JP2008117579A - Hydrogen absorbing alloy negative electrode for alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen absorbing alloy negative electrode for an alkaline battery reducing the used amount of nickel and enhancing cycle characteristics; and to provide the alkaline battery having the negative electrode. <P>SOLUTION: The hydrogen absorbing alloy negative electrode has a current collector of a nickel porous body formed by applying nickel plating on a nonwoven fabric of alkali resistant fibers, the nickel content of the current collector is 20-70 g/cm<SP>2</SP>. By using the nonwoven fabric in the current collector and making the filled hydrogen absorbing alloy present in the skeletons of the current collector, coming off of the alloy caused by finely dividing and expansion of the negative electrode can be suppressed. The nickel content in the current collector is low, the filling density of the hydrogen absorbing alloy is high, and the weight of the negative electrode can be made light. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a hydrogen storage alloy negative electrode for an alkaline battery and an alkaline battery. In particular, the present invention relates to a hydrogen storage alloy negative electrode for an alkaline battery and an alkaline battery having excellent cycle characteristics (lifetime).

  Conventionally, primary batteries or secondary batteries have been used as power sources for portable, mobile and industrial equipment. As the latter secondary battery, lead acid batteries, alkaline batteries, and lithium ion secondary batteries are widely used. Among them, the alkaline battery has characteristics such as high reliability, long life, low cost, and further reduction in size and weight compared to the lithium ion secondary battery. A typical alkaline battery is a nickel-hydrogen battery.

  Nickel-hydrogen batteries use a nickel electrode with a positive electrode active material nickel hydroxide filled in a current collector such as a nickel powder sintered body or foamed nickel on the positive electrode, and hydrogen that can absorb and release hydrogen in the negative electrode. An occlusion alloy is used. Many alloys have been researched and developed so far as hydrogen storage alloys for nickel metal hydride batteries. Currently, multi-component alloys based on the AB5 type MmNi5 system are the mainstream.

  The hydrogen storage alloy negative electrode is produced, for example, by coating or filling a current collector with a hydrogen storage alloy. As a current collector used for such a hydrogen storage alloy negative electrode, a two-dimensional punching metal and a three-dimensional foamed nickel have been proposed.

  For example, Patent Documents 1 and 2 disclose a hydrogen storage alloy negative electrode using a punching metal as a current collector. The punching metal can be manufactured by applying nickel plating to a plate containing iron as a main component, and the cost can be reduced.

In addition, for example, Patent Documents 3 and 4 disclose hydrogen storage alloy negative electrodes using foamed nickel as a current collector. Foamed nickel is generally produced by subjecting a foamed sheet made of urethane resin to nickel plating, burning away the urethane resin, and annealing the remaining network nickel in a reducing atmosphere. Foamed nickel has a large porosity (ratio of voids to volume) and can increase the packing density of the hydrogen storage alloy. Also, the basis weight by weight of the nickel plating for the urethane resin in the production of foamed nickel is generally ^{350g / m 2 ~600g / m 2} .

Furthermore, for example, Patent Document 5 discloses a current collector in which a nickel plating film is formed on a fiber surface by applying nickel plating to a nonwoven fabric. Further, in the examples, a positive electrode using this current collector is disclosed, and the nickel plating amount of the current collector is 115 g / m ² .

JP 2002-319395 A JP 2002-343366 A Japanese Patent Laid-Open No. 11-3705 JP 2003-151540 A JP 2005-347177 A

  However, when a punching metal is used for the current collector of an alkaline battery, it is necessary to apply a process for improving the electrolytic resistance to the iron plate, resulting in higher costs than a simple iron plate. Punching metal has a porous structure to improve the binding properties of the hydrogen storage alloy, but when used as a negative electrode current collector, the existing ratio of the current collector to the entire negative electrode is 10 to 20% by mass. Therefore, it is difficult to increase the packing density of the hydrogen storage alloy. For example, it is conceivable to reduce the thickness of the iron plate in order to improve the filling density of the hydrogen storage alloy. However, since it is a special process, it is difficult to use such an iron plate from the viewpoint of cost.

  Further, the hydrogen storage alloy of the negative electrode is repeatedly pulverized and released in the charge / discharge process, whereby the alloy is pulverized and volume expansion occurs. For this reason, when a punching metal having a two-dimensional structure is used as a current collector, the hydrogen storage alloy is likely to fall off or peel off from the current collector. In addition, due to the pulverization of the hydrogen storage alloy, the absorption of the electrolytic solution by the negative electrode becomes remarkable, and the electrolytic solution in the separator is depleted, so that the internal resistance and the cycle characteristics are liable to occur.

  On the other hand, when foamed nickel is used for the current collector, the hydrogen storage alloy is surrounded by a three-dimensional structure skeleton, and the alloy can be prevented from being pulverized to expand its volume. Can be suppressed to some extent. However, foamed nickel has a complicated manufacturing process and a large amount of nickel to be used, so that the manufacturing cost is high.

  Furthermore, when a non-woven fabric is used for the current collector, the swelling of the negative electrode can be suppressed by the three-dimensional structure as in the case of the foamed nickel, but it is required to use less nickel. Yes.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a hydrogen storage alloy negative electrode for an alkaline battery that is excellent in charge and discharge cycle characteristics while reducing the amount of nickel used. . Another object of the present invention is to provide an alkaline battery provided with the hydrogen storage alloy negative electrode for alkaline batteries.

  The present inventors pay attention to the conductivity of the hydrogen storage alloy, and even if the nickel content is reduced for weight reduction and cost reduction, the hydrogen storage alloy is filled in the skeleton of the current collector using the nonwoven fabric. Thus, the inventors have found that the decrease in the current collecting performance of the negative electrode can be suppressed, and have completed the present invention.

The hydrogen storage alloy negative electrode of the present invention is formed by filling a current collector with a hydrogen storage alloy. The hydrogen storage alloy negative electrode of the present invention is a three-dimensional nickel porous body in which the current collector is nickel-plated on a nonwoven fabric made of alkali-resistant fibers, and the nickel content of the current collector is 20 g / m ² or more and 70 g / m m ² or less.

  A non-woven fabric nickel-plated current collector is a porous body having a three-dimensional structure skeleton, and by having most or all of the filled hydrogen storage alloy present in the skeleton, the current collector performance is excellent. Can be prevented from falling off the current collector due to the pulverization of the powder. Moreover, the volume expansion of the alloy can be suppressed, and the swelling of the negative electrode can be suppressed. Here, the state in which most of the filled hydrogen storage alloy is present in the framework means that the majority of the filled hydrogen storage alloy is present in the framework and the remainder is the framework (current collector). The state attached to the surface. When the current collector is filled with a hydrogen storage alloy paste, a very small amount of paste will adhere to the surface of the current collector. If no operation such as wiping off the paste attached to the surface is applied, the paste attached to the surface will be lost. It is not possible. However, such an operation does not necessarily need to be adopted, and the filled hydrogen storage alloy does not need to be completely present in the framework. In other words, it is also possible to have a state in which most of the total amount of the hydrogen storage alloy exists in the skeleton and the remaining extremely small amount of the hydrogen storage alloy adheres to the current collector surface. The amount of the hydrogen storage alloy present in the skeleton is preferably 90% by mass or more of the total amount, more preferably 94% by mass or more, still more preferably 96% by mass or more, and even more preferably 98% by mass. % Or more.

Furthermore, the amount of nickel used can be reduced by setting the amount of nickel in the current collector to 20 g / m ² or more and 70 g / m ² or less. In addition, the pore diameter of the current collector does not become too small, and the current collector has an appropriate porosity, so that the filling density of the hydrogen storage alloy can be increased and the weight of the negative electrode can be reduced.

  The porosity of the nonwoven fabric is preferably 85% or more and 97% or less. More preferably, it is 90% or more and 96% or less.

  By setting the porosity of the nonwoven fabric within such a range, the amount of the hydrogen storage alloy that can be filled in the current collector is increased, and the filling density of the hydrogen storage alloy can be increased.

  The non-woven fabric is preferably heat-treated after entanglement treatment between the fibers.

  By performing the entanglement treatment between the fibers, the number of crossing points between the fibers increases, and by further heat treatment, the fibers are fused at the crossing points, and the obtained nonwoven fabric has high strength and a three-dimensional structure. The skeleton of can be kept strong. By using such a non-woven fabric for the current collector, the hydrogen storage alloy is less likely to fall off the current collector, and the fibers are firmly bonded at the intersections between the fibers, so that the current collector is less likely to expand. The volume expansion of the alloy can be suppressed to further suppress the swelling of the negative electrode.

  Polyolefin fibers and polyamide fibers can be used as the alkali-resistant fibers constituting the nonwoven fabric. Among these, polyolefin fibers can be suitably used. The polyolefin fiber preferably contains one selected from the group consisting of polyethylene, polypropylene, a mixture thereof, and a copolymer thereof. Moreover, the fiber which comprises a nonwoven fabric is good also as what consists of 1 type selected from the same group as a main component, or only 1 type. Specific examples of the fibers include polyethylene fibers, polypropylene fibers, mixed fibers of polyethylene and polypropylene, and coated fibers in which the center is made of polypropylene and the surface thereof is coated with polyethylene.

  When such a fiber exists in the hydrogen storage alloy negative electrode (current collector), sufficient strength can be imparted to the negative electrode. For example, the degree of cracking that occurs in the negative electrode during battery fabrication can be reduced.

  The nickel plating is preferably applied to the nonwoven fabric using an electrolytic plating method after imparting conductivity to the nonwoven fabric using at least one of a sputtering method and an electroless plating method.

  After imparting electrical conductivity to the nonwoven fabric surface, more specifically to the fiber surface constituting the nonwoven fabric, the nonwoven fabric is nickel-plated using an electrolytic plating method to form a uniform nickel layer on the fiber surface in a short time. be able to.

  The hydrogen storage alloy may contain a conductive agent, and the content is preferably 5% by mass or less.

  By containing a conductive agent in the hydrogen storage alloy, the conductivity of the negative electrode can be increased. Since the filling density of the hydrogen storage alloy decreases as the content of the conductive agent increases, the content of the conductive agent is preferably 5% by mass or less. For example, carbon black or nickel powder can be suitably used as the conductive agent.

  The hydrogen storage alloy may contain a binder, and the content thereof is preferably 3% by mass or less.

  Hydrogen storage alloy is processed into powder and filled and pressed into the skeleton to bind the powders together, but it can be integrated, but by containing a binder, the binding property is improved, Dropping from the current collector can be further prevented. The binder hinders the conductivity of the negative electrode, and when the binder content increases, the filling density of the hydrogen storage alloy decreases. Therefore, the binder content is preferably 3% by mass or less. As the binder, for example, SBR (styrene butadiene rubber) or fluororesin can be suitably used.

  The hydrogen storage alloy to be filled in the current collector is a paste obtained by adding a thickener aqueous solution to the hydrogen storage alloy powder, and the hydrogen storage alloy negative electrode may be formed by pressurizing the current collector after filling the current collector. preferable.

  By filling the current collector with the paste of the hydrogen storage alloy to which the thickener is added, and then pressurizing, the bonding property between the hydrogen storage alloy powders can be further enhanced, and the packing density of the hydrogen storage alloy can be increased. For example, CMC (carboxymethyl cellulose) can be suitably used as the thickener. Moreover, it is preferable to pressurize a roll using a roller press, for example.

  The thickness of the nonwoven fabric before pressurization is preferably 1.2 times or more and 2.0 times or less of the thickness of the hydrogen storage alloy negative electrode obtained by pressurization. More preferably, it is 1.4 times or more and 1.8 times or less.

  When the thickness of the non-woven fabric is more than 2.0 times the thickness of the negative electrode, when the hydrogen storage alloy is filled, holes that are not filled with the hydrogen storage alloy remain, and it is difficult to uniformly fill the skeleton with the hydrogen storage alloy. Become. Further, when the thickness of the nonwoven fabric is less than 1.2 times the thickness of the negative electrode, the number of holes formed by the skeleton for holding the hydrogen storage alloy is reduced, and a sufficient amount of the hydrogen storage alloy is contained in the skeleton. It cannot be present, and the amount of alloy applied to the current collector surface increases.

  The hydrogen storage alloy negative electrode of this invention can be utilized suitably for an alkaline battery.

  In the case of a nickel-hydrogen battery, for example, a separator made of a hydrophilic non-woven polyolefin and a nickel electrode mainly composed of nickel hydroxide are prepared, and an electrode group is prepared by sandwiching the separator between the negative electrode and the nickel electrode. To do. In the case of a cylindrical battery, a wound and wound electrode group is inserted into a battery case, and then an electrolytic solution is injected, and a nickel electrode terminal is welded to the lid portion for sealing. In the case of a prismatic battery, a single-terminal nickel electrode is usually used, and an electrode group having a laminated structure in which a negative electrode and a nickel electrode are stacked with a separator interposed therebetween is inserted into the battery case.

  Moreover, it is preferable that an alkaline battery makes a negative electrode and a battery case contact, and a battery case also serves as a negative electrode terminal.

  According to this configuration, it is not necessary to take out the terminal of the negative electrode, and the productivity is excellent. In a cylindrical battery using a wound electrode group, the negative electrode is wound so that the negative electrode is on the outer peripheral side, and the outer peripheral portion of the negative electrode is brought into contact with the battery case. In addition, in the case of a rectangular battery using a stacked electrode group, when a metal sheath or a laminate sheath is used for a battery case, the positive electrode and the negative electrode are stacked while being shifted up and down, and the outer edge of the negative electrode protruding from the electrode group is electrically connected. Contact the tank.

  The hydrogen storage alloy negative electrode of the present invention will be described in more detail.

  The nonwoven fabric used in the present invention can be produced using a known method such as a dry method or a wet method. The nonwoven fabric obtained by the wet method has less variation in basis weight and thickness than the nonwoven fabric obtained by the dry method. Moreover, you may raise the intensity | strength of a nonwoven fabric by performing the entanglement process, such as a hydroentanglement process and a needle punch process, or performing the heat processing which fuse | melts fibers.

What is necessary is just to determine the fabric weight of a nonwoven fabric suitably. Moreover, the amount of hydrogen storage alloy that can be filled in the current collector can be increased by increasing the porosity of the nonwoven fabric by increasing the bulk of the nonwoven fabric. However, when the fabric weight of the nonwoven fabric is suppressed and the porosity is increased by increasing the bulkiness, the strength of the nonwoven fabric is lowered. Therefore, the weight per unit area of the nonwoven fabric is preferably 45 g / m ² or more and 80 g / m ² or less.

  The thickness of the hydrogen storage alloy negative electrode used in a general alkaline battery is about 300 μm to 400 μm for the high output type, and about 450 μm to 550 μm for the high capacity type. Therefore, the thickness of the nonwoven fabric may be appropriately determined in consideration of the thickness of the negative electrode to be manufactured. In addition, when the pressure is applied after filling the current collector with the hydrogen storage alloy, the thickness of the nonwoven fabric is preferably 1.2 times or more and 2.0 times or less the thickness of the hydrogen storage alloy negative electrode obtained by pressurization.

A known electrolysis method can be used for nickel plating on the nonwoven fabric. In addition, before giving nickel plating to a nonwoven fabric, the layer which has electroconductivity is formed in the nonwoven fabric surface, more specifically the fiber surface which comprises a nonwoven fabric. As means for forming the conductive layer, an electroless plating method or a sputtering method can be used. For example, when using an electroless plating method, after immersing a nonwoven fabric in a palladium chloride solution as an activation treatment, the nonwoven fabric is immersed in an electroless nickel plating bath. For example, when using a sputtering method, a non-woven fabric is attached to the substrate holder, a DC high voltage is applied between the holder and the target (nickel) while introducing the inert gas, and the ionized inert gas collides with the nickel. Then, the nickel particles blown off are deposited on the nonwoven fabric surface. Here, the formation amount of the conductive layer is preferably about 4 g / m ² to 9 g / m ² . A current collector in which a nickel layer is formed on the fiber surface can be produced by applying electro-nickel plating to the nonwoven fabric provided with conductivity using a nickel plating bath. Examples of the plating bath include a watt bath, a chloride bath, and a sulfamic acid bath.

The nickel plating amount of the current collector is 20 g / m ² or more and 70 g / m ² or less in consideration of the usefulness of the present invention. The amount of nickel in the current collector is preferably 20 g / m ² or more in terms of conductivity and 70 g / m ² or less in terms of price, particularly in the case of a negative electrode used in a high-power type battery. In addition, when the amount of nickel exceeds 70 g / m ² , the filling density of the hydrogen storage alloy decreases in addition to the price, and the weight of the negative electrode increases, which is not preferable. For example, in the case of a negative electrode used for a high-power type battery that discharges at 10 C to 30 C, the use of a current collector with a nickel amount of 70 g / m ² has sufficient high-power characteristics and cycle characteristics. For example, in the case of a negative electrode used for a high-capacity type battery that discharges at 1 C to 2 C, using a current collector with a nickel amount of 20 g / m ² has sufficient discharge characteristics and cycle characteristics. Therefore, the nickel amount of the current collector may be appropriately determined within a range of 20 g / m ² or more and 70 g / m ² or less in consideration of output characteristics and capacity characteristics of the negative electrode.

  In the hydrogen storage alloy negative electrode for an alkaline battery of the present invention, the current collector is a three-dimensional nickel porous body, and the current collector is filled with most or all of the hydrogen storage alloy in the skeleton of the current collector. It is excellent in performance, and it is possible to suppress the swelling of the negative electrode by suppressing the drop from the current collector accompanying the pulverization of the hydrogen storage alloy and suppressing the volume expansion of the alloy. In addition, the negative electrode of the present invention is light and inexpensive with a small amount of nickel, and has a high filling density of the hydrogen storage alloy. An alkaline battery provided with such a hydrogen storage alloy negative electrode is excellent in discharge characteristics and cycle characteristics.

  Embodiments of the present invention will be described below.

<Hydrogen storage alloy>
As the hydrogen storage alloy, an Mm-Ni-Mn-Al-Co alloy (Mm: Misch metal) obtained by adding Mn, Al, and Co to an Mm-Ni alloy was used. This alloy was prepared by mixing at a ratio of MmNi _4.1 Mn _0.3 Al _0.3 Co _0.35 and melting in an arc melting furnace. This alloy was pulverized to a particle size of 300 mesh or less in an inert atmosphere and processed into a powder. This alloy powder was mixed with 1.5% by mass SBR aqueous emulsion as a binder and 0.1% by mass CMC as a thickener. And kneaded to prepare a hydrogen storage alloy paste.

  Next, the paste was filled in a current collector to produce a hydrogen storage alloy negative electrode, and the capacity density of the hydrogen storage alloy negative electrode was examined. The hydrogen storage alloy negative electrode was prepared by filling the paste in commercially available foamed nickel and press-molding so that the electrode area was 5 × 5 cm and the thickness was 0.5 mm. As the positive electrode, a nickel electrode obtained by filling commercially available foamed nickel with nickel hydroxide as a positive electrode active material was used so that the positive electrode capacity was sufficiently larger than the negative electrode capacity. A positive electrode was disposed on both sides of the negative electrode via a separator, and an open type test battery in which the negative electrode capacity was regulated (regulated) was produced. The electrolyte was fully charged with potassium hydroxide in which lithium hydroxide was dissolved and charged and discharged at 0.2 C. The discharge capacity became almost constant in 3 cycles, and the discharge capacity density of this negative electrode was 270 mAh / g. Met.

  By the way, as a method for evaluating a hydrogen storage alloy negative electrode, the negative electrode regulation battery as described above is often manufactured and the discharge characteristics and the cycle characteristics are examined. In the negative electrode regulation, oxygen gas generated during charging is absorbed by the negative electrode. I can't. Therefore, in a sealed nickel-hydrogen battery in practical use, the positive electrode regulation, that is, the negative electrode capacity is made sufficiently larger than the positive electrode capacity. Therefore, in the examples of the present invention, a positive electrode-regulated battery is manufactured in the same manner as a battery in practical use, the discharge characteristics, the cycle characteristics, and the gas absorption of the negative electrode are examined, and the hydrogen storage alloy negative electrode of the present invention is evaluated. It was decided.

  Using the hydrogen storage alloy negative electrode of the present invention, a high-power type nickel-hydrogen battery was fabricated and the performance of the negative electrode was evaluated.

<Production of non-woven fabric>
As the fiber, a fiber (average fiber diameter 15 μm, weight ratio of polypropylene to polyethylene 7: 3) in which polypropylene is coated around the center of polypropylene was used. The nonwoven fabric was prepared using a wet method so that the weight per unit area was 45 g / m ² and the average thickness was 0.70 mm. The resulting nonwoven fabric had a porosity and pore size of 95% and 15 to 170 μm.

<Creation of current collector>
The nonwoven fabric was subjected to nickel plating using an electrolytic plating method to produce a current collector. Prior to electrolytic nickel plating, a conductive layer was formed on the nonwoven fabric surface by sputtering. Specifically, a nonwoven fabric was attached to the substrate holder, the chamber was evacuated, and then a DC high voltage was applied between the holder and the target (nickel) while introducing an inert gas. And the electroconductive layer was formed by making the ionized inert gas collide with nickel and depositing the nickel particle which blew off on the nonwoven fabric surface. The amount formed was 8 g / m ² . Electrolytic nickel plating was performed on the nonwoven fabric on which the conductive layer was formed. Specifically, a nickel piece was placed in a titanium basket as a counter electrode, and a Watt bath containing nickel sulfate 330 g / L, nickel chloride 50 g / L, and boric acid 40 g / L as a plating solution was used. And after heating this plating solution to 60 degreeC, the nonwoven fabric wound around the carrier was sent in in the plating solution, and nickel plating was given to the nonwoven fabric. The average amount of nickel in the current collector was 70 g / m ² .

<Production of negative electrode>
The current collector was filled with the above-described hydrogen storage alloy paste by using a known paste press-fitting method in which the current was lightly pressurized with a pump from one side to prepare an electrode substrate. The electrode substrate was cut into a length of 330 mm and a width of 30 mm, and then roll-pressed in the length direction using a roller press to produce a hydrogen storage alloy negative electrode. The roller press was composed of a pair of rollers having a diameter of 300 mm, the slit between the rollers was 100 μm, and the feed rate of the electrode substrate was 50 cm / min. Further, the roller surface is provided with irregularities, and the negative electrode is embossed. The average thickness of the negative electrode after pressurization was 390 μm. This negative electrode was designated as negative electrode a.

  FIG. 1 is a schematic cross-sectional view of the obtained hydrogen storage alloy negative electrode, which is cut in the thickness direction of the negative electrode. A nickel layer 13 was formed on the surface of the fiber 11, and a continuous nickel layer 13 was formed so as to cover this portion at the intersection 12 between the fibers. Further, the negative electrode 10 was filled with the hydrogen storage alloy powder 14 uniformly and with high density.

  The filling of the hydrogen storage alloy paste was easy because the specific gravity of the alloy was large and the porosity of the nonwoven fabric was large. Furthermore, it was found that by adding about 0.1% of a surfactant (polyoxyethylene alkyl ether) to this paste, it becomes easier to fill the non-woven fabric with the paste.

<Production of battery>
A SubC size nickel-hydrogen battery using the obtained negative electrode was fabricated. This battery was fabricated by inserting a spiral electrode group with a separator between a positive electrode and a negative electrode into a battery case, injecting an electrolyte, and sealing. Moreover, it comprised so that the outer peripheral part of a negative electrode might contact a battery case. A battery using the negative electrode a was designated as battery A.

  As the positive electrode, a nickel electrode in which commercially available foamed nickel was filled with nickel hydroxide as a positive electrode active material was used. Specifically, this nickel electrode was prepared by filling foamed nickel with a paste mainly composed of nickel hydroxide powder having a cobalt oxyhydroxide layer formed on the surface thereof. The nickel electrode was 270 mm long, 30 mm wide, and 450 μm thick so that the calculated capacity ratio of the positive electrode to the negative electrode was 1.6.

  As the separator, a polypropylene nonwoven fabric having a thickness of 130 μm and subjected to hydrophilic treatment was used. Moreover, the potassium hydroxide aqueous solution which lithium hydroxide melt | dissolved was used for electrolyte solution.

Using the same non-woven fabric as that of the negative electrode a, a negative electrode b in which the amount of nickel in the current collector was 40 g / m ² was prepared in the same process as the negative electrode a. For comparison, a negative electrode c in which the amount of nickel in the current collector was 200 g / m ² was produced. Further, a negative electrode d using a punching metal having a porosity of 50%, a hole diameter of 0.5 mm, and a thickness of 0.10 mm as a current collector was produced. The punch metal was subjected to nickel plating with an average thickness of 5 μm, and the negative electrode d was produced by applying a hydrogen storage alloy paste to the punching metal, and the thickness was set to 390 μm. Batteries using the negative electrodes b to d were designated as batteries B, C, and D, respectively.

  Next, each battery was formed by repeating charge and discharge three times at a low rate. Specifically, the battery is charged to 140% of the calculated capacity at 0.1C, discharged once to a final voltage of 0.9V at 0.2C, charged to 120% of the calculated capacity at 0.2C, and discharged to 0.9V at 0.2C. Chemical conversion was performed by charging once to 115% of the calculated capacity at 0.5 C, and discharging once to 0.5 V at a final voltage of 0.9 V at 0.5 C.

<Battery discharge characteristics>
The discharge characteristics of batteries A, B, C, and D were examined in a room temperature environment of 25 ° C. The charge / discharge conditions are: charge at 1 C with a current of -ΔV (5 mV), discharge at 1 C to 0.9 V, repeat this for 15 cycles, and then set the discharge conditions to a final voltage of 0.7 V, 10 C and 15 C Discharge was performed and the intermediate voltage at this time was determined. The results are shown in Table 1.

  As is clear from Table 1, the discharge voltages of the batteries A and B of the present invention were almost the same as the battery C and higher than the battery D.

  From this result, the negative electrode of the present invention has the same high output characteristics as the negative electrode with a large amount of nickel in the current collector, and sufficient high output characteristics can be obtained even if the nickel content of the current collector is reduced. I understand that. Moreover, it turns out that the negative electrode of this invention is excellent in the high output characteristic compared with the negative electrode which used punching metal for the electrical power collector.

<Battery cycle characteristics>
The cycle characteristics of batteries A, B, C, and D were examined in a high temperature environment of 45 ° C. The charge / discharge conditions were set to charge at a current of −ΔV (5 mV) at 1 C and discharged to 0.9 V at 1 C, and this was repeated as one cycle, and the capacity maintenance rate (utilization rate) in each cycle was determined. The results are shown in Table 2. Since the discharge capacity at the beginning of the charge / discharge cycle (4 cycles) was about 102% of the calculated capacity for all the batteries, the capacity maintenance rate of each battery was determined with this as 100%.

  As is clear from Table 2, there was no difference in capacity retention rate for any of the batteries up to 500 cycles. This proves that the positive electrode rule is obtained, and none of the batteries has a problem with the negative electrode. However, the capacity retention rate at 700 cycles was 80% or more for batteries A, B, and C, but decreased to 78% for battery D. This is presumably because the current collector of the negative electrode d used in the battery D was a punching metal having a two-dimensional structure, and the hydrogen storage alloy was pulverized and dropped from the current collector by repeated charge and discharge. Another possible cause is that the alloy has expanded as the hydrogen storage alloy is pulverized to absorb the electrolytic solution and the electrolytic solution in the separator is reduced.

  From this result, the negative electrode of the present invention has cycle characteristics equivalent to those of the negative electrode having a large amount of nickel in the current collector, and sufficient cycle characteristics can be obtained even if the nickel content of the current collector is reduced. I understand. Moreover, it turns out that the negative electrode of this invention is excellent in cycling characteristics compared with the negative electrode which used punching metal for the electrical power collector.

<Gas absorbability of negative electrode>
Furthermore, the gas absorptivity during charging, that is, the ability to return oxygen gas generated from the positive electrode at the end of charging to water at the negative electrode was investigated. Specifically, it was examined based on the presence or absence of battery leakage or weight loss. As a result, there was no difference in any of the batteries. In addition, when a battery having a calculated capacity ratio between the positive electrode and the negative electrode of 1.2 was prepared and the gas absorbency during charging was similarly examined, the gas absorbency decreased. There was no difference.

  Using the hydrogen storage alloy negative electrode of the present invention, a high capacity type nickel-hydrogen battery was fabricated, and the performance of the negative electrode was evaluated.

<Production of non-woven fabric>
As in the case of Example 1, a fiber (average fiber diameter: 20 μm, weight ratio of polypropylene to polyethylene of 5: 5) in which polypropylene is coated around the center as in the case of Example 1 was used. The nonwoven fabric was prepared using a wet method so that the weight per unit area was 60 g / m ² and the average thickness was 0.90 mm. The resulting nonwoven fabric had a porosity and pore size of 95% and 15 to 200 μm.

<Creation of current collector>
The nonwoven fabric was subjected to nickel plating in the same manner as in Example 1 to produce a current collector. The average amount of nickel in the current collector was 20 g / m ² .

<Production of negative electrode>
The current collector was filled with the above-described hydrogen storage alloy paste using a known paste press-fitting method to produce an electrode substrate, and this electrode substrate was cut into a length of 250 mm and a width of 30 mm, and then a roller press. Using a machine, roll pressure was applied in the length direction to produce a hydrogen storage alloy negative electrode. The same roller press machine as in Example 1 was used, the slit between the rollers was 100 μm, and the feed rate of the electrode substrate was 50 cm / min. The thickness of the negative electrode after pressing was an average of 480 μm. This negative electrode was designated as negative electrode i.

<Production of battery>
A SubC size nickel-hydrogen battery using the obtained negative electrode was fabricated. This battery was produced in the same manner as in Example 1, and a battery using the negative electrode i was designated as battery I.

Using the same non-woven fabric as that of the negative electrode i, a negative electrode ii in which the amount of nickel in the current collector was 30 g / m ² was produced in the same process as the negative electrode i. For comparison, a negative electrode iii having a current collector with a nickel content of 150 g / m ² was produced. Further, a negative electrode iv was produced using a punching metal having a porosity of 50%, a hole diameter of 0.5 mm, and a thickness of 0.15 mm as a current collector. The punch metal was subjected to nickel plating with an average thickness of 5 μm, and the negative electrode iv was prepared by applying a hydrogen storage alloy paste to the punching metal to a thickness of 480 μm. Batteries using the negative electrodes ii to iv were designated as batteries II, III, and IV, respectively.

  Next, each battery was formed by repeating charging and discharging 5 times at a low rate. Specifically, charging to 130% of the calculated capacity at 0.1C, discharging to 0.9V of the final voltage at 0.2C, charging to 120% of the calculated capacity at 0.2C, and discharging to 0.9V of the final voltage at 0.2C Chemical conversion was carried out by charging twice to 115% of the calculated capacity at 0.5 C and discharging twice to a final voltage of 0.9 V at 0.5 C.

<Battery discharge characteristics>
The discharge characteristics of each battery I, II, III, and IV were examined in a room temperature environment of 25 ° C. The charge / discharge conditions were set to 0.5C at a current of -ΔV (5mV), 0.5C to 0.9V, and after 15 cycles, the discharge conditions were set to a final voltage of 0.7V and 1C. And the discharge was changed to 2C, and the intermediate voltage at this time was determined. The results are shown in Table 3.

  As is apparent from Table 3, the discharge voltages of the batteries I and II of the present invention were almost the same as the battery III and higher than the battery IV.

  From this result, the negative electrode of the present invention has a discharge characteristic equivalent to that of a negative electrode with a large amount of nickel in the current collector, and sufficient discharge characteristics can be obtained even if the amount of nickel in the current collector is reduced. I understand. Moreover, it turns out that the negative electrode of this invention is excellent in the discharge characteristic compared with the negative electrode which used punching metal for the electrical power collector.

<Battery cycle characteristics>
The cycle characteristics of each battery I, II, III, and IV were examined in a high temperature environment of 25 ° C. Charge / discharge conditions are as follows: charge at a current of -ΔV (5 mV) at 0.2 C, discharge to 0.9 V at 0.5 C, and repeat this as one cycle to obtain the capacity maintenance rate (utilization rate) at each cycle. It was. The results are shown in Table 4. Since the discharge capacity at the beginning of the charge / discharge cycle (5 cycles) was about 103% of the calculated capacity for all the batteries, the capacity maintenance rate of each battery was determined with this as 100%.

  As is clear from Table 4, there was no difference in capacity retention rate for any battery up to 800 cycles. This proves that the positive electrode rule is obtained, and none of the batteries has a problem with the negative electrode. However, the capacity retention rate at 1000 cycles was 85% or more for batteries I, II, and III, but decreased to 79% for battery IV. This is presumably because the current collector of the negative electrode iv used in the battery IV was a punching metal having a two-dimensional structure, and the hydrogen storage alloy was pulverized and dropped from the current collector due to repeated charge and discharge. Another possible cause is that the alloy has expanded as the hydrogen storage alloy is pulverized to absorb the electrolytic solution and the electrolytic solution in the separator is reduced.

  From this result, the negative electrode of the present invention has cycle characteristics equivalent to those of the negative electrode having a large amount of nickel in the current collector, and sufficient cycle characteristics can be obtained even if the nickel content of the current collector is reduced. I understand. Moreover, it turns out that the negative electrode of this invention is excellent in cycling characteristics compared with the negative electrode which used punching metal for the electrical power collector.

<Gas absorbability of negative electrode>
Further, in the same manner as in Example 1, the gas absorbability during charging was examined. As a result, there was no difference in any of the batteries. In addition, when a battery having a calculated capacity ratio between the positive electrode and the negative electrode of 1.2 was prepared and the gas absorbency during charging was similarly examined, the gas absorbency decreased. There was no difference.

  As described above, as shown in Examples 1 and 2, the hydrogen storage alloy negative electrode of the present invention uses a small amount of nickel and can keep costs low. In addition, the negative electrode of the present invention is light in weight of about 1/2 to 1/3 as compared with a negative electrode using a punching metal as a current collector, and the manufacturing process is simple.

  The hydrogen storage alloy negative electrode of the present invention is excellent in discharge characteristics and cycle characteristics (life), and can be suitably used for alkaline batteries. Moreover, the alkaline battery of the present invention can be suitably used as a power source for portable, mobile and industrial equipment.

It is a schematic cross section of the hydrogen storage alloy negative electrode of the present invention.

Explanation of symbols

10 Negative electrode
11 Fiber 12 Intersection of fibers 13 Nickel layer 14 Hydrogen storage alloy

Claims (11)

A hydrogen storage alloy negative electrode for an alkaline battery in which a current storage body is filled with a hydrogen storage alloy,
The current collector is a three-dimensional nickel porous body in which a non-woven fabric made of alkali-resistant fibers is plated with nickel. The amount of nickel in the current collector is from 20 g / m ^{2 to} 70 g / m ² A hydrogen storage alloy negative electrode for alkaline batteries.   The hydrogen storage alloy negative electrode for an alkaline battery according to claim 1, wherein the nonwoven fabric has a porosity of 85% or more and 97% or less.   The hydrogen storage alloy negative electrode for an alkaline battery according to claim 1, wherein the nonwoven fabric is subjected to a heat treatment after interlaced between the fibers. The alkali resistant fiber is a polyolefin fiber,
2. The hydrogen storage alloy negative electrode for an alkaline battery according to claim 1, wherein the polyolefin fiber contains one selected from the group consisting of polyethylene, polypropylene, a mixture thereof, and a copolymer thereof.   2. The alkali according to claim 1, wherein the nickel plating is applied to the nonwoven fabric using an electrolytic plating method after imparting conductivity to the nonwoven fabric using at least one of a sputtering method and an electroless plating method. Hydrogen storage alloy negative electrode for batteries.   The hydrogen storage alloy negative electrode for an alkaline battery according to claim 1, wherein the hydrogen storage alloy contains a conductive agent, and the content thereof is 5 mass% or less.   The hydrogen storage alloy negative electrode for an alkaline battery according to claim 1, wherein the hydrogen storage alloy contains a binder and the content thereof is 3% by mass or less.   The hydrogen storage alloy filled in the current collector is a paste obtained by adding a thickener aqueous solution to a hydrogen storage alloy powder, and the paste is filled into the current collector and then pressurized. The hydrogen storage alloy negative electrode for alkaline batteries as described.   The hydrogen storage alloy negative electrode for an alkaline battery according to claim 8, wherein the thickness of the nonwoven fabric before pressurization is 1.2 to 2.0 times the thickness of the hydrogen storage alloy negative electrode obtained by pressurization. .   An alkaline battery comprising the hydrogen storage alloy negative electrode for an alkaline battery according to claim 1.   The alkaline battery according to claim 10, wherein the negative electrode and the battery case are in contact with each other, and the battery case also serves as a negative electrode terminal.

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