JP2008210556A - Alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery having excellent discharge characteristics and life characteristics although its negative electrode contains a rare eath-Mg-Ni based hydrogen storage alloy. <P>SOLUTION: The negative electrode 4 of this alkaline storage battery contains a conductive substrate 20 having a plurality of holes 20a, and hydrogen storage alloy particles 20 formed by applying paste containing material powder of the hydrogen storage alloy to the conductive substrate 20 and applying a rolling treatment to it after drying it and allowed to be retained in the substrate. The arithmetic average roughness Ra of the conductive substrate 20 after the rolling treatment is 3.0 μm or more, and the composition of the hydrogen storage alloy particle 22 is expressed by a general formula: ((PrND)<SB>α</SB>Ln<SB>1-α</SB>)<SB>1-β</SB>Mg<SB>β</SB>Ni<SB>γ-δ-ε</SB>AL<SB>δ</SB>T<SB>ε</SB>. The average particle diameter D50 of the material powder of the hydrogen storage alloy is within a range of not less than 6 μm and not more than 40 μm, and the coefficient of variation σ/D50 obtained by dividing standard deviation σ in the particle size distribution of the material powder of the hydrogen storage alloy by the average particle diameter D50 is not more than 1.5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an alkaline storage battery using hydrogen storage alloy particles as a negative electrode.

Alkaline storage batteries using a hydrogen storage alloy as a negative electrode are in great demand as consumer batteries because of their high capacity and their cleanliness compared to the use of lead and cadmium.
More specifically, the negative electrode includes a conductive substrate such as punching metal having a plurality of holes, and hydrogen storage alloy particles held on the conductive substrate. Such a negative electrode is formed by applying a paste containing a raw material powder of a hydrogen storage alloy to a conductive substrate and drying it, and then performing a rolling process and a cutting process.

As the hydrogen storage alloy particles, for example, a part of Ni of an MmNi ₅ type hydrogen storage alloy (Mm is a misch metal) whose main crystal phase is CaCu ₅ type (AB ₅ type) is an element such as Co, Mn, or Al. There is a substituted AB type ₅ hydrogen storage alloy (AB type ₅ alloy). AB ₅ type alloy particles have already been put into practical use, and the average particle size is generally about 50 μm. This is because when the average particle size is made larger than 50 μm, not only the discharge characteristics are deteriorated, but also the life characteristics are not sufficiently improved by the pulverization accompanying the progress of the charge / discharge cycle.

On the other hand, rare earth-Mg—Ni hydrogen storage alloys (rare earth-Mg—Ni alloys) are known as hydrogen storage alloys that store a larger amount of hydrogen at room temperature than the above AB ₅ type alloys. The rare earth-Mg—Ni alloy is obtained by substituting a part of rare earth elements in the AB ₅ type alloy system with Mg elements. However, although the AB ₅ type alloy has a large amount of occlusion of hydrogen, there is a problem that it is difficult to release the occluded hydrogen and the corrosion resistance against the alkaline electrolyte is low. Due to these problems, an alkaline storage battery in which a rare earth-Mg-Ni alloy is applied to the negative electrode has a problem that the discharge characteristics are poor and the cycle life is short.

Therefore, Patent Document 1 discloses a rare earth-Mg-Ni alloy having a composition represented by the following general formula and conditional formula.
_{(R 1-a-b La} a Ce b) 1-c Mg c Ni Z-X-Y-d-e Mn X Al Y Co d M e
c = (− 0.025 / a) + f
In these formulas, R is at least one element selected from the group consisting of rare earth elements including Y and Ca (excluding La and Ce), and M is Fe, Ga, Zn, Sn. , Cu, Si, B, Ti, Zr, Nb, W, Mo, V, Cr, Ta, Li, P and S, which are at least one element selected from the group consisting of atomic ratios a, b, c, d, e, f, X, Y and Z are 0 <a ≦ 0.45, 0 ≦ b ≦ 0.2, 0.1 ≦ c ≦ 0.24, 0 ≦ X ≦ 0.1, 0.02. ≤Y≤0.2, 0≤d≤0.5, 0≤e≤0.1, 3.2≤Z≤3.8, 0.2≤f≤0.29.

In this rare earth-Mg—Ni-based alloy, the relationship of c = (− 0.025 / a) + f is satisfied in the general formula, so that hydrogen is easily released and the discharge characteristics of the alkaline storage battery are improved. It is believed that. In addition, this relationship suppresses the precipitation of undesired crystal phases other than the Ce ₂ Ni ₇ structure, CeNi ₃ structure, and similar structures, thereby preventing a decrease in the hydrogen storage amount. As a result, the cycle of the alkaline storage battery is reduced. It is thought that the life characteristics are improved.

On the other hand, in this rare earth-Mg—Ni-based alloy, in the general formula, when Y indicating the proportion of Al is set to 0.02 or more, the oxidation is suppressed, but precipitation of an undesired crystal phase is caused. In order to suppress it, Y is set to 0.2 or less.
JP 2002-164045 A

However, even in the rare earth-Mg-Ni alloy of Patent Document 1, the hydrogen release characteristics, the corrosion resistance against the alkaline electrolyte, and the oxidation resistance are insufficient, and the alkaline storage battery to which the rare earth-Mg-Ni alloy is applied. It is desired to improve the discharge characteristics and life characteristics.
The present invention has been made on the basis of the above-described circumstances, and its object is to provide a high-capacity alkaline storage battery that is excellent in discharge characteristics and life characteristics while including a rare earth-Mg-Ni-based hydrogen storage alloy. Is to provide.

In order to achieve the above object, according to the present invention, in an alkaline storage battery including a positive electrode, a negative electrode, and an alkaline electrolyte, the negative electrode is a conductive substrate having a plurality of holes, and a hydrogen with respect to the conductive substrate. And hydrogen storage alloy particles held by applying a rolling treatment after applying a paste containing the raw material powder of the storage alloy, the arithmetic average roughness Ra of the conductive substrate after the rolling treatment is 3. The composition of the hydrogen storage alloy particles is 0 μm or more, and the composition of the hydrogen storage alloy particles is represented by the general formula: ((PrNd) _α Ln _1-α ) _1-β Mg _β Ni _γ-δ-ε Al _{δT ε}
(In the formula, Ln is selected from the group consisting of La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Sr, Sc, Y, Ti, Zr, and Hf. T represents at least one selected from the group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Zn, Ga, Sn, In, Cu, Si, P, and B. Represents the seed, and the subscripts α, β, γ, δ, ε are 0.7 <α, 0.05 <β <0.15, 3.0 ≦ γ ≦ 4.2, 0.15 ≦ δ ≦, respectively. (Represents a number satisfying 0.30, 0 ≦ ε ≦ 0.20)
The average particle size of the raw material powder of the hydrogen storage alloy is in the range of 60 μm to 140 μm, and the variation obtained by dividing the standard deviation of the particle size distribution of the raw material powder of the hydrogen storage alloy by the average particle size An alkaline storage battery having a coefficient of 1.5 or less is provided (claim 1).

The alkaline storage battery of the present invention is suitable for increasing the capacity because the negative electrode hydrogen storage alloy is made of a rare earth-Mg-Ni hydrogen storage alloy.
Moreover, the alkaline storage battery of the present invention has excellent life characteristics (cycle characteristics) and discharge characteristics. This is due to the following reason.
First, the subscript δ indicating the ratio of Al in the hydrogen storage alloy particles contained in the negative electrode of the battery is 0.15 or more. That is, when the Al ratio is higher than before, the crystal structure of the hydrogen storage alloy is stabilized, and the corrosion resistance and oxidation resistance against the alkaline electrolyte are improved. As a result, the battery life characteristics are improved.

In this way, the subscript δ could be set to 0.15 or more because the subscript β indicating the ratio of Mg in the hydrogen storage alloy contained in the negative electrode of the battery is 0.05 <β <0.15. And the subscript α indicating the total ratio of Pr and Nd at the A site of the hydrogen storage alloy is greater than 0.7.
That is, according to this hydrogen storage alloy, by setting the ratio of Mg, Pr and Nd within the above range, the solid solution limit of Al in the hydrogen storage alloy increases, and an undesired phase mainly composed of Al is formed. Without precipitating, the proportion of Al in the hydrogen storage alloy is increased as compared with the prior art. Even if the ratio of Mg, Pr, and Nd is set in the above range, if the subscript δ exceeds 0.30, an undesired phase mainly composed of Al is precipitated, so the subscript δ is 0.30 or less. Set to

Next, in the hydrogen storage alloy, the ratio of Pr and Nd is set in the above range, so that the hydrogen equilibrium pressure is higher than before. As the hydrogen equilibrium pressure increases, the operating voltage of the battery also increases. As a result, the discharge characteristics of the battery are improved.
In addition, the average particle size of the raw material powder of the hydrogen storage alloy is in the range of 60 μm to 140 μm, and the coefficient of variation obtained by dividing the standard deviation of the particle size distribution by the average particle size is 1.5 or less. The hydrogen storage alloy particles bite into the conductive substrate by the rolling process. Thereby, the contact resistance between the conductive substrate and the hydrogen storage alloy particles is reduced, and the discharge characteristics are further improved.

  Furthermore, when the average particle size of the raw material powder of the hydrogen storage alloy is in the range of 60 μm or more and 140 μm or less, and the coefficient of variation is 1.5 or less, the specific surface area of the hydrogen storage alloy particles is reduced and the life characteristics are improved. Is done.

FIG. 1 shows a nickel metal hydride storage battery as an alkaline storage battery according to an embodiment of the present invention.
This battery includes a bottomed cylindrical conductive outer can 1, and an electrode group 2 is accommodated in the outer can 1. The electrode group 2 is formed by winding a positive electrode 3 and a negative electrode 4 in a spiral shape with a separator 5 interposed therebetween, and a portion on the outer end side of the negative electrode 4 is disposed on the outermost periphery of the electrode group 2 in the spiral direction. The negative electrode 4 is electrically connected to the inner peripheral wall of the outer can 1. The outer can 1 contains an alkaline electrolyte (not shown).

In addition, as alkaline electrolyte, what mixed potassium hydroxide aqueous solution and sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, etc. to this can be used, for example.
In the opening end of the outer can 1, a circular lid plate 8 having a gas vent hole 7 in the center is disposed via a ring-shaped insulating gasket 6. The insulating gasket 6 and the cover plate 8 are fixed by the opening edge of the caulked outer can 1. Between the positive electrode 3 of the electrode group 2 and the inner surface of the cover plate 8, a positive electrode lead 9 that electrically connects them is disposed. On the other hand, a rubber valve body 10 is disposed on the outer surface of the cover plate 8 so as to close the gas vent hole 7, and a cylindrical positive electrode terminal 11 with a flange is attached so as to surround the valve body 10. ing.

An annular insulating plate 12 is disposed on the opening edge of the outer can 1, and the positive terminal 11 protrudes through the insulating plate 12. Reference numeral 13 is attached to the outer tube, and the outer tube 13 covers the outer peripheral edge of the insulating plate 12, the outer peripheral surface of the outer can 1 and the outer peripheral edge of the bottom wall.
The positive electrode 3 includes a conductive positive electrode substrate and a positive electrode mixture held on the positive electrode substrate. As the positive electrode substrate, for example, a net-like, sponge-like, fiber-like, or felt-like metal porous body plated with nickel can be used.

The positive electrode mixture includes a nickel hydroxide powder as a positive electrode active material, a conductive agent and a binder. The nickel hydroxide powder has an average valence of nickel larger than two and the surface of each particle. It is preferable to use a powder at least partially or entirely coated with a cobalt compound. Moreover, cobalt hydroxide and zinc may be dissolved in the nickel hydroxide powder.
As the conductive agent, for example, powders of cobalt oxide, cobalt hydroxide, metallic cobalt and the like can be used. As the binder, for example, carboxymethyl cellulose, methyl cellulose, PTFE dispersion, HPC dispersion, and the like. Can be used.

The positive electrode 3 described above is prepared by, for example, kneading nickel hydroxide powder, a conductive agent, a binder, and water to prepare a positive electrode slurry, and using the positive electrode substrate coated and filled with the positive electrode slurry as a positive electrode It can be produced by rolling and cutting after slurry drying.
As schematically shown in FIG. 2, the negative electrode 4 has a conductive negative electrode substrate 20, and the negative electrode substrate 20 has a plurality of through holes 20 a opened on both surfaces thereof. As the negative electrode substrate 20, for example, a punching metal plated with nickel can be used.

  A negative electrode mixture containing hydrogen storage alloy particles 22 is held on the negative electrode substrate. More specifically, the negative electrode mixture includes hydrogen storage alloy particles 22, a binder, and, if necessary, a conductive agent. As the binder, in addition to the same binder as the positive electrode mixture, for example, sodium polyacrylate may be used in combination. In addition, as the conductive agent, for example, carbon powder can be used. In FIG. 2, only the negative electrode substrate 20 and the hydrogen storage alloy particles 22 are schematically shown, and the binder and the conductive agent are omitted.

The hydrogen storage alloy particles 22 of the negative electrode 4 are made of a rare earth-Mg—Ni-based hydrogen storage alloy (rare earth-Mg—Ni-based alloy), and the composition is represented by the general formula (I): ((PrNd) _α Ln _1-α ) _{1 -Β} Mg _β Ni _γ-δ-ε Al _{δT ε} .
However, in formula (I), Ln is La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Sr, Sc, Y, Ti, Zr, and Hf. T represents at least one selected from the group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Zn, Ga, Sn, In, Cu, Si, P, and B. Represents at least one selected, and subscripts α, β, γ, δ, and ε are 0.7 <α, 0.05 <β <0.15, 3.0 ≦ γ ≦ 4.2, and 0.2, respectively. This represents a number satisfying 15 ≦ δ ≦ 0.30 and 0 ≦ ε ≦ 0.20.

The subscript α indicates the total ratio of Pr and Nd in the hydrogen storage alloy, and the hydrogen storage alloy may include only one of Pr and Nd alone.
The negative electrode 4 is prepared by preparing a negative electrode slurry comprising raw material powder of the hydrogen storage alloy particles 22, a binder, water, and a conductive agent blended as necessary, and the negative electrode substrate coated with the negative electrode slurry. Can be produced by rolling and cutting after drying the slurry for the negative electrode.

  Here, the rolling treatment is performed such that the arithmetic average roughness Ra of the negative electrode substrate 20 in the obtained negative electrode 4 is 3.0 μm or more. That is, the hydrogen storage alloy particles 22 are bitten into the negative electrode substrate 20 by rolling, and the arithmetic average roughness Ra of the surface of the negative electrode substrate 20 on which the irregularities are formed is 3.0 μm or more, preferably 4.0 μm or more. The rolling process is carried out so that

  The arithmetic average roughness Ra is defined in JIS B0601-1994 and can be measured by a three-dimensional roughness meter. Specifically, the arithmetic average roughness Ra is obtained by measuring the surface shape of the negative electrode substrate 20 in a region excluding the through-hole 20a with a three-dimensional roughness measuring instrument to obtain a roughness curve, and extracting it from the roughness curve. This is a value obtained by dividing the sum of absolute values of deviations between the reference length portion and the average line by the reference length.

The raw material powder of the hydrogen storage alloy 22 has an average particle size in the range of 60 μm to 140 μm, and a coefficient of variation obtained by dividing the standard deviation σ of the particle size distribution by the average particle size is 1.5 or less. Preferably, those having a particle size of 1.2 or less are used.
The average particle size of the raw material powder is a particle size (D50 corresponding to 50% weight integral in the obtained particle size distribution when the particle size distribution of the raw material powder is measured using a laser diffraction / scattering type particle size distribution analyzer. ). The coefficient of variation is not a percentage.

Such raw material powder of the hydrogen storage alloy particles 22 is produced, for example, as follows.
First, metal raw materials are weighed and mixed so as to have the composition shown in the general formula (I), and this mixture is melted in, for example, a high-frequency melting furnace to make an ingot. The obtained ingot is heat-treated in an inert gas atmosphere at a temperature of 900 to 1200 ° C. for 5 to 24 hours, so that the crystal structure of the ingot is changed to a Ce ₂ Ni ₇ type structure or a similar structure. In other words, a superlattice structure of AB ₅ type structure and AB ₂ type structure is adopted. Thereafter, the ingot is pulverized and classified to a desired particle size by sieving to produce the raw material powder of the hydrogen storage alloy particles 22.

The nickel-metal hydride storage battery described above is suitable for high capacity because the hydrogen storage alloy of the negative electrode is made of a rare earth-Mg-Ni based hydrogen storage alloy having the composition represented by the general formula (I) and has a large amount of hydrogen storage at room temperature. ing.
Moreover, the nickel hydride storage battery mentioned above has the outstanding discharge characteristic and lifetime characteristic. This is due to the following reason.

First, the subscript δ indicating the ratio of Al in the hydrogen storage alloy contained in the negative electrode of the battery is 0.15 or more. That is, when the Al ratio is higher than before, the crystal structure of the hydrogen storage alloy is stabilized, and the corrosion resistance and oxidation resistance against the alkaline electrolyte are improved. As a result, the battery life characteristics are improved.
In this way, the subscript δ could be set to 0.15 or more because the subscript β indicating the ratio of Mg in the hydrogen storage alloy contained in the negative electrode of the battery is 0.05 <β <0.15. And the subscript α indicating the total ratio of Pr and Nd at the A site of the hydrogen storage alloy is greater than 0.7.

  That is, according to this hydrogen storage alloy, by setting the ratio of Mg, Pr and Nd within the above range, the solid solution limit of Al in the hydrogen storage alloy increases, and an undesired phase mainly composed of Al is formed. Without precipitating, the proportion of Al in the hydrogen storage alloy is increased as compared with the prior art. Even if the ratio of Mg, Pr, and Nd is set in the above range, if the subscript δ exceeds 0.30, an undesired phase mainly composed of Al is precipitated, so the subscript δ is 0.30 or less. Set to

Next, in this hydrogen storage alloy, the hydrogen equilibrium pressure is increased by setting the ratio of Pr and Nd in the above range. As the hydrogen equilibrium pressure increases, the operating voltage of the battery also increases. As a result, the discharge characteristics of the battery are improved.
In addition, since the average particle size of the raw material powder of the hydrogen storage alloy is in the range of 60 μm to 140 μm and the coefficient of variation σ / D50 is 1.5 or less, the hydrogen storage alloy particles are formed on the conductive substrate by rolling. Encroach appropriately. Thereby, the contact resistance between the conductive substrate and the hydrogen storage alloy particles is reduced, and the discharge characteristics are further improved.

Furthermore, when the average particle size of the raw material powder of the hydrogen storage alloy is in the range of 60 μm or more and 140 μm or less and the coefficient of variation σ / D50 is 1.5 or less, the specific surface area of the hydrogen storage alloy particles is reduced and the service life is reduced. The characteristics are improved.
In the above-described nickel-metal hydride storage battery, in general formula (I), the subscript β is set to 0.15 or less, so that precipitation of an undesired phase mainly composed of Mg is prevented. Battery life characteristics are improved. That is, when the subscript β is 0.15 or less, the formation of fine particles of the hydrogen storage alloy powder accompanying the charge / discharge cycle is suppressed, thereby improving the life characteristics. On the other hand, when the subscript β is set to 0.05 or more, the hydrogen storage alloy can store a large amount of hydrogen.

In the general formula (I), if the subscript γ is too small, the hydrogen storage stability in the hydrogen storage alloy is increased, so that the hydrogen releasing ability is deteriorated, and if the subscript γ is too large, this time, The hydrogen storage sites in the hydrogen storage alloy decrease, and the hydrogen storage capacity begins to deteriorate. Therefore, the subscript γ is set so as to satisfy 3.0 ≦ γ ≦ 4.2.
Further, in the general formula (I), the subscript ε indicates the amount of substitution of the Ni substituting element T. However, if the subscript ε becomes too large, the hydrogen storage alloy changes its crystal structure and exhibits hydrogen storage / release capability. As soon as it starts to be lost, elution of the substitution element T into the alkaline electrolyte begins to occur, and the composite precipitates on the separator, reducing the long-term storability of the battery. Therefore, the subscript ε is set so as to satisfy 0 ≦ ε ≦ 0.20.

Example 1
1. Preparation of negative electrode The metal raw materials were weighed and mixed so that the composition was (La _0.10 Ce _0.05 Pr _0.35 Nd _0.50 ) _0.90 Mg _0.10 Ni _3.22 Al _0.22, and this mixture was melted in a high-frequency melting furnace to obtain an ingot. This ingot was heated in an argon atmosphere at a temperature of 1000 ° C. for 10 hours, and the crystal structure of the ingot was changed to a Ce ₂ Ni ₇ type structure or a similar structure. Thereafter, the ingot was mechanically pulverized in an inert atmosphere and sieved to obtain a raw material powder of rare earth-Mg—Ni-based hydrogen storage alloy particles having the above composition. At this time, by changing the pulverization and sieving conditions, the average particle size D50 was 50, 100, 120 or 160 μm, and the variation coefficient σ / D50 was 1.5 or less. A raw material powder having a diameter D50 of 100 μm and a coefficient of variation σ / D50 of 1.7 was prepared.

The average particle diameter D50 of the obtained raw material powder is a particle diameter corresponding to 50% by weight in the particle size distribution measured using a laser diffraction / scattering particle size distribution measuring apparatus (LA-300 manufactured by HORIBA).
For 100 parts by mass of each raw material powder obtained, 0.5 parts by mass of sodium polyacrylate, 0.12 parts by mass of carboxymethylcellulose, PTFE dispersion (dispersion medium: water, specific gravity 1.5, solid content 60% by mass) 1.0 parts by mass (in terms of solid content), 1.0 part by mass of carbon black and 30 parts by mass of water were added and kneaded to prepare a slurry for negative electrode.

On the other hand, a 2 μm Ni plating was applied to a punching sheet made of Fe having a porosity of 43% and a thickness of 60 μm to produce a negative electrode substrate. The surface hardness of the produced negative electrode substrate was 100 Hv in terms of Vickers hardness. A negative electrode slurry was applied to the negative electrode substrate, and after the negative electrode slurry was dried, roll rolling and cutting were performed to prepare a negative electrode for SC size.
In the roll rolling process, the rolling load is adjusted so that the arithmetic average roughness Ra of the negative electrode substrate after the roll rolling process becomes the value shown in Table 1, and the hydrogen storage alloy particles bite into the negative electrode substrate. The degree of change. The arithmetic average roughness Ra of the negative electrode substrate after the roll rolling treatment shown in Table 1 was measured by removing the negative electrode mixture after the roll rolling treatment and using a three-dimensional roughness measuring instrument (EMS98-3D manufactured by Sigma Koki Co., Ltd.). .

2. Preparation of positive electrode A nickel hydroxide powder in which all or a part of each particle is coated with a cobalt compound is prepared, and 100 mass parts of the nickel hydroxide powder is mixed with an HPC dispersion having a concentration of 40 mass%. A slurry was prepared, and the sheet-like nickel porous body coated and filled with this positive electrode slurry was dried and then rolled and cut to produce a positive electrode.
3. Assembling the nickel-metal hydride storage battery The obtained negative electrode and positive electrode are spirally wound through a separator made of a nonwoven fabric made of polypropylene fiber and having a thickness of 0.15 mm and a basis weight of 60 g / m ² to produce an electrode group. did. After the obtained electrode group was housed in an outer can and subjected to a predetermined mounting step, an alkaline electrolyte composed of a 7N potassium hydroxide aqueous solution and a 1N lithium hydroxide aqueous solution was poured into the outer can. . Then, the open end of the outer can was sealed with a cover plate or the like, and the sealed cylindrical nickel-metal hydride batteries of Examples 1 and 2 and Comparative Examples 1 to 4 having a rated capacity of 3000 mAh and an SC size were assembled.

The assembled battery is charged with 0.1 It (CmA) charging current for 15 hours in an environment at a temperature of 25 ° C., and then discharged to a final voltage of 1.0 V with a discharge current of 0.2 It. gave.
4). Battery Evaluation The following tests were conducted on the nickel hydride storage batteries of Examples 1 and 2 and Comparative Examples 1 to 4 that were subjected to the initial activation treatment.

(1) Life characteristics (cycle characteristics)
For each battery, charging / discharging consisting of charging by dV control at a charging current of 1.0 It in a temperature of 40 ° C., resting for 60 minutes, discharging to a final voltage of 1.0 V at a discharging current of 5.0 It The cycle was repeated. At this time, the discharge capacity was measured in each cycle, and the number of cycles when the discharge capacity was less than 60% of the discharge capacity in the first cycle is shown in Table 1.
(2) Discharge characteristics Each battery was charged by dV control at a charging current of 1.0 It in an environment at a temperature of 25 ° C, and then a rest time of 180 minutes was taken in an environment at a temperature of 0 ° C. Thereafter, a pulse discharge with a discharge current of 40 A and a pulse width of 2 seconds was repeated to a final voltage of 0.3 V with a rest time of 8 seconds. The voltage value immediately after each pulse discharge was measured, and the lowest voltage value when the discharge depth is within 30% is shown in Table 1 as discharge characteristics. The higher the voltage value, the better the discharge characteristics.

From Table 1, the following is clear.
(1) The discharge characteristics and life characteristics of Examples 1 and 2 are excellent.
(2) Examples 1 and 2 having a coefficient of variation σ / D50 of 0.92 and 0.95, respectively, are remarkably superior in life characteristics as compared with Comparative Example 1 having a coefficient of variation σ / D50 of 1.70. This is because in Comparative Example 1, since the standard deviation σ of the particle size distribution is large, the particle size distribution is broad, and the raw material powder contains many fine particles. The fine particles are likely to be corroded by the alkaline electrolyte due to their large specific surface area, which is considered to be due to consumption of the alkaline electrolyte.

(3) Example 1 in which the arithmetic average roughness Ra of the negative electrode substrate is 4.5 is remarkably superior in discharge characteristics as compared with Comparative Example 2 in which the arithmetic average roughness Ra of the negative electrode substrate is 2.3. Although the raw material powder is the same, in Comparative Example 2, the negative electrode mixture and the hydrogen storage alloy particles were reduced in comparison with Example 1 because the negative load was made lower by reducing the rolling load of the roll rolling process. It is thought that the contact resistance between them became high.
(4) Example 1 having an average particle diameter D50 of 100 μm is significantly superior in life characteristics as compared with Comparative Example 3 having an average particle diameter D50 of 50 μm. This is presumably because, in Comparative Example 3, the hydrogen storage alloy particles were easily corroded because the specific surface area of the hydrogen storage alloy particles was larger than that in Example 1, thereby consuming the alkaline electrolyte.
(5) Example 1 having an average particle diameter D50 of 100 μm is significantly superior in discharge characteristics as compared with Comparative Example 4 having an average particle diameter D50 of 160 μm. This is presumably because, in Comparative Example 4, compared with Example 1, the specific surface area of the hydrogen storage alloy particles is large, and thus the reaction resistance is high.

The present invention is not limited to the above-described embodiment and its examples, and various modifications are possible. The battery may be a prismatic battery, and the mechanical structure is not particularly limited. .
In one embodiment, Ln is a group consisting of La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Sr, Sc, Y, Ti, Zr, and Hf. In the case where Ce is selected as Ln, it is preferable that the ratio of Ce in Pr, Nd and Ln does not exceed 0.2. This is because if the ratio of Ce exceeds 0.2, the hydrogen storage ability of the hydrogen storage alloy is lowered.

In one embodiment, the subscript α was greater than 0.7, but is preferably greater than 0.75, and more preferably greater than 0.80. The subscript α may be 1 as the maximum value.
In one embodiment, the subscript β was in the range 0.05 <β <0.15, but is preferably in the range 0.07 <β <0.14, and 0.08 <β <0.12. More preferably, it is in the range.

In one embodiment, the subscript γ was in the range of 3.0 ≦ γ ≦ 4.2, but preferably in the range of 3.2 ≦ γ ≦ 3.8, 3.3 ≦ γ ≦ 3.7. More preferably, it is in the range.
In one embodiment, the subscript δ was in the range of 0.15 ≦ δ ≦ 0.30, but is preferably in the range of 0.17 ≦ δ ≦ 0.27, and 0.20 ≦ δ ≦ 0.25. More preferably, it is in the range.

In one embodiment, the subscript ε was in the range 0 ≦ ε ≦ 0.20, but preferably in the range 0 ≦ ε ≦ 0.15, and in the range 0 ≦ ε ≦ 0.10. More preferred.
In one embodiment, the negative electrode mixture is composed of a hydrogen storage alloy powder, a binder, and optionally a conductive agent, but the negative electrode mixture further includes an additive powder composed of Al (OH) _3. It is preferable. This is due to the following reason.

The rare earth-Mg—Ni-based hydrogen storage alloy having the composition represented by the general formula (I) has high corrosion resistance and oxidation resistance to the alkaline electrolyte. For this reason, in the nickel metal hydride storage battery to which this hydrogen storage alloy is applied, Al of the hydrogen storage alloy is difficult to dissolve in the alkaline electrolyte.
Therefore, the negative electrode of the nickel-metal hydride storage battery described above preferably contains Al (OH) ₃ as an additive in addition to Al of the hydrogen storage alloy, despite the large proportion of Al in the hydrogen storage alloy. Al (OH) ₃ becomes a gel compound in the alkaline electrolyte, and the gel compound distributed in the vicinity of the positive electrode increases the oxygen overvoltage of the nickel hydroxide powder, which is the positive electrode active material, and the self-reduction of the nickel hydroxide powder. To prevent. As a result, self-discharge during storage of the nickel-metal hydride storage battery is prevented.

Further, since the self-discharge is prevented by the gel compound during storage of the battery, it is possible to prevent the nickel hydroxide powder from being excessively reduced to an irreversible region. As a result, a decrease in capacity before and after storage of the nickel-metal hydride storage battery is suppressed.
Finally, the alkaline storage battery of the present invention can be applied not only to nickel-metal hydride storage batteries but also to alkaline storage batteries in which the negative electrode contains hydrogen storage alloy powder.

It is a partial notch perspective view which shows the nickel hydride storage battery as an alkaline storage battery of one Embodiment of this invention. It is the figure which expanded and schematically showed a part of cross section of the negative electrode used for the battery of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Electrode group 3 Positive electrode 4 Negative electrode 5 Separator 20 Conductive substrate 20a Hole (through hole)
22 Hydrogen storage alloy particles

Claims (1)

In an alkaline storage battery comprising a positive electrode, a negative electrode and an alkaline electrolyte,
The negative electrode is
A conductive substrate having a plurality of holes;
The conductive substrate, the hydrogen storage alloy particles held by applying a rolling treatment after applying a paste containing the raw material powder of the hydrogen storage alloy and then performing a rolling treatment,
The arithmetic average roughness Ra of the conductive substrate after the rolling treatment is 3.0 μm or more,
The composition of the hydrogen storage alloy particles is:
General _{formula: ((PrNd) α Ln 1} -α) 1-β Mg β Ni γ-δ-ε Al δ T ε
(In the formula, Ln is selected from the group consisting of La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ca, Sr, Sc, Y, Ti, Zr, and Hf. T represents at least one selected from the group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Zn, Ga, Sn, In, Cu, Si, P, and B. Represents the seed, and the subscripts α, β, γ, δ, ε are 0.7 <α, 0.05 <β <0.15, 3.0 ≦ γ ≦ 4.2, 0.15 ≦ δ ≦, respectively. (Represents a number satisfying 0.30, 0 ≦ ε ≦ 0.20)
Indicated by
The average particle diameter of the raw material powder of the hydrogen storage alloy is in the range of 60 μm to 140 μm,
An alkaline storage battery having a coefficient of variation obtained by dividing the standard deviation of the particle size distribution of the raw material powder of the hydrogen storage alloy by the average particle size of 1.5 or less.

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