United States Patent (19) 11 Patent Number: 6,077,625 Yano Et Al
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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 Aou e o e uo eZ 4n e i el eu e A oW U.S. Patent Jun. 20, 2000 Sheet 2 of 6 6,077.625 Co Co Cs C cC ed r on e o Ao ul.0 e A oedeo 961 eulos C U.S. Patent Jun. 20, 2000 Sheet 3 of 6 6,077.625 Co o Co Cs Co Co yarn CO QO r CN Co el o Ao u20, e A oedeo 961 euos O U.S. Patent Jun. 20, 2000 Sheet 5 of 6 6,077.625 8 Co Co oC) 09 OOI cal O09 he bu! 61 euo ul Aoue o e uo eZ in e el eu e A low 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.