JP2012238565A - Alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline storage battery having excellent initial output characteristics and high endurance so that the output drop during enduring can be inhibited.SOLUTION: An alkaline storage battery 10 in accordance with an embodiment of the present invention comprises an electrode group comprising a negative electrode 12 containing a hydrogen absorbing alloy as a negative electrode active material, a positive electrode 11 containing nickel hydroxide as a main positive electrode active material, and a separator 13 separating the negative electrode and the positive electrode, and an alkaline electrolytic solution in an outer can 16. The hydrogen absorbing alloy is represented by the formula: LnMgNiAlM, where Ln represents at least one kind of element selected from rare earth elements including Y, and Zr and Ti, M represents at least one kind of element selected from V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P, and B, 0.05≤x≤0.30, 0.05≤a≤0.30, 0≤b≤0.50, and 2.8≤y≤3.9. The positive electrode 11 contains niobium (Nb).

Description

  The present invention relates to an alkaline storage battery suitable for high output applications such as a hybrid vehicle (HEV), and in particular, a sintered nickel positive electrode using nickel hydroxide as a main positive electrode active material and a hydrogen storage alloy as a negative electrode active material. The present invention relates to an alkaline storage battery provided with an electrode group composed of a hydrogen storage alloy negative electrode and a separator for separating these hydrogen storage alloy negative electrode and sintered nickel positive electrode together with an alkaline electrolyte in an outer can.

In recent years, the use of secondary batteries has expanded, and has come to be used over a wide range such as mobile phones, personal computers, electric tools, hybrid vehicles (HEV), and electric vehicles (PEV). Among these, in particular, alkaline storage batteries have been used in high output applications such as hybrid vehicles (HEV), and many technical developments related to high output have been made. Here, as the hydrogen storage alloy used for the negative electrode of the alkaline storage battery, an AB ₅ type structure has been used. However, the use of hydrogen-absorbing alloy of this AB ₅ type structure in the negative electrode, it is impossible to ensure sufficient initial output characteristics, and the post-durability was repeatedly charged and discharged at high rate, the AB ₅ type structure of the anode Co and Mn contained in the hydrogen storage alloy were eluted to form a Co—Mn oxide having conductivity, and the short circuit was caused by being interposed in the separator.

Therefore, the general formula is Ln _lx Mg _x Ni _yab Al _a M _b (where Ln is at least one element selected from rare earth elements including Y, Zr and Ti, and M is V, Nb , Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P, and B). Became to be suppressed. On the other hand, in order to increase the output required for HEV applications, by increasing the equilibrium pressure and increasing the stoichiometric ratio, the content of nickel (Ni) in the hydrogen storage alloy is improved and the reaction is performed. Methods for reducing the resistance are proposed in Patent Document 1 (Japanese Patent Laid-Open No. 2008-300108), Patent Document 2 (Japanese Patent Laid-Open No. 2009-054514), Patent Document 3 (Japanese Patent Laid-Open No. 2009-087431), and the like. It came to be.

JP 2008-300108 A JP 2009-054514 A JP 2009-07631 A

Here, as proposed in Patent Documents 1 to 3 described above, by using a hydrogen storage alloy expressed as Ln _lx Mg _x Ni _yab Al _a M _b , the output characteristics at the initial stage are improved to some extent. In addition, it is possible to suppress short-circuiting after endurance after repeated charge and discharge at a high rate.
However, when a hydrogen storage alloy expressed as Ln _lx Mg _x Ni _yab Al _a M _b is used, the charge voltage increases due to the migration of magnesium (Mg) to the nickel positive electrode, and oxygen generation is likely to occur. A new problem has arisen that the charging characteristics deteriorate. In addition, since oxygen generation is likely to occur, a new problem has arisen in that the hydrogen storage alloy deteriorates after the endurance of repeated charge and discharge at a high rate, resulting in a decrease in output characteristics.

  Therefore, the present invention has been made to solve the above-described problems, and provides a highly durable alkaline storage battery that can improve initial output characteristics and suppress a decrease in output characteristics after durability. It was made for the purpose.

The alkaline storage battery of the present invention includes a hydrogen storage alloy negative electrode using a hydrogen storage alloy as a negative electrode active material, a sintered nickel positive electrode using nickel hydroxide as a main positive electrode active material, and these hydrogen storage alloy negative electrode and sintered nickel. An electrode group consisting of a separator that separates the positive electrode is provided in an outer can together with an alkaline electrolyte. In order to achieve the above object, the hydrogen storage alloy used for the hydrogen storage alloy negative electrode has a general formula of Ln _lx Mg _x Ni _yab Al _a M _b (where Ln is a rare earth element including Y and Zr). And at least one element selected from Ti, and M is at least one element selected from V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P, and B And is expressed as 0.05 ≦ x ≦ 0.30, 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ 0.50, 2.8 ≦ y ≦ 3.9), The sintered nickel positive electrode contains niobium (Nb).

Here, the general formula is Ln _lx Mg _x Ni _yab Al _a M _b (where Ln is at least one element selected from rare earth elements including Y, Zr and Ti, and M is V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P, and B), and 0.05 ≦ x ≦ 0.30 , 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ 0.50, 2.8 ≦ y ≦ 3.9, when a hydrogen storage alloy satisfying the following conditions is used for the hydrogen storage alloy negative electrode, magnesium in the hydrogen storage alloy Since (Mg) moves to the sintered nickel positive electrode, the charging voltage is increased and oxygen generation is likely to occur, so that the high-temperature charging characteristics are likely to be deteriorated. In addition, since oxygen generation is likely to occur, the hydrogen storage alloy deteriorates after the endurance of repeated partial charge and discharge at a high rate, and the output performance decreases.

  For this reason, in the present invention, the sintered nickel positive electrode contains niobium (Nb). When niobium (Nb) is present in the sintered nickel positive electrode in this way, when the magnesium (Mg) eluted from the hydrogen storage alloy negative electrode reaches the sintered nickel positive electrode, niobium ( Nb) easily moves into the sintered nickel positive electrode (in the active material layer). Thereby, it is estimated that the position where niobium (Nb) was present on the positive electrode surface becomes a porous body that improves the reaction area, the reaction resistance is reduced, and the output characteristics are improved. Moreover, it is estimated that niobium (Nb) moves from the positive electrode surface to the inside of the positive electrode (in the active material layer), and as a result, generation of oxygen is suppressed and deterioration of high-temperature charging characteristics is suppressed. In addition, it is presumed that the generation of oxygen during the cycle is suppressed, and the decrease in output after endurance after repeated charge and discharge at a high rate can be suppressed. In addition, it is preferable to use La, Nd, Sm, and Y, which are rare in the hydrogen storage alloy composition, have abundant resources, are inexpensive, and have small characteristic variations.

  In this case, the content of niobium (Nb) contained in the sintered nickel positive electrode is preferably 0.2% by mass or more with respect to the mass of metallic nickel (Ni) in the positive electrode active material. As a method for incorporating niobium (Nb) into the sintered nickel positive electrode, the sintered nickel positive electrode filled with the main positive electrode active material made of nickel hydroxide is immersed in an aqueous alkaline solution containing niobium (Nb). Or using a separator on which niobium (Nb) is previously supported, niobium (Nb) is dissolved in the electrolyte from the separator in the battery, and the dissolved niobium (Nb) is applied to the surface of the sintered nickel positive electrode. It is desirable that it is obtained by a moving method.

Here, the method of immersing in an alkaline aqueous solution has an advantage that it is easy to increase the content of niobium (Nb) or to control the content. On the other hand, the method of dissolving in the electrolytic solution from the separator has the merit that no significant change in the production process is required, but it has a demerit if the effect is smaller than the direct application to the positive electrode. Therefore, in this case, it is desirable to reduce the content of magnesium (Mg) in the hydrogen storage alloy of the negative electrode, and when the hydrogen storage alloy is represented by the general formula Ln _lx Mg _x Ni _yab Al _a M _b , The content is preferably in the range of 0.05 ≦ x ≦ 0.30, preferably in the range of 0.09 ≦ x ≦ 0.13.

  In addition, when there is too much content of niobium (Nb), battery capacity will fall, and it will raise C resistance in large current charging / discharging, and will cause resistance increase. For this reason, the content of niobium (Nb) is desirably 5.0% by mass or less with respect to the mass of metallic nickel (Ni) in the positive electrode active material at the maximum. Furthermore, when tungsten (W) is contained in the alkaline electrolyte, tungsten (W) moves to the surface of the sintered nickel positive electrode after the endurance of the battery, and oxygen generation is suppressed. .

  In the present invention, since the sintered nickel positive electrode contains niobium (Nb), it is possible to improve output characteristics at the initial stage of charge / discharge and to suppress generation of oxygen. As a result, a decrease in output after endurance after repeated charge and discharge at a high rate is suppressed, and a highly durable alkaline storage battery can be provided.

It is sectional drawing which shows typically the nickel-hydrogen storage battery of this invention.

  Next, embodiments of the present invention will be described in detail below. However, the present invention is not limited to these embodiments, and can be appropriately modified and implemented without departing from the scope of the present invention.

1. Sintered Nickel Positive Electrode Sintered nickel positive electrode 11 is formed by filling nickel hydroxide, cobalt hydroxide, and zinc hydroxide into a predetermined amount of pores in a nickel sintered substrate serving as a substrate. ing.
In this case, a nickel sintered substrate manufactured as follows is used. That is, a nickel slurry was prepared by mixing and kneading methyl cellulose (MC) as a thickener, polymer hollow microspheres (for example, those having a pore diameter of 60 μm), and water with nickel powder.
Next, after applying nickel slurry on both sides of the punched metal made of nickel-plated steel sheet, heating at 1000 ° C. in a reducing atmosphere causes the thickener and polymer hollow microspheres to disappear and the nickel powders to It was produced by sintering. In addition, when the porosity of the produced nickel sintered substrate was measured with a mercury intrusion porosimeter (Pascal 140 manufactured by Faisons Instruments), it was found that the porosity was 85%.

  Then, by impregnating the obtained nickel-sintered substrate into the impregnating liquid as described below and alkali treatment with the alkali-treating liquid a predetermined number of times, a predetermined amount of hydroxylation is introduced into the pores of the nickel-sintered substrate. Filled with nickel, cobalt hydroxide and zinc hydroxide. Thereafter, the sintered nickel positive electrode 11 filled with the positive electrode active material was produced by cutting into a predetermined size. In this case, as the impregnating liquid, an impregnating liquid prepared by mixing nickel nitrate, cobalt nitrate, and zinc nitrate in a molar ratio of 100: 15: 5 so as to have a specific gravity of 1.8 was used. Further, as the alkali treatment liquid, a sodium hydroxide (NaOH) aqueous solution having a specific gravity of 1.3 was used.

  In this case, first, the nickel sintered substrate is immersed in the impregnating solution, the impregnating solution is impregnated in the pores of the nickel sintered substrate, and then dried, and then immersed in the alkali processing solution to perform the alkali treatment. It was. Thereby, nickel salt, cobalt salt, and zinc salt were converted into nickel hydroxide, cobalt hydroxide, and zinc hydroxide. Thereafter, the substrate was sufficiently washed with water to remove the alkaline solution and then dried. A series of positive electrode active material filling operations such as impregnation with an impregnation solution, drying, immersion in an alkali treatment solution, washing with water, and drying are repeated six times, whereby a predetermined amount of the positive electrode active material is applied to the nickel sintered substrate. It will be filled.

Next, an alkaline aqueous solution in which niobium oxide (Nb ₂ O ₅ ) powder was added to a potassium hydroxide (KOH) aqueous solution heated to a liquid temperature of 70 ° C. was prepared. Subsequently, the sintered nickel positive electrode 11 in which a predetermined amount of the positive electrode active material was filled in the nickel sintered substrate as described above was immersed in an alkaline aqueous solution to which niobium oxide (Nb ₂ O ₅ ) powder was added. Thus, after niobium (Nb) is slightly dissolved in the alkaline aqueous solution, the niobium (Nb) is deposited on the sintered nickel positive electrode 11 and dried, so that the sintered nickel positive electrode a, b containing niobium (Nb) is dried. Was made.

In this case, the content of niobium (Nb) is 0.1% by mass with respect to the mass of metallic nickel (Ni) in the positive electrode active material as a sintered nickel positive electrode a, and the content of niobium (Nb) is The sintered nickel positive electrode b was 0.2% by mass relative to the mass of metallic nickel (Ni) in the positive electrode active material. Here, the content of niobium (Nb) was controlled by changing the immersion time in the alkaline aqueous solution. A sintered nickel positive electrode x was obtained by using the obtained sintered nickel positive electrode 11 as it was without being immersed in an alkaline aqueous solution to which niobium oxide (Nb ₂ O ₅ ) powder was added.

2. Hydrogen Storage Alloy Negative Electrode First, a hydrogen storage alloy was prepared as follows. In this case, an element represented by Ln which is at least one element selected from rare earth elements including Y, Zr, and Ti (in this case, neodymium (Nd)), magnesium (Mg), nickel (Ni), and aluminum (Al) were mixed at a predetermined molar ratio, the mixture is dissolved in an argon gas atmosphere, which is expressed as Nd _0.9 Mg _0.1 Ni _3.3 Al _0.2 was melt-quenching An ingot of a hydrogen storage alloy was prepared.

Next, the obtained hydrogen storage alloy ingot is heat-treated at a temperature lower by 30 ° C. than the melting point for a predetermined time (in this case, 10 hours) in an argon atmosphere, and is identified as an A ₂ B ₇ type structure. A hydrogen storage alloy was obtained.

Subsequently, this hydrogen storage alloy was mechanically pulverized in an inert atmosphere to obtain a hydrogen storage alloy powder of Nd _0.9 Mg _0.1 Ni _3.3 Al _0.2 . When the particle size distribution was measured with a laser diffraction / scattering type particle size distribution measuring device, the average particle size corresponding to 50% of the mass integral was 25 μm. This was used as a hydrogen storage alloy powder. Thereafter, 0.5 parts by mass of SBR (styrene butadiene latex) as a water-insoluble polymer binder and 100 parts by mass of CMC (carboxymethyl cellulose) as a thickener with respect to 100 parts by mass of the obtained hydrogen storage alloy powder. 0.03 part by mass, 0.5 part by mass of carbon black as an additive, and an appropriate amount of water (or pure water) were added and kneaded to prepare a hydrogen storage alloy slurry.

  And after apply | coating the obtained hydrogen storage alloy slurry to both surfaces of the negative electrode core body which consists of punched metal (made by nickel plating steel plate), it dried at 100 degreeC and rolled so that it might become a predetermined | prescribed filling density. Then, the hydrogen storage alloy negative electrode 12 filled with the hydrogen storage alloy active material was produced by cutting into a predetermined dimension.

3. Separator The separator 13 is a non-woven fabric made of polyolefin synthetic resin and subjected to a hydrophilic treatment. As the polyolefin-based synthetic resin, for example, synthetic resins such as polyethylene and polypropylene can be used. And the separator 13 contains an ultrafine fiber and a composite fiber as a main component. The ultrafine fiber has a substantially circular cross-sectional shape, and has a single structure made of, for example, one type of polyolefin resin. The ultrafine fiber can be used as the ultrafine fiber by extruding the sea-island type fiber while regulating the die into the sea component at the spinneret, and removing the sea component from the obtained fiber.

  The composite fiber has a substantially circular cross-sectional shape, and has, for example, a core-sheath structure, and at least a part or all of the surface of the core material is covered with the sheath material. The core material and the sheath material are made of different polyolefin resins, and the melting point of the polyolefin resin of the sheath material is lower than the melting point of the polyolefin resin of the core material. In the nonwoven fabric, the ultrafine fibers and the composite fibers and the composite fibers are bonded to each other by fusion via a sheath material. The composite fiber can be produced by, for example, drawing a melt-spun composite undrawn yarn. The composite fiber may have an eccentric structure or a sea-island structure, and has a melting point higher than that of other parts as a fusion part for bonding the ultrafine fiber and the composite fiber to at least a part of the outer peripheral surface. As long as it contains a low part.

The basis weight of the separator 13 is, for example, 30 g / m ² or more and 60 g / m ² or less, and the thickness is, for example, 0.04 mm or more and 0.12 mm or less. The separator 13 obtained as described above was designated as a separator a. A separator b was prepared by applying a solution containing niobium oxide (Nb ₂ O ₅ ) powder and a binder to the surface of the separator a and drying it.

4). Nickel-hydrogen storage battery Next, a nickel positive electrode 11 (a, b, x) and a hydrogen storage alloy negative electrode 12 produced as described above are used, and a separator 13 (a) made of a polyolefin non-woven fabric is interposed therebetween. Thus, a spiral electrode group was produced by winding in a spiral shape. The core exposed portion 11a of the nickel positive electrode 11 is exposed at the upper part of the spiral electrode group thus manufactured, and the core exposed portion 12a of the hydrogen storage alloy negative electrode 12 is exposed at the lower part. ing. Next, the positive electrode current collector 14 is welded onto the core exposed portion 11a of the nickel positive electrode 11 exposed at the upper end surface of the obtained spiral electrode group, and the core body exposed at the lower end surface of the spiral electrode group. The negative electrode current collector 15 was welded to the part 12a to obtain an electrode body.

  Next, after the obtained electrode body is accommodated in a bottomed cylindrical outer can 16 in which nickel is plated on iron (the outer surface of the bottom surface becomes a negative electrode external terminal) 16, the negative electrode current collector 15 is attached to the outer can 16. Welded to the inner bottom. On the other hand, the current collecting lead portion 14a extending from the positive electrode current collector 14 was welded to the bottom portion of the sealing body 17 which also served as the positive electrode terminal and was fitted with the insulating gasket 18 on the outer peripheral portion. The sealing body 17 is provided with a positive electrode cap 17a, and a pressure valve (not shown) including a valve body 17b and a spring 17c which are deformed when a predetermined pressure is reached is disposed in the positive electrode cap 17a.

  Next, after forming the annular groove portion 16 a on the upper outer peripheral portion of the outer can 16, an alkaline electrolyte is injected, and the outer peripheral portion of the sealing body 17 is mounted on the annular groove portion 16 a formed on the upper portion of the outer can 16. An insulating gasket 18 was placed. After that, the nickel-hydrogen storage battery 10 (A, B, X) having a nominal capacity of 6 Ah was produced by caulking the opening edge 16 b of the outer can 16. In this case, the alkaline electrolyte is prepared as a mixed aqueous solution of sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH) so that the concentration is 7.0 mol / liter. Was used.

  Here, a battery using the nickel positive electrode a was designated as a battery A, and a battery using the nickel positive electrode b was designated as a battery B. A battery X using a nickel positive electrode x was used. Next, using each of these batteries A, B, and X, the battery capacity (nominal capacity) is charged to 160% of the battery capacity with a charge current of 1 It (SOC 160% charge) in a temperature atmosphere of 25 ° C. Then, after resting for 1 hour, it was left in a temperature atmosphere at 70 ° C. for 24 hours. Thereafter, the battery was discharged in a temperature atmosphere of 25 ° C. with a discharge current of 1 It until the battery voltage became 0.3V. Such charging, resting, leaving, and discharging were repeated for two cycles to perform activation processing (aging treatment) for each of the batteries A, B, and X.

  On the other hand, using the battery B, in a temperature atmosphere of 25 ° C., the battery capacity (nominal capacity) is charged to 160% of the battery capacity (SOC 160% charge) with a charging current of 1 It, and after resting for 1 hour, It was allowed to stand for 24 hours in a temperature atmosphere of 70 ° C. Thereafter, the battery was discharged in a temperature atmosphere of 25 ° C. with a discharge current of 1 It until the battery voltage became 0.3V. A battery C was obtained by repeating such charging, resting, leaving at high temperature, and discharging two cycles and then performing an additional aging treatment (leaving at 60 ° C. for 1 day). Further, in this battery C, a battery D in which a separator b on which niobium (Nb) was previously supported was used as the separator 13 was designated as a battery D. Furthermore, in the battery C, a battery E using an alkaline electrolyte containing tungsten (W) in advance as the alkaline electrolyte was used.

5. Battery test (1) Initial output characteristics After the activation process (aging process) or the additional aging process as described above, each of these batteries A, B, C, D, E, and X is subjected to a temperature atmosphere of 25 ° C. Then, the battery was charged to 50% of SOC (State Of Charge: charging depth) at a charging current of 1 It (SOC 50% charge). Thereafter, the charging / discharging current was increased in the order of 20A charging → 40A discharging → 40A charging → 80A discharging → 60A charging → 120A discharging → 80A charging → 160A discharging → 100A charging → 200A discharging.

At this time, a pause period of 10 minutes was provided between each step, and charging / discharging was performed in the order of charging for 20 seconds → pause for 10 minutes → discharge for 10 seconds → pause for 10 minutes. Then, the battery voltage at the time point of 10 seconds is plotted against the discharge current, and the product of the current value and 0.9V when the straight line obtained by the least square method reaches 0.9V is output (W) As sought.
In this case, when the calculated output (W) of the battery X is the reference (100) and the relative ratio (vs. the battery X) is calculated as the initial output characteristics of the batteries A, B, C, D, and E, The results shown in Table 1 were obtained.

(2) Output characteristics after partial charge / discharge cycle (after endurance) In addition, after the activation process (aging process) or additional aging process as described above, each of these batteries A, B, C, D, E, After charging to a voltage (upper limit voltage) at which the SOC (State Of Charge) with respect to the initial capacity is 80% at a charging current of 10 It in a temperature atmosphere of 25 ° C. using X, discharge of 10 It A partial charge / discharge cycle test (endurance test) was repeated in which the charge / discharge cycle of discharging to a voltage (lower limit voltage) at which the SOC was 20% was repeated for 2 months.
Thereafter, the outputs of the batteries A, B, C, D, E, and X were evaluated in the same manner as described above. Then, the obtained output (W) of the battery X after endurance is used as the reference (100), and the relative ratio (with respect to the battery X) is calculated as the output characteristics after endurance of the batteries A, B, C, D, and E. Then, the results shown in Table 1 below were obtained.

(3) Charging efficiency Further, after the activation process (aging process) or additional aging process as described above, these batteries A, B, C, D, E, and X are used in a temperature atmosphere of 25 ° C. At a current of 0.5 It, the battery is charged up to a voltage (upper limit voltage) at which the SOC (State Of Charge) is 80% with respect to the initial capacity, and immediately after that, a final voltage of 0. The battery was discharged until 9V was reached. And while calculating | requiring the discharge capacity in 1.0V time point, the ratio of the discharge capacity with respect to the charge capacity at this time was computed as charge efficiency (%). Then, the charging efficiency (%) of the obtained battery X is set as a reference (100), and the relative ratio (vs. battery X) is calculated as the charging efficiency (%) of the batteries A, B, C, D, E. The results shown in Table 1 below were obtained.

As is clear from the results in Table 1 above, in the battery X including the sintered nickel positive electrode x prepared without being immersed in an aqueous alkaline solution to which niobium oxide (Nb ₂ O ₅ ) powder was added, the initial output It can be seen that the characteristics and the output characteristics after durability are low, and the charging efficiency is also low. This is because magnesium (Mg) in the hydrogen storage alloy negative electrode 12 moves to the sintered nickel positive electrode 11, so that the charging voltage is increased and oxygen is likely to be generated. This is probably because In addition, it is considered that the generation of oxygen is likely to occur, so that the hydrogen storage alloy deteriorates after the endurance of repeated partial charge and discharge at a high rate and the output performance decreases.

On the other hand, 0.1 mass% niobium (Nb) is included with respect to metallic nickel (Ni) in the positive electrode active material produced by immersing in an alkaline aqueous solution to which niobium oxide (Nb ₂ O ₅ ) powder is added. In the battery A provided with the sintered nickel positive electrode a, the effect of improving the charging efficiency could be confirmed after the endurance. This is because the sintered nickel positive electrode contains a slight amount of niobium (Nb) by immersing the sintered nickel positive electrode in an alkaline aqueous solution. It is considered that the effect of improving the high temperature charging efficiency is exhibited.

Moreover, 0.2 mass% niobium (Nb) is included with respect to metallic nickel (Ni) in the positive electrode active material produced by immersing in an alkaline aqueous solution to which niobium oxide (Nb ₂ O ₅ ) powder is added. In the battery B provided with the sintered nickel positive electrode b, it can be seen that the initial output characteristics, the output characteristics after the endurance, and the charging efficiency are improved. This is because magnesium (Mg) eluted from the hydrogen storage alloy negative electrode 12 reaches the sintered nickel positive electrode 11, and niobium (Nb) present on the surface of the sintered nickel positive electrode 11 is converted into the positive electrode active material layer. It is thought that it became easy to move to the inside of the. As a result, the position where niobium (Nb) on the surface of the sintered nickel positive electrode 11 was present becomes a porous body that improves the reaction area, and the reaction resistance is reduced. As a result, the initial output characteristics are reduced. It is thought that it improved. From this, it can be said that it is preferable to contain niobium (Nb) so that it may become 0.2 mass% or more with respect to the metal nickel (Ni) in a positive electrode active material.

  In addition, the magnesium (Mg) in the hydrogen storage alloy reaches niobium (Nb) from the surface of the sintered nickel positive electrode 11 to the inside of the positive electrode active material layer, rather than the deterioration of the high temperature charging characteristics due to the arrival of the sintered nickel positive electrode 11. This is considered to be because the effect of improving the high-temperature charging characteristics due to the movement of) increased. As a result, it is considered that the generation of oxygen gas during the partial charge / discharge cycle was suppressed, and the deterioration of output characteristics after durability could be suppressed. The content of niobium (Nb) in the sintered nickel positive electrode 11 is desirably 0.2% by mass or more with respect to metallic nickel (Ni) in the positive electrode active material. On the other hand, if the content of niobium (Nb) in the sintered nickel positive electrode 11 is too large, the battery capacity is reduced, so that the C rate in large current charge / discharge is increased and the resistance is increased. The maximum value of the content of niobium (Nb) in the formula nickel positive electrode 11 is desirably 5% by mass or less with respect to metallic nickel (Ni) in the positive electrode active material.

Further, the sintered nickel positive electrode b containing niobium (Nb) was immersed in an alkaline aqueous solution containing niobium oxide (Nb ₂ O ₅ ) powder, and the sintered nickel positive electrode b was further provided. In the battery C produced by subjecting the battery to additional aging treatment (left at 60 ° C. for 1 day), the initial output characteristics, the output characteristics after durability, and the charging efficiency are further improved as compared with the battery B. I understand.

  This is presumably because the formation of the active material form of the sintered nickel positive electrode b containing niobium (Nb) was promoted by performing an additional aging treatment. That is, niobium (Nb) present on the surface of the sintered nickel positive electrode 11 is more easily moved into the positive electrode active material layer, and niobium (Nb) on the surface of the sintered nickel positive electrode is present. The position is a porous body that further improves the reaction area. As a result, the resistance is further reduced, so that the initial output characteristics and the output characteristics after endurance are improved, and it can be said that a more preferable result is obtained.

In this case, in the battery D using the separator b previously supporting niobium oxide (Nb ₂ O ₅ ) powder as the separator 13 used for separating the hydrogen storage alloy negative electrode 12 and the sintered nickel positive electrode 11, the battery C includes In contrast, it can be seen that the charging efficiency after the durability test is further improved. This is because niobium (Nb) moves from the surface of the positive electrode to the inside of the active material layer as the charge and discharge progress, so that the amount of niobium (Nb) near the surface of the positive electrode decreases. Nb) dissolves in the electrolyte solution from the separator 13 with the progress of the durability test, and the dissolved niobium (Nb) moves to the surface of the sintered nickel positive electrode 11 to generate oxygen near the surface of the sintered nickel positive electrode 11. This is considered to suppress the above.

This technique is an effective means even with a separator alone. Such an application method of niobium (Nb) has the advantage that no significant change in the production process is required, but on the other hand, the effect is less than direct application to the sintered nickel positive electrode 11. For this reason, it is preferable that the amount of Mg in the hydrogen storage alloy is small. When the hydrogen storage alloy is represented by the general formula Ln _lx Mg _x Ni _yab Al _a M _b , it is within the range of 0.05 ≦ x ≦ 0.30. The content is preferably in the range of 0.09 ≦ x ≦ 0.13. In addition, when the amount of niobium (Nb) supported on the separator 13 is too large, the performance variation increases. Therefore, the maximum amount of niobium (Nb) supported on the separator 13 is larger than the metal nickel (Ni) in the positive electrode active material. It is preferable that it is 3 mass% or less.

  Furthermore, in the battery E in which tungsten (W) is added to an alkaline electrolyte that is a mixed aqueous solution of sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH), It can be seen that the charging efficiency after the durability test is further improved. This is because the amount of niobium (Nb) near the surface of the sintered nickel positive electrode 11 decreases as niobium (Nb) moves from the surface of the sintered nickel positive electrode 11 to the inside of the active material layer as charge and discharge progress. However, on the other hand, tungsten (W) contained in the alkaline electrolyte moves to the surface of the sintered nickel positive electrode 11 with the progress of the durability test, and suppresses oxygen generation in the vicinity of the surface of the sintered nickel positive electrode 11. This is probably because of this. The effect of improving the charging efficiency due to the addition of tungsten (W) can be manifested alone.

In the above-described embodiment, an example in which a hydrogen storage alloy represented by Nd _0.9 Mg _0.1 Ni _3.3 Al _0.2 is used has been described. However, as a hydrogen storage alloy, the general formula is Ln _lx Mg _x Ni _yab Al _a M _b (wherein Ln is at least one element selected from rare earth elements including Y and Zr and Ti, and M is V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn) , In, Cu, Si, P, B) and 0.05 ≦ x ≦ 0.30, 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ Any hydrogen storage alloy that satisfies the conditions of 0.50, 2.8 ≦ y ≦ 3.9 may be used.

DESCRIPTION OF SYMBOLS 10 ... Nickel-hydrogen storage battery, 11 ... Nickel electrode, 11a ... Core body exposed part, 12 ... Hydrogen storage alloy electrode, 12a ... Core body exposed part, 13 ... Separator, 14 ... Positive electrode collector, 14a ... Current collection lead part 15 ... negative electrode current collector, 16 ... exterior can, 16a ... annular groove, 16b ... opening edge, 17 ... sealing body, 17a ... positive electrode cap, 17b ... valve plate, 17c ... spring, 18 ... insulating gasket

Claims (5)

A sintered nickel positive electrode using nickel hydroxide as a main positive electrode active material, a hydrogen storage alloy negative electrode using a hydrogen storage alloy as a negative electrode active material, and a separator separating the hydrogen storage alloy negative electrode and the sintered nickel positive electrode; An alkaline storage battery comprising an electrode group consisting of an alkaline electrolyte and an outer can,
The hydrogen storage alloy used for the hydrogen storage alloy negative electrode has a general formula of Ln _lx Mg _x Ni _yab Al _a M _b (where Ln is at least selected from a rare earth element including Y, Zr and Ti). M is at least one element selected from V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P, and B; 05 ≦ x ≦ 0.30, 0.05 ≦ a ≦ 0.30, 0 ≦ b ≦ 0.50, 2.8 ≦ y ≦ 3.9),
2. The alkaline storage battery, wherein the sintered nickel positive electrode contains niobium (Nb).   The content of niobium (Nb) contained in the sintered nickel positive electrode is 0.2% by mass or more based on the mass of metallic nickel (Ni) in the positive electrode active material in the positive electrode active material. The alkaline storage battery according to claim 1.   After the niobium (Nb) contained in the sintered nickel positive electrode is impregnated with a main positive electrode active material made of nickel hydroxide, the sintered nickel positive electrode is immersed in an alkaline aqueous solution containing niobium (Nb). The alkaline storage battery according to claim 1, wherein the alkaline storage battery is obtained.   The alkaline storage battery according to claim 1, wherein the niobium (Nb) contained in the sintered nickel positive electrode is obtained by using a separator containing a niobium (Nb) compound.   The alkaline storage battery according to claim 1, wherein the alkaline electrolyte in the outer can contains tungsten (W).

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