JP5991525B2 - Alkaline storage battery - Google Patents

Description

  The present invention relates to an alkaline storage battery, and more particularly to an improvement in an electrolyte solution in an alkaline storage battery using a negative electrode including a hydrogen storage alloy containing magnesium.

  An alkaline storage battery using a negative electrode containing a hydrogen storage alloy as a negative electrode active material has excellent output characteristics and high durability (such as life characteristics and storage characteristics). Therefore, such alkaline storage batteries are attracting attention as power sources for electric vehicles and the like. On the other hand, in recent years, since lithium ion secondary batteries are also used for this purpose, it is desired to further improve battery characteristics such as output characteristics and durability from the viewpoint of highlighting the advantages of alkaline storage batteries. .

As the hydrogen storage alloy, a hydrogen storage alloy having a CaCu ₅ type crystal structure is mainly used. When a high alloy capacity is required, a hydrogen storage alloy containing a Ce ₂ Ni ₇ type or CeNi ₃ type crystal structure is used. In addition, attempts have been made to optimize the composition and amount of the electrolytic solution in order to improve the battery characteristics of the alkaline storage battery.

  For example, in Patent Document 1, in order to further improve the low-temperature discharge characteristics and capacity, a hydrogen storage alloy containing Mg and Ni is used for the negative electrode, the amount X (g) of hydrogen storage alloy per theoretical capacity 1 Ah, and the positive electrode It has been proposed that the amount Y (ml) of the electrolytic solution per theoretical capacity 1 Ah satisfies 3.2 ≦ X ≦ 5.0 and 0.9 ≦ Y ≦ 0.2X + 0.7.

Patent Document 2 uses 5 to 40 mol% of potassium hydroxide with respect to the total alkali contained in the electrolytic solution in order to increase the charge acceptability in a high temperature atmosphere and the positive electrode utilization rate at room temperature. It has been proposed. The electrolytic solution actually used in Patent Document 2 contains sodium hydroxide at a higher concentration than potassium hydroxide.
In Patent Document 3, it is proposed to use 20 to 50 mol% of sodium hydroxide with respect to the total metal hydroxide contained in the electrolytic solution in order to increase the battery capacity.

JP-A-11-162503 JP 2003-229167 A JP-A-11-219702

  In alkaline storage batteries, potassium hydroxide is used as an electrolyte from the viewpoint of conductivity, and Patent Document 1 also describes that an electrolyte containing potassium hydroxide is preferable. However, when an electrolyte containing a large amount of potassium hydroxide is combined with a negative electrode containing a hydrogen storage alloy containing Mg, Mg contained in the hydrogen storage alloy is eluted into the electrolyte and the hydrogen storage alloy is easily corroded. . In particular, when the battery is stored at a high temperature, the elution of Mg tends to be remarkable, the corrosion of the hydrogen storage alloy proceeds, and the battery is liable to be deteriorated due to a decrease in capacity or withering of the electrolyte. Therefore, even if a hydrogen storage alloy having a large capacity is used, it is difficult to effectively use the capacity. Moreover, since the battery is likely to deteriorate after high temperature storage, it is difficult to improve the cycle life.

  In Patent Document 2 and Patent Document 3, the electrolytic solution contains a relatively large amount of sodium hydroxide. However, since the electrolyte containing a large amount of sodium hydroxide has low conductivity, it is difficult to improve discharge characteristics at low temperatures (for example, 0 ° C. or lower).

  An object of the present invention is to provide an alkaline storage battery that can be used in a wide temperature range by improving both low temperature discharge characteristics and high temperature storage characteristics when using a negative electrode containing a hydrogen storage alloy containing Mg. The purpose is to do.

One aspect of the present invention includes a positive electrode including nickel, a negative electrode including a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte. The hydrogen storage alloy contains La, Mg, Ni, Co, Al, and the element M, and the molar ratio x of Mg in the total of La and Mg is 0.01 ≦ x ≦ 0.5, and La and The molar ratio y of Ni to the total of Mg is 2 ≦ y ≦ 4, and the molar ratio z of Co to the total of La and Mg is 0.25 ≦ z ≦ 0.75, and is relative to the total of La and Mg. The molar ratio α of Al is 0.01 ≦ α ≦ 0.06, the element M is at least one selected from the group consisting of Y and Sn, and the amount of the element M is 0 % in the hydrogen storage alloy. 0.01 to 0.4% by mass , and the alkaline electrolyte is 0.08 to 4%. The present invention relates to an alkaline storage battery containing 0.2% by mass of potassium hydroxide KOH, 9.7-30.4% by mass of sodium hydroxide NaOH, and 0.05-0.53% by mass of lithium hydroxide LiOH.

  According to the present invention, in an alkaline storage battery, conductivity at low temperature can be improved, so that discharge characteristics at low temperature can be improved, and elution of constituent elements such as Mg contained in a hydrogen storage alloy used for the negative electrode can be suppressed. Therefore, high temperature storage characteristics can be improved.

FIG. 1 is a graph showing the elution amounts of Co and Mg contained in a hydrogen storage alloy with respect to an alkaline aqueous solution. FIG. 2 is a longitudinal sectional view schematically showing the structure of an alkaline storage battery according to an embodiment of the present invention.

  The alkaline storage battery of the present invention comprises a positive electrode containing nickel, a negative electrode containing a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte. It has.

  The hydrogen storage alloy includes La, Mg, Ni, Co, Al, and the element M, and the molar ratio x of Mg in the total of La and Mg is 0.01 ≦ x ≦ 0.5, and La and Mg The molar ratio y of Ni with respect to the sum of is 2 ≦ y ≦ 4, the molar ratio z of Co with respect to the sum of La and Mg is 0.25 ≦ z ≦ 0.75, and Al with respect to the sum of La and Mg The molar ratio α is 0.01 ≦ α ≦ 0.06. The element M is at least one selected from the group consisting of Y and Sn, and the amount of the element M is 0.45% by mass or less of the hydrogen storage alloy.

  The hydrogen storage alloy as described above has a large amount of hydrogen storage and can increase the capacity. On the other hand, in the alkaline storage battery, the constituent elements of the hydrogen storage alloy may elute into the alkaline electrolyte and the corrosion of the hydrogen storage alloy may proceed. When the hydrogen storage alloy is corroded, the capacity is reduced and the electrolyte is partially depleted, so that the battery is deteriorated. The elution of the constituent elements of the hydrogen storage alloy tends to become remarkable particularly at high temperatures. Therefore, when stored at a high temperature, the corrosion of the hydrogen storage alloy further proceeds more easily.

  The present inventors have found that the elution properties of the constituent elements of the hydrogen storage alloy differ depending on the kind of constituent elements and the kind of cations contained in the alkaline electrolyte. This will be described in more detail below.

  Using the above hydrogen storage alloy, the solubility of the constituent elements of the hydrogen storage alloy in an alkaline aqueous solution was examined. Specifically, hydrogen storage alloy particles having a particle size in the range of 20 to 150 μm classified by a 20 μm and 150 μm mesh sieve are surface-treated with a predetermined concentration of sodium hydroxide aqueous solution, washed with water, and dried. Particles were used. 3 g of these particles were added to 30 ml of an alkaline aqueous solution, and stirred with vibration at 80 ° C. for 4 hours, and the amount of the element eluted from the hydrogen storage alloy was measured. As the alkaline aqueous solution, an aqueous solution containing KOH, NaOH or LiOH at a concentration of 5 mol / L was used.

  The amount of the element eluted in the alkaline aqueous solution can be quantitatively measured by inductively coupled plasma (ICP) analysis. The ICP analysis can be performed by using, for example, an ICP emission spectroscopic analyzer defined in JIS K0116. Specifically, the alkaline aqueous solution is sprayed into a plasma torch according to JIS K0116, and the amount of elements in the sample is quantified based on the emission intensity at a specific wavelength.

FIG. 1 shows the results when using 0.3 mass% Y of hydrogen storage alloy particles with a composition of La _0.7 Mg _0.3 Ni _2.75 Co _0.5 Al _0.05 . FIG. 1 is a graph showing the elution amounts of Co and Mg of the alloy particles in an alkaline aqueous solution containing KOH, NaOH or LiOH as an alkali.

  As is clear from FIG. 1, the elution of Co increases in the order of KOH <NaOH <LiOH. On the other hand, the elution property of Mg increases in the order of NaOH <KOH <LiOH. That is, it can be seen that the elution properties of the constituent elements contained in the alloy particles are different depending on the types of cations contained in the alkaline aqueous solution, and the corrosivity of the alloy particles is also different.

  Although the details of the elution mechanism of each element are unknown, the elution of Mg follows the ionization tendency of cations contained in the alkaline aqueous solution. NaOH containing sodium can suppress elution of Mg as compared with KOH.

In the case of a hydrogen storage alloy containing Mg, the eluate eluted into the aqueous alkali solution is Mg ^ions such as Mg ²⁺ , other alkaline earth metal ions, light rare earth metal ions (La ³⁺ etc.), complex anions, etc. (e.g. AlO ₂ ^-, etc.) and the like. Such components eluted from the hydrogen storage alloy include hydroxides (for example, hydroxides of light rare earth metals such as La (OH) ₃ ), oxides (for example, complex oxides including Mn, Mg, etc.) ) And so on. When such a deposit is deposited, the positive electrode and the negative electrode are short-circuited, the battery voltage is lowered, and the battery is deteriorated. In particular, during storage at a high temperature, the elution of the constituent elements from the hydrogen storage alloy becomes significant, so that the deterioration of the battery becomes significant.

  In a hydrogen storage alloy containing Mg and Co, although the elution amount of Mg is smaller than the elution amount of Co, since Mg is more likely to reprecipitate than Co, battery deterioration is likely to occur. If only the amount of elution is observed, it is considered advantageous to use KOH with a small amount of Co elution as the electrolyte. However, even if the elution amount of Mg is small, it causes battery deterioration. From the viewpoint of suppressing battery deterioration, it is advantageous to use NaOH as an electrolyte rather than KOH.

  However, since Na has a lower ionization tendency than K, NaOH has a lower conductivity than KOH. The decrease in conductivity is likely to be noticeable particularly at low temperatures. Therefore, when NaOH is used as an electrolyte, the discharge characteristics at low temperatures are likely to be impaired.

  In addition, LiOH has a high ion mobility in an alkaline electrolyte, and thus is advantageous for ensuring conductivity at a low temperature. LiOH also affects the stability of the positive electrode and has a role to alleviate overvoltage at the end of discharge.

  Thus, the high-temperature storage characteristics and the low-temperature discharge characteristics are greatly influenced by the type of cation in the alkaline electrolyte, and in particular when using a negative electrode containing a hydrogen storage alloy containing Mg, both characteristics must be compatible. Is difficult.

  In view of such a viewpoint, when using the negative electrode containing the hydrogen storage alloy having the specific composition as described above containing Mg, the present inventors select the type of alkali in the alkaline electrolyte and include the negative electrode. It was found that by adjusting the amount, both high temperature storage characteristics and low temperature discharge characteristics can be improved. By satisfying these characteristics, the present invention can provide an alkaline storage battery that can be used in a wide temperature range.

  In the present invention, an alkaline electrolyte containing 0.08 to 40.2 mass% KOH, 9.7 to 30.4 mass% NaOH, and 0.53 mass% or less LiOH in combination with the negative electrode described above. Is used.

  Although KOH has higher elution of Mg than NaOH, it is easily ionized in an aqueous solution and exhibits high conductivity, which is advantageous in preventing a decrease in conductivity at low temperatures. When the content of KOH in the alkaline electrolyte is less than 0.08% by mass, it is difficult to sufficiently suppress the decrease in conductivity at low temperatures. In addition, when the KOH content exceeds 40.2 mass%, the elution amount of constituent elements of the hydrogen storage alloy such as Mg increases especially at high temperatures, and the deterioration of the negative electrode proceeds, so that the high-temperature storage characteristics deteriorate. To do. In addition, since ions in the alkaline electrolyte are excessively present and the ions interfere with each other, the speed of ion movement decreases, and the discharge characteristics deteriorate even at room temperature.

On the other hand, when the content of NaOH in the alkaline electrolyte is less than 9.7% by mass, the mobility of the salt in the alkaline electrolyte tends to be low, and the discharge characteristics are deteriorated. Further, the demerits associated with the properties of KOH and LiOH are easily realized. When the content of NaOH exceeds 30.4% by mass, the conductivity at low temperature is lowered, so that the low temperature discharge characteristics are impaired.
If the LiOH content in the alkaline electrolyte exceeds 0.53% by mass, the reason is unclear whether the activity of the hydrogen storage alloy or the balance of ions in the alkaline electrolyte is affected. Decreases.

  In this way, the alkaline electrolyte contains KOH that increases the conductivity at low temperature, NaOH that reduces the elution amount of Mg, and LiOH that increases the conductivity at low temperature at a specific content, thereby reducing the temperature. In addition to improving the discharge characteristics of the battery, elution of constituent elements contained in the hydrogen storage alloy, particularly elution during high-temperature storage of the battery, can be suppressed.

Below, the structure and each component of an alkaline storage battery are demonstrated in detail.
FIG. 2 is a longitudinal sectional view schematically showing the structure of an alkaline storage battery according to an embodiment of the present invention. The alkaline storage battery includes a bottomed cylindrical battery case 4 also serving as a negative electrode terminal, an electrode group housed in the battery case 4 and an alkaline electrolyte (not shown). In the electrode group, the negative electrode 1, the positive electrode 2, and the separator 3 interposed therebetween are spirally wound. A sealing plate 7 including a safety valve 6 is disposed in the opening of the battery case 4 via an insulating gasket 8, and the alkaline storage battery is hermetically sealed by caulking the opening end of the battery case 4 inward. The sealing plate 7 also serves as a positive electrode terminal, and is electrically connected to the positive electrode 2 via the positive electrode current collector plate 9.

  In such an alkaline storage battery, an electrode group is accommodated in a battery case 4, an alkaline electrolyte is injected, a sealing plate 7 is disposed in an opening of the battery case 4 via an insulating gasket 8, and the battery case 4 Can be obtained by caulking and sealing. At this time, the negative electrode 1 of the electrode group and the battery case 4 are electrically connected via a negative electrode current collector plate disposed between the electrode group and the inner bottom surface of the battery case 4. Further, the positive electrode 2 of the electrode group and the sealing plate 7 are electrically connected via the positive electrode current collector plate 9.

  In this invention, the negative electrode containing the above hydrogen storage alloys is used. Therefore, nickel hydride storage batteries are particularly preferable among alkaline storage batteries.

Below, the component of an alkaline storage battery is demonstrated more concretely.
(Alkaline electrolyte)
In the present invention, the above negative electrode and an alkaline electrolyte having a characteristic composition are used in combination. The alkaline electrolyte contains KOH, NaOH, and LiOH as the electrolyte.
The content (concentration) of KOH in the alkaline electrolyte is 0.08% by mass or more, preferably 0.09% by mass or more, more preferably 0.1% by mass or more or 0.4% by mass or more. The KOH content is 40.2% by mass or less, preferably 40% by mass or less, and more preferably 22% by mass or less or 10% by mass or less. These lower limit value and upper limit value can be appropriately selected and combined. 0.08-40 mass%, 0.1-40 mass%, or 0.5-10 mass% may be sufficient as content of KOH, for example.

  The content (concentration) of NaOH in the alkaline electrolyte is 9.7% by mass or more, preferably 9.8% by mass or more, and more preferably 10% by mass or more. The content of NaOH is 30.4% by mass or less, preferably 30.2% by mass or less, more preferably 30% by mass or less. These lower limit value and upper limit value can be appropriately selected and combined. The content of NaOH may be, for example, 9.7 to 30.2% by mass or 10 to 30% by mass.

  The total content of KOH and NaOH in the alkaline electrolyte is, for example, 10.5% by mass or more, preferably 10.7% by mass or more, and more preferably 11% by mass or more. When the total content of KOH and NaOH is within such a range, it is more advantageous in increasing the conductivity, particularly the conductivity at a low temperature.

  The content (concentration) of LiOH in the alkaline electrolyte is 0.53% by mass or less, preferably 0.52% by mass or less, and more preferably 0.5% by mass or less. The LiOH content is, for example, 0.05% by mass or more, preferably 0.07% by mass or more, and more preferably 0.1% by mass or more. These upper limit value and lower limit value can be appropriately selected and combined. The content of LiOH may be, for example, 0.05 to 0.53 mass% or 0.1 to 0.5 mass%.

From the viewpoint of more effectively suppressing elution of a hydrogen storage alloy such as Mg, the KOH content, the NaOH content, and the LiOH content in the alkaline electrolyte have the following relationship:
It is preferable that the content of LiOH <the content of KOH <the content of NaOH.

  The alkaline electrolyte may contain other alkalis such as metal hydroxides in addition to the above three types of alkali metal hydroxides. Moreover, the alkaline electrolyte may contain a known additive. However, the content of the additive is preferably 5% by mass or less of the alkaline electrolyte.

  The alkaline electrolyte may be prepared by dissolving all hydroxides in water, or an aqueous solution containing each hydroxide may be prepared, and the alkaline electrolyte may be prepared by mixing these aqueous solutions. Good. Alternatively, an alkaline electrolyte may be prepared by preparing an aqueous solution containing any hydroxide (for example, KOH) and dissolving the remaining hydroxide in this aqueous solution. The specific gravity of the aqueous KOH solution used in this preparation method is, for example, 1.01 to 1.5, preferably 1.1 to 1.35, and the specific gravity of the obtained alkaline electrolyte is, for example, 1.03 to 3. 1.55, preferably 1.11 to 1.32.

(Negative electrode)
The negative electrode includes a hydrogen storage alloy having the above composition and capable of electrochemically storing and releasing hydrogen.
The composition of the alkaline electrolyte and the composition of the hydrogen storage alloy are closely related to the low temperature discharge characteristics and high temperature storage characteristics of the alkaline storage battery.

  In the hydrogen storage alloy, the molar ratio x of Mg in the total of La and Mg is 0.01 ≦ x ≦ 0.5, preferably 0.1 ≦ x ≦ 0.4, and more preferably 0.25 ≦ x ≦ 0.35. The molar ratio y of Ni to the sum of La and Mg is 2 ≦ y ≦ 4, preferably 2.5 ≦ y ≦ 3.5. The molar ratio z of Co to the sum of La and Mg is 0.25 ≦ z ≦ 0.75, preferably 0.25 ≦ z ≦ 0.7 or 0.25 ≦ z ≦ 0.6. The molar ratio α of Al to the sum of La and Mg is 0.01 ≦ α ≦ 0.06, preferably 0.01 ≦ α <0.06, more preferably 0.03 ≦ α ≦ 0.055 or 0.005. It is 03 <= α <= 0.05.

Specific examples of the composition containing La, Mg, Ni, Co and Al in the hydrogen storage alloy include La _0.7 Mg _0.3 Ni _2.75 Co _0.5 Al _0.05 , La _0.7 Mg _0.3 Ni _2.95 Co _0.5 Al _0.05 , or La _0.7 Mg. _0.3 Ni _2.95 Co _0.3 Al _{0.05 and the} like.

  In the hydrogen storage alloy, the amount of the element M is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, or 0.2% by mass or more. The amount of the element M is 0.45% by mass or less, preferably 0.4% by mass or less, and more preferably 0.35% by mass or less. These lower limit value and upper limit value can be appropriately selected and combined. The amount of the element M may be, for example, 0.01 to 0.4 mass% or 0.2 to 0.4 mass%.

  When the amount of the element M exceeds 0.45% by mass, the capacity is reduced and many lattice defects are introduced, so that the durability of the positive electrode active material is easily lowered. descend. Moreover, when the number of lattice defects increases, the diffusibility of hydrogen in the hydrogen storage alloy decreases, and the conductivity at low temperatures decreases.

The elution of the constituent elements of the hydrogen storage alloy with respect to the alkaline electrolyte may be influenced by the crystal structure of the hydrogen storage alloy. The hydrogen storage alloy may have a crystal structure such as AB ₂ type, AB ₃ type (ie, CeNi ₃ type), AB ₅ type, A ₂ B ₇ type (ie, Ce ₂ Ni ₇ type), for example. . In the AB ₃ type and A ₂ B ₇ type hydrogen storage alloys, among the above elements, Mg and La are present at the A site, and Ni, Co, and Al are present at the B site.

Hydrogen storage alloys having AB ₃ type and A ₂ B ₇ type crystal structures are complex and relatively unstable, so when combined with an alkaline electrolyte containing a relatively large amount of potassium hydroxide, hydrogen storage alloys Elution of the constituent elements of the alloy tends to be significant. However, since an alkaline electrolyte having a specific composition is used in the present invention, even if a hydrogen storage alloy having an AB ₃ type or A ₂ B ₇ type crystal structure is used, the constituent elements of the hydrogen storage alloy Elution can be effectively suppressed.

  The hydrogen storage alloy may contain lanthanoid elements such as Pr, Nd, and Sm, Zr, and the like in addition to the above elements. The content of these other elements is 5% by mass or less of the entire hydrogen storage alloy.

  Of the elements M, Y has a strong affinity for oxygen and has the ability to reduce surrounding oxides. Therefore, in the hydrogen storage alloy containing Y in the above range, corrosion of the hydrogen storage alloy, particularly corrosion at a high temperature can be suppressed. In addition, in a hydrogen storage alloy containing Y in the above range, the constituent elements of the alloy may be replaced with Y more than necessary, the capacity may be reduced, and the durability may deteriorate due to the introduction of lattice defects. It is suppressed. Therefore, as a result, the high temperature storage characteristics can be improved more effectively.

  The reducing ability of Y can be explained by Pauling's electronegativity. Pauling's electronegativity is a measure of the tendency of atoms to attract electrons. The binding energy of an element is related to the square of the difference in Pauling electronegativity. The greater the difference in electronegativity, the greater the binding energy. The Pauling electronegativity of the elements contained in the hydrogen storage alloy is 1.2 for Y, 1.8 for Ni, 1.8 for Co, and 1.5 for Al. On the other hand, O is 3.5, and it is Y that has the largest difference from oxygen, and Y has a strong binding energy with respect to oxygen. That is, it is understood that there is a strong affinity for oxygen.

  Sn has an ability to suppress expansion and contraction when storing and releasing hydrogen. Therefore, in the hydrogen storage alloy containing Sn in the above range, especially when storing and releasing hydrogen at a high temperature, it is suppressed from expanding and contracting more than necessary, thereby suppressing the corrosion of the hydrogen storage alloy. Can do. In addition, in the hydrogen storage alloy containing Sn in the above range, it is possible to suppress the segregation of Sn excessively, and the constituent elements of the alloy are replaced with Sn more than necessary, the capacity is reduced, or lattice defects are introduced. This prevents the durability from deteriorating. Therefore, as a result, the high temperature storage characteristics can be improved more effectively.

Further, when the hydrogen storage alloy does not contain the element M, the low temperature discharge characteristics are somewhat high, but the high temperature storage characteristics are greatly deteriorated because the above-described effects due to Y and Sn cannot be obtained. When the hydrogen storage alloy contains the element M with a specific content, the high temperature storage characteristics can be improved, and the ability to suppress expansion and contraction when storing and releasing hydrogen is suppressed to a suitable range of crystal defects. can do. Therefore, when using a hydrogen storage alloy having an A ₂ B ₇ type crystal structure, it is particularly effective to contain the element M at a specific content. As a result, the diffusibility (mobility) of hydrogen in the hydrogen storage alloy is increased, so that a decrease in conductivity at a low temperature can be prevented. Therefore, when a negative electrode containing such a hydrogen storage alloy is used for an alkaline storage battery, the alkaline storage battery can be used in a wider temperature range.

The negative electrode containing the hydrogen storage alloy as described above is
(I) A first step of forming a raw material powder containing a hydrogen storage alloy having the above composition by mixing each element of the constituent elements of the hydrogen storage alloy at a predetermined ratio, alloying, and granulating. When,
(Ii) a second step in which the raw material powder is surface-treated with an alkaline aqueous solution to obtain an electrode alloy powder;
(Iii) a third step of preparing a negative electrode paste by mixing an electrode alloy powder, a conductive agent, a binder, and a dispersion medium;
(Iv) It can obtain by passing through the 4th process of forming a negative electrode by making a negative electrode paste adhere to a core material.

  The first step (i) may include an alloying step of alloying the constituent elements of the hydrogen storage alloy and alloying the constituent elements, and a granulating step of granulating the alloy.

  In the alloying process, for example, a plasma arc melting method, a high frequency melting (die casting) method, a mechanical alloying method (mechanical alloy method), a mechanical milling method, a rapid solidification method (specifically, a metal material utilization dictionary (industrial industry) Study Group, 1999), etc., roll spinning method, melt drag method, direct casting and rolling method, spinning in spinning solution, spray forming method, gas atomizing method, wet spraying method, splat method, rapid solidification strip pulverization method , Gas spray splat method, melt extraction method, spray forming method, rotating electrode method, etc.). The mechanical alloying method and the mechanical milling method are effective methods in that the size and crystal form of the hydrogen storage alloy powder can be easily controlled. In addition to the rapid solidification method alone, it can be used in combination with the mechanical alloying method.

In the alloying step, when mixing the single constituent elements, the molar ratio and mass ratio of the single constituents are adjusted so that the hydrogen storage alloy has a desired composition.
For example, when an alloy is formed by melting the mixture by a high frequency melting method or the like, after cooling and solidifying the melt, the solidified product is heat-treated in an inert gas atmosphere such as argon, and the heat-treated solidified product (alloy) is obtained. You may use for a granulation process.

The granulation of the alloy can be performed by an atomizing method in addition to pulverization. The alloy can be pulverized by wet pulverization, dry pulverization, or the like, or a combination thereof. You may classify the obtained particle | grains as needed.
The average particle diameter of the raw material powder is, for example, 5 to 50 μm, preferably 5 to 30 μm. When the average particle size is in such a range, the surface area of the hydrogen storage alloy can be maintained in an appropriate range, and more effectively, a decrease in corrosion resistance can be suppressed and a decrease in the hydrogen storage reaction can be suppressed.
In the present specification, the average particle diameter means a volume-based median diameter.

In the second step (ii), the raw material powder obtained in the first step is surface-treated with an alkaline aqueous solution.
As the alkaline aqueous solution, for example, an aqueous solution containing an alkali metal hydroxide such as KOH, NaOH, LiOH or the like as an alkali can be used. The density | concentration of the alkali in alkaline aqueous solution is 5-50 mass%, for example, Preferably it is 10-45 mass%.

The surface treatment of the raw material powder can be performed by bringing the raw material powder into contact with an alkaline aqueous solution. Specifically, the raw material powder can be brought into contact with the alkaline aqueous solution by immersing the raw material powder in an alkaline aqueous solution or spraying the alkaline aqueous solution onto the raw material powder.
The contact between the raw material powder and the alkaline aqueous solution may be performed under heating, or the heated alkaline aqueous solution may be brought into contact with the raw material powder. The temperature (atmosphere temperature or temperature of the alkaline aqueous solution) when bringing the raw material powder into contact with the alkaline aqueous solution is, for example, 50 to 100 ° C., preferably 80 to 100 ° C.

After the surface treatment with the alkaline aqueous solution, the obtained alloy powder may be washed with water. In order to reduce the remaining impurities on the surface of the alloy powder, the water washing is preferably finished after the pH of the water used for washing becomes 9 or less.
The alloy powder after the surface treatment is usually dried.

  The electrode alloy powder can sufficiently remove the oxide film on the surface of the hydrogen storage alloy through the second step. Therefore, the oxygen concentration in the electrode alloy powder is reduced. The oxide on the surface of the hydrogen storage alloy tends to be the starting point of the corrosion reaction, which may cause a decrease in capacity and elution of constituent elements. That is, the oxygen concentration in the electrode alloy powder can be used as an index of the degree of activation of the hydrogen storage alloy and the degree of inhibition of corrosion, and the smaller the value, the more the hydrogen storage alloy is activated. .

  The oxygen concentration of the electrode alloy powder can be evaluated based on, for example, a value obtained by an oxygen concentration measurement method (infrared absorption method) defined in JIS-Z-2613. This value corresponds to the amount of oxide and hydroxide deposited on the surface of the hydrogen storage alloy powder.

  In the electrode alloy powder of the present invention, the oxygen concentration based on JIS-Z-2613 is, for example, 0.9 mass% or less or 0.87 mass% or less. When the oxygen concentration is in such a range, it is more advantageous from the viewpoint of sufficiently activating the hydrogen storage alloy and suppressing corrosion. Therefore, by setting the oxygen concentration in such a range, the discharge characteristics and the storage characteristics can be further improved.

  In addition, through the second step, a magnetic material cluster (magnetic material) mainly composed of metallic nickel is formed on the surface or surface layer of the hydrogen storage alloy contained in the electrode alloy powder, whereby the hydrogen storage alloy. Is activated. The magnetic body is mainly an aggregate of Ni, and has a catalytic action for the storage and release of hydrogen. When the magnetic material is increased, when used as an electrode active material of an alkaline storage battery, the diffusion rate of hydrogen on the surface of the hydrogen storage alloy increases, and the discharge characteristics can be improved.

  The content of the magnetic substance contained in the electrode alloy powder can be measured, for example, using a vibrating sample magnetometer. Specifically, the saturation magnetization of the electrode alloy powder in a magnetic field of 10 kOe is obtained, the amount of metallic nickel (amount of magnetic material) corresponding to the saturation magnetization is obtained, and the content of the magnetic material is calculated based on this.

  The content (VSM value) of the magnetic substance contained in the electrode alloy powder is, for example, 1.6 to 2.3% by mass, preferably 1.65 to 2.2% by mass or 1.7 to 2.1% by mass. %. When the content of the magnetic material is in such a range, when the electrode alloy powder is used as an electrode active material in an alkaline storage battery, the battery reaction can be performed more efficiently and the constituent elements of the hydrogen storage alloy can be eluted. It is possible to suppress the decrease in capacity.

In the third step (iii), a negative electrode paste is prepared using the electrode alloy powder obtained in the second step.
The negative electrode paste can be prepared by mixing an electrode alloy powder, a conductive agent, a binder, and a dispersion medium. You may mix a thickener with these components as needed.

The conductive agent is not particularly limited as long as it is a material having electronic conductivity. For example, graphite such as natural graphite (flaky graphite etc.), artificial graphite and expanded graphite; carbon black such as acetylene black and ketjen black; conductive fibers such as carbon fiber and metal fiber; metal particles such as copper powder An organic conductive material such as a polyphenylene derivative can be exemplified. These conductive agents may be used alone or in combination of two or more. Of these, artificial graphite, ketjen black, carbon fiber and the like are preferable.
The quantity of a electrically conductive agent is 1-50 mass parts with respect to 100 mass parts of alloy powders for electrodes, Preferably it is 1-30 mass parts.

  The conductive agent may be added to the negative electrode paste and mixed with other components. The surface of the electrode alloy powder may be coated with a conductive agent in advance. The conductive agent is coated by a known method, for example, by coating the surface of the electrode alloy powder with a conductive agent, attaching a dispersion containing the conductive agent and drying it, or mechanically coating it by a mechanochemical method or the like. It can be done by doing.

As the binder, resin materials, for example, rubber-like materials such as styrene-butadiene copolymer rubber (SBR); polyolefin resins such as polyethylene and polypropylene; polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene Fluoropolymers such as copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers; acrylic resins such as ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl acrylate copolymers; The Na ion crosslinked body etc. can be illustrated. These binders can be used individually by 1 type or in combination of 2 or more types.
The amount of the binder is, for example, 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the electrode alloy powder.

  As the dispersion medium, known media such as water, organic media, and mixed media thereof can be used.

Examples of the thickener include carboxymethylcellulose (CMC) and modified products thereof (including salts such as Na salt), cellulose derivatives such as methylcellulose; saponified polymers having vinyl acetate units such as polyvinyl alcohol; polyethylene oxide, etc. And polyalkylene oxide. These thickeners can be used singly or in combination of two or more.
The amount of the thickener is, for example, 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the electrode alloy powder.

In the fourth step (iv), the negative electrode can be formed by attaching a negative electrode paste to the core material.
A well-known thing can be used as a negative electrode core material, The porous or non-porous board | substrate formed with stainless steel, nickel, its alloy, etc. can be illustrated. When the core material is a porous substrate, the active material may be filled in the pores of the core material.
The negative electrode can be formed by applying a negative electrode paste to a core material and then removing the dispersion medium by drying and rolling.

(Positive electrode)
The positive electrode may include a core material and an active material or an active material layer attached to the core material. The positive electrode may be an electrode obtained by sintering active material powder into a core material.
The positive electrode can be formed, for example, by attaching a positive electrode paste containing at least a positive electrode active material to a core material. The positive electrode paste usually contains a dispersion medium, and a known component used for the positive electrode, for example, a conductive agent, a binder, a thickener, and the like may be added as necessary.

The types and amounts of the dispersion medium, the conductive agent, the binder, and the thickener can be selected from the same ones or ranges as in the case of the negative electrode paste.
The positive electrode can be formed, for example, by applying a positive electrode paste to a core material, removing the dispersion medium by drying, and rolling.

A well-known thing can be used as a positive electrode core material, The porous board | substrate formed with nickel or nickel alloys, such as a nickel foam and a sintered nickel board, can be illustrated.
As the positive electrode active material, for example, nickel compounds such as nickel hydroxide and nickel oxyhydroxide are used.
As the positive electrode, a known sintered nickel positive electrode is preferably used.

(Separator)
As the separator, a microporous film or non-woven fabric made of polyolefin such as polyethylene or polypropylene can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
(1) Preparation of raw material powder Each of La, Mg, Ni, Co, and Al is mixed at a predetermined ratio, and Y is applied to a hydrogen storage alloy having a composition of La _0.7 Mg _0.3 Ni _2.75 Co _0.5 Al _0.05. What was introduced at 0.3% by mass was melted in a high-frequency melting furnace to produce an ingot. The obtained ingot was heated at 1060 ° C. for 10 hours under an argon atmosphere. The heated ingot was pulverized into coarse particles. The obtained coarse particles were pulverized in the presence of water using a wet ball mill and sieved with a sieve having a mesh diameter of 75 μm in a wet state to obtain a raw material powder containing a hydrogen storage alloy having an average particle diameter of 20 μm.

(2) Production of electrode alloy powder The raw material powder obtained in (1) above was mixed with an aqueous alkali solution containing 100% by mass of sodium hydroxide at a concentration of 40% by mass, and stirring was continued for 50 minutes. . The obtained powder was collected, washed with warm water, dehydrated and dried. Washing was performed until the pH of the hot water after use was 9 or less. As a result, an electrode alloy powder from which impurities were removed was obtained.

  It was 0.85 mass% when the oxygen concentration of the obtained alloy powder was calculated | required by the oxygen concentration measuring method prescribed | regulated to JIS-Z-2613.

  The content of the magnetic substance contained in the alloy powder was measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd., small fully automatic vibrating sample magnetometer VSM-C7-10A). Specifically, the saturation magnetization of the electrode alloy powder in a magnetic field of 10 kOe was obtained, the amount of metallic nickel corresponding to the saturation magnetization (amount of magnetic substance) was obtained, and the content of the magnetic substance was calculated based on this, The magnetic substance content was 1.8% by mass.

(3) Production of negative electrode 0.15 parts by mass of CMC (degree of etherification 0.7, degree of polymerization 1600), 0.3 parts by mass of acetylene black with respect to 100 parts by mass of the electrode alloy powder obtained in (2) above And 0.7 parts by mass of SBR were added, and water was further added and kneaded to prepare an electrode paste. The obtained electrode 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%). The coating film of the paste was pressed with a roller together with the core material after drying. Thus, a negative electrode having a thickness of 0.4 mm, a width of 35 mm, and a capacity of 2200 mAh was obtained. An exposed portion of the core material was provided at one end portion along the longitudinal direction of the negative electrode.

(4) Production of positive electrode A sintered positive electrode having a capacity of 1500 mAh obtained by filling a positive electrode core material made of a porous sintered substrate with nickel hydroxide was prepared. About 90 parts by mass of Ni (OH) ₂ is used for the positive electrode active material, about 6 parts by mass of Zn (OH) ₂ is added as an additive, and about 4 parts by mass of Co (OH) ₂ is added as a conductive material. did. An exposed portion of the core material that does not hold an active material having a width of 35 mm was provided at one end portion along the longitudinal direction of the positive electrode core material.
(5) Production of Nickel Metal Hydride Battery Using the negative electrode and the positive electrode obtained above, a nickel metal hydride battery with a 4 / 5A size and a nominal capacity of 1500 mAh as shown in FIG. 2 was produced. Specifically, the positive electrode 1 and the negative electrode 2 were wound through a separator 3 to produce a columnar electrode plate group. In the electrode plate group, the exposed portion of the positive electrode core material to which the positive electrode mixture was not attached and the exposed portion of the negative electrode core material to which the negative electrode mixture was not attached were exposed on the opposite end surfaces. For the separator 3, a nonwoven fabric made of polypropylene (thickness: 100 μm) was used. 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.

  A 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 7 and the positive electrode current collector plate were electrically connected through the positive electrode lead 9. Thereafter, the negative electrode current collector plate was turned downward, and the electrode plate group was accommodated in a battery case 4 formed of a cylindrical bottomed can. The negative electrode lead connected to the negative electrode current collector plate was welded to the bottom of the battery case 4. After injecting the electrolyte into the battery case 4, the opening of the battery case 4 was sealed with a sealing plate 7 having a gasket 8 on the periphery, thereby completing a nickel metal hydride storage battery.

  Note that an alkaline aqueous solution (specific gravity: 1.23) containing 1% by mass of KOH, 15% by mass of NaOH, and 0.1% by mass of LiOH was used as the electrolytic solution.

Examples 2-11 and Comparative Examples 1-7
A nickel-metal hydride storage battery was fabricated in the same manner as in Example 1, except that an alkaline aqueous solution in which the concentrations of KOH, NaOH, and LiOH were changed to the concentrations shown in Table 1 was used as the electrolytic solution.

Examples 12-14 and Comparative Examples 8-9
A raw material powder was obtained in the same manner as in Example 1 except that the amount of Y introduced into the hydrogen storage alloy was changed as shown in Table 2 in Example 1 (1). Except for using the obtained raw material powder, an electrode alloy powder was prepared in the same manner as in Example 1, and a negative electrode was prepared using the electrode alloy powder. A nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that this negative electrode was used.

Examples 15 to 17 and Comparative Example 10
In Example 1 (1), a raw material powder was obtained in the same manner as in Example 1 except that Sn was introduced into the hydrogen storage alloy in an introduction amount shown in Table 2 instead of Y. Except for using the obtained raw material powder, an electrode alloy powder was prepared in the same manner as in Example 1, and a negative electrode was prepared using the electrode alloy powder. A nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that this negative electrode was used.

Examples 18 and 19
In Example 1 (1), a raw material powder was obtained in the same manner as Example 1 except that Y was introduced into the hydrogen storage alloy having the composition shown in Table 3. The hydrogen storage alloy having the composition shown in Table 3 was produced by appropriately changing the ratio of each of La, Mg, Ni, Co, and Al.
Except for using the obtained raw material powder, an electrode alloy powder was prepared in the same manner as in Example 1, and a negative electrode was prepared using the electrode alloy powder. A nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that this negative electrode was used.

The following evaluation was performed about the nickel hydride storage battery obtained by the Example and the comparative example. The results are shown in Tables 1 to 3.
(Low temperature discharge characteristics)
The nickel-metal hydride battery is charged at 20 ° C. with a current value of 0.75 A until the capacity reaches 120% of the theoretical capacity, and at 20 ° C., the battery voltage drops to 1.0 V at a current value of 1.5 A. The capacity (initial discharge capacity) at this time was measured.
Furthermore, the nickel metal hydride storage battery is charged at 20 ° C. with a current value of 0.75 A until the capacity reaches 120% of the theoretical capacity, and at 0 ° C., the battery voltage becomes 1.0 V with a current value of 1.5 A. It discharged until it fell, and the capacity | capacitance at this time (low-temperature discharge capacity) was measured.
The low-temperature discharge capacity is divided by the initial discharge capacity and expressed as a percentage, and this value is used as an index of the low-temperature discharge characteristics.

(High temperature storage characteristics)
The nickel-metal hydride battery is charged at 20 ° C. with a current value of 0.15 A until the capacity reaches 160% of the theoretical capacity. At 20 ° C., the battery voltage drops to 1.0 V at a current value of 0.3 A. It discharged until it carried out, and the capacity | capacitance at this time (initial discharge capacity) was measured.
Further, the nickel metal hydride storage battery was charged at 20 ° C. with a current value of 0.15 A until the capacity reached 160% of the theoretical capacity, and stored at 45 ° C. for 2 weeks. After storage, discharge was performed at 20 ° C. with a current value of 0.3 A until the battery voltage decreased to 1.0 V, and the capacity at this time (storage remaining discharge capacity) was measured.
The storage residual discharge capacity was divided by the initial discharge capacity and expressed as a percentage, and this value was used as an index for high-temperature storage characteristics.

  As shown in Table 1, in the batteries of the examples in which the concentrations of KOH, NaOH, and LiOH in the alkaline electrolyte were adjusted to a predetermined range, the decrease in the low temperature discharge characteristics was suppressed, and the high temperature storage characteristics were high. Obtained.

  On the other hand, in Comparative Examples 1 and 2 in which the KOH concentration in the alkaline electrolyte was 0% by mass or 0.05% by mass, the low-temperature discharge characteristics were deteriorated. The reason why the low-temperature discharge characteristics were decreased is considered to be that the conductivity was decreased due to the KOH concentration being too low.

  In Comparative Example 3 where the KOH concentration was 41% by mass, both the low temperature discharge characteristics and the high temperature storage characteristics were deteriorated. The reason why the low-temperature discharge characteristics deteriorated is thought to be that the KOH concentration in the electrolytic solution became excessive and the ion movement speed decreased due to ion interference. In Comparative Example 3, the discharge characteristics deteriorated not only at a low temperature but also at a normal temperature. In Comparative Example 3, the high temperature storage characteristics were decreased because the amount of Mg eluted increased and the deterioration of the negative electrode progressed.

Further, in Comparative Examples 4 and 5 in which the NaOH concentration was 9% by mass, the low temperature discharge characteristics were deteriorated. This is presumably because the mobility of the salt in the alkaline electrolyte was lowered and the conductivity was lowered. Moreover, in the comparative example 5 whose LiOH density | concentration is 0.6 mass%, the high temperature storage characteristic also fell. This is thought to be due to the fact that due to the low NaOH concentration, the disadvantages due to the high LiOH concentration became obvious, the elution of constituent elements such as Mg contained in the hydrogen storage alloy became significant, and the corrosion reaction was promoted. .
In Comparative Example 6 in which the NaOH concentration was 31% by mass, the low-temperature discharge characteristics deteriorated due to the decrease in conductivity at low temperatures.
In Comparative Example 7 in which the LiOH concentration was 0.6% by mass, the low-temperature discharge characteristics were deteriorated.

  As shown in Table 2, in the examples in which the hydrogen storage alloy contains a predetermined amount of Y or Sn, excellent results were obtained in both low temperature discharge characteristics and high temperature storage characteristics. On the other hand, in Comparative Example 8 in which the hydrogen storage alloy did not contain any of Y and Sn, the high-temperature storage characteristics were remarkably deteriorated although the low-temperature discharge characteristics were high. When Y is included, due to the strong affinity of Y for oxygen, adjacent oxides are reduced, and corrosion of the hydrogen storage alloy is suppressed. In addition, when Sn is contained, expansion and contraction when hydrogen is occluded and released at a high temperature is suppressed, whereby corrosion of the hydrogen storage alloy is suppressed. In Comparative Example 8, since Y and Sn are not included, the effect of suppressing the corrosion of such a hydrogen storage alloy is not obtained, surface oxidation becomes remarkable, and corrosion is promoted. It is done.

In Comparative Examples 9 and 10 in which the content of Y or Sn was 0.6% by mass, the high-temperature storage characteristics were greatly deteriorated. In Comparative Example 9, when the Y content is excessively large, the capacity is reduced and many lattice defects are introduced, and the durability is lowered, so that the high-temperature storage characteristics are considered insufficient. It is done. In Comparative Example 10, since the Sn content is excessively increased, the segregation of Sn becomes significant, the capacity is reduced, and many lattice defects are introduced, resulting in a decrease in durability. It is thought that the high-temperature storage characteristics became insufficient.
In Comparative Examples 9 and 10, the low-temperature discharge characteristics were also deteriorated. This is presumably because the number of lattice defects increases, the hydrogen diffusibility in the hydrogen storage alloy decreases, and the conductivity at low temperatures decreases.

  As shown in Table 3, when using a raw material in which the molar ratio of Mg to the total of La and Mg and the molar ratio of Ni, Co and Al to the total of La and Mg are predetermined values, low temperature discharge Excellent results were obtained for both the characteristics and the high temperature storage characteristics.

  In this invention, since the low temperature discharge characteristic and high temperature storage characteristic of an alkaline storage battery can be improved, high battery characteristics can be obtained in a wide temperature range. Therefore, it can be expected to be used as a power source for various devices in addition to a substitute for a dry battery, and can also be expected to be used for a power source for a hybrid vehicle used in a harsh environment.

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Separator 4 Battery case 6 Safety valve 7 Sealing plate 8 Insulating gasket 9 Positive electrode lead

Claims (10)

A positive electrode including nickel, a negative electrode including a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte,
The hydrogen storage alloy includes La, Mg, Ni, Co, Al, and the element M;
The molar ratio x of Mg in the total of La and Mg is 0.01 ≦ x ≦ 0.5,
The molar ratio y of Ni to the sum of La and Mg is 2 ≦ y ≦ 4,
The molar ratio z of Co to the sum of La and Mg is 0.25 ≦ z ≦ 0.75,
The molar ratio α of Al to the sum of La and Mg is 0.01 ≦ α ≦ 0.06,
The element M is at least one selected from the group consisting of Y and Sn,
The amount of the element M is 0.01 to 0.4 % by mass of the hydrogen storage alloy,
The alkaline electrolyte is potassium hydroxide 0.08 to 40.2 wt%, sodium hydroxide 9.7 to 30.4 wt%, and containing 0.05 to 0.53 wt% lithium hydroxide Alkaline storage battery. In the alkaline electrolyte, the potassium hydroxide content is 0.1 to 40% by mass, the sodium hydroxide content is 10 to 30% by mass, and the lithium hydroxide content is The alkaline storage battery according to claim 1, which is 0.05 to 0.5 mass % . The alkaline storage battery according to claim 1 or 2, wherein a content of the potassium hydroxide in the alkaline electrolyte is 0.5 to 10% by mass. The alkaline storage battery according to any one of claims 1 to 3, wherein a content of the lithium hydroxide in the alkaline electrolyte is 0.1 to 0.5 mass%. The alkaline storage battery according to any one of claims 1 to 4, wherein a total content of the potassium hydroxide and a content of the sodium hydroxide in the alkaline electrolyte is 10.5% by mass or more. The content of the potassium hydroxide, the content of the sodium hydroxide, and the content of the lithium hydroxide in the alkaline electrolyte are as follows:
The alkaline storage battery according to claim 1, wherein the content of lithium hydroxide <the content of potassium hydroxide <the content of sodium hydroxide is indicated. The alkaline storage battery according to any one of claims 1 to 6 , wherein an amount of the element M is 0.2 to 0.4 mass% of the hydrogen storage alloy. In the hydrogen storage alloy, the molar ratio x of Mg is 0.1 ≦ x ≦ 0.4, the molar ratio y of Ni is 2.5 ≦ y ≦ 3.5, and the molar ratio of Co the ratio z is 0.25 ≦ z ≦ 0.75, wherein the molar ratio alpha of Al, which is 0.03 ≦ α ≦ 0.055, alkali according to any one of claims 1-7 Storage battery. In the hydrogen-absorbing alloy, the molar ratio x of said Mg is 0.25 ≦ x ≦ 0.35, the alkaline storage battery according to any one of claims 1-8. The hydrogen storage alloy has a crystal structure of type ₃ or Ce ₂ Ni ₇ type CeNi, alkaline storage battery according to any one of claims 1-9.

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