JP2008251392A - Active material for nickel positive electrode, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nickel positive electrode active material having high conductivity and high density rather than the nickel positive electrode active material obtained by a conventional method, to provide an active material for a nickel positive electrode capable of easily obtaining a nickel positive electrode inexpensively, and to provide a manufacturing method thereof. <P>SOLUTION: In a manufacturing method for crystal condensed particles of nickel hydroxide crystal and cobalt hydroxide crystal which are a new nickel positive electrode active material and has tapping density of 1.50-2.50 g/cm<SP>3</SP>and an average particle of 3.0-30.0 μm, a nickel (2+) acid solution, a cobalt (2+) acid solution, and alkaline solution are simultaneously dropped into water of a reaction container under an inert gas atmosphere while they are churned so as to neutralize these solutions in the reaction container, and generated insoluble particles are separated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The technical field of the present invention belongs to an active material for a nickel positive electrode.

  Nickel positive electrodes are not limited to nickel metal hydride batteries, but are widely used as positive electrodes for alkaline secondary batteries such as nickel cadmium batteries and nickel zinc batteries. These batteries have been increasingly required to have high capacity and long life for recent personal computers and digital cameras. Therefore, the nickel positive electrode is required to have superior high capacity characteristics, high temperature charge performance, discharge characteristics, cycle life, high energy density, etc., and higher utilization of the active material constituting the nickel positive electrode is required. It has become to.

Conventionally, nickel cathodes are known to be sintered (or sintered) or non-sintered (or paste) (Reference: Electron and Ion Functional Chemistry Series Vol. 1) All nickel-hydrogen rechargeable batteries supervised by Hideo Tamura). In the sintering method, for example, a nickel substrate is repeatedly impregnated and dried in a nickel salt bath (nickel nitrate solution, etc.) and a cobalt salt bath (cobalt nitrate solution, etc.), and then nickel hydroxide and cobalt are fixed with alkali. Thus, a positive electrode having excellent high output characteristics and a long life can be obtained. The reason is that a conductive network is formed at the crystallite level because CoOOH, which is a good conductor, is present adjacent to nickel hydroxide (Ni (OH) ₂ ), which is a nonconductor, and therefore, every corner of the active material Therefore, even if a large current is passed, the electron conduction is dispersed and excellent in high output characteristics. Further, since the Ni (OH) ₂ is less damaged by the electron conduction, the life is extended. On the other hand, since the formed crystal is soft, the capacity of the electrode plate is low because the electrode plate density is low. Further, the electrode plate manufacturing process is long, and the solution concentration in the Ni and Co salt baths is lowered, so that the yield is poor and the manufacturing cost is problematic.

Non-sintered (paste-type) nickel cathodes are produced by making conductive nickel hydroxide or nickel hydroxide and a mixture of cobalt compounds as conductive aids on the particle surface and foaming with a porosity of about 95%. It is obtained by applying to nickel and then drying / rolling. This is because it uses high-density nickel hydroxide as the active material, so the discharge capacity per volume is high, and since there is no chemical reaction in the electrode plate manufacturing process, the process control is easy and the manufacturing process is simple, so it is excellent in terms of manufacturing cost. In addition, it is superior to the sintered type in that the conductivity between particles is improved by coating the nickel hydroxide surface with a cobalt compound. On the other hand, since nickel hydroxide itself is a nonconductor, only the portion close to the surface is charged at the beginning of charging, and the portion near the center is hardly discharged at the end of discharging. Since it is in a charged state, it becomes a state where γ-type NiOOH is likely to be generated, and this causes an undesirable memory effect. In addition, during discharge, the central portion is difficult to be discharged, the discharge capacity is reduced, and the utilization rate is reduced. Further improvements are needed in this regard.
Electron and ion functional chemistry series Vol. 1 All of the nickel-hydrogen secondary batteries that are currently attracting attention Supervised by Hideo Tamura

  The present invention relates to an active material for a nickel positive electrode and a method for producing the same.

  As a result of earnest research to obtain a novel nickel positive electrode active material (and its precursor) and a nickel positive electrode that do not have the problems and disadvantages of the conventional methods described above, the present inventor has a completely new structure. A method for producing cobalt-encapsulated nickel hydroxide, which has internal conductivity, was found and the present invention was completed.

That is, the nickel positive electrode active material for nickel positive electrode according to the present invention has a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.00 to 30.00 μm. These are crystal agglomerated particles.

Further, the nickel positive electrode active material according to the present invention has a nickel hydroxide crystal having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.00 to 30.00 μm, and an average value of cobalt. It is a crystal aggregated particle with cobalt hydroxide crystals having a number of 2.00.

The active material for a nickel positive electrode according to the present invention has a tapping density of 1.50 to 2.50 g / cm ³ , an average particle size of 3.00 to 30.00 μm, and a surface coated with a cobalt compound. Crystal aggregated particles of nickel oxide crystals and cobalt hydroxide crystals.

The active material for a nickel positive electrode according to the present invention has a tapping density of 1.50 to 2.50 g / cm ³ , an average particle size of 3.00 to 30.00 μm, and an average valence of cobalt of 2.00 to 3. Crystal-aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal, the surface of which is coated with a 50-valent cobalt compound.

Furthermore, the production method according to the present invention comprises crystal aggregation of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.00 to 30.00 μm. A method for producing particles, in which a nickel (2+) acidic aqueous solution, a cobalt (2+) acidic aqueous solution, and an alkaline aqueous solution are simultaneously added to a reaction vessel water under an inert gas atmosphere while stirring to neutralize the solution. And insoluble particles formed are separated.

Moreover, the manufacturing method according to the present invention has a nickel hydroxide crystal having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.00 to 30.00 μm, and an average valence of cobalt of 2 A method for producing crystal agglomerated particles with 0.000 to 3.50 valent cobalt hydroxide crystal, wherein the tapping density is 1.50 to 2.50 g / cm ³ and the average particle size is 3.00 to 30.00 μm. This is a method characterized by air-oxidizing crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal in the presence of an alkaline aqueous solution.

Further, the production method according to the present invention comprises a nickel hydroxide crystal having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.00 to 30.00 μm, and having a surface coated with a cobalt compound. And a cobalt hydroxide crystal, wherein the tapping density is 1.50 to 2.50 g / cm ³ and the average particle size is 3.00 to 30.00 μm. In addition, a cobalt (2+) acidic aqueous solution and an alkaline water-like liquid are simultaneously dropped onto crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal to coat the surface of the crystal aggregated particle with a cobalt compound. It is a method.

The production method according to the present invention has a tapping density of 1.50 to 2.50 g / cm ³ , an average particle size of 3.00 to 30.00 μm, and an average valence of cobalt of 2.00 to 3.50. A method for producing crystal agglomerated particles of nickel hydroxide crystals and cobalt hydroxide crystals, the surface of which is coated with a valent cobalt compound, wherein the tapping density is 1.50 to 2.50 g / cm ³ and the average particle size is The method is characterized in that the crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal having a surface of 3.00 to 30.00 μm and coated with a cobalt compound are air-oxidized in the presence of an alkaline aqueous solution. is there.

  Furthermore, the present invention includes a non-sintered nickel electrode for alkaline storage batteries using the crystal aggregated particles of the present invention. Moreover, the alkaline storage battery containing the non-sintered nickel electrode for alkaline storage batteries is included.

  In the crystal aggregated particles obtained by the production method of the present invention, nickel hydroxide crystals and cobalt hydroxide crystals forming the particles are closely aggregated and become internal conductive by oxidation treatment. Therefore, by using the crystal agglomerated particles of the present invention as a non-sintered nickel electrode for an alkaline storage battery, an excellent nickel positive electrode active material having the advantageous effects of the two conventional methods (non-sintered and sintered), A nickel positive electrode can be obtained easily and inexpensively.

  The crystal agglomerated particles of the nickel hydroxide crystal and the cobalt hydroxide crystal of the present invention are the following four types (hereinafter referred to as particle I to particle IV), which will be described in order.

(Crystal agglomerated particles of nickel hydroxide crystal and cobalt hydroxide crystal, particle I)
The crystal aggregated particles according to the present invention are characterized in that nickel hydroxide crystals and cobalt hydroxide crystals are densely aggregated as constituents to form particles. Here, both nickel and cobalt have a valence of 2+. Further, depending on the production method of the present invention described below, the nickel hydroxide crystal can further dissolve other metals. Examples of the solid solution metal include magnesium, aluminum, titanium, manganese, iron, copper, and zinc. The shape of the particles can be adjusted in the range of an average particle diameter of 5.00 to 20.00 μm depending on the production method of the present invention described below, and also depends on the production method of the present invention described below. Thus, the shape can be adjusted from a substantially spherical shape to an elliptical spherical shape. Furthermore, the particle size distribution can be adjusted from a narrow range to a very wide range depending on the production method of the present invention described below. For example, an electron microscope or a particle size distribution meter can be used for easy analysis as a measuring method and measuring means for the particle size and particle size distribution of the particles.

  There is no restriction | limiting in particular in content of nickel, cobalt, or another metal, It can adjust in arbitrary ranges depending on the manufacturing method of this invention demonstrated below. Specifically, cobalt is in the range of 0.1 wt% to 35.0 wt%. Further, the content of other solid solution metal in nickel hydroxide is in the range of 0.0 wt% to 15.0 wt%. Such content analysis can be easily measured by using, for example, ICP emission analysis.

  The structural feature of the crystal aggregated particles of the present invention is that the nickel hydroxide crystal and the cobalt hydroxide crystal are uniformly aggregated (surface portion, inside) over the entire particle. It is not simply a mixture of two types of crystal particles with cobalt hydroxide crystals. The results of analysis using X-ray diffraction measurement of the crystal particles are shown in FIG. It can be seen that the nickel hydroxide crystal and the cobalt hydroxide crystal are densely and uniformly agglomerated with extremely small crystals (primary particles or even smaller particles).

  It can be easily seen from the bulk density and the tapping density that the crystal aggregated particles of the present invention are dense. Specifically, the bulk density of the crystal agglomerated particles of the present invention is 1.00 to 1.90 g / cc, and the tapping density is 1.70 to 2.40 g / cc, which is extremely high.

(Crystal Aggregated Particles of Nickel Hydroxide Crystals and Cobalt Hydroxide Crystals with an Average Valence of Cobalt of 2.01 to 2.50, Particle II)
The crystal aggregated particle II of the present invention is obtained by oxidizing the particle I described above, and is a crystal aggregated particle characterized in that the constituent cobalt is formally oxidized more than 2+. is there. The oxidation number of cobalt can be measured by the method described below. For example, the oxidation number of cobalt is determined by, for example, an iodometry method (the result of the amount of cobalt contained in the positive electrode active material by ICP emission analysis, a solution obtained by adding hydrochloric acid to the positive electrode active material powder and the potassium iodide powder, and the sodium thiosulfate solution is titrated. It is easily determined by analytical methods such as titration of sodium thiosulfate solution at the end point and a method for calculating the oxidation number of cobalt based on the amount of cobalt contained in the positive electrode active material obtained previously. Is possible. Moreover, the higher the degree of oxidation, the blacker the color of the crystal aggregated particles. Moreover, the shape (average particle diameter, particle size distribution) and density of the particles are substantially maintained by selecting the oxidation conditions described below.

  Furthermore, the crystal agglomerated particles of the nickel hydroxide crystal of the present invention and the cobalt hydroxide crystal having an average valence of cobalt of 2.01 to 2.50 are characterized by exhibiting electrical conductivity by themselves. The electrical conductivity is measured by an ordinary method known in the art. For example, a sample of 1.0 g is set on a dedicated jig, pressed at 10 kN, and measured the upper and lower resistance values to determine the sample thickness It was converted and measured as a specific resistance value per 1 cm. The specific resistance value obtained under these conditions was 100 to 1000 Ω · cm. This is presumably because a so-called three-dimensional conductive network is formed inside by the presence of oxidized cobalt hydroxide particles.

(Crystal Aggregated Particles of Nickel Hydroxide Crystals and Cobalt Hydroxide Crystals, Surface III Coated with Cobalt Compound, Particle III)
The crystal particle III of the present invention has a structure in which the surface of the particle I described above is coated with a cobalt compound. The cobalt compound to be coated here is specifically cobalt hydroxide or cobalt oxyhydroxide, and cobalt hydroxide is particularly preferable. Furthermore, it means that the cobalt compound contains a metal other than cobalt. Specific examples include yttrium, ytterbium, calcium, and magnesium.

  There is no particular limitation on the thickness of the coated cobalt compound, and the thickness of the coating can be adjusted in the range of 0.1 μm to 1.0 μm while maintaining the shape of the particles themselves by the production method of the present invention described below. is there. Further, since the surface of the particle I is coated, the particle III has a very high tap density of 1.40 to 2.40 g / cc and a bulk density of 0.80 to 1.80 g / cc.

(Crystal Aggregated Particles of Nickel Hydroxide Crystal and Cobalt Hydroxide Crystal with Particles Coated with Cobalt Compounds with an Average Valence of Cobalt of 2.01 to 3.50, Particle IV)
The particle IV of the present invention is obtained by oxidizing the particle III described above, and the constituent cobalt (internal cobalt hydroxide and / or surface cobalt compound) is formally oxidized more than 2+. It is a crystal aggregated particle characterized by being in a state. The oxidation number of cobalt can be adjusted in the range of 2.01 to 3.50 by the manufacturing method described below. The oxidation number of cobalt can be easily determined by an analysis method such as iodometry. Moreover, the higher the degree of oxidation, the blacker the color of the crystal aggregated particles. Moreover, the shape (average particle diameter, particle size distribution) and density of the particles are substantially maintained by selecting the oxidation conditions described below. For example, the tap density is 1.50 to 2.50 g / cc, and the bulk density is 0.80 to 1.80 g / cc, which is extremely high.

  Furthermore, the particles IV of the present invention are distinguished by a large electrical conductivity. The electrical conductivity is measured by a conventional method known in the art, for example, 1.0 g of a sample is set on a dedicated jig, pressed at 10 kN, the upper and lower resistance values are measured, and the sample thickness is 1 cm. It was converted and measured as a specific resistance value per unit. The specific resistance value obtained under these conditions was 2.0 to 20.0 Ω · cm. This is presumably because a so-called three-dimensional conductive network is formed inside due to the conductivity through oxidized surface-coated cobalt and the presence of oxidized cobalt hydroxide particles. The presence of such a plurality of conductive networks means that both the advantages of both the conventional non-fired type and the fired type are combined.

(Production method)
A method for producing the particles I to IV according to the present invention will be described below.

(Method for producing particle I)
The method for producing particles I of the present invention is to neutralize and form precipitated particles by simultaneously dropping nickel (2+) acidic aqueous solution, cobalt (2+) acidic aqueous solution and alkaline aqueous solution while stirring into water in the reaction vessel. It is characterized by making it.

  For example, when a reaction tank having a reaction volume of 15 L is used, the reaction atmosphere is not particularly limited, but it is preferably performed in an inert gas atmosphere so that cobalt (2+) is not oxidized. Examples of the inert gas include nitrogen gas, helium gas, neon gas, argon gas, krypton gas, xenon gas, and radon gas. The inert gas is preferably introduced into the reaction vessel or into the reaction water. In the present invention, nitrogen gas is preferably blown into the reaction vessel, and the gas flow rate is preferably in the range of 1.0 to 5.0 L / min.

  The nickel salt for preparing the nickel (2+) acidic aqueous solution is not particularly limited, and examples thereof include nickel sulfate, nickel chloride, and nickel nitrate. In the present invention, it is preferable to use nickel sulfate. Similarly, the cobalt salt for preparing the cobalt (2+) acidic aqueous solution is not particularly limited, and examples thereof include cobalt sulfate, cobalt chloride, and cobalt nitrate. In the present invention, the use of cobalt sulfate is preferred.

  Furthermore, in order to make it a solid solution in a nickel hydroxide, the salt of another metal ion can be mixed with the above nickel (2+) acidic aqueous solution and used. Examples of other metal salts include magnesium sulfate, aluminum sulfate, titanium sulfate, manganese sulfate, iron sulfate, copper sulfate, and zinc sulfate.

  The concentration of the acidic aqueous solution of nickel (2+) acidic solution, cobalt (2+) acidic aqueous solution, and other metal ions for dissolving in nickel hydroxide is not particularly limited, and reaction conditions (nickel and cobalt, or other metals) Content, reaction vessel size, reaction temperature, amount of reaction solution, degree of stirring). Specifically, when a reaction tank with a reaction volume of 15 L is used, these concentrations are preferably in the range of 0.1 to 2.0 mol / L. In particular, the concentration of acidic aqueous solution of nickel (2+), cobalt (2+) acidic aqueous solution, and other metal ions for dissolving in nickel hydroxide is 0.7 to 2.0 mol / L, 0.7 to It is preferable that it is the range of 2.0 mol / L and 0.1-2.0 mol / L.

  There is no restriction | limiting in particular as alkaline aqueous solution, The aqueous solution of hydroxides, such as lithium, sodium, potassium, can be used preferably. Moreover, there is no restriction | limiting in particular also about a use density | concentration, It is possible to select suitably for hydroxide production | generation and preferable pH maintenance. In the present invention, specifically, in the case of sodium hydroxide, the range of 1.5 to 15.0 mol / L is preferable. The pH of the reaction solution is preferably maintained in the range of 10.0 to 13.5.

  There is no particular limitation on the method of reacting the nickel (2+) acidic aqueous solution (optionally a mixed aqueous solution with other metal ions that are solid-dissolved in nickel hydroxide), the cobalt (2+) acidic aqueous solution, and the alkaline aqueous solution. Preferably, each solution is dropped separately into the stirred water in the reaction vessel. Each of the dropped solutions is sufficiently stirred in the reaction vessel, and a precipitate is formed along with the neutralization reaction. The degree of stirring is preferably such that each solution dropped on the upper part of the reaction vessel is diffused over the entire solution (not only in the radial direction but also in the vertical direction) in a sufficiently short time. Specifically, it is particularly preferable to use a propeller-shaped stirring device at 1200 rotation speed. The reaction temperature is not particularly limited but is preferably 20 to 55 ° C. Further, the dropping flow rate is not particularly limited, but in the case of nickel (2+) acidic aqueous solution, it is preferably 3.0 to 50.0 ml / min, and cobalt (2+) acidic aqueous solution (in some cases, solid solution in nickel hydroxide). In the case of a mixed aqueous solution with other metal ions, it is preferably 0.3 to 10.0 ml / min.

  The particle size and particle size distribution of the precipitated particles can be adjusted by appropriately changing the pH of the reaction solution, the dropping flow rate of the raw material liquid, and the rotation speed. Specifically, the average particle size can be adjusted small by increasing the pH of the reaction solution, and the average particle size can be adjusted large by decreasing the pH of the reaction solution. The particle size distribution can be adjusted by appropriately changing the pH of the reaction solution, the dropping flow rate of the raw material liquid, and the rotation speed. Specifically, the particle size distribution can be widely adjusted by reducing the rotation speed, and the particle size distribution can be adjusted narrowly by increasing the rotation speed.

  The reaction may be batch or continuous using an overflow pipe. In the present invention, a continuous type using an overflow pipe is preferred. As the reaction tank provided with the overflow pipe, for example, the apparatus described in JP-A-2-6340 can be preferably used. After the reaction described above proceeds, it is possible to continuously take out the precipitated particles generated from the overflow pipe provided in the upper part of the reaction tank.

  The precipitated particles taken out from the overflow pipe can be separated from the reaction solution by decantation or ordinary filtration means. Furthermore, it is possible to dry by a normal drying method. The obtained particles I can be used as they are. In order to prepare an appropriate particle size and distribution, separation and classification can be performed using known means.

  The metal ions that can be used in the method for producing the particle I of the present invention are not limited to nickel, cobalt, and other metals that dissolve in nickel hydroxide described above. Usable metals include magnesium, aluminum, titanium, manganese, iron, copper, and zinc. By using these metal ion aqueous solutions, crystal aggregated particles of these metal hydroxide crystals can be produced.

(Method for producing particle II)
The manufacturing method of the particle | grains II of this invention is implementing the well-known oxidation method which can oxidize cobalt hydroxide and oxidize to highly oxidized cobalt hydroxide by using the particle | grains I of this invention as a starting material. Although there is no restriction | limiting in particular about the said well-known oxidation method here, For example, the oxidation based on Unexamined-Japanese-Patent No. 2002-255562 is preferable.

  More specifically, it is possible to produce the particles II by spraying the particles I with an alkaline aqueous solution into a dry powder and oxidizing them with air. Although there is no restriction | limiting in particular as alkaline aqueous solution, It is preferable to air-oxidize using the aqueous solution of the hydroxide of lithium, sodium, and potassium. The oxidation reaction can be traced based on the change in the color of the particles or the measurement result of the oxidation number to know completion. The change in color changes from green to gray. Further, a part of the particles in the middle of the reaction is taken out, and the oxidation number of the cobalt is monitored by an iodometry method. When the oxidation number changes from 2.00 to 2.50, the completion of the oxidation reaction can be confirmed. The obtained particles II can be washed with water and dried without any particular treatment after the oxidation reaction.

(Method for producing particle III)
The particle III of the present invention can be produced by coating the surface of the particle I of the present invention with a cobalt compound by a conventionally known method. Here, the conventional method for coating the surface with a cobalt compound is not particularly limited, but it is preferably carried out according to the methods described in JP-A-10-012236, JP-A-10-012237, and the like.

  Specifically, a method in which a cobalt (2+) acidic aqueous solution and an alkaline water-like liquid are simultaneously dropped into a dispersion of particles I or particles II to coat the surface of the crystal aggregated particles with a cobalt compound is preferable. Here, the dispersion liquid of the particles I or II is preferably about 10.0 L of water with respect to 1.0 kg of the particles. The cobalt (2+) acidic aqueous solution preferably has a concentration of 90 g / L of cobalt sulfate (2+), cobalt nitrate (2+), and cobalt chloride (2+) (particularly cobalt sulfate is preferred).

  Completion of the surface coating of the cobalt compound can be confirmed by monitoring SEM images before and after the reaction.

(Method for producing particle IV)
The particle IV of the present invention is to carry out a known oxidation method in which the cobalt hydroxide is oxidized in the air and oxidized into highly oxidized cobalt hydroxide using the particle III of the present invention as a starting material. Although there is no restriction | limiting in particular about the said well-known oxidation method here, For example, the oxidation based on Unexamined-Japanese-Patent No. 2002-255562 is preferable.

  More specifically, the particles IV can be produced by spraying an aqueous alkaline solution into a dry powder and oxidizing the particles III with air. Although there is no restriction | limiting in particular as alkaline aqueous solution, It is preferable to use the aqueous solution of hydroxides, such as lithium, sodium, and potassium. The oxidation reaction can be traced based on the change in the color of the particles or the measurement result of the oxidation number to know completion. The change in color changes from green to gray. A part of the particles in the middle of the reaction is taken out, and the oxidation number of the cobalt is monitored by an iodometry method. When the oxidation number changes from 2.01 to 3.50, the end of the oxidation reaction can be confirmed. The obtained particles IV can be washed with water and dried without any particular treatment after the oxidation reaction.

(Nickel positive electrode)
The particles I to IV of the present invention can be used as a positive electrode material, and a nickel positive electrode for an alkaline storage battery and further an alkaline storage battery can be produced by combining generally known methods. Specifically, JP-A No. 2001-052695 (contract), Japanese Patent No. 3808193, [Technology of the latest secondary battery material (supervised by Zenpachi Okumi) CMC (published in 1999-09-08)] and the like are preferably applicable.

  Specific examples of the present invention will be described below. The obtained samples were analyzed as follows.

(X-ray diffraction)
The sample was used as is. The measuring apparatus and conditions were RINT2200 (Cu-Kα) manufactured by Rigaku Corporation and followed the operation procedure manual.

(Tapping density)
The mass of the 20 mL cell was measured [A], and the sample was naturally dropped into the cell with a 48 mesh sieve and filled. The weight [B] and filling volume [D] of the cell after tapping 200 times were measured using “TAPDENSER KYT3000” manufactured by Seishin Enterprise Co., Ltd. with a 4 cm spacer. The following formula was used for calculation.

Tap density = (B−A) / D g / cc
(Average particle size, particle size distribution)
The measuring device used was LA-910 manufactured by HORIBA, Ltd., and the measurement conditions followed the operation procedure manual. The measurement result was expressed as an average particle diameter.

(electronic microscope)
The measuring apparatus used was S-2400 manufactured by Hitachi, Ltd., and the measurement conditions were in accordance with the operation procedure manual. The measurement results were expressed as SEM images.

(Composition analysis)
The measuring device used was CIROS-120 EOP manufactured by Rigaku Corporation, and the measuring conditions followed the operating procedure. The measurement results were expressed as the main component content.

Example 1 Production of Particle I (a) 13 L of distilled water was added to a 15 L cylindrical reaction tank (material SUS304) having an effective volume of 15 L equipped with a stirring device equipped with one 70φ propeller type stirring blade and an overflow pipe. I put it in. 900 g of ammonium sulfate powder (special grade reagent) was added to the water in the reaction vessel and stirred to dissolve. Subsequently, 30% sodium hydroxide solution (special grade reagent) was added to adjust the pH to 12.8. The temperature of this solution was maintained at 45 ° C. with an electric heater provided outside the reaction vessel. The solution in the reaction vessel was stirred at a constant speed (1200 rpm) with a stirring device. Further, nitrogen gas was continuously supplied to the reaction tank at a flow rate of 1.0 L / min to maintain the atmosphere in the reaction tank under a nitrogen atmosphere.

  (B) A nickel sulfate solution, a zinc sulfate solution and a nickel zinc mixed solution, and a cobalt sulfate solution and an ammonium sulfate solution were prepared as follows. Nickel sulfate (special grade reagent) was dissolved in distilled water to prepare a nickel sulfate solution to a concentration of 1.8 mol / L. A zinc sulfate solution was prepared by dissolving zinc sulfate (special grade reagent) in distilled water to a concentration of 1.3 mol / L. These liquids were mixed so that Ni: Zn = 93: 7 (molar ratio) to prepare a nickel zinc mixed liquid.

  Cobalt sulfate solution was prepared by dissolving cobalt sulfate (special grade reagent) in distilled water to a concentration of 1.5 mol / L.

  Further, ammonium sulfate (special grade reagent) was dissolved in distilled water to prepare an ammonium sulfate solution so as to have a concentration of 6.0 mol / L.

  (C) The reaction was carried out as follows.

  From the upper part of the reaction tank of (a), the nickel zinc mixed liquid of (b) was continuously supplied to the liquid level in the reaction tank at a constant rate of 10 cc / min. Moreover, the cobalt sulfate liquid of (b) was continuously supplied to the liquid level in the tank from the upper part of the reaction tank different from the supply part of the nickel zinc mixed liquid of (b) at a constant rate of 2.8 cc / min. Furthermore, the ammonium sulfate solution of (b) was continuously supplied to the liquid level in the tank from the upper part of the reaction tank different from the supply part of each liquid of (b) at a constant rate of 4 cc / min. During the reaction, 30% sodium hydroxide was intermittently added to maintain the pH of the solution in the reaction vessel at 12.8.

  It was confirmed from the moving average of the average particle size that a particulate precipitate was formed with the supply of each of the liquids above, and the reaction vessel was in a steady state after about 72 hours. Thereafter, the precipitate discharged from the overflow pipe was continuously collected for 24 hours. The obtained precipitate was washed twice with distilled water, and then separated by filtration with Nutsche. The obtained precipitate was dried at 65 ° C. for 15 hours to obtain a dry powder. The color of the precipitate was green. The obtained precipitate is designated as Sample 1.

  The analysis results of Sample 1 are summarized below.

(X-ray diffraction) FIG.
(Tapping density) 2.04 g / cc
(Average particle size, particle size distribution) 9.1 μm
(Electron microscope) Fig. 2
From this analysis result, it was found that the obtained precipitate was crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal.

Example 2 Production of Particles II 7.0 kg of the precipitate obtained in Example 1 was placed in a stirring mixer (Kawata Co., Ltd. Model SMV-20), and the main stirring shaft was rotated at 200 rpm. Thereafter, the jacket of the stirring mixer was heated to set the powder (precipitation) temperature to 100 ° C., and 700 ml of a 48% sodium hydroxide aqueous solution was sprayed onto the powder at 500 ml / min. After spraying, the mixture was kept at 100 ° C. for 30 minutes and then cooled to room temperature. The powder was taken out, washed twice with pure water, dehydrated and dried (100 ° C., 3 hours) to obtain gray crystal aggregated particles (referred to as sample 2).

  The analysis results of Sample 2 are summarized below.

(Tapping density) 2.02 g / cc
(Average particle size, particle size distribution) 9.5 μm
(Cobalt average valence) 2.33 valence From this analysis result, the resulting precipitate is a crystal agglomeration of nickel hydroxide crystals and cobalt hydroxide crystals having an average valence of cobalt of 2.01 to 2.40. It turned out to be a particle.

(Example 3) Production of Particle III 100 g of the precipitated particles obtained in Example 2 were placed in a 3 L reactor equipped with a stirrer. While stirring (100 rpm), 700 ml of water, 200 ml of 6 mol / L ammonium sulfate solution, and 30% aqueous sodium hydroxide solution were gently added to the reaction vessel. The pH of the reaction vessel was 9.0. Into this, 40 ml of 2 mol / L cobalt sulfate aqueous solution and 10 mol / L sodium hydroxide aqueous solution were added while maintaining the pH at 9.0. Thereafter, stirring was continued for 30 minutes. Thereafter, a 30% aqueous sodium hydroxide solution was added to adjust the pH to 12.5, and the pH was maintained for 1 hour. The resulting precipitate was filtered, dehydrated and separated, and dried with a shelf dryer to obtain dark green crystal aggregated particles (referred to as sample 3).

  The analysis results of Sample 3 are summarized below.

(Tapping density) 2.06 g / cc
(Average particle size, particle size distribution) 10.5 μm
(Cobalt average valence) 2.07 value From this analysis result, it was found that the obtained precipitate was crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal, the surface of which was coated with a cobalt compound. .

(Example 4) Production of Particle VI 7.0 kg of the crystal aggregated particles obtained in Example 3 were put into a stirring mixer (Kawata Co., Ltd. Model SMV-20), and the main stirring shaft was rotated at 200 rpm. Thereafter, the jacket of the stirring mixer was heated to set the powder (precipitation) temperature to 100 ° C., and 700 ml of a 48% sodium hydroxide aqueous solution was sprayed onto the powder at 500 ml / min. After spraying, the mixture was kept at 100 ° C. for 30 minutes and then cooled to room temperature. The powder was taken out and washed twice with pure water. Post-dehydration and drying (100 ° C., 3 hours) were performed to obtain gray crystal aggregated particles (referred to as sample 4).

  The analysis results of Sample 4 are summarized below.

(Tapping density) 2.09 g / cc
(Average particle size, particle size distribution) 10.1 μm
(Cobalt average valence) 3.01 valence From this analysis result, the resulting precipitate was a nickel hydroxide crystal whose surface was coated with a cobalt compound having an average valence of cobalt of 2.01 to 3.50. It was found to be crystal agglomerated particles of cobalt hydroxide and cobalt hydroxide crystals.

  By using the nickel positive electrode active material obtained by the production method of the present invention, it is possible to easily and inexpensively obtain a nickel positive electrode with higher conductivity and higher density than before.

FIG. 1 shows the XRD pattern of Sample 1. FIG. 2 shows an SEM image of Sample 1.

Claims (8)

Crystal aggregated particles of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm. Nickel hydroxide crystal having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm, and water having an average valence of cobalt of 2.00 to 3.00 Crystal aggregated particles with cobalt oxide crystals. Crystal aggregation of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.0 to 30.0 μm and having a surface coated with a cobalt compound particle. The surface is coated with a cobalt compound having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm, and an average valence of cobalt of 2.00 to 3.00. Crystal aggregated particles of nickel hydroxide crystals and cobalt hydroxide crystals. A method for producing crystal agglomerated particles of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.0 to 30.0 μm,
While stirring, the aqueous solution of nickel (2+), cobalt (2+), and aqueous alkaline solution are simultaneously added to the reaction vessel in an inert gas atmosphere while stirring to neutralize the resulting insoluble particles. A method characterized by separating. A nickel hydroxide crystal having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm, and a cobalt hydroxide crystal having an average valence of cobalt of 2.00 A method for producing crystal agglomerated particles of
Crystal aggregated particles of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm are made alkaline in the presence of an oxidizing agent. Dispersing in an aqueous solution and oxidizing. Crystal aggregation of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.0 to 30.0 μm and having a surface coated with a cobalt compound A method for producing particles comprising:
In the aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal dispersed in water and having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.0 to 30.0 μm, A method in which a cobalt (2+) acidic aqueous solution and an alkaline water-like liquid are simultaneously dropped to coat the surface of the crystal aggregated particles with a cobalt compound. The surface is coated with a cobalt compound having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle diameter of 3.0 to 30.0 μm, and an average valence of cobalt of 2.00 to 3.50. A method for producing crystal aggregated particles of nickel hydroxide crystal and cobalt hydroxide crystal,
Crystal aggregation of nickel hydroxide crystals and cobalt hydroxide crystals having a tapping density of 1.50 to 2.50 g / cm ³ and an average particle size of 3.0 to 30.0 μm and having a surface coated with a cobalt compound A method characterized in that particles are oxidized by air in the presence of an aqueous alkaline solution.