JP2014229593A - Alkali storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali storage battery which is inexpensive, and has a good discharge output characteristic and an excellent high-temperature durability.SOLUTION: An alkali storage battery comprises a negative electrode of a hydrogen-absorbable alloy which includes La as a main rare earth element, and is expressed by the general formula (LaLn)MgNiT(where T is selected from a group consisting of Al, Co, Mn, and Zn; Ln is at least one element selected from a group consisting of rare earth elements except La, and Y; x>y; 0.09≤z≤0.14; 3.65≤t≤3.80; and 0.05≤u≤0.25). The hydrogen-absorbable alloy includes an A5B19 type structure of hexagonal crystal (2H) system, an A5B19 type structure of trigonal crystal (3R) system, and an A2B7 type structure. In intensity peak of powder X-ray diffraction with Cu-Kα rays, the A5B19 type crystal structure of 2H system is larger than the A5B19 type crystal structure of 3R system and the A2B7 type structure.

Description

  The present invention relates to an alkaline storage battery using a hydrogen storage alloy negative electrode.

  An alkaline storage battery such as a nickel metal hydride storage battery is designed such that the electrode plate capacity of the negative electrode is higher than the electrode plate capacity of the positive electrode. This is to ensure a charge reserve for preventing hydrogen generation during overcharge and a discharge reserve for preventing oxygen generation during overdischarge in the negative electrode. On the other hand, when the material in the battery (positive electrode / negative electrode material, other materials) is oxidized due to repeated charge / discharge, etc., the discharge reserve increases / the charge reserve decreases. In addition, the charge reserve decreases due to the oxidative deterioration of the negative electrode alloy.If the charge reserve is eventually depleted, hydrogen is generated from the negative electrode during overcharge, and the electrolyte retained by the separator is depleted due to leakage due to the gas pressure increase. Charge / discharge is not possible.

Mg-containing hydrogen storage alloys having an A2B7 type crystal structure or an A5B19 type crystal structure have been studied from the viewpoint of increasing the durability and capacity of the hydrogen storage alloy for controlling the amount of stored discharge reserve (the following patent documents) 1-3). As the hydrogen storage alloy having the A2B7 type crystal structure, for example, a Ce ₂ Ni ₇ type hexagonal crystal (2H) crystal structure in which the AB2 type crystal structure and the AB5 type crystal structure overlap each other with a period of two layers is known. Yes. The hydrogen storage alloy having an A5B19 crystal structure includes, for example, a Ce ₂ Co ₁₉ type trigonal (3R) crystal structure in which an AB2 type crystal structure and an AB5 type crystal structure are stacked with a period of three layers, and an AB2 type For example, a Pr ₅ Co ₁₉ type hexagonal (2H) crystal structure in which the crystal structure and the AB5 type crystal structure overlap each other with a period of two layers is known.

  The hydrogen storage alloy with A2B7 crystal structure can improve the cycle life characteristics of hydrogen storage / release, but the high current discharge characteristics (assist output) is insufficient and the high output exceeds the conventional range. Satisfactory characteristics cannot be obtained for use. The hydrogen storage alloy having the A5B19 type crystal structure can increase the nickel ratio per unit crystal lattice and increase the active sites that promote the adsorption of hydrogen molecules and the dissociation into hydrogen atoms. The gap between atoms becomes smaller and the hydrogen storage pressure rises. For this reason, when a hydrogen storage alloy having an A5B19 crystal structure is used for charging and discharging with a large current, pulverization of the hydrogen storage alloy is accelerated and durability is lowered.

  In addition, in the alkaline storage battery using the conventional hydrogen storage alloy negative electrode, 40 ° C., H / M = for compatibility between output characteristics (advantageous when the hydrogen storage pressure is high) and regenerative characteristics (advantageous when the hydrogen storage pressure is low). A hydrogen storage pressure at 0.5 of 0.020 MPa or more and 0.055 MPa or less is often used.

JP 2008-084649 A JP 2009-176712 A JP 2011-127177 A

  In order to use an alkaline storage battery using a hydrogen storage alloy negative electrode as a power source for a hybrid vehicle (HEV, PHEV), an electric vehicle (EV), etc., it is necessary to use not only output characteristics and regenerative characteristics, but also a large number of batteries. Is required. In recent years, the price of rare earth elements such as Nd used in magnet applications has risen and it is necessary to reduce the amount used, and replacement with relatively inexpensive La is being studied. However, when the addition amount of La in the hydrogen storage alloy is simply increased, the hydrogen storage pressure decreases, so that the output characteristics of the alkaline storage battery using the hydrogen storage alloy negative electrode are significantly reduced.

  In addition, in order to use alkaline storage batteries using a hydrogen storage alloy negative electrode for HEV, PHEV and EV applications, not only high-rate discharge characteristics at low temperatures (for example, discharge characteristics of 5 It or more at −10 ° C.) are required. Therefore, high temperature resistance is also required.

The alkaline storage battery of one embodiment of the present invention is
A hydrogen storage alloy negative electrode mainly composed of a hydrogen storage alloy;
A nickel positive electrode mainly composed of nickel hydroxide;
An alkaline storage battery comprising an electrode group consisting of a separator and an alkaline electrolyte in an outer can,
The hydrogen storage alloy is selected from the general formula (La _x Ln _y ) _{11 z} Mg _z Ni _{tu- Tu} (T: Al, Co, Mn, Zn) in which La is a main rare earth element, and Ln is other than La X> y, 0.09 ≦ z ≦ 0.14, 3.65 ≦ t ≦ 3.80, 0.05 ≦ u ≦ 0.25) A hexagonal (2H) A5B19 crystal structure, a trigonal (3R) A5B19 crystal structure, and an A2B7 crystal structure,
The powder X-ray diffraction intensity peak by Cu-Kα ray of the hexagonal (2H) A5B19 crystal structure is higher than that of the trigonal (3R) A5B19 crystal structure and A2B7 crystal structure. It is supposed to be big.

  According to the alkaline storage battery of the present invention, the conventional hydrogen storage alloy negative electrode is used because the hydrogen storage alloy of the negative electrode contains inexpensive La in a specific amount and includes a specific crystal structure. Compared with alkaline storage batteries, while being inexpensive, the discharge output characteristics are improved, and the high-temperature durability is equal to or higher. The rare earth element Ln other than La in the hydrogen storage alloy preferably includes at least one of Sm, Gd, and Y as a main component.

It is a longitudinal cross-sectional view of the nickel metal hydride storage battery used in various experimental examples. 3 is a powder X-ray diffraction chart of a LaSm hydrogen storage alloy. 2 is a powder X-ray diffraction chart of a LaNd-based hydrogen storage alloy.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with various experimental examples. However, the following various experimental examples are given for the purpose of understanding the technical idea of the present invention, and are not intended to specify the present invention in this embodiment. The present invention can be equally applied to various changes made without departing from the technical idea shown in the claims.

[Preparation of hydrogen storage alloy]
After mixing the metal elements so as to have a predetermined molar ratio, these mixtures are put into a high-frequency induction furnace in an argon gas atmosphere to be melted, poured into a mold and solidified, and the compositions shown in Table 1 below are given. The ingot-state LaSm-based hydrogen storage alloys of Experimental Examples 1 to 5 and the ingot-state LaNd-based hydrogen storage alloys having the compositions shown in Table 2 were prepared. The composition of these hydrogen storage alloy is represented by the general formula _(La x _Ln y) _{1 one z Mg z Ni t-u Al} u (Ln = Sm or Nd).

Subsequently, about each obtained hydrogen storage alloy, melting | fusing point (Tm) was measured using DSC (differential scanning calorimeter). Thereafter, each hydrogen storage alloy is subjected to heat treatment at a predetermined temperature lower than the melting point (Tm) thereof, for example, 1025 ° C. (Experimental Examples 1 to 5) or 1020 ° C. (Experimental Examples 6 to 8) for a predetermined time, for example, 10 hours. went. After that, these hydrogen storage alloy ingots were coarsely crushed and then mechanically pulverized in an inert gas atmosphere, and Experimental Examples 1 to 8 having a particle diameter (D ₅₀ ) at a volume cumulative frequency of 50% of 25 μm. A hydrogen storage alloy powder was prepared.

  Subsequently, the crystal structure of the hydrogen storage alloy powder according to Experimental Examples 1 to 8 was identified by a powder X-ray diffraction method using an X-ray diffraction measurement apparatus using a Cu—Kα tube as an X-ray source. In this case, X-ray diffraction measurement was performed at a scan speed of 1 ° / min, a tube voltage of 40 kV, a tube current of 300 mA, a scan step of 1 °, and a measurement angle of 20 to 50θ / deg. A powder X-ray diffraction chart of the hydrogen storage alloy powders according to Experimental Examples 1 to 5 is shown in FIG. 2, and a powder X-ray diffraction chart of the hydrogen storage alloy powders according to Experimental Examples 6 to 8 is shown in FIG.

  The trigonal (3R) A5B19 crystal structure, the hexagonal (2H) A5B19 crystal structure, and the A2B7 crystal structure are 2θ = 31.4 ° to 31.7 °, 32.1 ° to 32, respectively. It was identified from the peaks of .4 ° and 32.7 ° to 33.0 °. From the charts shown in FIGS. 2 and 3, it was confirmed that any of the hydrogen storage alloys of Experimental Examples 1 to 8 has an A2B7 crystal structure and an A5B19 crystal structure. Further, regarding the peak intensities of the hexagonal system (2H) and the trigonal system (3R) of the A5B19 type crystal structure, relative values (%) when the peak intensity of the A2B7 type crystal structure is set to 100% are shown in Experimental Example 1 The measurement results of 5 are shown in Table 1, and the measurement results of Experimental Examples 6 to 8 are shown in Table 2.

Next, each of the hydrogen-absorbing alloy powders of Experimental Examples 1 to 8 was activated by repeating hydrogen storage and release five times at, for example, 80 ° C., and then the hydrogen storage amount (H / Based on JIS H7201 (1991) “Method for measuring pressure-composition isotherm (PCT curve) of hydrogen storage alloy” with dissociation pressure when M) is 0.5 and 0.7 as hydrogen equilibrium pressure The pressure and its slope were measured. The slope of the hydrogen storage pressure was determined by the following formula.
Inclination = Log (Occlusion pressure (H / M = 0.7) / Occlusion pressure (H / M = 0.5))
/(0.7-0.5)
The measurement results of Experimental Examples 1 to 5 are shown in Table 1, and the measurement results of Experimental Examples 6 to 8 are shown in Table 2, respectively.

  From the results shown in FIG. 2, the LaSm-based A5B19 type crystal structure was mainly hexagonal (2H) in the hydrogen storage alloy of Experimental Example 1, but three-way in the hydrogen storage alloys of Experimental Examples 2-5. It was confirmed that the crystal system (3R) was predominant. Similarly, from the results shown in FIG. 3, the LaNd-based A5B19 type crystal structure was mainly hexagonal (2H) in the hydrogen storage alloy of Experimental Example 6, but the hydrogen storage of Experimental Examples 7 and 8 It was confirmed that the alloy was mainly trigonal (3R).

  Further, from the results shown in Table 1, in Experimental Examples 2 to 5, the equilibrium pressure of the hydrogen storage alloy decreases as the amount of La added in the hydrogen storage alloy increases. It can be seen that the equilibrium pressure of the hydrogen storage alloy is higher than that of Experimental Example 2 despite the largest amount of La added in the storage alloy. Similarly, from the results shown in Table 2, in Experimental Examples 7 and 8, the equilibrium pressure of the hydrogen storage alloy decreases as the amount of La added in the hydrogen storage alloy increases. It can be seen that despite the largest amount of La added in the storage alloy, the equilibrium pressure of the hydrogen storage alloy is almost the same as that of Experimental Example 7. This is because when the hydrogen storage alloy has a hexagonal (2H) A5B19 type crystal structure, the equilibrium pressure of the hydrogen storage alloy increases, and the amount of La added in the hydrogen storage alloy increases. This is considered to indicate that the equilibrium pressure drop is relaxed.

  However, since La has a strong bond strength with hydrogen, it is assumed that irreversible hydrogen that is occluded but not released increases due to an increase in the amount of La added. However, there is no problem in in-vehicle applications because complete discharge is not performed. The hexagonal (2H) A5B19 type crystal structure can be included by specifying the composition of the hydrogen storage alloy and adjusting the manufacturing conditions such as the heat treatment conditions.

  In Experimental Examples 1 to 8, examples using Sm and Nd as Ln were shown. As Ln, at least one selected from rare earth elements other than La and Y can be used, but from the viewpoint of suppressing pulverization of the hydrogen storage alloy, elements such as Nd, Sm, Gd, Pr, and Y are used. desirable. Further, as Ln, since the equilibrium pressure is decreased due to an increase in the amount of La added, rare earth elements such as Sm, Y, and Gd that have a large effect of increasing the equilibrium pressure are desirable. It should be noted that the amount of La added in the hydrogen storage alloy is preferably larger than Ln, that is, x> y in the above general formula of the hydrogen storage alloy composition.

  If the amount of Mg added is too large, pulverization and dissolution of the Mg component accelerate, and if it is too small, the crystal structure becomes unstable (production of AB5-type crystal structure not containing Mg is remarkable) and the hydrogen storage characteristics are not stable ( (Two steps of occlusion curve). In order to stabilize the hydrogen storage characteristics, it is necessary to stably build the A5B19 type crystal structure. Therefore, the total amount of Mg and rare earth elements (La + Ln) (A), and the amount of Ni and additive elements (T) It is necessary to control the stoichiometric ratio (B / A) to the total (B) within a predetermined range. There is no problem even if an A2B7 crystal structure exists, but if the B / A is too small, the AB2 or AB3 crystal structure tends to be mixed, and if it is too much, the AB5 crystal structure tends to be mixed. In the case where AB2, AB3 type crystal structure, and AB5 type crystal structure are mixed, the pulverization accompanying the cycle becomes remarkable.

  In an in-vehicle application, in order to be able to assist (discharge) at any time, a state of charge (SOC) is maintained in a state of charge of 50% or more, and a large output characteristic is desired in such a high SOC state. Similarly, when the SOC decreases with discharge, it is necessary to immediately recover the SOC position by regenerative charging, and a large regenerative output characteristic is also required. From this point of view, it is desirable that the battery voltage is high in the high SOC region and low in the low SOC region. Therefore, the hydrogen storage curve (PCT curve) has a slope at H / M = 0.5 to 0.7. Is preferably 0.7 or more and 3.0 or less, and it is necessary to control B / A within a range consisting of an A5B19 type crystal structure and an A2B7 type crystal structure. Considering the above points, it is preferable that 0.09 ≦ z ≦ 0.14, 3.65 ≦ t ≦ 3.80.

  In Experimental Examples 1-8, although the example which used Al as a T component was shown, Co, Mn, or Zn can be used for others. If the amount of T component added is too small, it will be disadvantageous in terms of the stability of the crystal structure and the amount of hydrogen occlusion, and if it is too large, the effect of dissolution of the T component will be significant, so 0.05 ≦ u ≦ 0.25. It is preferable to do.

[Characteristic measurement of nickel metal hydride storage battery]
Using each of the hydrogen storage alloys of Experimental Examples 1 to 8 prepared as described above, a nickel metal hydride storage battery was produced as shown below, and a high temperature storage test and measurement of output characteristics were performed.

(Production of hydrogen storage alloy negative electrode)
The hydrogen storage alloy slurries were prepared by mixing and kneading each of the hydrogen storage alloy powders of Experimental Examples 1 to 8, the water-soluble binder, the thermoplastic elastomer, and the carbon-based conductive agent. As the water-soluble binder, an aqueous solution of 0.1% by mass of CMC (carboxymethyl cellulose) was used. Styrene butadiene latex (SBR) was used as the thermoplastic elastomer. Ketchen Black was used as the carbon-based conductive agent.

The hydrogen storage alloy slurry produced as described above is applied to a negative electrode conductive core made of a nickel-plated mild steel porous substrate (punching metal) with a predetermined packing density (for example, 5.2 g / After coating and drying so as to be cm ³ ), it was rolled to a predetermined thickness. Then, it cut | disconnected so that it might become a predetermined dimension, and produced the hydrogen storage alloy negative electrode corresponding to each of Experimental Examples 1-8, respectively.

(Preparation of nickel positive electrode)
A porous nickel sintered substrate having a porosity of about 85% is immersed in a mixed aqueous solution of nickel nitrate, cobalt nitrate and zinc 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 and zinc salt were retained. Thereafter, this porous nickel sintered substrate is immersed in a 25% by mass aqueous sodium hydroxide (NaOH) solution to convert nickel salt, cobalt salt and zinc salt into nickel hydroxide, cobalt hydroxide and zinc hydroxide, respectively. I let you. Next, after sufficiently washing with water to remove the alkaline solution, it was dried, and the positive electrode active material mainly composed of nickel hydroxide was filled in 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 active material mainly composed of nickel hydroxide is filled in the pores of the porous sintered substrate so that the filling density becomes 2.5 g / cm ^3. Filled.

  Next, a porous nickel sintered substrate filled with a positive electrode active material mainly composed of nickel hydroxide is immersed in a mixed aqueous solution of nickel nitrate and yttrium nitrate, and the nickel salt and yttrium salt are held on the electrode plate surface, Thereafter, this porous nickel sintered substrate was immersed in a 25% by mass sodium hydroxide (NaOH) aqueous solution to convert the nickel salt and yttrium salt into nickel hydroxide and yttrium hydroxide, respectively. Next, after sufficiently washing with water to remove the alkaline solution, it was dried and cut into predetermined dimensions to produce a nickel positive electrode.

(Preparation of alkaline electrolyte)
The alkaline electrolyte was prepared by adding sodium tungstate to a mixed aqueous solution prepared by adding sodium hydroxide (NaOH) and lithium hydroxide (LiOH) in a predetermined molar ratio to a 30% by mass potassium hydroxide (KOH) aqueous solution. What was added so that it might become 20 mg per 1 g of alkaline electrolyte in conversion of tungsten was used.

(Production of nickel metal hydride storage battery)
Using the hydrogen storage alloy negative electrode and the nickel positive electrode produced as described above, a separator made of nonwoven fabric containing a sulfonated polypropylene fiber is interposed therebetween, and the spiral electrode group is wound in a spiral shape. Was made. This sulfonated polypropylene fiber has an ammonia adsorption ability. In the lower part of the spiral electrode group thus produced, the core exposed part of the hydrogen storage alloy negative electrode is exposed, and the core exposed part of the nickel positive electrode is exposed above it. Next, the negative electrode current collector is welded to the core exposed portion exposed at the lower end surface of the obtained spiral electrode group, and the positive electrode is exposed on the nickel positive electrode core exposed portion exposed at the upper end surface of the spiral electrode group. The current collector was welded to obtain an electrode body.

  The obtained electrode body was housed in a bottomed cylindrical outer can made of nickel-plated iron (the outer surface of the bottom surface becomes the negative electrode external terminal), and then the negative electrode current collector was welded to the inner bottom surface of the outer can . The current collector lead portion extending from the positive electrode current collector served as the positive electrode terminal and was welded to the sealing body constituting the bottom portion of the sealing body having an insulating gasket attached to the outer peripheral portion. In addition, the positive electrode cap is provided in the sealing body, and the pressure valve which consists of the valve body and spring which deform | transform when it becomes predetermined pressure in this positive electrode cap is arrange | positioned.

  Next, after forming an annular groove in the upper outer periphery of the outer can, an alkaline electrolyte is injected, and an insulating gasket mounted on the outer periphery of the sealing body is placed on the annular groove formed in the upper portion of the outer can. I put it. Then, the opening edge of the outer can was crimped, and the alkaline electrolyte was injected into the outer can at 2.5 g / Ah per battery capacity, and nickel hydride storage batteries corresponding to each of Experimental Examples 1 to 8 were produced.

  A specific configuration of the nickel-metal hydride storage battery 10 thus manufactured will be described with reference to FIG. The nickel-metal hydride storage battery 10 has a wound electrode body 14 in which the nickel positive electrode 11 and the hydrogen storage alloy negative electrode 12 manufactured as described above are wound in a state of being insulated from each other via a separator 13. ing. The nickel positive electrode 11 is a positive electrode active material in which nickel hydroxide is a main component and cobalt hydroxide is added in a porous nickel sintered body formed on both surfaces of a positive electrode core 15 made of a nickel-plated steel plate. It has a configuration filled with the substance 16. In the hydrogen storage alloy negative electrode 12, a negative electrode mixture layer 19 having hydrogen storage alloy powder as a negative electrode active material is formed on both surfaces of a negative electrode core 18 made of a nickel-plated mild steel punching metal.

  A negative electrode current collector 20 is resistance-welded to the negative electrode core 18 at the lower part of the wound electrode body 14, and a positive electrode current collector 21 is resistance-welded to the positive electrode core 15 at the upper part of the wound electrode body 14. Yes. The wound electrode body 14 is inserted into a bottomed cylindrical metal outer can 22 in which iron is nickel-plated, and the negative electrode current collector 20 and the bottom of the outer can 22 are spot-welded. ing.

  On the open end side of the outer can 22, a sealing body 23 in which nickel is plated on iron is caulked and fixed with a gasket 24 being electrically insulated from the outer can 22. The positive electrode current collector 21 is welded and electrically connected to the sealing body 23. An opening 25 is provided in the center of the positive electrode current collector 21, and a valve body 26 is disposed in the opening 25 so as to block the opening 25.

  Further, a positive electrode cap 27 is provided on the upper surface of the sealing body 23 so as to cover the periphery of the opening 25 and to be separated from the valve body 26 by a certain distance. The positive electrode cap 27 is appropriately provided with a gas vent hole (not shown). A spring 28 is provided between the inner surface of the positive electrode cap 27 and the valve body 26, and the valve body 26 is pressed by the spring 28 so as to close the opening 25 of the sealing body 23. The valve body 26 has a function as a safety valve for releasing the internal pressure when the internal pressure of the outer can 22 becomes high.

(Activation of NiMH batteries)
Each cylindrical nickel-metal hydride storage battery corresponding to Experimental Examples 1 to 8 manufactured as described above was charged in a thermostat maintained at 25 ° C. until the SOC became 120% with a charging current of 1 It. Then, after being left for 24 hours in a thermostat maintained at 70 ° C., the battery was discharged in a thermostat maintained at 45 ° C. until the battery voltage became 0.3 V with a discharge current of 1 It. The battery was activated by repeating this charge / discharge cycle as one cycle for two cycles.

  Next, for each of the cylindrical nickel-metal hydride storage batteries corresponding to the activated Experimental Examples 1 to 8, in a thermostat maintained at 25 ° C., until the SOC becomes 120% at a constant current of 0.5 It. The battery was charged and allowed to stand for 1 hour, and then discharged at a discharge current of 1 It until the battery voltage reached 0.9V. This charge / discharge cycle was repeated three times.

(High temperature storage test)
In order to investigate the corrosion resistance of the hydrogen storage alloy, the following evaluation was performed. After measuring the battery mass of the cylindrical nickel metal hydride storage battery corresponding to each of Experimental Examples 1 to 8 activated as described above, after charging to 80% of SOC at a charging current of 1 It in a temperature atmosphere of 25 ° C. , And allowed to stand at 80 ° C. for 1 week. Next, the battery was discharged with a discharge current of 1 It in a temperature atmosphere of 25 ° C. until the battery voltage became 0.9V. Such charge leaving was repeated 6 times (Experimental Examples 1 to 5) or 5 times (Experimental Examples 6 to 8).

(Output characteristic evaluation)
The low-temperature output characteristic evaluation of the cylindrical nickel-metal hydride storage battery corresponding to each of Experimental Examples 1 to 8 before and after being left in an 80 ° C. temperature atmosphere was measured as follows. The cylindrical nickel metal hydride storage batteries corresponding to each of Experimental Examples 1 to 8 activated as described above were charged to 50% of SOC at a charging current of 1 It in a temperature atmosphere of 25 ° C., and then the temperature atmosphere of −10 ° C. And rested for 3 hours. Next, the battery was charged for 20 seconds at a predetermined charging rate shown below 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 a predetermined discharge rate shown below in a temperature atmosphere of −10 ° C., and then rested for 30 minutes in a temperature atmosphere of −10 ° C. Such a 20 second charge at a predetermined charge rate in a temperature atmosphere of −10 ° C., a 30 minute pause, a 10 second discharge at a predetermined discharge rate, and a 30 minute pause in a temperature atmosphere of 10 ° C. were repeated. .

  In this case, the predetermined charging rate increases the charging current in the order of 0.8 It−1.7 It−2.5 It−3.31 t−4.21 t, and the predetermined discharging rate is 1.7 It−3.3 It−. The discharge current was increased in the order of 5.0 It-6.7 It-8.3 It, and the battery voltage (V) of each battery when 10 seconds passed at each discharge rate was measured for each discharge rate. Then, the measured battery voltage (V) of each battery at the time point of 10 seconds is two-dimensionally plotted with respect to the discharge current value for each discharge rate to obtain an approximate curve indicating the relationship between the battery voltage and the discharge current value. The discharge current value at 0.9 V in the curve was determined as SOC 50% output characteristics. The measurement results of the LaSm system of Experimental Examples 1 to 5 are shown in the “Initial” column of Table 3 as relative values with the measurement result of Experimental Example 1 being 100, and the LaNd systems of Experimental Examples 6 to 8 are those of Experimental Example 6. The relative value with the measurement result as 100 is shown in the column “Initial” in Table 4.

  Next, the SOC 50% output characteristics were obtained for the cylindrical nickel-metal hydride batteries corresponding to each of Experimental Examples 1 to 8 after being left at high temperature in the same manner as in the above case. The measurement results of the LaSm system in Experimental Examples 1 to 5 are shown in the “After Degradation” column of Table 3 as relative values with the measurement result of Experimental Example 1 being 100, and the LaNd systems in Experimental Examples 6 to 8 are those of Experimental Example 6. The relative value with the measurement result as 100 is shown in the “after degradation” column of Table 4.

  In addition, in the columns of “Initial × After Degradation” in Tables 3 and 4, the “Initial” measurement results and “After Degradation” are taken into account in order to comprehensively consider the “Initial” output characteristics and “After Degradation” output characteristics. The measurement results of the LaSm system of Experimental Examples 1 to 5 are shown in Table 3 as relative values with the measurement result of Experimental Example 1 being 100, and the LaNd systems of Experimental Examples 6 to 8 are Experimental Example 6 Table 4 shows the relative values with the measurement result of 100 as 100.

  As is clear from the results shown in Tables 3 and 4, in the nickel metal hydride storage batteries corresponding to Experimental Examples 1 and 6, the nickel hydrogen storage batteries corresponding to Experimental Examples 2 to 5 to Experimental Examples 7 and 8 are used. In spite of the addition amount of La (cost is low), the deterioration of the initial characteristics is suppressed, and the superiority of the charge / discharge characteristics is maintained even after deterioration (after leaving at high temperature). It was confirmed that the balance of characteristics was excellent. In particular, in the nickel metal hydride storage battery corresponding to Experimental Example 1, it is possible to increase the amount of La added more than that of Example 2, and it is clear that the cost is superior.

DESCRIPTION OF SYMBOLS 10 ... Nickel metal hydride battery 11 ... Nickel positive electrode 12 ... Hydrogen storage alloy negative electrode 13 ... Separator 14 ... Winding electrode body 15 ... Positive electrode core body 16 ... Positive electrode active material 18 ... Negative electrode core body 19 ... Negative electrode mixture layer 20 ... Negative electrode current collection Body 21 ... Positive electrode current collector 22 ... Exterior can 23 ... Sealing body 24 ... Gasket 25 ... Opening 26 ... Valve body 27 ... Positive electrode cap 28 ... Spring

Claims (2)

A hydrogen storage alloy negative electrode mainly composed of a hydrogen storage alloy;
A nickel positive electrode mainly composed of nickel hydroxide;
An alkaline storage battery comprising an electrode group consisting of a separator and an alkaline electrolyte in an outer can,
The hydrogen storage alloy is selected from the general formula (La _x Ln _y ) _{11 z} Mg _z Ni _{tu- Tu} (T: Al, Co, Mn, Zn) in which La is a main rare earth element, and Ln is other than La X> y, 0.09 ≦ z ≦ 0.14, 3.65 ≦ t ≦ 3.80, 0.05 ≦ u ≦ 0.25) A hexagonal (2H) A5B19 crystal structure, a trigonal (3R) A5B19 crystal structure, and an A2B7 crystal structure,
The powder X-ray diffraction intensity peak by Cu-Kα ray of the hexagonal (2H) A5B19 crystal structure is higher than that of the trigonal (3R) A5B19 crystal structure and A2B7 crystal structure. large,
Alkaline storage battery.   The alkaline storage battery according to claim 1, wherein the Ln includes at least one of Sm, Gd, and Y as a main component.

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