JP7087379B2 - Transition metal-containing composite hydroxide particles and their production methods, as well as positive electrode active materials for non-aqueous electrolyte secondary batteries and their production methods. - Google Patents

Description

The present invention relates to a transition metal-containing composite hydroxide particle and a method for producing the same, and a positive electrode active material for a non-aqueous electrolyte secondary battery using the transition metal-containing composite hydroxide particle as a precursor and a method for producing the same.

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook personal computers, there is a strong demand for the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density. Further, it is strongly desired to develop a high output secondary battery as a power source for electric vehicles such as hybrid electric vehicles, plug-in hybrid electric vehicles, and battery-powered electric vehicles.

As a secondary battery satisfying such a requirement, there is a lithium ion secondary battery which is a kind of non-aqueous electrolyte secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, a non-aqueous electrolyte, and the like, and a material capable of desorbing and inserting lithium is used as an active material used as a material for the negative electrode and the positive electrode. .. As the non-aqueous electrolyte, a non-aqueous electrolyte solution obtained by dissolving a supporting salt, a lithium salt, in an organic solvent, a nonflammable solid electrolyte having ion conductivity, and the like are used.

Among these lithium ion secondary batteries, the lithium ion secondary battery using a lithium transition metal-containing composite oxide having a layered rock salt type structure or a spinel type structure as a positive electrode material has a high energy because a 4V class voltage can be obtained. As a battery with density, research and development are currently being actively carried out, and some of them are being put into practical use.

As the positive electrode material for such a lithium ion secondary battery, lithium cobalt composite oxide (LiCoO ₂ ) particles that are relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) particles that use nickel, which is cheaper than cobalt, and the like. Lithium Nickel Cobalt Manganese Composite Oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) Particles, Lithium Manganese Composite Oxide (LiMn ₂ O ₄ ) Particles Using Manganese, Lithium Nickel Manganese Composite Oxide (LiNi) Lithium transition metal-containing composite oxide particles such as _0.5 Mn _0.5 O ₂ ) particles have been proposed.

By the way, in order to obtain a lithium ion secondary battery having excellent cycle characteristics and output characteristics, the positive electrode active material, which is the positive electrode material of the non-aqueous electrolyte secondary battery, is composed of particles having a small particle size and a narrow particle size distribution. It is necessary to be there. This is because particles with a small particle size have a large specific surface area, and when used as a positive electrode active material, not only can a sufficient reaction area with the electrolytic solution be secured, but also the positive electrode is made thin, and lithium ions are formed. This is because the moving distance between the positive electrode and the negative electrode can be shortened, so that the positive electrode resistance can be reduced. Further, since the particles having a narrow particle size distribution can make the voltage applied to the particles uniform in the electrode, it is possible to suppress the decrease in battery capacity due to the selective deterioration of the particles.

In order to further improve the output characteristics, it is effective to form a space in which the electrolytic solution can penetrate inside the positive electrode active material. Since such a positive electrode active material can have a larger reaction area with an electrolytic solution than a positive electrode active material having a solid structure having the same particle size, it is possible to significantly reduce the positive electrode resistance. It becomes. It is known that the positive electrode active material inherits the properties of the transition metal-containing composite hydroxide particles as its precursor. That is, in order to obtain the above-mentioned positive electrode active material, it is necessary to appropriately control the particle size, particle size distribution, particle structure and the like of the transition metal-containing composite hydroxide particles which are the precursors thereof.

For example, Japanese Patent Application Laid-Open No. 2012-246199, Japanese Patent Application Laid-Open No. 2013-147416, and WO2012 / 131881 have two stages, a nuclear generation step mainly for nuclear formation and a particle growth step mainly for particle growth. A method for producing transition metal-containing composite hydroxide particles which are precursors of a positive electrode active material by a clearly separated crystallization reaction is disclosed. In these methods, by appropriately adjusting the pH value and the reaction atmosphere in the nucleation generation step and the particle growth step, the particle size distribution is narrow with a small particle size, and the central part with a low density consisting of fine primary particles and the plate shape. Alternatively, transition metal-containing composite hydroxide particles composed of a high-density outer shell portion composed of needle-shaped primary particles are obtained.

Further, in WO2014 / 181891, the pH value of the aqueous solution for nuclear formation containing at least a metal compound containing a transition metal and an ammonium ion feeder is controlled to be 12.0 to 14.0, and nuclear formation is performed. The pH value of the particle growth aqueous solution containing the generated nuclei is controlled to be lower than the pH value of the nucleation generation step and to be 10.5 to 12.0 for growth. An atmosphere in which a particle growth step is provided, the initial stage of the nucleation generation step and the particle growth step is set to a non-oxidizing atmosphere, and the atmosphere is switched to an oxidizing atmosphere at a predetermined timing in the particle growing step, and then switched to a non-oxidizing atmosphere again. A method for producing a transition metal-containing composite hydroxide particle, which comprises performing the control at least once, is disclosed. According to this method, it has a small particle size, a narrow particle size distribution, and a central portion formed by agglomeration of plate-like or needle-like primary particles, and is formed by agglomeration of fine primary particles on the outside of the central portion. It is possible to obtain transition metal-containing composite hydroxide particles having two laminated structures in which the formed low-density layer and the high-density layer formed by aggregating plate-shaped primary particles are alternately laminated.

The positive electrode active material using these transition metal-containing composite hydroxide particles as precursors has a small particle size, a narrow particle size distribution, and has a hollow structure or a multilayer structure having a space portion. Therefore, in a secondary battery using these positive electrode active materials, it is considered that the battery capacity, output characteristics and cycle characteristics can be improved at the same time. However, in the production methods described in these documents, it takes time to switch the reaction atmosphere in the particle growth step, so that it is necessary to temporarily stop the supply of the raw material aqueous solution during that period, and there is room for improvement in terms of productivity. There is. Further, the specific surface area of the positive electrode active material particles produced by the production methods of these documents is at most 3.0 m ² / g. In order to further improve the output characteristics, a method capable of controlling the specific surface area to a higher range is required. Furthermore, it is desired to control the specific surface area without lowering the tap density so as not to impair the filling property.

Japanese Unexamined Patent Publication No. 2012-246199 Japanese Unexamined Patent Publication No. 2013-147416 WO2012 / 131881 WO2014 / 181891

In view of the above problems, the present invention is a positive electrode active material having a high specific surface area and tap density and capable of simultaneously improving battery capacity, output characteristics, and cycle characteristics when a secondary battery is configured, and a positive electrode active material thereof. It is an object of the present invention to provide a transition metal-containing composite hydroxide particle as a precursor. In addition, the present invention is efficient in producing a positive electrode active material having such characteristics and a transition metal-containing composite hydroxide particle having a structure that brings about the characteristics of such a positive electrode active material in industrial scale production. The purpose is to provide a means for good production.

In the present invention, a reaction aqueous solution is formed by supplying a raw material aqueous solution containing at least a transition metal and an aqueous solution containing an ammonium ion feeder into a reaction vessel, and a positive electrode for a non-aqueous electrolyte secondary battery is formed by a crystallization reaction. The present invention relates to a method for producing a transition metal-containing composite hydroxide particle which is a precursor of an active material.

The method for producing transition metal-containing composite hydroxide particles of the present invention causes nucleation by controlling the pH value of the reaction aqueous solution at a liquid temperature of 25 ° C. to be in the range of 12.0 to 14.0. The pH value of the nucleation generation step to be performed and the reaction aqueous solution containing the nuclei obtained in the nucleation generation step at a liquid temperature of 25 ° C. is lower than the pH value of the nucleation generation step and is 10.5 to 12.0. It is provided with a particle growth step of growing the nucleus by controlling the pH to be within the range of.

In the method for producing transition metal-containing composite hydroxide particles of the present invention, the reaction atmosphere in the initial stages of the nucleation formation step and the particle growth step is adjusted to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less, and the particles are said. After the initial stage of the growth step, by introducing an oxidizing gas while continuing to supply the raw material aqueous solution, the reaction atmosphere is changed from the non-oxidizing atmosphere to an oxidizing atmosphere in which the oxygen concentration exceeds 5% by volume. By introducing a non-oxidizing gas while continuing to supply the raw material aqueous solution, the reaction atmosphere is switched from the oxidizing atmosphere to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less. Atmosphere control is performed twice or more.

In particular, in the method for producing transition metal-containing composite hydroxide particles of the present invention, the oxidizing gas and the non-oxidizing gas are introduced using a diffuser tube when the reaction atmosphere is switched. Further, the switching of the reaction atmosphere is defined by the ratio of the amount of metal added in the oxidizing atmosphere to the total amount of metal added in the particle growth step, and the ratio of the entire crystallization reaction in the oxidizing atmosphere. Is in the range of 3% to 30% with respect to the entire particle growth process, and the ratio of each crystallization reaction in the oxidizing atmosphere is 1% to 12.5% with respect to the entire particle growth process. Control so that it is within the range.

The transition metal-containing composite hydroxide particles have the general formula (A): Ni _x Mn _y Coz M _t (OH) _{2 + a} (x + y + _z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦. 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf , Ta, W), preferably having a composition represented by one or more additive elements).

After the particle growth step, it is preferable to further include a coating step of coating the transition metal-containing composite hydroxide particles with a compound containing the additive element M.

The transition metal-containing composite hydroxide particles of the present invention are transition metal-containing composite hydroxide particles that are precursors of a positive electrode active material for a non-aqueous electrolyte secondary battery, and are a plurality of plate-shaped primary particles and the plate-shaped primary particles. It consists of secondary particles formed by agglomeration of fine primary particles smaller than the primary particles.

In particular, in the transition metal-containing composite hydroxide particles of the present invention, the secondary particles have a central portion formed by aggregating the plate-shaped primary particles, and the plate-shaped primary particles are located outside the central portion. It has two or more laminated structures in which a low-density layer formed by aggregating particles and the fine primary particles and a high-density layer formed by agglomerating the plate-shaped primary particles are laminated.

The low-density layer includes a low-density portion formed by aggregating the fine primary particles and a high-density portion formed by agglomerating the plate-shaped primary particles. The high-density layer is connected to the central portion and / or other high-density layers by the high-density portion constituting the low-density layer.

The average particle size MV of the secondary particles is in the range of 1 μm to 15 μm, and [(d90-d10) / average particle size MV], which is an index showing the spread of the particle size distribution of the secondary particles, is 0. It is .65 or less.

The transition metal-containing composite hydroxide particles have the general formula (A): Ni _x Mn _y Coz M _t (OH) _{2 + a} (x + y + _z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦. 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf , Ta, W), preferably having a composition represented by one or more additive elements).

The additive element M may be present inside the secondary particles, but it is preferable that the additive element M covers the surface of the secondary particles.

The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is formed by a mixing step of mixing the transition metal-containing composite hydroxide particles and a lithium compound to form a lithium mixture, and the mixing step. It is characterized by comprising a firing step of firing the lithium mixture at a temperature in the range of 700 ° C. to 920 ° C. in an oxidizing atmosphere.

In the mixing step, the lithium mixture is adjusted so that the ratio of the sum of the atoms of metals other than lithium contained in the lithium mixture to the number of atoms of lithium is 1: 0.95 to 1.5. It is preferable to do so.

Prior to the mixing step, it is preferable to further include a heat treatment step of heat-treating the transition metal-containing composite hydroxide particles at a temperature in the range of 105 ° C to 750 ° C.

The positive electrode active material for a non-aqueous electrolyte secondary battery has a general formula (B): 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 ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is Mg, Ca, Al, Ti, V, Cr, Zr, It is preferably composed of hexagonal lithium nickel-manganesium composite oxide particles represented by one or more additive elements selected from Nb, Mo, Hf, Ta, and W) and having a porous structure.

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery composed of lithium transition metal-containing composite oxide particles, and is formed by aggregating a plurality of primary particles. It is composed of secondary particles. In particular, in the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the secondary particles have a porous structure, and specifically, the secondary particles are formed by the aggregated primary particles. The shell portion, the aggregated portion existing inside the outer shell portion, formed by the aggregated primary particles, and electrically conducting with the outer shell portion, and dispersed in the aggregated portion. It has a plurality of existing space parts.

The average particle size MV of the secondary particles is in the range of 1 μm to 15 μm, and [(d90-d10) / average particle size MV], which is an index showing the spread of the particle size distribution of the secondary particles, is 0. It is 0.7 or less.

The BET specific surface area of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is in the range of 1.5 m ² / g to 4.0 m ² / g, preferably 2.0 m ² / g or more. More preferably, it is 2.5 m ² / g or more.

The tap density of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is in the range of 1.0 g / cm ³ to 2.0 g / cm ³ , preferably 1.3 g / cm ³ or more. More preferably, it is 5 g / cm ³ or more.

The total area ratio of the plurality of spaces measured by observing the cross section of the secondary particles is in the range of 15% to 30% with respect to the cross-sectional area of the secondary particles, and is 20% or more. preferable.

The positive electrode active material for a non-electrolyte secondary battery of the present invention has a general formula (B): 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 ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is Mg, Ca, Al, Ti, V, Cr, Zr , Nb, Mo, Hf, Ta, W), preferably composed of lithium transition metal-containing composite oxide particles having a hexagonal crystal structure having a layered structure. ..

According to the present invention, a positive electrode active material for a non-aqueous electrolyte secondary battery capable of simultaneously improving battery capacity, output characteristics, and cycle characteristics when a non-aqueous electrolyte secondary battery is configured, and a precursor thereof. It is possible to provide a transition metal-containing composite hydroxide particle which is a body. Further, according to the present invention, it is possible to provide a secondary battery using this positive electrode active material as a positive electrode material. Further, according to the present invention, it is possible to provide a means for efficiently producing the positive electrode active material and the transition metal-containing composite hydroxide particles in industrial scale production. Therefore, the industrial significance of the present invention is extremely large.

In the present invention, the present invention is appropriate by controlling the ratio of the entire crystallization reaction in the oxidizing atmosphere and the ratio of each crystallization reaction in the oxidizing atmosphere within the scope of the present invention. As a porous structure, the BET specific surface area may be in the range of 1.5 m ² / g to 4.0 m ² / g, and the tap density may be in the range of 1.0 g / cm ³ to 2.0 g / cm ³ . In the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, when a plurality of positive surface active substances are obtained by changing the BET specific surface area in the same composition, the BET specific surface area S of the positive electrode active material and When the relationship of the tap density m of the positive electrode active material is shown by the following equation 1 by the minimum square method , the range of the inclination a is −0.15 <a <0.15.
m = aS + b ... (Equation 1)

FIG. 1 is a cross-sectional view schematically showing the structure of the transition metal-containing composite hydroxide particles of the present invention. FIG. 2 is a binarized image of a field emission scanning electron microscope photograph of Example 2 used for evaluating the total area ratio of the space portion of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention. be. FIG. 3 is a schematic cross-sectional view of a 2032 type coin battery used for battery evaluation. FIG. 4 is a schematic explanatory diagram of a measurement example of impedance evaluation and an equivalent circuit used for analysis.

The present inventors further improve the productivity and output characteristics of the positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter referred to as “positive electrode active material”) based on the prior art such as WO2014 / 18891. Diligent research was repeated.

As a result, in the particle growth step, the reaction atmosphere can be switched in a short time by supplying the atmosphere gas using the air diffuser, and when the reaction atmosphere is switched, the supply of the raw material aqueous solution is not stopped and the oxidizing property is oxidizable. It has been found that the crystallization reaction due to the atmosphere and the crystallization reaction due to the non-oxidizing atmosphere can be appropriately switched, and the time of these crystallization reactions can be appropriately controlled even if the time is shorter than before. Obtained.

Further, by such switching of the reaction atmosphere, the plate-shaped primary particles have a central portion formed by agglomeration, and the plate-shaped primary particles and the fine primary particles are agglomerated and formed on the outside of the central portion. It was found that it is possible to obtain transition metal-containing composite hydroxide particles having two or more laminated structures in which a low-density layer and a high-density layer formed by aggregating plate-shaped primary particles are laminated. ..

In particular, by controlling the time of the crystallization reaction due to the oxidizing atmosphere to be shorter than before, the low-density layer is formed by agglomerating the low-density portion formed by the agglomeration of fine primary particles and the agglomeration of plate-shaped primary particles. It can be configured by the high-density part. Therefore, the high-density layer of the transition metal-containing composite hydroxide particles can be connected to the central portion and / or other high-density layers by the high-density portion constituting the low-density layer.

Furthermore, by appropriately controlling the time of the crystallization reaction due to the oxidizing atmosphere and the time of the crystallization reaction due to the non-oxidizing atmosphere in the particle growth step, and appropriately controlling the sizes of the low density layer and the high density layer, the size of the low density layer and the high density layer is appropriately controlled. In the positive electrode active material using the transition metal-containing composite hydroxide particles as precursors, the secondary particles existed in the outer shell portion formed by the aggregated primary particles and inside the outer shell portion and aggregated. It can be provided with a structure composed of an agglomerated portion formed by the primary particles and electrically conducting with the outer shell portion, and a plurality of spatial portions dispersed and existing in the agglomerated portion. In other words, in the secondary particles constituting the positive electrode active material, a hollow structure in which the entire inside of the conventional outer shell portion is a hollow portion, or a predetermined or more that spreads in the circumferential direction between the outer shell portion and the central portion. Unlike a hollow structure in which a gap portion having a size is present, a structure in which a plurality of small space portions are dispersed can be obtained.

In particular, by controlling the number and size of these spaces to the extent that the tap density of the positive electrode active material is not reduced, the specific surface area of the positive electrode active material is improved by the presence of the spaces, and the area that can come into contact with the electrolytic solution. It is possible to obtain high-density secondary particles while increasing the number of particles, and to sufficiently develop the electrical conduction path inside the secondary particles to significantly reduce the internal resistance of the positive electrode active material. The present invention has been completed based on such findings.

1. 1. Transition metal-containing composite hydroxide particles (1) Structure of transition metal-containing composite hydroxide particles The transition metal-containing composite hydroxide particles of the present invention (hereinafter referred to as “composite hydroxide particles”) are non-aqueous electrolyte particles. It is a precursor of a positive electrode active material for a secondary battery, and is composed of a plurality of plate-shaped primary particles and secondary particles formed by aggregating fine primary particles smaller than the plate-shaped primary particles.

In particular, the secondary particles constituting the composite hydroxide particles of the present invention have a central portion formed by agglomeration of plate-shaped primary particles as shown in the conceptual diagram of FIG. 1, and are located outside the central portion. It has two or more laminated structures in which a low-density layer formed by aggregating plate-shaped primary particles and fine primary particles and a high-density layer formed by agglomerating plate-shaped primary particles are laminated.

In particular, the low-density layer constituting the composite hydroxide particles of the present invention includes a low-density portion formed by agglomeration of fine primary particles and a high-density portion formed by agglomeration of plate-shaped primary particles. .. More specifically, the low-density layer is between the surface of the aggregate of plate-shaped primary particles constituting the central portion and the surface of the aggregate of plate-shaped primary particles constituting the high-density layer, or two highs. Agglomerates of fine primary particles are deposited between the surfaces of the aggregates of plate-shaped primary particles constituting the density layer, but the surface of the aggregates of plate-shaped primary particles is uneven, so that the low-density layer is formed. , Substantially, the structure is formed by agglomerating both plate-shaped primary particles and fine primary particles.

Then, in the low-density layer, a part of the aggregate of the plate-shaped primary particles in the central portion and a part of the aggregate of the plate-shaped primary particles of the high-density layer, or a part of the plate-shaped primary of the two high-density layers. Some of the aggregates of particles are in contact with each other. With such a structure, the high density layer is connected to the central portion and / or other high density layer by the high density portion constituting the low density layer.

When such composite hydroxide particles are fired, the low-density layer shrinks while maintaining the connection between the high-density layers. Therefore, in the obtained positive electrode active material, the low-density portion is dispersed in the secondary particles as pores of an appropriate size, that is, a space portion, and in the positive electrode active material, the primary particles are aggregated in the circumferential direction. It is composed of an outer shell portion, a plurality of pores existing inside the outer shell portion, and an agglomerate portion of primary particles surrounding these pores. Between the outer shell portion and the aggregated portion of the primary particles existing inside the outer shell portion, and the inside of the aggregated portion of the primary particles are electrically conductive, and the cross-sectional area of the path is sufficient. Secured. As a result of the positive electrode active material being composed of such a porous structure, it is possible to maintain a high density while reducing the internal resistance of the positive electrode active material, and the battery performance of the secondary battery using this can be significantly improved. It will be possible to improve.

In the composite hydroxide particles, the low-density layer does not have to be formed over the entire outer side of the central portion or over the entire circumferential direction between the high-density layers, but is in a partially formed state. May be good. In this case as well, in the obtained positive electrode active material, the partial low-density layer contracts to form a plurality of spaces consisting of pores of appropriate size, and the aggregated portions of the primary particles are formed outside the spaces. It becomes a formed structure. Further, the central portion of the composite hydroxide particles may have a structure in which aggregates of a plurality of plate-shaped primary particles are connected, and a portion in which fine primary particles are aggregated inside the central portion of the composite hydroxide particles is formed. It may have a structure. Even in such a case, in the obtained positive electrode active material, a structure of secondary particles substantially composed of an outer shell portion, a space portion existing inside the outer shell portion, and an agglomerated portion is formed.

(2) Average particle size MV
In the composite hydroxide particles of the present invention, the average particle size MV of the secondary particles is adjusted to 1 μm to 15 μm, preferably 3 μm to 12 μm, and more preferably 3 μm to 10 μm. The average particle size MV of the secondary particles correlates with the average particle size MV of the positive electrode active material using the composite hydroxide particles as a precursor. Therefore, by controlling the average particle size MV of the secondary particles in such a range, the average particle size MV of the positive electrode active material using the composite hydroxide particles as a precursor can be controlled in a predetermined range. It will be possible.

In the present invention, the average particle size MV of the secondary particles means a volume-based average particle size (Mean Volume Diameter), and is obtained from, for example, a volume integrated value measured by a laser light diffraction / scattering type particle size analyzer. Can be done.

(3) Particle size distribution The composite hydroxide particles of the present invention have an index [(d90-d10) / average particle size MV] indicating the spread of the particle size distribution of 0.65 or less, preferably 0.55 or less. More preferably, it is adjusted to be 0.50 or less.

The particle size distribution of the positive electrode active material is strongly influenced by the composite hydroxide particles that are its precursor. Therefore, when composite hydroxide particles containing a large amount of fine particles and coarse particles are used as a precursor, the positive electrode active material also contains a large amount of fine particles and coarse particles, and a secondary battery using this is used. Safety, cycle characteristics and output characteristics cannot be sufficiently improved. On the other hand, if [(d90-d10) / average particle size MV] is adjusted to be 0.65 or less at the stage of the composite hydroxide particles, the positive electrode active material using this as a precursor is used. The particle size distribution can be narrowed, and the above-mentioned problems can be avoided. However, on the premise of industrial scale production, it is not realistic to use composite hydroxide particles having an excessively small [(d90-d10) / average particle size]. Therefore, in consideration of cost and productivity, the lower limit of [(d90-d10) / average particle size MV] is preferably about 0.25.

In addition, d10 is a particle size in which the number of particles in each particle size is accumulated from the smaller particle size side, and the cumulative volume is 10% of the total volume of all particles, and d90 is similarly a respective particle size. It means the particle size in which the number of particles in the above is accumulated from the side with the smaller particle size and the accumulated volume is 90% of the total volume of all the particles. Similar to the average particle size MV, d10 and d90 can be obtained from the volume integrated values measured by the laser light diffraction / scattering type particle size analyzer.

(4) Size of central part, low density layer, and high density layer In the composite hydroxide particles of the present invention, the outer diameter of the central part, the low density layer, and the high density layer with respect to the particle size of the secondary particles. By appropriately controlling the ratio of each size, the outer shell part formed by the agglomerated primary particles and the outer shell part existing inside the outer shell part and formed by the agglomerated primary particles, and with the outer shell part. A positive electrode active material composed of secondary particles composed of an electrically conductive agglomerated portion and a plurality of spatial portions dispersed in the agglomerated portion can be obtained.

In the composite hydroxide particles having the structure of the present invention, the average ratio of the outer diameter of the central portion to the particle diameter (hereinafter referred to as “central particle size ratio”) is preferably in the range of 10% to 30%. .. By controlling the central particle size ratio to such a range, the low-density layer and the high-density layer formed on the outer side thereof are formed to appropriate sizes, respectively, and the desired positive electrode active material is obtained. It is possible to obtain the structure. If the size of the central portion exceeds this range, it may not be possible to obtain a structure having a desired dispersed space portion inside in the obtained positive electrode active material.

When the size of each low-density layer is based on the thickness of the low-density layer, the average ratio of the thickness of each low-density layer to the particle size of the secondary particles (hereinafter, "low-density layer particle size"). The ratio) is preferably in the range of 2% to 10%, more preferably in the range of 5% to 10%.

When the size of each high-density layer is based on the thickness of the high-density layer, the average ratio of the thickness of each high-density layer to the particle size of the secondary particles (hereinafter, "high-density layer particle size"). The ratio) is preferably in the range of 2% to 10%, more preferably in the range of 5% to 10%.

By setting the respective low-density layer particle size ratio and high-density layer particle size ratio in this range, the secondary particles in the positive electrode active material obtained by using the composite hydroxide particles having such a structure as a precursor. It is possible to form a structure in which a plurality of spaces (pores) of appropriate size that are dispersed inside the space are formed. If the particle size ratio of each low-density layer is too small, a space having a sufficiently large size in the obtained positive electrode active material does not occur during firing of the composite hydroxide particles, and the structure is substantially the same as that of the solid structure. There is a possibility of becoming. On the contrary, if the particle size ratio of each low-density layer is too large, the low-density layer does not shrink so as to have a pore structure when the composite hydroxide particles are fired. There is a possibility that a large void exists between the part, the high-density layer, and the outer shell part, and the outer shell part and the agglomerated part inside are not sufficiently connected or integrated, and the desired structure cannot be obtained. There is. In this case, an electrical conduction path having a sufficient cross-sectional area is not formed between the outer shell portion and the internal agglomerated portion, and the effect of reducing the positive electrode resistance cannot be obtained.

If the particle size ratio of each high-density layer is too small, the predetermined structure of the secondary particles will not be maintained at the production stage or filling stage of the positive electrode active material and will be destroyed, or the size will be sufficient inside the secondary particles. There is a possibility that the space part of is not formed. On the other hand, if the particle size ratio of each high-density layer is too large, a space having a sufficient size is not formed inside the secondary particles when the composite hydroxide particles are fired, which is sufficient inside the secondary particles. Insufficient penetration of electrolytes and conductive aids may occur.

In the composite hydroxide particles of the present invention, two or more laminated structures in which a low-density layer and a high-density layer are laminated can be provided on the outside of the central portion. Preferably, the number of laminated structures is 2 to 5, more preferably 3 to 5, and even more preferably 3 to 4. If the number of laminated structures exceeds 5, each low-density layer is not formed to a sufficient size, and there is a high possibility that a positive electrode active material having a desired particle structure cannot be obtained. On the other hand, if only one laminated structure is used, the abundance ratio of the space portion is insufficient in the obtained positive electrode active material, and the desired characteristics such as sufficient specific surface area and low internal resistance cannot be obtained.

In the present invention, as long as the basic central portion, each low-density layer and the high-density layer have a predetermined size, basically, regardless of the number of laminated structures, such a structure is used. When the composite hydroxide particles are fired, a structure is obtained in which the central portion and the high-density layer are substantially integrated by sintering shrinkage, and a plurality of spatial portions generated by being dispersed inside are present. The space portion existing inside can communicate with the outside through the grain boundaries or voids between the primary particles forming the aggregate. Therefore, in such a structure, the electrical conduction path between the primary particles constituting the secondary particles is sufficiently secured while maintaining the structure of the obtained positive electrode active material as a whole, and the space portion and the space portion are formed. As a result of sufficient communication with the outside, it is possible to further reduce the positive electrode resistance.

In addition, the central particle size ratio, the low density layer particle size ratio, and the high density particle size ratio are obtained by scanning the cross section of the composite hydroxide particles with a scanning electron microscope such as an electric field emission scanning electron microscope (FE-SEM). Although it can be obtained by observing with (SEM), in the composite hydroxide particles, the overall shape is distorted and the shape of each layer is also complicated, so the thickness of each is observed by SEM. It is not easy to identify by. Therefore, the central particle size ratio, the low density layer particle size ratio, and the high density particle size ratio in the present specification are all metals added in the particle growth step in the manufacturing step of the composite hydroxide particles. It is theoretically obtained from the ratio of the total crystallization reaction in the non-oxidizing atmosphere or the oxidizing atmosphere in the particle growth step, which is defined by the ratio of the amount of metal added in the non-oxidizing atmosphere or the oxidizing atmosphere to the amount. Be done.

(5) Primary particles In the composite hydroxide particles of the present invention, the size of the plate-shaped primary particles constituting the high-density portion of the central portion, the high-density layer and the low-density layer, and the low-density portion of the low-density layer are determined. The size of the fine primary particles that make up the particles is determined by embedding composite hydroxide particles in a resin or the like and making it possible to observe the cross section by cross-section polisher processing, etc., and then using SEM such as FE-SEM for the cross section. When observed using, the difference is such that the difference in structure can be clearly grasped on the imaging.

In the composite hydroxide particles of the present invention, the plate-shaped primary particles are formed in a size having an average particle size in the range of 0.3 μm to 3 μm. Preferably, the size of the plate-shaped primary particles is in the range of 0.4 μm to 1.5 μm in average particle size. If the average particle size of the plate-shaped primary particles is less than 0.3 μm, the volume shrinkage of the plate-shaped primary particles also occurs in the low temperature region in the firing step for producing the positive electrode active material, so that the plate-shaped primary particles have a low density layer. Since the difference in volume shrinkage between the central portion and the high-density layer becomes small, it is possible that a sufficient number of spatial portions cannot be obtained inside the positive electrode active material. On the other hand, when the average particle size of the plate-shaped primary particles is larger than 3 μm, firing at a higher temperature is required in order to increase the crystallinity of the positive electrode active material in the firing step when producing the positive electrode active material, which is a composite. Sintering between the secondary particles constituting the hydroxide particles progresses, and it becomes difficult to set the average particle size MV and the particle size distribution of the positive electrode active material within a predetermined range.

In the composite hydroxide particles of the present invention, the fine primary particles are formed into a size sufficiently distinguishable from the plate-shaped primary particles by SEM observation or the like. In the imaging of SEM observation, it may be difficult to fully grasp the size, but the fine primary particles have an average particle size smaller than the average particle size of the plate-shaped primary particles, that is, the average particle size is , 0.01 μm to 0.3 μm, and the difference from the average particle size of the plate-shaped primary particles is 0.1 μm or more. Normally, the average particle size of the fine primary particles has a difference of 0.3 μm or more from the average particle size of the plate-shaped primary particles. If the average particle size of the fine primary particles is less than 0.01 μm, the thickness of the low density layer cannot be satisfactorily obtained. On the other hand, when the average particle size of the fine primary particles is larger than 0.3 μm, the volume shrinkage due to heating does not sufficiently proceed during the firing in the low temperature range in the firing step for producing the positive electrode active material, and the density is low. Since the difference in volume shrinkage between the layer and the central portion and the high-density layer becomes small, there is a possibility that a sufficiently large space portion is not formed inside the secondary particles of the positive electrode active material.

The shape of such fine primary particles may not be sufficiently grasped and specified even by SEM observation, and basically any shape can be taken, but a needle shape is preferable. This is because the needle-shaped primary particles have a one-dimensional directional shape, and when the particles are aggregated, a structure having many gaps, that is, a structure having a low density can be formed.

As described above, it is sufficient that the sizes of the fine primary particles and the plate-shaped primary particles are different enough to understand the difference between the layers or parts formed by the aggregation by SEM observation, and it is necessary to measure them concretely. There is no. In particular, for fine primary particles, the particle size may be too small to sufficiently grasp the shape. When both the shapes and sizes of the fine primary particles and the plate-shaped primary particles can be observed by SEM, they can be obtained as follows. That is, the maximum outer diameter (major axis diameter) of 10 or more fine primary particles or plate-shaped primary particles existing in the cross section of the secondary particles is measured, the average value is obtained, and this value is used in the secondary particles. The particle size of fine primary particles or plate-shaped primary particles. Next, for 10 or more secondary particles, the particle sizes of the fine primary particles and the plate-shaped primary particles are similarly determined. Finally, by obtaining the average particle size obtained for these secondary particles, the average particle size of the fine primary particles or the plate-shaped primary particles of the entire composite hydroxide particles is determined.

(4) Composition The composition of the composite hydroxide particles of the present invention is not limited as long as it has the above-mentioned structure, average particle size MV and particle size distribution, but the general formula (A): Ni _x Mn _y . Coz M _t (OH) _{2 + a} (x + y + _z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is a composite water represented by one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). It is preferably oxide particles. By using such composite hydroxide particles as a precursor, a positive electrode active material represented by the general formula (B) described later can be easily obtained, and higher battery performance can be realized.

In the composite hydroxide particles represented by the general formula (A), the composition range of nickel, manganese, cobalt and the additive element M constituting the composite hydroxide particles and their critical significance are represented by the general formula (B). It becomes the same as the positive electrode active material. Therefore, the description of these matters is omitted here.

2. 2. Method for Producing Transition Metal-Containing Composite Hydroxide Particles In the method for producing composite hydroxide particles of the present invention, at least an aqueous solution containing a transition metal and an aqueous solution containing an ammonium ion feeder are supplied into a reaction vessel. This is a method for producing a transition metal-containing composite hydroxide particle which is a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery by forming a reaction aqueous solution with water.

In particular, in the method for producing composite hydroxide particles of the present invention, the crystallization reaction is performed by adjusting the pH value of the reaction aqueous solution at a liquid temperature of 25 ° C. to the range of 12.0 to 14.0 to generate nuclei. The pH value of the reaction aqueous solution containing the nuclei obtained in the formation step and the nucleation step is lower than the pH value of the nucleation step and is 10.5 to 12.0. It is characterized by a clear distinction between the two stages of the particle growth process, which is controlled to grow the nucleus.

Further, by circulating an inert gas in the reaction vessel before the start of the nuclear formation step or at the start of the nuclear formation step, the reaction atmosphere at the initial stage of the nuclear formation step and the particle growth step has an oxygen concentration of 5% by volume or less. In the particle growth step, the reaction atmosphere is changed from the non-oxidizing atmosphere to the oxygen concentration by introducing the atmospheric gas using the diffuser tube while continuing the supply of the raw material aqueous solution. Atmosphere control that switches the reaction atmosphere from an oxidizing atmosphere to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less by reintroducing a non-oxidizing gas after switching to an oxidizing atmosphere exceeding 5% by volume. Is characterized by performing the above twice or more.

Further, at that time, the ratio of the total crystallization reaction in the oxidizing atmosphere, which is defined by the ratio of the amount of metal added in the oxidizing atmosphere to the total amount of metal added in the particle growth step, is applied to the entire particle growth step. On the other hand, it is controlled to be in the range of 3% to 30%, and the ratio of each crystallization reaction in the oxidizing atmosphere is controlled to be in the range of 1% to 12.5% with respect to the entire particle growth process. It is characterized by doing.

The method for producing composite hydroxide particles of the present invention is not limited by the composition as long as the above-mentioned structure, average particle size and particle size distribution can be realized, but is represented by the general formula (A). It can be suitably applied to composite hydroxide particles.

(1) Crystallization reaction In the method for producing composite hydroxide particles of the present invention, the crystallization reaction is clearly separated into two stages, a nucleus formation step mainly for nucleation and a particle growth step mainly for particle growth. At the same time, by adjusting the crystallization conditions in each step, in particular, in the particle growth step, while continuing to supply the raw material aqueous solution, the atmosphere gas is sent through the diffuser tube to switch the reaction atmosphere, as described above. It is possible to efficiently obtain composite hydroxide particles having a fine particle structure, an average particle size MV, and a particle size distribution.

[Nucleation process]
In the nucleation step, first, the transition metal compound which is the raw material in this step is dissolved in water to prepare an aqueous raw material solution. At the same time, an alkaline aqueous solution and an aqueous solution containing an ammonium ion feeder are supplied and mixed in the reaction vessel, and the pH value measured at a liquid temperature of 25 ° C. is 12.0 to 14.0, and the ammonium ion concentration is 3 g / g. A pre-reaction aqueous solution of L to 25 g / L is prepared. The pH value of the pre-reaction aqueous solution can be measured with a pH meter, and the ammonium ion concentration can be measured with an ion meter.

Next, the raw material aqueous solution is supplied while stirring the pre-reaction aqueous solution. As a result, a nucleation aqueous solution, which is a reaction aqueous solution in the nucleation step, is formed in the reaction vessel. Since the pH value of this aqueous solution for nucleation is in the above range, nucleation occurs preferentially in the nucleation step with almost no growth of nuclei. In the nucleation step, the pH value of the nucleation aqueous solution and the concentration of ammonium ions change with the nucleation, so an alkaline aqueous solution and an ammonia aqueous solution are supplied in a timely manner, and the pH value of the solution in the reaction vessel is 25. It is necessary to control the pH to be maintained in the range of 12.0 to 14.0 and the concentration of ammonium ions in the range of 3 g / L to 25 g / L on the basis of ° C.

In the nucleation step, it is necessary to circulate the inert gas in the reaction vessel and adjust the reaction atmosphere to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less. It is usually preferable to adjust the reaction atmosphere before starting the supply of the raw material aqueous solution. As a result, the central portion of the positive electrode active material using the composite hydroxide particles as a precursor has a solid structure, and it is possible to suppress a decrease in particle density due to the formation of a space portion.

In the nucleation step, by supplying an aqueous solution containing a raw material aqueous solution, an alkaline aqueous solution and an ammonium ion feeder to the nucleation aqueous solution, the generation of new nuclei is continuously continued. Then, when a predetermined amount of nuclei are generated in the nucleation aqueous solution, the nucleation step is terminated.

At this time, the amount of nucleation produced can be determined from the amount of the metal compound contained in the raw material aqueous solution supplied to the nucleation aqueous solution. The amount of nuclei produced in the nucleation step is not particularly limited, but in order to obtain composite hydroxide particles having a narrow particle size distribution, the metal contained in the raw material aqueous solution supplied through the nucleation step and the particle growth step. It is preferably 0.1 atomic% to 2 atomic%, more preferably 0.1 atomic% to 1.5 atomic%, based on the metal element in the compound. The reaction time in the nucleation step is usually about 0.2 minutes to 5 minutes.

[Particle growth process]
After the nucleation step is completed, the pH value of the nucleation aqueous solution in the reaction vessel is adjusted to 10.5 to 12.0 based on the liquid temperature of 25 ° C. to form a particle growth aqueous solution which is a reaction aqueous solution in the particle growth step. do. The pH value can also be adjusted by stopping the supply of the alkaline aqueous solution, but in order to obtain composite hydroxide particles with a narrow particle size distribution, the supply of all the aqueous solutions is temporarily stopped and the pH value is adjusted. Is preferable. Specifically, it is preferable to adjust the pH value by stopping the supply of all the aqueous solutions and then supplying the nucleation aqueous solution with an inorganic acid of the same type as the acid constituting the metal compound as a raw material.

Next, the supply of the raw material aqueous solution is restarted while stirring the particle growth aqueous solution. At this time, since the pH value of the aqueous solution for particle growth is in the above range, almost no new nuclei are generated, the nuclei (particles) grow, and composite hydroxide particles having a predetermined particle size are formed. To. Also in the particle growth step, the pH value and ammonium ion concentration of the aqueous solution for particle growth change with the growth of particles, so an alkaline aqueous solution and an aqueous ammonia solution are supplied in a timely manner to maintain the pH value and ammonium ion concentration within the above ranges. It is necessary to do.

In particular, in the method for producing composite hydroxide particles of the present invention, the reaction atmosphere is not created by introducing an atmospheric gas using an air diffuser while continuing to supply the raw material aqueous solution in the middle of the particle growth step. After switching from the oxidizing atmosphere to the oxidizing atmosphere where the oxygen concentration exceeds 5% by volume, the atmosphere is controlled twice or more by switching again from this oxidizing atmosphere to the non-oxidizing atmosphere where the oxygen concentration is 5% by volume or less. conduct. This makes it possible to obtain composite hydroxide particles having the above-mentioned particle structure.

In the particle growth step, an inert gas and / or an oxidizing gas is circulated in the reaction aqueous solution in the reaction vessel using an air diffuser, and the reaction atmosphere is changed from an oxidizing atmosphere having an oxygen concentration higher than 5% by volume to an oxygen concentration. It is preferable to quickly switch to a non-oxidizing atmosphere of 5% by volume or less, or from a non-oxidizing atmosphere to an oxidizing atmosphere. As the method for supplying the inert gas and / or the oxidizing gas to the reaction aqueous solution in the reaction tank, it is possible to supply the inert gas and / or the oxidizing gas to the space in the reaction tank in contact with the reaction aqueous solution, but the method of supplying the inert gas and / or the oxidizing gas directly into the reaction aqueous solution is adopted. Is preferable. As a result, it is possible to shorten the time for switching the atmosphere, and it is possible to appropriately design the outer diameter of the central portion and the sizes of the respective low-density layers and high-density layers, and in particular, the size of the low-density layer. Even when the size is designed to be small, the reaction time for that purpose can be easily controlled.

The present invention is characterized in that the atmosphere is switched at least four times (similar atmosphere control is performed at least twice) as described above during the crystallization reaction. In this case, from the inside of the secondary particles constituting the composite hydroxide particles, the central portion, the first low-density layer, the first high-density layer, the second low-density layer, and the second high-density layer (in this order). A laminated structure consisting of an outer shell portion) is formed. Further, by adding this atmosphere switching twice more (similar atmosphere control once each), it is possible to increase the laminated structure by one. For example, by switching the atmosphere 6 times (similar atmosphere control 3 times), the central portion, the first low-density layer, and the first are ordered from the inside of the secondary particles constituting the composite hydroxide particles. A laminated structure including a high-density layer, a second low-density layer, a second high-density layer, a third low-density layer, and a third high-density layer (outer shell portion) is formed.

In such a method for producing composite hydroxide particles, metal ions are precipitated as nuclei or primary particles in the nucleation generation step and the particle growth step. Therefore, the ratio of the liquid component to the metal component in the aqueous solution for nucleation and the aqueous solution for particle growth increases. As a result, the concentration of the raw material aqueous solution apparently decreases, and the growth of the composite hydroxide particles may be stagnant, especially 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 of the aqueous particle growth solution to the outside of the reaction vessel after the nucleation step is completed and during the particle growth step. Specifically, the supply and stirring of the aqueous solution containing the raw material aqueous solution, the alkaline aqueous solution and the ammonium ion feeder are temporarily stopped, and the nuclei and the composite hydroxide particles in the particle growth aqueous solution are precipitated to form the particle growth aqueous solution. It is preferable to drain the supernatant liquid. By such an operation, the relative concentration of the mixed aqueous solution in the aqueous solution for particle growth can be increased, so that the stagnation of particle growth is prevented and the particle size distribution of the obtained composite hydroxide particles is controlled in a suitable range. Not only can this be done, but the density of the secondary particles as a whole can also be improved.

[Diameter control of composite hydroxide particles]
The particle size of the composite hydroxide particles obtained as described above is controlled by the time of the particle growth step and the nucleation step, the pH value of the nucleation aqueous solution and the particle growth aqueous solution, and the supply amount of the raw material aqueous solution. Can be done. For example, by performing the nucleation generation step at a high pH value or by prolonging the time of the particle generation step, the amount of the metal compound contained in the supplied raw material aqueous solution is increased, and the amount of nucleation is increased. The particle size of the composite hydroxide particles to be obtained can be reduced. On the contrary, by suppressing the amount of nucleation produced in the nucleation step, the particle size of the obtained composite hydroxide particles can be increased.

[Another embodiment of the crystallization reaction]
In the method for producing composite hydroxide particles of the present invention, a component adjusting aqueous solution adjusted to a pH value and ammonium ion concentration suitable for the particle growth step is prepared separately from the nucleus forming aqueous solution, and the component adjusting aqueous solution is prepared. Aqueous solution for nucleation after the nucleation step, preferably an aqueous solution for nucleation after the nucleation step in which a part of the liquid component is removed is added and mixed, and this is used as an aqueous solution for particle growth for particle growth. The process may be performed.

In this case, since the nucleation step and the particle growth step can be separated more reliably, the reaction aqueous solution in each step can be controlled to the optimum state. In particular, since the pH value of the aqueous solution for particle growth can be controlled in the optimum range from the start of the particle growth step, the particle size distribution of the obtained composite hydroxide particles can be made narrower.

(2) Supply aqueous solution In the method for producing composite hydroxide particles of the present invention, a raw material aqueous solution containing at least a transition metal, preferably nickel and manganese, or nickel, manganese and cobalt, and ammonium ions are contained in the reaction vessel. A reaction aqueous solution is formed by supplying an aqueous solution containing a feeder, and a composite hydroxide particle is obtained by a crystallization reaction while adjusting the pH value of the reaction aqueous solution to a predetermined range with a pH adjusting agent.

a) Aqueous solution of raw material In the present invention, the ratio of the metal element in the aqueous solution of the raw material is generally the composition ratio of the obtained composite hydroxide particles. Therefore, it is necessary to appropriately adjust the content of each metal element in the raw material aqueous solution according to the composition of the target composite hydroxide particles. For example, when trying to obtain the composite hydroxide particles represented by the above-mentioned general formula (A), the ratio of the metal element in the raw material aqueous solution is set to Ni: Mn: Co: M = x: y: z. Adjusted to be t (however, x + y + z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1). It is necessary to do. However, when the additive element M is introduced in another step as described above, the additive element M is not contained in the raw material aqueous solution. It is also possible to change the presence or absence of the additive element M added or the content ratio of the transition metal or the additive element M in the nucleation step and the particle growth step.

The transition metal compound for preparing the raw material aqueous solution is not particularly limited, but it is preferable to use water-soluble nitrates, sulfates, hydrochlorides, etc. from the viewpoint of ease of handling, and it is preferable to use water-soluble nitrates, sulfates, hydrochlorides, etc. From the viewpoint of preventing contamination, it is particularly preferable to use sulfate.

Further, the additive element M (M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) in the composite hydroxide particles). In the case of containing, a water-soluble compound is also preferable as the compound for supplying the additive element M, for example, magnesium sulfate, calcium sulfate, aluminum sulfate, titanium sulfate, ammonium peroxotitanate, titanium oxalate. Potassium, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, zirconium sulfate, niobium oxalate, ammonium molybdate, hafnium sulfate, sodium tantalate, sodium tungstate, ammonium tungstate and the like can be preferably used.

The concentration of the raw material aqueous solution is the total of the metal compounds, preferably 1 mol / L to 2.6 mol / L, and more preferably 1.5 mol / L to 2.2 mol / L. If the concentration of the raw material aqueous solution is less than 1 mol / L, the amount of crystallized material per reaction vessel is small, so that the productivity is lowered. On the other hand, if the concentration of the mixed aqueous solution exceeds 2.6 mol / L, the saturation concentration at room temperature is exceeded, so that crystals of each metal compound may reprecipitate and clog the piping or the like.

The above-mentioned metal compound does not necessarily have to be supplied to the reaction vessel as a raw material aqueous solution. For example, when a crystallization reaction is carried out using a metal compound that reacts when mixed to produce a compound other than the target compound, the total concentration of the total metal compound aqueous solution is within the above range. An aqueous solution of a metal compound may be prepared and supplied into the reaction vessel at a predetermined ratio as an aqueous solution of individual metal compounds.

As for the supply amount of the raw material aqueous solution, the concentration of the product in the particle growth aqueous solution is preferably 30 g / L to 200 g / L, more preferably 80 g / L to 150 g / L at the end of the particle growth step. To do so. If the concentration of the product is less than 30 g / L, the aggregation of the primary particles may be insufficient. On the other hand, if it exceeds 200 g / L, the aqueous metal salt solution for nucleation or the aqueous metal salt solution for particle growth may not sufficiently diffuse in the reaction vessel, and the particle growth may be biased.

b) Alkaline aqueous solution The alkaline aqueous solution for adjusting the pH value in the reaction aqueous solution is not particularly limited, and a general alkaline metal hydroxide aqueous solution such as sodium hydroxide or potassium hydroxide can be used. Although the alkali metal hydroxide can be added directly to the reaction aqueous solution, it is preferable to add it as an aqueous solution because of the ease of pH control. In this case, the concentration of the aqueous alkali metal hydroxide solution is preferably 20% by mass to 50% by mass, more preferably 20% by mass to 30% by mass. By limiting the concentration of the aqueous alkali metal solution to such a range, it is possible to suppress the amount of solvent (amount of water) supplied to the reaction system and prevent the pH value from increasing locally at the addition position. , It becomes possible to efficiently obtain composite hydroxide particles having a narrow particle size distribution.

The method for supplying the alkaline aqueous solution is not particularly limited as long as the pH value of the reaction aqueous solution does not rise locally and is maintained within a predetermined range. For example, the reaction aqueous solution may be sufficiently agitated and supplied by a pump capable of controlling the flow rate, such as a metering pump.

c) Aqueous solution containing an ammonium feeder The aqueous solution containing an ammonium ion feeder is also not particularly limited, and for example, aqueous ammonia or an aqueous solution such as ammonium sulfate, ammonium chloride, ammonium carbonate or ammonium fluoride may be used. Can be done.

When ammonia water is used as the ammonium ion feeder, the concentration thereof is preferably 20% by mass to 30% by mass, more preferably 22% by mass to 28% by mass. By restricting the concentration of ammonia water to such a range, it is possible to minimize the loss of ammonia due to volatilization and the like, so that it is possible to improve the production efficiency.

The method of supplying the aqueous solution containing the ammonium ion feeder can also be supplied by a pump capable of controlling the flow rate, as in the case of the alkaline aqueous solution.

(3) Crystallization reaction
In the method for producing composite hydroxide particles of the present invention, the crystallization reaction is clearly separated into two steps, a nucleation step in which nucleation is mainly performed and a particle growth step in which particle growth is mainly carried out. In the particle growth step, the reaction atmosphere, that is, the atmosphere in the reaction aqueous solution, is oxidized with a non-oxidizing atmosphere by using a diffuser tube while adjusting the conditions of the crystallization reaction in the above step and continuing the supply of the raw material aqueous solution. It is characterized by switching between the sexual atmosphere and the atmosphere as appropriate. In particular, at the time of switching the atmosphere, an atmosphere gas, that is, an oxidizing gas, an inert gas, or a mixed gas thereof is sent into the reaction aqueous solution by using an air diffuser, and these gases and the reaction aqueous solution are brought into direct contact with each other. By rapidly switching the reaction atmosphere, it is possible to efficiently obtain composite hydroxide particles having a particle structure in which the above-mentioned low-density layer and high-density layer are laminated, an average particle size, and a particle size distribution.

[pH value]
In the method for producing composite hydroxide particles of the present invention, the pH value of the reaction aqueous solution at a liquid temperature of 25 ° C. is set in the range of 12.0 to 14.0 in the nucleation generation step, and 10. It is necessary to control in the range of 5 to 12.0. In any of the steps, it is preferable to control the fluctuation range of the pH value during the crystallization reaction within ± 0.2. When the fluctuation range of the pH value is large, the amount of nucleation generated and the ratio of particle growth are not constant, and it becomes difficult to obtain composite hydroxide particles having a narrow particle size distribution. The pH value of the reaction aqueous solution can be measured with a pH meter, and the ammonium ion concentration can be measured with an ion meter.

a) Nucleation step In the nucleation step, the pH value of the reaction aqueous solution (aqueous solution for nucleation) is adjusted from 12.0 to 14.0, preferably 12.3 to 13.5, based on a liquid temperature of 25 ° C. It is preferably necessary to control in the range of 12.5 to 13.3. This makes it possible to suppress the growth of nuclei and give priority to nucleation, and the nuclei produced in this step can be made homogeneous and have a narrow particle size distribution. On the other hand, when the pH value is less than 12.0, the growth of nuclei (particles) proceeds with the formation of nuclei, so that the particle size of the obtained composite hydroxide particles becomes non-uniform and the particle size distribution deteriorates. Further, when the pH value exceeds 14.0, the nucleated nuclei become too fine, which causes a problem that the aqueous solution for nucleation gels.

b) Particle growth step In the particle growth step, the pH value of the reaction aqueous solution (particle growth aqueous solution) is 10.5 to 12.0, preferably 11.0 to 12.0, more preferably, based on a liquid temperature of 25 ° C. Needs to be controlled in the range of 11.5 to 12.0. As a result, the formation of new nuclei is suppressed, the particle growth can be prioritized, and the obtained composite hydroxide particles can be made homogeneous and have a narrow particle size distribution. On the other hand, when the pH value is less than 10.5, the ammonium ion concentration increases and the solubility of metal ions increases, so that not only the rate of the crystallization reaction slows down but also the amount of metal ions remaining in the reaction aqueous solution increases. However, productivity deteriorates. Further, when the pH value exceeds 12.0, the amount of nuclei generated during the particle growth step increases, the particle size of the obtained composite hydroxide particles becomes non-uniform, and the particle size distribution deteriorates.

When the pH value is 12.0, it is a boundary condition between nucleation and nuclear growth. Therefore, depending on the presence or absence of nuclei present in the reaction aqueous solution, either the nucleation step or the particle growth step should be used. Can be done. That is, if the pH value of the nuclear formation step is set higher than 12.0 to generate a large amount of nuclei and then the pH value of the particle growth step is set to 12.0, a large amount of nuclei are present in the reaction aqueous solution. It is possible to obtain composite hydroxide particles in which growth occurs preferentially and the particle size distribution is narrow. On the other hand, when the pH value of the nucleation step is 12.0, since there are no nuclei to grow in the reaction aqueous solution, nucleation occurs preferentially, and the pH value of the particle growth step is made smaller than 12.0. , The generated nuclei can grow to obtain good composite hydroxide particles. In either case, the pH value of the particle growth step may be controlled to be lower than the pH value of the nucleation step, and in order to clearly separate nucleation and particle growth, the pH value of the particle growth step should be set to nuclei. It is preferably 0.5 or more lower than the pH value in the production step, and more preferably 1.0 or more.

[Reaction atmosphere]
The structure of the composite hydroxide particles of the present invention is formed by controlling the pH value of the reaction aqueous solution in the nucleation generation step and the particle growth step as described above, and controlling the reaction atmosphere in these steps. Therefore, in the method for producing composite hydroxide particles of the present invention, it is important to control the reaction atmosphere as well as the pH value in each step. That is, by controlling the pH value in each step as described above and adjusting the initial reaction atmosphere of the nucleation step and the particle growth step to a non-oxidizing atmosphere, the central portion where the plate-shaped primary particles are aggregated. Is formed. Further, in the middle of the particle growth process, by introducing an atmospheric gas using an air diffuser, the non-oxidizing atmosphere is switched to the oxidizing atmosphere, and then the non-oxidizing atmosphere is further switched to the outside of the central part. A structure is formed in which a low-density layer in which plate-shaped primary particles and fine primary particles are aggregated and a high-density layer in which plate-shaped primary particles are aggregated are laminated.

In such control of the reaction atmosphere, the fine primary particles constituting the low density layer are usually plate-like and / or needle-like, but depending on the composition of the composite hydroxide particles, they are rectangular parallelepiped, elliptical, or ridged. Shapes such as facets can also be taken. The same applies to the plate-shaped primary particles constituting the central portion and the high-density layer. Therefore, in the method for producing composite hydroxide particles of the present invention, it is necessary to appropriately control the reaction atmosphere at each stage according to the composition of the desired composite hydroxide particles.

a) Non-oxidizing atmosphere In the production method of the present invention, it is necessary to control the reaction atmosphere at the stage of forming the central portion of the composite hydroxide particles and the high-density layer to a non-oxidizing atmosphere. Specifically, by introducing a non-oxidizing gas such as an inert gas, the oxygen concentration in the reaction atmosphere is 5% by volume or less, preferably 2% by volume or less, and more preferably 1% by volume or less. It is necessary to control the mixed atmosphere of oxygen and an inert gas so as to have an oxidizing atmosphere. As a result, the nuclei generated in the nucleation step can be grown to a certain range while suppressing unnecessary oxidation, so that the plate-shaped primary particles aggregate in the center of the composite hydroxide particles and the high-density layer. It can be a structure. As described above, the reaction atmosphere is usually adjusted before the supply of the raw material aqueous solution is started.

b) Oxidizing atmosphere On the other hand, at the stage of forming a low-density layer of composite hydroxide particles, it is necessary to control the reaction atmosphere to an oxidizing atmosphere. Specifically, it is necessary to control the oxygen concentration in the reaction atmosphere so as to exceed 5% by volume, preferably 10% by volume or more, and more preferably the air atmosphere (oxygen concentration: 21% by volume). Will be. By controlling the oxygen concentration in the reaction atmosphere to such a range, particle growth is suppressed and the average particle size of the primary particles is in the range of 0.01 μm to 0.3 μm. A low density layer having a sufficient density difference from the layer can be formed.

The upper limit of the oxygen concentration in the reaction atmosphere at this stage is not particularly limited, but if the oxygen concentration is excessively high, the average particle size of the primary particles is less than 0.01 μm, and a low density layer is sufficient. It may not be the size. Therefore, the oxygen concentration is preferably 30% by volume or less.

c) Timing of atmosphere control In the particle growth step, it is necessary to perform the above-mentioned atmosphere control so that composite hydroxide particles having a target particle structure are formed.

In the method for producing composite hydroxide particles of the present invention, when an atmospheric gas is directly supplied into the reaction aqueous solution by using an air diffuser, the reaction atmosphere, that is, the amount of oxygen dissolved in the reaction aqueous solution which is the reaction field is determined. It changes without delay with respect to changes in oxygen concentration in the reaction vessel. Therefore, the atmosphere switching time can be confirmed by measuring the oxygen concentration in the reaction vessel. On the other hand, when the atmospheric gas is supplied to the space in contact with the reaction aqueous solution in the reaction vessel, there is a time lag between the change in the oxygen dissolved amount in the reaction aqueous solution and the change in the oxygen concentration in the reaction vessel. Until the change in oxygen concentration in the reaction tank stabilizes, the amount of dissolved oxygen in the reaction aqueous solution cannot be immediately confirmed as the correct value, but similarly, it is confirmed by the measured value after the oxygen concentration in the reaction vessel stabilizes. It is possible to do. As described above, in either case, the switching time of the atmosphere obtained based on the oxygen concentration in the reaction vessel can be set as the switching time of the dissolved oxygen amount in the reaction aqueous solution which is the reaction field, and thus the reaction. The reaction atmosphere can be appropriately controlled over time based on the oxygen concentration in the tank.

In the present invention, the time required for switching the atmosphere is about 1% to 2% with respect to the entire particle growth step. This time is also common when switching from a non-oxidizing atmosphere to an oxidizing atmosphere or from an oxidizing atmosphere to a non-oxidizing atmosphere. Therefore, although it is possible to strictly control the atmosphere switching time independently, it is usually sufficient to include it in the non-oxidizing atmosphere or the oxidizing atmosphere after the atmosphere switching.

In order to obtain composite hydroxide particles composed of a central part, a plurality of low-density layers and a plurality of high-density layers, the non-oxidizing atmosphere and the oxidizing atmosphere are alternately switched, and a particle growth step is performed. The ratio of the entire crystallization reaction in the oxidizing atmosphere in the above is in the range of 3% to 30% with respect to the entire particle growth process, and the ratio of each crystallization reaction in the oxidizing atmosphere is the particle growth. It should be in the range of 1% to 12.5% with respect to the entire process. By switching the reaction atmosphere in this way, the size of the central portion and the sizes of the low-density layer and the high-density layer are controlled within a suitable range, and the laminated structure composed of the low-density layer and the high-density layer has an appropriate number of layers. Can be controlled to.

More specifically, the crystallization reaction due to the non-oxidizing atmosphere in the initial stage is preferably in the range of 10% to 25%, more preferably in the range of 10% to 18% with respect to the entire particle growth step time. .. Reactions in this range of reaction times in a non-oxidizing atmosphere form a center of appropriate size. After a lapse of a predetermined time, the introduction of the oxidizing gas into the reaction aqueous solution is started, and the non-oxidizing atmosphere is switched to the oxidizing atmosphere.

The crystallization reaction (including the switching time from the non-oxidizing atmosphere to the oxidizing atmosphere) in each oxidizing atmosphere is preferably in the range of 1% to 12.5% with respect to the total particle growth process time. It is preferably in the range of 1% to 10%. However, it is necessary to keep the ratio of the entire crystallization reaction in the oxidizing atmosphere within the range of 3% to 30%. The ratio of the entire crystallization reaction in the oxidizing atmosphere is preferably in the range of 5% to 25% and more preferably in the range of 10% to 15% with respect to the total particle growth step time. Reactions over this range of reaction times in each oxidizing atmosphere form a low density layer in the positive electrode active material that allows the formation of spaces of appropriate size to disperse inside the secondary particles. Will be done. After a lapse of a predetermined time, the introduction of the non-oxidizing gas, that is, the inert gas or the mixed gas of the oxidizing gas and the inert gas into the reaction aqueous solution is started, and the atmosphere is switched from the oxidizing atmosphere to the non-oxidizing atmosphere.

The crystallization reaction (including the switching time from the oxidizing atmosphere to the non-oxidizing atmosphere) in each non-oxidizing atmosphere after the start of switching from the oxidizing atmosphere is preferably 10 with respect to the entire particle growth process time. It is in the range of% to 70%, more preferably in the range of 15% to 40%. Reactions in this range of reaction times in a non-oxidizing atmosphere form a space in the positive electrode active material consisting of a large number of pores capable of communicating with the outside without reducing the tap density of the secondary particles. A high-density layer is formed, which enables the formation of a high-density layer. After a lapse of a predetermined time, the introduction of the oxidizing gas into the reaction aqueous solution is started to switch from the non-oxidizing atmosphere to the oxidizing atmosphere, or finally the crystallization reaction is terminated.

The ratio of the crystallization reaction in the oxidizing atmosphere here is defined as the ratio of the amount of metal added in the oxidizing atmosphere to the total amount of metal added in the particle growth step. Similarly, the ratio of the crystallization reaction in the non-oxidizing atmosphere is defined as the ratio of the amount of metal added in the non-oxidizing atmosphere to the total amount of metal added in the particle growth step. In actual operation, these have a predetermined ratio of each crystallization reaction time to the time of the entire particle growth process by supplying a constant amount of the raw material aqueous solution and making the amount of metal added constant. Can be controlled so as to be.

d) Switching method Conventionally, to switch the reaction atmosphere during the crystallization process, the atmosphere gas is circulated in the reaction vessel, or a conduit having an inner diameter of about 1 mm to 50 mm is inserted into the reaction aqueous solution and bubbling is performed by the atmosphere gas. It is common to do it in. However, in such a conventional technique, it takes a long time to switch the reaction atmosphere, so it is necessary to stop the supply of the raw material aqueous solution during the switching. This is because it was thought that if the supply of the raw material aqueous solution was not stopped, a gentle density gradient was formed inside the composite hydroxide particles, and the low-density layer could not be made sufficiently large.

On the other hand, the method for producing composite hydroxide particles of the present invention is characterized in that the reaction atmosphere is switched by a diffuser tube. Since the air diffuser is composed of a conduit having a large number of fine holes on the surface and can release a large number of fine gases (air bubbles) into the liquid, it is possible to switch the reaction atmosphere in a short time. Therefore, it is not necessary to stop the supply of the raw material aqueous solution when the reaction atmosphere is switched, and the production efficiency can be improved. Further, the ratio of each crystallization reaction in the oxidizing atmosphere is in the range of 1% to 12.5% with respect to the particle growth step, that is, the time of each crystallization reaction in the oxidizing atmosphere is 10%. A composite hydroxide having a particle structure having a low-density layer having a structure in which a high-density portion exists inside the central portion and the high-density layer, or between the high-density layers, even if the following is short. Particles can be easily formed.

As such an air diffuser, it is preferable to use a ceramic one having excellent resistance in a high pH environment. Further, the smaller the pore size of the air diffuser, the finer bubbles can be discharged, so that the reaction atmosphere can be switched with high efficiency. In the present invention, it is preferable to use an air diffuser having a pore diameter of 100 μm or less, and more preferably to use an air diffuser having a pore size of 50 μm or less.

(4) Ammonium ion concentration The ammonium ion concentration in the reaction aqueous solution is preferably maintained at a constant value within the range of 3 g / L to 25 g / L, more preferably 5 g / L to 20 g / L. Since ammonium ions function as a complexing agent in the reaction aqueous solution, if the ammonium ion concentration is less than 3 g / L, the solubility of metal ions cannot be kept constant, and the reaction aqueous solution tends to gel and has a shape. It becomes difficult to obtain composite hydroxide particles having a uniform particle size. On the other hand, if the ammonium ion concentration exceeds 25 g / L, the solubility of the metal ions becomes too large, so that the amount of metal ions remaining in the reaction aqueous solution increases, which causes composition deviation and the like.

If the ammonium ion concentration fluctuates during the crystallization reaction, the solubility of the metal ions fluctuates, and uniform composite hydroxide particles cannot be formed. Therefore, it is preferable to control the fluctuation range of the ammonium ion concentration within a certain range through the nucleation step and the particle growth step, and specifically, it is preferable to control the fluctuation range to ± 5 g / L.

(5) Reaction temperature It is necessary to control the temperature (reaction temperature) of the reaction aqueous solution in the range of preferably 20 ° C. or higher, more preferably 20 ° C. to 60 ° C. through the nucleation step and the particle growth step. If the reaction temperature is less than 20 ° C., the solubility of the reaction aqueous solution becomes low, so that nucleation is likely to occur, and it becomes difficult to control the average particle size and particle size distribution of the obtained composite hydroxide particles. The upper limit of the reaction temperature is not particularly limited, but when it exceeds 60 ° C., the volatilization of ammonia is promoted, and the ammonium ion feeder supplied to control the ammonium ions in the reaction aqueous solution within a certain range. The amount of the aqueous solution containing the above increases, and the production cost increases.

(6) Coating Step In the method for producing composite hydroxide particles of the present invention, a compound containing the additive element M is added to the raw material aqueous solution to obtain composite hydroxide particles in which the additive element M is dispersed inside the particles. Obtainable. However, in order to obtain the effect of the addition of the additive element M with a smaller addition amount, a coating step of coating the surface of the composite hydroxide particles with the compound containing the additive element M is performed after the particle growth step. It is preferable to do it.

The coating method is not particularly limited as long as the composite hydroxide particles can be coated with the compound containing the additive element M. For example, the composite hydroxide particles are made into a slurry, the pH value thereof is controlled within a predetermined range, and then an aqueous solution (coating aqueous solution) in which a compound containing the additive element M is dissolved is added to the surface of the composite hydroxide particles. By precipitating the compound containing the additive element M, composite hydroxide particles coated with the compound containing the additive element M can be obtained. In this case, the alkoxide solution of the additive element M may be added to the slurryed composite hydroxide particles instead of the coating aqueous solution. Alternatively, the composite hydroxide particles may be coated by spraying an aqueous solution or slurry in which a compound containing the additive element M is dissolved and drying the composite hydroxide particles without forming the slurry. Further, a method such as spray-drying a slurry in which a compound containing the composite hydroxide particles and the additive element M is suspended, or a method such as mixing the composite hydroxide particles and the compound containing the additive element M by a solid phase method. Can also be covered with.

When the surface of the composite hydroxide particles is coated with the additive element M, the raw material aqueous solution is provided so that the composition of the composite hydroxide particles after coating matches the composition of the target composite hydroxide particles. And it is necessary to adjust the composition of the coating aqueous solution as appropriate. Further, the coating step may be performed on the heat-treated particles after the composite hydroxide particles have been heat-treated.

(7) Production apparatus The crystallization apparatus (reaction tank) for producing the composite hydroxide particles of the present invention is particularly limited as long as the reaction atmosphere can be switched by the above-mentioned air diffuser tube. There is no such thing. However, it is preferable to use a batch type crystallization device that does not collect the precipitated product until the crystallization reaction is completed. Unlike the continuous crystallization device that recovers the product by the overflow method, such a crystallization device does not recover the growing particles at the same time as the overflow liquid, so that the composite hydroxylation with a narrow particle size distribution Particles can be easily obtained. Further, in the method for producing composite hydroxide particles of the present invention, it is necessary to appropriately control the reaction atmosphere during the crystallization reaction, so that it is preferable to use a closed crystallization device.

3. 3. Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery The positive electrode active material of the present invention is a positive electrode active material for non-aqueous electrolyte secondary battery composed of lithium transition metal-containing composite oxide particles, and a plurality of primary particles are aggregated. It is composed of the formed secondary particles. In particular, in the positive electrode active material of the present invention, the secondary particles are composed of an outer shell portion composed of aggregated primary particles and primary particles existing inside the outer shell portion and aggregated in the same manner as the outer shell portion, and It is characterized by having an agglomerated portion that is electrically conductive with the outer shell portion and a space portion having a plurality of pore structures dispersed in the agglomerated portion.

(1) Particle structure a) Structure of secondary particles The positive electrode active material of the present invention is composed of secondary particles formed by agglomeration of a plurality of primary particles. These secondary particles are composed of an outer shell portion composed of primary particles aggregated in the entire circumferential direction of the secondary particles, and primary particles existing inside the outer shell portion and aggregated in the same manner as the outer shell portion, and outside. It is characterized by having an agglomerated portion that is electrically conductive with the shell portion and a space portion having a plurality of pore structures dispersed in the agglomerated portion. In other words, a structure in which a plurality of spaces having a predetermined size and preferably having a small variation in the secondary particles having a predetermined size are dispersed in the secondary particles constituting the positive electrode active material. It is characterized by having.

Here, "electrically conducting" means that the aggregated portions of the primary particles are structurally connected to each other and are in a state of being electrically conductive. Further, the "outer shell portion" corresponds to a portion in which the outermost high-density layer formed of the composite hydroxide particles as a precursor is sintered and shrunk. Further, the "aggregate portion" means that the central portion of the composite hydroxide particles as the precursor, the high-density layer excluding the high-density layer of the outermost shell, and the high-density portion in the low-density layer are sintered and shrunk. Means part. Further, in the "space portion", the fine primary particles constituting the low-density portion of the composite hydroxide particles as the precursor are formed into the surrounding central portion, the high-density layer, and the plate-shaped primary particles constituting the high-density portion. It means a pore structure formed by being absorbed. These pore structures are structures in which pores are separated from each other due to the presence of agglomerates, but they communicate with each other externally and mutually through grain boundaries and voids between primary particles, and are electrolyzed into the pore structure. It is possible for liquids and conductive aids to enter.

Due to such a particle structure, the positive electrode active material of the present invention has a hollow structure in which the entire inside of the conventional outer shell portion is a hollow portion, or a predetermined shape that spreads in the circumferential direction between the outer shell portion and the central portion. Compared with a positive electrode active material having a hollow structure in which voids having the above size are present, a larger specific surface area and a higher tap density are compatible. In the positive electrode active material having the particle structure of the present invention, the electrolytic solution penetrates into the secondary particles through the grain boundaries, voids or spaces between the primary particles, so that not only the surface of the secondary particles but also the secondary particles are secondary. Lithium can be removed and inserted even inside the subatomic particles. Moreover, since the outer shell portion and the aggregated portion are electrically conductive and the cross-sectional area of the path is sufficiently large, this positive electrode active material is compared with the positive electrode active material described in WO2014 / 181891 and the like. , The resistance inside the particles (internal resistance) can be significantly reduced. Therefore, when a secondary battery is constructed using this positive electrode active material, it is possible to further improve the output characteristics without impairing the battery capacity and cycle characteristics.

(2) Average particle size MV
The positive electrode active material of the present invention is adjusted so that the average particle size MV is 1 μm to 15 μm, preferably 3 μm to 12 μm, and more preferably 3 μm to 10 μm. If the average particle size MV of the positive electrode active material is in such a range, not only the battery capacity per unit volume of the secondary battery using this positive electrode active material can be increased, but also the safety and output characteristics can be improved. Can be improved. On the other hand, if the average particle size MV is less than 1 μm, the filling property of the positive electrode active material is lowered, and the battery capacity per unit volume cannot be increased. On the other hand, when the average particle size MV exceeds 15 μm, the reaction area of the positive electrode active material is reduced and the interface with the electrolytic solution is reduced, so that it is difficult to improve the output characteristics.

The average particle size MV of the positive electrode active material means a volume-based average particle size (Mean Volume Diameter) as in the case of the composite hydroxide particles described above, and is measured by, for example, a laser light diffraction scattering type particle size analyzer. It can be obtained from the calculated volume integration value.

(3) Particle Size Distribution The positive particle active material of the present invention has an index [(d90-d10) / average particle size MV] indicating the spread of the particle size distribution of 0.70 or less, preferably 0.60 or less, more preferably. Is 0.55 or less, and is composed of lithium composite acid particles having an extremely narrow particle size distribution. Such a positive electrode active material has a small proportion of fine particles and coarse particles, and a secondary battery using the same has excellent safety, cycle characteristics, and output characteristics.

On the other hand, when [(d90-d10) / average particle size MV] exceeds 0.70, the ratio of fine particles and coarse particles in the positive electrode active material increases. For example, in a secondary battery using a positive electrode active material with a large proportion of fine particles, the secondary battery tends to generate heat due to the local reaction of the fine particles, which not only reduces safety but also fine particles. Due to the selective deterioration of the particles, the cycle characteristics become inferior. Further, in the secondary battery using the positive electrode active material having a large proportion of coarse particles, the reaction area between the electrolytic solution and the positive electrode active material cannot be sufficiently secured, and the output characteristics are inferior.

On the other hand, on the premise of industrial scale production, it is not realistic to use a positive electrode active material having an excessively small [(d90-d10) / average particle size MV]. Therefore, in consideration of cost and productivity, the lower limit of [(d90-d10) / average particle size] is preferably about 0.25.

The meanings of d10 and d90 in the index [(d90-d10) / average particle size MV] indicating the spread of the particle size distribution, and how to obtain them are the same as those of the above-mentioned composite hydroxide particles. The explanation in is omitted.

(4) BET Specific Surface Area The positive electrode active material of the present invention is characterized in that the specific surface area is improved due to the presence of the space formed inside the secondary particles. As the specific surface area of the positive electrode active material in the present invention, for example, the BET specific surface area measured by the BET method by adsorbing nitrogen gas is used. In the positive electrode active material of the present invention, the BET specific surface area is preferably as large as possible as long as the structure of the secondary particles described above is maintained. This is because the larger the BET specific surface area, the larger the contact area with the electrolytic solution, and the output characteristics of the secondary battery using this can be significantly improved. Specifically, the BET specific surface area of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is in the range of 1.5 m ² / g to 4.0 m ² / g. In the present invention, if the specific surface area of the positive electrode active material is less than 1.5 m ² / g, it is not possible to secure a sufficient reaction area with the electrolytic solution when a secondary battery is configured, and the output characteristics are sufficiently sufficient. This is because it is difficult to improve. The BET specific surface area is preferably 2.0 m ² / g or more, and more preferably 2.5 m ² / g or more.

(5) Tap density In order to extend the usage time of portable electronic devices and the mileage of electric vehicles, increasing the capacity of secondary batteries has become an important issue. On the other hand, the thickness of the electrode of the secondary battery is required to be about several microns due to the problem of packing of the entire battery and electron conductivity. Therefore, it is necessary not only to use a high-capacity material as the positive electrode active material, but also to improve the filling property of the positive electrode active material and to increase the capacity of the secondary battery as a whole.

From this point of view, the positive electrode active material of the present invention has a BET specific surface area as large as 1.5 m ² / g to 4.0 m ² / g, but has a filling property (secondary component of the positive electrode active material). It is characterized in that the tap density, which is an index of particle sphericality), is maintained in the range of 1.0 g / cm ³ to 2.0 g / cm ³ . When the tap density is less than 1.0 g / cm ³ , the filling property is low and the battery capacity of the entire secondary battery may not be sufficiently improved. On the other hand, the upper limit of the tap density is not particularly limited, but in the particle structure of the present invention, the upper limit under normal manufacturing conditions is about 2.0 g / cm ³ . The tap density is preferably 1.3 g / cm ³ or more, and more preferably 1.5 g / cm ³ or more.

The tap density represents the bulk density after tapping the sample powder collected in the container 100 times based on JIS Z-2504, and can be measured using a shaking specific gravity measuring device.

(6) Spatial part ratio In the positive electrode active material of the present invention, it is necessary that a plurality of space parts are dispersed inside the particles. In the positive electrode active material of the present invention, the total area ratio of the plurality of spaces measured by observing the cross section of the secondary particles is in the range of 15% to 30% with respect to the cross-sectional area of the secondary particles. As the occupancy rate of the space area with respect to the cross-sectional area of the positive electrode active material (hereinafter, "space area ratio") increases, the specific surface area tends to increase. That is, when a secondary battery is configured, it leads to securing a reaction area with the electrolytic solution. If this space ratio is lower than the above range, a sufficient space portion is not formed and the effect of increasing the specific surface area cannot be obtained. On the other hand, if it exceeds the above range, voids larger than the mechanical structure are present inside the secondary particles, and the ratio of the agglomerated portions becomes too low, so that desired characteristics cannot be obtained. This spatial division ratio is preferably 20% or more.

As for the spatial ratio, the binarized image as shown in FIG. 2 is SEM-observed with respect to the cross section of any 10 or more particles of the positive electrode active material, and the obtained SEM image is binarized. As a result, the ratio occupied by the total area of the space portion (white portion in FIG. 2) dispersed in the particle in one particle cross-sectional area (sum of the black portion and the white portion in FIG. 2) was obtained. It can be obtained by calculating the average value of these.

(7) Relationship between BET specific surface area of positive electrode active material and tap density Oxidation between the BET specific surface area S (m ² / g) of the positive electrode active material and the tap density m (g / cm ³ ) has the same composition. By keeping the ratio of the total crystallization reaction in the sexual atmosphere constant, changing the number of crystallizations in the oxidizing atmosphere, the ratio of each crystallization reaction in the oxidizing atmosphere, and / or changing the firing conditions, the specific surface area thereof. When the positive electrode active material is produced by changing the above, the relationship shown in Equation 1 is established. In the present invention, the range of the slope a in the formula 1 is −0.15 <a <0.15. This is because the ratio of the crystallization reaction in each oxidizing atmosphere is appropriately controlled, and the number of crystallizations in the oxidizing atmosphere is increased, so that the space (pores) can be obtained by firing under appropriate firing conditions. It is considered that the number of the taps increases, and as a result, the specific surface area increases while the tap density remains constant. The slope a is calculated by the method of least squares.
m = aS + b ... (Equation 1)

(8) Composition The composition of the positive electrode active material of the present invention is not limited as long as it has the above-mentioned structure, but the general formula (B): Li _{1 + u} Ni _x Mn _{y Coz} M _t O ₂ (-). 0.05 ≦ u ≦ 0.50, x + y + z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is suitably applied to a positive electrode active material represented by (one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W). can do.

In this positive electrode active material, the value of u indicating an excess amount of lithium (Li) is preferably −0.05 or more and 0.50 or less, more preferably 0 or more and 0.50 or less, and further preferably 0 or more and 0.35. It shall be as follows. By restricting the value of u to the above range, the output characteristics and battery capacity of the secondary battery using this positive electrode active material as the positive electrode material can be improved. On the other hand, if the value of u is less than −0.05, the positive electrode resistance of the secondary battery becomes large, so that the output characteristics cannot be improved. On the other hand, if it exceeds 0.50, not only the initial discharge capacity decreases, but also the positive electrode resistance increases.

Nickel (Ni) is an element that contributes to increasing the potential and capacity of the secondary battery, and the value of x indicating the content thereof is preferably 0.3 or more and 0.95 or less, more preferably 0. 3 or more and 0.9 or less. If the value of x is less than 0.3, the battery capacity of the secondary battery using this positive electrode active material cannot be improved. On the other hand, if the value of x exceeds 0.95, the content of other elements decreases and the effect cannot be obtained.

Manganese (Mn) is an element that contributes to the improvement of thermal stability, and the value of y indicating its content is preferably 0.05 or more and 0.55 or less, more preferably 0.10 or more and 0.40 or less. And. If the value of y is less than 0.05, the thermal stability of the secondary battery using this positive electrode active material cannot be improved. On the other hand, if the value of y exceeds 0.55, Mn is eluted from the positive electrode active material during high temperature operation, and the charge / discharge cycle characteristics are deteriorated.

Cobalt (Co) is an element that contributes to the improvement of charge / discharge cycle characteristics, and the value of z indicating its content is preferably 0 or more and 0.4 or less, more preferably 0.10 or more and 0.35 or less. do. If the value of z exceeds 0.4, the initial discharge capacity of the secondary battery using this positive electrode active material will be significantly reduced.

The positive electrode active material of the present invention may contain an additive element M in addition to the above-mentioned metal element in order to further improve the durability and output characteristics of the secondary battery. Examples of such additive element M include magnesium (Mg), calcium (Ca), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), and molybdenum. One or more selected from (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W) can be used.

The value of t indicating the content of the additive element M is preferably 0 or more and 0.1 or less, more preferably 0.001 or more and 0.05 or less. When the value of t exceeds 0.1, the amount of metal elements contributing to the Redox reaction decreases, so that the battery capacity decreases.

Such an additive element M may be dispersed inside the particles of the positive electrode active material, or may cover the particle surface of the positive electrode active material. Further, the surface of the particles may be coated after being dispersed inside the particles. In any case, it is necessary to control the content of the additive element M so as to be within the above range.

In addition, in the above-mentioned positive electrode active material, when further improvement of the battery capacity of the secondary battery using this is aimed at, the composition is described in the general formula (B1): Li _{1 + u} Ni _x Mn _y Co _z M _t O ₂ ( -0.05 ≦ u ≦ 0.20, x + y + z + t = 1, 0.7 <x ≦ 0.95, 0.05 ≦ y ≦ 0.1, 0 ≦ z ≦ 0.2, 0 ≦ t ≦ 0.1 , M is preferably adjusted so as to be represented by one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, and W). In particular, in order to achieve both thermal stability, it is more preferable that the value of x in the general formula (B1) is 0.7 <x ≦ 0.9, and 0.7 <x ≦ 0.85. Is more preferable.

On the other hand, in order to further improve the thermal stability, the composition may be expressed by the general formula (B2): Li _{1 + u} Ni _x Mn _{y Coz} 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 Al, Ti, V, Cr, Zr , Nb, Mo, Hf, Ta, W (one or more additive elements selected from)).

4. Method for Producing Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery The method for producing the positive electrode active material of the present invention uses the above-mentioned composite hydroxide particles as a precursor and has a predetermined structure, average particle size MV and particle size distribution. As long as the positive electrode active material can be synthesized, there is no particular limitation. However, on the premise of industrial scale production, the above-mentioned composite hydroxide particles are mixed with a lithium compound to obtain a lithium mixture, and the obtained lithium mixture is mixed at 650 ° C. in an oxidizing atmosphere. It is preferable to synthesize the positive electrode active material by a production method including a firing step of firing at about 920 ° C. If necessary, steps such as a heat treatment step and a calcining step may be added to the above-mentioned steps. According to such a manufacturing method, the above-mentioned positive electrode active material, particularly the positive electrode active material represented by the general formula (B), can be easily obtained.

(1) Heat Treatment Step In the method for producing a positive electrode active material of the present invention, a heat treatment step may be optionally provided before the mixing step to make the composite hydroxide particles into heat treatment particles and then mix them with the lithium compound. .. Here, the heat-treated particles include not only the composite hydroxide particles from which excess water has been removed in the heat treatment step, but also the transition metal-containing composite oxide particles converted into oxides by the heat treatment step (hereinafter, “composite oxide”). Also included are "particles") or mixtures thereof.

The heat treatment step is a step of removing excess water contained in the composite hydroxide particles by heating the composite hydroxide particles to 105 ° C. to 750 ° C. and heat-treating the composite hydroxide particles. As a result, the amount of water remaining until after the firing step can be reduced to a certain amount, and variations in the composition of the obtained positive electrode active material can be suppressed.

The heating temperature in the heat treatment step is 105 ° C to 750 ° C. If the heating temperature is less than 105 ° C., the excess water in the composite hydroxide particles cannot be removed, and the variation may not be sufficiently suppressed. On the other hand, even if the heating temperature exceeds 700 ° C., not only the further effect cannot be expected, but also the production cost increases.

In the heat treatment step, it is sufficient that water can be removed to the extent that the number of atoms of each metal component in the positive electrode active material and the ratio of the number of atoms of Li do not vary, so that all the composite hydroxide particles are not necessarily compositely oxidized. There is no need to convert to particles. However, in order to reduce the variation in the number of atoms of each metal component and the ratio of the number of Li atoms, the mixture is heated to 400 ° C. or higher to convert all the composite hydroxide particles into composite oxide particles. It is preferable to do so. The above-mentioned variation can be further suppressed by determining the metal component contained in the composite hydroxide particles under the heat treatment conditions in advance by analysis and determining the mixing ratio with the lithium compound.

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

The heat treatment time is not particularly limited, but is preferably at least 1 hour, more preferably 5 hours to 15 hours, from the viewpoint of sufficiently removing excess water in the composite hydroxide particles.

(2) Mixing Step The mixing step is a step of mixing a lithium compound with the above-mentioned composite hydroxide particles or heat-treated particles to obtain a lithium mixture.

In the mixing step, the ratio of the sum of the number of atoms (Me) to metal atoms other than lithium in the lithium mixture, specifically nickel, cobalt, manganese and the additive element M, to the number of lithium atoms (Li) ( Li / Me) is 0.95 to 1.5, preferably 1.0 to 1.5, more preferably 1.0 to 1.35, and even more preferably 1.0 to 1.2. It is necessary to mix the lithium compound with the composite hydroxide particles or heat-treated particles. That is, since Li / Me does not change before and after the firing step, composite hydroxide particles or heat-treated particles and a lithium compound are mixed so that Li / Me in the mixing step becomes Li / Me of the target positive electrode active material. It will be necessary to mix.

The lithium compound used in the mixing step is not particularly limited, but it is preferable to use lithium hydroxide, lithium nitrate, lithium carbonate or a mixture thereof from the viewpoint of easy availability. In particular, considering ease of handling and stability of quality, it is preferable to use lithium hydroxide or lithium carbonate.

It is preferable that the composite hydroxide particles or the heat-treated particles and the lithium compound are sufficiently mixed so as not to generate fine powder. Insufficient mixing may cause variations in Li / Me among the individual particles, making it impossible to obtain sufficient battery characteristics. A general mixer can be used for mixing. For example, a shaker mixer, a Lady Gemixer, a Julia mixer, a V blender, or the like can be used.

(3) Calcining step When lithium hydroxide or lithium carbonate is used as the lithium compound, the lithium mixture is heated at a temperature lower than the firing temperature described later and at 350 ° C. to 350 ° C. after the mixing step and before the firing step. A calcining step of calcining at 800 ° C., preferably 450 ° C. to 780 ° C. may be performed. Thereby, lithium can be sufficiently diffused in the composite hydroxide particles or the heat-treated particles, and more uniform lithium composite oxide particles can be obtained.

The holding time at the above temperature is preferably 1 hour to 10 hours, more preferably 3 hours to 6 hours. Further, the atmosphere in the calcining step is preferably an oxidizing atmosphere as in the firing step described later, and more preferably an atmosphere having an oxygen concentration of 18% by volume to 100% by volume.

(4) Firing step The calcining step is a step of calcining the lithium mixture obtained in the mixing step under predetermined conditions and diffusing lithium into the composite hydroxide particles or heat-treated particles to obtain lithium composite oxide particles. Is.

In this firing step, the central portion of the composite hydroxide particles and the heat-treated particles, the high-density portion of the high-density layer, and the low-density layer are sintered and shrunk, and the outer shell portion and the primary particles are aggregated in the positive electrode active material. Form a part. On the other hand, since the low-density portion of the low-density layer is composed of fine primary particles, it is more than the central portion, the high-density layer, and the high-density portion composed of plate-shaped single particles larger than the fine primary particles. Also begins to sinter from the low temperature range. Moreover, the low-density portion has a larger shrinkage amount than the central portion, the high-density layer, and the high-density portion. For this reason, the fine primary particles constituting the low-density portion contract to the central portion where the sintering progress is slow, the high-density layer, and the side with the high-density portion, and a space portion having an appropriate size is formed as pores. The Rukoto. At this time, the high-density portion in the low-density layer is sintered and shrunk while maintaining the connection with the central portion and the high-density layer. Therefore, in the obtained positive electrode active material, between the outer shell portion and the agglomerated portion. , And the inside of the agglomerated portion is electrically conductive, and the cross-sectional area of the path can be sufficiently secured. As a result, the internal resistance of the positive electrode active material is significantly reduced, and when a secondary battery is configured, the output characteristics can be improved without impairing the battery capacity and cycle characteristics.

The particle structure of such a positive electrode active material is basically determined according to the particle structure of the composite hydroxide particles that are precursors, but it may be affected by its composition, firing conditions, and the like. After conducting a preliminary test, it is preferable to appropriately adjust each condition so as to obtain a desired structure.

The furnace used in the firing step is not particularly limited as long as it can heat the lithium mixture in the atmosphere or an oxygen stream. However, from the viewpoint of keeping the atmosphere in the furnace uniform, an electric furnace that does not generate gas is preferable, and either a batch type or a continuous type electric furnace can be preferably used. The same applies to the furnace used in the heat treatment step and the calcining step.

a) Firing temperature The calcination temperature of the lithium mixture needs to be 700 ° C to 920 ° C. In particular, in the present invention, the temperature is preferably 800 ° C to 900 ° C. When the firing temperature is less than 650 ° C., lithium does not sufficiently diffuse into the composite hydroxide particles or heat-treated particles, and excess lithium or unreacted composite hydroxide particles or heat-treated particles remain, or the obtained lithium composite. The crystallinity of the oxide particles may be insufficient. Further, if the firing temperature is less than 700 ° C., the agglomerated portion and the space portion may not be controlled within an appropriate size range. On the other hand, if the firing temperature exceeds 920 ° C., the pores in the lithium composite oxide particles may be crushed, and the lithium composite oxide particles are violently sintered, causing abnormal grain growth, which is not possible. The proportion of regular coarse particles will increase. Further, by setting the firing temperature of the lithium mixture to 800 ° C. to 900 ° C., more preferably 850 ° C. to 900 ° C., a BET specific surface area of 2.5 m ² / g or more and a tap of 1.5 g / cm ³ or more. It is possible to achieve both densities.

When the positive electrode active material represented by the above-mentioned general formula (B1) is to be obtained, the firing temperature is preferably 700 ° C. to 900 ° C. On the other hand, when the positive electrode active material represented by the general formula (B2) is to be obtained, the firing temperature is preferably 800 ° C. to 900 ° C.

The rate of temperature rise in the firing step is preferably 2 ° C./min to 10 ° C./min, and more preferably 5 ° C./min to 10 ° C./min. Further, during the firing step, the lithium compound is held at a temperature near the melting point, preferably for 1 hour to 5 hours, more preferably for 2 hours to 5 hours . Thereby, the composite hydroxide particles or the heat-treated particles can be reacted more uniformly with the lithium compound.

b) Baking time Of the firing times, the holding time at the above-mentioned firing temperature is preferably at least 2 hours, more preferably 4 hours to 24 hours. If the holding time at the firing temperature is less than 2 hours, lithium does not sufficiently diffuse into the composite hydroxide particles or heat-treated particles, and excess lithium or unreacted composite hydroxide particles or heat-treated particles remain, or the obtained. There is a possibility that the crystallinity of the lithium composite oxide particles to be obtained will be insufficient.

After the holding time is completed, the cooling rate from the firing temperature to at least 200 ° C. is preferably 2 ° C./min to 10 ° C./min, and more preferably 3 ° C./min to 7 ° C./min . By controlling the cooling rate within such a range, it is possible to prevent the equipment such as the saggar from being damaged by quenching while ensuring productivity.

c) Baking atmosphere The atmosphere at the time of firing is preferably an oxidizing atmosphere, more preferably an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, and a mixed atmosphere of oxygen having an oxygen concentration and an inert gas. Is particularly preferable. That is, firing is preferably performed in the atmosphere or an oxygen stream. If the oxygen concentration is less than 18% by volume, the crystallinity of the lithium composite oxide particles may be insufficient.

(5) Crushing Step The lithium composite oxide particles obtained by the firing step may be aggregated or slightly sintered. In such a case, it is preferable to crush the aggregate or sintered body of the lithium composite oxide particles. Thereby, the average particle size and the particle size distribution of the obtained positive electrode active material can be adjusted in a suitable range. In addition, crushing means that mechanical energy is applied to an agglomerate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. It means the operation of separating and loosening agglomerates.

As a crushing method, a known means can be used, and for example, a pin mill, a hammer mill, or the like can be used. At this time, it is preferable to adjust the crushing force to an appropriate range so as not to destroy the secondary particles.

5. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention includes the same components as a general non-aqueous electrolyte secondary battery, such as a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. It should be noted that the embodiments described below are merely examples, and the non-aqueous electrolyte secondary battery of the present invention is applied to embodiments described in the present specification with various modifications and improvements. It is also possible to do.

(1) Components a) Positive electrode Using the above-mentioned positive electrode active material, for example, a positive electrode of a non-aqueous electrolyte secondary battery is manufactured as follows.

First, the positive electrode active material of the present invention is mixed with a conductive material and a binder, and if necessary, activated carbon and a solvent for adjusting the viscosity are added, and these are kneaded to prepare a positive electrode mixture paste. At that time, the mixing ratio of each in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery. For example, 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 parts by mass to 95 parts by mass, as in the case of the positive electrode of a general non-aqueous electrolyte secondary battery. The content of the conductive material can be 1 part by mass to 20 parts by mass, and the content of the binder can be 1 part by mass to 20 parts by mass.

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

As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.) or a carbon black material such as acetylene black or Ketjen black can be used.

The binder serves to hold the active material particles together, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylenepropylene diene rubber, styrene butadiene, cellulose resin or polyacrylic acid. Acids can be used.

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

b) Negative electrode A metallic lithium, a lithium alloy, or the like can be used for the negative electrode. In addition, a negative electrode mixture made into a paste by mixing a binder with a negative electrode active material capable of occluding and desorbing lithium ions and adding an appropriate solvent is applied to the surface of a metal leaf current collector such as copper. , Dried, and if necessary, compressed to increase the electrode density can be used.

Examples of the negative electrode active material include lithium-containing substances such as metallic lithium and lithium alloys, natural graphite capable of storing and desorbing lithium ions, calcined organic compounds such as artificial graphite and phenolic resin, and carbon substances such as coke. A powdery substance can be used. In this case, as the negative electrode binder, a fluororesin such as PVDF can be used as in the positive electrode, and the solvent for dispersing these active substances and the binder is an organic substance such as N-methyl-2-pyrrolidone. A solvent can be used.

c) Separator The separator is arranged so as to be sandwiched between the positive electrode and the negative electrode, and has a function of separating the positive electrode and the negative electrode and holding an electrolyte. As such a separator, for example, a thin film such as polyethylene or polypropylene, which has a large number of fine pores, can be used, but is not particularly limited as long as it has the above-mentioned function.

d) Non-aqueous electrolyte As the non-aqueous electrolyte, a non-aqueous electrolyte solution obtained by dissolving a lithium salt as a supporting salt in an organic solvent, a nonflammable solid electrolyte having ion conductivity, and the like are used.

Examples of the organic solvent used in the non-aqueous electrolyte solution 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, and further. , Tetrahydrofuran, 2-methyltetrahydrofuran, ether compounds such as dimethoxyethane, sulfur compounds such as ethylmethyl sulfone and butane sulton, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc., alone or in combination of two or more. Can be mixed and used.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and a composite salt thereof can be used.

The non-aqueous electrolytic solution may contain a radical scavenger, a surfactant, a flame retardant and the like.

On the other hand, as the solid electrolyte, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ or Li _{2S-SiS 2 can} be used.

(2) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention composed of the above positive electrode, negative electrode, separator and non-aqueous electrolyte can be made into various shapes such as a cylindrical shape and a laminated type. ..

Regardless of which shape is adopted, for example, 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 electrolytic solution to form a positive electrode current collector and an external electrode. Connect between the positive electrode terminal leading to 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 connect the non-aqueous electrolyte secondary battery. Finalize.

(3) Characteristics of non-aqueous electrolyte secondary battery As described above, the non-aqueous electrolyte secondary battery of the present invention uses the positive electrode active material of the present invention as the positive electrode material, and therefore has capacity characteristics, output characteristics and cycle characteristics. Excellent for. Moreover, it can be said that it is excellent in thermal stability and safety even in comparison with a conventional secondary battery using a positive electrode active material composed of lithium nickel-based oxide particles.

For example, when a 2032 type coin battery as shown in FIG. 3 is configured by using the positive electrode active material of the present invention, an initial discharge capacity of 160 mAh / g or more and a low positive electrode resistance can be achieved at the same time.

(4) Applications The non-aqueous electrolyte secondary battery of the present invention is excellent in capacity characteristics, output characteristics and cycle characteristics as described above, and is a small portable electronic device (notebook type) in which these characteristics are required at a high level. It can be suitably used as a power source for personal computers, mobile phone terminals, etc.). In addition, the non-aqueous electrolyte secondary battery of the present invention is excellent in safety, and not only can it be miniaturized and have high output, but also an expensive protection circuit can be simplified, so that it can be used in a mounting space. It can also be suitably used as a power source for transportation equipment subject to restrictions.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, unless otherwise specified, a reagent special grade sample manufactured by Wako Pure Chemical Industries, Ltd. was used for producing the composite hydroxide particles and the positive electrode active material. Further, the pH value of the reaction aqueous solution is measured by a pH controller (NPH-690D, manufactured by Nisshin Rika) through the nucleation generation step and the particle growth step, and the supply amount of the sodium hydroxide aqueous solution is adjusted based on this measured value. Therefore, the fluctuation range of the pH value of the reaction aqueous solution in each step was controlled within the range of ± 0.2.

(Example 1)
a) Production of composite hydroxide particles [nucleation step]
First, 14 L of water was put into the reaction tank and the temperature in the tank was set to 40 ° C. while stirring. At this time, nitrogen gas was circulated in the reaction vessel for 30 minutes, and the reaction atmosphere was set to a non-oxidizing atmosphere having an oxygen concentration of 2% by volume or less. Subsequently, an appropriate amount of 25% by mass sodium hydroxide aqueous solution and 25% by mass ammonia water are supplied into the reaction vessel so that the pH value is 12.6 based on the liquid temperature of 25 ° C. and the ammonium ion concentration is 10 g / L. A pre-reaction aqueous solution was formed by adjusting to.

At the same time, nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved in water so that the molar ratio of each metal element is Ni: Mn: Co: Zr = 38.0: 30.0: 32.0, and 2 mol / L. A raw material aqueous solution was prepared.

Next, this raw material aqueous solution was supplied to the pre-reaction aqueous solution at 115 ml / min to form an aqueous solution for the nucleation step, and nucleation was performed for 1 minute. At this time, a 25% by mass sodium hydroxide aqueous solution and a 25% by mass aqueous ammonia solution were supplied in a timely manner, and the pH value and the ammonium ion concentration of the aqueous solution for nucleation were maintained within the above ranges.

[Particle growth process]
After the completion of nucleation, the supply of all the aqueous solutions is temporarily stopped, and sulfuric acid is added to adjust the pH value to 11.2 based on the liquid temperature of 25 ° C. to prepare the aqueous solution for particle growth. Formed. After confirming that the pH value reached a predetermined value, the raw material aqueous solution was supplied at a constant rate of 115 ml / min, which was the same as in the nucleation step, and the nuclei (particles) generated in the nucleation step were grown. ..

After 40 minutes (16.7% of the total particle growth process) from the start of the particle growth process, a ceramic air diffuser with a pore size of 20 μm to 30 μm while continuing to supply the raw material aqueous solution (Kinoshita Rika Kogyo). Air was circulated in the reaction vessel using (manufactured by Co., Ltd.), and the reaction atmosphere was adjusted to an oxidizing atmosphere having an oxygen concentration of 21% by volume (switching operation 1).

After 10 minutes (4.2% with respect to the entire particle growth process) have elapsed from the switching operation 1, nitrogen is circulated in the reaction vessel while the supply of the raw material aqueous solution is continued, and the reaction atmosphere is changed to the oxygen concentration. The non-oxidizing atmosphere was adjusted to 2% by volume or less (switching operation 2).

After 80 minutes (33.3% for the entire particle growth process) have elapsed from the switching operation 2, the switching operation 1 is performed again, and the crystallization reaction in the oxidizing atmosphere is performed for 20 minutes (8 for the entire particle growth process). .3%) After continuing, the switching operation 2 is performed, and after 90 minutes (37.5% with respect to the entire particle growth process) of the crystallization reaction in the non-oxidizing atmosphere, the supply of all the aqueous solutions is stopped. This completes the particle growth process. Then, the obtained product was washed with water, filtered and dried to obtain powdery composite hydroxide particles. The rate of crystallization reaction in the entire oxidizing atmosphere was 12.5%.

In the particle growth step, 25% by mass sodium hydroxide aqueous solution and 25% by mass ammonia water were supplied in a timely manner through this step, and the pH value and ammonium ion concentration of the particle growth aqueous solution were maintained within the above ranges. ..

b) Evaluation of composite hydroxide particles [Composition]
By analysis using an ICP emission spectroscopic analyzer (ICPE-9000, Shimadzu Corporation, Shimadzu Corporation), this composite hydroxide particle was obtained by the general formula: Ni _0.38 Mn _0.30 Co _0.32 (OH). It was confirmed that it was represented by ₂ .

[Particle structure]
After embedding a part of the composite hydroxide particles in the resin and making the cross section observable by cross-section polish processing, 10 or more composite hydroxide particles are placed in an electric field radiation scanning electron microscope (FE-SEM: Japan). Observed by JSM-6360LA) manufactured by JEOL Ltd. As a result, the composite hydroxide particles have a central portion formed by aggregating the plate-shaped primary particles, and the plate-shaped primary particles and the fine primary particles are aggregated and formed on the outside of the central portion. It has two laminated structures in which a density layer and a high-density layer formed by aggregating plate-shaped primary particles are laminated, and the high-density layer is formed by agglomeration of plate-shaped primary particles in a low-density layer. It was confirmed that the high-density part was connected to the central part and other high-density layers.

Further, the central particle size ratio, the first low density layer particle size ratio, the first high density layer particle size ratio, the second low density layer particle size ratio, and the second high density layer (outer shell portion). The particle size ratio was also measured and calculated and found to be 20%, 10%, 10%, 10%, and 10%.

[Average particle size MV and particle size distribution]
Using a laser light diffraction scattering type particle size analyzer (Microtrac HRA manufactured by Nikkiso Co., Ltd.), the average particle size MV of the composite hydroxide particles is measured, and d10 and d90 are measured to show the spread of the particle size distribution. The index [(d90-d10) / average particle size MV] was calculated. As a result, it was confirmed that the average particle size was 5.5 μm and [(d90-d10) / average particle size MV] was 0.40.

c) Preparation of positive electrode active material The composite hydroxide particles obtained as described above are heat-treated at 120 ° C. for 12 hours in an air (oxygen concentration: 21% by volume) air stream (heat treatment step), and then Li / Me. Was sufficiently mixed with lithium carbonate using a shaker mixer device (TURBULA Type T2C manufactured by Willy et Bacoffen (WAB)) so as to have a value of 1.10 to obtain a lithium mixture (mixing step).

This lithium mixture is heated to 885 ° C. in an air (oxygen concentration: 21% by volume) air stream at a heating rate of 2.3 ° C./min and held at this temperature for 4 hours to be fired to reduce the cooling rate. It was cooled to room temperature at about 4 ° C./min (baking step). The positive electrode active material thus obtained was aggregated or slightly sintered. Therefore, this positive electrode active material was crushed to adjust the average particle size and the particle size distribution (crushing step).

d) Evaluation of positive electrode active material [Composition]
By analysis using an ICP emission spectrophotometer, it was confirmed that this positive electrode active material is represented by the general formula: Li _1.10 Ni _0.38 Mn _0.30 Co _0.32 O ₂ . ..

[Particle structure]
A part of the positive electrode active material was embedded in the resin, cross-section polish processing was performed to make the cross section observable, and then the observation was performed by SEM. As a result, the positive electrode active material is composed of secondary particles formed by aggregating a plurality of primary particles, and the secondary particles are dispersed in the outer shell portion and the inside of the outer shell portion. It was confirmed that the agglomerated portion of the primary particles electrically conducting with the outer shell portion and the space portion existing inside the agglomerating portion and having a plurality of pore structures and in which the primary particles do not exist are provided.

The cross-sectional image containing any 10 or more secondary particles obtained from the above SEM observation is binarized to obtain the image shown in FIG. 2, and one particle cross-sectional area (sum of black part and white part). Of these, the rate occupied by the total area of the space (white area) was calculated, and the average value of these was calculated. As a result, the area ratio of the space portion was 27.4%.

[Average particle size MV and particle size distribution]
Using a laser light diffraction scattering type particle size analyzer (Microtrac HRA manufactured by Nikkiso Co., Ltd.), the average particle size MV of the positive electrode active material is measured, and d10 and d90 are measured, which is an index showing the spread of the particle size distribution. A certain [(d90-d10) / average particle size MV] was calculated. As a result, it was confirmed that the average particle size was 5.0 μm and [(d90-d10) / average particle size MV] was 0.41.

[BET specific surface area and tap density]
The BET specific surface area was measured by a flow method gas adsorption method specific surface area measuring device (manufactured by Yuasa Ionics Co., Ltd., Multisorb), and the tap density was measured by a tapping machine (manufactured by Kuramochi Kagaku Kikai Seisakusho Co. , Ltd., KRS-406). As a result, it was confirmed that the BET specific surface area was 3.07 m ² / g and the tap density was 1.53 g / cm ³ .

e) Preparation of secondary battery A 2032 type coin battery (B) as shown in FIG. 5 was manufactured . Specifically, the positive electrode active material obtained as described above: 52.5 mg, acetylene black: 15 mg, and PTEE: 7.5 mg are mixed and pressed to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. After molding, the positive electrode (1) was prepared by drying in a vacuum dryer at 120 ° C. for 12 hours.

Next, using this positive electrode (1), a 2032 type coin battery (B) was produced in a glove box having an Ar atmosphere with a dew point controlled at −80 ° C. A lithium metal having a diameter of 17 mm and a thickness of 1 mm is used for the negative electrode (2) of this 2032 type coin battery, and ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting electrolyte are used as the electrolytic solution. (Manufactured by Toyama Yakuhin Kogyo Co., Ltd.) was used. Further, as the separator (3), a polyethylene porous membrane having a film thickness of 25 μm was used. In this way, a 2032 type coin battery (B) having a gasket (4) and a positive electrode can (5) and a negative electrode can (6) was assembled.

f) Battery evaluation [Initial discharge capacity]
After the 2032 type coin battery was manufactured and left to stand for about 24 hours, the open circuit voltage OCV (Open Circuit Voltage) became stable, and then the current density with respect to the positive electrode was 0.1 mA / cm ² and the cutoff voltage was 4.3 V. A charge / discharge test was performed to measure the discharge capacity when the battery was charged until it became full, and after a one-hour rest, and then discharged until the cutoff voltage reached 3.0 V, and the initial discharge capacity was determined. As a result, it was confirmed that the initial discharge capacity was 166.2 mAh / g. A multi-channel voltage / current generator (manufactured by Advantest Co., Ltd., R6741A) was used to measure the initial discharge capacity.

[Positive electrode resistance]
The resistance value was measured by the AC impedance method using a 2032 type coin battery charged with a charging potential of 4.1 V. A frequency response analyzer and a potentiogalvanostat (manufactured by Solartron Metrology) were used for the measurement, and the Nyquist plot shown in FIG. 4 was obtained. Since the plot appears as the sum of the solution resistance, the negative electrode resistance and the capacitance, and the characteristic curve showing the positive electrode resistance and the capacitance, the fitting calculation was performed using an equivalent circuit, and the value of the positive electrode resistance was calculated. As a result, it was confirmed that the positive electrode resistance was 5.34 Ω.

Tables 1 to 3 show the production conditions of the transition metal-containing composite hydroxide particles and the positive electrode active material, their characteristics, and the results of various performances of the battery using them. The results of Example 2, Example 3, and Comparative Example 1 below are also shown in Tables 1 to 3 in the same manner.

(Example 2)
Composite hydroxide particles were obtained in the same manner as in Example 1 except that the crystallization conditions were changed to the following conditions in the particle growth step.

In the particle growth step, the switching operation 1 is performed 32.5 minutes (13.5% with respect to the entire particle growth step) from the start of the particle growth step, and the crystallization reaction in an oxidizing atmosphere is carried out for 5 minutes (particles). After continuing the switching operation 2 (2.1% with respect to the entire growth process), the crystallization reaction in a non-oxidizing atmosphere was continued for 50 minutes (20.8% with respect to the entire particle growth process). Subsequently, the switching operation 1 is performed again, and the crystallization reaction in the oxidizing atmosphere is continued for 10 minutes (4.2% with respect to the entire particle growth step), and then the switching operation 2 is performed in the non-oxidizing atmosphere. The crystallization reaction was continued for 65 minutes (27.1% with respect to the entire particle growth step). Then, the switching operation 1 is performed again, and the crystallization reaction in the oxidizing atmosphere is continued for 15 minutes (6.3% with respect to the entire particle growth step), and then the switching operation 2 is performed in the non-oxidizing atmosphere. After 62.5 minutes (26.0% of the total particle growth step) of the crystallization reaction, the supply of all the aqueous solutions was stopped to complete the particle growth step. The rate of crystallization reaction in the entire oxidizing atmosphere was 12.6%.

Central particle size ratio, first low density layer particle size ratio, first high density layer particle size ratio, second low density layer particle size ratio, second high density layer particle size ratio, third low The density layer particle size ratio and the third high density layer (outer shell) particle size ratio are 20%, 6.7%, 6.7%, 6.7%, 6.7%, and 6. It was 7% and 6.7%.

Further, using the obtained composite hydroxide particles, a positive electrode active material and a secondary battery were obtained in the same manner as in Example 1, and their evaluation was performed.

(Example 3)
In the particle growth step, composite hydroxide particles were obtained in the same manner as in Example 1 except that the crystallization conditions were changed to the following conditions.

In the particle growth step, the switching operation 1 is performed 29 minutes (12.1% with respect to the entire particle growth step) from the start of the particle growth step, and the crystallization reaction in an oxidizing atmosphere is performed for 2.5 minutes (particles). After continuing the switching operation 2 (1.0% with respect to the entire growth process), the crystallization reaction in a non-oxidizing atmosphere was continued for 37.5 minutes (15.6% with respect to the entire particle growth process). .. Subsequently, the switching operation 1 is performed again, the crystallization reaction in the oxidizing atmosphere is continued for 5.0 minutes (2.1% with respect to the entire particle growth step), and then the switching operation 2 is performed to perform the non-oxidizing property. The crystallization reaction in the atmosphere was continued for 45 minutes (18.8% of the total particle growth step). Then, the switching operation 1 is performed again, the crystallization reaction in the oxidizing atmosphere is continued for 7.5 minutes (3.1% with respect to the entire particle growth step), and then the switching operation 2 is performed to perform the non-oxidizing atmosphere. The crystallization reaction in (20.6% with respect to the entire particle growth step) was continued for 49.5 minutes. Further, switching operation 1 is performed, and the crystallization reaction in an oxidizing atmosphere is continued for 15.0 minutes (6.3% with respect to the entire particle growth step), and then switching operation 2 is performed to crystallize in a non-oxidizing atmosphere. After 49.0 minutes (20.4% with respect to the entire particle growth step) of the analysis reaction, the supply of all the aqueous solutions was stopped to complete the particle growth step. The rate of crystallization reaction in the entire oxidizing atmosphere was 12.5%.

Central particle size ratio, first low density layer particle size ratio, first high density layer particle size ratio, second low density layer particle size ratio, second high density layer particle size ratio, third low The density layer particle size ratio, the third high density layer particle size ratio, the fourth low density layer particle size ratio, and the fourth high density layer (outer shell) particle size ratio are 20% and 5 respectively. %, 5%, 5%, 5%, 5%, 5%, 5%, and 5%.

Further, using the obtained composite hydroxide particles, a positive electrode active material and a secondary battery were obtained in the same manner as in Example 1, and their evaluation was performed.

(Comparative Example 1)
In the crystallization step of the precursor hydroxide particles, all the grain growth steps were performed in a non-oxidizing atmosphere, and the reaction time was controlled so that the particle size was about 5 μm. In the same manner, composite hydroxide particles, a positive electrode active material and a secondary battery were obtained and evaluated . The obtained hydroxide particles were entirely composed of secondary particles composed of aggregates of plate-shaped primary particles, and the obtained positive electrode active material was solid secondary particles.

Using the BET specific surface area S (m ² / g) and tap density m (g / cm ³ ) of each of the positive electrode active materials of Examples 1 to 3, the value of the inclination a in Equation 1 is calculated by the minimum square method. As a result, the inclination a was −0.11 and was in the range of −0.15 <a <0.15.
m = aS + b ... (Equation 1)

However, the BET specific surface area S (m ² / g) and tap density m (g / cm ³ ) of the positive electrode active material of Comparative Example 1 have a slope a in this formula 1 of −0.15 <a <0.15. It did not belong to the range of.

In the secondary batteries using the positive electrode active materials of Examples 1 to 3, which are within the scope of the present invention, the initial discharge capacity is increased and the positive electrode resistance is reduced in each of the secondary batteries as compared with Comparative Example 1. It was confirmed that there was.

1 Positive electrode (evaluation electrode)
2 Negative electrode 3 Separator 4 Gasket 5 Positive electrode can 6 Negative electrode can B 2032 type coin battery

Claims (12)

A reaction aqueous solution is formed by supplying an aqueous solution containing at least a transition metal and an aqueous solution containing an ammonium ion feeder into the reaction vessel, and a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery is formed by a crystallization reaction. A method for producing a transition metal-containing composite hydroxide particle as a body.
By controlling the pH value of the reaction aqueous solution based on the liquid temperature of 25 ° C. so as to be in the range of 12.0 to 14.0, the nucleation step of performing nucleation and the nucleation obtained in the nucleation step can be obtained. The nuclei are grown by controlling the pH value of the contained reaction aqueous solution at a liquid temperature of 25 ° C., which is lower than the pH value of the nucleation step and in the range of 10.5 to 12.0. , With a particle growth process,
The reaction atmosphere in the initial stages of the nucleation generation step and the particle growth step is adjusted to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less, and the supply of the raw material aqueous solution is continued after the initial step of the particle growth step. However, by introducing an oxidizing gas, the reaction atmosphere is switched from the non-oxidizing atmosphere to an oxidizing atmosphere in which the oxygen concentration exceeds 5% by volume, and the raw material aqueous solution is continuously supplied while being non-oxidized. By introducing an oxidizing gas, the atmosphere control for switching the reaction atmosphere from the oxidizing atmosphere to a non-oxidizing atmosphere having an oxygen concentration of 5% by volume or less is performed twice or more, and
When switching the reaction atmosphere, the oxidizing gas and the non-oxidizing gas are introduced using an air diffuser, and the reaction atmosphere is switched by oxidizing the total amount of metal added in the particle growth step. The ratio of the entire crystallization reaction in the oxidizing atmosphere, which is defined by the ratio of the amount of metal added in the sexual atmosphere, is in the range of 3% to 30% with respect to the entire particle growth step, and the oxidizing property. The ratio of each crystallization reaction in the atmosphere is controlled to be in the range of 1% to 12.5% with respect to the entire particle growth step.
A method for producing transition metal-containing composite hydroxide particles. The transition metal-containing composite hydroxide particles have the general formula (A): Ni _x Mn _y Coz M _t (OH) _{2 + a} (x + y + _z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦. 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf , Ta, W), the method for producing a transition metal-containing composite hydroxide particle according to claim 1, which has a composition represented by one or more additive elements). The production of the transition metal-containing composite hydroxide particles according to claim 2, further comprising a coating step of coating the transition metal-containing composite hydroxide particles with a compound containing the additive element M after the particle growth step. Method. Transition metal-containing composite hydroxide particles that are precursors of positive electrode active materials for non-aqueous electrolyte secondary batteries, and are formed by agglomeration of a plurality of plate-shaped primary particles and fine primary particles smaller than the plate-shaped primary particles. Consists of secondary particles
The secondary particles have a central portion formed by aggregating the plate-shaped primary particles, and have a low density formed by agglomerating the plate-shaped primary particles and the fine primary particles on the outside of the central portion. It is provided with two or more laminated structures in which a layer and a high-density layer formed by aggregating the plate-shaped primary particles are laminated.
The low-density layer includes a low-density portion formed by aggregating the fine primary particles and a high-density portion formed by agglomerating the plate-shaped primary particles, and the high-density layer comprises the low-density portion. The high-density portion constituting the layer is connected to the central portion and / or other high-density layer, and
The secondary particles have an average particle size in the range of 1 μm to 15 μm, and have an index [(d90-d10) / average particle size MV] indicating the spread of the particle size distribution of 0.65 or less.
Transition metal-containing composite hydroxide particles. The transition metal-containing composite hydroxide particles have the general formula (A): Ni _x Mn _y Coz M _t (OH) _{2 + a} (x + y + _z + t = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y ≦. 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, 0 ≦ a ≦ 0.5, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo, Hf , Ta, W), the transition metal composite hydroxide particle according to claim 4 , which has a composition represented by one or more additive elements). The transition metal composite hydroxide particle according to claim 5 , wherein the additive element M covers the surface of the secondary particle.
A mixing step of mixing the transition metal-containing composite hydroxide particles according to any one of claims 4 to 6 with a lithium compound to form a lithium mixture.
A firing step of firing the lithium mixture formed in the mixing step at a temperature in the range of 700 ° C. to 920 ° C. in an oxidizing atmosphere, and a firing step.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. In the mixing step, the lithium mixture is adjusted so that the ratio of the sum of the atoms of metals other than lithium contained in the lithium mixture to the number of atoms of lithium is 1: 0.95 to 1.5. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 7. The non-aqueous electrolyte secondary battery according to claim 7 or 8, further comprising a heat treatment step of heat-treating the transition metal-containing composite hydroxide particles at a temperature in the range of 105 ° C. to 750 ° C. before the mixing step. A method for manufacturing a positive electrode active material for use. The positive electrode active material for a non-aqueous electrolyte secondary battery has a general formula (B): 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 ≦ 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is Mg, Ca, Al, Ti, V, Cr, Zr, 7. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the above. A positive electrode active material for a non-aqueous electrolyte secondary battery composed of lithium transition metal-containing composite oxide particles.
It is composed of secondary particles formed by agglomeration of multiple primary particles.
The secondary particles are present in the outer shell portion formed by the aggregated primary particles and inside the outer shell portion, are formed by the aggregated primary particles, and are electrically conductive with the outer shell portion. It has a porous structure including an agglomerated portion and a plurality of spatial portions dispersed in the agglomerated portion.
The average particle size MV of the secondary particles is in the range of 1 μm to 15 μm, and [(d90-d10) / average particle size MV], which is an index showing the spread of the particle size distribution of the secondary particles, is 0. .7 or less,
It has a BET specific surface area in the range of 2.0 m ² / g to 4.0 m ² / g and a tap density in the range of 1.0 g / cm ³ to 2.0 g / cm ³ .
The total area ratio of the plurality of spaces measured by observing the cross section of the secondary particles is in the range of 15% to 30% with respect to the cross-sectional area of the secondary particles.
Non-aqueous electrolyte Positive electrode active material for secondary batteries. The lithium transition metal composite oxide particles have the general formula (B): 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 ≦. 0.95, 0.05 ≦ y ≦ 0.55, 0 ≦ z ≦ 0.4, 0 ≦ t ≦ 0.1, M is Mg, Ca, Al, Ti, V, Cr, Zr, Nb, Mo , Hf, Ta, W), and a hexagonal crystal structure having a layered structure, according to claim 11. For positive electrode active material.

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