JP2012256435A - Nickel manganese composite hydroxide particle and production method thereof, positive electrode active material for nonaqueous electrolyte secondary battery and production method thereof, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nickel manganese composite hydroxide particles having high surface Mn/Ni ratio and high grain size uniformity in which dispersibility of the active material in a positive electrode can be improved, and to provide a production method thereof.SOLUTION: When producing a nickel manganese composite hydroxide by crystallization reaction, nucleation is performed by controlling the pH value of an aqueous solution for nucleation containing a metal compound containing nickel and a metal compound containing manganese and an ammonium ion supply body to be 12.0-13.4 measured on the basis of a liquid temperature of 25°C. Subsequently, the nuclei are grown by controlling the pH value of an aqueous solution for growing the particles containing the nuclei thus formed to be 10.5-12.0 measured on the basis of a liquid temperature of 25°C and lower than the pH value in the nucleation process, and the Mn/Ni ratio of the liquid part in the solution is increased on the way of crystallization.

Description

  The present invention relates to a nickel manganese composite hydroxide particle that is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a positive electrode active for a secondary battery using the nickel manganese composite hydroxide particle as a raw material. The present invention relates to a substance, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery using the positive electrode active material for a non-aqueous electrolyte secondary battery as a positive electrode material.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. In addition, development of a high-power secondary battery is strongly desired as a battery for a motor drive power supply, particularly a power supply for transportation equipment.

  As a secondary battery satisfying such requirements, there is a lithium ion secondary battery. A lithium ion secondary battery includes a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as an active material for the negative electrode and the positive electrode.

  Research and development of lithium ion secondary batteries are currently being actively conducted. Among them, lithium ion secondary batteries using a layered or spinel type lithium metal composite oxide as a positive electrode material are of the 4V class. Since a high voltage can be obtained, practical use is progressing as a battery having a high energy density.

As a positive electrode material of such a lithium ion secondary battery, currently, lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel cheaper than cobalt, lithium Nickel cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), and the like have been proposed.

Among these positive electrode active materials, in recent years, lithium nickel manganese composite oxide (LiNi _0.5 Mn _0.5 O ₂ ) which has excellent thermal stability and high capacity without using cobalt with a small reserve is attracting attention. Lithium nickel manganese composite oxide (LiNi _0.5 Mn _0.5 O ₂ ) is a layered compound similar to lithium cobalt composite oxide and lithium nickel composite oxide, and basically has a composition ratio of 1: 1 (see Non-Patent Document 1).

  As a condition for obtaining good performance (high cycle characteristics, low resistance, high output) of the lithium ion secondary battery, it is required that the positive electrode active material particles having a uniform and appropriate particle size are uniformly dispersed in the positive electrode. Is done.

  This is because if the dispersion state is not uniform, the current flow is biased, causing problems such as a decrease in battery capacity and an increase in reaction resistance. The reason why the battery capacity is reduced is that the voltage applied to the particles in the electrode becomes non-uniform, and the particles with high voltage are selectively deteriorated when charging and discharging are repeated.

  Therefore, in order to improve the performance of the positive electrode material, the above-described lithium nickel manganese composite oxide can also be manufactured so that the positive electrode active material particles having a uniform and appropriate particle diameter are uniformly dispersed in the electrode. is necessary.

  As a cause of the occurrence of bias in dispersibility in the electrode, for example, the influence of the alkalinity of the active material can be mentioned. When the alkalinity of the active material is high, the alkali attacks the binder (PVDF) that is generally used in the preparation of the positive electrode paste and polymerizes the paste, causing the paste to gel, thereby making the active material uniform. It is known to cause a situation that does not disperse. One way to prevent this situation is to reduce the alkalinity of the active material.

  To date, no proposal has been made to reduce the alkalinity of the active material, but in order to improve the performance of the lithium-ion secondary battery, which is the final product, the lithium-nickel-manganese composite oxide that forms the cathode material Various attempts have been made to obtain particles having a narrow particle size distribution with respect to the composite hydroxide as a raw material.

For example, Patent Document 1 discloses composite hydroxide particles substantially having a manganese: nickel ratio of 1: 1, an average particle diameter of 5 to 15 μm, a tap density of 0.6 to 1.4 g / ml, The bulk density is 0.4 to 1.0 g / ml, the specific surface area is 20 to 55 m ² / g, the contained sulfate radical is 0.25 to 0.45% by mass, and 15 ≦ 2θ ≦ 25 in X-ray diffraction. The ratio (I ₀ / I ₁ ) between the maximum intensity (I ₀ ) of the peak at 10 and the maximum intensity (I ₁ ) of the peak at 30 ≦ 2θ ≦ 40 is ₁ to 6, Manganese nickel composite hydroxide particles have been proposed. Further, the surface and the internal structure of the secondary particles are formed as a net by pleated walls of primary particles, and the space surrounded by the pleated walls is said to be relatively large.

  Further, as a production method thereof, the atomic ratio of manganese to nickel is substantially increased in an aqueous solution having a pH value of 9 to 13 in the presence of a complexing agent while controlling the degree of oxidation of manganese ions within a certain range. It is disclosed to co-precipitate particles produced by reacting a 1: 1 mixed aqueous solution of manganese and nickel salts with an alkaline solution under suitable stirring conditions.

  However, in the lithium manganese nickel composite oxide of Patent Document 1 and the production method thereof, although the structure of the particles has been studied, the obtained particles are coarse particles, as is apparent from the disclosed electron micrographs. And fine particles are mixed, and no study has been made on the uniform particle size.

  On the other hand, regarding the particle size distribution of the lithium composite oxide, for example, Patent Document 2 discloses that in the particle size distribution curve, the average particle size D50, which means a particle size with a cumulative frequency of 50%, is 3 to 15 μm, and the minimum particle size is 0. In the relationship between D10 having a particle size distribution of not less than 0.5 μm and a maximum particle size of not more than 50 μm and a cumulative frequency of D10 of 10% and D90 of 90%, D10 / D50 is 0.60 to 0.90. , A lithium composite oxide having D10 / D90 of 0.30 to 0.70 is disclosed. Since this lithium composite oxide has high filling properties, is excellent in charge / discharge capacity characteristics and high output characteristics, and is difficult to deteriorate even under conditions with a large charge / discharge load, this lithium composite oxide can be used. For example, there is a description that a lithium ion non-aqueous electrolyte secondary battery having excellent output characteristics and little deterioration in cycle characteristics can be obtained.

  However, the lithium composite oxide disclosed in Patent Document 2 has a minimum particle size of 0.5 μm or more and a maximum particle size of 50 μm or less with respect to an average particle size of 3 to 15 μm. Coarse particles are included. And in the particle size distribution prescribed | regulated by said D10 / D50 and D10 / D90, it cannot be said that the range of a particle size distribution is narrow. That is, the lithium composite oxide of Patent Document 2 cannot be said to be a particle having sufficiently high particle size uniformity, and even if such a lithium composite oxide is employed, improvement in the performance of the positive electrode material cannot be expected. It is difficult to obtain a lithium ion non-aqueous electrolyte secondary battery having performance.

  A proposal has also been made for a method for producing a composite hydroxide, which is a raw material for a composite oxide, for the purpose of improving the particle size distribution. In Patent Document 3, in a method for producing a positive electrode active material for a non-aqueous electrolyte battery, an aqueous solution containing two or more transition metal salts, or two or more aqueous solutions of different transition metal salts and an alkaline solution are simultaneously used in a reaction vessel. There has been proposed a method of obtaining a precursor hydroxide or oxide by adding and coprecipitating with a reducing agent coexisting or aerated inert gas.

  However, since the technique of Patent Document 3 is to collect the generated crystals while classifying them, it is considered that manufacturing conditions must be strictly controlled in order to obtain a product having a uniform particle size. Industrial scale production is difficult. Moreover, it is difficult to obtain small-sized particles even though large-sized crystal particles can be obtained. In addition, since the particle size is uniformed by classification, the degree of homogenization does not exceed the accuracy of classification.

  As described above, there is no example that reports the study of reducing the alkalinity of the active material, and at present, on an industrial scale, it becomes a raw material of a composite oxide that can sufficiently improve the performance of a lithium ion secondary battery. No method has been developed that can produce composite hydroxides. In other words, a positive electrode active material that reduces the alkalinity of the active material and has high particle size uniformity and an appropriate particle size has not been developed. Development is required.

JP 2004-210560 A JP 2008-147068 A JP 2003-86182 A

Chemistry Letters, Vol.30 (2001), No.8, p.744

  In view of the problems involved, the present invention provides nickel manganese composite hydroxide particles that, when used as a raw material, provide a lithium nickel manganese composite oxide with reduced alkalinity as an active material and high particle size uniformity. For the purpose.

  In addition, the positive electrode active material, together with the positive electrode active material for non-aqueous secondary batteries, having a uniform particle size distribution and good filling properties and capable of reducing the value of the positive electrode resistance measured when used in a battery, It aims at providing the nonaqueous electrolyte secondary battery excellent in the used electrical property.

  Furthermore, an object of the present invention is to provide an industrial production method for the nickel manganese composite hydroxide particles and the positive electrode active material.

  As a result of intensive studies on a lithium nickel manganese composite oxide capable of exhibiting excellent battery characteristics when used as a positive electrode material of a lithium ion secondary battery, the present inventor has found that the lithium nickel manganese composite oxide constituting the positive electrode material By using composite hydroxide particles having a multilayer structure with different Mn / Ni ratios between the inside and the outer periphery of the composite hydroxide as a raw material, both battery characteristics and alkalinity reduction can be established. I learned that I can do it. Also, the knowledge that lithium nickel manganese composite oxide with high particle size uniformity can be obtained by controlling the particle size distribution of the nickel manganese composite hydroxide as a raw material and having a uniform particle size. Obtained. Furthermore, the nickel manganese composite hydroxide is obtained by controlling the pH during crystallization and separating it into a nucleation step and a particle growth step, and changes the Mn / Ni ratio in the aqueous solution during the crystallization. As a result, the inventors have obtained knowledge that the multilayer structure is obtained. The present invention has been completed based on these findings.

That is, the nickel manganese composite hydroxide particle of the present invention is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery,
General _{formula: Ni x Mn y Co z M} t (OH) 2 + α (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0.4,0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is represented by one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Hf, Ta, Mo, and W) Nickel manganese composite hydroxide having an average particle size of 3 to 11 μm and an index indicating the spread of the particle size distribution [(d90−d10) / average particle size] is 0.55 or less, Nickel-manganese composite hydroxide is a spherical secondary particle, and has a multilayer structure in which the composition of the inside of the secondary particle and the outer peripheral part are different, and the composition of the outer peripheral part is higher than the composition of the inner part of the secondary particle. It is characterized by a high ratio.

The outer peripheral portion of the secondary particles is represented by the general _{formula: Ni x Mn y Co z (} OH) 2 + α (0 ≦ x ≦ 0.4,0 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 1.0,0 ≦ t ≦ 0.2, x + y + z + t = 1, 0 ≦ α ≦ 0.5, M is one or more additions selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W It is preferably composed of a nickel manganese composite hydroxide represented by (element).

  Moreover, it is preferable that the thickness of the said outer peripheral part is 5 to 25% of a secondary particle diameter.

  In the secondary particles, it is preferable that the additive element is uniformly distributed and / or the surface thereof is uniformly coated with the additive element.

The method for producing nickel manganese composite hydroxide particles of the present invention comprises a general formula: Ni _x M _y Co _z M _t (OH) _{2 + a} (x + y + z + t = 1, 0.3 ≦ x ≦ 0.7) by crystallization reaction. , 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Al, Ti, V, Cr, Zr, Nb, A production method for producing nickel-manganese composite hydroxide particles that are precursors of a positive electrode active material for a non-aqueous electrolyte secondary battery represented by one or more additional elements selected from Hf, Ta, Mo, and W) There,
A nucleation aqueous solution containing at least a nickel-containing metal compound and a manganese-containing metal compound and an ammonium ion supplier is controlled so that the pH value becomes 12.0 to 14.0 based on a liquid temperature of 25 ° C. A nucleation process for nucleation,
The aqueous solution for particle growth containing nuclei formed in the nucleation step has a pH value of 10.5 to 12.0 and lower than the pH value in the nucleation step on the basis of a liquid temperature of 25 ° C. A particle growth step for growing the nucleus by controlling so that
And the Mn / Ni ratio of the liquid part of the aqueous solution in the outer peripheral part formation stage during crystallization is higher than that of the aqueous part in the inner formation stage.

It is preferable that the composition ratio of the metal ions contained in the liquid part of the aqueous solution in the outer peripheral part formation period be a composition ratio in the following general formula.
The general _{formula: Ni x Mn y Co z (} OH) 2 + α
(0 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 1.0, 0 ≦ t ≦ 0.2, x + y + z + t = 1, 0 ≦ α ≦ 0.5, M is One or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W)
The Mn / Ni ratio in the liquid part of the aqueous solution is preferably changed when a metal element amount of 10 to 90 mol% is supplied with respect to the total metal element amount supplied during crystallization.

The positive electrode active material of the present invention have the general _{formula: Li 1 + u Ni x Mn} y Co z M t O 2 (-0.05 ≦ u ≦ 0.50, x + y + z + t = 1,0.3 ≦ x ≦ 0.7 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W A positive electrode active material comprising a lithium nickel cobalt manganese composite oxide composed of a hexagonal lithium-containing composite oxide having a layered structure and having an average particle diameter Is 3 to 12 [mu] m, [(d90-d10) / average particle size] which is an index indicating the spread of the particle size distribution is 0.60 or less, and the alkalinity is pH = 10.6 to 11.5. It is characterized by.

  Moreover, the manufacturing method of the said positive electrode active material is the composite hydroxide particle manufacturing process which obtains nickel manganese composite hydroxide particle by the manufacturing method of the said nickel manganese composite hydroxide particle, and this nickel manganese composite hydroxide particle. A heat treatment step for heat treatment, a mixing step for mixing a lithium compound with the particles after the heat treatment to form a lithium mixture, and the mixture formed in the mixing step at 800 ° C. to 1000 ° C. in an oxidizing atmosphere. And a firing step of firing at a temperature.

  In the firing step, it is preferable to perform preliminary firing at a temperature of 350 ° C. to 800 ° C. in advance.

  The non-aqueous electrolyte secondary battery of the present invention is characterized in that the positive electrode is formed of the positive electrode active material for a non-aqueous electrolyte secondary battery.

  According to the present invention, when used as a raw material, the particle size uniformity is high, and the alkalinity as an active material is reduced, and the nickel manganese composite hydroxide that provides a lithium nickel manganese composite oxide with high particle size uniformity is obtained. Product particles are obtained. Further, the positive electrode active material comprising the lithium nickel manganese composite oxide has a high capacity and high output when used in a non-aqueous secondary battery, and is composed of a positive electrode containing the positive electrode active material. The non-aqueous secondary battery is provided with excellent battery characteristics.

  The nickel manganese composite hydroxide particles and the method for producing the positive electrode active material provided by the present invention are both easy and suitable for large-scale production, and their industrial value is extremely large.

It is a schematic flowchart of the process of manufacturing the nickel manganese composite hydroxide of this invention. It is a schematic flowchart of the other process which manufactures the nickel manganese composite hydroxide of this invention. It is a schematic flowchart of the process of manufacturing lithium nickel manganese composite oxide from the nickel manganese composite hydroxide of this invention. It is a schematic flowchart after manufacturing the nickel manganese composite hydroxide of this invention until manufacturing a non-aqueous electrolyte secondary battery. It is a SEM photograph (observation magnification 1,000 times) of the nickel manganese composite hydroxide of the present invention. It is the figure which showed the estimation method of the thickness of the surface layer with high Mn / Ni ratio in this invention. It is a SEM photograph (observation magnification 1,000 times) of the lithium nickel manganese composite oxide of this invention. It is the schematic of the coin battery used for battery evaluation. It is the equivalent circuit used for the measurement example and analysis of impedance evaluation.

  The present invention includes (1) nickel manganese composite hydroxide particles as a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery and a method for producing the same, and (2) a nonaqueous system using the nickel manganese composite hydroxide particles. The present invention relates to a positive electrode active material for an electrolyte secondary battery and a production method thereof, and (3) a non-aqueous electrolyte secondary battery using the positive electrode active material for a non-aqueous electrolyte secondary battery as a positive electrode.

  In order to improve the performance of the non-aqueous electrolyte secondary battery, the influence of the positive electrode active material for the non-aqueous electrolyte secondary battery employed in the positive electrode is large. In order to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery capable of obtaining such excellent battery characteristics, the particle size and particle size distribution are important factors, and the positive electrode active material adjusted to a desired particle size and particle size distribution is used. Substances are preferred. In order to obtain such a positive electrode active material, it is necessary to use nickel manganese composite hydroxide particles having a desired particle diameter and particle size distribution as precursors thereof.

  Hereinafter, each of the above inventions (1) to (3) will be described in detail. First, the nickel-manganese composite hydroxide particles and the production method thereof, which are the greatest features of the present invention, will be described.

(1-1) Nickel-manganese composite hydroxide particles The nickel-cobalt-manganese composite hydroxide particles of the present invention (hereinafter simply referred to as composite hydroxide particles of the present invention) are non-aqueous electrolyte secondary battery positive electrode active materials. A precursor comprising:
General _{formula: Ni x Mn y Co z M} t (OH) 2 + α (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0.4,0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is represented by one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Hf, Ta, Mo, and W) Nickel manganese composite hydroxide having an average particle size of 3 to 11 μm and an index indicating the spread of the particle size distribution [(d90−d10) / average particle size] is 0.55 or less, Nickel-manganese composite hydroxide is a spherical secondary particle, and has a multilayer structure in which the composition of the inside of the secondary particle and the outer peripheral part are different, and the composition of the outer peripheral part is higher than the composition of the inner part of the secondary particle. It is characterized by a high ratio.

(Particle composition)
The composite hydroxide particles of the present invention are adjusted so that the composition is represented by the above general formula. When a nickel nickel composite hydroxide having such a composition is used as a precursor to produce a lithium nickel manganese composite oxide, when an electrode using the lithium nickel manganese composite oxide as a positive electrode active material is used in a battery, The measured positive electrode resistance value can be lowered, and the battery performance can be improved.

  When a positive electrode active material is obtained using composite hydroxide particles as a raw material, the composition ratio (Ni: Mn: Co: M) of the composite hydroxide particles is also maintained in the obtained positive electrode active material. Therefore, the composition ratio of the composite hydroxide particles of the present invention is adjusted to be the same as the composition ratio required for the positive electrode active material to be obtained.

(Particle structure).
The discharge capacity of the battery becomes higher as the Mn / Ni ratio is lowered, and the performance is improved. On the other hand, the alkalinity of the active material is related to the Mn / Ni ratio. When the Mn / Ni ratio is high, the alkalinity is low. Conversely, when the Mn / Ni ratio is low, the alkalinity is high. That is, in order to reduce the alkalinity while improving the characteristics of the battery, it is necessary to establish both contradictory.

  Therefore, if the Mn / Ni ratio of the whole positive electrode active material is lowered and the Mn / Ni ratio of only the particle surface can be increased, the alkalinity of the active material surface can be expected to be reduced. In other words, in producing a high-performance lithium ion secondary battery as a final product by improving the performance of the positive electrode material, as a composite hydroxide as a raw material of the lithium nickel manganese composite oxide forming the positive electrode material, By increasing the Mn / Ni ratio in the vicinity of the surface from the inside of the secondary particles, the inside has a low Mn / Ni ratio and a high capacity, and the surface layer portion has a high Mn / Ni ratio and a low alkalinity. And a reduction in alkalinity can be achieved.

  The composite hydroxide particles of the present invention are adjusted so as to have a multilayer structure in which the composition of the secondary particles is different from that of the outer periphery. And since the Mn / Ni ratio of the composition of the outer peripheral part is adjusted to be higher than the composition inside the secondary particles, the alkalinity of the positive electrode active material is lowered, and gelation occurs when forming a paste in the electrode manufacturing process. Reaction can be suppressed, and an electrode in which an active material and a current collector are uniformly distributed can be manufactured. On the other hand, since the internal Mn / Ni ratio can be kept low, a sufficient battery capacity can be ensured.

Further, the outer peripheral portion of the secondary particles is represented by the general _{formula: Ni x Mn y Co z (} OH) 2 + α (0 ≦ x ≦ 0.4,0 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 1.0 , 0 ≦ t ≦ 0.2, x + y + z + t = 1, 0 ≦ α ≦ 0.5, M is one or more selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W It is preferable to be composed of a nickel manganese composite hydroxide represented by: By adjusting the outer peripheral portion to the above composition, the Mn / Ni ratio of the surface layer portion of the positive electrode active material obtained using the composite hydroxide particles of the present invention as a raw material becomes sufficiently high, and the alkalinity of the positive electrode active material is an appropriate value. Can be lowered.

  Moreover, it is preferable that the thickness of the said outer peripheral part with high Mn / Ni ratio is 5 to 25% of a secondary particle diameter. If the thickness of the outer peripheral portion is less than 5%, the effect of reducing the alkalinity may not be sufficiently obtained when the positive electrode active material is used. If the thickness exceeds 25%, the inside of the positive electrode active material and the Mn / Ni in the surface layer portion may be obtained. If the ratio becomes insufficient and an attempt to obtain a sufficient alkalinity reduction effect is obtained, the battery capacity may be reduced.

  The number of layers in the outer peripheral portion is not particularly limited, and may be an outer peripheral portion including a plurality of layers.

(Average particle size)
The composite hydroxide particles of the present invention have an average particle size of 3 to 11 μm, preferably 3 to 8 μm. By setting the average particle size to 3 to 11 μm, the positive electrode active material obtained using the composite hydroxide particles of the present invention as a raw material can be adjusted to a predetermined average particle size (3 to 12 μm). Thus, the particle size of the composite hydroxide particles correlates with the particle size of the positive electrode active material to be obtained, and therefore affects the characteristics of a battery using this positive electrode active material as the positive electrode material.

  Specifically, if the average particle size of the composite hydroxide particles is less than 3 μm, the average particle size of the obtained positive electrode active material also decreases, the packing density of the positive electrode decreases, and the battery capacity per volume increases. descend. On the other hand, when the average particle size of the composite hydroxide particles exceeds 11 μm, the specific surface area of the obtained positive electrode active material is reduced, and the interface with the electrolytic solution is reduced, thereby increasing the resistance of the positive electrode. The output characteristics of the battery deteriorate.

(Particle size distribution)
The composite hydroxide particles of the present invention are adjusted so that [(d90-d10) / average particle size], which is an index indicating the spread of the particle size distribution, is 0.55 or less, preferably 0.52 or less. ing.

  The particle size distribution of the positive electrode active material is strongly influenced by the composite hydroxide particles as the raw material. Therefore, if fine particles or coarse particles are mixed in the composite hydroxide particles, the same particles are also present in the positive electrode active material. To come. That is, when [(d90−d10) / average particle size] exceeds 0.55 and the particle size distribution is wide, fine particles or coarse particles also exist in the positive electrode active material.

  When a positive electrode is formed using a positive electrode active material in which a large amount of fine particles are present, heat may be generated due to a local reaction of the fine particles, which decreases the safety of the battery and selectively deteriorates the fine particles. Therefore, the cycle characteristics of the battery are deteriorated. On the other hand, when a positive electrode is formed using a positive electrode active material in which a large number of large particles are present, a sufficient reaction area between the electrolytic solution and the positive electrode active material cannot be obtained, and the battery output decreases due to an increase in reaction resistance.

  Therefore, in the composite hydroxide particles of the present invention, if [(d90-d10) / average particle size] is adjusted to 0.55 or less, the positive electrode active material obtained by using this as a precursor Also, the range of the particle size distribution becomes narrow, and the particle diameter can be made uniform. That is, with respect to the particle size distribution of the positive electrode active material, [(d90−d10) / average particle size] can be 0.60 or less. Thereby, in the battery using the positive electrode active material formed using the composite hydroxide particles of the present invention as a precursor as the positive electrode material, good output characteristics and high output can be achieved.

  It is conceivable to classify composite hydroxide particles having a wide normal distribution to obtain a composite hydroxide having a narrow particle size distribution, but classification by sieving is difficult and difficult. In addition, even with an apparatus such as a wet cyclone, it cannot be classified into a sufficiently narrow particle size distribution, and the industrial classification method has a uniform particle size distribution such as the composite hydroxide particles of the present invention. It is difficult to obtain a narrow composite hydroxide.

Specifically, using a cylindrical reaction vessel equipped with a stirrer and an overflow pipe, the pH was adjusted to 11.5 to 12.0 while adding a mixed aqueous solution of nickel sulfate and manganese sulfate and aqueous ammonia to the reaction vessel. After the inside of the reaction vessel is in a steady state, composite hydroxide particles are continuously collected from the overflow pipe, and the composition is Ni _0.50 Mn _0.50 (OH) _{2 + α} (0 ≦ α ≦ 0 .5) composite hydroxide particles were obtained. The obtained composite hydroxide particles were wet cyclone (Hydrocyclone, manufactured by Nippon Chemical Machinery Co., Ltd., NHC-1), the supply pressure was increased to remove coarse powder, and then the supply pressure was lowered again. However, only composite hydroxide particles having an average particle size of 8.5 and [(d ₉₀ -d ₁₀ ) / average particle size] of 0.67 were obtained.

  In the index [(d90−d10) / average particle size] indicating the spread of the particle size distribution, d10 is the number of particles in each particle size accumulated from the smaller particle size side, and the accumulated volume is the total volume of all particles. Means a particle size of 10%. D90 means the particle diameter in which the number of particles is accumulated in the same manner and the accumulated volume is 90% of the total volume of all particles.

  The method for obtaining the average particle diameter and d90 and d10 is not particularly limited, but can be obtained, for example, from the volume integrated value measured with a laser light diffraction / scattering particle size analyzer. As the average particle diameter, d50 is used, and a particle diameter in which the cumulative volume is 50% of the total particle volume may be used similarly to d90.

(1-2) Method for Producing Nickel Manganese Composite Hydroxide Particles The method for producing the composite hydroxide particles of the present invention may be any method as long as the composition of the inner and outer peripheral parts of the secondary grains can be changed. 1) Manufacturing method by batch crystallization, 2) Method of crystallizing secondary particles produced by continuous crystallization method, spray drying method, spray pyrolysis method, etc. 3) Manufacturing method by batch crystallization, continuous Examples include a method of mechanically coating secondary particles produced by a formula crystallization method, a spray drying method, a spray pyrolysis method, and the like. However, in order to obtain the particle size uniformity of the composite hydroxide particles of the present invention, it is optimal to use a batch-type seed crystal method, and a production method using the batch-type seed crystal method will be described below.

  The method for producing composite hydroxide particles of the present invention is a method for producing nickel manganese composite hydroxide particles by a crystallization reaction, wherein a) a nucleation step for nucleation and b) a nucleation step. And a particle growth process for growing the formed nuclei.

  That is, in the conventional continuous crystallization method, since the nucleation reaction and the particle growth reaction proceed simultaneously in the same tank, the particle size distribution of the obtained composite hydroxide particles becomes wide. On the other hand, in the method for producing composite hydroxide particles of the present invention, the time mainly when the nucleation reaction occurs (nucleation process) and the time when the particle growth reaction mainly occurs (particle growth process) are clearly separated. Thus, the obtained composite hydroxide particles are characterized in that a narrow particle size distribution is achieved. Furthermore, by controlling the atmosphere during the crystallization reaction, the particle structure of the resulting composite hydroxide particles was composed of a central part composed of fine primary particles and an outer shell part composed of primary particles larger than the central part. There is a feature in the point to be.

  Initially, the outline of the manufacturing method of the composite hydroxide particle of this invention is demonstrated based on FIG. In FIGS. 1 and 2, (A) corresponds to the nucleation step and (B) corresponds to the particle growth step.

(Nucleation process)
As shown in FIG. 1, in the method for producing composite hydroxide particles of the present invention, first, a plurality of metal compounds containing nickel and manganese are dissolved in water at a predetermined ratio to produce a mixed aqueous solution. In the method for producing composite hydroxide particles of the present invention, the composition ratio of each metal in the obtained composite hydroxide particles is the same as the composition ratio of each metal in the mixed aqueous solution.

  Therefore, the ratio of the metal compound dissolved in water is adjusted so that the composition ratio of each metal in the mixed aqueous solution is the same as the composition ratio of each metal in the composite hydroxide particles of the present invention. A mixed aqueous solution is prepared.

  On the other hand, an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous ammonia solution containing an ammonium ion supplier, and water are supplied to the reaction vessel and mixed to form an aqueous solution. The pH value of this aqueous solution (hereinafter referred to as “pre-reaction aqueous solution”) is adjusted to 12.0 to 14.0, preferably 12.3 based on the liquid temperature of 25 ° C. by adjusting the supply amount of the alkaline aqueous solution. Adjust to the range of 13.4. The concentration of ammonium ions in the aqueous solution before reaction is adjusted to 3 to 25 g / L, preferably 3 to 20 g / L by adjusting the supply amount of the aqueous ammonia solution. The temperature of the aqueous solution before reaction is also preferably adjusted to 20 to 60 ° C, more preferably 35 to 60 ° C. About the pH value of the aqueous solution in a reaction tank, and the density | concentration of ammonium ion, it can each measure with a general pH meter and an ion meter.

  When the temperature and pH of the aqueous solution before reaction are adjusted in the reaction vessel, the mixed aqueous solution is supplied into the reaction vessel while stirring the aqueous solution before reaction. As a result, a nucleation aqueous solution, which is a reaction aqueous solution in the nucleation step, is formed in the reaction tank by mixing the pre-reaction aqueous solution and the mixed aqueous solution, and fine nuclei of the composite hydroxide are formed in the nucleation aqueous solution. Will be generated. At this time, since the pH value of the aqueous solution for nucleation is within the above range, the produced nuclei hardly grow and the nucleation is preferentially generated.

  In addition, since the pH value and ammonium ion concentration of the aqueous solution for nucleation change with the nucleation due to the supply of the mixed aqueous solution, the alkaline aqueous solution and the aqueous ammonia solution are supplied to the aqueous solution for nucleation together with the mixed aqueous solution. The pH value of the aqueous solution for nucleation is controlled so as to maintain the range of 12.0 to 14.0 and the concentration of ammonium ion in the range of 3 to 25 g / L on the basis of the liquid temperature of 25 ° C.

  By supplying the mixed aqueous solution, the alkaline aqueous solution and the aqueous ammonia solution to the nucleation aqueous solution, new nuclei are continuously generated in the nucleation aqueous solution. When a predetermined amount of nuclei is generated in the aqueous solution for nucleation, the nucleation step is finished. Whether or not a predetermined amount of nuclei has been generated is determined by the amount of metal salt added to the aqueous solution for nucleation.

(Particle growth process)
After completion of the nucleation step, the pH value of the aqueous solution for nucleation is 10.5 to 12.0, preferably 11.0 to 12.0, based on the liquid temperature of 25 ° C., and the pH value in the nucleation step. The aqueous solution for particle growth, which is a reaction aqueous solution in the particle growth step, is obtained by adjusting to a lower pH value. Specifically, the control of the pH during the adjustment is performed by adjusting the supply amount of the alkaline aqueous solution.

  By setting the pH value of the aqueous solution for particle growth within the above range, the nucleus growth reaction takes precedence over the nucleus generation reaction. Therefore, in the particle growth process, new nuclei are contained in the particle growth aqueous solution. With almost no generation, the nucleus grows (particle growth) to form composite hydroxide particles having a predetermined particle size.

  Similarly, since the pH value of the aqueous solution for particle growth and the concentration of ammonium ions change as the particles grow due to the supply of the mixed aqueous solution, an alkaline aqueous solution and an aqueous ammonia solution are supplied to the aqueous solution for particle growth together with the mixed aqueous solution. Thus, the pH value of the aqueous solution for particle growth is controlled so as to maintain the range of 10.5 to 12.0 and the concentration of ammonium ion of 3 to 25 g / L on the basis of the liquid temperature of 25 ° C.

  Thereafter, when the composite hydroxide particles grow to a predetermined particle size, the particle growth step is terminated. The particle size of the composite hydroxide particles can be determined in each step by obtaining the relationship between the amount of metal salt added to each reaction aqueous solution and the resulting particles in each step of the nucleation step and particle growth step by preliminary tests. It can be easily judged from the amount of metal salt added.

  As described above, in the case of the method for producing the composite hydroxide particles, nucleation occurs preferentially in the nucleation step, and almost no nucleation occurs. Conversely, only nucleation occurs in the particle growth step, Almost no new nuclei are generated. For this reason, in the nucleation step, homogeneous nuclei with a narrow particle size distribution range can be formed, and in the particle growth step, nuclei can be grown homogeneously. Therefore, in the above method for producing composite hydroxide particles, the range of particle size distribution is narrow, and uniform nickel manganese composite hydroxide particles can be obtained.

  In the case of the above production method, in both steps, the metal ions are crystallized as nuclei or composite hydroxide particles, so that the ratio of the liquid component to the metal component in each reaction aqueous solution increases. In this case, apparently, the concentration of the mixed aqueous solution to be supplied is lowered, and there is a possibility that the composite hydroxide particles are not sufficiently grown particularly in the particle growth step.

  Therefore, in order to suppress the increase of the liquid component, it is preferable to discharge a part of the liquid component in the aqueous solution for particle growth to the outside of the reaction tank in the middle of the particle growth step after the nucleation step. Specifically, the supply and stirring of the mixed aqueous solution, alkaline aqueous solution and aqueous ammonia solution to the particle growth aqueous solution are stopped, the nuclei and composite hydroxide particles are allowed to settle, and the supernatant liquid of the particle growth aqueous solution is discharged. Thereby, the relative concentration of the mixed aqueous solution in the aqueous solution for particle growth can be increased. Since the composite hydroxide particles can be grown in a state in which the relative concentration of the mixed aqueous solution is high, the particle size distribution of the composite hydroxide particles can be narrowed, and the secondary particles of the composite hydroxide particles The density of the entire particle can also be increased.

  In the embodiment shown in FIG. 1, the pH of the aqueous solution for nucleation after completion of the nucleation step is adjusted to form an aqueous solution for particle growth, and the particle growth step is subsequently performed from the nucleation step. There is an advantage that the transition to the particle growth process can be performed quickly. Furthermore, the transition from the nucleation step to the particle growth step can be performed simply by adjusting the pH of the reaction aqueous solution, and the pH can also be easily adjusted by temporarily stopping the supply of the alkaline aqueous solution. There is. The pH of the reaction aqueous solution can also be adjusted by adding sulfuric acid to the reaction aqueous solution in the case of an inorganic acid of the same kind as the acid constituting the metal compound, for example, sulfate.

  However, as in another embodiment shown in FIG. 2, a component-adjusted aqueous solution adjusted to a pH and ammonium ion concentration suitable for the particle growth step is formed separately from the aqueous solution for nucleation, and this component-adjusted aqueous solution is used. , An aqueous solution containing nuclei generated by performing a nucleation step in another reaction tank (aqueous solution for nucleation, preferably one obtained by removing a part of the liquid component from the aqueous solution for nucleation) to obtain a reaction aqueous solution, You may perform a particle growth process by making this reaction aqueous solution into the aqueous solution for particle growth.

  In this case, since the nucleation step and the particle growth step can be more reliably separated, the state of the reaction aqueous solution in each step can be set to an optimum condition for each step. In particular, the pH of the aqueous solution for particle growth can be set to an optimum condition from the start of the particle growth step. The nickel manganese composite hydroxide particles formed in the particle growth step can have a narrower particle size distribution range and be uniform.

  Next, control of the reaction atmosphere in each process, substances and solutions used in each process, and reaction conditions will be described in detail.

(PH control)
As described above, in the nucleation step, it is necessary to control the pH value of the reaction aqueous solution to be in the range of 12.0 to 14.0, preferably 12.3 to 13.4 on the basis of the liquid temperature of 25 ° C. There is. When the pH value exceeds 14.0, the produced nuclei become too fine and the reaction aqueous solution gels. On the other hand, when the pH value is less than 12.0, a nucleus growth reaction occurs together with nucleation, so that the range of the particle size distribution of the nuclei formed becomes wide and non-uniform. That is, in the nucleation step, by controlling the pH value of the reaction aqueous solution within the above range, it is possible to suppress the growth of nuclei and cause almost only nucleation. Can be narrow.

  On the other hand, in the particle growth step, it is necessary to control the pH value of the aqueous reaction solution to be in the range of 10.5 to 12.0, preferably 11.0 to 12.0 on the basis of the liquid temperature of 25 ° C. When the pH value exceeds 12.0, more nuclei are newly generated and fine secondary particles are generated, so that hydroxide particles having a good particle size distribution cannot be obtained. On the other hand, when the pH value is less than 10.5, the solubility by ammonia ions is high, and the metal ions remaining in the liquid without being precipitated increase, so that the production efficiency is deteriorated. Further, when a metal sulfate is used as a raw material, the amount of S (sulfur) remaining in the particles increases, which is not preferable. That is, in the particle growth process, by controlling the pH of the reaction aqueous solution within the above range, it is possible to preferentially cause the growth of nuclei generated in the nucleation process and suppress new nucleation. The nickel manganese composite hydroxide particles can be homogeneous and have a narrow particle size distribution range.

  In both the nucleation step and the particle growth step, the fluctuation range of the pH is preferably within 0.2 above and below the set value. When the pH fluctuation range is large, nucleation and particle growth are not constant, and uniform nickel manganese composite hydroxide particles having a narrow particle size distribution range may not be obtained.

  When the pH value is 12, it is a boundary condition between nucleation and nucleation, and therefore, it can be set as either a nucleation process or a particle growth process depending on the presence or absence of nuclei present in the reaction aqueous solution. .

  That is, if the pH value in the nucleation step is higher than 12 and a large amount of nuclei are produced, and if the pH value is set to 12 in the particle growth step, a large amount of nuclei are present in the reaction aqueous solution, so the growth of nuclei takes priority. Thus, the hydroxide particles having a narrow particle size distribution and a relatively large particle size can be obtained.

  On the other hand, when no nuclei exist in the reaction aqueous solution, that is, when the pH value is set to 12 in the nucleation step, since no nuclei grow, nucleation occurs preferentially, and the pH value of the particle growth step is set to 12. By making it smaller, the produced | generated nucleus grows and the said hydroxide particle | grains favorable are obtained.

  In any case, the pH value of the particle growth process may be controlled to a value lower than the pH value of the nucleation process. To clearly separate nucleation and particle growth, the pH value of the particle growth process is It is preferably 0.5 or more lower than the pH value of the production step, more preferably 1.0 or more.

(Nucleation amount)
The amount of nuclei generated in the nucleation step is not particularly limited, but in order to obtain composite hydroxide particles having a good particle size distribution, the total amount, that is, to obtain composite hydroxide particles. The total metal salt to be supplied is preferably 0.1% to 2%, more preferably 1.5% or less.

(Controlling the particle size of composite hydroxide particles)
Since the particle size of the composite hydroxide particles can be controlled by the time of the particle growth step, if the particle growth step is continued until it grows to a desired particle size, composite hydroxide particles having the desired particle size are obtained. be able to.

  Further, the particle size of the composite hydroxide particles can be controlled not only by the particle growth step but also by the pH value of the nucleation step and the amount of raw material charged for nucleation.

  That is, by increasing the pH during nucleation to the high pH value side or by increasing the nucleation time, the amount of raw material to be added is increased and the number of nuclei to be generated is increased. Thereby, even when the particle growth step is performed under the same conditions, the particle size of the composite hydroxide particles can be reduced. On the other hand, if the nucleation number is controlled to be small, the particle size of the obtained composite hydroxide particles can be increased.

(Particle structure control of composite hydroxide particles)
The composition of the composite hydroxide particles is the same as the composition ratio of the liquid part of the reaction aqueous solution, that is, the composition ratio of each metal in the mixed aqueous solution. Therefore, in order to obtain a multilayer structure in which the Mn / Ni ratio of the outer peripheral composition is higher than the internal composition of the secondary particles, the Mn / Ni ratio of the liquid part of the aqueous solution in the outer peripheral part formation stage during crystallization is What is necessary is just to make it higher than the liquid part of the aqueous solution in a formation period. That is, the composition ratio of each metal in the mixed aqueous solution to be supplied is determined from the nucleation to the inside of the composite hydroxide grains having a relatively low Mn / Ni ratio until a predetermined total amount of metal elements is supplied in the growth process. The above multilayer structure can be obtained by changing the composition ratio of the outer peripheral portion having a relatively high Mn / Ni ratio until the completion of crystallization after the supply of the predetermined total amount of metal elements. Since the volume ratio between the inside and the outer periphery of the secondary particles is proportional to the total amount of metal elements to be supplied, it can be easily controlled.

In addition, since the required time can be obtained from the supply rate per metal element of the mixed aqueous solution, the thickness of the outer peripheral portion may be controlled by the time for supplying the mixed aqueous solution. What is necessary is just to crystallize for the time required by each composition ratio so that a part may become desired thickness.
The Mn / Ni ratio of the liquid part of the aqueous solution is preferably changed when a metal element amount of 10 to 90 mol% is supplied with respect to the total metal element amount supplied during crystallization. Thereby, the thickness of the said outer peripheral part is controllable to 1.5-25% of the secondary particle diameter which is a preferable range.

  Hereinafter, conditions such as the atmosphere in the reaction tank, stirring of the reaction aqueous solution, metal compound, ammonia concentration in the reaction aqueous solution, reaction temperature, etc. will be described. The difference between the nucleation step and the particle growth step is that the pH of the reaction aqueous solution is It is only the range to be controlled, and the conditions such as the atmosphere in the reaction vessel, the stirring of the reaction aqueous solution, the metal compound, the ammonia concentration in the reaction solution, the reaction temperature, and the like are substantially the same in both steps.

(Reaction atmosphere)
In the nucleation step, the oxygen concentration in the reaction vessel space is preferably 10% by volume or less, more preferably 5% by volume or less, and further preferably from the viewpoint of stably generating particles by suppressing the oxidation of cobalt and manganese. Must be controlled to 1% by volume or less. Oxidation control is also important in the particle growth process, and it is necessary to similarly control the oxygen concentration in the reaction vessel space. The oxygen concentration in the atmosphere can be adjusted using, for example, an inert gas such as nitrogen or argon. As a means for adjusting the oxygen concentration in the atmosphere to be a predetermined concentration, for example, a constant amount of atmospheric gas is always circulated in the atmosphere.

(Metal compound)
As the metal compound, a compound containing the target metal is used. As the compound to be used, a water-soluble compound is preferably used, and examples thereof include nitrates, sulfates and hydrochlorides. For example, nickel sulfate, manganese sulfate, and cobalt sulfate are preferably used.

(Additive elements)
The additive element (one or more elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) is preferably a water-soluble compound. For example, titanium sulfate, peroxo Ammonium titanate, titanium potassium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, etc. can be used. .

  When the additive element is uniformly dispersed inside the composite hydroxide particle, an additive containing the additive element may be added to the mixed aqueous solution, and the additive element is uniformly distributed inside the composite hydroxide particle. It can be coprecipitated in a dispersed state.

  When the surface of the composite hydroxide particles is coated with an additive element, for example, the composite hydroxide particles are slurried with an aqueous solution containing the additive element and controlled to have a predetermined pH, If an aqueous solution containing one or more additive elements is added and the additive elements are precipitated on the surface of the composite hydroxide particles by a crystallization reaction, the surface can be uniformly coated with the additive elements. In this case, an alkoxide solution of the additive element may be used instead of the aqueous solution containing the additive element. Furthermore, the surface of the composite hydroxide particles can be coated with the additive element by spraying an aqueous solution or slurry containing the additive element onto the composite hydroxide particle and drying it. Also, the slurry in which the composite hydroxide particles and the salt containing one or more additional elements are suspended is spray-dried, or the composite hydroxide and the salt containing one or more additional elements are mixed by a solid phase method. It can coat | cover by methods, such as doing.

  In addition, when the surface is coated with an additive element, the atomic ratio of the metal ions of the resulting composite hydroxide particles is reduced by reducing the atomic ratio of the additive element ions present in the mixed aqueous solution by the amount to be coated. Can be matched. Moreover, you may perform the process of coat | covering the surface of particle | grains with an additive element with respect to the particle | grains after heat-processing composite hydroxide particle | grains.

(Concentration of mixed aqueous solution)
The concentration of the mixed aqueous solution is preferably 1 to 2.6 mol / L, more preferably 1.5 to 2.2 mol / L in total of the metal compounds. When the concentration of the mixed aqueous solution is less than 1 mol / L, the amount of crystallized product per reaction tank is decreased, and thus the productivity is not preferable.

  On the other hand, when the salt concentration of the mixed aqueous solution exceeds 2.6 mol / L, the saturated concentration at room temperature is exceeded, so there is a risk that crystals re-deposit and clog the equipment piping.

  In addition, the metal compound does not necessarily have to be supplied to the reaction vessel as a mixed aqueous solution. For example, when a metal compound that reacts when mixed to produce a compound is used, the total concentration of all the metal compound aqueous solutions is within the above range. As described above, the metal compound aqueous solution may be prepared individually and supplied into the reaction vessel at a predetermined ratio simultaneously as an aqueous solution of each metal compound.

  Further, the amount of the mixed aqueous solution and the aqueous solution of each metal compound supplied to the reaction tank is such that the concentration of the crystallized product at the time when the crystallization reaction is completed is approximately 30 to 200 g / L, preferably 80 to 150 g / L. It is desirable to become. When the crystallized substance concentration is less than 30 g / L, aggregation of primary particles may be insufficient, and when it exceeds 200 g / L, diffusion of the mixed aqueous solution to be added in the reaction vessel is sufficient. This is because the grain growth may be biased.

(Ammonia concentration)
The ammonia concentration in the reaction aqueous solution is preferably maintained within a range of 3 to 25 g / L, preferably 3 to 20 g / L.

  Since ammonia acts as a complexing agent, if the ammonia concentration is less than 3 g / L, the solubility of metal ions cannot be kept constant, and plate-shaped hydroxide primary particles having a uniform shape and particle size Is not formed, and gel-like nuclei are easily generated, so that the particle size distribution is likely to be widened.

  On the other hand, when the ammonia concentration exceeds 25 g / L, the solubility of metal ions is large and the hydroxide is densely formed. Therefore, the positive electrode active material for a non-aqueous electrolyte secondary battery finally obtained is also dense. The structure may be small, the particle size may be small, and the specific surface area may be low. Further, if the solubility of metal ions becomes too high, the amount of metal ions remaining in the reaction aqueous solution increases, resulting in a compositional shift or the like.

  Further, when the ammonia concentration varies, the solubility of metal ions varies, and uniform hydroxide particles are not formed. Therefore, it is preferable to maintain a constant value. For example, the ammonia concentration is preferably maintained at a desired concentration by setting the upper and lower limits to about 5 g / L.

  Although it does not specifically limit about an ammonium ion supply body, For example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride etc. can be used.

(Reaction temperature)
In the reaction vessel, the temperature of the reaction solution is preferably set to 20 to 60 ° C. or more, particularly preferably 35 to 60 ° C. When the temperature of the reaction solution is lower than 20 ° C., the solubility of metal ions is low, so that nucleation is likely to occur and control becomes difficult. On the other hand, when the temperature exceeds 60 ° C., volatilization of ammonia is promoted. Therefore, in order to maintain a predetermined ammonia concentration, it is necessary to add an excess ammonium ion supplier, resulting in an increase in cost.

(Alkaline aqueous solution)
The aqueous alkali solution for adjusting the pH in the aqueous reaction solution is not particularly limited, and for example, an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide can be used. In the case of such an alkali metal hydroxide, it may be supplied directly into the reaction aqueous solution, but it is preferable to add it as an aqueous solution to the reaction aqueous solution in the reaction vessel for ease of pH control of the reaction aqueous solution in the reaction vessel. .

  Further, the method for adding the aqueous alkaline solution to the reaction vessel is not particularly limited, and the pH value of the aqueous reaction solution is predetermined by a pump capable of controlling the flow rate, such as a metering pump, while sufficiently stirring the aqueous reaction solution. It may be added so that it is maintained in the range of.

(production equipment)
In the method for producing composite hydroxide particles of the present invention, an apparatus that does not recover the product until the reaction is completed is used. For example, it is a normally used batch reactor equipped with a stirrer. By adopting such an apparatus, unlike the continuous crystallization apparatus that recovers the product by a general overflow, there is no problem that the growing particles are recovered simultaneously with the overflow liquid. Uniform particles can be obtained.

  In addition, when the reaction atmosphere is controlled, a device capable of controlling the atmosphere such as a hermetically sealed device is used. By using such an apparatus, the nucleation reaction and particle growth reaction can be carried out almost uniformly, so that particles having an excellent particle size distribution, that is, composite hydroxide particles having a narrow particle size distribution range can be obtained. it can.

(2-1) a positive electrode active material of the positive electrode active material present invention for a nonaqueous electrolyte secondary battery is represented by the general _{formula: Li 1 + u Ni x Mn} y Co z M t O 2 (-0.05 ≦ u ≦ 0.250, x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.554, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.102, M is an additive element , Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W), and a lithium nickel manganese composite oxide particle represented by a layered structure. It has a hexagonal crystal structure.

(composition)
The positive electrode active material of the present invention is lithium nickel manganese composite oxide particles whose composition is adjusted so as to be represented by the following general formula.
_{Formula: Li 1 + u Ni x Mn} y Co z M t O 2
(−0.05 ≦ u ≦ 0.250, x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.554, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W)
In the positive electrode active material of the present invention, u indicating an excess amount of lithium is in the range of −0.05 to 0.50. When the excess amount u of lithium is less than −0.05, the reaction resistance of the positive electrode in the nonaqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the output of the battery decreases. Moreover, alkalinity will be less than the minimum of this invention. On the other hand, when the excessive amount u of lithium exceeds 0.50, the initial discharge capacity when the positive electrode active material is used for the positive electrode of the battery is lowered and the reaction resistance of the positive electrode is also increased. In order to further reduce the reaction resistance, the excess amount u of lithium is preferably 0.05 or more, and more preferably 0.20 or less.

  Furthermore, in the positive electrode active material of the present invention, the Mn / Ni ratio of the surface layer portion is preferably higher than the inside, and the ratio of the Mn / Ni ratio (SMN) of the surface layer portion to the internal Mn / Ni ratio (IMN) ( SMN / IMN) is preferably 1.3-50. Thereby, alkalinity can be made into the range of this invention. The SMN ratio and the IMN ratio can be obtained by analysis such as EDX analysis in cross-sectional SEM observation.

  Moreover, as represented by the above general formula, the positive electrode active material of the present invention is more preferably adjusted so as to contain an additive element in the lithium nickel manganese composite oxide particles. By including the additive element, it is possible to improve durability characteristics and output characteristics of a battery using the additive element as a positive electrode active material.

  In particular, since the additive element is uniformly distributed on the surface or inside of the particle, the above effect can be obtained over the entire particle, and the above effect can be obtained with a small amount of addition, and a decrease in capacity can be suppressed.

  Furthermore, in order to obtain the effect with a smaller addition amount, it is preferable to increase the concentration of the additive element on the particle surface from the inside of the particle.

  When the atomic ratio t of the additive element M exceeds 0.1, the metal element contributing to the Redox reaction is decreased, which is not preferable because the battery capacity is decreased. Therefore, the additive element M is adjusted so as to fall within the above range at the atomic ratio t.

(Average particle size)
The positive electrode active material of the present invention has an average particle size of 3 to 12 μm, preferably 3 to 10 μm. When the average particle size is less than 3 μm, the tap density decreases, and when the positive electrode is formed, the packing density of the particles decreases, and the battery capacity per positive electrode volume decreases. On the other hand, when the average particle size exceeds 12 μm, the specific surface area of the positive electrode active material is reduced, and the interface with the battery electrolyte is reduced, thereby increasing the resistance of the positive electrode and lowering the output characteristics of the battery.

  Therefore, if the positive electrode active material of the present invention is adjusted to have an average particle size of 3 to 12 μm, preferably 3 to 10 μm, a battery using this positive electrode active material for the positive electrode has a large battery capacity per volume. In addition, it is possible to obtain excellent battery characteristics such as high safety and high output.

(Particle size distribution)
The positive electrode active material of the present invention has a [(d90-d10) / average particle size] which is an index indicating the spread of the particle size distribution of 0.60 or less, and is a secondary secondary of a lithium nickel manganese composite oxide having extremely high homogeneity. Consists of particles.

  The positive electrode active material of the present invention has an index ((d90-d10) / average particle diameter) indicating the spread of the particle size distribution of 0.60 or less, preferably 0.55 or less. When the particle size distribution is wide, there are many fine particles having a very small particle size with respect to the average particle size and coarse particles having a very large particle size with respect to the average particle size in the positive electrode active material. Become. When a positive electrode is formed using a positive electrode active material in which a large amount of fine particles are present, heat may be generated due to a local reaction of the fine particles, and safety is lowered and the fine particles are selectively deteriorated. As a result, the cycle characteristics deteriorate. On the other hand, when a positive electrode is formed using a positive electrode active material with a large amount of coarse particles, the reaction area between the electrolytic solution and the positive electrode active material is not sufficient, and the battery output is reduced due to an increase in reaction resistance.

  Therefore, by setting the particle size distribution of the positive electrode active material to 0.60 or less with the above-mentioned index [(d90-d10) / average particle size], the proportion of fine particles and coarse particles can be reduced. The battery used for the positive electrode is excellent in safety and has good cycle characteristics and battery output. The average particle diameter, d90 and d10 are the same as those used for the composite hydroxide particles described above, and the measurement can be performed in the same manner.

(Alkalinity)
The positive electrode active material of the present invention has an alkalinity of pH = 10.6 to 11.5. The alkalinity is defined as the pH value of a slurry in which 2 g of the positive electrode active material is slurried in 100 cc of water at 25 ° C., stirred for 1 minute, and allowed to stand for 5 minutes.

  When the pH indicating the alkalinity is less than 10.6, there is little surplus lithium on the surface of the positive electrode active material particles, and thus a sufficient capacity cannot be obtained. On the other hand, if the pH exceeds 11.5, gelation of the paste occurs during preparation of the positive electrode paste for the battery, and the active material is not uniformly dispersed in the positive electrode material, resulting in a decrease in battery capacity and an increase in positive electrode resistance.

(2-2) Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery The method for producing a positive electrode active material of the present invention produces a positive electrode active material so as to have the above average particle size, particle size distribution, particle structure and composition. If it can, it will not specifically limit, However, If the following method is employ | adopted, since this positive electrode active material can be manufactured more reliably, it is preferable.

  As shown in FIG. 3, the method for producing a positive electrode active material of the present invention includes a) a step of heat-treating nickel manganese composite hydroxide particles as a raw material of the positive electrode active material of the present invention, and b) On the other hand, it includes a mixing step of mixing a lithium compound to form a lithium mixture, and c) a baking step of baking the mixture formed in the mixing step. Hereinafter, each process will be described.

a) Heat treatment step In the heat treatment step, nickel manganese composite hydroxide particles (hereinafter, simply referred to as “composite hydroxide particles”) obtained by the method for producing nickel manganese composite hydroxide particles are 105 to 750 ° C., preferably It is a process of heating to a temperature of 105 to 400 ° C. and removing heat contained in the composite hydroxide particles. By performing this heat treatment step, the moisture remaining in the particles up to the firing step can be reduced to a certain amount. Thereby, it can prevent that the ratio of the atomic number of the metal in the positive electrode active material manufactured and the atomic number of lithium varies.

  In addition, since it is sufficient that water can be removed to such an extent that the ratio of the number of metal atoms and the number of lithium atoms in the positive electrode active material does not vary, all composite hydroxide particles are not necessarily nickel manganese composite oxide particles (hereinafter, It is not necessary to simply convert it into “composite oxide particles”), and it is sufficient to perform heat treatment at a temperature of 400 ° C. or lower. However, in order to reduce the variation, the composite hydroxide particles may be converted into composite oxide particles by setting the heating temperature to 400 ° C. or higher.

  In the heat treatment step, when the heating temperature is lower than 105 ° C., excess moisture in the composite hydroxide particles cannot be removed, and the above variation cannot be suppressed. On the other hand, when the heating temperature exceeds 750 ° C., the particles are sintered by heat treatment, and complex oxide particles having a uniform particle size cannot be obtained. The dispersion | variation can be suppressed by calculating | requiring previously the metal component contained in the composite hydroxide particle by heat processing conditions by analysis, and determining ratio with a lithium compound.

  The atmosphere in which the heat treatment is performed is not particularly limited and may be a non-reducing atmosphere, but is preferably performed in an air stream that can be easily performed.

  In addition, the heat treatment time is not particularly limited, but if it is less than 1 hour, the excess moisture of the composite hydroxide particles may not be sufficiently removed, so at least 1 hour is preferable, and 5 to 15 hours is more preferable. .

The equipment used for the heat treatment is not particularly limited as long as the composite hydroxide particles can be heated in a non-reducing atmosphere, preferably in an air stream, and no electric gas is generated. Etc. are preferably used.
b) Mixing step In the mixing step, the composite hydroxide particles (hereinafter referred to as “heat treated particles”) heat-treated in the above heat treatment step and a lithium-containing substance, for example, a lithium compound are mixed to obtain a lithium mixture. It is the process of obtaining.

  Here, the heat treated particles include not only the composite hydroxide particles from which residual moisture has been removed in the heat treatment step, but also composite oxide particles converted to oxides in the heat treatment step, or mixed particles thereof.

  The heat-treated particles and the lithium compound are a ratio of the number of atoms of metals other than lithium in the lithium mixture, that is, the sum of the number of atoms of nickel, manganese, cobalt and additive elements (Me) to the number of atoms of lithium (Li). (Li / Me) is mixed so that it may become 0.95-1.5, Preferably it is 1-1.35, More preferably, it is 1.05-1.20. That is, since Li / Me does not change before and after the firing step, Li / Me mixed in this mixing step becomes Li / Me in the positive electrode active material, so that Li / Me in the lithium mixture is to be obtained. To be the same as Li / Me.

  The lithium compound used to form the lithium mixture is not particularly limited, but for example, lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof is preferable in that it is easily available. . In particular, in view of ease of handling and quality stability, it is more preferable to use lithium hydroxide, lithium carbonate, or a mixture thereof.

  The lithium mixture is preferably mixed well before firing. If the mixing is not sufficient, Li / Me varies among individual particles, and problems such as a time when sufficient battery characteristics cannot be obtained may occur.

  Moreover, a general mixer can be used for mixing, for example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, etc. can be used, and the shape such as heat-treated particles is not destroyed. It is sufficient that the composite oxide particles and the substance containing lithium are sufficiently mixed.

c) Firing step The firing step is a step of firing the lithium mixture obtained in the mixing step to form a lithium nickel manganese composite oxide. When the lithium mixture is fired in the firing step, lithium in the lithium-containing substance is diffused into the heat-treated particles, so that the lithium nickel manganese composite oxide is formed.

(Baking temperature)
Firing of the lithium mixture is performed at 800 to 1000 ° C, preferably 820 to 960 ° C, more preferably 850 to 940 ° C.
When the firing temperature is less than 800 ° C., the diffusion of lithium into the nickel manganese composite oxide particles is not sufficient, and excess lithium and unreacted nickel manganese composite oxide remain, or the crystal structure becomes insufficient. In other words, sufficient battery characteristics cannot be obtained when used in batteries.

Further, when the temperature exceeds 1000 ° C., intense sintering occurs between the lithium nickel manganese composite oxide particles and abnormal grain growth occurs, so that the particles become coarse and the shape of the spherical secondary particles cannot be maintained. Furthermore, even when firing is performed under any conditions other than the temperature range of the present invention, not only the battery capacity decreases, but also the value of the positive electrode resistance increases.
(Baking time) Of the baking time, the holding time at the predetermined temperature is preferably at least 1 hour, more preferably 5 to 15 hours. If it is less than 1 hour, the lithium nickel manganese composite oxide may not be sufficiently produced.

(Calcination)
In the firing step, particularly when lithium hydroxide or lithium carbonate is used as the lithium compound, it is lower than the firing temperature and at a temperature of 350 to 800 ° C. for about 1 to 10 hours, preferably before firing. It is preferable to hold for 3 to 6 hours and calcine, and subsequently to fire at 800 to 1000 ° C. That is, it is preferable to calcine at the reaction temperature of lithium hydroxide or lithium carbonate and the heat-treated particles. In this case, if the reaction temperature is maintained in the vicinity of the reaction temperature of lithium hydroxide or lithium carbonate, lithium is sufficiently diffused into the heat-treated particles, and a uniform lithium nickel manganese composite oxide can be obtained.

(Baking atmosphere)
The atmosphere during firing is an oxidizing atmosphere, preferably an atmosphere having an oxygen concentration of 18 to 100% by volume, and particularly preferably a mixed atmosphere of oxygen having the above oxygen concentration and an inert gas. That is, it is preferable to carry out in air | atmosphere-oxygen stream. If the oxygen concentration is less than 18% by volume, the oxidation may not be sufficient and the crystallinity of the lithium nickel manganese composite oxide may not be sufficient.

  The furnace used for firing is not particularly limited as long as it can be heated in the atmosphere to an oxygen stream, but an electric furnace that does not generate gas is preferable, and a batch type or continuous type furnace is used. It is done.

(Disintegration)
The lithium nickel manganese composite oxide particles obtained by firing may be aggregated or slightly sintered. In this case, it may be crushed, whereby a lithium nickel manganese composite oxide, that is, the positive electrode active material of the present invention can be obtained. Note that pulverization means that mechanical energy is applied to an aggregate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. This is an operation of separating the secondary particles and loosening the aggregates.

(3) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention employs a positive electrode using the positive electrode active material for non-aqueous electrolyte secondary battery of (2), as shown in FIG. is there.

  Since such a positive electrode is adopted, a battery having a high initial discharge capacity of 150 mAh / g or more and a low positive electrode resistance is obtained, and the effect that the thermal stability and safety can be increased can be obtained.

First, the structure of the nonaqueous electrolyte secondary battery of the present invention will be described.
The non-aqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as the secondary battery of the present invention) is a positive electrode material for the non-aqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as the positive electrode active material of the present invention). The structure is substantially the same as that of a general non-aqueous electrolyte secondary battery.

  Specifically, the secondary battery of the present invention has a structure including a case, and a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator accommodated in the case. More specifically, a positive electrode and a negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and a positive electrode current collector of the positive electrode and a positive electrode terminal connected to the outside are provided. The secondary battery of the present invention is formed by connecting the negative electrode current collector of the negative electrode and the negative electrode terminal communicating with the outside using a current collecting lead or the like, and sealing the case to the case. It is.

In addition, it cannot be overemphasized that the structure of the secondary battery of this invention is not limited to the said example, Moreover, the external shape can employ | adopt various shapes, such as a cylinder shape and a laminated form. Below, each part which comprises the secondary battery of this invention is demonstrated (positive electrode).
Using the positive electrode active material for a non-aqueous electrolyte secondary battery obtained as described above, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.

  First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and activated carbon and a target solvent such as viscosity adjustment are added as necessary, and this is kneaded to prepare a positive electrode mixture paste. . At that time, the mixing ratio in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery. When the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 to 95 parts by mass, and the content of the conductive material is the same as the positive electrode of a general non-aqueous electrolyte secondary battery. It is desirable that the content of the binder is 1 to 20 parts by mass and the content of the binder is 1 to 20 parts by mass.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be used.

  In producing the positive electrode, as the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, and the like), and carbon black materials such as acetylene black and ketjen black can be used.

  The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, and polyacrylic are used. An acid can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(3-b) Negative electrode made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of inserting and extracting lithium ions, mixed with a binder, and added with a suitable solvent to form a paste The composite material is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(3-c) Separator A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains an electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

(3-d) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate are used alone or in admixture of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(3-e) Shape and Configuration of Battery The nonaqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator, and the nonaqueous electrolytic solution that have been described above includes various types such as a cylindrical shape and a laminated shape. It can be made into a shape.

  In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the nonaqueous electrolyte secondary battery. .

(Characteristics of the secondary battery of the present invention)
The secondary battery of the present invention has the above-described configuration and uses the positive electrode as described above. Therefore, a high initial discharge capacity of 150 mAh / g or more and a low positive electrode resistance are obtained, and a high capacity and a high output are obtained. Become. Moreover, it can be said that the thermal stability is high and the safety is also excellent in comparison with a positive electrode active material of a conventional lithium cobalt oxide or lithium nickel oxide.

(Use of the secondary battery of the present invention)
The non-aqueous electrolyte secondary battery of the present invention is suitable for the power source of small portable electronic devices (such as notebook personal computers and cellular phone terminals) that always require a high capacity.

  The secondary battery of the present invention is also suitable for a battery as a power source for driving a motor that requires high output. As batteries become larger, it becomes difficult to ensure safety, and expensive protection circuits are indispensable. On the other hand, the non-aqueous electrolyte secondary battery of the present invention has excellent safety without increasing the size of the battery, so that not only ensuring safety but also an expensive protection circuit is possible. Can be simplified and the cost can be reduced. Furthermore, since it is possible to reduce the size and increase the output, it is suitable as a power source for transportation equipment that is restricted by the mounting space.

The average particle size and particle size distribution of the composite hydroxide produced by the method of the present invention and the positive electrode active material produced by the method of the present invention using this composite hydroxide as a raw material were confirmed.
Moreover, about the secondary battery which has the positive electrode manufactured using the positive electrode active material manufactured by the method of this invention, the performance (initial discharge capacity, cycle capacity maintenance factor, positive electrode resistance ratio) was confirmed.
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Measurement of average particle size and particle size distribution)
The average particle size and particle size distribution ([(d90-d10) / average particle size] value) of the composite hydroxide and the positive electrode active material are measured using a laser diffraction scattering type particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., Microtrac HRA). It is calculated from the volume integrated value measured by using.
Further, the crystal structure was also confirmed by X-ray diffraction measurement (X'Pert PRO, manufactured by Panalical).
The composition of the obtained composite hydroxide and positive electrode active material was confirmed by ICP emission spectroscopy after dissolving the sample.

(Alkalinity evaluation)
2 g of the obtained positive electrode active material was placed in 100 cc of water at 25 ° C., stirred for 1 minute, measured for pH value when allowed to stand for 5 minutes, and evaluated for alkalinity.

(Battery evaluation)
The obtained positive electrode active material for a non-aqueous electrolyte secondary battery was evaluated by preparing a battery and measuring the charge / discharge capacity as follows. 82.5 mg of a positive electrode active material for a non-aqueous electrolyte secondary battery, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. A positive electrode (evaluation electrode) (1) shown in FIG. The produced positive electrode (1) was dried in a vacuum dryer at 120 ° C. for 12 hours. And using this positive electrode (1), 2032 type coin battery (B) was produced in the glove box of Ar atmosphere where the dew point was controlled at -80 degreeC. Lithium metal having a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode (2), and an equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting electrolyte (electrolyte) Toyama Pharmaceutical Co., Ltd.) was used. As the separator (3), a polyethylene porous film having a film thickness of 25 μm was used. The coin battery (B) has a gasket (4) and is assembled into a coin-shaped battery with a positive electrode can (5) and a negative electrode can (6).

The manufactured coin battery (B) is left for about 24 hours after assembly, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is 0.1 mA / cm ² and the cut-off voltage is 4.3 V. A charge / discharge test was carried out to measure the discharge capacity when the battery was discharged until the cut-off voltage reached 3.0 V after charging for 1 hour. A multi-channel voltage / current generator (manufactured by Advantest Corporation, R6741A) was used for the measurement of the charge / discharge capacity.

  Moreover, resistance value was measured by the alternating current impedance method using the coin battery (B) charged with the charge potential of 4.1V. For the measurement, a Nyquist plot shown in FIG. 9 is obtained by using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron). Since the plot is expressed as the sum of the characteristic curve indicating the solution resistance, the negative electrode resistance and the capacity, and the positive electrode resistance and the capacity, the fitting calculation is performed using an equivalent circuit. The ratio with the value of the positive electrode resistance was defined as the positive electrode resistance ratio.

Example 1
[Composite hydroxide particle production process]
The composite hydroxide particles were prepared as follows using the method of the present invention.
First, the temperature in the tank was set to 40 ° C. while stirring by adding half the amount of water in the reaction tank (34L), and a nitrogen gas was passed through the reaction tank to form a non-oxidizing atmosphere. At this time, the oxygen concentration in the reaction vessel space was 2.0%.

  Appropriate amounts of 25% by mass aqueous sodium hydroxide and 25% by mass ammonia water were added to the water in the reaction vessel, and the pH of the reaction solution in the vessel was adjusted to a value of 12.6 based on the liquid temperature of 25 ° C. The ammonia concentration in the reaction solution was adjusted to 10 g / L.

(Nucleation process)
Next, nickel sulfate, manganese sulfate, and sodium tungstate were dissolved in water to form a 1.9 mol / L mixed aqueous solution. In this mixed aqueous solution, the element molar ratio of each metal was adjusted to be Ni: Mn: W = 0.50: 0.50: 0.005.
The mixed aqueous solution was added to the reaction solution in the reaction vessel at 88 ml / min. At the same time, 25 mass% ammonia water and 25 mass% sodium hydroxide aqueous solution are also added to the reaction liquid in the reaction tank at a constant rate, and the ammonia temperature in the reaction liquid is maintained at the above value, and the liquid temperature is 25 ° C. standard. Then, crystallization was carried out for 2 minutes and 30 seconds while controlling the pH value to 12.6 (nucleation pH value) to effect nucleation.

(Particle growth process)
Thereafter, only the supply of the 25 mass% sodium hydroxide aqueous solution was temporarily stopped until the pH value of the reaction solution reached 11.6 (particle growth pH value) on the basis of the liquid temperature of 25 ° C.
After the pH value of the reaction solution reached 11.6 on the basis of the liquid temperature of 25 ° C., the supply of the 25 mass% sodium hydroxide aqueous solution was restarted again as the pH value to be measured based on the liquid temperature of 25 ° C. While controlling at 11.6, crystallization was continued for 2 hours to perform particle growth.

  Crystallization was stopped when the reaction tank was full, and stirring was stopped and the mixture was allowed to stand to promote precipitation of the product. Then, after extracting a half amount of the supernatant from the reaction tank, crystallization was resumed, and the mixed aqueous solution to be supplied after crystallization was carried out for 1.5 hours (amount of supply relative to the total amount of metal elements: 87.6 mol%). Switch to a 1.9 mol / L mixed aqueous solution adjusted so that the metal element molar ratio is Ni: Mn: W = 0.30: 0.70: 0.005, and add at 88 ml / min for 0.5 hours. After continuing the crystallization (total 4 hours), the crystallization was terminated. The product was washed with water, filtered, and dried to obtain particles.

The obtained particles were composite hydroxide particles represented by Ni _0.449 Mn _0.547 W _0.004 (OH) _{2 + α} (0 ≦ α ≦ 0.5).

  As shown in Table 1, when the particle size distribution of the composite hydroxide particles was measured, the average particle size was 4.0 μm, and the ([(d90−d10) / average particle size] value was 0.47. It was.

  Moreover, it confirmed that it was a spherical secondary particle from the SEM photograph which is a SEM (Hitachi High-Technologies scanning electron microscope S-4700) observation result of the obtained composite hydroxide particle. Further, when EDX ray analysis of the cross section of the secondary particles was performed using STEM (scanning transmission electron microscope HD2300A manufactured by Hitachi High-Technologies Corporation), the thickness of the outer peripheral portion having a high Mn / Ni ratio was 14. It was 5%.

(Cathode active material manufacturing process)
The composite hydroxide particles were heat-treated at 700 ° C. for 12 hours in the air atmosphere, and then lithium carbonate was weighed so that Li / M = 1.35, and mixed with the heat-treated composite hydroxide particles. Formed. Mixing was performed using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)).
The obtained mixture was calcined at 760 ° C. for 4 hours in air (oxygen: 21% by volume), then calcined at 900 ° C. for 10 hours, and further pulverized to obtain a positive electrode active material.

As shown in FIG. 5, when the particle size distribution of the obtained positive electrode active material was measured, the average particle size was 4.3 μm, and the [(d90-d10) / average particle size] value was 0.56. .
Moreover, when SEM observation of the positive electrode active material was performed by the same method as that for the composite hydroxide particles, it was confirmed that the obtained positive electrode active material had a substantially spherical shape and a uniform particle size.

  Further, when the obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu—Kα ray, it was confirmed to be a hexagonal layered crystal lithium nickel manganese composite oxide single phase.

The positive electrode active material has a composition of 9.47% by mass of Li, 26.6% by mass of Ni, 30.4% by mass of Mn, 0.74% by mass of W by chemical analysis, and Li _1.35. It was confirmed that Ni _0.449 Mn _0.547 W _0.004 O ₂ .

  The positive electrode active material had a pH value of 10.9. Further, the ratio of the Mn / Ni ratio of the surface layer portion to the internal Mn / Ni ratio (SMN / IMN) was 1.5 when EDX analysis was performed in the same manner as the composite hydroxide particles.

(Battery evaluation)
A secondary battery having a positive electrode formed using the positive electrode active material was subjected to a charge / discharge test. As shown in Table 2, the initial discharge capacity of the secondary battery was 168.5 mAh / g. . The positive electrode resistance ratio was 0.62.

  Hereinafter, about Examples 2-8 and Comparative Examples 1-6, only the substance and conditions which were changed with the said Example 1 are shown. The results of each evaluation of Examples 2 to 8 and Comparative Examples 1 to 6 are shown in Table 1.

(Example 2)
The composition of the mixed aqueous solution was changed from Ni: Co: Mn: Zr: W = 0.55: 0.22: 0.22: 0.005: 0.005 to Ni: Co: Mn: Zr: W = 0.33: 0. .33: 0.33: 0.005: 0.005: A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except that the firing temperature was 850 ° C. evaluated. The particles obtained by crystallization were a composite hydroxide represented by Ni _0.496 Co _0.247 Mn _0.247 Zr _0.005 W _0.005 (OH) _{2 + α} (0 ≦ α ≦ 0.5). It was a particle. The obtained positive electrode active material was found to have a Li analysis of 7.63 wt%, Ni 28.8 wt%, Co 14.5 wt%, Mn 13.5 wt%, and Zr 0.42 by chemical analysis. It was confirmed that the composition was wt% and W was 0.84 wt%, and Li _1.1 Ni _0.50 Co _0.25 Mn _0.25 Zr _0.005 W _0.005 O ₂ .

  The ratio (SMN / IMN) of the Mn / Ni ratio in the surface layer portion and the internal Mn / Ni ratio was 1.7 when the EDX analysis was performed in the same manner as the composite hydroxide particles. FIG. 5 shows an SEM photograph of the obtained composite hydroxide particle, and FIG. 6 shows an SEM photograph of the obtained positive electrode active material.

(Example 3)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that mixing was performed so that Li / M = 1.05.

Example 4
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that mixing was performed so that Li / M = 1.15.

(Example 5)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that the firing condition was 925 ° C. for 10 hours.

(Example 6)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that the calcining conditions were changed to 400 ° C. for 10 hours.

(Example 7)
A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that calcination was not carried out at 850 ° C. for 10 hours.

(Example 8)
Crystallization was performed for 2 hours in a mixed solution in which the elemental molar ratio of each metal was Ni: Co: Mn: Zr: W = 0.66: 0.165: 0.165: 0.005: 0.005, and the reaction vessel When the inside is full, the crystallization is stopped and the stirring is stopped and the mixture is allowed to stand. After extracting a half amount of the supernatant from the reaction vessel, the mixed aqueous solution to be supplied has an element molar ratio of Ni: Co: After switching to a mixed aqueous solution adjusted to be Mn: Zr: W = 0.33: 0.33: 0.33: 0.005: 0.005 and continuing crystallization for 2 hours (total 4 hours), A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that the crystallization was completed.

Example 9
Crystals for 2 hours are adjusted so that the molar ratio of metal elements in the mixed aqueous solution is Ni: Co: Mn: Zr: W = 0.85: 0.1525: 0.1525: 0.005: 0.005. After crystallization and particle growth, when the reaction tank is full, crystallization is stopped, stirring is stopped and the mixture is left standing, and half of the supernatant liquid is extracted from the reaction tank, and then crystallization is resumed. In the mixed aqueous solution supplied after crystallization for 1.5 hours, the element molar ratio of each metal is Ni: Co: Mn: Zr: W = 0.33: 0.33: 0.33: 0.005. : Switched to a mixed aqueous solution adjusted to 0.005, and continued to crystallize for 0.5 hours to obtain a composite hydroxide, in the same manner as in Example 2, for a non-aqueous electrolyte secondary battery A positive electrode active material was obtained and evaluated.

(Comparative Example 1)
In the composite hydroxide production process, the mixed aqueous solution is prepared so that the metal element has a molar ratio of Ni: Co: Mn: Zr: W = 0.396: 0.247: 0.247: 0.005: 0.005. A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that it was prepared and supplied until completion of crystallization and the composition was not changed.

(Comparative Example 2)
Crystallization was performed for 2 hours in a mixed solution in which the elemental molar ratio of each metal was Ni: Co: Mn: Zr: W = 0.518: 0.236: 0.236: 0.005: 0.005, and the reaction vessel When the inside is full, the crystallization is stopped and the stirring is stopped and the mixture is allowed to stand. After half of the supernatant is withdrawn from the reaction vessel, the crystallization is resumed for 1.75 hours (with respect to the total amount of metal elements supplied). (Supply amount: 93.8 mol%) The mixed aqueous solution to be supplied at the time of crystallization has an element molar ratio of each metal of Ni: Co: Mn: Zr: W = 0.33: 0.33: 0.33: 0. 0.005: A positive electrode for a non-aqueous electrolyte secondary battery in the same manner as in Example 2 except that the mixed aqueous solution was adjusted to 0.005 and crystallized for 0.25 hours to obtain a mixed hydroxide. An active material was obtained and evaluated.

(Comparative Example 3)
In the composite hydroxide production process, the mixed aqueous solution is prepared so that the metal elements are in a molar ratio of Ni: Co: Mn: Zr: W = 0.594: 0.198: 0.198: 0.005: 0.005. A positive electrode active material for a non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 9 except that it was prepared and supplied until completion of crystallization and the composition was not changed.

(Comparative Example 4)
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that the firing conditions were changed to 1050 ° C. for 10 hours.

(Comparative Example 5)
A positive electrode active material for a nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 2 except that Li / M = 0.90.

(Evaluation)
Since the composite hydroxide particles and the positive electrode active materials of Examples 1 to 8 are materials in which the composition inside the secondary particles according to the present invention is inclined, the alkalinity is kept low. In addition, non-aqueous electrolyte secondary batteries using these positive electrode active materials have high initial discharge capacity, excellent cycle characteristics, low positive electrode resistance, and have excellent characteristics. .

In Comparative Examples 1 and 3, there is no high Mn / Ni specific layer, and in Comparative Example 2, the thickness of the outer peripheral portion is less than 5% of the secondary particle diameter, and thus the alkalinity reduction effect is not exhibited.
In Comparative Examples 4 and 5, since the manufacturing process of the positive electrode active material did not comply with the present invention, positive electrode active materials having good characteristics could not be obtained, and non-aqueous electrolyte secondary batteries using these positive electrode active materials were positive electrodes The resistance has increased and the initial discharge capacity has deteriorated.

  From the above results, if the nickel cobalt manganese composite hydroxide particles and the positive electrode active material are produced using the production method of the present invention, the non-aqueous electrolyte secondary battery using this positive electrode active material has an initial discharge capacity. It can be confirmed that the battery has high characteristics, excellent cycle characteristics, low positive electrode resistance, and excellent characteristics.

The nonaqueous electrolyte secondary battery of the present invention is suitable for the power source of small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require a high capacity.
In addition, the nonaqueous electrolyte secondary battery of the present invention has excellent safety, and can be downsized and increased in output. Therefore, the nonaqueous electrolyte secondary battery is suitable as a power source for transportation equipment that is restricted by the mounting space.

Claims (11)

A precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery,
General _{formula: Ni x Mn y Co z M} t (OH) 2 + α (x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0.55,0 ≦ z ≦ 0.4,0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is represented by one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Hf, Ta, Mo, and W) Nickel manganese composite hydroxide,
The average particle diameter is 3 to 11 μm, the index indicating the spread of the particle size distribution [(d90-d10) / average particle diameter] is 0.55 or less, and the nickel manganese composite hydroxide is a plurality of primary particles. Is a spherical secondary particle formed by agglomeration, and has a multilayer structure in which the composition of the inside of the secondary particle is different from the composition of the outer periphery, and the Mn / Ni of the composition of the outer periphery is greater than the composition of the interior of the secondary particle. Nickel-manganese composite hydroxide particles characterized by a high ratio. Outer periphery general formula of the secondary _{particles: Ni x Mn y Co z (} OH) 2 + α (0 ≦ x ≦ 0.4,0 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 1.0,0 ≦ t ≦ 0.2, x + y + z + t = 1, 0 ≦ α ≦ 0.5, M is one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W The nickel manganese composite hydroxide particles according to claim 1, wherein the nickel manganese composite hydroxide is represented by   The nickel manganese composite hydroxide particles according to claim 1 or 2, wherein the outer peripheral portion has a thickness of 5 to 25% of a secondary particle diameter.   The nickel-manganese composite hydroxide particles according to claim 1, wherein the secondary particles have the additive element uniformly distributed and / or the surface thereof uniformly covered with the additive element. Depending on the crystallization reaction, the general formula: Ni _x M _y Co _z M _t (OH) _{2 + a} (x + y + z + t = 1, 0.3 ≦ x ≦ 0.7, 0.1 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is one or more selected from Al, Ti, V, Cr, Zr, Nb, Hf, Ta, Mo, W A manufacturing method for producing nickel manganese composite hydroxide particles that are precursors of a positive electrode active material for a non-aqueous electrolyte secondary battery represented by an additive element),
A nucleation aqueous solution containing at least a nickel-containing metal compound and a manganese-containing metal compound and an ammonium ion supplier is controlled so that the pH value becomes 12.0 to 14.0 based on a liquid temperature of 25 ° C. A nucleation process for nucleation,
The aqueous solution for particle growth containing nuclei formed in the nucleation step has a pH value of 10.5 to 12.0 and lower than the pH value in the nucleation step on the basis of a liquid temperature of 25 ° C. A particle growth step for growing the nucleus by controlling so that
And a Mn / Ni ratio of the liquid part of the aqueous solution in the outer peripheral part formation stage during crystallization is made higher than the liquid part of the aqueous solution in the inner formation stage. . 6. The method for producing nickel manganese composite hydroxide particles according to claim 5, wherein the composition ratio of metal ions contained in the liquid part of the aqueous solution in the outer peripheral part formation period is a composition ratio in the following general formula.
The general _{formula: Ni x Mn y Co z (} OH) 2 + α
(0 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.4, 0.3 ≦ z ≦ 1.0, 0 ≦ t ≦ 0.2, x + y + z + t = 1, 0 ≦ α ≦ 0.5, M is One or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W)   6. The Mn / Ni ratio of the liquid part of the aqueous solution is changed when a metal element amount of 10 to 90 mol% is supplied with respect to the total metal element amount supplied during crystallization. 6. The method for producing nickel manganese composite hydroxide particles according to 6. _{Formula: Li 1 + u Ni x Co} y Mn z M t O 2 (-0.05 ≦ u ≦ 0.50, x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0 .55, 0.1 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is one or more selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W A positive electrode active material composed of a lithium nickel cobalt manganese composite oxide composed of a hexagonal lithium-containing composite oxide having a layered structure and having an average particle diameter of 3 to 12 μm The non-aqueous system is characterized in that [(d90-d10) / average particle size], which is an index indicating the spread of the particle size distribution, is 0.60 or less and the alkalinity is pH = 10.6 to 11.5. Positive electrode active material for electrolyte secondary battery. _{Formula: Li 1 + u Ni x Mn} y Co z M t O 2 (-0.05 ≦ u ≦ 0.50, x + y + z + t = 1,0.3 ≦ x ≦ 0.7,0.1 ≦ y ≦ 0 .55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is one or more additive elements selected from Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W 8) and a method for producing a positive electrode active material comprising a lithium nickel manganese composite oxide comprising a hexagonal lithium-containing composite oxide having a layered structure, A composite hydroxide particle manufacturing step for obtaining the nickel manganese composite hydroxide particles by the manufacturing method described above, a heat treatment step for heat-treating the nickel-manganese composite hydroxide particles, and a lithium compound for the particles after the heat treatment A mixing step of mixing to form a lithium mixture; The mixture formed in the mixing step, method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery characterized in that it comprises a firing step of firing at a temperature of 800 ° C. to 1000 ° C. in an oxidizing atmosphere.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, wherein calcining is performed in advance at a temperature of 350 ° C. to 800 ° C. in the firing step.   A non-aqueous electrolyte secondary battery, wherein the positive electrode is formed of the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8.