JP2012099250A - Alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline storage battery capable of compaction and suppression of memory effect while maintaining high output and output stability by optimizing the stoichiometric ratio of the composition of a rare earth-Mg-Ni based hydrogen storing alloy.SOLUTION: An alkaline storage battery 10 is provided, in an outer can 17, with an electrode group consisting of a negative electrode 11 containing a hydrogen storing alloy as a main component, a positive electrode 12 containing a nickel hydroxide as a main component, and a separator 13 together with an electrolytic solution. The hydrogen storing alloy is represented by a general formula LaNdReMgNiAlT(Re: at least one kind of element selected from rare earth elements containing Y (excepting La and Nd), T: at least one kind of element selected from Co, Mn, Zn), where following conditions are satisfied; 0.13≤x≤0.34, 0.14≤y≤0.60, 0.10≤z≤0.15, 3.50≤n≤3.75, 0.13≤m≤0.22, v≥0.

Description

  The present invention relates to an alkaline storage battery having a negative electrode with a hydrogen storage alloy suitable for applications (high power / high current applications) that require high output and large current discharge, such as a hybrid electric vehicle (HEV).

Alkaline batteries with a hydrogen storage alloy in the negative electrode are used for applications requiring high power and large current discharge (high power / high current applications) such as for HEVs because they are excellent in safety. . By the way, generally, the hydrogen storage alloy used for the negative electrode of an alkaline storage battery is composed of a single phase of AB ₂ type structure or AB ₅ type structure. However, high output and large current discharge performance far exceeding the conventional range have been demanded, and the AB ₂ type structure and the AB ₅ type structure are combined as in the rare earth-Mg—Ni based hydrogen storage alloy. A structure including an A ₂ B ₇ type structure or an A ₅ B ₁₉ type structure as a main phase has been proposed. In the AB ₂ type structure, AB ₅ type structure, A ₂ B ₇ type structure, and A ₅ B ₁₉ type structure, the A component represents the sum of the stoichiometric ratio of the rare earth and Mg, the B component is the Ni component, and the rare earth And the sum of the stoichiometric ratios of components other than Mg.

Here, in the rare earth-Mg—Ni-based hydrogen storage alloy, the structure is transformed by the stoichiometric ratio of the B component (mainly Ni), and the A ₂ B ₇ type increases as the stoichiometric ratio of the B component increases. A ₅ B ₁₉ type structure is easily constructed from the structure. In this case, the A ₅ B ₁₉ type structure includes a structure in which the AB ₂ type structure and the AB ₅ type structure are stacked with a period of 3 layers, so that the nickel ratio per unit crystal lattice can be improved. Is. For this reason, an alkaline storage battery that includes a rare earth-Mg-Ni-based hydrogen storage alloy that includes an A ₅ B ₁₉ type structure as a main phase (including a relatively large amount) as a negative electrode is a battery that exhibits particularly high output, It has been proposed in Patent Literature 1, Patent Literature 2, Patent Literature 3, and the like.

  In recent years, in alkaline storage batteries used for HEV applications and the like, in addition to the high output and high current discharge performance exceeding the conventional range as described above, cost reduction and partial charge / discharge use range (for example, SOC (State Of Charge)) Is in the range of 20 to 80%), and further improvement in performance such as suppression of the memory effect has been desired.

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

  Here, in response to the demand for cost reduction, use of a rare earth-Mg-Ni hydrogen storage alloy in which rare earth of the rare earth-Mg-Ni alloy is replaced with La, which is low in cost, has been studied. However, when the La content is increased, a new problem arises in that the flatness of the hydrogen equilibrium pressure of the rare earth-Mg-Ni-based hydrogen storage alloy, that is, the output stability is significantly reduced. Therefore, as a result of various attempts to control the crystal of the hydrogen storage alloy by component design, in the case of a rare earth-Mg—Ni-based hydrogen storage alloy containing a predetermined amount of La, by setting a predetermined amount of Mg, It has been found that the structure is stabilized and the flatness of the hydrogen equilibrium pressure, that is, the output stability can be improved.

  In this case, in the rare earth-Mg—Ni-based hydrogen storage alloy containing a predetermined amount of La, if the Mg content is increased, then the pulverization of the hydrogen storage alloy is accelerated, and the hydrogen storage alloy is deteriorated. A new problem has arisen that is easy to progress. In addition, in the case of a rare earth-Mg-Ni alloy containing a predetermined amount of La, by adding a predetermined amount of Al, the crystal structure of the hydrogen storage alloy is stabilized, and the flatness of the hydrogen equilibrium pressure, that is, It was found that the output stability can be improved.

  However, Al contained in the rare earth-Mg-Ni-based hydrogen storage alloy has a problem that it easily elutes into the alkaline electrolyte because the standard electrode potential is lower than that of Ni. For this reason, when an alkaline storage battery is constructed using a rare earth-Mg-Ni hydrogen storage alloy with an increased Al content for the negative electrode, Al is eluted from the rare earth-Mg-Ni hydrogen storage alloy into the alkaline electrolyte. However, this has moved to the nickel positive electrode and entered the positive electrode active material, resulting in a new problem that the durability (output durability) of the alkaline storage battery is lowered.

  In addition, when the size of the alkaline storage battery is reduced (downsized), there is a problem that the output stability is significantly reduced due to the size reduction of the hydrogen storage alloy negative electrode. Furthermore, it has been found that the memory effect is suppressed by containing a predetermined amount of Zn in the positive electrode active material. However, when the Zn amount is increased, the battery voltage rises quickly during charging, and output stability is improved. There was a problem that would decrease.

  Therefore, the present invention has been made to solve the above-described problems, and optimizes the stoichiometric ratio of the composition of the rare earth-Mg-Ni-based hydrogen storage alloy while maintaining high output and output stability. An object of the present invention is to provide an alkaline storage battery capable of reducing the battery size and reducing the memory effect.

The alkaline storage battery of the present invention comprises an electrode group consisting of a hydrogen storage alloy negative electrode mainly composed of a hydrogen storage alloy, a nickel positive electrode mainly composed of nickel hydroxide, and a separator in an outer can together with an alkaline electrolyte. Yes. Then, to solve the above problems, the hydrogen storage alloy, the general formula _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v (Re: selected from excluding rare earth elements (La and Nd including Y) And at least one element selected from T, Co, Mn, and Zn), and 0.13 ≦ x ≦ 0.34, 0.14 ≦ y ≦ 0.60 0.10 ≦ z ≦ 0.15, 3.50 ≦ n ≦ 3.75, 0.13 ≦ m ≦ 0.22, and v ≧ 0.

Here, the general formula _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v (Re: at least one element selected from rare earth elements (except La and Nd) including Y, T: Co , At least one element selected from Mn and Zn), 0.13 ≦ x ≦ 0.34, 0.14 ≦ y ≦ 0.60, 0 .10 ≦ z ≦ 0.15, 3.50 ≦ n ≦ 3.75, 0.13 ≦ m ≦ 0.22, and v ≧ 0 satisfying the requirements of the prior art by using a hydrogen storage alloy for the negative electrode. It is possible to provide an alkaline storage battery that is low in output and stable in output, and can maintain high output performance even in a battery size reduction and memory effect suppression specification.

  In this case, the La stoichiometric ratio x is 0.13 or more and 0.34 or less (0.13 ≦ x ≦ 0.34), and the Nd stoichiometric ratio y is 0.14 or more and 0.60. Below (0.14 ≦ y ≦ 0.60), it is possible to meet the demand for cost reduction and to achieve high output characteristics. On the other hand, when the Mg stoichiometric ratio z is 0.16 or more, the hydrogen storage alloy is pulverized and the corrosion resistance is lowered. On the other hand, it was found that when the Mg stoichiometric ratio z is 0.15 or less, the corrosion resistance characteristics are not so lowered. In this case, if the Mg stoichiometric ratio z is smaller than 0.10, the equilibrium pressure of the hydrogen storage alloy is lowered and the function as a battery is impaired. Consequently, the Mg stoichiometric ratio z is 0.10. From the above, it is desirable that 0.15 or less (0.10 ≦ z ≦ 0.15).

  Further, in the rare earth-Mg-Ni hydrogen storage alloy, when the stoichiometric ratio (n) of the B component (Ni, rare earth, other than Mg) to the A component (rare earth element and Mg) is as low as 3.45, the hydrogen equilibrium It became clear that the pressure decreased and the SOC 20% output and the SOC 50% output decreased. On the other hand, when the stoichiometric ratio (n) is greater than 3.75, it has been clarified that the increase in the hydrogen equilibrium pressure increases and the corrosion resistance decreases. On the other hand, if the stoichiometric ratio (n) of the B component to the A component is within the range of 3.50 or more and 3.75 or less (3.50 ≦ n ≦ 3.75), the SOC 20% output and the SOC 50 % Output has been improved and the corrosion resistance characteristics can be maintained. From these facts, it can be said that the stoichiometric ratio (n) of the B component to the A component is preferably regulated to 3.50 or more and 3.75 or less (3.50 ≦ n ≦ 3.75).

  Further, when the stoichiometric ratio (m) of Al added to the hydrogen storage alloy is more than 0.22, a large amount of Al is eluted from the hydrogen storage alloy into the alkaline electrolyte, and this is transferred to the nickel positive electrode to be active in the positive electrode. There is a problem that the material enters the substance and the durability of the alkaline storage battery is lowered. On the other hand, if the stoichiometric ratio (m) of Al added to the hydrogen storage alloy is less than 0.13, the crystal structure becomes unstable, the plateau property decreases, and it is difficult to obtain a stable output. Become. For this reason, it can be said that the stoichiometric ratio (m) of Al is desirably regulated to 0.13 or more and 0.22 or less (0.13 ≦ m ≦ 0.22).

Taken together consideration of the above results, the general formula _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v (Re: rare earth elements including Y (other than La and Nd) at least one selected from Element, T: at least one element selected from Co, Mn, and Zn), and 0.13 ≦ x ≦ 0.34, 0.14 ≦ y ≦ 0.60, 0.10 ≦ z. It is desirable to use, for the negative electrode, a hydrogen storage alloy that satisfies the conditions of ≦ 0.15, 3.50 ≦ n ≦ 3.75, 0.13 ≦ m ≦ 0.22, and v ≧ 0. Note that when the element T is selected from Co, Mn, and Zn, each element has little influence on the performance related to hydrogen storage, and the same effect as in the case of no addition can be obtained. In this case, the upper limit value of the stoichiometric ratio (v) of the element T is desirably 0.10.

Here, in an alkaline storage battery using a hydrogen storage alloy as a negative electrode, the negative electrode structure α as the ratio β / α of the negative electrode capacity α (Ah) and the negative electrode surface area β (cm ² ) becomes 60 cm ² / Ah or more. As a result, the area facing the nickel positive electrode is inevitably increased and the battery resistance is reduced, so that high output can be achieved. When such a high power battery design (60 cm ² / Ah ≦ β / α) is employed, it is preferable to employ the hydrogen storage alloy of the present invention for the negative electrode.

  Moreover, the memory effect is suppressed by reducing the addition amount of zinc contained in the positive electrode active material to 2.0% by mass or less with respect to the mass of nickel in the positive electrode. This is because the voltage gradient during charging / discharging increases and the voltage difference in a predetermined SOC range increases due to a decrease in the amount of zinc contained in the positive electrode active material. As an adverse effect, a decrease in output in a low SOC region becomes remarkable. In order to improve this, it is preferable to employ the hydrogen storage alloy of the present invention for the negative electrode.

  In the present invention, by using an inexpensive hydrogen storage alloy that maintains high output and output stability, an alkaline storage battery that can maintain output performance even in a small battery size and in a memory effect suppression specification is provided. Is possible.

It is sectional drawing which shows typically the alkaline storage battery of one Example 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. Hydrogen storage alloy The hydrogen storage alloy was produced as follows. In this case, first, lanthanum (La), neodymium (Nd), samarium (Sm), magnesium (Mg), nickel (Ni), and aluminum (Al) are mixed at a predetermined molar ratio, and this mixture is mixed with argon gas. dissolved in an atmosphere, which melt quenching composition formula is _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v ( where a rare earth element Re in the formula, except for lanthanum (La), neodymium (Nd) Ingots of hydrogen storage alloys a1 to l1 expressed as follows: T is at least one element selected from Co, Mn, and Zn. Thereafter, the masses of these hydrogen storage alloys a1 to l1 are coarsely pulverized and then mechanically pulverized in an inert gas atmosphere to obtain a hydrogen storage having a particle size (D50) of 25 μm at a volume cumulative frequency of 50%. Alloy powder was prepared.

When the compositions of these hydrogen storage alloys a1 to l1 are analyzed by high frequency plasma spectroscopy (ICP), the composition formula of the hydrogen storage alloy a1 is La _0.29 Nd _0.20 Sm _0.41 Mg _0.10 Ni as shown in Table 1 below. It was found to be represented by _3.48 Al _0.15 . Similarly, the composition formula of the hydrogen storage alloy b1 is represented by La _0.32 Nd _0.17 Sm _0.40 Mg _0.11 Ni _3.47 Al _0.13 , and the composition of the hydrogen storage alloy c1 is represented by La _0.34 Nd _0.15 Sm _0.40 Mg _0.11 Ni _3.52 Al _0.15. The hydrogen storage alloy d1 is represented by the composition formula La _0.32 Nd _0.22 Sm _0.35 Mg _0.11 Ni _3.50 Al _0.17 , and the hydrogen storage alloy e1 is represented by the composition formula La _0.31 Nd _0.18 Sm _0.40 Mg _0.11 Ni _3.54 Al _0.17 It turns out that.

The hydrogen storage alloy f1 is represented by a composition formula of La _0.13 Nd _0.44 Sm _0.32 Mg _0.11 Ni _3.38 Al _0.17 , and the hydrogen storage alloy g1 is represented by a composition formula of La _0.24 Nd _0.25 Sm _0.40 Mg _0.11 Ni _3.49 Al _0.22 , The hydrogen storage alloy h1 was found to have a compositional formula represented by Nd _0.89 Mg _0.11 Ni _3.33 Al _0.17 . Further, the hydrogen storage alloy i1 is represented by La _0.52 Sm _0.36 Mg _0.12 Ni _3.60 Al _0.09 , the hydrogen storage alloy j1 is represented by La _0.18 Nd _0.36 Sm _0.35 Mg _0.11 Ni _3.28 Al _0.17 , and the hydrogen storage alloy k1 is La _0.43 Nd. _0.44 Mg _0.13 Ni _3.69 Al _0.10 , and the hydrogen storage alloy 11 was found to be La _0.38 Nd _0.34 Sm _0.13 Mg _0.15 Ni _3.47 Al _0.09 .

At least one in Table 1 below, the composition formula of each hydrogen absorbing alloy _{a1~l1 La x Nd y Re 1-} xyz Mg z Ni nmv Al m T v (T is selected from among Co, Mn, and Zn The value of the molar ratio (B / A = n) of the B component (Ni, Al, and T) to the A component (rare earth elements (La, Nd, Re) and Mg) and the molar ratio of La (X), Nd molar ratio (y), Re (Sm in this case) molar ratio (1-xyz), Mg molar ratio (z), Ni molar ratio (nmv) ), The molar ratio of Al (m) and the molar ratio of T (v).

2. Hydrogen Storage Alloy Negative Electrode Next, the hydrogen storage alloy negative electrode 11 was manufactured as follows using the powders of the hydrogen storage alloys a1 to l1 manufactured as described above.
In this case, first, a hydrogen storage alloy slurry is prepared by mixing and kneading the powders of the hydrogen storage alloys a1 to 11 prepared as described above, a water-soluble binder, a thermoplastic elastomer, and a carbon-based conductive agent. Produced. In this case, as the water-soluble binder, a material composed of 0.1% by mass of CMC (carboxymethyl cellulose) and water (or pure water) was used. Further, styrene butadiene latex (SBR) was used as the thermoplastic elastomer. Further, ketjen black was used as the carbon-based conductive agent.

Next, the hydrogen storage alloy slurry prepared as described above is applied to a negative electrode conductive core (a nickel-plated soft steel porous substrate (punching metal)) with a predetermined filling density (for example, 5.0 g / The active material layer was formed by applying and drying to a thickness of cm ³ ), and then rolling to a predetermined thickness. Thereafter, the hydrogen storage alloy negative electrode capacity is 12 Ah, and the hydrogen storage alloy negative electrode surface area is 720 cm ² (negative electrode surface area / negative electrode capacity = 60 cm ² / Ah). , B, c, d, e, f, g, h, i, j, k, l), respectively.

  In this case, the hydrogen storage alloy negative electrode a was prepared using the hydrogen storage alloy a1 powder. Similarly, a hydrogen storage alloy negative electrode b is prepared using the hydrogen storage alloy b1 powder, a hydrogen storage alloy negative electrode c is prepared using the hydrogen storage alloy c1 powder, and the hydrogen storage alloy d1 powder is prepared. The hydrogen storage alloy negative electrode d was prepared using the hydrogen storage alloy e1 powder, the hydrogen storage alloy negative electrode e was prepared using the hydrogen storage alloy e1 powder, and the hydrogen storage alloy negative electrode was prepared using the hydrogen storage alloy f1 powder. f.

  Also, a hydrogen storage alloy negative electrode g was prepared using the hydrogen storage alloy g1 powder, a hydrogen storage alloy negative electrode h was prepared using the hydrogen storage alloy h1 powder, and a hydrogen storage alloy i1 powder was used. The hydrogen storage alloy negative electrode i, the hydrogen storage alloy j1 powder prepared using the hydrogen storage alloy negative electrode j, and the hydrogen storage alloy k1 powder prepared using the hydrogen storage alloy k1 powder. It was. Furthermore, what was produced using the powder of hydrogen storage alloy l1 was made into the hydrogen storage alloy negative electrode l.

3. Nickel positive electrode The nickel positive electrode 12 was produced as follows.
First, a porous nickel sintered substrate having a porosity of about 85% is immersed in a mixed aqueous solution of nickel nitrate and cobalt nitrate having a specific gravity of 1.75, and nickel salt and cobalt are placed in the pores of the porous nickel sintered substrate. Salt was retained. Thereafter, the porous nickel sintered substrate was immersed in a 25% by mass sodium hydroxide (NaOH) aqueous solution to convert the nickel salt and the cobalt salt into nickel hydroxide and cobalt hydroxide, respectively.
Next, after sufficiently washing with water to remove the alkaline solution, drying was performed, and the active material mainly composed of nickel hydroxide was filled into the pores of the porous nickel sintered substrate. Such an active material filling operation is repeated a predetermined number of times (for example, 6 times) so that the filling density of the active material mainly composed of nickel hydroxide in the pores of the porous sintered substrate becomes 2.5 g / cm ^3. Filled. Then, after making it dry at room temperature, it cut | disconnected to the predetermined dimension and the nickel positive electrode 12 was produced.

4). Nickel-hydrogen storage battery The nickel-hydrogen storage battery 10 was produced as follows.
First, the hydrogen storage alloy negative electrode 11 and the nickel positive electrode 12 manufactured as described above are used, and a separator 13 made of a nonwoven fabric containing polypropylene fibers is interposed between them, and the spiral electrode group is wound. Was made. The core exposed portion 11c of the hydrogen storage alloy negative electrode 11 is exposed at the lower part of the spiral electrode group thus fabricated, and the core exposed part 12c of the nickel positive electrode 12 is exposed at the upper portion thereof. ing. Next, the negative electrode current collector 14 is welded to the core exposed portion 11c exposed at the lower end surface of the obtained spiral electrode group, and the core exposed portion 12c of the nickel positive electrode 12 exposed at the upper end surface of the spiral electrode group. A positive electrode current collector 15 was welded onto the electrode body to obtain an electrode body.

  Next, after the obtained electrode body is housed in a bottomed cylindrical outer can 16 in which iron is nickel-plated (the outer surface of the bottom surface becomes a negative electrode external terminal) 16, the negative electrode current collector 14 is attached to the outer can 16. Welded to the inner bottom. On the other hand, a current collecting lead portion 15a extending from the positive electrode current collector 15 and a sealing plate 17 serving as a positive electrode terminal and having an insulating gasket 18 attached to the outer peripheral portion were welded. The sealing plate 17 is provided with a positive electrode cap 17a, and a pressure valve 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, the electrolytic solution was injected, and the outer peripheral portion of the sealing plate 17 was mounted on the annular groove portion 16 a formed on the upper portion of the outer can 16. An insulating gasket 18 was placed. Thereafter, the opening edge 16b of the outer can 16 is caulked, and an alkaline electrolyte (for example, composed of 30% by mass potassium hydroxide (KOH) aqueous solution) is put in the outer can 16 at 2.5 g per battery capacity (Ah) ( 2.5 g / Ah) was injected to produce a nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L).

  In this case, the battery A was prepared using the hydrogen storage alloy negative electrode a, the battery B was manufactured using the hydrogen storage alloy negative electrode b, and the battery C was manufactured using the hydrogen storage alloy negative electrode c. A battery D was prepared using the hydrogen storage alloy negative electrode d, a battery E was manufactured using the hydrogen storage alloy negative electrode e, and a battery F was manufactured using the hydrogen storage alloy negative electrode f. In addition, a battery prepared using the hydrogen storage alloy negative electrode g is referred to as a battery G, a battery prepared using the hydrogen storage alloy negative electrode h is referred to as a battery H, and a battery manufactured using the hydrogen storage alloy negative electrode i is referred to as a battery I. A battery J was prepared using the hydrogen storage alloy negative electrode j, and a battery K was prepared using the hydrogen storage alloy negative electrode k. Further, a battery L was prepared using the hydrogen storage alloy negative electrode 1.

5. Battery test (1) Activation Activation was performed as follows. That is, the nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L) manufactured as described above has a peak voltage of 60 when left unattended. Then, the battery is charged to SOC 120% with a charging current of 1 It in a temperature atmosphere of 25 ° C., and rested in a temperature atmosphere of 25 ° C. for 1 hour. Then, after being allowed to stand for 24 hours in a temperature atmosphere at 70 ° C., a cycle in which the battery voltage was 0.3 V with a discharge current of 1 It in a temperature atmosphere of 45 ° C. was repeated two times.

(2) Output characteristics (-10 ° C assist output)
In order to investigate the output stability, the output characteristics (−10 ° C. assist output) were determined as follows.
First, the nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L) activated as described above is charged at 1 It in a temperature atmosphere of 25 ° C. After charging up to 50% SOC, the battery was rested in a temperature atmosphere of −10 ° C. for 1 hour. Next, the battery was charged for 20 seconds at an arbitrary charging rate in a temperature atmosphere of −10 ° C., and then rested for 30 minutes in a temperature atmosphere of −10 ° C. Thereafter, the battery was discharged for 10 seconds at an arbitrary discharge rate in a temperature atmosphere of −10 ° C., and then rested in a temperature atmosphere of −10 ° C. for 30 minutes. In such a temperature atmosphere of −10 ° C., charging for 20 seconds at an arbitrary charging rate, pause for 30 minutes, discharging for 10 seconds at an arbitrary discharge rate, and pause for 30 minutes in a temperature atmosphere of −10 ° C. were repeated. .

  In this case, the charging rate is increased in the order of 0.8 It → 1.7 It → 2.5 It → 3.3 It → 4.2 It, and the arbitrary discharging rate is 1.7 It → 3. The discharge current is increased in the order of 3 It → 5.0 It → 6.7 It → 8.3 It so that 0.8 It charge → 1.7 It discharge → 1.7 It charge → 3.3 It discharge → 2.5 It charge → 5.0 It discharge → 3.3 It charge → 6.7 It discharge → 4.2 It charge → 8.3 It discharge / discharge treatment was performed. At this time, the battery voltage (V) of each battery at the time when 10 seconds passed at each discharge rate was measured for each discharge rate. Next, the measured battery voltage (V) of each of the batteries A, B, C, D, E, F, G, H, I, J, K, and L at the time when the measured 10 seconds elapsed is the discharge current value for each discharge rate. 2 is plotted to obtain an approximate curve showing the relationship between the battery voltage and the discharge current value, and the discharge current value at 0.9 V in the approximate curve is expressed as an SOC 50% output characteristic at −10 ° C. (−10 ° C. As a result, the results shown in Table 2 below were obtained.

  In addition, the activated nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L) is SOC 20% with a charging current of 1 It in a temperature atmosphere of 25 ° C. When the SOC 20% output characteristics (SOC 20% assist output at −10 ° C.) were obtained in the same manner as above except that the battery was charged up to the above, the results shown in Table 2 below were obtained. In Table 2 below, SOC 50% assist output and SOC 20% assist output at −10 ° C. of the battery H are defined as 100, and other batteries A, B, C, D, E, F, G, I, J , K, L assist outputs are shown as a ratio to them.

(3) Negative electrode discharge reserve (corrosion resistance)
Next, using the above-described nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L), the negative electrode discharge reserve (corrosion resistance characteristics) is performed as follows. Asked. In this case, first, each nickel-hydrogen storage battery 10 (A, B, C, D, E, F, G, H, I, J, K, L) is opened to make the electrolyte rich state and open. A reference electrode (Hg / HgO) is arranged in each battery. Next, after the positive electrode active material is completely discharged, the negative electrode potential is 0.3 V (absolute value) with respect to the reference electrode (Hg / HgO) at a discharge current of 1.0 It in a temperature atmosphere of 25 ° C. Then, the capacity at the time of 1 It discharge of the negative electrode was determined from the discharge time at this time.

  Then, after stopping the discharge for 10 minutes in a temperature atmosphere of 25 ° C., until the negative electrode potential becomes 0.3 V (absolute value) with respect to the reference electrode (Hg / HgO) with a discharge current of 0.1 It. It was made to discharge and the capacity | capacitance at the time of 0.1 It discharge of the negative electrode was calculated | required from the discharge time at this time. Then, the sum of the obtained negative electrode discharge capacity at 1 It discharge and the negative electrode discharge capacity at 0.1 It discharge (negative electrode discharge reserve) is obtained, and the sum of these negative electrode discharge capacities with respect to the theoretical capacity of the hydrogen storage alloy negative electrode (negative electrode discharge reserve). ) Ratio (negative electrode discharge reserve / negative electrode theoretical capacity) was determined as the negative electrode oxidation amount. Then, when the electrochemical oxidation amount per negative electrode surface area (negative electrode oxidation amount × average particle size) as a corrosion resistance index was determined from the determined negative electrode oxidation amount as a corrosion resistance index, the results shown in Table 2 below were obtained. .

  In Table 2 below, the amount of electrochemical oxidation per surface area of the negative electrode h of the battery H is defined as 100, and other batteries A, B, C, D, E, F, G, I, J, K, The electrochemical oxidation amount (negative electrode oxidation amount × average particle size) of the negative electrodes a, b, c, d, e, f, g, i, j, k, and l of L is shown as a ratio to that.

6). Test results (1) Regarding the stoichiometric ratio (x) of La and the stoichiometric ratio (y) of Nd in the composition of the hydrogen storage alloy Here, as in the negative electrode h used in the battery H, the rare earth is replaced with La. When using a hydrogen storage alloy h1 that does not occur, the price of the hydrogen storage alloy h1 becomes expensive, so it is not possible to meet the demand for cost reduction, so use a hydrogen storage alloy that does not replace rare earth with La. Is not preferred.

  On the other hand, in order to meet the demand for cost reduction, when using a rare earth-Mg-Ni hydrogen storage alloy in which the rare earth of the rare earth-Mg-Ni alloy is replaced with La, which is low cost, the batteries I, K, and L are used. When the La content is increased as in the negative electrodes i, k, and l used (the stoichiometric ratio x of La is larger as 0.52, 0.43, and 0.38), the SOC is 20% than that of the battery H. It can be seen that the output and SOC 50% output decrease. In addition, like the negative electrode j used for the battery J, when the La content is decreased (La stoichiometric ratio x is 0.18), the SOC 20% output and the SOC 50% output are compared with the battery H. It can be seen that does not decrease so much.

  On the other hand, as in the negative electrodes a to g used in the batteries A to G, the stoichiometric ratio x of La is 0.13 or more, 0.34 or less (0.13 ≦ x ≦ 0.34), and Nd When the stoichiometric ratio y is 0.14 or more and 0.60 or less (0.14 ≦ y ≦ 0.60), the SOC 20% output and the SOC 50% output are equal to or higher than those of the battery H. I understand that there is. From this, the stoichiometric ratio x of La is 0.13 or more, 0.34 or less (0.13 ≦ x ≦ 0.34), and the stoichiometric ratio y of Nd is 0.14 or more. By using a hydrogen storage alloy that is 60 or less (0.14 ≦ y ≦ 0.60), it is possible to meet the demand for cost reduction and achieve high output characteristics.

(2) About the stoichiometric ratio (z) of Mg in the composition of the hydrogen storage alloy As in the negative electrodes a to l used in the batteries A to L, the stoichiometric ratio z of Mg is 0.10 or more and 0.15 or less. It turns out that corrosion resistance is favorable in it being (0.10 <= z <= 0.15). From this, it can be said that it is desirable to use a hydrogen storage alloy having a Mg stoichiometric ratio z of 0.10 or more and 0.15 or less (0.10 ≦ z ≦ 0.15).

(3) Regarding the stoichiometric ratio (n) of the B component to the A component in the composition of the hydrogen storage alloy As in the negative electrode j used in the battery J, the stoichiometric ratio x of La is 0.13 or more and 0.34 Even below (0.13 ≦ x ≦ 0.34), if the stoichiometric ratio (n) of the B component to the A component is as low as 3.45, the SOC 20% output and the SOC 50% output are reduced. I understand. This is presumably because the hydrogen equilibrium pressure decreases when the stoichiometric ratio (n) is less than 3.50.
On the other hand, as in the negative electrodes a to g used in the batteries A to G, the stoichiometric ratio (n) of the B component to the A component is 3.50 or more and 3.75 or less (3.50 ≦ n ≦ 3.75). ), The SOC 20% output and the SOC 50% output are improved and the corrosion resistance characteristics can be maintained. Therefore, the stoichiometric ratio (n) of the B component to the A component is 3.50 or more and 3.75. It can be said that it is desirable to restrict to the following (3.50 ≦ n ≦ 3.75).

(4) About the stoichiometric ratio (m) of Al in the composition of the hydrogen storage alloy When the stoichiometric ratio (m) of Al exceeds 0.23, a large amount of Al is eluted from the hydrogen storage alloy into the alkaline electrolyte, This moves to the nickel positive electrode and enters the positive electrode active material, causing a problem that the durability of the alkaline storage battery is lowered. On the other hand, if the Al stoichiometric ratio (m) is less than 0.13, the crystal structure becomes unstable, the plateau property is lowered, and it becomes difficult to obtain a stable output. For this reason, it can be said that the stoichiometric ratio (m) of Al is desirably regulated to 0.13 or more and 0.22 or less (0.13 ≦ m ≦ 0.22).

Taken together consideration of the above results, the general formula _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v (Re: rare earth elements including Y (other than La and Nd) at least one selected from Element, T: at least one element selected from Co, Mn, and Zn), and 0.13 ≦ x ≦ 0.34, 0.14 ≦ y ≦ 0.60, 0.10 ≦ z. ≦ 0.15, 3.50 ≦ n ≦ 3.75, 0.13 ≦ m ≦ 0.22, v ≧ 0 satisfying the requirements of high output and stable output by using hydrogen storage alloy for negative electrode In addition, it is possible to provide an alkaline storage battery having an inexpensive hydrogen storage alloy negative electrode, and to maintain output performance even in a battery size down and memory effect suppression specification.

  In the above-described embodiment, the example using the hydrogen storage alloy in which the element T is not added (v = 0) has been described. However, even if the element T is selected from Co, Mn, and Zn, it may be added. The same effect as in the case of addition can be brought out. In this case, it is desirable that the upper limit value of the stoichiometric ratio (v) of the element T is 0.10. In the above-described embodiment, an example in which samarium (Sm) is used as a rare earth element excluding La and Nd has been described. However, praseodymium (Pr) may be used instead of samarium (Sm). In this case, the amount of praseodymium (Pr) added may be approximately the same as that of samarium (Sm).

Furthermore, in an alkaline storage battery using a hydrogen storage alloy for the negative electrode, the ratio β / α between the negative electrode capacity α (Ah) and the negative electrode surface area β (cm ² ) is increased (particularly β / α is 60 cm ² / Ah or more). Along with this, the structure of the negative electrode becomes thin and long, the area facing the nickel positive electrode inevitably increases, and the battery resistance also decreases, enabling high output. When such a high-power battery design (60 cm ² / Ah ≦ β / α) is employed, the above-described hydrogen storage alloy of the present invention is preferably employed for the negative electrode.

  Moreover, the memory effect is suppressed by reducing the addition amount of zinc contained in the positive electrode active material to 2.0% by mass or less with respect to the mass of nickel in the positive electrode. This is because the voltage gradient during charging / discharging increases and the voltage difference in a predetermined SOC range increases due to a decrease in the amount of zinc contained in the positive electrode active material. As an adverse effect, a decrease in output in a low SOC region becomes remarkable. In order to improve this, it is preferable to employ the hydrogen storage alloy of the present invention for the negative electrode.

DESCRIPTION OF SYMBOLS 11 ... Hydrogen storage alloy negative electrode, 11c ... Core exposed part, 12 ... Nickel positive electrode, 12c ... Core exposed part, 13 ... Separator, 14 ... Negative electrode collector, 15 ... Positive electrode collector, 15a ... Lead for positive electrode, DESCRIPTION OF SYMBOLS 16 ... Exterior can, 16a ... Circular groove part, 16b ... Opening edge, 17 ... Sealing plate, 17a ... Positive electrode cap, 17b ... Valve plate, 17c ... Spring, 18 ... Insulation gasket

Claims (3)

An alkaline storage battery comprising an electrode group consisting of a hydrogen storage alloy negative electrode mainly composed of a hydrogen storage alloy, a nickel positive electrode mainly composed of nickel hydroxide, and a separator together with an alkaline electrolyte in an outer can,
The hydrogen storage alloy is represented by the general formula is _{La x Nd y Re 1-xyz} Mg z Ni nmv Al m T v (Re: at least one element selected from rare earth elements (except La and Nd) including Y, T: at least one element selected from Co, Mn, and Zn), and 0.13 ≦ x ≦ 0.34, 0.14 ≦ y ≦ 0.60, 0.10 ≦ z ≦ 0 .15, 3.50 ≦ n ≦ 3.75, 0.13 ≦ m ≦ 0.22, and v ≧ 0. When the negative electrode capacity of the hydrogen storage alloy negative electrode is α (Ah) and the negative electrode surface area of the hydrogen storage alloy negative electrode is β (cm ² ), the ratio of the negative electrode surface area to the negative electrode capacity (β / α) is 60 cm ² / It is Ah or more, The alkaline storage battery of Claim 1 characterized by the above-mentioned.   The alkaline storage battery according to claim 1 or 2, wherein a content of zinc (Zn) contained in the nickel positive electrode is 2.0 mass% or less with respect to a content of nickel (Ni). .

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