JP2008059818A - Alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery in which a hydrogen storage alloy used for an anode is improved and a melting out of cobalt or the like from the hydrogen storage alloy when kept unused for a long period is prevented and a preservation property is improved. <P>SOLUTION: In the alkaline storage battery provided with a cathode, an anode made of hydrogen storage alloy, a separator and alkaline electrolyte solution, the anode is made of hydrogen storage alloy as shown in a general formula and an La content in Ln is 85 mol% or less against a total Ln: Ln<SB>1-x</SB>Mg<SB>x</SB>Ni<SB>y-a-b</SB>Co<SB>a</SB>M<SB>b</SB>(wherein, Ln is at least one kind of element selected from rare earth elements including Zr, Ti, and Y, and M is at least one element selected from V, Nb, Ta, Cr, Mo, Mn, Fe, Al, Ga, Zn, Sn, In, Cu, Si, P, and B, satisfying conditions of 0.05≤x≤0.30, 0.05≤a≤0.30, 0≤b≤0.50 and 2.8≤y≤3.9), and a separator with a sulfone group is used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an alkaline storage battery comprising a positive electrode, a negative electrode using a hydrogen storage alloy, a separator provided between the positive electrode and the negative electrode, and an alkaline electrolyte, improving the hydrogen storage alloy used for the negative electrode, In particular, the alkaline storage battery using a separator having a sulfone group is characterized in that the storage characteristics are improved.

  Conventionally, nickel-cadmium storage batteries have been widely used as alkaline storage batteries, but in recent years they have a higher capacity than nickel-cadmium storage batteries and are superior in environmental safety because they do not use cadmium. Therefore, nickel-hydrogen storage batteries using a hydrogen storage alloy for the negative electrode have come to attract attention.

  In recent years, alkaline storage batteries composed of such nickel-hydrogen storage batteries have come to be used for applications such as hybrid vehicles and power tools, and have higher capacity and excellent high-rate charge / discharge characteristics. There has been a strong demand for alkaline storage batteries.

Here, in such an alkaline storage battery, the hydrogen storage alloy used for the negative electrode generally includes a rare earth-nickel hydrogen storage alloy whose main phase is a CaCu ₅ type crystal, Ti, Zr, V and Ni. Hydrogen storage alloys, etc., mainly composed of Laves phase AB ₂ type crystals are generally used. However, these hydrogen storage alloys do not necessarily have sufficient hydrogen storage capacity, and have higher capacities. It was difficult to obtain an alkaline storage battery.

  In recent years, in order to improve the hydrogen storage capability in the rare earth-nickel hydrogen storage alloy, a hydrogen storage alloy in which a part of the rare earth element in the rare earth-nickel hydrogen storage alloy is replaced with Mg or the like. It has been proposed to use an alkaline storage battery (see, for example, Patent Document 1).

  Here, the hydrogen storage alloy in which a part of the rare earth element in the rare earth-nickel-based hydrogen storage alloy is replaced with Mg or the like is prone to cracking, and a new highly reactive surface appears due to the crack, resulting in a discharge reaction. However, the corrosion resistance decreases due to such cracks, and in the case of an alkaline storage battery using such a hydrogen storage alloy, a sufficient cycle life is obtained. There was a problem that it could not be obtained.

  For this reason, in recent years, a proposal has been made to improve the corrosion resistance of hydrogen storage alloys by optimizing the composition of hydrogen storage alloys in which a part of the rare earth elements as described above is substituted with Mg or the like. (For example, refer to Patent Document 2).

  However, even in the alkaline storage battery using the hydrogen storage alloy as described above, when left for a long time, the surface of the hydrogen storage alloy is corroded, and Co and rare earth elements in the hydrogen storage alloy gradually elute, There was a problem that the characteristics deteriorated.

  Further, conventionally, a separator provided with a sulfone group as an ion exchange group is used as a separator of an alkaline storage battery, and transition metal ions eluted from the negative electrode or the positive electrode are trapped in the separator to prevent self-discharge. What has been proposed has been proposed (see, for example, Patent Document 3).

However, when such a sulfone-grouped separator is used for the alkaline storage battery using the hydrogen storage alloy as described above, Co and rare earth elements eluted from the hydrogen storage alloy are deposited on the separator, There still remained the problem that sufficient storage properties could not be obtained.
JP-A-11-323469 JP 2001-316744 A Japanese Patent Laid-Open No. 10-50291

  This invention makes it a subject to solve the above problems in the alkaline storage battery provided with the positive electrode, the negative electrode using a hydrogen storage alloy, the separator provided between a positive electrode and a negative electrode, and an alkaline electrolyte. When the hydrogen storage alloy used for the negative electrode is improved and left for a long period of time, it is suppressed that Co and rare earth elements are eluted from the hydrogen storage alloy, and the eluted Co and rare earth elements have a sulfone group. It is an object of the present invention to prevent the precipitation on the separator and to obtain an alkaline storage battery having excellent storage characteristics.

In the alkaline storage battery according to the present invention, in order to solve the above-described problems, the alkaline storage battery includes a positive electrode, a negative electrode using a hydrogen storage alloy, a separator provided between the positive electrode and the negative electrode, and an alkaline electrolyte. in, the negative electrode described above, in the general formula _{Ln 1-x Mg x Ni yab} Co a M b ( wherein, Ln at least one element is selected from rare earth elements including Zr, Ti, and Y, M of V, Nb, Ta, Cr, Mo, Mn, Fe, Al, Ga, Zn, Sn, ln, Cu, Si, P, and at least one element selected from B, 0.05 ≦ x ≦ 0.30, 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ 0.50, 2.8 ≦ y ≦ 3.9.), And the content of La in the above Ln is the total amount of Ln And using a hydrogen storage alloy of 85 mol% or less based on And to use a separator having a sulfone group.

  Here, in the alkaline storage battery according to the present invention, in the hydrogen storage alloy represented by the above general formula, the content of La in the above Ln is preferably 49 mol% or less with respect to the total amount of Ln. It is preferable to contain at least one element of Sm and Gd in the above Ln, and the total content of these Sm and Gd is preferably 10 mol% or more of the total rare earth elements.

  In addition, in the negative electrode using the hydrogen storage alloy as described above, a hydrophilic polymer such as polyvinyl alcohol, polyvinyl pyrrolidone, or polyethylene oxide is applied to the surface, and the hydrophilic polymer thus applied is used to remove the hydrogen storage alloy from the hydrogen storage alloy. It is preferable to prevent the eluted Co and the like from diffusing and to suppress the separator from folding out.

  Further, in obtaining the above-mentioned separator having a sulfone group, the separator is fluorinated with fluorinated gas and sulfurous acid gas to give a sulfone group, or the separator is given a sulfone group with fuming sulfuric acid. can do.

In the alkaline storage battery in the present invention, as the hydrogen storage alloy in its negative electrode is represented by the general formula _{Ln 1-x Mg x Ni yab} Co a M b, the content of La in the Ln is the total amount of Ln Since the one having a content of 85 mol% or less was used, the oxidation resistance of the hydrogen storage alloy was improved as compared with the hydrogen storage alloy in which the La content in Ln exceeded 85 mol%. In addition, the elution of alloy components such as Co from this hydrogen storage alloy is suppressed, and when a hydrogen storage alloy having a La content in Ln of 49 mol% or less is used, the alloy components such as Co are eluted. This is further suppressed.

  As a result, in the alkaline storage battery according to the present invention, alloy components such as Co eluted from the hydrogen storage alloy are suppressed from being deposited on the separator having the sulfone group, and the transition metal ions eluted from the negative electrode and the positive electrode by the separator. Is appropriately trapped and self-discharge is prevented, and the storage characteristics of the alkaline storage battery are greatly improved.

  In addition, when Sm is contained in Ln in the above hydrogen storage alloy, the oxidation resistance of the hydrogen storage alloy is improved, and pulverization of the hydrogen storage alloy is suppressed, and Gd is contained in Ln. As a result, the pulverization of the hydrogen storage alloy is suppressed, which further suppresses the elution of alloy components such as Co from the hydrogen storage alloy, thereby further improving the storage characteristics of the alkaline storage battery.

  Hereinafter, the alkaline storage battery according to the embodiment of the present invention will be specifically described, and a comparative example will be given to clarify that the storage characteristics of the alkaline storage battery according to the embodiment of the present invention are improved. In addition, the alkaline storage battery in this invention is not limited to what was shown to the following Example, In the range which does not change the summary, it can implement suitably.

(Example 1)
In Example 1, when preparing a hydrogen storage alloy used for the negative electrode, the rare earth elements La, Pr, and Nd, Zr, Mg, Ni, Al, and Co are made to have a predetermined alloy composition. This was mixed and melted in a high frequency induction melting furnace, and then cooled to obtain a hydrogen storage alloy ingot.

Then, the hydrogen storage alloy ingot was heat treated in an inert atmosphere at 1000 ° C. for 10 hours to homogenize, and then the hydrogen storage alloy ingot was mechanically pulverized in an inert atmosphere and classified. Thus, a powder of a hydrogen storage alloy having a composition of La _0.39 Pr _0.30 Nd _0.10 Zr _0.01 Mg _0.20 Ni _3.20 Al _0.10 Co _0.10 was obtained. The composition of the above hydrogen storage alloy was measured by inductively coupled plasma spectroscopy (ICP). As a result of measuring the particle size distribution of the hydrogen storage alloy powder using a laser diffraction / scattering particle size distribution measuring apparatus, the average particle size at a weight integral of 50% was 65 μm.

Here, in this hydrogen storage alloy, in Ln (at least one element selected from rare earth elements including Zr, Ti, Y) in the above general formula Ln _1-x Mg _x Ni _yab Co _a M _b The La content (La / Ln) was 49 mol% as shown in Table 1 below.

Further, the hydrogen storage alloy powder thus obtained was subjected to X-ray diffraction measurement using an X-ray diffractometer using a Cu-Kα tube as an X-ray source. Has a strong peak in the range of 31 ° to 34 °, and had a crystal structure different from the CaCu ₅ type.

  Then, with respect to 100 parts by mass of the hydrogen storage alloy powder, 0.5 parts by mass of polyethylene oxide, 0.5 parts by mass of polyvinylpyrrolidone, and 20 parts by mass of water are added as binders. A slurry was prepared by kneading. And this slurry was apply | coated uniformly on both surfaces of the nickel plating punching metal of a negative electrode support body, this was dried and rolled, Then, this was cut | disconnected to the predetermined dimension, and the negative electrode was produced.

  In preparing the positive electrode, nickel hydroxide powder containing 2.5% by mass of zinc and 1.0% by mass of cobalt was charged into an aqueous cobalt sulfate solution, and the mixture was stirred at 1 mol / liter. An aqueous solution of sodium hydroxide was added dropwise, and the reaction was allowed to stir while adjusting the pH to 11. Then, the formed precipitate was filtered off, washed with water, and dried in vacuum to obtain the surface of the above nickel hydroxide particles. A coating layer of 5% by weight cobalt hydroxide was formed on the substrate.

  Next, the nickel hydroxide powder thus formed with the cobalt hydroxide coating layer and a 25 wt% aqueous sodium hydroxide solution were mixed at a mass ratio of 1:10, and the mixture was stirred at a temperature of 80 ° C. After heat treatment for 8 hours, this was washed with water and dried at 65 ° C. to obtain a powder of a positive electrode active material in which a coating layer made of a sodium-containing cobalt compound was formed on the surface of nickel hydroxide particles.

In addition, 95 parts by mass of the positive electrode active material powder, 3 parts by mass of zinc oxide, and 2 parts by mass of cobalt hydroxide were mixed with 50 parts by mass of a 0.2% by mass hydroxypropylcellulose aqueous solution. In addition, these were mixed to prepare a slurry, and this slurry was filled in a nickel foam having a basis weight of about 600 g / m ² , a porosity of 95% and a thickness of about 2 mm, dried and pressed, A positive electrode made of a non-sintered nickel electrode was produced by cutting to a predetermined dimension.

  Further, as the separator, a polypropylene non-woven fabric which is fluorinated with fluorinated gas and sulfurous acid gas to give a sulfone group is used. As the alkaline electrolyte, KOH, NaOH and LiOH are 15: 2. An alkaline storage battery having a cylindrical shape as shown in FIG. 1 was prepared using an alkaline electrolyte containing a mass ratio of 1 and a specific gravity of 1.30.

  Here, in producing the alkaline storage battery, as shown in FIG. 1, a separator 3 is interposed between the positive electrode 1 and the negative electrode 2, and these are spirally wound and accommodated in a battery can 4. The positive electrode 1 is connected to the positive electrode lid 6 via the positive electrode lead 5, and the negative electrode 2 is connected to the battery can 4 via the negative electrode lead 7, and an alkaline electrolyte is injected into the battery can 4. The battery can 4 and the positive electrode lid 6 were sealed via an insulating packing 8, and the battery can 4 and the positive electrode lid 6 were electrically separated by the insulating packing 8. Further, a closing plate 11 urged by a coil spring 10 is provided between the positive electrode cover 6 and the positive electrode external terminal 9 so as to close the gas discharge port 6a provided in the positive electrode cover 6, and the battery When the internal pressure of the battery rises abnormally, the coil spring 10 is compressed so that the gas inside the battery is released into the atmosphere.

(Example 2)
In Example 2, in preparing a hydrogen storage alloy used for the negative electrode, the rare earth elements La, Pr, and Nd, Zr, Mg, Ni, Al, and Co are made to have a predetermined alloy composition. In the same manner as in Example 1 above, the hydrogen storage alloy powder having the average particle size of 65 μm and the composition of La _0.49 Pr _0.15 Nd _0.15 Zr _0.01 Mg _0.20 Ni _3.20 Al _0.10 Co _0.10 Got. In this hydrogen storage alloy, the La content (La / Ln) in the above Ln is 61 mol% as shown in Table 1 below, and the X-ray diffraction measurement results are as follows. Like the hydrogen storage alloy of Example 1, the crystal structure was different from that of the CaCu ₅ type.

  And the alkaline storage battery of Example 2 was produced like the case of said Example 1 except using the powder of the hydrogen storage alloy obtained in this way.

(Example 3)
In Example 3, in preparing a hydrogen storage alloy used for the negative electrode, the rare earth elements La and Pr, Zr, Mg, Ni, Al, and Co were mixed so as to have a predetermined alloy composition. In the same manner as in Example 1, a hydrogen storage alloy powder having an average particle size of 65 μm and a composition of La _0.54 Pr _0.20 Zr _0.01 Mg _0.25 Ni _3.15 Al _0.15 Co _0.10 was obtained. In this hydrogen storage alloy, the La content (La / Ln) in the above Ln is 72 mol% as shown in Table 1 below, and the X-ray diffraction measurement results are as follows. Like the hydrogen storage alloy of Example 1, the crystal structure was different from that of the CaCu ₅ type.

  And the alkaline storage battery of Example 3 was produced like the case of said Example 1 except using the powder of the hydrogen storage alloy obtained in this way.

Example 4
In Example 4, in preparing a hydrogen storage alloy used for the negative electrode, the rare earth elements La and Sm, Zr, Mg, Ni, Al, and Co were mixed so as to have a predetermined alloy composition. In the same manner as in Example 1, a hydrogen storage alloy powder having an average particle size of 65 μm and a composition of La _0.64 Sm _0.10 Zr _0.01 Mg _0.25 Ni _3.20 Al _0.10 Co _0.10 was obtained. In this hydrogen storage alloy, the La content (La / Ln) in the above Ln is 85 mol% as shown in Table 1 below, and the X-ray diffraction measurement results are as follows. Like the hydrogen storage alloy of Example 1, the crystal structure was different from that of the CaCu ₅ type.

  And the alkaline storage battery of Example 4 was produced like the case of said Example 1 except using the powder of the hydrogen storage alloy obtained in this way.

(Example 5)
In Example 5, in preparing a hydrogen storage alloy used for the negative electrode, the rare earth elements La and Gd, Zr, Mg, Ni, Al, and Co were mixed so as to have a predetermined alloy composition. In the same manner as in Example 1, a hydrogen storage alloy powder having an average particle size of 65 μm and a composition of La _0.64 Gd _0.10 Zr _0.01 Mg _0.25 Ni _3.20 Al _0.10 Co _0.10 was obtained. In this hydrogen storage alloy, the La content (La / Ln) in the above Ln is 85 mol% as shown in Table 1 below, and the X-ray diffraction measurement results are as follows. Like the hydrogen storage alloy of Example 1, the crystal structure was different from that of the CaCu ₅ type.

  And the alkaline storage battery of Example 5 was produced like the case of said Example 1 except using the powder of the hydrogen storage alloy obtained in this way.

(Comparative Example 1)
In Comparative Example 1, in preparing the hydrogen storage alloy used for the negative electrode, the rare earth elements La, Zr, Mg, Ni, Al, and Co were mixed so as to have a predetermined alloy composition. In the same manner as in Example 1, a hydrogen storage alloy powder having an average particle size of 65 μm and a composition of La _0.79 Zr _0.01 Mg _0.20 Ni _3.20 Al _0.10 Co _0.10 was obtained. In this hydrogen storage alloy, the La content (La / Ln) in the above Ln is 99 mol% as shown in Table 1 below, and the X-ray diffraction measurement results are as follows. Like the hydrogen storage alloy of Example 1, the crystal structure was different from that of the CaCu ₅ type.

  And the alkaline storage battery of the comparative example 1 was produced like the case of said Example 1 except using the powder of the hydrogen storage alloy obtained in this way.

  Next, each of the alkaline storage batteries of Examples 1 to 5 and Comparative Example 1 manufactured as described above was charged at a current of 150 mA for 16 hours under a temperature condition of 25 ° C., and then the battery voltage was adjusted to a current of 1500 mA. It discharged until it became 1.0V, this was made into 1 cycle, charging / discharging of 3 cycles was performed, and each alkaline storage battery was activated.

  Then, each of the alkaline storage batteries of Examples 1 to 5 and Comparative Example 1 activated as described above was subjected to a temperature of 25 ° C., and the battery voltage reached a maximum value at a current of 1500 mA until the battery voltage decreased by 10 mV. Then, the battery was discharged at a current of 1500 mA until the battery voltage reached 1.0 V, and the discharge capacity Qo before being left standing was measured.

Next, each alkaline storage battery is charged in such a manner that the battery voltage reaches a maximum value at a current of 1500 mA at a temperature condition of 25 ° C. as described above until the voltage decreases by 10 mV. After being allowed to stand at 60 ° C. for 2 weeks, each alkaline storage battery is discharged at a current of 1500 mAh until the battery voltage reaches 1.0 V at a temperature of 25 ° C. The capacity Qa was measured, the capacity remaining rate after being left in each alkaline storage battery was determined by the following formula, and the results are shown in Table 1 below.
Capacity remaining rate (%) = (Qa / Qo) × 100

  As a result, in the alkaline storage battery of Comparative Example 1 in which the content of La in Ln exceeded 85 mol%, the residual capacity rate after standing was 0%, whereas the content of La in Ln In each of the alkaline storage batteries of Examples 1 to 5 in which the amount was 85 mol% or less, the capacity remaining rate after being left was greatly improved.

  In particular, in the alkaline storage battery of Example 1 in which the content of La in Ln is 49 mol% or less, the capacity remaining rate after being allowed to stand is further greatly improved. In each of the alkaline storage batteries of Examples 4 and 5 containing Gd and Gd, although the La content in Ln is as high as 85 mol%, the capacity remaining rate after being left is greatly improved. Was.

It is a schematic sectional drawing of the alkaline storage battery produced in the Example and comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery can 5 Positive electrode lead 6 Positive electrode cover 6a Gas discharge port 7 Negative electrode lead 8 Insulation packing 9 Positive electrode external terminal 10 Coil spring 11 Closure board

Claims (4)

In an alkaline storage battery including a positive electrode, a negative electrode using a hydrogen storage alloy, a separator provided between the positive electrode and the negative electrode, and an alkaline electrolyte, the negative electrode includes the general formula Ln _1-x Mg _x Ni _yab Co _a M _b (wherein Ln is at least one element selected from rare earth elements including Zr, Ti, Y, M is V, Nb, Ta, Cr, Mo, Mn, Fe, Al, Ga, Zn, At least one element selected from Sn, ln, Cu, Si, P, and B, 0.05 ≦ x ≦ 0.30, 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ 0.50 2.8 ≦ y ≦ 3.9), and a hydrogen storage alloy having a La content in Ln of 85 mol% or less with respect to the total amount of Ln is used. An alkaline storage battery using a separator having a group.   The alkaline storage battery according to claim 1, wherein the content of La in the Ln is 49 mol% or less with respect to the total amount of Ln.   The alkaline storage battery according to claim 1 or 2, wherein at least one element of Sm and Gd is contained in the Ln.   The alkaline storage battery according to claim 3, wherein the total content of Sm and Gd in the Ln is 10 mol% or more of the total rare earth elements.

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