JP2004119020A - Negative electrode for alkaline storage battery and alkaline storage battery using the same and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline storage battery that has excellent charge and discharge cycle characteristics and in which increase in the internal pressure of the battery at charging is suppressed. <P>SOLUTION: This is a negative electrode for the alkaline storage battery in which the active material powder is carried by the substrate, and in the substrate an oxide and a hydroxide of at least one kind of metal elements selected from transitional metals having alkaline electrolyte resistance and lead are reduced and a layer made of that metal is arranged on the surface of a core material made of the alkaline resistant metal, and that negative electrode is applied to this alkaline storage battery. The quantity of the metal contained in the above layer is made 0.02 millimole/cm<SP>2</SP>-0.35 millimole/cm<SP>2</SP>per unit area of the core material. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a negative electrode applied to an alkaline storage battery such as a nickel metal hydride battery and a nickel cadmium battery, an alkaline storage battery using the same, and a method for manufacturing the same.
[0002]
[Prior art]
Alkaline storage batteries have excellent resistance to overcharge and overdischarge and are easy to use for general users, so they are widely used as power sources for portable small electronic devices such as mobile phones, small power tools and small personal computers. The demand for these small electronic devices has been dramatically increased with the spread of these small electronic devices. Further, it has been put to practical use as a power supply for driving a hybrid electric vehicle (HEV). Further, there is a demand for further increase in capacity and improvement in charge / discharge cycle performance of alkaline storage batteries.
[0003]
The negative electrode of the alkaline battery is one in which a paste mainly containing a hydrogen storage alloy or cadmium hydroxide as an active material is supported on a porous substrate of an alkali-resistant and highly conductive metal such as iron, nickel and copper. is there.
[0004]
The porous substrate serving as the substrate of the negative electrode plate includes a metal plate made of nickel or a nickel-plated steel plate, a punched metal formed by mechanically perforating a metal plate, a fiber substrate formed by forming metal fibers into a felt shape. And foamed metal obtained by molding a metal into a sponge shape. In a conventional alkaline storage battery, the surface of these substrates was used without being processed. Of the above-mentioned substrates, punching metal is heavily used for a substrate for a negative electrode of an alkaline storage battery because of its low cost and easy availability. However, a negative electrode plate using the punched metal as a substrate does not have sufficient adhesion between the active material powder and the substrate, and improvement has been required.
[0005]
In the nickel-metal hydride battery and the nickel cadmium battery, a nickel electrode is applied to the positive electrode. The nickel electrode is obtained by filling an active material paste mainly containing nickel hydroxide as an active material into a porous nickel substrate such as foamed nickel.
[0006]
An alkaline storage battery combines the positive electrode and the negative electrode to form a battery, and oxidizes nickel hydroxide to nickel oxyhydroxide at a nickel electrode as a positive electrode by charging, and a hydrogen storage alloy at a hydrogen storage alloy electrode as a negative electrode. At the cadmium electrode, hydrogen is absorbed, and cadmium hydroxide is reduced to cadmium metal.
[0007]
By the way, in the nickel electrode, in addition to nickel hydroxide powder as an active material, cobalt monoxide or cobalt hydroxide is added to increase conductivity in the electrode, and the cobalt hydroxide is made conductive by charging the battery. High-order cobalt compound (also called cobalt oxyhydroxide). The reaction when the higher cobalt compound is generated by charging is an irreversible reaction, and an amount of electricity corresponding to the amount of electricity consumed for generating the higher cobalt compound by charging is latently discharged to the negative electrode as a discharge reserve. Will be stored.
[0008]
When the generation amount of the discharge reserve increases, the charge reserve amount decreases, which may lead to a reduction in the charge / discharge cycle life. In order to prevent a decrease in the charge reserve, it is necessary to allow for the filling of an active material for forming a discharge reserve in the negative electrode when designing a battery. Excessive filling of the negative electrode active material in anticipation of the formation of the discharge reserve reduces the filling amount of the positive electrode active material, resulting in a decrease in the discharge capacity of the battery.
[0009]
In order to suppress the generation of a discharge reserve, a method of previously oxidizing a cobalt compound such as cobalt hydroxide disposed on the surface of nickel hydroxide, which is an active material of a nickel electrode, by a chemical method and converting it to a higher cobalt compound has been proposed. It has been proposed (for example, see Patent Documents 1 and 2).
[0010]
[Patent Document 1]
JP-A-3-78965 (page 3, upper left column, lines 14 to 16)
[Patent Document 2]
JP-A-4-26058 (page 2, upper right column, lines 9 to 10)
[0011]
In addition, in addition to the active material such as hydrogen storage alloy or cadmium powder in the negative electrode, cobalt monoxide or cobalt hydroxide is added, and the amount of electricity consumed in the irreversible reaction is canceled according to the following reaction, thereby reducing the discharge reserve. Methods to prevent generation are also conceivable.
Positive electrode @ Co (OH)₂+ (OH)⁻→ CoOOH + H₂O + e⁻
Negative electrode 1 / 2CoO + ／ H₂O + e⁻→ 1 / 2Co + (OH)⁻
[0012]
As described above, a method has been proposed in which cobalt monoxide is added to the hydrogen storage alloy powder as the negative electrode active material, and metal cobalt is generated on the surface of the negative electrode by charging (for example, Patent Document 3 and Patent Document 4). ).
[0013]
[Patent Document 3]
JP-A-6-150921 (page 2, paragraph 0009)
[Patent Document 4]
JP-A-10-3939 (page 2, paragraph 0004)
[0014]
In addition to a method of forming a layer of cobalt hydroxide on the surface of the negative electrode (for example, see Patent Document 5), an oxide of one or more metals selected from Co, Cu, Ru, Pd and other metals or water A method of adding an oxide (see Patent Document 6) has been proposed.
[0015]
[Patent Document 5]
JP-A-4-34850 (page 2, lower right column, lines 12 to 14)
[Patent Document 6]
JP-A-9-223500 (pages 2 to 3, paragraphs 0010 and 0011)
[0016]
However, in the method of arranging cobalt hydroxide on the surface of the negative electrode or adding a compound such as a metal oxide or hydroxide to the active material powder of the negative electrode, only a part of the added compound is a current collector of the negative electrode. Is not in direct contact with the substrate. Compounds that are not in contact with the substrate may remain without being reduced even after charging, and thus have a disadvantage that the effect of suppressing the generation of discharge reserve is not sufficient.
[0017]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described disadvantages of the related art, and is an alkaline storage battery in which a hydrogen storage alloy electrode or a cadmium electrode is applied to a negative electrode. Another object of the present invention is to provide an alkaline storage battery having an excellent function of suppressing an increase in battery internal pressure during overcharge.
[0018]
[Means for Solving the Problems]
The present invention is a negative electrode for an alkaline storage battery in which an active material powder such as a hydrogen storage alloy powder or cadmium oxide is supported on a substrate, wherein the substrate has a core material made of nickel or an alkali-resistant metal plated with nickel. A negative electrode having a layer made of at least one metal selected from transition metals and lead having alkali-electrolyte resistance on the surface is provided.
[0019]
In the present invention, the amount of metal contained in the metal layer disposed on the substrate surface of the negative electrode is set to 0.02 mmol / cm per unit area of the core material.²~ 0.35 mmol / cm²It is desirable that Here, the area of the unit area of the core material means an apparent size including an opening of the core material. For example, the area of a punching metal or metal foam having a size of 10 mm × 10 mm is 1 cm.²It is.
[0020]
An alkaline storage battery according to the present invention is an alkaline storage battery in which the hydrogen storage alloy electrode or the cadmium electrode according to claim 1 of the present invention is applied to a negative electrode, and has a discharge reserve of 0.5 to 18% of the rated capacity. It is desirable. The term “discharge reserve amount” as used herein refers to a result measured for a battery that has passed several cycles (2 to 3 cycles) to 30 charge / discharge cycles including formation. The alkaline storage battery does not differ from the conventional alkaline storage battery except that the metal reserve is provided on the surface of the core material of the negative electrode to reduce the discharge reserve in the battery configuration. The alkaline storage battery is excellent in the function of suppressing internal pressure rise and the cycle performance when the battery is overcharged without lowering the substance utilization rate.
[0021]
The method for manufacturing an alkaline storage battery according to the present invention is characterized in that the transition metal or lead deposited in a layer on the surface of the core material of the substrate is temporarily changed to an oxide or hydroxide, and the active material powder is supported on the substrate. After that, the battery is incorporated into a battery, and the oxide is reduced in the step of charging the battery, thereby reducing the transition metal or the oxide or hydroxide of lead to a metal.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
The negative electrode for an alkaline storage battery according to the present invention is a hydrogen storage alloy electrode, a cadmium electrode, or the like. These electrodes are obtained by supporting a negative electrode active material such as a hydrogen storage alloy or cadmium on a substrate having a core material of an alkali-resistant metal such as iron, nickel or copper.
[0023]
The core material of the substrate applied to the present invention is a punching metal such as iron, nickel or copper, a fibrous core material formed by molding fibers of these metals, or a sponge-shaped foamed metal.
[0024]
In the present invention, a layer of a transition metal or a metal containing lead (Pb) is disposed on the surface of the core material. The transition metal contains 6 to 8 mol / dm.³Apply chemically stable substances to caustic potash and caustic soda. Specifically, cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), techtinium (Tc), ruthenium (Ru), rhodium (Rh), and iridium (Ir) can be applied. The transition metal applied to the present invention is preferably one whose oxide is slightly dissolved in an alkaline electrolyte. Here, a slight amount of dissolution means that the dissolution amount is 10^-2-10^-5Mol / dm³Say. It is desirable that the metal material be easily available and inexpensive. From such a point, Co, Ni, Cu, Ag and Pb are preferable as the metal element applied to the present invention.
[0025]
The transition metal or lead layer on the core material surface according to the present invention, after forming the transition metal or lead layer on the core material surface, once subjected to oxidation treatment to form the transition metal or lead oxide layer, A negative electrode provided with a substrate to which the core material is applied is formed by assembling it into a battery and reducing it by initial charging in a chemical conversion step.
[0026]
As a method of first forming a transition metal layer on the surface of the core material, a method such as vapor deposition or electroless plating can be applied. However, electrolytic plating is preferred because the amount of transition metal deposited can be accurately controlled. Specifically, an electrolytic bath in which the transition metal salt is dissolved is prepared, electrolysis is performed using the electrolytic bath with a core material as a negative electrode, and the surface of the core material is plated with a transition metal.
[0027]
Next, the transition metal deposited on the surface of the core material is converted into an oxide by a chemical reaction. Specifically, a method in which heating is performed in an atmosphere of oxygen or ozone, or an oxidation treatment using an oxidizing agent such as permanganate, chlorate, chlorite, or persulfate can be applied. Alternatively, a method of converting the transition metal into a hydroxide can also be applied. Specifically, the transition metal is converted into an oxide and then immersed in a caustic alkali, or the transition metal is precipitated on the surface of the core material and then electrolytically oxidized in an alkaline electrolyte to form a hydroxide of the transition metal. Is generated.
[0028]
An active material paste mainly containing a hydrogen storage alloy powder or a cadmium hydroxide powder is applied and filled on a substrate having a transition metal oxide layer formed on the surface of the core material. After drying the electrode plate filled with the active material paste, the electrode plate is pressed through a roll to increase the active material filling density.
[0029]
Oxides and hydroxides of the transition metal generated on the surface of the substrate have a low hardness, so that a part of the active material powder filled in the process of pressing through the roll is formed of the oxide or hydroxide of the transition metal. There is a tendency to cut into layers. Therefore, it is considered that the present invention has an effect of further improving the adhesion between the substrate and the active material powder.
[0030]
The negative electrode plate and the nickel electrode serving as the positive electrode plate thus manufactured are combined to form an alkaline storage battery. By charging the battery, the oxide layer of the transition metal is reduced to a metal. As described above, the transition metal oxide applied in the present invention is slightly dissolved in the alkaline electrolyte. Therefore, after incorporating the negative electrode into the battery, part of the transition metal oxide dissolves in the alkaline electrolyte and precipitates as a metal on the negative electrode during charging. Part of the metal deposited on the negative electrode is deposited on the boundary between the active material powder and the substrate and serves as a connection between the active material powder and the substrate, so that the active material powder and the substrate are firmly adhered to each other. It is considered that part of the metal is deposited in the negative electrode. The metal acts as a conductive agent at the same time as binding the active material powders of the negative electrode.
[0031]
Almost all of the oxide of the transition metal generated on the surface of the core material is in contact with the core material of the substrate, which is a current collector. As a result, when the battery is charged, reduction of the generated transition metal oxide proceeds almost completely, and unreacted oxide does not remain. As a result, the amount of electricity that causes the negative electrode to generate a discharge reserve when the battery is charged can be offset by the amount corresponding to the generated amount of the transition metal oxide. Therefore, the amount of discharge reserve generation can be controlled more accurately than the conventional method of adding a metal oxide to the negative electrode active material.
[0032]
In the present invention, the arrangement amount of the transition metal or lead is set to 0.02 mmol / cm per unit area of the core material.²~ 0.35 mmol / cm²It is desirable that The amount of the transition metal or lead is determined to be 0.05 mmol / cm per unit area of the core material.²~ 0.35 mmol / cm²More desirably. 0.02 mmol / cm of transition metal or lead²By doing so, an excellent discharge reserve generation suppressing effect can be obtained.
[0033]
If the amount of discharge reserve generated is too small, the discharge capacity when discharging is restricted by the performance of the negative electrode (negative electrode regulation). When the discharge capacity of the battery is regulated by the negative electrode, a drawback occurs in that the active material utilization rate decreases. In the present invention, the amount of transition metal or lead formed on the surface of the core material of the negative electrode substrate is set to 0.35 mmol / cm.²It is desirable to make the following. This can prevent the discharge capacity from being regulated by the negative electrode during discharge.
[0034]
Hereinafter, the present invention will be described in detail with reference to examples, focusing on examples in which cobalt is used as a transition metal.
(Example 1)
(Formation of a cobalt monoxide layer on the surface of the anode substrate core material)
A punching metal made of a steel plate having a thickness of 60 μm and a porosity of 40% plated with nickel was used as a core material. 1 mol / dm³And an aqueous solution containing 1 mol / dm3 of hydrochloric acid as an electrolytic bath. The punching metal is disposed at the center of the electrolytic bath, and cobalt plates are disposed on both sides. went. The current density of electrolysis per unit area of punching metal is 0.5 mA / cm²And Electrolysis is performed with 5 levels of electricity. Cobalt deposition amount per unit area of punching metal is 0.1 mmol / cm²Was prepared.
[0035]
The substrate material was set in an atmosphere furnace. The furnace was oxidized by heating at a temperature of 300 ° C. for 2 hours in an atmosphere of oxygen, and cobalt deposited on the surface of the core material was changed to cobalt monoxide to obtain a negative electrode substrate.
[0036]
(Preparation of hydrogen storage alloy electrode)
CaCu₅Type crystal structure, MmNi_3.6Al_0.29Co_0.75Mn_0.36(Mm is a misch metal and is a mixture of rare earth elements composed of La, Ce, Pr and Nd), and is increased with respect to 100 parts by weight of the hydrogen storage alloy powder having an average particle size of about 50 μm. A paste was prepared by adding and mixing 20 parts by weight of a 1 wt% aqueous solution of methylcellulose (MC) as a tackifier and 1 part by weight of styrene butadiene rubber as a binder. The paste was applied to both sides of the substrate and dried to obtain an electrode plate having a thickness of 1.1 mm. The dried electrode plate was pressed through a roll, the thickness was adjusted to 0.5 mm, and a hydrogen storage alloy electrode base plate was obtained. The original plate was cut into a predetermined size to obtain a hydrogen storage alloy electrode.
[0037]
(Preparation of nickel electrode active material powder)
Average particle size of a high-density nickel hydroxide containing 3% by weight and 5% by weight of hydroxide in solid solution in terms of hydroxide according to a standard method, and a coating layer of cobalt hydroxide formed on the surface. A nickel electrode active material powder mainly composed of nickel hydroxide having a particle size of 10 μm was prepared. The ratio of the cobalt hydroxide coating layer formed on the surface of the active material powder was 6% by weight.
[0038]
(Preparation of nickel electrode)
To 80 parts by weight of the obtained nickel electrode active material powder, 20 parts by weight of a 1% by weight aqueous solution of carboxymethyl cellulose (CMC) was added and kneaded to prepare a nickel electrode active material paste. The paste was 1.4 mm thick and the basis weight was 500 g / m.²After filling and drying into a foamed nickel porous substrate, the thickness was adjusted to 0.8 mm by pressing to obtain a long strip-shaped original plate for nickel electrodes. The original plate was cut into a predetermined size to obtain a nickel electrode. The capacity of the nickel electrode calculated from the active material filling amount was 1700 mAh.
[0039]
(Production of nickel-metal hydride battery)
The nickel electrode and the hydrogen storage alloy electrode were spirally wound around a separator having a thickness of 0.12 mm made of a nonwoven fabric of a polypropylene resin fiber subjected to a hydrophilic treatment, thereby producing an electrode plate group. The ratio of the active material filling capacity of the hydrogen storage alloy electrode and the nickel electrode of the electrode group was set to 1.6. This electrode group was housed in a cylindrical metal case, and was 7 mol / dm.³Potassium hydroxide aqueous solution and 1 mol / dm³A predetermined amount of an electrolytic solution composed of an aqueous solution of lithium hydroxide was injected. Next, the metal case was sealed with a metal lid provided with a safety valve to obtain an AA-size sealed nickel-metal hydride battery.
[0040]
(Chemical)
After aging the obtained nickel-metal hydride storage battery at a temperature of 40 ° C. for 12 hours, formation was performed under the following conditions. In the first charging, the battery was charged with a charging current of 1/50 ItA (34 mA) for 10 hours, and then charged with a charging current of 0.1 ItA (170 mA) for 10 hours. Next, discharge was performed at a discharge current of 0.2 ItA (340 mA) with a discharge end voltage of 1.0 V. After the second cycle, the battery was charged at a charge current of 0.1 ItA for 12 hours, and discharged at a discharge current of 0.2 ItA with a discharge end voltage of 1.0 V. The cycle was defined as one cycle, and the charge and discharge were repeated for 10 cycles including the first charge and discharge.
[0041]
(Example 2)
In Example 1, nickel oxide (NiO) was generated on the surface of the core material of the negative electrode substrate before coating the negative electrode active material paste. Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0042]
(Example 3)
In Example 1, copper oxide (CuO) was generated on the surface of the core material of the negative electrode substrate before coating the negative electrode active material paste. Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0043]
(Example 4)
In Example 1, silver oxide (AgO) was generated on the core material surface of the negative electrode substrate before coating the negative electrode active material paste. Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0044]
(Example 5)
In Example 1, lead oxide (PbO) was generated on the surface of the core material of the negative electrode substrate before coating the negative electrode active material paste. Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0045]
(Example 6)
In Example 1, the amount of Co deposited on the core material surface of the negative electrode substrate was 0.02 mmol / cm.²And Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
(Example 7)
In Example 1, the amount of Co deposited on the core material surface of the negative electrode substrate was 0.05 mmol / cm.²And Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
(Example 8)
In Example 1, the amount of Co deposited on the core material surface of the negative electrode substrate was 0.35 mmol / cm.²And Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0046]
(Example 9)
In Example 1, the amount of Co deposited on the surface of the core material of the negative electrode substrate was 0.4 mmol / cm.²And Except for this, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0047]
(Comparative Example 1)
The transition metal layer was not formed on the surface of the core material of the negative electrode substrate, and the core material was directly used as the negative electrode substrate. Otherwise, a nickel-metal hydride battery was manufactured under the same conditions as in Example 1.
[0048]
(Comparative Example 2)
Cobalt monoxide powder was added to the same negative electrode active material paste as in the example without forming a Co layer on the surface of the negative electrode substrate. A hydrogen storage alloy electrode was manufactured with the addition ratio of cobalt monoxide to the hydrogen storage alloy in the negative electrode active material paste being 6 wt%. The amount of cobalt monoxide contained in the electrode was the same as the amount of cobalt monoxide generated on the surface of the core material of the substrate of the hydrogen storage alloy electrode of Example 1. Otherwise, a nickel-metal hydride battery was manufactured under the same conditions as in the above-described example.
[0049]
(Measurement of discharge reserve generation amount)
After completion of the formation, the battery of Example and the battery of Comparative Example were charged and discharged for 10 cycles under the charging and discharging conditions for the second and subsequent cycles. The battery after the completion of the discharge after the charge / discharge cycle was disassembled. The negative electrode was collected. The negative electrode was immersed in water, and the hydrogen gas generated at that time was recovered by the water displacement method. The amount of discharge reserve was calculated from the amount of hydrogen gas collected.
[0050]
(Evaluation of active material utilization rate)
The battery of Example and the battery of Comparative Example after completion of the formation were charged at a temperature of 20 ° C. under the above conditions, subjected to a discharge test at a current of 0.2 ItA, and the discharge capacity in the 0.2 ItA discharge with respect to the positive electrode active material filling capacity. The ratio was defined as the active material utilization rate.
[0051]
(Survey of γ-NiOOH formation in positive electrode)
After completion of the formation, the batteries of Example 1 and Example 9 were charged at a temperature of 40 ° C. at 0.1 ItA for 15 hours, discharged at a current of 0.2 ItA at a discharge termination voltage of 1.0 V, and the charge / discharge was defined as 10 cycles. After repeating the cycle, the positive electrode active material collected by disassembling the battery was subjected to powder X-ray diffraction, and the (001) plane of γ-NiOOH and β-Ni (OH)₂Of (100) plane was obtained.
[0052]
(Measurement of internal pressure rise during overcharge)
After a pressure gauge for measuring the internal pressure of the battery was attached to the example battery and the comparative battery after the formation, the batteries were charged at 1 ItA (1700 mA) for 2 hours. The change over time in the internal pressure of the battery during charging was measured.
[0053]
(Charge / discharge cycle test)
The battery of Example and the battery of Comparative Example after the formation were subjected to a charge / discharge cycle test at a temperature of 20 ° C. Charging was performed with an ItA current for 1.2 hours, and discharging was performed with an ItA current with a discharge end voltage of 1.0 V. The cycle was repeated with the charge / discharge cycle as one cycle.
[0054]
FIG. 1 is a graph showing the discharge reserve amounts of Example Battery 1 to Example Battery 9, Comparative Example Battery 1, and Comparative Example Battery 2 after formation. Incidentally, the ratio of the discharge reserve amount to the rated capacity (1700 mAh) of the batteries in Example Battery 1 to Example Battery 9 was 5.4%, 5.5%, 6.8%, 7.0%, and 6.0, respectively. They are 3%, 18%, 9%, 0.5% and 0%. The ratios of the discharge reserve amounts of Comparative Example Battery 1 and Comparative Example Battery 2 are 20% and 11%, respectively.
[0055]
As shown in FIG. 1, each of the batteries of the example has a smaller amount of discharge reserve than the battery 1 of the comparative example. This is because the transition metal oxide generated on the surface of the core material of the negative electrode substrate suppresses the generation of the discharge reserve. In addition, as shown in Example Battery 1 to Example Battery 5, all of CoO, NiO, CuO, AgO, and PbO deposited on the surface of the core material of the substrate effectively functioned to suppress discharge reserve generation. It is shown that.
[0056]
The amount of CoO generated on the core material surface of the negative electrode substrate of Example Battery 1 and the amount of CoO mixed and added to the active material powder of Comparative Example Battery 2 are equivalent. Nevertheless, the discharge reserve of Example Battery 1 is smaller than that of Comparative Battery 2 by about 比較. This indicates that the transition metal oxide generated on the substrate surface of the negative electrode suppresses the generation of the discharge reserve more efficiently than the transition metal oxide mixed and added to the active material powder.
[0057]
In Example Battery 1, Example Battery 6 to Example Battery 9, CoO was generated on the surface of the core material of the negative electrode substrate. The larger the amount of CoO generated, the smaller the amount of discharge reserve generated. It is suggested that there is a correlation between the amount of generation of the gas and the amount of generation of the discharge reserve. This means that the discharge reserve amount of the alkaline storage battery can be freely controlled by applying the negative electrode for an alkaline battery in which the amount of the transition metal oxide generated on the core material surface of the negative electrode substrate as in the present invention is applied. Indicates that it can be done.
[0058]
FIG. 2 shows the active material utilization rates of Example Battery 1, Example Battery 8 and Example Battery 9. As described above, the ratio of the discharge reserve amount to the rated capacity of the battery is 5.4% for Example Battery 1, 0.5% for Example Battery 8, and 0% for Example Battery 9. As shown in FIG. 2, both the example battery 1 and the example battery 8 have an active material utilization of 100%, while the example battery 9 has a low utilization of 76%. It is considered that this is because the amount of reduction in the discharge reserve was large and the discharge reserve was too small, and the discharge capacity fell into the negative electrode regulation.
[0059]
FIG. 3 shows the (001) plane of γ-NiOOH and β-Ni (OH) in Example Battery 1 and Example Battery 9.₂The diffraction intensity ratio of the (100) plane was shown. In Example Battery 9, the diffraction intensity ratio was high, indicating that the amount of γ-NiOOH generated was larger than that in Example Battery 1. As described above, since the battery 9 of the embodiment falls under the regulation of the negative electrode, the positive electrode is not fully discharged but overcharged in each cycle. Therefore, it is considered that as the charge / discharge cycle progresses, the amount of accumulated overcharge electricity increases and the amount of γ-NiOOH generated increases. From the above results, it is desirable to set the ratio of the discharge reserve amount to the rated capacity of the battery to 0.5% or more.
[0060]
FIG. 4 shows the internal pressure of the battery when the example battery 1, the example batteries 6 to 8 and the comparative example battery 1 were overcharged. In each of the batteries of the examples, the increase in the internal pressure is smaller than that of the batteries of the comparative examples. In particular, the increase in the internal pressure of Example Battery 1, Example Battery 7, and Example Battery 8 is small. It is considered that the amount of hydrogen generated at the negative electrode during overcharging was small in the example battery because the amount of generated discharge reserve was small, and the increase in the internal pressure of the battery was suppressed. Further, it is considered that the increase in the internal pressure of the battery was also suppressed by the promotion of oxygen absorption by the catalytic action of the transition metal oxide generated on the substrate of the negative electrode to promote the oxygen absorption reaction in the negative electrode.
[0061]
The ratio of the discharge reserve amount of the example battery shown in FIG. 4 is 0.5% of the example battery 8 to 18% of the example battery 6, and the smaller the ratio of the discharge reserve amount, the higher the internal pressure of the battery. There is a tendency to be suppressed. In Example 7 in which the ratio of the discharge reserve amount was 9%, the increase in the internal pressure of the battery was significantly suppressed. Summarizing the above results, if the discharge reserve amount is 18% or less, it is effective for the function of suppressing an increase in the internal pressure of the battery when overcharged, and more remarkable when the ratio of the discharge reserve amount is 9% or less. It can be seen that a special effect can be obtained.
[0062]
FIG. 5 is a graph showing the charge / discharge cycle performance of Example Battery 1 to Example Battery 8 and Comparative Example Battery 1. The cycle performance of each of the batteries of the examples was superior to that of the battery of the comparative example. In the case of the example battery, the adhesion between the hydrogen storage alloy powder of the negative electrode and the substrate was excellent as described above, and the generation of the discharge reserve was controlled so as to be in a preferable range. In the case of the battery of the present invention, it is considered that these two factors together result in excellent cycle performance. It is considered that the reason why excellent cycle performance is obtained when the generation of the discharge reserve is suppressed is that a sufficient amount of charge reserve is secured.
[0063]
From the results described above, in order to obtain excellent cycle performance, it is preferable that the ratio of the discharge reserve to the rated capacity of the battery be 18% or less, and that the negative electrode is regulated in the discharge and the active material utilization rate is prevented from lowering. It is preferable that the ratio of the discharge reserve is 0.5% or more. Furthermore, in order to obtain an excellent effect in the function of suppressing an increase in the internal pressure of the battery when the battery is overcharged, the ratio of the discharge reserve is desirably 18% or less, and more desirably 9% or less. I understand.
[0064]
As described above, according to the present invention, the discharge reserve amount of the alkaline storage battery can be freely controlled by applying the negative electrode for an alkaline battery in which the amount of the transition metal oxide generated on the core material surface of the negative electrode substrate is controlled. be able to. According to the results of the trial production shown in FIG. 1, in order to control the discharge reserve amount to a preferable value of 0.5 to 18% of the rated capacity of the battery, it is necessary to form CoO formed on the surface of the core material of the negative electrode substrate. 0.02 to 0.35 mmol / cm per unit area of the core material²In order to control the discharge reserve to a more desirable value of 0.5 to 9%, the amount of CoO generated on the surface of the core material of the negative electrode substrate is set to 0.05 to 9% per unit area of the core material. 0.35 mmol / cm²It turns out that it is good to do.
[0065]
The amount of CoO generated per unit area of the core material is 0.02 mmol / cm.²If it is less than 3, the effect of suppressing the generation of the discharge reserve is extremely small, and 0.35 mmol / cm²If the discharge capacity exceeds the limit, the discharge reserve becomes too small, the discharge performance is regulated by the negative electrode, and the active material utilization rate decreases. At the same time, when the charge / discharge cycle is performed, the positive electrode (nickel electrode) becomes overcharged and γ-NiOOH There are drawbacks to create. From the above results, the amount of CoO generated per unit area of the core material was 0.02 to 0.35 mmol / cm.²Is preferably 0.05 to 0.35 mmol / cm.²More preferably,
[0066]
Although the above description has been made with reference to the hydrogen storage alloy electrode and the nickel-metal hydride storage battery using the same, the present invention is not limited to this, and can be applied to a cadmium electrode and a nickel cadmium storage battery using the same. Further, the metal element generated on the core material surface of the negative electrode substrate is not limited to Co, Ni, Cu, Ag, and Pb, and a stable transition metal can be applied to an alkaline electrolyte. The same effect can be obtained even if the metal compound formed on the core material surface of the negative electrode substrate is not only an oxide but also a hydroxide. Further, in the above embodiment, an example is shown in which the amount of transition metal generated on the surface of the core is changed only for CoO, and the amount of CoO generated per unit area of the core is 0.02 to 0.35 mmol / cm.²Is preferably 0.05 to 0.35 mmol / cm.²However, it is also possible to apply oxides and hydroxides other than Co, such as Ni, Cu, Ag, and Pb.
[0067]
In the above example, after the formation was completed, the battery was charged and discharged for 10 cycles under the charge and discharge conditions of the second and subsequent cycles, the discharge reserve amount was measured, and the preferable range of the discharge reserve amount was determined. The discharge reserve amount may be measured for a battery having a number of charge-discharge cycles including formation of several to 30 cycles.
【The invention's effect】
[0068]
The negative electrode for an alkaline storage battery according to claim 1 of the present invention is a negative electrode for an alkaline storage battery that enables control of a discharge reserve generation amount.
[0069]
The negative electrode for an alkaline storage battery according to the second aspect of the present invention is a negative electrode for an alkaline storage battery that can control the amount of discharge reserve generated in an appropriate range.
[0070]
A negative electrode for an alkaline storage battery according to a third aspect of the present invention is a negative electrode for an alkaline storage battery having the functions according to the first and second aspects of the invention and having excellent adhesion between the active material powder and the substrate.
[0071]
The alkaline storage battery according to claim 4 of the present invention is an alkaline storage battery that is excellent in a function of suppressing an increase in battery internal pressure during charging and is excellent in charge / discharge cycle performance.
[0072]
The method for manufacturing an alkaline storage battery according to claim 5 of the present invention can suppress the generation amount of the discharge reserve, is excellent in the function of suppressing the increase in the internal pressure of the battery by suppressing the generation amount of the discharge reserve, and has a charge / discharge cycle. This is a manufacturing method capable of manufacturing an alkaline storage battery having excellent performance.
[Brief description of the drawings]
FIG. 1 is a graph showing a discharge reserve generation amount of an example battery and a comparative example battery according to the present invention.
FIG. 2 is a graph showing a utilization rate of an active material of an example battery according to the present invention.
FIG. 3 shows the (001) plane of γ-NiOOH and β-Ni (OH) of the positive electrode of the battery according to the embodiment of the present invention.₂3 is a graph showing the X-ray diffraction intensity ratio of the (100) plane.
FIG. 4 is a graph showing the internal pressure of a battery when an example battery and a comparative example battery according to the present invention are overcharged.
FIG. 5 is a graph showing the charge / discharge cycle performance of a battery according to the present invention and a battery of a comparative example.

Claims (5)

A negative electrode for an alkaline storage battery in which an active material powder is supported on a substrate, wherein the substrate is selected from alkali-electrolyte-resistant transition metals and lead on a surface of a core material made of an alkali-electrolyte-resistant metal. A negative electrode for an alkaline storage battery, comprising a layer made of at least one metal. ^{2. The} negative electrode for an alkaline storage battery according to claim 1, wherein an amount of the metal layer per unit area of the core material is 0.02 mmol / cm ^{2 to} 0.35 mmol / cm ^2. 3. 3. The negative electrode for an alkaline storage battery according to claim 1, wherein the transition metal is at least one metal selected from cobalt, nickel, copper, and silver. 4. An alkaline storage battery comprising the negative electrode according to claim 1, wherein a discharge reserve amount of the negative electrode is 0.5 to 18% of a rated capacity of the battery. After forming a layer of the transition metal or lead oxide or hydroxide on the surface of the core material to produce a negative electrode carrying an active material powder, after incorporating the negative electrode into the battery, charging the battery The method according to claim 4, wherein the metal layer is formed by reducing the oxide or hydroxide of the transition metal or lead.

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