JP2005183339A - Nickel electrode for alkaline storage battery and alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve output characteristics in an alkaline storage battery using a nickel electrode for the alkaline storage battery for a positive electrode in which an positive electrode mixture containing an active material particle having nickel hydroxide as a main part and a binder is filled in a conductive core, and to suppress easily the occurrence of self discharge. <P>SOLUTION: A positive electrode mixture which contains the active material particle provided with a covered layer made of a cobalt compound of trivalence or more on the surface of a particle made mainly of nickel hydroxide, an yttrium compound particle, a nickel metal particle having a particle size of 1/5 or less of the above active material particle, and a binder is filled in the conductive core, and the alkaline storage battery nickel electrode 21 is manufactured, and then, this alkaline storage battery nickel electrode 21 is used as the positive electrode of the alkaline storage battery. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery, and a nickel electrode for an alkaline storage battery used for the positive electrode of such an alkaline storage battery, and in particular, to active material particles mainly composed of nickel hydroxide. Improved the nickel electrode for alkaline storage batteries in which a positive electrode mixture containing an adhesive is filled in a conductive core to improve the output characteristics of the alkaline storage battery and to easily suppress the occurrence of self-discharge. It is characterized by a point.

  Conventionally, in an alkaline storage battery represented by a nickel-hydrogen storage battery and a nickel-cadmium storage battery, a nickel electrode for an alkaline storage battery that generally uses an active material mainly composed of nickel hydroxide has been used as the positive electrode.

  Here, in such a nickel electrode for an alkaline storage battery, since nickel hydroxide used as an active material has low conductivity, it is generally filled with nickel powder in a cored steel rod as a core metal and sintered. A sintered nickel electrode is used in which a sintered substrate is chemically impregnated with nickel hydroxide as an active material.

  However, in the case of such a sintered nickel electrode, the bonding between the particles in the nickel powder is weak, and if the porosity in the substrate is increased, the nickel powder is likely to fall off. It is difficult to obtain an alkaline storage battery having a large capacity because it cannot be filled with a large amount of nickel hydroxide as an active material.

  In the case of the above sintered nickel electrode, since a cored bar such as a perforated steel plate is used, the packing density of the active material is generally small, and the pores of the nickel powder formed by sintering are as small as 10 μm or less. Therefore, when filling the active material, a solution impregnation method in which complicated steps are repeated for several cycles must be used, and there is a problem that the productivity is poor.

  For this reason, a paste of a positive electrode mixture prepared by adding an aqueous solution of a binder such as methylcellulose to an active material particle mainly composed of nickel hydroxide is applied to a conductive core having a large porosity such as foamed nickel, A non-sintered nickel electrode for an alkaline storage battery obtained by drying this is also used.

  Here, in the case of such a non-sintered alkaline storage battery nickel electrode, a conductive core having a porosity of 95% or more can be used, and the conductive core is filled with many active materials, A large capacity alkaline storage battery can be obtained, and the conductive material can be easily filled with an active material, thereby improving productivity.

  Further, in recent years, in alkaline storage batteries using non-sintered alkaline storage battery nickel electrodes as described above, the resistance between the active material particles is lowered to increase the utilization rate of the active material, and the output characteristics are improved. In order to improve, an active material made of nickel hydroxide has been proposed in which cadmium, zinc or cobalt is added and nickel powder or other metal powder is added as a conductive agent (for example, Patent Document 1). reference.).

  Here, when nickel powder is added as a conductive agent in this way, self-discharge tends to occur, and there is a problem that storage characteristics are deteriorated. For this reason, the surface of the nickel powder has a passive state of 10 to 30%. The thing which formed the oxide film is proposed (for example, refer patent document 2).

However, it is very difficult to appropriately form the thin passive oxide film as described above on the surface of the nickel powder, and there is a problem that self-discharge in the alkaline storage battery cannot be easily suppressed.
JP-A-5-225971 JP-A-8-241719

  The present invention relates to a nickel electrode for an alkaline storage battery in which a positive electrode mixture containing active material particles mainly composed of nickel hydroxide and a binder is filled in a conductive core, and such a nickel electrode for an alkaline storage battery as a positive electrode. It is an object to solve the above problems in the used alkaline storage battery, and improves the output characteristics of the alkaline storage battery by improving the nickel electrode for alkaline storage battery and easily suppresses the occurrence of self-discharge. The challenge is to make it possible.

  In the nickel electrode for alkaline storage batteries according to the present invention, in order to solve the above-described problems, a coating layer made of a cobalt compound having a cobalt valence of 3 or more is provided on the surface of particles mainly composed of nickel hydroxide. A positive electrode mixture containing active material particles, yttrium compound particles, nickel metal particles having a particle size of 1/5 or less of the above active material particles, and a binder is filled in the conductive core. I tried to make it.

  Here, when adding nickel metal particles having a particle size of 1/5 or less of the particle size of the active material particles to the positive electrode mixture as described above, the nickel metal particles are added to the above active material particles. It is preferable to add in the range of 6 to 30% by weight.

  Moreover, in the alkaline storage battery in this invention, the nickel electrode for alkaline storage batteries is used for the positive electrode.

  When using active material particles in which a coating layer made of a cobalt compound having a valence of cobalt of 3 or more is provided on the surface of particles mainly composed of nickel hydroxide, like the nickel electrode for alkaline storage batteries in this invention, In the case where a positive electrode mixture containing active material particles is applied as a paste to a conductive core, or when this alkaline storage battery nickel electrode is accommodated in an alkaline storage battery and an alkaline electrolyte is injected, etc. The cobalt compound does not elute unlike a coating layer made of a cobalt compound having a valence of less than three, and the coating layer forms a uniform conductive matrix on the surface of the active material particles. Sufficient conductivity is imparted, and the output characteristics of the alkaline storage battery are improved.

  Further, in the active material particles provided with a coating layer made of a cobalt compound having a cobalt valence of 3 or more in this way, the cobalt compound does not elute, so that the gap between the active material particles remains as it is. When a nickel metal particle having a particle size of 1/5 or less of the particle size of the active material particles is added, the gap between the active material particles is filled with the nickel metal particles, and the resistance between the active material particles is reduced. Greatly reduces the output characteristics of the alkaline storage battery. In addition, the nickel metal particles having a particle size of 1/5 or less of the particle size of the active material particles are used in this way, and nickel metal particles having a particle size larger than this do not fill well in the gaps between the active material particles. Because.

  In addition, when adding the nickel metal particles in this way, if the amount is small, the gap between the active material particles is not sufficiently filled with the nickel metal particles, and the output characteristics in the alkaline storage battery can be sufficiently improved. On the other hand, if the amount is too large, the amount of active material particles in the nickel electrode for alkaline storage batteries is reduced and the capacity is reduced. Therefore, the nickel metal particles are contained in an amount of 6 to 30% by weight based on the above active material particles. It is preferable to add in the range.

  In addition, when nickel metal particles are added in this manner, self-discharge is likely to occur as described above. However, as in the present invention, an active layer provided with a coating layer made of a cobalt compound having a valence of cobalt of 3 or more. When substance particles are used and an yttrium compound is added, self-discharge due to nickel metal particles is suppressed, and the storage characteristics of the alkaline storage battery are improved. Here, the reason why the self-discharge caused by the nickel metal particles is suppressed by using the active material particles provided with the coating layer made of a cobalt compound having a cobalt valence of 3 or more and adding the yttrium compound is not clear. However, when the positive electrode mixture is applied as a paste to the conductive core as described above, or when this alkaline storage battery nickel electrode is contained in an alkaline storage battery and an alkaline electrolyte is injected, etc. The cobalt compound in the coating layer does not melt, but only the yttrium compound melts, and the surface of the nickel metal particles is covered with yttrium, thereby suppressing the catalytic action of nickel, and hydrogen and oxygen are This is probably because the reaction is prevented and the occurrence of self-discharge is suppressed.

  And in the alkaline storage battery using the above nickel electrode for alkaline storage batteries as a positive electrode, sufficient output characteristics can be obtained, self-discharge can be easily suppressed, and the storage characteristics can be improved.

  Hereinafter, the alkaline storage battery according to the present invention and the alkaline storage battery using the alkaline storage battery nickel electrode as a positive electrode will be specifically described with reference to examples. In the alkaline storage battery in this example, the output characteristics and A comparative example will clarify that the storage characteristics are improved. In addition, the nickel electrode for alkaline storage batteries and alkaline storage battery in this invention are not limited to what was shown in the following Example, It can implement by changing suitably in the range which does not change the summary.

(Comparative Example A)
In Comparative Example A, in preparing a nickel electrode for an alkaline storage battery used for the positive electrode, 100 g of nickel hydroxide powder was added to 1 liter of cobalt sulfate aqueous solution in which 13.1 g of cobalt sulfate powder was dissolved, and this was stirred. Then, 1 mol / l sodium hydroxide aqueous solution was added, and stirring was continued for 1 hour while adjusting the pH to 11. Then, the precipitate was collected by filtration, washed with water, dried in vacuo, and nickel hydroxide. Active material particles in which a coating layer made of cobalt hydroxide was formed on the surface of the particles were obtained. The average particle diameter of the active material particles was 10 μm, and the valence of cobalt in the coating layer determined by oxidation-reduction titration was divalent.

  Moreover, as a result of measuring the amount of cobalt in the coating layer with respect to nickel hydroxide by the atomic absorption method for the active material particles, the amount of cobalt in the coating layer with respect to nickel hydroxide was 5% by weight.

  Then, 20 parts by weight of a 1% by weight methylcellulose aqueous solution as a binder is added to 100 parts by weight of the above active material particles, and this is kneaded to prepare a positive electrode mixture paste. The body was filled with foamed nickel, dried, and pressure-molded to produce a nickel electrode for an alkaline storage battery.

On the other hand, in preparing the negative electrode, the composition formula MmNi _3.2 Co _1.0 Al _0.7 Mn _0.1 (where Mm is La, Ce, Pr, Nd is a misch metal having a weight ratio of 25: 50: 6: 19). ) Is added to 100 parts by weight of hydrogen storage alloy particles having an average particle diameter of 50 μm, and 1.0 part by weight of polyethylene oxide as a binder and a small amount of water are added, and these are uniformly mixed to prepare a paste. The paste was uniformly applied to both surfaces of a nickel-plated punching metal current collector, dried and rolled to produce a negative electrode comprising a hydrogen storage alloy electrode.

  In addition, a nonwoven fabric made of polyolefin resin was used as the separator, and an alkaline electrolyte containing potassium hydroxide, sodium hydroxide, and lithium hydroxide was used as the alkaline electrolyte, and the design capacity was about 1000 mAh. A cylindrical nickel-hydrogen storage battery as shown in FIG. 1 was produced.

  Here, in producing the nickel-hydrogen storage battery, as shown in FIG. 1, a separator 3 is interposed between the positive electrode 1 and the negative electrode 2, and these are wound in a spiral shape in the battery can 4 And the alkaline electrolyte is poured into the battery can 4, and then sealed between the battery can 4 and the positive electrode lid 6 via an insulating packing 8, and the positive electrode 1 is connected via the positive electrode lead 5. Then, the negative electrode 2 was connected to the battery can 4 via the negative electrode lead 7, and the battery can 4 and the positive electrode cover 6 were electrically separated by the insulating packing 8. In addition, when a coil spring 10 is provided between the positive electrode lid 6 and the positive electrode external terminal 9 and the internal pressure of the battery rises abnormally, the coil spring 10 is compressed and the gas inside the battery is brought into the atmosphere. To be released.

(Comparative Example B)
In Comparative Example B, in the preparation of the nickel electrode for alkaline storage battery in Comparative Example A above, 1% by weight of methylcellulose as a binder with respect to 100 parts by weight of the active material particles having an average particle diameter of 10 μm. While adding 20 parts by weight of the aqueous solution, nickel metal particles having an average particle diameter of 0.6 μm are added at a rate of 10 parts by weight. Otherwise, the nickel-hydrogen storage battery is the same as in Comparative Example A above. Was made.

  The nickel-hydrogen storage batteries of Comparative Examples A and B produced as described above were charged at 100 mA for 16 hours under a temperature condition of 25 ° C., respectively, and then discharged to 1.0 V at 1000 mA. Each cycle was charged and discharged 5 times to activate each nickel / hydrogen storage battery.

  Next, each of the nickel / hydrogen storage batteries of Comparative Examples A and B activated in this manner is subjected to a temperature of 25 ° C. and a battery voltage reaches a maximum value at a current of 100 mA until the voltage decreases by 10 mV. The battery was charged and then allowed to stand at 55 ° C. for 12 minutes, and the voltage drop after being left in each nickel / hydrogen storage battery was examined. The results are shown in Table 1 below in terms of an index with the voltage drop after standing in the nickel-hydrogen storage battery of Comparative Example A taken as 1.

  In Table 1 below, the average particle diameter D1 (μm) of the active material particles in the positive electrode, the average particle diameter D2 (μm) of the nickel metal particles, the value of D2 / D1, the nickel metal particles relative to the active material particles The weight ratio W (% by weight) of Co and the valence of Co in the coating layer are shown together.

  As a result, compared with the nickel-hydrogen storage battery of Comparative Example A in which nickel metal particles were not added in the production of a nickel electrode for alkaline storage batteries, the nickel-hydrogen storage battery of Comparative Example B to which nickel metal particles were added was more The voltage drop after standing increased, and the storage characteristics deteriorated.

(Example 1)
In Example 1, in preparing the nickel electrode for an alkaline storage battery used for the positive electrode, in the same manner as in Comparative Example A above, a 1 liter aqueous solution of cobalt sulfate in which 13.1 g of cobalt sulfate powder was dissolved was hydroxylated. 100 g of nickel powder was added, and a 1 mol / liter aqueous sodium hydroxide solution was added while stirring. The stirring was continued for 1 hour while adjusting the pH to 11, and then the precipitate was collected by filtration. After washing with water, vacuum drying was performed to form a coating layer made of cobalt hydroxide on the surface of the nickel hydroxide particles.

  Next, in Example 1, the nickel hydroxide particles on which the coating layer made of cobalt hydroxide was formed as described above were mixed with a 5 wt% aqueous sodium hydroxide solution in a weight ratio of 1:10, This was heat-treated in air at a temperature of 75 ° C. for 8 hours, then washed with water and dried at a temperature of 65 ° C., and the cobalt valence became 3 or more on the surface of the nickel hydroxide particles. Active material particles having a coating layer made of a cobalt compound were obtained. The average particle diameter of the active material particles is 10 μm, and the valence of cobalt in the coating layer obtained by oxidation-reduction titration is 3.05. Further, in the coating layer with respect to nickel hydroxide measured by the atomic absorption method The amount of cobalt was 5% by weight.

Then, with respect to 100 parts by weight of the active material particles, 0.5 parts by weight of yttrium oxide Y ₂ O ₃ particles, 18 parts by weight of nickel metal particles having an average particle size of 0.6 μm, and 1 part by weight as a binder. % Aqueous solution of methylcellulose is added at a ratio of 20 parts by weight, and this is kneaded to prepare a paste of a positive electrode mixture. This paste is filled in foamed nickel which is a conductive core, dried, and press-molded. And the nickel electrode for alkaline storage batteries was produced.

  On the other hand, in producing the negative electrode, a negative electrode comprising a hydrogen storage alloy electrode was produced in the same manner as in Comparative Example A above.

  And as shown in FIG. 2, the negative electrode 22 which consists of said hydrogen storage alloy electrode is provided on both sides of the positive electrode 21 which consists of said nickel electrode for alkaline storage batteries through the separator 23 which consists of a nonwoven fabric made from polyolefin resin, Thus, an electrode body in which the positive electrode 21 is sandwiched between two negative electrodes 22 through a separator 23 is placed in an alkaline electrolyte 24 made of a 30 wt% aqueous potassium hydroxide solution contained in an acrylic cell container 20. The test cell of Example 1 having a design capacity of 100 mAh was produced by immersion. The electrochemical capacity of the negative electrode 22 was set to be twice or more that of the positive electrode 21.

(Example 2)
In Example 2, in the production of the nickel electrode for an alkaline storage battery in Example 1 above, nickel metal particles having an average particle diameter of 2 μm are used instead of nickel metal particles having an average particle diameter of 0.6 μm. Otherwise, the test cell of Example 2 was fabricated in the same manner as in Example 1 above.

(Comparative Example 1)
In Comparative Example 1, in the production of the nickel electrode for alkaline storage battery in Example 1 above, nickel metal particles having an average particle diameter of 30 μm are used instead of nickel metal particles having an average particle diameter of 0.6 μm. Otherwise, a test cell of Comparative Example 1 was produced in the same manner as in Example 1 above.

(Comparative Example 2)
In Comparative Example 2, in the production of the nickel electrode for an alkaline storage battery in Example 1 above, the nickel metal particles having an average particle diameter of 0.6 μm were not added, and other than that in Example 1 above. A test cell of Comparative Example 2 was produced in the same manner as in the case.

  Each of the test cells of Examples 1 and 2 and Comparative Examples 1 and 2 produced as described above was charged at 150 mA at 50 mA under a temperature condition of 25 ° C. and then 0.8 V at 50 mA. Each of the test cells was activated by repeating 10 cycles of charge and discharge.

  Next, each of the test cells of Examples 1 and 2 and Comparative Examples 1 and 2 thus activated was charged under a temperature condition of 25 ° C. with a current of 50 mA until the charge depth reached 50%. Then, discharging was performed at a current of 800 mA for 10 seconds, and voltage drop at the time of output in each test cell was examined. The results are shown in Table 2 below, with an index in which the voltage drop during output in the test cell of Example 1 is 1.

  Further, each of the test cells of Examples 1 and 2 and Comparative Examples 1 and 2 activated as described above was charged at a current of 50 mA and a charging depth of 50% under a temperature condition of 25 ° C. After charging, the battery was allowed to stand for 60 minutes, and the voltage drop after being left in each test cell was examined. The results are shown in Table 2 below, using an index with voltage drop after standing in the test cell of Example 1 as 1.

  Here, in Table 2 below, the average particle diameter D1 (μm) of the active material particles in the positive electrode, the average particle diameter D2 (μm) of the nickel metal particles, the value of D2 / D1, the nickel metal relative to the active material particles The particle weight ratio W (% by weight) and the Co valence in the coating layer are shown together.

  As a result, the test cells of Examples 1 and 2, to which nickel metal particles having an average particle diameter D2 of nickel metal particles of 1/5 or less of the average particle diameter D1 of active material particles were added, Test cell of Comparative Example 1 in which nickel metal particles having an average particle diameter D2 exceeding 1/5 of the average particle diameter D1 of active material particles were added, or Test cell of Comparative Example 2 in which no nickel metal particles were added Compared with, the voltage drop at the time of output was reduced, and the output characteristics were improved.

Further, as in each of the test cells of Examples 1 and 2 and Comparative Example 1 described above, active material particles in which a coating layer made of a cobalt compound having a cobalt valence of 3 or more was formed on the positive electrode mixture And when yttrium oxide Y ₂ O ₃ particles are added, even when nickel metal particles are added, as in the nickel-hydrogen storage battery of Comparative Example B to which nickel metal particles are added, There was no increase in voltage drop at the time point and storage characteristics were not lowered.

(Examples 3 and 4)
In Examples 3 and 4, the weight of nickel metal particles having an average particle diameter of 0.6 μm added to 100 parts by weight of the active material particles in the production of the nickel electrode for an alkaline storage battery in Example 1 above. In Example 3, 6 parts by weight of nickel metal particles having an average particle diameter of 0.6 μm were added in Example 3, and 12 parts by weight of nickel metal particles having an average particle diameter of 0.6 μm were added in Example 4. Otherwise, the test cells of Examples 3 and 4 were produced in the same manner as in Example 1 above.

  And also about each test cell of Examples 3 and 4, after being charged 150% at 50 mA under a temperature condition of 25 ° C., it was discharged to 0.8 V at 50 mA, and this was taken as one cycle. Each test cell was activated by repeating 10 cycles of charge and discharge.

  And after charging each test cell of Examples 3 and 4 thus activated under a temperature condition of 25 ° C. with a current of 50 mA until the charge depth becomes 50%, 800 mA of The voltage drop at the time of output in each test cell was examined by discharging with a current for 10 seconds, and the result was obtained as an index with the voltage drop at the time of output in the test cell of Example 1 as 1. The results are shown in Table 3 below together with 2 test cells.

  In Table 3 below, the average particle diameter D1 (μm) of the active material particles in the positive electrode, the average particle diameter D2 (μm) of the nickel metal particles, the value of D2 / D1, the weight of the nickel metal particles relative to the active material particles The ratio W (% by weight) and the Co valence in the coating layer are shown together.

  As a result, the nickel metal particles were added to each of the test cells of Examples 1, 3, and 4 in which 6% by weight or more of nickel metal particles having an average particle diameter of 0.6 μm was added to the above active material particles. Compared with the test cell of Comparative Example 2 which was not made, the voltage drop at the time of output was reduced, and the output characteristics were improved. In particular, in the test cells of Examples 1 and 4 in which nickel metal particles having an average particle diameter of 0.6 μm were added in an amount of 12 wt% or more, the voltage drop during output was further reduced, and the output characteristics were further improved. .

It is a schematic sectional drawing of the alkaline storage battery produced in the comparative examples A and B of this invention. It is a schematic sectional drawing of the test cell produced in Examples 1-4 and Comparative Examples 1 and 2 of this invention.

Explanation of symbols

1,21 Positive electrode (Nickel electrode for alkaline storage battery)
2,22 Negative electrode 24 Alkaline electrolyte

Claims (3)

  Active material particles in which a coating layer made of a cobalt compound having a cobalt valence of 3 or more is provided on the surface of particles mainly composed of nickel hydroxide, yttrium compound particles, A nickel electrode for an alkaline storage battery, wherein a positive electrode mixture containing nickel metal particles having a particle size of 1/5 or less and a binder is filled in a conductive core.   The nickel electrode for an alkaline storage battery according to claim 1, wherein the nickel metal particles are added to the positive electrode mixture in a range of 6 to 30% by weight with respect to the active material particles. Nickel electrode for alkaline storage battery.   An alkaline storage battery comprising a positive electrode, a negative electrode, and an alkaline electrolyte, wherein the alkaline storage battery uses the nickel electrode for an alkaline storage battery according to claim 1 or 2 for the positive electrode.

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