JP2010182684A - Processing method of anode active material for nickel hydrogen battery, anode active material for nickel hydrogen battery, and nickel hydrogen battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve battery characteristics without damaging high-temperature life characteristics in a nickel hydrogen battery using hydrogen storage alloy as an anode active material. <P>SOLUTION: The anode active material for a nickel hydrogen battery is expressed in a general formula:Mm<SB>1-α</SB>T1<SB>α</SB>Ni<SB>x</SB>Al<SB>y</SB>Mn<SB>z</SB>Co<SB>β</SB>T2<SB>γ</SB>(in the formula, Mm is a mixture of light rare-earth elements, T1 is an element of at least one kind selected from a group consisting of Mg, Ca, Sr and Ba, T2 is an element of at least one kind selected from a group consisting of Sn, Cu, and Fe. 0.01≤α≤0.5, 2.5≤x≤4.5, 0.05≤y+z≤2.0, 0≤β≤0.6, 0≤γ≤0.6, and 5.6≤x+y+z+β+γ≤6.0). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a negative electrode active material used for a nickel metal hydride battery, and more particularly to an improvement in the composition of a hydrogen storage alloy powder which is a negative electrode active material.

  Nickel metal hydride batteries using a hydrogen storage alloy powder as a negative electrode active material are attracting attention as power sources for electric vehicles and the like because they have excellent output characteristics and high durability (lifetime characteristics and storage characteristics). In recent years, lithium ion secondary batteries are also entering this application. Therefore, it is necessary to further improve output characteristics and durability from the viewpoint of highlighting the advantages of nickel metal hydride batteries.

As the hydrogen storage alloy powder, a powder having a CaCu ₅ type crystal structure is mainly used. From the viewpoint of enhancing the durability, for example, among the AB ₅ type, Ni of MmNi ₅ (Mm is a mixture of rare earth elements). In many cases, a part of is replaced with Co, Mn, Al, Cu or the like. From the viewpoint of further increasing the capacity while enhancing the durability in this way, a part of the A site is replaced with a 2A group element such as Mg, Ca, Sr, etc., and a hydrogen storage amount (hereinafter referred to as PCT) in a predetermined pressure range. Attempts have been made to increase the capacity (referred to as Patent Document 1). In addition, attempts have been made to suppress deterioration of discharge characteristics by replacing part of Ni in MmNi ₅ with Mg (see Patent Document 2).

JP 2002-042802 A JP 2004-119271 A

  By using the techniques of Patent Documents 1 and 2, it became possible to increase the capacity and suppress the deterioration of the discharge characteristics, but it was found that the high-temperature life characteristics were not good. The present invention has been made to solve the above problems, and an object of the present invention is to improve battery characteristics in a nickel-metal hydride battery using a hydrogen storage alloy as a negative electrode active material without impairing high-temperature life characteristics.

In view of the problems described above, the negative electrode active material for a nickel-hydrogen battery of the present invention have the general formula _{Mm 1-α T1 α Ni x} Al y Mn z Co β T2 γ ( wherein, Mm is the mixture of light rare earth elements, T1 Is at least one element selected from the group consisting of Mg, Ca, Sr and Ba, T2 is at least one element selected from the group consisting of Sn, Cu and Fe, 0.05 ≦ α ≦ 0. 5, 2.5 ≦ x ≦ 4.5, 0.05 ≦ y + z ≦ 2.0, 0 ≦ β ≦ 0.6, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + β + γ ≦ 6.0) It is characterized by that.

  As a result of studies by the present inventors, the following findings have been obtained. First, as in Patent Document 1, when the amount of part of the A site replaced with the group 2A element is small, the hydrogen storage alloy powder deteriorates due to repeated charge and discharge at high temperatures. Secondly, when trying to prevent the elution of Mn by Mg added to the B site as in Patent Document 2, the substitution of Mg that is inherently stable at the A site is incomplete and unevenly distributed on the surface and grain boundaries. The hydrogen occlusion reaction through the Ni layer decreases, and the battery reaction becomes insufficient each time charging and discharging are repeated.

  By utilizing the above knowledge, a relatively large amount of 2A group element is replaced with the A site, and the A / B ratio (stoichiometry ratio) is made 5.6 or more and 6.0 or less, so that the hydrogen storage alloy powder It has been found that the flatness can be improved while lowering the equilibrium pressure at a high temperature, and the PCT capacity can be increased. The effect of the present invention is under intensive analysis, but by controlling the stoichiometric ratio (element ratio between A site and B site) while substituting the 2A group element with the A site, Amorphization with Ni is promoted, and a new grain boundary of the hydrogen storage alloy powder is formed. Through this grain boundary, hydrogen ions (protons) easily reach the Ni layer unevenly distributed on the surface of the hydrogen storage alloy. It is thought that it became.

  The negative electrode active material for nickel metal hydride batteries of the present invention has an improved composition of the core hydrogen storage alloy powder, and the novel grain boundary has high corrosion resistance and does not inhibit the hydrogen storage reaction. The discharge efficiency in the high temperature of the comprised nickel metal hydride battery can be improved, and the capacity | capacitance fall by repetition of charging / discharging can be prevented.

Schematic sectional view showing the negative electrode active material for nickel-metal hydride battery of the present invention

  The best mode for carrying out the present invention will be described below with reference to the drawings.

The first invention of the general formula _{Mm 1-α T1 α Ni x} Al y Mn z Co β T2 γ ( wherein, Mm is the mixture of light rare earth elements, T1 is selected from the group consisting of Mg, Ca, Sr and Ba At least one element selected, T2 is at least one element selected from the group consisting of Sn, Cu, and Fe, 0.05 ≦ α ≦ 0.5, 2.5 ≦ x ≦ 4.5, 0 0.05 ≦ y + z ≦ 2.0, 0 ≦ β ≦ 0.6, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + β + γ ≦ 6.0).

The second invention has the general formula _{La 1-α T1 α Ni x} Al y Mn z Co β T2 γ ( wherein, T1 is at least one element selected from the group consisting of Mg, Ca, Sr and Ba, T2 is at least one element selected from the group consisting of Sn, Cu, and Fe, 0.05 ≦ α ≦ 0.5, 2.5 ≦ x ≦ 4.5, 0.05 ≦ y + z ≦ 2.0 , 0 ≦ β ≦ 0.6, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + β + γ ≦ 6.0).

A third invention of the general formula _{La 1-α Mg α Ni x} Al y Mn z Fe 0.6-y Sn y ( wherein, 0.05 ≦ α ≦ 0.5,2.5 ≦ x ≦ 4. 5, 0.05 ≦ y + z ≦ 2.0, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + 0.6 ≦ 6.0).

Considering the description of the first to third inventions, the composition of the hydrogen storage alloy powder 1 suitable for the present invention is, for example, La _0.7 Mg _0.3 Ni _2.75 Co _0.5 Al _{0.05 , La 0.6 Mg 0.4 Ni 3.0 Mn} 1.1 Al 0.5 Fe 0.6, La 0.7 Mg 0.3 Ni 3.3 Mn 1.0 Al 0.9 Fe 0.1 Sn _0.3 , Mm _0.7 Mg _0.3 Ni _2.75 Co _0.5 Al _0.05 , Mm _0.6 Mg _0.4 Ni _3.0 Mn _1.1 Al _0.5 Fe _0.6 MmMg _0.3 Ni _3.3 Mn _1.0 Al _0.9 Fe _0.1 Sn _0.3 .

5th invention is the processing method of the negative electrode active material for nickel hydride batteries of Claims 1-3, Comprising: The negative electrode for nickel hydride batteries which has the process of stirring the negative electrode active material for nickel hydride batteries in the said alkaline aqueous solution The present invention relates to a method for treating an active material. More specifically, the processing apparatus for the negative electrode active material for nickel-metal hydride batteries of the present invention, as a processing apparatus for establishing the processing method of the fifth invention, mixes and / or agitates the hydrogen storage alloy powder and the alkaline aqueous solution. A first means, a second means for heating the mixture of the hydrogen storage alloy powder and the alkaline aqueous solution, a third means for controlling the temperature of the alkaline aqueous solution in the second means, and discharging the alkaline aqueous solution waste. Fourth means, fifth means for pressure-filtering the hydrogen storage alloy powder, and sixth means for introducing the stored alkaline aqueous solution into the first and / or fifth means are provided.

  In the sixth invention, the aqueous alkali solution is preferably sodium hydroxide and / or potassium hydroxide.

  In the seventh invention, it is preferable that the basic molar concentration of the aqueous potassium hydroxide solution is 3 to 20 mol / L, and the basic molar concentration of the aqueous sodium hydroxide solution is 10 to 20 mol / L.

  In the eighth invention, the treatment temperature in the above step is preferably 80 to 150 ° C.

  FIG. 1 is a schematic cross-sectional view showing a negative electrode active material for a nickel metal hydride battery of the present invention. In the hydrogen-absorbing alloy powder 1 of the present invention, a non-crystallized layer of Group 2A element and B-site Ni is interposed between the particles 3 to form a grain boundary 4. It is connected to the Ni layer 2 that is unevenly distributed on the surface of the storage alloy powder 1.

  By replacing a relatively large amount of group 2A element with the A site and further setting the B / A ratio (stoichiometric ratio) to 5.6 or more and 6.0 or less, the equilibrium pressure of the hydrogen storage alloy powder at high temperature can be reduced. The flatness can be improved while lowering, and the PCT capacity can be increased. Although the effects of the present invention are being intensively analyzed, by controlling the stoichiometric ratio while substituting the 2A group element with the A site, non-crystallisation of the 2A group element and Ni at the B site is promoted. This is because the grain boundary 4 of the hydrogen storage alloy powder 1 is newly formed, and the hydrogen ions (protons) easily reach the Ni layer 2 unevenly distributed on the surface of the hydrogen storage alloy powder 1 through the grain boundary 4. It is done.

  Here, when α is less than 0.05, it is difficult to increase the capacity, and when it exceeds 0.5, segregation of the T1 element becomes remarkable. Moreover, even if x is less than 2.5 or more than 4.5, the capacity reduction becomes remarkable. Subsequently, when y + z is less than 0.05, the hydrogen equilibrium pressure increases and the capacity decreases, and when it exceeds 2.0, when elution of Mn and Al into the electrolyte is excessive, a nickel metal hydride battery is constructed. High temperature life characteristics deteriorate. On the other hand, if β exceeds 0.6, the elution of Co into the electrolyte is excessive and the high temperature life characteristics deteriorate when a nickel metal hydride battery is constructed. Further, when γ exceeds 0.6, segregation of the T2 element occurs, oxidation and passivation occur, hydrogen storage / release is inhibited, and the capacity decreases. Finally, if x + y + z + β + γ is less than 5.6, the non-crystallisation of the 2A group element at the A site and Ni at the B site is not promoted, so that the discharge capacity cannot be increased sufficiently. The debate becomes excessive and the capacity drop becomes remarkable.

The method for forming the negative electrode active material for a nickel metal hydride battery of the present invention is not particularly limited. For example, plasma arc melting method, high-frequency melting (die casting) method, mechanical alloying method (mechanical alloy method), mechanical milling method, rapid solidification method (specifically, metal materials utilization dictionary (Industry Research Committee, 1999)) Roll spinning method, melt drag method, direct casting and rolling method, spinning in spinning solution, spray forming method, gas atomization method, wet spray method, splat method, rapid solidification strip pulverization method, gas spray splat method , Melt extraction method, spray forming method, rotating electrode method, and the like). The mechanical alloying method and the mechanical milling method are effective synthesis methods in that the size and crystal form of the hydrogen storage alloy powder can be easily controlled. In addition to using the rapid solidification method alone, it can be used in combination with a mechanical alloying method or the like. As a raw material, what mixed the component element simple substance of the hydrogen storage alloy which has the target structural ratio to the target structural ratio can be used.

  The light rare earth element contained in Mm specifically refers to La, Ce, Nd, Pr, and Sm. In general, La, which is the main component, is contained in the Mm by 10 wt% or more and 50 wt% or less.

  Here, the base molar concentration of the KOH aqueous solution is preferably 3 to 20 mol / L, and the basic molar concentration of the NaOH aqueous solution is preferably 10 to 20 mol / L. When the base molar concentration of KOH is less than 3 mol / L, the surface treatment does not proceed as expected, and when it exceeds 20 mol / L, KOH is partially precipitated at the solution itself even at room temperature, and the productivity is remarkably increased. The process is not reproducible. In addition, when the base molar concentration of the NaOH aqueous solution is less than 10 mol / L, the removal of re-precipitate does not proceed, so that the surface treatment ability is reduced. When it exceeds 20 mol / L, even at room temperature, the solution itself is partially Precipitation of NaOH occurs and productivity is remarkably lowered, and process reproducibility is lost.

  Furthermore, it is preferable that the process temperature in the said process is 80-150 degreeC. When the temperature is lower than 80 ° C., a desired reaction is less likely to occur, and in the region exceeding 150 ° C., the KOH aqueous solution and the NaOH aqueous solution are close to the boiling point regardless of the concentration, and thus problems such as bumping are likely to occur. Considering the material and structure of the surface treatment equipment, the practical optimum range is 80 to 120 ° C.

  4th invention and 9th invention are related with the nickel hydride battery using the negative electrode containing the negative electrode active material for nickel hydride batteries described in the 1st-3rd and 5-8th invention. The detailed configuration of the nickel metal hydride battery of the present invention will be described below.

  First, a known positive electrode using nickel hydroxide as an active material can be used for the positive electrode.

  In addition, a conductive agent, a thickener, and a binder can be added separately to the negative electrode including the negative electrode active material for a nickel metal hydride battery of the present invention.

  As the conductive agent, any material having electronic conductivity can be selected without limitation. For example, natural graphite (such as flake graphite), artificial graphite, graphite such as expanded graphite, acetylene black (hereinafter abbreviated as AB), ketjen Carbon blacks such as black, channel black, furnace black, lamp black and thermal black, conductive fibers such as carbon fiber and metal fiber, metal powders such as copper, organic conductive materials such as polyphenylene derivatives, etc. Among them, artificial graphite, ketjen black, and carbon fiber are more preferable. These conductive agents may be used as a mixture of two or more kinds, and may be coated on the surface of the negative electrode active material for a nickel metal hydride battery of the present invention. Although the addition amount of the said electrically conductive agent is not specifically limited, The range of 0.1-50 weight part is preferable with respect to 100 weight part of negative electrode active materials for nickel hydride batteries, and the range of 0.1-30 weight part is more preferable.

  As the thickener, a material capable of imparting viscosity to the mixture paste, which is a precursor of the negative electrode, can be selected without limitation. For example, carboxymethylcellulose (hereinafter abbreviated as CMC) and modified products thereof, polyvinyl alcohol, methylcellulose, polyethylene oxide Is preferred.

As the binder, a material capable of binding the negative electrode mixture to the core material can be selected without limitation. For example, any of a thermoplastic resin and a thermosetting resin may be used. Styrene-butadiene copolymer rubber (hereinafter abbreviated as SBR), polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoro Ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer , Ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chloroto Fluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid copolymer Polymer Na ⁺ ion crosslinked body, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid copolymer Na ⁺ ion crosslinked body, ethylene-methyl acrylate copolymer, ethylene-methyl acrylate copolymer Na ⁺ ion crosslinked Body, ethylene-methyl methacrylate copolymer, ethylene-methyl methacrylate copolymer Na ⁺ ion cross-linked body, etc. can be used alone or in combination.

  As the separator, a nonwoven fabric made of polyolefin such as polypropylene can be used.

  As the electrolytic solution, a solution obtained by dissolving sodium hydroxide or lithium hydroxide in a potassium hydroxide aqueous solution having a specific gravity of around 1.30 can be used.

  The nickel metal hydride battery of the present invention can be configured by combining the above components.

  Hereinafter, the present invention will be specifically described based on examples, but the examples do not limit the present invention.

(I) Preparation of hydrogen storage alloy powder (1) Preparation of hydrogen storage alloy powders of Examples 1 to 18, 52 to 54 and Comparative Examples 1 to 10, 28, and 29 Metallic Mm, Ni, Mn, Co, A mixture of Al, Mg, and Fe in a predetermined ratio is melted at 1480 ° C. using a high-frequency melting furnace, and the melt is rapidly cooled by a roll quenching method and solidified, whereby the general formula is Mm _{1-α mg α Ni x Al y Mn z} Co β Fe γ (α, β, γ, x, y and z are listed in Table 1) was prepared an ingot of hydrogen-absorbing alloy is. The ingot was heated in an argon atmosphere at 800 ° C. for 5 hours and then pulverized to an average particle size of 30 μm.

(2) Preparation of hydrogen storage alloy powders of Examples 19 to 36, 55 to 57, and Comparative Examples 11 to 20, 30, and 31 Metal, La, Ni, Mn, Co, Al, Mg, and Fe in a predetermined ratio the in a mixture, and dissolved in 1480 ° C. using a high frequency melting furnace, and the melt was quenched by a roll quenching method, by solidifying the general formula _{La 1-α Mg α Ni x} Al y Mn z Co An ingot of a hydrogen storage alloy having _β Fe _γ (α, β, γ, x, y, and z are described in (Table 2)) was prepared. The ingot was heated in an argon atmosphere at 800 ° C. for 5 hours and then pulverized to an average particle size of 30 μm.

(3) Preparation of hydrogen storage alloy powders of Examples 37 to 51, 58 to 60, and Comparative Examples 21 to 27, 32, and 33 Metal, La, Ni, Mn, Al, Mg, Fe, and Sn in a predetermined ratio , And the mixture is melted at 1480 ° C. using a high-frequency melting furnace, and the melt is quenched by a roll quenching method.
By solidifying the general formula _{La 1-α Mg α Ni x} Al y Mn z Fe 0.6-γ Sn γ (α, γ, x, y and z (in Table 3)) is a hydrogen-absorbing An alloy ingot was prepared. The ingot was heated in an argon atmosphere at 800 ° C. for 5 hours and then pulverized to an average particle size of 30 μm.

(Ii) PCT capacity In order to measure the hydrogen storage amount of the hydrogen storage alloy powder, PCT measurement was performed. Using a PCT device manufactured by Resuka Co., Ltd., hydrogen was occluded at 45 ° C. until reaching 3 MPa, and then released until reaching 0.007 MPa. The PCT capacity was calculated from the amount of hydrogen from 0.01 MPa to 0.5 MPa using the obtained pressure-composition isotherm on the discharge side.

(Iii) Dissolution test In order to evaluate the durability of the hydrogen storage alloy powder in a nickel metal hydride battery, an alkali dissolution test of the hydrogen storage alloy was performed. 1 g of the hydrogen storage alloy powder described above was immersed in 100 ml of 48% by weight NaOH aqueous solution and kept at a constant temperature of 80 ° C. for 8 hours, and the constituent elements of the hydrogen storage alloy powder were eluted in this aqueous solution. The aqueous solution was analyzed by ICP analysis (Induced Couple
Analysis by Plasma Spectroscopy (Inductively Coupled Plasma Spectroscopy), and the concentration of each detected element was recorded.

(Iv) Production of negative electrode 0.15 parts by weight of CMC (degree of etherification 0.7, degree of polymerization 1600), 0.3 parts by weight of AB and 0 with respect to 100 parts by weight of the negative electrode active material for nickel metal hydride battery described above 0.7 parts by weight of SBR was added, and water was further added and kneaded to obtain a mixture paste. This mixture paste was applied to both surfaces of a core material made of nickel-plated iron punching metal (thickness 60 μm, hole diameter 1 mm, hole area ratio 42%). After drying the mixture paste layer, it was pressed and cut with a roller together with the core material to obtain a negative electrode having a thickness of 0.4 mm, a width of 35 mm, and a capacity of 2200 mAh. In addition, the exposed part of the core material was provided in the one end part along the longitudinal direction of a negative electrode.

(V) Production of Nickel Metal Hydride Battery Using a sintered nickel positive electrode with a capacity of 1500 mAh having an exposed portion of a core material with a width of 35 mm at one end along the longitudinal direction, a nickel metal hydride battery with a nominal capacity of 1500 mAh in a 4/5 A size is produced. did. Specifically, the positive electrode and the negative electrode were wound through a separator (thickness: 100 μm) made of a sulfonated polypropylene nonwoven fabric to produce a cylindrical electrode plate group. In the electrode plate group, the exposed portion of the positive electrode core material that does not carry the positive electrode mixture and the exposed portion of the negative electrode core material that does not carry the negative electrode mixture were exposed on the opposite end surfaces. A positive electrode current collector plate was welded to the end face of the electrode plate group from which the positive electrode core material was exposed. While the negative electrode current collector plate was welded to the end face of the electrode plate group where the negative electrode core material was exposed, the sealing plate and the positive electrode current collector plate were made conductive through the positive electrode lead. The electrode plate group was accommodated in a battery case made of a cylindrical bottomed can with the negative electrode current collector plate facing downward, and the negative electrode lead connected to the negative electrode current collector plate was welded to the bottom of the battery case. Furthermore, after injecting an electrolytic solution in which lithium hydroxide was dissolved at a concentration of 40 g / L into a potassium hydroxide aqueous solution having a specific gravity of 1.3, the opening of the battery case was sealed with a sealing plate having a gasket on the periphery, A nickel metal hydride battery was produced.

(Vi) High-temperature life characteristics The nickel-metal hydride storage batteries of each Example and Comparative Example were charged for 15 hours at a 10 hour rate (150 mA) in a 40 ° C. environment, and the battery voltage was 1.0 V at a 5 hour rate (300 mA). Discharged until This charge / discharge cycle was repeated 100 times. The ratio of the discharge capacity at the 100th cycle to the discharge capacity at the second cycle was determined as a percentage as the capacity retention rate.

  The composition ratios and evaluation results of the hydrogen storage alloy powders of Examples 1 to 18 and Comparative Examples 1 to 10 are shown in (Table 1).

  In Comparative Example 1 in which α is less than 0.05, the effect of adding Mg is excessively low, so the capacity is low and the capacity retention rate is also low. On the other hand, in Comparative Example 2 in which α exceeds 0.5, the segregation of Mg becomes remarkable, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of α is 0.05 or more and 0.5 or less.

In Comparative Example 3 in which x is less than 2.5, the capacity is low due to the decrease in the activity of the hydrogen storage alloy, and the capacity retention rate is also low. On the other hand, in Comparative Example 4 where x exceeds 4.5, the details are unclear, but since the amount of Ni is excessive and dumbbell-type atom pairs are formed in the CaCu ₅ type crystal structure, distortion occurs. As a result, the capacity may have decreased and the capacity maintenance rate may have decreased. From the above results, the appropriate range of x is 2.5 or more and 4.5 or less.

  In Comparative Example 5 where y + z is less than 0.05, the capacity is low due to the increase in the hydrogen equilibrium pressure, and the capacity retention rate is also low. On the other hand, in Comparative Example 6 in which y + z exceeds 2.0, elution of Mn and Al into the electrolyte was excessive, and the high temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less.

  In Comparative Example 7 in which β exceeded 0.6, the dissolution of Co into the electrolyte was excessive, and the high-temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of β is 0.6 or less.

  In Comparative Example 8 in which γ exceeds 0.6, the segregation of Fe occurs, oxidation and passivation occur, and hydrogen storage / release is inhibited, so the capacity is low. From the above results, the appropriate range of γ is 0.6 or less.

In Comparative Example 9 in which x + y + z + β + γ is less than 5.6, since the non-crystallization of the Group 2A element at the A site and Ni at the B site is not promoted, the capacity is low and the capacity retention rate is also low. On the other hand, x + y +
In Comparative Example 10 in which z + β + γ exceeds 6.0, non-stoichiometry becomes excessive, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of x + y + z + β + γ is 5.6 or more and 6.0 or less.

  The composition ratios and evaluation results of the hydrogen storage alloy powders of Examples 19 to 36 and Comparative Examples 11 to 20 are shown in (Table 2).

  In Comparative Example 11 in which α is less than 0.05, the effect of adding Mg is excessively low, so the capacity is low and the capacity retention rate is also low. On the other hand, in Comparative Example 12 in which α exceeds 0.5, the segregation of Mg becomes remarkable, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of α is 0.05 or more and 0.5 or less.

In Comparative Example 13 in which x is less than 2.5, the capacity is low due to the decrease in the activity of the hydrogen storage alloy, and the capacity retention rate is also low. On the other hand, in Comparative Example 14 where x exceeds 4.5, the details are unclear, but distortion occurred because the amount of Ni was excessive and dumbbell-type atom pairs were formed in the CaCu ₅ type crystal structure. As a result, the capacity may have decreased and the capacity maintenance rate may have decreased. From the above results, the appropriate range of x is 2.5 or more and 4.5 or less.

  In Comparative Example 15 where y + z is less than 0.05, the capacity is low due to the increase in hydrogen equilibrium pressure, and the capacity retention rate is also low. On the other hand, in Comparative Example 16 in which y + z exceeds 2.0, elution of Mn and Al into the electrolyte was excessive, and the high-temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less.

  In Comparative Example 17 in which β exceeded 0.6, the dissolution of Co into the electrolyte was excessive, and the high-temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of β is 0.6 or less.

  In Comparative Example 18 in which γ exceeds 0.6, Fe segregation occurs, oxidation and passivation occur, and hydrogen storage / release is inhibited, so the capacity is low. From the above results, the appropriate range of γ is 0.6 or less.

  In Comparative Example 19 in which x + y + z + β + γ is less than 5.6, the non-crystallization of the Group 2A element at the A site and Ni at the B site is not promoted, so the capacity is low and the capacity retention rate is also low. On the other hand, in Comparative Example 20 in which x + y + z + β + γ exceeds 6.0, non-stoichiometry becomes excessive, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of x + y + z + β + γ is 5.6 or more and 6.0 or less.

  The composition ratios and evaluation results of the hydrogen storage alloy powders of Examples 37 to 51 and Comparative Examples 21 to 27 are shown in (Table 3).

  In Comparative Example 21 in which α is less than 0.05, the effect of adding Mg is excessively low, so the capacity is low and the capacity retention rate is also low. On the other hand, in Comparative Example 22 in which α exceeds 0.5, the segregation of Mg becomes remarkable, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of α is 0.05 or more and 0.5 or less.

In Comparative Example 23 in which x is less than 2.5, the capacity is low due to the decrease in the activity of the hydrogen storage alloy, and the capacity retention rate is also low. On the other hand, in Comparative Example 24 where x exceeds 4.5, the details are unclear, but distortion occurred because the amount of Ni was excessive and dumbbell-type atom pairs were formed in the CaCu ₅ type crystal structure. As a result, the capacity may have decreased and the capacity maintenance rate may have decreased. From the above results, the appropriate range of x is 2.5 or more and 4.5 or less.

  In Comparative Example 25 where y + z is less than 0.05, the capacity is low due to the increase in the hydrogen equilibrium pressure, and the capacity retention rate is also low. On the other hand, in Comparative Example 26 in which y + z exceeded 2.0, the elution of Mn and Al into the electrolyte was excessive, and the high temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less.

  When γ exceeds 0.6, Sn segregation occurs, oxidation and passivation occur, and hydrogen storage / release is inhibited, so the capacity may be lowered. From the above results, the appropriate range of γ is 0.6 or less.

  In Comparative Example 27 in which x + y + z + 0.6 is less than 5.6, non-crystallization of the Group 2A element at the A site and Ni at the B site is not promoted, so the capacity is low and the capacity retention rate is also low. On the other hand, in Comparative Example 28 in which x + y + z + 0.6 exceeds 6.0, non-stoichiometry becomes excessive, the capacity is low, and the capacity retention rate is also low. From the above results, the appropriate range of x + y + z + 0.6 is 5.6 or more and 6.0 or less.

(I) Alkaline aqueous solution treatment In the preparation of the hydrogen storage alloy powders of Examples 10 to 12, 28 to 30, 46 to 48 and Comparative Examples 6 to 7, 16 to 17, and 26 to 27, The treatment with an aqueous alkali solution was performed.

  The base molar concentration of the KOH aqueous solution was 18 mol / L, and the treatment was performed at a treatment temperature of 100 ° C. for a treatment time of 30 minutes. The treated powder was subjected to dealkalization in a water washing step to obtain a dehydrated powder having a water content of 3.5%.

  Thereafter, the production of the negative electrode and the production of the nickel metal hydride battery were performed in the same manner as in Examples 1 to 51, and the high-temperature life characteristics were evaluated. This was designated as Examples 52 to 60.

  The composition ratios and evaluation results of the hydrogen storage alloy powders of Examples 52 to 60 and Comparative Examples 28 to 33 are shown in (Table 4).

In the case of the general formula Mm _1-α T1 _α Ni _x Al _y Mn _z Co _β T2 _γ , Comparative Example 29 in which y + z exceeds 2.0 is excessive elution of Mn and Al into the electrolyte solution. When configured, the high temperature life characteristics deteriorated. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less. On the other hand, in Comparative Example 30 in which β exceeds 0.6, the elution of Co into the electrolyte was excessive, and the high-temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of β is 0.6 or less. By carrying out the alkali treatment, the appropriate range of the composition is the same as in Examples 1-18. Furthermore, the hydrogen storage alloy that has been subjected to the alkali treatment has a higher PCT capacity and a higher capacity retention rate. Although the details are unknown, there is a possibility that a hydrogen catalyst active layer of the extreme surface layer is formed. In any case, the alkali treatment is more preferable.

If the formula is _{La 1-α Mg α Ni x} Al y Mn z Co β Fe γ, Comparative Example 31 in which y + z is greater than 2.0 is excessive elution of the electrolytic solution of Mn and Al, NiMH batteries When it was constructed, the high-temperature life characteristics deteriorated. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less. On the other hand, in Comparative Example 32 in which β exceeds 0.6, the dissolution of Co into the electrolyte was excessive, and the high-temperature life characteristics deteriorated when a nickel metal hydride battery was constructed. From the above results, the appropriate range of β is 0.6 or less. By carrying out the alkali treatment, the appropriate range of the composition is the same as in Examples 19 to 36. Furthermore, the hydrogen storage alloy that has been subjected to the alkali treatment has a higher PCT capacity and a higher capacity retention rate. Although the details are unknown, there is a possibility that a hydrogen catalyst active layer of the extreme surface layer is formed. In any case, the alkali treatment is more preferable.

In the case of the general formula La _1-α Mg _α Ni _x Al _y Mn _z Fe _0.6-y Sn _y , Comparative Example 33 in which y + z exceeds 2.0 has excessive elution of Mn and Al into the electrolyte solution, When a nickel metal hydride battery was constructed, the high temperature life characteristics deteriorated. From the above results, the appropriate range of y + z is 0.05 or more and 2.0 or less.

  On the other hand, Comparative Example 34 in which x + y + z + 0.6 is less than 5.6 does not promote non-crystallization of the 2A group element at the A site and Ni at the B site, so the capacity is low and the capacity retention rate is also low. From the above results, the appropriate range of x + y + z + 0.6 is 5.6 or more and 6.0 or less. By carrying out the alkali treatment, the appropriate range of the composition is the same as in Examples 37-51. Furthermore, the hydrogen storage alloy that has been subjected to the alkali treatment has a higher PCT capacity and a higher capacity retention rate. Although the details are unknown, there is a possibility that a hydrogen catalyst active layer of the extreme surface layer is formed. In any case, the alkali treatment is more preferable.

  By utilizing the present invention, it is possible to increase the capacity while greatly improving the high-temperature life characteristics of the nickel-metal hydride battery, so that it can be used as a power source for all devices and is used in harsh environments It can be expected to bring about a great effect in the field of power sources for automobiles.

1 Hydrogen storage alloy powder 2 Ni layer 3 Particles 4 Grain boundary

Claims (8)

In the formula _{Mm 1-α T1 α Ni x} Al y Mn z Co β T2 γ ( wherein, Mm is the mixture of light rare earth elements, T1 is Mg, Ca, at least one selected from the group consisting of Sr and Ba Element, T2 is at least one element selected from the group consisting of Sn, Cu, and Fe, 0.05 ≦ α ≦ 0.5, 2.5 ≦ x ≦ 4.5, 0.05 ≦ y + z ≦ 2 0.0, 0 ≦ β ≦ 0.6, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + β + γ ≦ 6.0), the treatment of the negative electrode active material for nickel metal hydride batteries A method,
The processing method of the negative electrode active material for nickel hydride batteries which has the process of stirring the negative electrode active material for nickel hydride batteries in alkaline aqueous solution. Formula _{La 1-α T1 α Ni x} Al y Mn z Co β T2 γ ( wherein, at least one element T1 is selected from the group consisting of Mg, Ca, Sr and Ba, T2 is Sn, Cu, And at least one element selected from the group consisting of Fe, 0.05 ≦ α ≦ 0.5, 2.5 ≦ x ≦ 4.5, 0.05 ≦ y + z ≦ 2.0, 0 ≦ β ≦ 0 .6, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + β + γ ≦ 6.0), a method for treating a negative electrode active material for nickel metal hydride batteries of a negative electrode active material for nickel metal hydride batteries,
The processing method of the negative electrode active material for nickel hydride batteries which has the process of stirring the negative electrode active material for nickel hydride batteries in alkaline aqueous solution. Formula _{La 1-α Mg α Ni x} Al y Mn z Fe 0.6-γ Sn γ ( wherein, 0.05 ≦ α ≦ 0.5,2.5 ≦ x ≦ 4.5,0.05 ≦ y + z ≦ 2.0, 0 ≦ γ ≦ 0.6, 5.6 ≦ x + y + z + 0.6 ≦ 6.0), which is a method for treating a negative electrode active material for a nickel metal hydride battery. And
The processing method of the negative electrode active material for nickel hydride batteries which has the process of stirring the negative electrode active material for nickel hydride batteries in alkaline aqueous solution. The method for treating a negative electrode active material for a nickel metal hydride battery according to any one of claims 1 to 3, wherein the alkaline aqueous solution is sodium hydroxide and / or potassium hydroxide. 4. The nickel hydride according to claim 1, wherein the basic molar concentration of the aqueous potassium hydroxide solution is 3 to 20 mol / L, and the basic molar concentration of the aqueous sodium hydroxide solution is 10 to 20 mol / L. The processing method of the negative electrode active material for batteries. The processing method of the negative electrode active material for nickel-metal hydride batteries according to any one of claims 1 to 3, wherein a treatment temperature in the step of stirring the negative electrode active material for nickel-metal hydride batteries in an alkaline aqueous solution is 80 to 150 ° C. The negative electrode active material for nickel metal hydride batteries obtained by the processing method of the negative electrode active material for nickel metal hydride batteries according to any one of claims 1 to 6. The nickel metal hydride battery using the negative electrode plate containing the negative electrode active material for nickel metal hydride batteries of Claim 7.

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