JP2009059598A - Alkaline accumulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage alloy electrode in which adhesive strength between a core body and negative electrode active materials (hydrogen storage alloy powders), and adhesive strength between the negative electrode active materials are improved. <P>SOLUTION: This alkaline storage battery is equipped with a spirally wound electrode group in which a separator 13 is interposed between the hydrogen storage alloy electrode 11 wherein the hydrogen storage alloy is made as the negative electrode active material and a nickel electrode 12 wherein nickel hydroxide is made as the main positive electrode active material together with an alkaline electrolytic solution in an armoring can 17. Then, the hydrogen storage alloy electrode 11 contains a non-water soluble polymer and an anion based water-soluble polymer as a binder, and as for the anion based water-soluble polymer, the content existing on the surface part of the hydrogen storage alloy electrode 11 is arranged to be more than that existing in the interior of the hydrogen storage alloy electrode 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an alkaline storage battery suitable for applications requiring high current discharge such as HEV (hybrid vehicle) and PEV (electric vehicle), and in particular, a hydrogen storage alloy electrode and nickel hydroxide using a hydrogen storage alloy as a negative electrode active material. The present invention relates to an alkaline storage battery in which an electrode group wound in a spiral shape with a separator interposed between a nickel electrode having a main positive electrode active material together with an alkaline electrolyte in an outer can.

  In recent years, the use of secondary batteries (storage batteries) has expanded, and has come to be used in a wide range such as mobile phones, notebook computers, electric tools, electric bicycles, hybrid vehicles (HEV), and electric vehicles (PEV). Among these, especially for power supplies for devices that require high output such as electric tools, electric bicycles, hybrid vehicles (HEV), and electric vehicles (PEV), high output far exceeding the conventional range is required. At the same time, higher reliability has been demanded.

  Incidentally, an alkaline storage battery such as a nickel-hydrogen storage battery is used for a power source that requires this type of high output. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-82491) discloses a technique for increasing the output of such an alkaline storage battery. Issue). Here, in the high output method proposed in Patent Document 1, it is proposed to increase the facing area between the positive and negative electrodes constituting the electrode group. In this case, the electrode is made as thin as possible to increase the opposing area of the positive and negative electrodes by winding the electrode group several times.

However, if the thickness of the electrode is reduced and the number of electrode layers in the electrode group after winding is increased, the strength of the electrode is reduced, and cracks and cracks occur during winding. Patent Document 2 (Japanese Patent Laid-Open No. 61-66366) proposes increasing the content of the binder added to the electrode as a technique for improving the strength of the electrode. However, in the technique proposed in Patent Document 2, since the content of the binder is high, the reactivity is lowered and a high output cannot be obtained. Thus, it is difficult to achieve both improvement in electrode strength and high output.
JP 2000-82491 A JP-A 61-66366

  By the way, assuming that the outer diameter and height of the electrode group are constant, in order to increase the opposing area of the positive and negative electrodes, the thickness of the core is reduced to such an extent that the strength of the electrode is not reduced, or It is necessary to reduce the basis weight of the separator. However, based on the viewpoint of the necessity of equalizing the current density in a large current application, it is necessary to secure the thickness of the core body to a certain value or more. Further, from the viewpoint of preventing a short circuit, it is necessary to secure the basis weight of the separator above a certain value. For this reason, in order to increase the opposing area of the positive and negative electrodes in the electrode group, it is inevitably necessary to increase the constituent pressure of the electrode group.

 However, in the step of increasing the constituent pressure of the electrode group, friction occurs between the hydrogen storage alloy powder existing on the surface of the negative electrode and the separator, and the hydrogen storage alloy powder falls off the negative electrode. Here, when the hydrogen storage alloy powder falls off the negative electrode, there arises a problem that the positive and negative electrodes are short-circuited through the dropped hydrogen storage alloy powder. Further, even if the short circuit is not generated, the dropped hydrogen storage alloy powder causes the battery voltage to vary.

  By the way, especially when used for an assembled battery configured by connecting a plurality of alkaline storage batteries such as HEV and PEV, which are required for high output such as power supply, in series, the battery voltage varies depending on the battery. As a result, a difference in battery capacity is caused, resulting in a problem that the lifetime of the assembled battery is further shortened. For this reason, in negative electrodes used in alkaline storage batteries such as power supplies that require high output exceeding the conventional range, not only the adhesion strength between the core and the negative electrode active material (hydrogen storage alloy powder), but also the negative electrode active material It is necessary to improve the adhesion strength.

  The present invention has been made based on the above findings, and provides a hydrogen storage alloy electrode in which the adhesion strength between the core and the negative electrode active material (hydrogen storage alloy powder) and the adhesion strength of the negative electrode active material question are improved. In addition, an object of the present invention is to provide an alkaline storage battery having such a high output characteristic that exceeds the conventional range using such a hydrogen storage alloy electrode.

  In the present invention, a group of electrodes wound in a spiral shape with a separator interposed between a hydrogen storage alloy electrode having a hydrogen storage alloy as a negative electrode active material and a nickel electrode having nickel hydroxide as a main positive electrode active material are subjected to alkaline electrolysis. The present invention relates to an alkaline storage battery provided in an outer can together with a liquid. In order to achieve the above object, the hydrogen storage alloy electrode contains a water-insoluble polymer and an anionic water-soluble polymer as a binder, and the anionic water-soluble polymer is a component of the hydrogen storage alloy electrode. The present invention is characterized in that the content present on the surface portion of the hydrogen storage alloy electrode is made larger than the content present inside.

  Here, when a water-insoluble polymer (for example, SBR) and an anionic water-soluble polymer (for example, CMC) are used as the binder, the water-insoluble polymer is attached to the particle surface of the hydrogen storage alloy powder. Can be interspersed. This makes it possible to form a three-phase interface (solid-liquid-gas interface) on the particle surface of the hydrogen storage alloy powder. However, since the water-insoluble polymer has poor coating properties, the hydrogen storage alloy powder easily falls off due to friction with the separator. Therefore, in the present invention, an anionic water-soluble polymer (for example, CMC) excellent in spreadability and covering property is contained in the surface portion more than in the hydrogen storage alloy electrode. As a result, it is possible not only to suppress the dropping of the hydrogen storage alloy powder, but also to improve the liquid replenishment property inside the hydrogen storage alloy electrode, thereby improving the output characteristics.

  Then, the content of the anionic water-soluble polymer (for example, CMC) in the hydrogen storage alloy electrode with respect to the hydrogen storage alloy powder is X (part by mass), and the anionic water-soluble polymer on the surface of the hydrogen storage alloy electrode When the content of the hydrogen storage alloy powder (for example, CMC) is Y (parts by mass), if Y / X is 3 or more and 13 or less (3 ≦ Y / X ≦ 13), the active material The experimental result that the strength and the strength between the core and the active material can be made compatible was obtained. Further, the content Y of the anionic water-soluble polymer (for example, CMC) in the surface portion of the hydrogen storage alloy electrode at this time is 0.14 parts by mass or more and 0.63 parts by mass or less (0.14 parts by mass ≦ Y ≦ 0.63 parts by mass).

  When Y / X and Y are defined in this way, it is possible to ensure the strength that can withstand the increase in the component pressure of the electrode group without increasing the amount of binder added. As a result, it is possible not only to suppress the variation in battery voltage due to the dropping of the hydrogen storage alloy powder, but also to improve the output characteristics. In this case, the surface portion of the hydrogen storage alloy electrode has a thickness (t1-t2) from the surface of the hydrogen storage alloy electrode, where the thickness of the hydrogen storage alloy electrode is t1, and the thickness of the core of the hydrogen storage alloy electrode is t2. X can be defined as a range up to 0.15.

The hydrogen storage alloy constituting the hydrogen storage alloy electrode as described above preferably has at least an A ₅ B ₁₉ type crystal structure and contains at least a rare earth element, nickel, magnesium, and aluminum. This is because the A ₅ B ₁₉ type structure is a crystal structure in which the conventional AB ₂ type structure and the AB ₅ type structure are stacked with a period of three layers, and the a-axis and c-axis of the crystal lattice are higher than the AB ₅ type structure. short. For this reason, the lattice volume is small, and the content ratio of nickel per unit crystal lattice can be increased. For this reason, it is possible to form a structure with high activity, and in the electrode design of the present invention, it is possible to reduce the charge transfer resistance at the three-phase interface.

A hydrogen storage alloy having a crystal structure of at least an A ₅ B ₁₉ type structure and containing at least a rare earth element, nickel, magnesium, and aluminum is represented by _a general formula Ln _lx Mg _x Ni _yab Al _a M _b , The conditions of 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.1 ≦ a ≦ 0.3, and 0 ≦ b ≦ 0.2 must be satisfied. This is because magnesium is segregated when x> 0.2, and aluminum is segregated when a> 0.3, resulting in a decrease in corrosion resistance. Further, if y <3.5 or y> 3.9, it is difficult to form the A ₅ B ₁₉ type structure.

  Further, in such a hydrogen storage alloy, when the average particle size is smaller than 30 μm, the contact area with the separator increases, and accordingly, the friction coefficient increases and the hydrogen storage alloy powder easily falls off. . For this reason, in order to suppress the dropping of the hydrogen storage alloy powder from the surface of the hydrogen storage alloy electrode, the average particle diameter of the hydrogen storage alloy powder is preferably 30 μm or more, but by using the hydrogen storage alloy electrode of the present invention. It becomes possible to use hydrogen storage alloy powder having an average particle size of 30 μm or less.

In this case, when the content of the anionic water-soluble polymer is increased in the surface portion than in the hydrogen storage alloy electrode, the strength between the active materials is improved as compared with the case where the surface portion and the inside are equal. And, when using a hydrogen storage alloy electrode in which the content of the anionic water-soluble polymer is greater on the surface portion than in the interior of the hydrogen storage alloy electrode, even if the basis weight of the separator is reduced to 35 g / m ² , Experimental results in which the strength between active materials is improved compared to the case of using a hydrogen storage alloy electrode in which the content of an anionic water-soluble polymer is equal between the surface and the interior, and using a separator having a basis weight of 55 g / m ² was gotten. For this reason, by using the hydrogen storage alloy electrode of the present invention, it is possible to reduce the basis weight of the separator, and it is possible to use a separator having a basis weight of 35 to 55 g / m ² .

  In the present invention, since the content of the anionic water-soluble polymer in the surface portion of the hydrogen storage alloy electrode is larger than the content in the hydrogen storage alloy electrode, it is possible to suppress the dropping of the hydrogen storage alloy powder. Is possible. In addition, since it is possible to improve the fluid replenishment inside the hydrogen storage alloy electrode, the output characteristics are improved, and the hydrogen storage alloy electrode with the opposed area design that exceeds the conventional range has high reliability and high output characteristics. It becomes possible to provide the alkaline storage battery which has this.

Next, embodiments of the present invention will be described in detail below with reference to FIG. 1 to FIG. 3. However, the present invention is not limited to these embodiments, and may be appropriately modified and implemented without departing from the scope of the present invention. be able to. 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 strength between the active materials and the strength between the core and the active material with respect to the ratio Y / X of the CMC content in the surface portion relative to the inside of the hydrogen storage alloy electrode. FIG. 3 is a diagram showing the relationship between the active material strength and the basis weight (g / m ² ) of the separator.

1. Hydrogen storage alloy After mixing metal elements such as La, Ce, Pr, Nd, Sm, Mg, Ni, Al, Co, Mn, and Zn so as to have a predetermined molar ratio, these mixtures are mixed with a high frequency in an argon gas atmosphere. After being charged into an induction furnace and melted, the molten metal was quenched to form an alloy ingot to produce hydrogen storage alloys a to e. In this case, a hydrogen storage alloy a having a composition formula represented by Nd _0.9 Mg _0.1 Ni _3.2 Al _0.2 Co _0.1 was used.

Similarly, a hydrogen storage alloy b having a composition formula represented by La _0.2 Pr _0.1 Nd _0.5 Mg _0.2 Ni _3.6 Al _0.3 and a hydrogen storage alloy b having La _0.2 Sm _0.7 Mg _0.1 Ni _3.5 Al _0.1 Zn _0.2 The alloy c is represented by La _0.8 Ce _0.1 Pr _0.05 Nd _0.05 Ni _4.2 Al _0.3 (Co, Mn) _0.5 and the hydrogen storage alloy d is represented by La _0.2 Pr _0.3 Nd _0.3 Mg _0.2 Ni _3.1 Al _0.2 This was designated as hydrogen storage alloy e.

  Subsequently, about each obtained hydrogen storage alloy ae, melting | fusing point (Tm) was measured using DSC (differential scanning calorimeter). Thereafter, a heat treatment was performed for a predetermined time (in this case, 10 hours) at a temperature (Ta = Tm-30 ° C.) lower by 30 ° C. than the melting points (Tm) of these hydrogen storage alloys a to e. And the composition of each hydrogen storage alloy ae after heat processing was analyzed by the high frequency plasma spectroscopy (ICP), and when the result was shown, the result as shown in following Table 1 was obtained.

  Subsequently, the crystal structures of the hydrogen storage alloys a to e were identified by a powder X-ray diffraction method using an X-ray diffraction measuring 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 (2θ) of 20 to 50 °. From the obtained XRD profile, the crystal structure of each of the hydrogen storage alloys a to e was identified using a JCPDS card chart.

Here, in the composition ratio of each crystal structure, the A ₅ B ₁₉ type structure is a Ce ₅ Co ₁₉ type structure and a Pr ₅ Co ₁₉ type structure, and the A ₂ B ₇ type structure is an Nd ₂ Ni ₇ type structure and Ce ₂ Ni structure. ₇ type structure, AB ₅ type structure is LaNi ₅ type structure, and the ratio of intensity of diffraction angle of each structure by JCPDS and the strongest intensity value of 42-44 ° is applied to each obtained XRD profile. When the composition ratio of each structure was calculated, the results shown in Table 1 below were obtained.

As is clear from the results in Table 1 above, in the hydrogen storage alloys a to e represented by the general formula Ln _lx Mg _x Ni _yab Al _a M _b , 0.1 ≦ x ≦ 0.2, 3.5 ≦ Of those that do not satisfy the conditions of y ≦ 3.9, 0.1 ≦ a ≦ 0.3, and 0 ≦ b ≦ 0.2, the hydrogen storage alloy d has an AB ₅ type structure, and the hydrogen storage alloy e is A _2. it can be seen consisting of B ₇ structure and AB ₅ type structure. On the other hand, hydrogen storage alloys a, b, which satisfy the conditions of 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.1 ≦ a ≦ 0.3, and 0 ≦ b ≦ 0.2. It can be seen that c has at least an A ₅ B ₁₉ type structure.

2. Hydrogen storage alloy electrode Next, the hydrogen storage alloy a is used to roughly pulverize the lump of the hydrogen storage alloy a, and then mechanically pulverize it in an inert gas atmosphere until the average particle size becomes 25 μm. Alloy powder was prepared. Then, 0.5 parts by mass of SBR (styrene butadiene latex) as a water-insoluble polymer and CMC (carboxymethylcellulose) as an anionic water-soluble polymer with respect to 100 parts by mass of the obtained hydrogen storage alloy powder. 0.05 part by mass and an appropriate amount of water (or pure water) were added and kneaded to prepare a hydrogen storage alloy slurry.

Thereafter, this hydrogen storage alloy slurry was applied to a core made of nickel-plated punching metal to form a negative electrode mixture layer. After drying, the negative electrode mixture layer is rolled so as to have a packing density of 5.0 g / cm ³ and cut so that the negative electrode surface area (short axis length × long axis length × 2) becomes 760 cm ^2. 11 was produced. Next, CMC is dissolved in an appropriate amount of water (or pure water) and adjusted to have a viscosity of 200 mPa · s, and then the content of CMC (anionic water-soluble polymer) on the surface of the hydrogen storage alloy electrode 11 (hydrogen The surface of the hydrogen storage alloy electrode 11 was applied by roll transfer so that the mass part) relative to 100 parts by mass of the storage alloy powder was a predetermined amount as shown in Table 2, and the hydrogen storage alloy electrodes a1 to a8 were produced. .
In this case, when the thickness of the hydrogen storage alloy electrode 11 is t1, and the thickness of the core made of the punching metal of the hydrogen storage alloy electrode is t2, (t1−t2) × 0. The range of 15 is defined as the surface portion of the hydrogen storage alloy electrode.

Here, the content of CMC (anionic water-soluble polymer) in the surface portion of the hydrogen storage alloy electrode 11 was adjusted to 0.05 (in this case, CMC was not applied to the surface portion). This was used as a hydrogen storage alloy electrode a1. Similarly, the hydrogen storage alloy electrode a2 adjusted to 0.08 parts by mass and the hydrogen storage alloy electrode a3 adjusted to 0.14 parts by mass were 0.24 parts by mass. What was adjusted to become hydrogen storage alloy electrode a4. Moreover, what was adjusted to be 0.33 parts by mass was a hydrogen storage alloy electrode a5, and what was adjusted to be 0.50 parts by mass was a hydrogen storage alloy electrode a6, and was 0.63 parts by mass. What was adjusted to become hydrogen storage alloy electrode a7, and what was adjusted to 0.70 parts by mass was hydrogen storage alloy electrode a8.
And the content of CMC in the surface portion of the hydrogen storage alloy electrode with respect to the content of CMC in the hydrogen storage alloy electrode (mass part with respect to 100 parts by mass of hydrogen storage alloy powder) X (mass part with respect to 100 parts by mass of hydrogen storage alloy powder) ) Y ratio Y / X was obtained as shown in Table 2 below.

3. Strength test of hydrogen storage alloy electrode (1) Strength between active materials Next, using each of the hydrogen storage alloy electrodes a1 to a8 produced as described above, a pressure test (between active materials) serving as an index of electrode plate strength Strength test and core-active material strength test) were performed as follows. That is, in the strength test between active materials, each hydrogen storage alloy electrode a1 to a8 is cut into 100 mm × 50 mm, and a separator having a basis weight of 55 g / m ² is placed thereon, and then a load of 30 g / cm ² is applied. Insert (pull) the separator while applying. Next, the amount of active material adhering to the separator was measured, and the reciprocal of the relative value when the active material adhering amount of a1 on which the CMC was not applied to the electrode surface was set to 100 was used as an index A of the strength between the active materials. That is, as the index A is larger, the strength between the active materials on the electrode surface is improved.

(2) Strength between core and active material On the other hand, in the strength test between core and active material, after each hydrogen storage alloy electrode a1 to a8 was cut into 150 mm × 50 mm and wound around a roll having a radius of 20 mm And fixed with adhesive tape. Thereafter, the roll was rotated for 5 seconds while applying a pressure of 0.5 MPa on them, and the number of times the hydrogen storage alloy powder was peeled off from the core was determined. And the relative value when the frequency | count of peeling of the hydrogen storage alloy electrode a1 in which CMC is not apply | coated to the electrode surface part was set to 100 was set as the parameter | index B of the strength between core bodies-active materials. That is, the smaller the index B, the weaker the strength between the core and the active material.

  Here, based on the results in Table 2 above, the ratio Y / X of the CMC content Y in the surface portion to the CMC content X inside the hydrogen storage alloy electrode is taken as the horizontal axis (X axis), When the strength (index A) and the core-active material strength (index B) are plotted on the vertical axis, the results are as shown in FIG. As can be seen from the results of Table 2 and FIG. 2, the strength between the active materials (index A) increases as Y / X increases. On the other hand, the strength between the core and the active material (index B) is improved when Y / X is 3.0 or more. However, when it exceeds 13, the CMC is not applied to the electrode surface. It turns out that it falls rather than the hydrogen storage alloy electrode a1 which is.

  Here, in the strength test between the core and the active material, the hydrogen storage alloy powder at the time of the adhesive tape peels, whereas when Y / X> 13, the hydrogen storage alloy powder other than at the time of the adhesive tape is Peeling was confirmed. This is presumably because the surface of the hydrogen storage alloy electrode was hardened by CMC (anionic water-soluble polymer) and surface cracking occurred during winding.

  From these results, in order to achieve both the strength between the active materials and the strength between the core and the active material, the ratio Y / X of the CMC content in the surface portion to the inside of the hydrogen storage alloy electrode is 3 or more and 13 or less (3 It can be said that it is desirable to satisfy ≦ Y / X ≦ 13). In this case, the content Y of CMC in the surface portion of the hydrogen storage alloy electrode is 0.14 parts by mass or more and 0.63 parts by mass or less (0.14 parts by mass ≦ Y ≦ 0.63 parts by mass). It should be noted that both the effect of improving the strength between the active materials and the effect of improving the strength between the core and the active material appear as the winding pressure increases, that is, as the opposing area between the electrodes increases. become.

4). Nickel-hydrogen storage battery Next, the above-mentioned hydrogen storage alloys b to e are used to mechanically pulverize these hydrogen storage alloys be to e until the average particle size becomes 25 μm in an inert gas atmosphere. To obtain a hydrogen storage alloy powder. Next, in the same manner as described above, 0.5 parts by mass of SBR as a water-insoluble polymer and 0.05 parts by mass of CMC as an anionic water-soluble polymer are obtained with respect to 100 parts by mass of the obtained hydrogen storage alloy powder. And a suitable amount of water (or pure water) were added and kneaded to prepare a hydrogen storage alloy slurry.

  Next, after each hydrogen storage alloy electrode was produced using the obtained hydrogen storage alloy slurry, the surface of the hydrogen storage alloy electrode was transferred by roll transfer so that the CMC content of the surface portion was 0.63 parts by mass. It applied and produced hydrogen storage alloy electrode 11 (b7, c7, d7, e7). Here, the hydrogen storage alloy electrode b7 is the one using the hydrogen storage alloy b, the hydrogen storage alloy electrode c7 is the one using the hydrogen storage alloy c, and the hydrogen storage alloy electrode d7 is the one using the hydrogen storage alloy d. A hydrogen storage alloy electrode e7 was prepared using the hydrogen storage alloy e.

Next, the hydrogen storage alloy electrode 11 (a1, a3, a4, a7, b7, c7, d7, e7) produced as described above and a known nickel electrode 12 were used, and the basis weight was 55 g. A spiral electrode group was produced by winding in a spiral with a separator 13 made of polypropylene nonwoven fabric of / cm ² interposed. The core exposed portion 11c of the hydrogen storage alloy electrode 11 is exposed at the lower part of the spiral electrode group thus produced, and the core exposed part 12c of the nickel 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 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 (in which the outer surface of the bottom surface becomes a negative electrode external terminal) 17 in which nickel is plated on iron, the negative electrode current collector 14 is attached to the outer can 17. Welded 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 an annular groove portion 17 a on the upper outer peripheral portion of the outer can 17, an electrolytic solution was injected, and the outer peripheral portion of the sealing body 18 was mounted on the annular groove portion 17 a formed on the upper portion of the outer can 17. An insulating gasket 19 is placed. Then, the nickel-hydrogen storage battery 10 (A1, A3, A4, A7, B7, C7, D7, E7) is produced by caulking the opening edge 17b of the outer can 17. In this case, an alkaline electrolyte composed of a 30% by mass potassium hydroxide (KOH) aqueous solution was poured into the outer can 17 so as to be 2.5 g (2.5 g / Ah) per battery capacity (Ah).

  Here, a battery using the hydrogen storage alloy electrode a1 is referred to as a battery A1, a battery using the hydrogen storage alloy electrode a3 is referred to as a battery A3, a battery using the hydrogen storage alloy electrode a4 is referred to as a battery A4, and a hydrogen storage alloy electrode a7. A battery A7 was used. A battery using hydrogen storage alloy electrode b7 is referred to as battery B7, a battery using hydrogen storage alloy electrode c7 is referred to as battery C7, a battery using hydrogen storage alloy electrode d7 is referred to as battery D7, and a hydrogen storage alloy electrode e7 is used. The battery used was designated as battery E7. Each of these batteries A1, A3, A4, A7, B7, C7, D7, E7 had a nominal capacity of 6 Ah and a D size (a diameter of 32 mm and a height of 60 mm).

  In each of these batteries A1, A3, A4, A7, B7, C7, D7, E7, the battery was charged to 120% of SOC (State Of Charge) with a charging current of 1 It at 25 ° C. and rested for 1 hour. Thereafter, it was left (ripened) at 70 ° C. for 24 hours. Subsequently, the battery was discharged at 45 ° C. with a discharge current of 1 It until the battery voltage became 0.3V. Subsequently, such charging, resting, aging, and discharging were repeated for two cycles to activate each of the batteries A1, A3, A4, A7, B7, C7, D7, and E7.

5). Next, in each of the batteries A1, A3, A4, A7, B7, C7, D7, and E7 activated as described above, the output characteristics (−10 ° C. assist output and −30 ° C. assist output) are as follows. ) Was measured. That is, at -10 ° C. assist output, the battery was charged to SOC 50% with a charging current of 1 It at 25 ° C. and rested for 1 hour. Then, after charging for 20 seconds at the following arbitrary charging rate in a temperature environment of −10 ° C., resting for 30 minutes, and then discharging for 10 seconds at the following arbitrary discharging rate, 25 Rested at 30 ° C. for 30 minutes. Such charge at −10 ° C., pause, discharge, and pause at 25 ° C. were repeated.

  In this case, the arbitrary charging rate is 0.8 It → 1.7 It → 2.5 It → 3.3 It → 4.2 It and the charging current is increased, and the arbitrary discharging rate is 1.7 It → 3.3 It → 5.0 It. The discharge current was increased from 6.7 It to 8.3 It, and each battery voltage at the time when 10 seconds elapsed at each rate was measured. Here, when the 0.9 V current on the approximate line of the discharge VI plot was obtained as the -10 ° C. assist output as an indicator of the discharge characteristics, the results shown in Table 3 below were obtained.

  On the other hand, at an assist output of −30 ° C., the battery was charged to SOC 50% with a charging current of 1 It at 25 ° C. and rested for 1 hour. Then, after charging for 20 seconds at the following arbitrary charging rate in a temperature environment of −30 ° C., resting for 30 minutes, and discharging for 10 seconds at the following arbitrary discharging rate, 25 Rested at 30 ° C. for 30 minutes. Such charge at −30 ° C., pause, discharge, and pause at 25 ° C. were repeated.

  In this case, the arbitrary charging rate is 0.3 It → 0.7 It → 1.0 It → 1.3 It → 1.7 It and the charging current is increased, and the arbitrary discharging rate is 0.7 It → 1.3 It → 2.0 It. → 2.7 It → 3.3 It was increased by increasing discharge current, and each battery voltage was measured at each rate when 10 seconds had elapsed. Here, when the 0.9 V current on the approximate line of the discharge VI plot was determined as the -30 ° C. assist output as an indicator of the discharge characteristics, the results shown in Table 3 below were obtained. Note that the −10 ° C. assist output and the −30 ° C. assist output in Table 3 are expressed as relative values when the result of the battery C1 is 100.

  As is clear from the results of the batteries A1, A3, A4, and A7 in Table 3 above, it can be seen that the discharge characteristics (output characteristics; assist output) improve as Y / X increases and as the temperature decreases. . This is because the content of CMC (anionic water-soluble polymer), which is excellent in spreading and covering properties, is increased on the surface than in the interior of the hydrogen-absorbing alloy electrode, so that the occlusion of the hydrogen-absorbing alloy powder can be suppressed. In addition, the fluid replenishment inside the electrode is improved. Thereby, it is considered that the charge transfer resistance at the three-phase interface is reduced, and the discharge characteristics (output characteristics; assist output) in the low temperature region where the charge transfer resistance is dominant are improved.

Here, in Table 3 above, discharge at low temperature of the batteries A7, B7, C7, D7, E7 provided with hydrogen storage alloy electrodes adjusted so that the content of CMC in the surface portion was 0.63 parts by mass Compare characteristics (output characteristics; assist output). In this case, it can be seen that the batteries A7, B7, C7 have excellent discharge characteristics (output characteristics; assist output). On the other hand, it can be seen that the batteries D7 and E7 have poor discharge characteristics (output characteristics; assist output). In the batteries A7, B7, and C7, when expressed as Ln _lx Mg _x Ni _yab Al _a M _b , 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.8. Hydrogen storage alloy a (Nd _0.9 Mg _0.1 Ni _3.2 Al _0.2 Co _0.1 ), hydrogen storage alloy b (La _0.2 Pr _0.1 Nd _0.5 Mg _0.2 Ni) satisfying the conditions of 1 ≦ a ≦ 0.3 and 0 ≦ b ≦ 0.2 _3.6 Al _0.3 ) and hydrogen storage alloy c (La _0.2 Sm _0.7 Mg _0.1 Ni _3.5 Al _0.1 Zn _0.2 ) are used.
These hydrogen storage alloys a, b, and c have at least an A ₅ B ₁₉ type structure. The A ₅ B ₁₉ type structure can increase the content ratio of nickel per unit crystal lattice, resulting in a structure with high activity. For this reason, it is considered that the discharge characteristics (output characteristics; assist output) have been improved.

On the other hand, in the battery D7 are using a hydrogen storage alloy d of AB ₅ type structure _{(La 0.8 Ce 0.1 Pr 0.05 Nd} 0.05 Ni 4.2 Al 0.3 (Co, Mn) 0.5), and A ₂ B ₇ structure in cell E7 A hydrogen storage alloy e (La _0.2 Pr _0.3 Nd _0.3 Mg _0.2 Ni _3.1 Al _0.2 ) having an AB ₅ type structure is used. When these alloys d and e are expressed as Ln _lx Mg _x Ni _yab Al _a M _b , 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.1 ≦ a ≦ Since the conditions of 0.3 and 0 ≦ b ≦ 0.2 are not satisfied, it is considered that the discharge characteristics (output characteristics; assist output) have deteriorated.

From the above, in the hydrogen storage alloy general formula is expressed as _{Ln lx Mg x Ni yab Al a} M b, at least A ₅ B ₁₉ type structure has a hydrogen storage alloy a, b, to use c Is desirable. Here, when x> 0.2, magnesium segregates, and when a> 0.3, aluminum segregates, resulting in a decrease in corrosion resistance. Further, if y <3.5 or y> 3.9, it is difficult to form the A ₅ B ₁₉ type structure. For this reason, the conditions of 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.1 ≦ a ≦ 0.3, and 0 ≦ b ≦ 0.2 must be satisfied.

6). Next, the relationship between the separator basis weight (g / m ² ) and the strength between the active materials was examined. Accordingly, the hydrogen storage alloy electrodes a1 and a3 produced as described above were used, respectively, and a separator with a basis weight of 51 g / m ² was combined with this to obtain the index A of the strength between the active materials in the same manner as described above. Similarly, the index A of strength between active materials is obtained by combining separators with a basis weight of 45 g / m ² , and the index A of strength between active materials is obtained by combining separators with a basis weight of 35 g / m ^2. Results as shown in 4 were obtained. Table 4 also shows the results when using the separator having a basis weight of 55 g / m ² shown above. Then, when the basis weight of the separator is plotted on the horizontal axis and the index A of the strength between the active materials is plotted on the vertical axis, the result is shown in FIG.

As is apparent from the results of Table 4 and FIG. 3, when the electrode a1 in which CMC (anionic water-soluble polymer) is not applied to the surface of the hydrogen storage alloy electrode 11 is used, the basis weight of the separator is reduced. It can be seen that the strength between the active materials decreases. On the other hand, when the electrode a3 in which CMC (anionic water-soluble polymer) is applied to the surface of the hydrogen storage alloy electrode 11 is used, the CMC (anionic water-soluble polymer) is obtained even when the basis weight of the separator is reduced to 35 g / m ^2. It can be seen that the strength between the active materials is improved as compared with the case of using the electrode a1 that was not applied to the surface. From this, it can be said that the basis weight of the separator can be reduced to 35 g / m ² by using an electrode obtained by applying CMC (anionic water-soluble polymer) to the surface of the hydrogen storage alloy electrode 11. .

  In the above-described embodiment, an example in which CMC (carboxymethylcellulose) is used as an anionic water-soluble polymer serving as a water-soluble binder has been described. However, the present invention is not limited to CMC obtained using cellulose as a raw material. For example, anionic water-soluble polymers such as polycarboxylic acid and polyacrylic acid copolymers and ammonium salts thereof, copolymers of vinyl monomers and acrylamide hydrophilic monomers are used. However, the same effect can be obtained.

  In addition to the above-mentioned SBR (styrene-butadiene-latex), water-insoluble polymers include hydrogen such as acrylic ester-methacrylic ester copolymer, NBR (acrylonitrile-butadiene-latex), acrylate-butadiene-latex, etc. You may make it select and use from the copolymer containing 2 or more types selected from the acrylic acid ester which can hold | maintain a storage alloy powder, a methacrylic acid ester, an aromatic olefin, a conjugated diene, and an olefin. In this case, it is desirable to use it in the state of an emulsion or latex that can be easily uniformly dispersed when the hydrogen storage alloy slurry is produced.

  As described above, in the alkaline storage battery configured according to the present invention, it is possible to prevent the hydrogen storage alloy powder from falling off the hydrogen storage alloy electrode. Thereby, it becomes possible to manufacture without causing non-uniformity in the characteristics (battery voltage, charge / discharge capacity, etc.) of each alkaline storage battery. For this reason, when an assembled battery (for example, an assembled battery in which five or more batteries are combined in series) is configured using these single cells, the effect can be exhibited particularly effectively.

It is sectional drawing which shows the alkaline storage battery of this invention typically. It is a figure which shows the relationship between the strength between active materials with respect to ratio Y / X of the content of CMC of the surface part with respect to the inside of a hydrogen storage alloy electrode, and the strength between core bodies-active materials. It is a figure which shows the relationship of the strength between active materials with respect to the fabric weight (g / m < ² >) of a separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Hydrogen storage alloy electrode, 11c ... Core body exposed part, 12 ... Nickel electrode, 12c ... Core body exposed part, 13 ... Separator, 14 ... Negative electrode collector, 15 ... Positive electrode collector, 16 ... Positive electrode lead, DESCRIPTION OF SYMBOLS 17 ... Exterior can, 17a ... Annular groove, 17b ... Opening edge, 18 ... Sealing body, 18a ... Positive electrode cap, 18b ... Positive electrode cap, 18b ... Valve plate, 18c ... Spring, 19 ... Insulating gasket

Claims (7)

An electrode group wound with a separator between a hydrogen storage alloy electrode using a hydrogen storage alloy as a negative electrode active material and a nickel electrode using nickel hydroxide as a main positive electrode active material together with an alkaline electrolyte An alkaline storage battery provided in a can,
The hydrogen storage alloy electrode contains a water-insoluble polymer and an anionic water-soluble polymer as a binder,
2. The alkaline storage battery according to claim 1, wherein the content of the anionic water-soluble polymer in the surface portion of the hydrogen storage alloy electrode is larger than the content in the hydrogen storage alloy electrode. The content of the anionic water-soluble polymer present inside the hydrogen storage alloy electrode is X parts by mass with respect to 100 parts by mass of the hydrogen storage alloy powder,
When the content of the anionic water-soluble polymer present on the surface portion of the hydrogen storage alloy electrode is Y parts by mass with respect to 100 parts by mass of the hydrogen storage alloy powder,
2. The alkaline storage battery according to claim 1, wherein the alkaline storage battery has a relationship of 3 ≦ Y / X ≦ 13 and a relationship of 0.14 parts by mass ≦ Y ≦ 0.63 parts by mass.   When the thickness of the hydrogen storage alloy electrode is t1, and the thickness of the core of the hydrogen storage alloy electrode is t2, the surface portion of the hydrogen storage alloy electrode is (t1-t2) × from the surface of the hydrogen storage alloy electrode. The alkaline storage battery according to claim 1 or 2, wherein the alkaline storage battery is in a range of up to 0.15. 4. The hydrogen storage alloy according to claim 1, wherein the hydrogen storage alloy contains at least a rare earth element, nickel, magnesium, and aluminum, and has a crystal structure of at least an A ₅ B ₁₉ type structure. ₅ . Alkaline storage battery. Select the hydrogen storage alloy is represented by the general formula is in _{Ln lx Mg x Ni yab Al a} M b ( wherein, Ln is at least one element selected from rare earth elements including Y, M is Co, Mn, and Zn At least one element, 0.1 ≦ x ≦ 0.2, 3.5 ≦ y ≦ 3.9, 0.1 ≦ a ≦ 0.3, 0 ≦ b ≦ 0.2) The alkaline storage battery according to any one of claims 1 to 4, wherein the alkaline storage battery is provided.   The alkaline storage battery according to any one of claims 1 to 5, wherein the hydrogen storage alloy has an average particle size of 30 µm or less. Alkaline storage battery according to any one of claims 1 to 6 wherein the separator is characterized in that a weight per unit area is 35~55g / m ^2.

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