a negative electrode is a hydrogen-absorbing alloy following charging at 25 C. in the 10th cycle being taken electrode, a cadmium electrode or a Zinc electrode. as 100. 9. A non-sintered nickel electrode for an alkaline Storage From FIG. 6, it is seen that, for obtaining a non-sintered battery which comprises an active material powder consist nickel electrode showing great discharge capacity, the pro ing essentially of composite particles each composed of a portion of yttrium in the outer coat layer relative to the 1O Substrate particle containing nickel hydroxide, an inner coat nickel hydroxide in the Substrate particle should preferably layer covering Said Substrate particle and consisting essen be not more than 5% by weight. tially of cobalt or a cobalt compound, and an outer coat layer As seen from FIG. 5 and FIG. 6, it is preferred that the covering Said inner coat layer and comprising yttrium, proportion of yttrium in the Outer coat layer relative to the Scandium or a lanthanoid, or an yttrium, Scandium or nickel hydroxide in the Substrate particle should be 0.05 to 15 lanthanoid compound. 5% by weight. It has also been established separately that, in 10. The non-sintered nickel electrode for an alkaline forming the Outer coat layer using ytterbium hydroxide, too, Storage battery according to claim 9, wherein Said Substrate the proportion of ytterbium in the outer coat layer relative to particle is a Solid Solution particle composed of nickel the nickel hydroxide in the substrate particle should prefer hydroxide and at least one element Selected from among ably be 0.05 to 5% by weight. For scandium and cobalt, Zinc, cadmium, calcium, manganese, magnesium, lanthanoids, the same tendency was observed. bismuth, aluminum, lanthanoids and yttrium. While, in the above examples, Single-component particles 11. The non-sintered nickel electrode for an alkaline made of nickel hydroxide were used as SubStrate particles, it Storage battery according to claim 9, wherein Said cobalt has been Separately established that the same excellent compound is cobalt monoxide, cobalt hydroxide, cobalt effects as mentioned above can be obtained by using Solid 25 Oxyhydroxide or a Sodium-containing cobalt compound. Solution particles derived from nickel hydroxide and at least 12. The non-sintered nickel electrode for an alkaline one element Selected from among cobalt, Zinc, cadmium, Storage battery according to claim 9, wherein Said yttrium, calcium, manganese, magnesium, bismuth, aluminum, lan Scandium or lanthanoid compound is a hydroxide, oxide, thanoids and yttrium as Substrate particles. carbonate or fluoride. The present invention thus provides non-sintered nickel 13. The non-sintered nickel electrode for an alkaline electrodes for alkaline Storage batteries which can express Storage battery according to claim 9, wherein the proportion high active material utilization efficiency not only at the time of the yttrium, Scandium or lanthanoid in Said outer coat of charging at ordinary temperature but also at the time of layer relative to the nickel hydroxide in Said Substrate charging in a high-temperature atmosphere. particle is 0.05 to 5% by weight. What is claimed is: 35 14. The non-sintered nickel electrode for an alkaline 1. A non-sintered nickel electrode for an alkaline Storage Storage battery according to claim 9, wherein the proportion battery which comprises an active material powder consist of the inner coat layer relative to the Sum total of Said ing essentially of composite particles each composed of a substrate particle and said inner coat layer is 3 to 15% by Substrate particle containing nickel hydroxide, an inner coat weight. layer covering Said Substrate particle and comprising 40 15. A non-sintered nickel electrode for an alkaline Storage yttrium, Scandium or a lanthanoid, or an yttrium, Scandium battery which comprises an active material powder consist or lanthanoid compound, and an outer coat layer covering ing essentially of composite particles each composed of a Said inner coat layer and consisting essentially of cobalt or Substrate particle containing nickel hydroxide, an inner coat a cobalt compound. layer covering Said Substrate particle consisting essentially 2. The non-sintered nickel electrode for an alkaline Stor 45 of yttrium, Scandium or a lanthanoid, or an yttrium, Scan age battery according to claim 1, wherein Said Substrate dium or lanthanoid compound, and an Outer coat layer particle is a Solid Solution particle composed of nickel covering Said inner coat layer and consisting essentially of hydroxide and at least one element Selected from among cobalt or a cobalt compound. cobalt, Zinc, cadmium, calcium, manganese, magnesium, 16. The non-sintered nickel electrode for an alkaline bismuth, aluminum, lanthanoids and yttrium. 50 Storage battery according to claim 15, wherein the inner coat 3. The non-sintered nickel electrode for an alkaline stor layer consists of yttrium, Scandium or a lanthanoid, or an age battery according to claim 1, wherein Said yttrium, yttrium, Scandium or lanthanoid compound, wherein the Scandium or lanthanoid compound is a hydroxide, oxide, outer coat layer consists of cobalt or a cobalt compound, and carbonate or fluoride. wherein the inner coat layer and the Outer coat layer may 4. The non-sintered nickel electrode for an alkaline Stor 55 include impurities. age battery according to claim 1, wherein Said cobalt com 17. The non-sintered nickel electrode for an alkaline pound is cobalt monoxide, cobalt hydroxide, cobalt oxyhy Storage battery according to claim 16, wherein the cobalt droxide or a Sodium-containing cobalt compound. compound may contain Sodium and is Selected from the 5. The non-sintered nickel electrode for an alkaline stor group consisting of cobalt monoxide, cobalt hydroxide, age battery according to claim 1, wherein the proportion of 60 cobalt oxyhydroxide, CoHO, CoO and mixtures thereof. the yttrium, Scandium or lanthanoid in Said inner coat layer 18. The non-sintered nickel electrode for an alkaline relative to the nickel hydroxide in Said Substrate particle is Storage battery according to claim 17, 0.05 to 5% by weight. wherein the yttrium compound is Selected from the group 6. The non-sintered nickel electrode for an alkaline Stor consisting of yttrium hydroxide, diyttrium trioxide, age battery according to claim 1, *herein the proportion of 65 yttrium carbonate and yttrium fluoride, Said outer coat layer relative to Said composite particle is 3 wherein the Scandium compound is Selected from the to 15% by weight. group consisting of (Sc(OH), and Sc-O, and 6,077.625 23 24 wherein the lanthanoid compound is Selected from the 21. The non-sintered nickel electrode for an alkaline group consisting of La(OH), Ce(OH), Pr(OH), Storage battery according to claim 20, wherein the cobalt Nd(OH), Pm(OH), Eu(OH), Gd(OH), Tb(OH), compound may contain Sodium and is Selected from the Dy(OH), Ho(OH), Er(OH), Tm(OH), La-O, group consisting of cobalt monoxide, cobalt hydroxide, CeO2, PrO, Nd2O, SmO, Eu2O, Gd2O, TbO7, cobalt oxyhydroxide, CoHO, CoO and mixtures thereof. Dy2O3, Ho-Os, Er-Os, Tm2O3, Yb2O3, Lu Os, La (CO), Ce(CO), Nd(CO), Sma(CO), LaF, 22. The non-sintered nickel electrode for an alkaline CeF, Pr, NdF, SmR, GdF, TbF, DyFs, Erf, Storage battery according to claim 21, YbF, and HoF. wherein the yttrium compound is Selected from the group 19. A non-sintered nickel electrode for an alkaline Storage consisting of yttrium hydroxide, diyttrium trioxide, battery which comprises an active material powder consist yttrium carbonate and yttrium fluoride, ing essentially of composite particles each composed of a wherein the Scandium compound is Selected from the Substrate particle containing nickel hydroxide, an inner coat layer covering Said Substrate particle consisting essentially group consisting of (Sc(OH), and Sc-O, and of cobalt or a cobalt compound, and an outer coat layer 15 wherein the lanthanoid compound is Selected from the covering Said inner coat layer consisting essentially of group consisting of La(OH), Ce(OH), Pr(OH), yttrium, Scandium or a lanthanoid, or an yttrium, Scandium Nd(OH), Pm(OH), Eu(OH), Gd(OH), Tb(OH), or lanthanoid compound. Dy(OH), Ho(OH), Er(OH), Tm(OH), La-O, 20. The non-sintered nickel electrode for an alkaline CeO2, PrO, Nd2O, SmO, Eu2O, Gd2O, TbO7, Storage battery according to claim 19, wherein the inner coat Dy2O, HoO, Er-O, Tm-O, YbO, Lu O, La layer consists of cobalt or a cobalt compound, wherein the (CO3)3, Ce2(CO3)3, Nd2(CO3)3, Sma(CO3)3, LaFs, outer coat layer consists of yttrium, Scandium or a CeF, Pr, NdF, SmR, GdF, TbF, DyFs, Erf, lanthanoid, or an yttrium, Scandium or lanthanoid YbF, and HoF. compound, and wherein the inner coat layer and the outer coat layer may include impurities. k k k k k