JPH1081520A - Manganese-cobalt-based double hydroxide, its production and raw material for anode active material for lithium secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a manganese-cobalt-based double hydroxide having spherical shape and capable of providing a raw material for an anode active material for a lithium secondary cell having improved initial service capacity and retention of discharge by aging a precipitate obtained by adding a chelating agent to an aqueous solution of a mixed salt of Mn and Co salts and further performing an alkaline hydrolysis thereof. SOLUTION: This manganese-cobalt-based double hydroxide in produced by adding 0.2-4.0mol chelating agent having chelating ability at Mn and Co metal ions, and 1.1-3.0mol alkali based on 1mol Mn and Co salts to a mixed salt aqueous solution containing 0.5-3.5mol/L Mn and Co slats, performing an alkaline hydrolysis thereof a 10-100 deg.C for 1-72hr to form a precipitate, aging the precipitate to provide the objective manganese-cobalt-based double hydroxide having <=3 particle distribution (V95 -V5 )/V50 measured by a laser method and (0.01:0.99) to (0.99:0.01) atomic ratio of Mn to Co (Mn:Co).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Mn-Co composite hydroxide, a method for producing the same, and a raw material for a positive electrode active material for a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
With the rapid progress of cordless technology, lithium secondary batteries have been put to practical use as power supplies for small electronic devices. Mizushima et al. Reported in 1980 that this lithium secondary battery was useful as a positive electrode active material for lithium cobaltate secondary batteries [“Material Research Brain” vol.
15, P783-789 (1980)], research and development on lithium-based composite oxides have been actively promoted, and many proposals have been made so far.

[0003] These are, for example, Li _1-a NiO ₂ (where 0 ≦
a ≦ 1) (US Pat. No. 4,302,518), Li _b Ni
_2-b O ₂ and LiNi _1-d Co _d O ₂ (provided that 0.84 ≦ b ≦ 1.22, 0.
09 ≦ d ≦ 0.5) (JP-A-2-40861), LinNimCo _1-m
O ₂ (JP-A-63-299056, JP-A-1-120765,
JP-A-1-94364, JP-A-5-290890, JP-A-Hei.
No. 6-275274, JP-A-7-142056) and the like, which are composite oxides mainly composed of lithium and a transition metal. Among the above compounds, lithium cobalt oxide has been studied from the earliest because it is relatively easy to synthesize. However, there is a problem that cobalt (Co) as a raw material is expensive and is rarely produced as a resource. Nickel (Ni) instead of Co to solve this problem
And lithium oxides using Mn have been studied, but have not been put to practical use yet.

[0004]

The synthesis of lithium nickelate is very difficult and has not been manufactured on an industrial level. To solve this problem, lithium nickelate Ni
Have been proposed in which a part of is replaced by Mn. However, since these oxides are synthesized at low temperatures, Mn
The problem is that the solution reaction between Co and Co is not so good.

Accordingly, an object of the present invention is to provide a Mn-Co-based composite hydroxide useful as a raw material of a Li-Mn-Co-based composite oxide used for a positive electrode of a lithium secondary battery or the like, and a method for producing the same. It is in.

[0006]

Under such circumstances, the present inventors have conducted intensive studies, and as a result, completed the present invention.

That is, the present invention relates to a crystal particle of a Mn—Co-based composite hydroxide formed in a solid solution state and / or a coprecipitation state of Mn and Co, and the crystal particle is measured by a laser method. cathode active material for a lithium secondary battery according to the particle size distribution _{(V 95 -V 5) / Mn} -Co -based V ₅₀ value is equal to or more than 3 composite hydroxide and active ingredient which was determined by the law This is to provide raw materials.

Further, the present invention provides a method for continuously performing a precipitation-forming reaction by alkali hydrolysis in the presence of a chelating agent having a complexing power for Mn and Co metal ions in an aqueous solution of a mixed salt of Mn and Co salts. And then ripening the precipitate to provide a method for producing a Mn—Co-based composite hydroxide.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The Mn-Co composite hydroxide of the present invention is a Mn-Co composite hydroxide formed in a solid solution and / or coprecipitation state of Mn and Co. Mn and Co formed in a solid solution and / or coprecipitation state include, for example, Mn and Co.
And Co are not simply mixed but Mn and Co are uniformly co-precipitated and mixed. When Mn or Co that does not form a solid solution or coprecipitate exists alone, X
Line diffraction confirms the peak of Mn or Co hydroxide as an impurity generated due to the presence of Mn or Co. However, the Mn—Co-based composite hydroxide of the present invention has very few such impurities, and substantially has no such peaks in powder X-ray diffraction.

Further, crystal grains of Mn-Co-based composite hydroxide of the present invention, the particle size distribution _{(V 95 -V 5) / V} 50 values obtained in the measurement method by laser method is in the range of 3 or less Yes,
In particular, it is preferably in the range of 0.5 to 2. The average particle diameter of the crystal particles is preferably 1 to 50 μm, and more preferably 5 to 20 μm. Those outside the above range have a wide range of particle diameters, and are not very preferable as raw materials for lithium secondary batteries. Also,
V ₉₅ , V ₅₀ and V ₅ represent 95% by volume, 50% by volume and 5% by volume, respectively. The crystal particles are substantially spherical particles as described above, and are, for example, cocoon-shaped or dumpling-shaped particles in which some spherical or elliptical particles and some spherical particles are combined.

The atomic ratio Mn: Co of the Mn—Co-based composite hydroxide of the present invention is 0.01: 0.99 to 0.99: 0.
01, preferably 0.1: 0.9 to 0.9: 0.1.

The method for producing a Mn—Co-based composite hydroxide according to the present invention is directed to a method for producing an Mn—Co complex hydroxide using a chelating agent having a complexing power for Mn and Co metal ions in a mixed salt aqueous solution of a Mn salt and a Co salt. The precipitation-forming reaction by hydrolysis is continuously performed, and the precipitation product is ripened as necessary and sufficiently ripened, for example, retained for at least 3 hours to progress the ripening reaction.

The Mn salt used in the production method of the present invention is
There is no particular limitation as long as it is soluble in water, but examples thereof include easily water-soluble mineral salts such as nickel sulfate, nickel nitrate, and nickel chloride. The Co salt is not particularly limited as long as it dissolves in water similarly to the Mn salt, and examples thereof include water-soluble mineral salts such as manganese sulfate, manganese nitrate, and manganese chloride. Mn salt and C
The o salt is preferably used in the reaction in an aqueous solution concentration of about 0.5 to 3.5 mol / L in a practical range.

Examples of chelating agents having a complexing power for these metal ions include hydrazine, triethanolamine, glycine, alanine, asparagine, iminodiacetic acid, glutamic acid, ethylenediamine, and the like.
Aminocarboxylic acids such as ethylenediaminetetraacetic acid and salts thereof; acetic acid, lactic acid, oxalic acid, malonic acid, malic acid,
Oxycarboxylic acids such as tartaric acid, citric acid, salicylic acid and thioglycolic acid and salts thereof or ammonia. Ammonia is not particularly limited as long as it can supply ammonium ions.Examples thereof include aqueous solutions of ammonium salts such as ammonium nitrate, ammonium sulfate, and ammonium chloride, aqueous ammonia, and ammonia gas. is there.

The above-mentioned chelating agents such as aminocarboxylic acid, oxycarboxylic acid and ammonia may be used alone or in combination of two or more. The compounding amount is 0.2 to 1 mol of Mn salt and Co salt. A range of 4.0 moles is preferred. The method of blending the chelating agent is not particularly limited, and may be used alone,
Any predetermined ratio of the o salt aqueous solution may be mixed in advance and added. If it is less than 0.2 mol, particle growth is not sufficient, and
If it is 0.4 mol or more, it is not preferable in terms of economy.

Examples of the alkali used for the alkali hydrolysis include aqueous solutions of caustic alkali such as sodium hydroxide and potassium hydroxide. Of these, sodium hydroxide is preferred. The amount of the alkali added was Mn salt and Co.
It is 1.1 to 3.0 mol per mol of the salt. If the amount is less than 1.1 mol, unreacted Mn salt and Co salt are generated, which is not preferable.

The reaction operation is not particularly limited. For example, the pH of the continuously added reaction solution is adjusted to 9-1.
A method in which the reaction is carried out by keeping the solution at a constant value in the range of 2 for at least 3 hours. At this time, the reaction solution may be subjected to an aging reaction in the next container once overflowed.

As another method, the volume of the reaction solution is controlled to a constant amount except for the reaction medium solution without overflowing the reaction system solution containing the reaction product by continuously adding the reaction solution. This is a method of reacting while reacting. According to this method, the particles of the Mn-Co composite hydroxide formed in the reaction vessel continuously grow and increase, so that the stirring of the reaction system becomes gradually difficult. It is preferable to terminate the reaction.

The reaction conditions are preferably set so that the slurry concentration of the reaction system is at least 70 g / L or more. If the concentration is lower than this, particle growth becomes extremely slow, which is not preferable.

Each reaction solution to be added may be continuously added at once, or may be a multistage system in which the reaction solution is divided into several portions and dropped in multiple stages.

The reaction temperature is usually 10 to 100 ° C., preferably 20 to 80 ° C., and the reaction time is about 1 to 72 hours.

[0022]

The Mn-Co-based composite hydroxide of the present invention comprises:
It has a substantially spherical particle form and is useful as a raw material for a positive electrode active material for a lithium secondary battery.
A lithium secondary battery using a positive electrode active material with an n-Co-based composite oxide as an active ingredient has excellent characteristics such as an initial discharge capacity and a discharge retention rate, which have not been seen before.

[0023]

Next, the present invention will be described in detail with reference to examples, but this is merely an example and does not limit the present invention.

Example 1 A 1 L beaker was previously filled with 200 ml of water, and 1.6 ml of water was added thereto.
_{l / L MnSO 4 · 6H 2} O and 0.4 mol / L CoSO ₄ of
· 5H ₂ O of the mixture 1200 ml, added dropwise to ammonia solution 400ml of 14.8mol / L as NaOH solution 800ml and complexing agents of 6 mol / L, was kept at 50 ° C. while adjusting the pH to 11, 9 hours The mixture was aged with stirring. During this time, the amount of liquid in the system was controlled by the overflow method, and a certain amount of the reaction liquid was discharged. Next, the crystals after the filtration were subjected to repulping washing, and the washing effect was confirmed by a conductivity meter. This crystal is composed of Mn and Co
Was formed in a solid solution and / or coprecipitation state, and had a composition of Mn: Co at a molar ratio of 0.8: 0.2. When the particle size distribution of the crystals was measured by a laser method, (V ₉₅ −
The V ₅ ) / V ₅₀ value was 1.6 and the average particle size was 16 μm.

Example 2 A 1 L beaker was previously filled with 200 ml of water, and 1.8 mol of water was added thereto.
/ L MnSO ₄ .H ₂ O and 0.2 mol / L CoSO _4.
1200 ml of a mixture of 5H ₂ O, 800 ml of a 6 mol / L NaOH solution, and 40 mol of a 1 mol / L glycine solution as a complexing agent
0 ml was added dropwise, and the pH was adjusted to 10 to 70
The solution was kept at ℃ and stirred and aged for 9 hours. During this time, the amount of the liquid in the system was controlled by the overflow method, and a certain amount of the reaction liquid was discharged. Next, the crystals after the filtration were subjected to repulping washing, and the washing effect was confirmed by a conductivity meter. This crystal is a eutectic formed in a solid solution and / or coprecipitation state of Mn and Co, and has a composition of Mn:
The molar ratio of Co was 0.9: 0.1. When the particle size distribution of the crystals was measured by a laser method, (V ₉₅ -V ₅₎ /
The V ₅₀ value was 2.2 and the average particle size was 12 μm.

Example 3 A 500 ml beaker was previously filled with 250 ml of water.
0.4mol / L CoS of MnSO ₄ · 6H ₂ O and 1.8mol / L of
O ₄ · 5H ₂ O mixture 2L, 1 mol / L of malic acid solution 6 as NaOH solution 1300ml and complexing agents of 6 mol / L of
Add 70 ml dropwise and adjust the pH to 10 to 7
The mixture was kept at 0 ° C. and aged for 15 hours with stirring. During this time, in order to control the amount of liquid in the system, the slurry concentration was increased while only the reaction liquid was removed by filtration under reduced pressure. Next, the crystals after the filtration were subjected to repulping washing, and the washing effect was confirmed by a conductivity meter. The crystal after drying is a eutectic of Mn and Co formed in a solid solution and / or coprecipitation state, and the composition is in a molar ratio of Mn: Co.
0.2: 0.8. Measurement of the particle size distribution of the crystal by laser method, the average particle diameter (V ₉₅ -V ₅₎ / V ₅₀ value 1.5 was 9 .mu.m.

Claims (6)

[Claims] 1. A crystal particle of a Mn—Co-based composite hydroxide formed in a solid solution state and / or a coprecipitation state of Mn and Co, and the crystal particle is obtained by a measuring method by a laser method. Mn-Co-based composite hydroxide wherein the particle size distribution _{(V 95 -V 5) / V} 50 is 3 or less. 2. The atomic ratio of Mn to Co, Mn: Co,
The Mn-Co-based composite hydroxide according to claim 1, wherein the ratio is in the range of 0.01: 0.99 to 0.99: 0.01. 3. M in a mixed salt aqueous solution of a Mn salt and a Co salt.
Mn- characterized by continuously performing a precipitation-forming reaction by alkaline hydrolysis in the presence of a chelating agent having a complexing power for metal ions of n and Co, and then aging the precipitate. A method for producing a Co-based composite hydroxide. 4. The method for producing a Mn—Co-based composite hydroxide according to claim 3, wherein the continuous reaction is performed in a multistage manner. 5. The method according to claim 1, wherein the chelating agent is at least one selected from aminocarboxylic acids, oxycarboxylic acids and ammonia.
Mn-Co according to claim 3 or 4, which is a species or two or more species.
For producing a composite hydroxide. 6. A raw material for a positive electrode active material for a lithium secondary battery, comprising the Mn—Co-based composite hydroxide according to claim 1 or 2 as an active ingredient.