JP5334498B2 - Alkaline storage battery - Google Patents

Description

  The present invention includes an electrode group including a 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 in an outer can together with an alkaline electrolyte. The present invention relates to an alkaline storage battery, and more particularly to an alkaline storage battery suitable for use in a vehicle such as a hybrid vehicle (HEV) and an electric vehicle (PEV).

  In recent years, secondary batteries have been used in a wide variety of applications such as mobile phones, personal computers, electric tools, hybrid vehicles (HEV), electric vehicles (PEV), etc., and alkaline storage batteries are used for these applications. became. Among these, particularly in alkaline storage batteries used for vehicle-related applications such as hybrid vehicles (HEV) and electric vehicles (PEV), high output performance and high durability performance are particularly required. As the market matures, there is an increasing demand for smaller and lighter weight.

Here, as a technique for reducing the size and weight, for example, it is possible to reduce the weight by reducing the amount of hydrogen storage alloy used for the negative electrode, but if the amount of hydrogen storage alloy is reduced, the output decreases due to a decrease in the nickel active point. A new problem will arise. In order to improve this, Patent Document 1 (Japanese Patent Laid-Open No. 2005-32573) has proposed a method of increasing the operating voltage using a hydrogen storage alloy having a high hydrogen equilibrium pressure. However, when a hydrogen storage alloy having a high hydrogen equilibrium pressure is used, a new problem arises that the charge / discharge cycle life is reduced.
JP 2005-32573 A

The present inventors have, A ₅ B ₁₉ type structure has a crystal structure, and the stoichiometric ratio of the molar ratio of B component to A component in the A ₅ B ₁₉ type structure (B / A) is A capacity ratio Z (= Y / X) that is a ratio of the capacity Y of the hydrogen storage alloy negative electrode to the capacity X of the nickel positive electrode is 1.2 or less (1.0 <Z It was previously proposed as Japanese Patent Application No. 2007-253990 that a low-temperature output and durability can be achieved by partially charging and discharging a battery satisfying ≦ 1.2).

  Here, when further miniaturization and weight reduction are to be performed, it is necessary to make the battery small and light and have a high output, that is, a battery having a high energy density. Therefore, a battery size that takes into consideration the maximum dischargeable current value (limit current value) per battery capacity is required. This is because a simple reduction in size, that is, a reduction in the size of a simple battery only reduces the battery capacity. For this reason, it has been found that it is necessary to take measures to obtain a battery size that takes into account the maximum dischargeable current value (limit current value) per battery capacity.

  The present invention has been made on the basis of these findings. The battery size is selected in consideration of the maximum dischargeable current value (limit current value) per battery capacity, and is small, lightweight, and has high output. It was made for the purpose of obtaining a battery.

  The alkaline storage battery of the present invention comprises an electrode group consisting of a hydrogen storage alloy negative electrode using a hydrogen storage alloy as a negative electrode active material, a nickel positive electrode using nickel hydroxide as a main positive electrode active material, and a separator in an outer can together with an alkaline electrolyte. In preparation. In order to achieve the above object, in the nickel positive electrode, zinc is added to nickel hydroxide as a main positive electrode active material, and the amount of zinc added is 5 mass relative to the mass of nickel in the positive electrode active material layer. %, The battery capacity is 4.5 Ah or less, and the discharge is allowed to exceed the discharge rate of 60 It.

  Here, in a battery equipped with a normal nickel positive electrode in which the amount of zinc added is about 15% by mass with respect to the nickel mass, the battery capacity is simply 4.5 Ah or less in order to reduce the size and weight of the alkaline storage battery. It was found that discharge was impossible at a discharge rate (discharge rate) exceeding 60 It. However, in a battery having a nickel positive electrode in which the amount of zinc added is 5% by mass or less based on the mass of nickel in the positive electrode active material layer, a discharge rate (discharge) exceeding 60 It even when the battery capacity is reduced to 4.5 Ah or less. It has been found that discharge is possible.

  Therefore, in the alkaline storage battery of the present invention, zinc is added to nickel hydroxide as the main positive electrode active material, and the battery capacity is 4.5 Ah or less, and discharge is possible at a discharge rate (discharge rate) exceeding 60 It. Thus, the nickel positive electrode added so that the added amount of zinc is 5% by mass or less with respect to the mass of nickel in the positive electrode active material layer is provided.

  As a result, the battery volume can be reduced as much as the battery capacity is reduced, and the output density (W / L) can be increased. And since the nickel positive electrode whose mass of Zn with respect to Ni mass is 5 mass% or less is used, it becomes a battery which can be discharged with the discharge rate (discharge rate) exceeding 60 It. As a result, an alkaline storage battery having a large output density (W / L) and an improved capacity retention rate after a partial charge / discharge cycle is obtained. In this case, if the nickel positive electrode added so that the added amount of zinc is 5 mass% or less with respect to the nickel mass in the positive electrode active material layer is provided, the memory effect is improved and the life is extended. It became clear that there was an effect.

  The nickel positive electrode is preferably one in which at least nickel hydroxide and zinc, which are the main positive electrode active materials, are filled in the pores of the sintered nickel substrate by the impregnation treatment and the alkali treatment. This is because, according to the solution impregnation, it is easy to add zinc so that the amount of zinc is 5% by mass or less with respect to the amount of nickel in the positive electrode active material layer. The concentration of the alkaline electrolyte is 6.5 mol / L or less, the amount of lithium (Li) contained in the alkaline electrolyte is 0.3 mol / L or more, and sodium hydroxide, potassium hydroxide, It is preferable to use a mixed alkaline aqueous solution composed of lithium hydroxide.

  Here, when the alkaline electrolyte containing the lithium (Li) amount as described above is used at the concentration as described above, if the battery capacity is too low, the low charge depth region (low SOC region, SOC is 20%). It was revealed that the output decreased at the same level. For this reason, in the present invention, the lower limit value of the battery capacity is set to 4.0 Ah to suppress the output decrease in the low depth of charge (SOC) region.

  When charge / discharge control is performed on this type of battery, when the depth of charge (SOC) reaches a voltage corresponding to 20%, the discharge is stopped and charging is started, and the depth of charge (SOC) reaches a voltage equivalent to 80%. Then, it is preferable to perform partial charge / discharge control so as to stop charging and start discharging. This is because if the amount of zinc contained in the positive electrode mixture is reduced to 5% by mass or less with respect to the mass of nickel in the positive electrode active material layer, the memory effect is suppressed even if partial charge / discharge is performed. This is because the service life is long.

  The alkaline storage battery of the present invention has a high output density regardless of its small size and light weight. Therefore, if the alkaline storage battery of the present invention is used, it has a high motor performance and a low fuel consumption hybrid vehicle (HEV) or electric vehicle ( PEV) can be provided.

  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. In addition, FIG. 1 is sectional drawing which shows typically the alkaline storage battery of this invention. FIG. 2 is a graph showing the relationship between the discharge current (A) and the power density (W / L). In this graph, the value at the lowest current of the battery A shown in Table 2 described later is shown as 100. ing. FIG. 3 is a graph showing the relationship between the battery capacity value (Ah) and the SOC dependency (the output ratio of SOC 20 (%) to SOC 50 (%)).

1. Nickel positive electrode The nickel positive electrode 11 of the present invention is formed by filling a predetermined amount of nickel hydroxide and zinc hydroxide into the pores of a nickel sintered substrate serving as a substrate. In this case, the nickel sintered substrate is produced as follows. That is, for example, a nickel slurry is prepared by mixing and kneading methyl cellulose (MC), which is a thickener, polymer hollow microspheres (for example, those having a pore size of 60 μm), and water with nickel powder. Next, after applying nickel slurry on both sides of the punching metal made of nickel-plated steel plate, it is heated at 1000 ° C. in a reducing atmosphere, and the applied thickener and polymer hollow microspheres disappear. It is produced by sintering nickel powders. In addition, when the obtained nickel sintered board | substrate was measured with the mercury intrusion type porosimeter (Pascal 140 by Faisons Instruments), it turned out that porosity is 85%.

The obtained nickel sintered substrate is impregnated with an impregnating solution as described below, and after impregnating, the active material filling operation including an alkali treatment with an alkali treatment solution is repeated a predetermined number of times. A predetermined amount of nickel hydroxide and zinc hydroxide are filled in the pores of the bonded substrate. Thereafter, the nickel positive electrode 11 filled with the positive electrode active material is produced by cutting into a predetermined size. As the impregnating liquid, a molar ratio of nickel nitrate (Ni (NO ₃ ) ₂ ), cobalt nitrate (Co (NO ₃ ) ₂ ), and zinc nitrate (Zn (NO ₃ ) ₂ ) is 100: 15: 5 (specific gravity). 1.8) or 100: 5: 5 (specific gravity 1.8). Further, as the alkali treatment liquid, a sodium hydroxide (NaOH) aqueous solution having a specific gravity of 1.3 was used.

In this case, in a mixed aqueous solution (impregnating liquid) having a specific gravity of 1.8 consisting of nickel nitrate (Ni (NO ₃ ) ₂ ), cobalt nitrate (Co (NO ₃ ) ₂ ), and zinc nitrate (Zn (NO ₃ ) ₂ ). After soaking (impregnation treatment), nickel hydroxide (Ni (OH) ₂ ), hydroxylation by immersion and reaction (alkali treatment) in an alkali solution (for example, sodium hydroxide having a specific gravity of 1.3) It is converted into cobalt (Co (OH) ₂ ) and zinc hydroxide (Zn (OH) ₂ ), crystallized in the pores, washed with water and dried. Such impregnation treatment, alkali treatment, washing with water and drying are repeated six times to produce the nickel positive electrode 11 filled with a predetermined amount of the positive electrode active material.

Here, the molar ratio of nickel nitrate (Ni (NO ₃ ) ₂ ), cobalt nitrate (Co (NO ₃ ) ₂ ) and zinc nitrate (Zn (NO ₃ ) ₂ ) is 100: 5 : 15 , and the specific gravity is 1. 8 is used to adjust the impregnation amount of the impregnation liquid so that the ratio of the zinc mass to the nickel mass in the active material layer of the nickel positive electrode 11 is 15 mass% and the battery capacity is 6 Ah. The produced product was designated as a nickel positive electrode a. A nickel positive electrode b was prepared by using the obtained nickel positive electrode a and cutting it to a size such that the battery capacity was 4 Ah.

The molar ratio of nickel nitrate (Ni (NO ₃ ) ₂ ), cobalt nitrate (Co (NO ₃ ) ₂ ) and zinc nitrate (Zn (NO ₃ ) ₂ ) is 100: 5: 5, and the specific gravity is 1.8. The impregnating solution is used to adjust the impregnating amount of the impregnating solution so that the ratio of the zinc mass to the nickel mass in the active material layer of the nickel positive electrode 11 is 5 mass% and the battery capacity is 6 Ah. This was used as a nickel positive electrode c. Further, using the obtained nickel positive electrode c, a product prepared by cutting to a battery capacity of 4 Ah was used as a nickel positive electrode d, and a product prepared by cutting into a size such that the battery capacity was 3 Ah. e. The contents of the nickel positive electrodes a to e are summarized in a table as shown in Table 1 below.

2. Hydrogen Storage Alloy Negative Electrode The hydrogen storage alloy negative electrode 12 is formed by filling a hydrogen storage alloy slurry in a negative electrode core made of punching metal. In this case, after mixing rare earth elements (Ln; La, Pr, Nd, etc.), magnesium (Mg), nickel (Ni), aluminum (Al) and the like in a predetermined molar ratio, these mixtures Is put into a high-frequency induction furnace in an argon gas atmosphere and melted, and then the molten metal is rapidly cooled to produce an ingot of a hydrogen storage alloy. Next, the melting point (Tm) of each ingot of each obtained hydrogen storage alloy is measured using DSC (differential scanning calorimeter). Then, the crystal structure of the hydrogen storage alloy is obtained by performing a heat treatment for a predetermined time (in this case, 10 hours) at a temperature (Ta = Tm-30 ° C.) lower by 30 ° C. than the melting point (Tm) of these hydrogen storage alloys. Is adjusted to have an A ₅ B ₁₉ type structure.

Note that the crystal structure of the obtained hydrogen storage alloy is A ₅ B ₁₉ type structure can be confirmed by an X-ray diffraction method using an X-ray diffraction measuring apparatus using a Cu—Kα tube as an X-ray source. . After this, after coarsely crushed, and the hydrogen storage alloy powder was mechanically pulverized in an inert gas atmosphere, further selecting a hydrogen-absorbing alloy powder between 400 and mesh 200 mesh by sieving. 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.

  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 parts by mass, 0.5 parts by mass of carbon black as a conductive agent, and an appropriate amount of pure water are 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 punching metal (made by nickel plating steel plate), after drying at 100 degreeC and rolling so that it may become predetermined | prescribed packing density, predetermined The hydrogen storage alloy negative electrode 12 is produced by cutting into the following dimensions.

3. Nickel-hydrogen storage battery Next, the nickel positive electrode 11 (a, b, c, d) produced as described above and the hydrogen storage alloy negative electrode 12 are used, and a separator 13 made of a polyolefin nonwoven fabric is interposed therebetween. Thus, a spiral electrode group is produced by winding in a spiral shape. As shown in FIG. 1, the core exposed portion 11c of the nickel positive electrode 11 is exposed at the upper part of the spiral electrode group produced in this manner, and the core of the hydrogen storage alloy electrode 12 is exposed at the lower part thereof. The body exposed part 12c is exposed. Next, the negative electrode current collector 14 is welded to the core exposed portion 12c exposed at the lower end surface of the obtained spiral electrode group, and the core exposed portion 11c of the nickel electrode 11 exposed at the upper end surface of the spiral electrode group. A positive electrode current collector 15 is welded to the electrode body to form an electrode body.

  Next, after the obtained electrode body was accommodated in a bottomed cylindrical outer can in which nickel was plated on iron (the outer surface of the bottom surface becomes a negative external terminal) 17, the negative electrode current collector 14 was attached to the outer can 17. Weld to the inner bottom. On the other hand, the current collecting lead portion 15a extending from the positive electrode current collector 15 serves as a positive electrode terminal and is welded to the bottom portion of the sealing body 18 having the insulating gasket 19 attached to the outer peripheral portion. The sealing body 18 is provided with a positive electrode cap 18a, and a pressure valve (not shown) composed of a valve body 18b and a spring 18c, which are deformed when a predetermined pressure is reached, is disposed in the positive electrode cap 18a.

  Next, after forming the annular groove portion 17 a on the outer periphery of the upper portion of the outer can 17, an alkaline electrolyte is injected, and the outer periphery portion of the sealing body 18 is mounted on the annular groove portion 17 a formed on the upper portion of the outer can 17. Insulating gasket 19 is placed. Thereafter, the opening edge 17b of the outer can 17 is caulked, thereby the nickel-hydrogen storage battery 10 (A, C) having a battery capacity (nominal capacity) of 6 Ah and the nickel-hydrogen battery having a battery capacity (nominal capacity) of 4 Ah. The storage battery 10 (B, D) is produced. In this case, the alkaline electrolyte is a mixed aqueous solution of sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH), and the concentration of the electrolyte is 7.0 mol / L (7.0 N). The Li concentration was adjusted to 0.21 mol / L (0.21N).

  Here, the nickel-hydrogen storage battery 10 having a battery capacity of 6 Ah using the nickel positive electrode a was designated as battery A, and the nickel-hydrogen storage battery 10 having a battery capacity of 4 Ah using the nickel positive electrode b was designated as battery B. A nickel-hydrogen storage battery 10 having a battery capacity of 6 Ah using the nickel positive electrode c was designated as battery C, and a nickel-hydrogen storage battery 10 having a battery capacity of 4 Ah using the nickel positive electrode d was designated as battery D. In this case, assuming that the volume of the batteries A and C with the battery capacity of 6 Ah is 100, the volume (volume ratio) of the batteries B and D with the battery capacity of 4 Ah was 70.

4). Test (1) Output Density Next, after activating each of the batteries A, B, C, and D produced as described above, the battery capacity (nominal capacity) was used in a temperature atmosphere of 25 ° C. using these batteries. ) Was charged to 50% of the battery capacity at a charge rate of 1 It (SOC (State Of Charge): 50%). After this, 20A charge → 40A discharge → pause → 40A charge → 80A discharge → pause → 60A charge → 120A discharge → pause → 80A charge → 160A discharge → pause → 100A charge → 200A discharge → pause → 120A charge → 240A discharge → pause → 140A charge → 280A discharge → pause → 160A charge → 320A discharge → pause → 180A charge → 360A discharge → pause → 200A charge → 400A discharge → pause → 220A charge → 440A discharge The pause for 10 minutes was repeated.

  Then, the battery voltage (V) at the time of discharging each 10 seconds is plotted against the discharge current (A), and the current value (A) when the straight line obtained by the least square method reaches 0.9V. And the product of 0.9V was obtained as output (W). Further, when the maximum output (W) obtained for the battery A is set to 100 and the obtained maximum outputs (W) of the other batteries B, C, and D are expressed as relative values (output ratios) (%) with respect to this, The results shown in Table 2 were obtained. Further, the ratio of the output (W) to the battery volume (L) at each discharge current value (A) is obtained as the output density (W / L), and each discharge current value (A) is plotted on the horizontal axis (X axis). Plotting and plotting the obtained power density (W / L) on the vertical axis (Y-axis) gave the results shown in FIG.

Also, the output (W) for the battery volume (L) during discharge for 10 seconds at 60 It (360 A for batteries A and C with a battery capacity of 6 Ah and 240 A for batteries B and D with a battery capacity of 4 Ah). ) Was determined as the power density (W / L) during 60 It discharge. Then, the obtained 60 It discharge power density (W / L) for battery A is set to 100, and the obtained 60 It discharge power density (W / L) of other batteries B, C, and D is a relative value (60 It). When expressed in terms of power density ratio during discharge, the results shown in Table 2 below were obtained. Next, discharge exceeding 60 It was performed (400 A for batteries A and C with a battery capacity of 6 Ah, and 280 A for batteries B and D with a battery capacity of 4 Ah). As shown in Table 2, the batteries C and D were found to be capable of discharging over 60 It.

From the results shown in Table 2 and FIG.
That is, when comparing the battery A and the battery C having a battery capacity of 6 Ah, the battery C using the nickel positive electrode having a Zn mass of 5 mass% with respect to the Ni mass can be discharged even if the discharge for 10 seconds exceeds 60 It. On the other hand, in the battery A using the nickel positive electrode in which the mass of Zn is 15% by mass with respect to the mass of Ni, it can be seen that the discharge for 10 seconds is up to 60 It. In this case, in the battery C using the nickel positive electrode having a mass of Zn of 5% by mass with respect to the mass of Ni, the maximum output ratio and the 60 It discharge are higher than those of the battery A using the nickel positive electrode having a mass of Zn of 15% by mass with respect to the Ni mass. It can be seen that the hourly power density ratio is slightly improved.

  On the other hand, when comparing the battery B and the battery D having a battery capacity of 4 Ah, the battery D using a nickel positive electrode having a mass of Zn of 5 mass% with respect to the mass of Ni is possible even if discharge for 10 seconds exceeds 60 It. On the other hand, in the battery B using the nickel positive electrode in which the mass of Zn is 15% by mass with respect to the mass of Ni, it can be seen that the discharge for 10 seconds is up to 60 It. In this case, in the battery D using the nickel positive electrode having a mass of Zn of 5% by mass with respect to the mass of Ni, although the battery capacity was reduced to 4 Ah, the reduction in the maximum output was significantly reduced (compared to the battery C). In the battery B using a nickel positive electrode having a Zn mass of 15 mass% with respect to the Ni mass, the maximum output ratio is -20% (relative to the battery C). -25%). This is because when the maximum output is exceeded, the added zinc becomes a resistance component and the positive electrode resistance increases rapidly.

Furthermore, when comparing battery C and battery D, which can discharge for 10 seconds with a discharge current exceeding 60 It, battery D with a battery capacity of 4 Ah and a volume ratio of 70 has a higher output density (W / L). I understand. In other words, when a nickel positive electrode with a Zn mass of 5 mass% or less with respect to the Ni mass is used, the output is reduced by reducing the capacity of the nickel positive electrode and the battery volume (L), thereby reducing the size and weight. It was revealed that the density (W / L) was improved.
In other words, the battery capacity is reduced (4.5Ah or less is desirable), the battery volume (L) is decreased to increase the output density (W / L), and discharge for 10 seconds is possible with a discharge current exceeding 60 It. In order to obtain a simple battery, it can be said that it is necessary to use a nickel positive electrode in which the mass of Zn with respect to the mass of Ni is 5 mass% or less.

(2) Capacity after partial charge / discharge cycle Next, in each of these batteries A, B, C, D, after charging to a voltage at which SOC (State Of Charge) is 80% at a charge rate of 10 It, A partial charge / discharge cycle test was performed in which a cycle of discharging to a voltage at which the SOC became 20% at a discharge rate of 10 It was repeated. Then, such a partial charge / discharge cycle was repeated until the amount of discharged electricity reached 50 kAh.

Thereafter, the battery capacity after partial charge / discharge cycle (capacity after partial charge / discharge cycle) X2 of each battery A, B, C, D was determined. Then, after calculating the capacity X2 after the partial charge / discharge cycle with respect to the initial capacity X1 as the capacity ratio after the partial charge / discharge cycle (X2 / X1), the capacity ratio after the partial charge / discharge cycle of the battery A is set to 100. The results shown in Table 3 below were obtained, in which the capacity ratio after partial charge / discharge cycles of batteries B, C, and D was obtained as a relative value to battery A (capacity ratio after charge / discharge cycles).

From the results in Table 3 above, the following became clear.
That is, when comparing the battery A with the battery capacity 6Ah and the battery C, in the battery C using the nickel positive electrode having a Zn mass of 5 mass% with respect to the Ni mass, the capacity ratio after the charge / discharge cycle is relative to the battery A. It can be seen that there is an improvement of 10%. This is presumably because a smaller amount of zinc in the nickel positive electrode can suppress the memory effect associated with the partial charge / discharge cycle, and the capacity retention rate after the partial charge / discharge cycle is improved.

On the other hand, when the battery B and the battery D having a battery capacity of 4 Ah are compared, in the battery D using the nickel positive electrode in which the mass of Zn with respect to the mass of Ni is 5 mass%, the capacity ratio after the charge / discharge cycle is relative to the battery B. It can be seen that it is improved by 12%. This is presumably because the memory effect was suppressed as the amount of zinc added to the nickel positive electrode decreased, and the capacity retention rate after the partial charge / discharge cycle improved.
Also from this, the battery capacity is reduced (4.5 Ah or less is desirable), the battery volume (L) is decreased to increase the power density (W / L), and the Zn mass relative to the Ni mass is 5 mass% or less. When the battery is capable of discharging for 10 seconds with a discharge current exceeding 60 It using the nickel positive electrode, it can be said that the capacity retention rate after the partial charge / discharge cycle can also be maintained.

5. Examination of electrolyte concentration and lithium concentration of alkaline electrolyte Next, the effects of the electrolyte concentration and lithium concentration of the alkaline electrolyte were examined. Therefore, an electrolyte solution having an electrolyte concentration of 6.5 mol / L (6.5 N) and a Li concentration of 0.33 mol / L (0.33 N) was prepared. Next, using this electrolytic solution and the nickel positive electrode d produced as described above, a nickel-hydrogen storage battery 10 having a battery capacity of 4 Ah was produced in the same manner as described above. For comparison, a nickel-hydrogen storage battery 10 having a battery capacity of 4 Ah is produced in the same manner as described above using this electrolytic solution and the nickel positive electrode b produced as described above. It was.

Next, using these batteries E and F, a charge / discharge test is performed in the same manner as described above, and the relative value (output ratio) of the maximum outputs (W) of the batteries E and F with respect to the maximum output (W) of the battery A ( %) And the relative value (60 It discharge power density ratio) of the battery E, F output density with respect to the battery A and 60 It discharge power density (W / L) is shown in Table 4 below. The result was as shown. Furthermore, when the partial charge / discharge test was performed in the same manner as described above, and the capacity ratio after the partial charge / discharge cycle of the batteries E and F with respect to the capacity ratio after the partial charge / discharge cycle of the battery A (capacity ratio after the charge / discharge cycle) was determined, The results shown in Table 4 were obtained. Table 4 also shows the results of the battery D described above.

  As is apparent from the results in Table 4 above, an alkaline electrolyte having an alkaline electrolyte concentration of 7.0 mol / L (7.0 N) and a lithium concentration of 0.21 mol / L (0.21 N) was used. Comparing battery D with battery E using an alkaline electrolyte with an alkaline electrolyte concentration of 6.5 mol / L (6.5 N) and a lithium concentration of 0.33 mol / L (0.33 N) It can be seen that the capacity retention rate after the partial charge / discharge cycle is improved by about 30% when the alkaline electrolyte having a low electrolyte concentration and a high lithium concentration is used.

  This is because, when an alkaline electrolyte having an alkaline electrolyte concentration of 6.5 mol / L (6.5 N) and a lithium concentration of 0.33 mol / L (0.33 N) is used, the memory effect is suppressed. This is probably because the capacity retention rate after the charge / discharge cycle improved. However, even when an alkaline electrolyte having a low electrolyte concentration and a high lithium concentration is used as in the battery F, a nickel positive electrode in which the amount of zinc added is 15% by mass with respect to the amount of nickel in the positive electrode active material layer. When b is used, the capacity retention rate after the partial charge / discharge cycle is decreased, and therefore it is necessary to use a nickel positive electrode d in which the amount of zinc added is 5% by mass with respect to the amount of nickel in the positive electrode active material layer. .

  The following conclusions can be obtained by comprehensively considering the results of Tables 2 to 4 and the results of FIG. That is, the battery capacity is reduced (4.5 Ah or less is desirable), the battery volume (L) is decreased to increase the output density (W / L), and discharge is possible for 10 seconds at a discharge rate exceeding 60 It. In order to obtain a battery, it is necessary to use a nickel positive electrode whose Zn mass is 5 mass% or less with respect to Ni mass. As a result, an alkaline storage battery having a high output density (W / L), capable of discharging for 10 seconds at a discharge rate exceeding 60 It, and having an improved capacity retention rate after a partial charge / discharge cycle is obtained.

In this case, if the concentration of the alkaline electrolyte is 6.5 mol / L (6.5 N) or less and the amount of lithium (Li) contained in the alkaline electrolyte is 0.3 mol / L (0.3 N) or more, This is preferable because the memory effect is further suppressed.
Thus, since the alkaline storage battery of the present invention has a high output density regardless of its size and weight, the alkaline storage battery of the present invention has a high motor performance and a low fuel consumption hybrid vehicle (HEV). An electric vehicle (PEV) can be provided.

  In the above-described example, the battery capacity is 4 Ah, the volume ratio with respect to the battery A is 70, and the size and weight are reduced. However, even if the battery capacity is 4.5 Ah, the volume with respect to the battery A is described. Since the ratio can be sufficiently small and light when the ratio is 80, it can be said that the battery capacity is desirably 4.5 Ah or less. Further, the maximum discharge rate of the battery D capable of discharging for 10 seconds at a discharge rate exceeding 60 It is 100 It from the result of FIG. 2, but as a result of the experiment, the discharge of 10 seconds is performed even at the discharge rate of 120 It. It was possible.

6). Examination of output in the low SOC range In alkaline storage batteries used for vehicle-related applications such as hybrid vehicles (HEV) and electric vehicles (PEV), if the capacity is reduced too much by reducing the size and weight, the SOC is reduced. There was a problem that the output in the region (SOC 20% region) decreased. Therefore, in the following, the output in the low SOC region was examined.

  Therefore, the battery G using the alkaline electrolyte having the above-mentioned concentration of 6.5 mol / L (6.5 N) and the lithium concentration of 0.33 mol / L (0.33 N) and the nickel positive electrode c of 6 Ah; Using a battery E using a 4Ah nickel positive electrode d and a battery H using a 3Ah nickel positive electrode e, the output in the low SOC region was examined as follows.

  Therefore, first, in each of these batteries E, G, and H, the battery capacity (nominal capacity) is charged to 50% of the battery capacity (SOC (State Of Charge)) at a charging rate of 1 It with respect to the battery capacity (nominal capacity). Depth) was 50%). After that, 20A charge → 40A discharge → pause → 40A charge → 80A discharge → pause → 60A charge → 120A discharge → pause → 80A charge → 160A discharge → pause → 100A charge → 200A discharge The discharge was repeated for 10 minutes.

  Then, the battery voltage (V) at the time of discharging each 10 seconds is plotted against the discharge current (A), and the current value (A) when the straight line obtained by the least square method reaches 0.9V. And 0.9V was obtained as an output (W) of SOC 50%. Next, the battery was charged to 20% of the battery capacity at a charge rate of 1 It (SOC (State Of Charge): 20%). After that, 20A charge → 40A discharge → pause → 40A charge → 80A discharge → pause → 60A charge → 120A discharge → pause → 80A charge → 160A discharge → pause → 100A charge → 200A discharge In this order, charging for 20 seconds, discharging for 10 seconds, and rest for 10 minutes were repeated.

  And the output (W) of SOC20% was calculated | required similarly to the time of SOC50% mentioned above. When the output ratio (W) of SOC 20% to the output (W) of SOC 50% obtained as described above was obtained as the output ratio in the low SOC region, the results shown in Table 5 below were obtained. Further, based on the results of Table 5, the battery capacity (Ah) is plotted on the horizontal axis (X-axis), and the obtained output (W) of SOC 20% with respect to the obtained output (W) of SOC 50% (output ratio: dependence on SOC) When the vertical axis (Y-axis) is plotted, the results shown in FIG. 3 are obtained.

Next, in each of these batteries G and H, a part of repeating a cycle of charging to a voltage at which the SOC becomes 80% at a charging rate of 10 It and then discharging to a voltage at which the SOC becomes 20% at a discharging rate of 10 It. A charge / discharge cycle test was conducted. Then, such a partial charge / discharge cycle was repeated until the amount of discharged electricity reached 50 kAh. Thereafter, the battery capacity after partial charge / discharge cycle (capacity after partial charge / discharge cycle) X2 of each battery G, H was determined. Then, after calculating the capacity X2 after the partial charge / discharge cycle with respect to the initial capacity X1 as the capacity ratio after the partial charge / discharge cycle (X2 / X1), the capacity ratio after the partial charge / discharge cycle of the battery A is set to 100. The results are shown in Table 5 below, in which the capacity ratios after partial charge / discharge cycles of the batteries G and H are obtained as relative values to the battery A (capacity ratio after charge / discharge cycles). Table 5 also shows the results for battery E.

  As is apparent from the results of Table 5 and FIG. 3, in the battery H having a battery capacity of 3 Ah, the output ratio in the low SOC region (the output of SOC 20% with respect to the output of SOC 50% (SOC 20% / SOC 50%)) It can be seen that it is as small as 43, that is, the SOC dependency is greatly reduced. On the other hand, in the battery E with a battery capacity of 4 Ah, the output ratio in the low SOC region (SOC 20% output to SOC 50% output (SOC 20% / SOC 50%)) is as large as 65, that is, the SOC dependency is not so much. It turns out that it does not fall. In addition, in the battery G having a battery capacity of 6 Ah, the output ratio in the low SOC region (SOC 20% output to SOC 50% output (SOC 20% / SOC 50%)) is 80 and larger, and the SOC dependency does not decrease much. I understand that.

  In this case, as shown in FIG. 3, there is an SOC-dependent change point when the battery capacity is 4 Ah. Therefore, by controlling the battery capacity to 4 Ah or more, the SOC dependency is not lowered without reducing the SOC dependency ( It can be said that a stable output can be ensured even at an SOC of about 20%. This can be considered as an effect of increasing the lithium concentration in the alkaline electrolyte. This phenomenon has not been observed before increasing the lithium concentration, which can be considered as an effect of increasing the lithium concentration in the alkaline electrolyte.

  From the above results, the amount of zinc in the positive electrode active material layer is 5% by mass or less with respect to the mass of nickel, the concentration of the alkaline electrolyte is 6.5 mol / L (6.5N) or less, and the alkaline electrolyte is When the amount of lithium (Li) contained in the battery is 0.3 mol / L (0.3 N) or more and the battery capacity is specified to be 4 Ah or more and 4.5 Ah or less, the capacity after the charge / discharge cycle and the SOC It can be said that it is possible to obtain an alkaline storage battery excellent in both dependence characteristics.

  In the above-described embodiment, the example in which the partial charge / discharge cycle condition is set to SOC 20 to 80% has been described. However, the partial charge / discharge cycle condition may be set to SOC 20 to 80% or SOC 30 to 70%. It was revealed that the initial capacity ratio after the partial charge / discharge cycle did not change. From this, the partial charge / discharge cycle conditions may be SOC 20 to 80%, SOC 30 to 70%, or SOC 10 to 90%, but practically SOC 20 to 80%. Is desirable.

It is sectional drawing which shows typically the nickel-hydrogen storage battery of this invention. It is a graph which shows the relationship between discharge current (A) and power density (W / L). It is a graph which shows the relationship between battery capacity acquisition (Ah) and SOC dependence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Nickel electrode, 11c ... Core exposed part, 12 ... Hydrogen storage alloy electrode, 12c ... Core exposed part, 13 ... Separator, 14 ... Negative electrode collector, 15 ... Positive electrode collector, 15a ... Current collection lead part , 17 ... exterior can, 17a ... annular groove, 17b ... opening edge, 18 ... sealing body, 18a ... positive electrode cap, 18b ... valve plate, 18c ... spring, 19 ... insulating gasket

Claims (6)

An alkaline storage battery comprising an electrode group consisting of a nickel positive electrode having nickel hydroxide as a main positive electrode active material, a hydrogen storage alloy negative electrode having a hydrogen storage alloy as a negative electrode active material, and a separator together with an alkaline electrolyte in an outer can. And
In the nickel positive electrode, zinc is added to nickel hydroxide serving as a main positive electrode active material, and the amount of zinc added is 5% by mass or less based on the mass of nickel in the positive electrode active material layer,
An alkaline storage battery having a battery capacity of 4.5 Ah or less and capable of discharging exceeding a discharge rate of 60 It.   2. The alkaline storage battery according to claim 1, wherein the nickel positive electrode is one in which at least nickel hydroxide and zinc are filled in the pores of a nickel sintered substrate by impregnation treatment with an impregnation solution and alkali treatment.   The concentration of the alkaline electrolyte is 6.5 mol / L or less, and the amount of lithium (Li) contained in the alkaline electrolyte is 0.3 mol / L or more. The alkaline storage battery described in 1.   The alkaline storage battery according to any one of claims 1 to 3, wherein the alkaline electrolyte comprises sodium hydroxide, potassium hydroxide, and lithium hydroxide.   5. The alkaline storage battery according to claim 4, wherein the lowering of the battery capacity is set to 4.0 Ah to suppress a decrease in output in a low charging depth (SOC) region. 6.   When the depth of charge (SOC) reaches a voltage equivalent to 20%, discharging is stopped and charging starts, and when the depth of charge (SOC) reaches a voltage equivalent to 80%, charging is stopped and discharging starts. The alkaline storage battery according to any one of claims 1 to 5, wherein discharge control is performed.

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