JP7444535B2 - Method for producing positive electrode active material for non-aqueous electrolyte secondary battery, and molded article - Google Patents

Description

The present invention relates to a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, and a molded article.

In recent years, with the spread of mobile devices such as mobile phones and notebook computers, there is a strong desire to develop small and lightweight secondary batteries with high energy density. Furthermore, environmentally friendly vehicles called xEVs are also undergoing a transition from hybrid vehicles (HEVs) to plug-in hybrid vehicles (PHEVs) and electric vehicles (BEVs), which require high-capacity secondary batteries. BEVs can travel a shorter distance on a single charge than gasoline vehicles, and to improve this problem, there is a need for higher capacity secondary batteries.

As a secondary battery that meets such requirements, there is a positive electrode active material for a non-aqueous electrolyte secondary battery, and a typical secondary battery is a lithium ion secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, etc., and the active material of the negative electrode and positive electrode is a material that can desorb and insert lithium.

Lithium-ion secondary batteries are currently undergoing active research and development, and among them, lithium-ion secondary batteries that use layered or spinel-type lithium metal composite oxide as the positive electrode material are 4V class. Since high voltage can be obtained, it is being put into practical use as a battery with high energy density.

The main materials that have been proposed so far include lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ), and lithium nickel cobalt manganese composite oxide (LiNi _{1/ 3} Co _1/3 Mn _1/3 O ₂ ), lithium manganese composite oxide using manganese (LiMn ₂ O ₄ ), and the like.

Among these, lithium nickel composite oxide (LiNiO ₂ ) has high capacity and high output, and is attracting attention as a material that satisfies the characteristics required as a positive electrode active material for secondary batteries of future environmentally friendly automobiles. Demand is rapidly increasing.

Furthermore, with the recent increase in demand for XEVs, there is a need for lower prices. For this reason, there is an increasing demand for lower costs for secondary batteries, which are one of the reasons for the high costs of environmentally friendly vehicles, and there is also a demand for lower costs for positive electrode active materials, which are one of the materials that make up lithium secondary batteries. It is being

Lithium-nickel composite oxide is obtained by mixing a nickel-containing compound such as nickel composite hydroxide or nickel composite oxide with a lithium compound to prepare a lithium mixture (raw material mixture), and then firing the lithium mixture. be able to. The lithium mixture is fired at a temperature of, for example, 650° C. or higher and 850° C. or lower for 3 hours or more. During this firing step, the lithium compound reacts (sinters) with the nickel-containing compound to obtain a lithium-nickel composite oxide having high crystallinity.

Generally, lithium mixture powder is placed in a container such as a sagger and fired in a firing furnace. However, when the powder is placed in a container and fired, heat conduction is poor and the displacement between the generated gas and the reaction gas is also poor, so it takes a long time to produce a lithium-nickel composite oxide with high crystallinity. Temperature raising and reaction time are required, and the total firing time including these steps becomes extremely long.

Several proposals have been made regarding firing conditions for efficiently firing lithium mixture powder.

For example, in Patent Document 1, in the step of filling a firing container with a mixture (powder) obtained by mixing a nickel composite compound and a lithium compound and firing it, in order to sufficiently diffuse oxygen into the mixture, By identifying the minimum holding time and oxygen concentration range for the volume (thickness when the mixture is placed in the firing container) in a specific temperature range, we can find a method for firing the mixture as efficiently as possible. It is shown.

Furthermore, several methods have been disclosed in which a lithium-nickel composite oxide is obtained by granulating a lithium mixture to obtain a granulated product or molding a lithium mixture to obtain a molded product and then firing the product.

For example, Patent Document 2 discloses that at least a predetermined amount of a nickel salt and a lithium salt are mixed to form a raw material mixture, and when the raw material mixture is fired to synthesize _LiNiO2 , the raw material mixture is granulated. A method for producing a LiNiO ₂ -based layered composite oxide is described, which is characterized by firing the product. Furthermore, in the example of Patent Document 2, after charging a granulated material of approximately 0.5 mm in an alumina container into a firing furnace, the temperature is raised to 700°C while introducing an oxidizing gas, and the temperature is maintained for 24 hours. It is described that a calcined composite is obtained by According to Patent Document 2, by the above manufacturing method, a composite having a desired crystal structure can be manufactured with high productivity including the work surface.

Furthermore, Patent Document 3 discloses that after a raw material mixture containing a lithium raw material is formed into a molded body through processes such as granulation formation, it is held at a temperature of 700°C to 1000°C for 2 to 15 hours in an oxidizing atmosphere. It is described that a lithium composite oxide is synthesized by firing. Furthermore, in the example of Patent Document 3, the raw material mixture was molded into pellets using a die press at a pressure of 2t/ ^cm2 , and the pellets were fired at 800°C for 10 hours in a pure oxygen atmosphere. Are listed.

In addition, in the example of Patent Document 4, a mixed powder of raw materials is press-molded into a molded body with a diameter of 50 mm and a thickness of 5 mm at a press pressure of 500 kg/ ^cm2 , and pieces of an alumina spacer with a thickness of 1 mm are press-molded. It is described that the material is placed in an appropriate place on the body, fired at 740°C for 10 hours, and then held and fired at 820°C for 20 hours. According to Patent Document 4, press molding is extremely useful in that it shortens the distance of intermolecular movement and promotes crystal growth during firing.

Further, Patent Document 5 describes that a raw material containing a lithium compound is made into a slurry, and a dried product obtained by spraying or freeze-drying is press-molded and then fired. Further, in the example of Patent Document 5, the dried gel is molded using a static compressor at 2 t/cm ² pressure to form pellets with a diameter of 14 mm and a thickness of 2 mm, which is then placed in an alumina boat and placed in a tube furnace. It is described that the material was fired at 750° C. for 48 hours in an oxygen atmosphere.

By the way, lithium hydroxide monohydrate is generally used as a lithium raw material for lithium-nickel composite oxide. However, lithium hydroxide monohydrate has a high moisture content, and a lot of moisture is generated from lithium hydroxide monohydrate during calcination, which may reduce the reactivity of the solid phase reaction or result in the positive electrode obtained. There is a tendency for variations in the composition of the active material to become large. Therefore, several methods have been reported in which the hydration water of lithium hydroxide monohydrate is removed and then the lithium hydroxide monohydrate is fired to reduce the rate of moisture generation during firing.

For example, Patent Document 6 describes the use of anhydrous lithium hydroxide, which has been vacuum-dried at 50° C. for 12 hours and then vacuum-dried at 200° C. for 8 hours to remove water of hydration, as a lithium raw material. Further, Patent Document 7 describes a method of removing hydration water of lithium hydroxide by heating at 450° C. for 15 minutes using a rotary kiln.

Japanese Patent Application Publication No. 2011-146309 Japanese Patent Application Publication No. 2000-072446 Japanese Patent Application Publication No. 11-135123 Japanese Patent Application Publication No. 06-290780 International Publication No. 98/06670 Japanese Patent Application Publication No. 2015-122299 Japanese Patent Application Publication No. 2006-265023

However, in the technique described in Patent Document 1, when the amount of mixed powder is increased to increase productivity, the heating time of the mixture becomes longer, and the replacement of the generated gas and the reaction gas becomes worse, so the firing time is increased. It becomes long and there is a limit to productivity.

Furthermore, in the technique described in Patent Document 2, since the granules are filled in a container and fired, heat conduction may not be sufficient. In addition, in the case of powder of a lithium mixture or granules with a particle size of less than 1 mm as described in Patent Document 2, for example, in order to increase the firing efficiency, when the atmospheric gas flow rate in the firing furnace is increased, powder or Granules may fly up from the container, reducing yield.

Furthermore, in the techniques described in Patent Documents 3 to 5, a larger molded body is formed and fired, but the firing conditions specifically disclosed as examples require a firing time of 10 hours or more. , there is a problem of poor productivity.

On the other hand, when lithium hydroxide from which water has been removed (e.g., anhydrous lithium hydroxide) is used as a lithium raw material, it is thought that there is a cost reduction effect due to improved firing productivity. With this technology, it takes as much as 20 hours to remove the hydration water contained in lithium hydroxide, and it also requires investment in equipment and man-hours, so the cost reduction is not large. In addition, with the technology described in Patent Document 6, it is possible to remove the hydration water of lithium hydroxide hydrate in a short time of 15 minutes, but it is necessary to raise the temperature to a high temperature of 450 ° C. Because of the costs, energy costs, and post-processing cooling costs, large cost reductions cannot be expected.

In view of the above-mentioned problems, an object of the present invention is to provide a simple method for producing a positive electrode active material with higher productivity and high crystallinity, and a molded article that can be suitably used in the production method. shall be.

According to a first aspect of the present invention, there is provided a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium-nickel composite oxide, the method comprising: a nickel composite oxide and a lithium hydroxide monohydrate; Mixing to obtain a lithium mixture; Molding the lithium mixture to obtain a molded body with a density of 1.3 g/cm ³ or more; and firing the molded body at a temperature of 650°C or higher and 850°C or lower in an oxidizing atmosphere. The lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), and aluminum (Al), and the atomic ratio of each element is Li:Ni. :Co:Al=s:(1-x-y):x:y (however, 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y≦0.10 ) A method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery is provided.

Moreover, the moisture content of lithium hydroxide monohydrate may be 42% by mass or more and 48% by mass or less. Further, the density of the molded body may be 1.4 g/cm ³ or more. Moreover, the maximum value of the distance between two points on the outer shape of the molded article may be 1 mm or more. Further, the firing may be performed by placing the molded body on a plate-shaped member placed in a firing furnace. The method may also include crushing the fired product after firing. Further, the fired product after crushing may be washed with water and dried. Further, in the firing, the firing temperature may be maintained for 3 hours or less. In addition, the lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), aluminum (Al), and other elements M, and the atomic ratio of each element is Li: Ni:Co:Al:M=s:(1-x-y):x:y:z (however, 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦ y≦0.10, 0<z≦0.1, M may be represented by an element other than Li, Ni, Co, Al, and O). Further, the amount of lithium eluted into the supernatant liquid after dispersing 5 g of lithium-nickel composite oxide in 100 ml of pure water and allowing it to stand for 10 minutes is 0.11% by mass or less based on the total amount of lithium-nickel composite oxide. Good too. Further, the lithium nickel composite oxide may have a lithium site occupancy rate of 97.0% or more at the 3a site obtained from Rietveld analysis of the X-ray diffraction pattern.

According to the second aspect of the present invention, nickel (Ni), cobalt (Co), and aluminum (Al) are included, and the molar ratio of each element is Ni:Co:Al=(1-xy ):x:y (0.03≦x≦0.10, 0.03≦y≦0.10); and lithium hydroxide monohydrate. , a molded article is provided which does not contain a binder, has a maximum distance between two points on the outer shape of 1 mm or more, and has a density of 1.3 g/cm ³ or more.

According to the present invention, it is possible to provide a simple method for producing a positive electrode active material with higher productivity and high crystallinity, and a molded body that can be suitably used in the production method.

FIG. 1 is a diagram showing an example of a method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery. FIG. 2 is a diagram showing an example of a method for producing a nickel composite oxide. FIGS. 3(A) to 3(D) are diagrams showing an example of a molded article. FIG. 4(A) is a diagram showing an example of a molded body placed on a plate-like member, and FIG. 4(B) is a diagram showing an example of a lithium mixture powder placed in a container (casing). It is a diagram. FIG. 5 is a diagram illustrating an example of a treatment process for the lithium-nickel composite oxide after firing. FIG. 6 is a diagram showing a secondary battery for evaluation used in Examples. FIG. 7 is a diagram showing the relationship between the density of the molded body and the temperature increase rate.

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below. In the drawings, the drawings may be expressed schematically or with a changed scale, as appropriate.

1. Manufacturing method of positive electrode active material for non-aqueous electrolyte secondary battery]
The present embodiment is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as "positive electrode active material") containing a lithium-nickel composite oxide. The lithium-nickel composite oxide has an atomic ratio of lithium (Li), nickel (Ni), cobalt (Co), and aluminum (Al) such that Li:Ni:Co:Al=s:(1-xy ):x:y (0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y≦0.10). Further, the lithium-nickel composite oxide (hereinafter also simply referred to as "composite oxide") has a layered crystal structure and may include secondary particles formed by agglomeration of primary particles.

FIG. 1 is a diagram showing an example of a method for manufacturing a positive electrode active material according to the present embodiment. As shown in FIG. 1, the method for producing a positive electrode active material includes, for example, obtaining a lithium mixture containing a nickel composite oxide and lithium hydroxide monohydrate (mixing step: step S10), and lithium The method includes molding the mixture to obtain a molded body (molding process: step S20) and firing the molded body (firing process: step S30). In the manufacturing method according to the present embodiment, by using lithium hydroxide monohydrate as a lithium raw material, the cost is lower than using anhydrous lithium hydroxide, the productivity is high, and the lithium metal composite oxide (positive electrode active material ) can be manufactured. Each step will be explained below.

[Mixing process: Step S10]
First, a nickel composite oxide and lithium hydroxide monohydrate are mixed to obtain a lithium mixture (step S10). By using the nickel composite oxide as a raw material (precursor), the manufacturing method of the present embodiment can yield a highly crystalline lithium-nickel composite oxide with high productivity in a very short firing time. Each raw material used in the mixing step (step S10) will be explained below.

(nickel composite oxide)
Nickel composite oxide is an oxide containing nickel, cobalt, and aluminum (hereinafter also referred to as "nickel cobalt aluminum composite oxide"). Further, the nickel composite oxide may contain other elements M in addition to nickel, cobalt, and aluminum, such as molybdenum, tungsten, silicon, boron, niobium, vanadium, titanium, etc. can be mentioned.

The nickel composite oxide contains, for example, nickel (Ni), cobalt (Co), and aluminum (Al), and the atomic ratio (molar ratio) of each element is Ni:Co:Al=(1-x -y):x:y (0.03≦x≦0.10, 0.03≦y≦0.10). Note that the ratio of each element contained in the nickel composite oxide is inherited to the molded body and the lithium-nickel composite oxide. Therefore, the composition of the entire nickel composite oxide can be the same as the composition of metals other than lithium in the lithium-nickel composite oxide to be obtained.

Further, the nickel composite oxide may contain nickel (Ni), cobalt (Co), aluminum (Al), and other elements M, and the atomic ratio (molar ratio) of each element is Ni :Co:Al:M=(1-x-y):x:y:z(0.03≦x≦0.10, 0.03≦y≦0.10, 0≦z≦0.10, M may be represented by an element other than Ni, Co, Al, and O). Further, the element M may be, for example, at least one of molybdenum, tungsten, silicon, boron, niobium, vanadium, and titanium.

Nickel composite oxide can be obtained, for example, by oxidizing nickel composite hydroxide used as a precursor of a positive electrode active material. When a nickel composite oxide is used, the amount of water vapor generated during firing of the lithium mixture is reduced, the reaction progresses much more easily, and the firing time can be significantly shortened. An example of a method for producing a nickel composite oxide will be described below. Note that the nickel composite oxide may be obtained by other manufacturing methods.

FIG. 2 is a diagram showing an example of a method for producing a nickel composite oxide. For example, as shown in FIG. 2, the nickel composite oxide can be obtained by a method comprising oxidizing and roasting the nickel composite hydroxide obtained by crystallization (step S1) (step S2). The nickel composite hydroxide obtained by crystallization has a uniform composition throughout the particles, and the composition of the finally obtained positive electrode active material also becomes uniform. Note that the nickel composite oxide may be obtained by a method other than crystallization. Each step of manufacturing the nickel composite oxide will be explained below.

[Crystallization process; Step S1]
Nickel composite hydroxide is produced by supplying a neutralizing agent etc. to an aqueous solution containing a salt containing nickel (Ni salt), a salt containing cobalt (Co salt), and a salt containing aluminum (Al salt). It is obtained by crystallizing (step S1). As a specific example, a crystallization reaction is performed by neutralizing an aqueous solution containing a nickel salt, a cobalt salt, and an aluminum salt with an alkaline aqueous solution in the presence of a complexing agent such as an ammonium ion donor while stirring the aqueous solution. It can be manufactured by The nickel composite hydroxide obtained by the crystallization method is composed of secondary particles in which primary particles are aggregated, and the positive electrode active material obtained using these nickel composite hydroxide particles as a precursor is also composed of primary particles in which they aggregate. It is composed of secondary particles.

As the metal salt used when preparing the aqueous solution containing the metal salt, for example, sulfates, nitrates, and chlorides of Ni, Co, and Al can be used. Further, the aqueous solution of the metal salt may include a salt containing a metal M other than nickel, cobalt, and aluminum.

The nickel composite hydroxide can contain nickel (Ni), cobalt (Co), and optionally another metal (M), and the molar ratio of each element is Ni:Co:Al:M=( 1-xy):x:y:z (0.03≦x≦0.10, 0.03≦y≦0.10, 0≦z≦0.10). The ratio of each element contained in the nickel composite hydroxide is inherited to the nickel composite oxide, the molded body, and the lithium-nickel composite oxide. Therefore, the composition of the entire nickel composite hydroxide can be the same as the composition of metals other than lithium in the lithium-nickel composite oxide to be obtained.

Note that the crystallization method is not particularly limited, and for example, continuous crystallization method, batch method, etc. can be used. The continuous crystallization method is, for example, a method of continuously recovering nickel composite hydroxide overflowing from a reaction vessel, and can easily produce a large amount of nickel composite hydroxide having the same composition. Further, since the nickel composite oxide obtained by the continuous crystallization method has a wide particle size distribution, it is possible to improve the packing density of a molded body obtained using the nickel composite oxide. Note that the particle size of the nickel composite hydroxide is, for example, 1 μm or more and 50 μm or less.

The batch method can obtain a nickel composite hydroxide having a more uniform particle size and a narrow particle size distribution. A molded body obtained using a nickel composite hydroxide obtained by a batch method can react more uniformly with a lithium compound (lithium hydroxide monohydrate) during firing. Further, the nickel composite hydroxide obtained by the batch method can reduce the contamination of fine powder, which is one of the causes of deterioration of cycle characteristics and output characteristics when used in a secondary battery.

[Oxidation roasting: Step S2]
Next, the nickel composite hydroxide is subjected to oxidative roasting (heat treatment) to obtain a nickel composite oxide (step S2). The conditions for oxidative roasting are not particularly limited as long as most of the nickel composite hydroxide is converted to nickel composite oxide, but for example, the temperature for oxidative roasting is 600°C or higher and 800°C or lower. It is preferable. When the temperature of oxidative roasting is less than 600° C., moisture may remain in the nickel composite hydroxide (precursor) and oxidation may not proceed sufficiently. On the other hand, when the temperature of oxidative roasting exceeds 800° C., composite oxides may bind together to form coarse particles. Furthermore, if the temperature of oxidative roasting is too high, a large amount of energy is used, which lowers productivity from the viewpoint of cost and is not industrially appropriate.

The oxidative roasting time is preferably, for example, 0.5 hours or more and 3.0 hours or less. If the oxidative roasting time is less than 0.5 hours, the oxidation of the nickel composite hydroxide may not proceed sufficiently. On the other hand, when the oxidative roasting time exceeds 3.0 hours, the energy cost increases, productivity decreases, and it is not industrially suitable.

(Lithium hydroxide monohydrate)
As the lithium compound, lithium hydroxide monohydrate (LiOH.H ₂ O) is used. When lithium hydroxide monohydrate is used, it has higher reactivity during sintering than when lithium carbonate or the like is used. Furthermore, when lithium hydroxide monohydrate is used as the lithium compound, the properties of lithium hydroxide bind, so a binder is not necessary depending on the molding conditions. When the lithium mixture does not contain a binder, contamination of impurities into the positive electrode active material can be further suppressed.

When lithium hydroxide having hydration water is used as a lithium raw material, more water is generated during firing than when anhydrous lithium hydroxide is used. When the oxygen concentration in the lithium mixture and in the sintering atmosphere decreases due to the generated moisture, the sintering reaction may become difficult to proceed. However, in the manufacturing method of the present embodiment, by molding the lithium mixture (step S20) and firing it (step S30), even when using lithium hydroxide having hydration water, crystallization can be achieved in a short time by firing. A lithium metal composite oxide (positive electrode active material) having high properties and sufficient quality can be obtained. The reason for this is, although not particularly limited, that the space inside the molded body is appropriately reduced, the moisture (generated gas) inside the molded body is discharged faster, and oxygen (reactive gas) is more easily introduced into the molded body. It is thought that this was due to an accident.

Moreover, it is preferable that the moisture content of lithium hydroxide monohydrate is 42% by mass or more and 48% by mass or less. Note that the moisture content is the amount including hydration water. Moreover, the moisture content is calculated by measuring the weight before and after vacuum drying, assuming that the moisture content obtained by vacuum drying the lithium hydroxide to be measured at 200° C. for 8 hours is 0% by mass. Furthermore, from the viewpoint of reducing impurities, lithium hydroxide monohydrate having a total carbon content of 1.0% or less is preferable. Note that the total carbon (total carbon content) is a value that can be measured by high frequency combustion-infrared absorption method.

(lithium mixture)
The mixing ratio of the nickel composite oxide and lithium hydroxide monohydrate is determined by the ratio of the total number of atoms of nickel, cobalt, and aluminum (Me) to the number of lithium atoms (Li) in the nickel composite oxide (Li /Me ratio) is in the range of more than 0.93 and less than 1.03. If the Li/Me ratio is 0.93 or less, some of the nickel composite oxide may remain unreacted in the firing process (step S30), and sufficient battery performance may not be obtained. On the other hand, when the Li/Me ratio is 1.03 or more, sintering is promoted in the firing process (step S30), and the fired product becomes hard and difficult to crush, and the resulting lithium-nickel composite oxide If the particle size or crystallite size of the battery becomes too large, sufficient battery performance may not be obtained.

Since the required value of the Li/Me ratio differs depending on the configuration of the secondary battery, etc., the value of the Li/Me ratio can be appropriately set within the above range according to the request. The value of the Li/Me ratio may be, for example, 0.95 or more and less than 1.03, 1.0 or more and less than 1.03, and more than 1.0 and less than 1.03. There may be.

Further, since the Li/Me ratio does not substantially change before and after the firing step (step S30), the Li/Me ratio in the lithium mixture is substantially maintained even in the lithium-nickel composite oxide. Therefore, the mixing ratio of the nickel composite oxide and lithium hydroxide monohydrate can be adjusted as appropriate so that it becomes the same as the Li/Me ratio in the lithium-nickel composite oxide to be obtained.

A general mixer can be used to mix the nickel composite oxide and lithium hydroxide monohydrate, and for example, a shaker mixer, Loedige mixer, Julia mixer, V blender, etc. can be used. Further, this mixing may be done sufficiently as long as the skeleton of the nickel composite oxide is not destroyed. If the mixing is insufficient, the Li/Me ratio may vary among individual particles, which may cause problems such as insufficient battery characteristics.

(binder)
The lithium mixture may also include a binder. When a binder is included, the moldability of the lithium mixture is improved, and molded bodies of various shapes can be easily formed. As the binder, a known binder can be used, and for example, polyvinyl alcohol, polyacrylamide, carboxymethyl cellulose, etc. can be used. Among these, it is preferable to use polyvinyl alcohol.

The content of the binder in the lithium mixture can be, for example, 0.05% by mass or more and 0.2% by mass or less, preferably 0.08% by mass or more and 0.12% by mass or less, based on the total amount of the lithium mixture. . When the content of the binder is within the above range, a molded article having appropriate strength can be produced. If the binder content is too large, the adhesive strength of each particle that makes up the molded body becomes too strong, which may reduce the efficiency of exhausting the gas produced by the reaction between lithium and nickel composite oxide, or cause the binder to decompose. As a result, the amount of carbon dioxide gas generated increases, and the generated gas cannot be discharged inside the molded body, and the internal pressure of the molded body increases, which may cause the molded body to fracture.

The lithium mixture may also be binder-free. When lithium hydroxide monohydrate is used as the lithium compound, a molded body can be formed using only the nickel composite oxide and lithium hydroxide without using a binder. When a binder is not used, the content of impurities (eg, carbon, etc.) in the obtained lithium-nickel composite oxide can be reduced.

[Formation of molded body: Step S20]
Next, the lithium mixture is molded to obtain a molded body having a density of 1.3 g/cm ³ or more (step S20). By forming and densifying the lithium mixture in this way, the contact area between the particles of the lithium mixture increases, improving heat transfer. Furthermore, by reducing the voids between the particles, moisture and generated gases within the lithium mixture are reduced. The molded body can be easily discharged, heat and reaction gas can be efficiently supplied into the molded body, and the molded body can be fired efficiently in a very short time.

(Density of molded body)
The density of the molded body is preferably 1.3 g/cm ³ or more, more preferably 1.4 g/cm ³ or more. When the density of the molded body is less than 1.3 g/cm ³ , the strength of the molded body is low and may collapse during handling. Furthermore, if the density of the molded product is less than 1.4 g/cm ³ , the yield may decrease due to chipping at corners and ridges. On the other hand, the upper limit of the density of the molded body is not particularly limited, and may be a density that maintains the particle structure of the nickel composite oxide, and may be, for example, 2.3 g/cm ³ or less. Note that if the particle structure of the nickel composite oxide in the molded body collapses, the battery characteristics of the resulting positive electrode active material will deteriorate. In addition, the density of the molded body can be made into the said range by adjusting the surface pressure at the time of manufacturing a molded body, for example.

The density of the molded body may be, for example, 1.3 g/cm ³ or more and 2.0 g/cm ³ or less. When the density of the compact is within the above range, the heat transfer to the inside of the compact during the firing process (step S30) is very good (see FIG. 7).

Furthermore, as will be described later, when crushing (step S40, see FIG. 5) after firing (step S30), if the density of the compact is too high, the crushability after firing will be poor and the particle size distribution will be broad. It may become. Therefore, from the viewpoint of achieving both reactivity in the firing process (step S30) and crushability in the crushing process (step S40), the density of the compact is preferably 1.4 g/cm3 or ^more and 1.7 g/cm3 or more. cm ³ or less, more preferably 1.4 g/cm ³ or more and 1.6 g/cm ³ or less, even more preferably 1.4 g/cm ³ or more and 1.5 g/cm ³ or less.

(Shape of molded object)
FIG. 3 is a diagram showing an example of a molded body used in this embodiment. The shape of the molded body 10 is not particularly limited, and may be a briquette, a pellet, a tablet, a plate, a spherical shape, etc. For example, as shown in FIGS. 3(A) to 3(C), it is approximately circular. It may be columnar or roughly elliptical, or it may be plate-like (plate-like) as shown in FIG. 3(D). In addition, from the viewpoint of productivity, the shape of the molded body 10 is preferably a plate shape (plate shape), which allows for high filling into the firing apparatus.

(Size of molded object)
The size of the molded body is not particularly limited, and may be within a range that allows the molded body to be formed. For example, if the maximum distance between two points on the outline of the molded body is 1 mm or more, The yield in the manufacturing process can be 90% or more. Further, the upper limit of the size of the molded body is not particularly limited, and can be appropriately selected according to the shape inside the firing furnace. In addition, from the viewpoint of improving handling properties and productivity, the maximum value of the distance between two points on the outer shape of the molded object is preferably 10 mm or more and 1000 mm or less, more preferably 50 mm or more and 500 mm or less, and 100 mm or more and 500 mm or less. is even more preferable. In addition, as shown in the examples described later, a molded product in which the distance between two points on the outer shape of the molded product is within the range of 100 mm or more and 500 mm or less has a similar high thermal conductivity, so it is easy to generate. From the viewpoint of further improving the temperature, the maximum value of the distance between two points on the outer shape of the molded article may be 350 mm or more and 500 mm or less.

For example, as shown in FIG. 4(C), when the molded body 10 is plate-shaped, the thickness (t) of the molded body 10 is preferably 5 mm or more and 200 mm or less, more preferably 10 mm. It is not less than 100 mm. Further, the area of the cross section perpendicular to the thickness direction of the molded body 10 may be, for example, 10 mm ² or more and 1000 mm ² or less, or 100 mm ² or more and 10000 mm ² or less.

The apparatus for producing the molded body is not particularly limited, and any apparatus that can pressurize the lithium mixture may be used, and for example, a granulator, tablet machine, briquette machine, press, etc. can be used. For example, when producing a plate-shaped molded body having long and short sides of 10 mm or more and 100 mm or less and a thickness of 5 mm or more and 200 mm or less, it is preferable to use a hydraulic press machine.

The surface pressure during molding (step S20) is adjusted as appropriate depending on the composition of the lithium mixture, the powder characteristics of the raw material, the shape of the molded body, etc. For example, when obtaining a plate-shaped molded product, the surface pressure during forming may be 100 kg/cm ² or more and 2000 kg/cm ² or less, or 150 kg/cm ² or more and 1500 kg/cm ² or less. Moreover, when the lithium mixture does not contain a binder, the surface pressure may be 200 kg/cm ² or more.

[Baking: Step S30]
Next, the obtained molded body is fired in an oxygen atmosphere at a temperature of 650° C. or higher and 850° C. or lower (firing step, step S30). By firing the compact, the nickel composite oxide and lithium hydroxide monohydrate react to produce a lithium-nickel composite oxide. By firing the above-mentioned compact at the above-mentioned temperature, a lithium-nickel composite oxide (positive electrode active material) having high crystallinity equal to or higher than conventional ones can be obtained in a much shorter time than conventional firing times. .

The firing conditions are not particularly limited as long as the nickel composite oxide and lithium hydroxide monohydrate in the compact react to form a lithium-nickel composite oxide, but for example, the temperature can be set to room temperature. It is preferable to gradually increase the temperature from 650°C to 850°C and maintain the temperature for 3 hours or less. If the firing temperature is lower than 650°C, lithium will not diffuse sufficiently, leaving particles of unreacted lithium hydroxide monohydrate, or the crystal structure of the lithium-nickel composite oxide will not be well-organized. Therefore, a secondary battery using the obtained positive electrode active material may not have sufficient battery characteristics. On the other hand, if the firing temperature is higher than 850° C., intense sintering occurs between the lithium-nickel composite oxide particles and abnormal grain growth occurs, which may reduce the specific surface area. Further, the specific surface area of the positive electrode active material may decrease, and the resistance of the positive electrode in the secondary battery may increase, resulting in a decrease in battery capacity. The firing temperature can be adjusted as appropriate depending on the composition and shape of the molded body, and may be 700°C or higher and 800°C, or 730°C or higher and 770°C or lower.

The time for holding the compact at the above firing temperature (hereinafter also referred to as "holding time") is not particularly limited as long as a lithium-nickel composite oxide with high crystallinity is formed, but for example, it is 5 hours or less. It is preferably 3 hours or less, more preferably 2.5 hours or less, and may be less than 2.5 hours. The shorter the firing time, the better the productivity. Further, the lower limit of the firing time is, for example, 1 hour or more, and may be 2 hours or more.

The heating rate of the firing furnace is, for example, 3°C/min or more, preferably 3.5°C/min or more, and more preferably 4°C/min or more from the viewpoint of productivity. If the heating rate of the firing furnace is less than 3° C./min, the firing time will become long and no improvement in productivity can be expected. Further, the upper limit of the heating rate of the firing furnace is not particularly limited, but may be 6° C./min or less, or may be 5° C./min or less. If the temperature increase rate exceeds 6° C./min, the temperature increase inside the molded body is delayed and the reaction does not proceed sufficiently, which may result in a decrease in product quality.

Further, the temperature increase rate of the firing furnace may be adjusted as appropriate in accordance with the temperature increase rate of the center portion of the molded body when the temperature is rapidly increased. For example, the heating rate of the firing furnace may be adjusted within the range of ±1°C/min, or ±0.5°C/min, relative to the heating rate at the center of the compact when the temperature is rapidly raised. It may be adjusted within a range of minutes. By adjusting the temperature increase rate of the firing furnace in accordance with the temperature increase rate of the compact, the rate of the sintering reaction can be kept within an appropriate range, and the generated gas can be efficiently replaced with the reaction gas.

Further, the rate of temperature increase at the center of the molded body until the firing temperature is reached is not particularly limited, and is, for example, 3°C/min or higher, preferably 3.5°C/min or higher, and preferably 4°C/min or higher. It's more than a minute. Further, the upper limit of the temperature increase rate at the center of the molded body is not particularly limited, and may be 6° C./min or less, or 5° C./min or less. Note that the rate of temperature increase at the center of the molded body can be measured by inserting a thermocouple into the center of the molded body.

The atmosphere during firing is preferably an oxidizing atmosphere having an oxygen concentration higher than the atmospheric atmosphere, more preferably an atmosphere with an oxygen concentration of 80% by volume or more, and may have an oxygen concentration of 100% by volume. . That is, the firing is preferably performed in an oxygen stream. If the oxygen concentration in the atmosphere during firing is less than 80% by volume, the amount of oxygen required for the reaction between the nickel composite oxide and lithium hydroxide monohydrate cannot be supplied, and the lithium-nickel composite oxide is not sufficiently formed. It may not be possible.

The firing furnace is not particularly limited as long as it can heat in an oxygen stream, and a vertical furnace, a rotary hearth furnace, a roller hearth kiln, etc. can be used. Among these, it is preferable to use a roller hearth kiln from the viewpoint of equipment investment and running cost.

FIG. 4(A) is a diagram showing a state in which the molded body 10 is placed on the plate-like member 1 during firing, and FIG. 4(B) is a diagram showing a state in which the lithium mixture powder 20 is placed in the container 2 during firing. FIG. Conventionally, when firing a lithium mixture powder 20 or granules, the powder or granules are placed in a container 2 such as a sagger and fired, as shown in FIG. 4(B).

At the time of firing, the molded body 10 may be placed in the container 2 and fired as in the conventional method, but the molded body 10 may be placed directly in the plate member 1 (e.g., setter) placed in the firing furnace without using the container 2. The body 10 may be placed and fired. Note that the setter is a member (furnace material) with which the molded body comes into contact in the firing furnace, and as shown in FIG. It is preferable that there be. When using the plate member 1 without using the container 2, it is possible to increase the contact area between the molded body 10 and the atmospheric gas to further promote the reaction between the precursor and lithium hydroxide monohydrate. In addition, the amount of raw materials input into the firing furnace can be increased.

FIG. 5 is a diagram showing an example of a process for treating the lithium-nickel composite oxide obtained after firing. As shown in FIG. 5, the method for producing a positive electrode active material according to the present embodiment includes crushing the lithium nickel composite oxide (fired product) obtained after the firing step (step S30) to create a crushed product (lithium nickel composite oxide). oxide powder) (crushing process: step S40), washing and filtering the crushed material with water (water washing process: step S50), and drying the washed lithium-nickel composite oxide (drying process). :Step S60). Note that the method for producing a positive electrode active material according to the present embodiment may not include the above-described crushing (step S40), washing with water (step S50), and drying step (step S60), or may include these three steps. At least one of these steps may be included. Each step will be explained below.

[Crushing process: Step S40]
The lithium-nickel composite oxide (fired product) obtained after firing (step S30) may be further crushed (step S40). By crushing, the secondary particles of the lithium-nickel composite oxide that are agglomerated or slightly sintered can be separated, and the average particle size and particle size distribution of the resulting positive electrode active material can be adjusted to a suitable range. . Further, when the molded body is fired, the fired product that is obtained maintains the shape at the time of molding, so it is preferable to crush it (step S40). Note that crushing is a process in which mechanical energy is applied to an aggregate consisting of multiple secondary particles that is generated due to sinter necking between secondary particles during firing, without destroying the secondary particles themselves. This refers to the operation of separating and loosening aggregates.

As a method of crushing, known means can be used, such as a pin mill, a hammer mill, a crusher with a classification function, etc. In addition, at this time, it is preferable to adjust the crushing force to an appropriate range so as not to destroy the secondary particles.
[Water washing process: Step S50]
Next, the obtained crushed material may be washed with water (step S50). By washing the lithium-nickel composite oxide (crushed product) with water, excess lithium and impurities on the surface of the lithium-nickel composite oxide particles are removed, creating a positive electrode active for non-aqueous electrolyte secondary batteries with higher capacity and higher thermal stability. substance can be obtained. Here, the washing method is not particularly limited, and known techniques can be used.

As a washing method, for example, lithium-nickel composite oxide (crushed material) is added to water to form a slurry, and the slurry is stirred so that excess lithium on the surface of the lithium-nickel composite oxide particles is sufficiently removed. It is preferable. After stirring, solid-liquid separation is performed and dried as described later (step S60), whereby a lithium-nickel composite oxide can be obtained.

As for the slurry concentration, preferably 0.5 to 2 parts by mass of lithium-nickel composite oxide (crushed material) is added to 1 part by mass of water. If the slurry concentration exceeds 2 parts by mass of crushed material per 1 part by mass of water, the viscosity will become very high and stirring will be difficult, and the alkalinity (pH) of the liquid will be high, so there will be no equilibrium relationship. This may slow down the dissolution rate of deposits or make it difficult to separate them from the powder even if they peel off. On the other hand, if the slurry concentration is less than 0.5 part by mass of crushed material per 1 part by mass of water, the slurry is too dilute and a large amount of lithium is eluted, resulting in crystallization of lithium-nickel composite oxide (crushed material). Lithium also begins to be desorbed from the lattice, making the crystal more likely to collapse, and the high pH aqueous solution (slurry) absorbs carbon dioxide gas from the atmosphere, causing lithium carbonate to form on the surface of the lithium-nickel composite oxide. may re-precipitate.

The cleaning liquid used in the water washing step (step S50) is not particularly limited, and for example, water may be used. When using water, for example, water with an electrical conductivity of less than 10 μS/cm is preferred, and water with an electrical conductivity of 1 μS/cm or less is more preferred. When using water with an electrical conductivity measurement of less than 10 μS/cm, deterioration in battery performance due to adhesion of impurities to the positive electrode active material can be further suppressed.

When the slurry is subjected to solid-liquid separation, it is preferable that the amount of adhering water remaining on the particle surface of the lithium nickel composite oxide is small. When there is a large amount of attached water, lithium dissolved in the liquid (slurry) may redeposit, and the amount of lithium present on the surface of the lithium-nickel composite oxide after drying (step S60) may increase. For solid-liquid separation, commonly used centrifuges, filter presses, etc. are used.

[Drying process: Step S60]
After washing with water (step S50), a lithium-nickel composite oxide (positive electrode active material) may be obtained by drying (step S60). Drying conditions are not particularly limited as long as at least part of the water in the lithium nickel composite oxide is removed. In the drying step (step S60), for example, the lithium-nickel composite oxide (powder) after filtration (solid-liquid separation) can be dried under a gas atmosphere that does not contain compound components containing carbon and sulfur, or under a vacuum atmosphere. It is preferable to use a machine at a predetermined temperature.

The drying temperature is preferably 80°C or higher and 550°C or lower, more preferably 120°C or higher and 350°C or lower. When the drying temperature is 80° C. or higher, the positive electrode active material after washing with water (step S50) can be quickly dried, and a gradient in lithium concentration between the particle surface and the inside of the particle can be suppressed. On the other hand, when the drying temperature exceeds 550°C, the lithium-nickel composite oxide near the surface is expected to have a very close to stoichiometric ratio or a state close to a charged state due to some lithium desorption. This may cause the crystal structure to collapse, leading to a decrease in battery characteristics in the secondary battery.

Further, the drying temperature is more preferably 120° C. or higher and 350° C. or lower from the viewpoint of productivity and thermal energy cost.

[Characteristics of positive electrode active material]
By the method for producing a positive electrode active material according to the present embodiment described above, a lithium-nickel composite oxide (positive electrode active material) with excellent crystallinity can be obtained with high productivity by firing in a very short time. Hereinafter, the characteristics of the lithium-nickel composite oxide (positive electrode active material) obtained by the manufacturing method according to the present embodiment will be explained.

(composition)
The lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), and aluminum (Al), and the molar ratio of each metal element is Li:Ni:Co:Al=s:(1 -xy):x:y (0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y≦0.10).

In addition, the lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), aluminum (Al), and other elements M, and the atomic ratio of each element is Li: Ni:Co:Al:M=s:(1-x-y):x:y:z (however, 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦ y≦0.10, 0<z≦0.1, M may be represented by an element other than Li, Ni, Co, Al, and O).

In addition, the lithium nickel composite oxide has a hexagonal crystal structure having a shape structure, for example, the general formula (1): Li _s Ni _1-xy Co _x Al _y M _z O _2+α (however, In formula (1), 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y≦0.10, 0≦z≦0.10, -0.5≦α ≦0.5, and M is at least one element selected from Mn, V, Mo, Nb, Ti, and W.). Further, the element M may be, for example, at least one of molybdenum, tungsten, silicon, boron, niobium, vanadium, and titanium.

(Lithium seat occupancy rate)
In the lithium-nickel composite oxide, for example, the lithium site occupancy of the 3a site, which is the lithium-based layer, obtained from Rietveld analysis of the X-ray diffraction pattern is 95% or more, preferably 96% or more, and more preferably It is 97% or more. If the lithium seat occupancy is within the above range, the sintering reaction between the precursor and the lithium hydroxide monohydrate is sufficiently carried out in the firing process (step S30), and the lithium nickel composite oxide is highly crystalline. Indicates that the person has sex. When a highly crystalline lithium-nickel composite oxide is used as a positive electrode active material in a secondary battery, it exhibits excellent battery characteristics (high battery capacity, etc.).

(Amount of eluted lithium)
In the lithium-nickel composite oxide, when the lithium-nickel composite oxide is dispersed in water, the amount of lithium eluted into water (the amount of eluted lithium) is, for example, 0.11% by mass based on the total amount of the lithium-nickel composite oxide. or less, preferably 0.10% by mass or less, and more preferably 0.05% by mass or less. Note that the amount of eluted lithium can be measured by a neutralization titration method. Note that when performing the water washing step (step S50), the amount of eluted lithium is a value measured using the lithium-nickel composite oxide obtained after washing with water (step S50) and drying (step S60).

The eluted lithium is thought to originate from unreacted lithium hydroxide monohydrate present on the particle surface of the lithium-nickel composite oxide (positive electrode active material), lithium present in excess in the crystal, and the like. In other words, the amount of eluted lithium can be used as an indicator of the remaining amount of unreacted lithium hydroxide monohydrate derived from the raw material, and the smaller the amount of eluted lithium, the more unreacted lithium hydroxide monohydrate. The remaining amount of hydrate is small, and it can be said that the sintering reaction between the precursor and lithium hydroxide monohydrate is progressing. Furthermore, the smaller the amount of eluted lithium, the more it is possible to suppress gelation of the positive electrode composite material paste.

The amount of lithium eluted is determined by dispersing 15 g of lithium-nickel composite oxide in 75 ml of pure water, allowing it to stand for 10 minutes, diluting 10 ml of the supernatant liquid with 50 ml of pure water, and calculating the amount of lithium eluted in water ( This value is calculated by measuring the amount of eluted lithium by neutralization titration method by adding 1 mol/liter of hydrochloric acid.

(Initial charge/discharge efficiency)
The initial charge/discharge efficiency (initial discharge capacity/initial charge capacity) of the 2032-type coin-type battery CBA for evaluation (see FIG. 9) manufactured using lithium-nickel composite oxide as the positive electrode active material is, for example, 85%. or more, preferably 88% or more, more preferably 88.5% or more. If the initial charge/discharge efficiency is within the above range, the sintering reaction between the precursor and the lithium hydroxide monohydrate is sufficiently performed in the firing process (step S30), and the lithium-nickel composite oxide has a high crystallinity. Indicates that the person has sex. The initial discharge capacity efficiency was determined by leaving the coin-type battery CBA used in the example for about 24 hours after manufacturing, and after the open circuit voltage OCV (Open Circuit Voltage) stabilized, the current density for the positive electrode was set to 0.1 mA. / ^cm2 , the capacitance was measured when the battery was charged to a cutoff voltage of 4.3V, and then discharged to a cutoff voltage of 3.0V after a one-hour rest.

2. Molded object The molded object according to the present embodiment includes a nickel composite oxide and lithium hydroxide monohydrate. The molded body according to this embodiment can be suitably used as a positive electrode active material of a secondary battery by firing to form a lithium-nickel composite oxide.

The nickel composite oxide contains nickel (Ni), cobalt (Co), and aluminum (Al), and the molar ratio of each element is Ni:Co:Al=(1-xy):x:y (0.03≦x≦0.10, 0.03≦y≦0.10). The composition and characteristics of the nickel composite oxide are the same as those of the metal elements contained in the nickel composite oxide in the above-described method for producing a positive electrode active material, so description thereof will be omitted.

The moisture content of lithium hydroxide monohydrate is preferably 42% by mass or more and 48% by mass or less. Moreover, it is preferable that the total carbon content of lithium hydroxide monohydrate is 1.0% or less. In this embodiment, by forming a molded body, the reaction between the nickel composite oxide and lithium hydroxide monohydrate can proceed efficiently. In addition, lithium hydroxide monohydrate may react with carbon dioxide in the air to form lithium carbonate, but if the total carbon is within the above range, the positive electrode active material has a reduced amount of impurities. substance can be obtained.

The molded article according to this embodiment does not contain a binder, as described above. As described above, by including lithium hydroxide monohydrate as a raw material, the molded object can have sufficient strength even without a binder. Moreover, when the molded body does not contain a binder, a positive electrode active material with a reduced amount of impurities can be obtained.

Further, in the molded article according to the present embodiment, the maximum distance between two points on the outer shape is 1 mm or more, and the density is 1.3 g/cm ³ or more. The shape and preferable range of density of the molded body are the same as those of the molded body in the above-described method for producing a positive electrode active material, and therefore description thereof will be omitted.

3. Non-Aqueous Electrolyte Secondary Battery The method for manufacturing a non-aqueous electrolyte secondary battery according to this embodiment (hereinafter also referred to as "method for manufacturing a secondary battery") uses a positive electrode, a negative electrode, and a non-aqueous electrolyte to produce a non-aqueous electrolyte secondary battery. obtaining an electrolyte secondary battery, and the positive electrode is obtained using the positive electrode active material obtained by the above-mentioned manufacturing method. Note that the secondary battery obtained by the manufacturing method according to the present embodiment may include, for example, a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, or may include a positive electrode, a negative electrode, and a solid electrolyte. Further, the secondary battery may be constructed from the same components as known lithium ion secondary batteries.

Hereinafter, as an example of the method for manufacturing a secondary battery according to the present embodiment, each constituent material of a secondary battery using a non-aqueous electrolyte and a method for manufacturing the same will be described. Note that the embodiments described below are merely examples, and the method for manufacturing a secondary battery may be modified and improved based on the embodiments described in this specification based on the knowledge of those skilled in the art. It can be implemented in the following form. Further, the use of the secondary battery obtained by the manufacturing method according to the present embodiment is not particularly limited.

(positive electrode)
The positive electrode includes the positive electrode active material described above. The positive electrode can be manufactured, for example, as follows. Note that the method for producing the positive electrode is not limited to the following example, and other methods may be used.

First, the above cathode active material, conductive material, and binder are mixed, and if necessary, activated carbon and a solvent for viscosity adjustment, etc. are added, and the mixture is kneaded to form a cathode composite. Make a paste. Note that the constituent material of the positive electrode composite paste is not particularly limited, and materials equivalent to known positive electrode composite pastes may be used.

The mixing ratio of each material in the positive electrode composite paste is not particularly limited, and is adjusted as appropriate depending on the required performance of the secondary battery. The mixing ratio of the materials can be in the same range as the positive electrode composite paste of known secondary batteries. For example, if the total mass of the solid content of the positive electrode composite excluding the solvent is 100 parts by mass, the positive electrode The content of the active material may be 60 parts by mass or more and 95 parts by mass or less, the content of the conductive material may be 1 part by mass or more and 20 parts by mass or less, and the content of the binder may be 1 part by mass or more and 20 parts by mass or less.

As the conductive agent, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black-based materials such as acetylene black, Ketjen black, etc. can be used.

The binder plays a role in binding the active material particles, and includes, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, and cellulose resin. , polyacrylic acid, etc. can be used.

Note that, if necessary, a solvent for dispersing the positive electrode active material, conductive material, and activated carbon and dissolving the binder may be added to the positive electrode composite paste. Specifically, an organic solvent such as N-methyl-2-pyrrolidone (NMP) may be used as the solvent. Furthermore, activated carbon may be added to the positive electrode mixture in order to increase the electric double layer capacity.

Next, the obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, aluminum foil, dried, and the solvent is scattered to produce a sheet-like positive electrode. If necessary, pressure may be applied using a roll press or the like in order to increase the electrode density. The sheet-like positive electrode can be cut into an appropriate size depending on the intended battery and used for battery production.

(Negative electrode)
Metal lithium, lithium alloy, or the like may be used for the negative electrode. In addition, for the negative electrode, a negative electrode active material that can absorb and deintercalate lithium ions is mixed with a binder, and an appropriate solvent is added to make a paste. It may be applied to the surface, dried, and compressed to increase the electrode density if necessary.

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

(Separator)
A separator is placed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and holds the electrolyte, and can be a thin film made of polyethylene, polypropylene, etc., and has many minute pores.

(Non-aqueous electrolyte)
The non-aqueous electrolyte is a solution in which a lithium salt as a supporting salt is dissolved in an organic solvent. Examples of organic solvents 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 also tetrahydrofuran, 2- One type selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butane sultone, and phosphorus compounds such as triethyl phosphate and trioctyl phosphate is used alone or in a mixture of two or more types. be able to.

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

(Battery shape and configuration)
The non-aqueous electrolyte secondary battery of this embodiment, which is composed of the positive electrode, negative electrode, and non-aqueous electrolyte described above, can have various shapes, such as a cylindrical shape and a stacked type. Regardless of the shape, the positive electrode and negative electrode are laminated with a separator in between to form an electrode body, the resulting electrode body is impregnated with a non-aqueous electrolyte, and communicated with the positive electrode current collector to the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collection lead, etc., and seal it in the battery case to complete the non-aqueous electrolyte secondary battery. . Note that when a solid electrolyte is employed, the solid electrolyte may also serve as a separator.

Hereinafter, the present invention will be specifically explained using examples, but the present invention is not limited to these examples in any way. Regarding the positive electrode active material obtained in this embodiment, the positive electrode composite paste using this positive electrode active material, and the non-aqueous electrolyte secondary battery, its performance (paste stability, initial discharge capacity, positive electrode resistance, discharge capacity retention rate) ) was measured. In this example, each sample of reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. was used for the production of the composite hydroxide, the positive electrode active material, and the secondary battery.

[Manufacture and evaluation of secondary batteries for evaluation]
A 2032-type coin-type battery CBA (see FIG. 6) was produced by the following method, and the battery characteristics of the positive electrode active material were evaluated.

(Production of coin-type battery)
A positive electrode PE (evaluation electrode) was prepared by mixing 52.5 mg of positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) and press-molding the mixture to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. did. The produced positive electrode PE was dried in a vacuum dryer at 120° C. for 12 hours. Using the dried positive electrode PE, negative electrode NE, separator SE, and electrolyte, a coin-type battery CBA shown in FIG. 6 was fabricated in a glove box with an Ar atmosphere whose dew point was controlled at −80° C.

For the negative electrode NE, we used a negative electrode sheet in which copper foil was coated with graphite powder with an average particle size of about 20 μm and polyvinylidene fluoride punched into a disk shape of 14 mm in diameter, and 1M LiPF ₆ was used as the electrolyte. A mixed solution of equal amounts of ethylene carbonate (EC) and diethyl carbonate (DEC) (manufactured by Toyama Pharmaceutical Co., Ltd.) was used. A porous polyethylene film with a film thickness of 25 μm was used as the separator SE. Further, the coin-shaped battery CBA had a gasket GA and a wave washer WW, and was assembled into a coin-shaped battery with a positive electrode can PC and a negative electrode can NC.

(Initial discharge capacity)
The initial discharge capacity is calculated by setting the current density to the positive electrode at 0.1 mA/cm ² and setting the cutoff voltage at 4 after leaving the coin-type battery CBA for about 24 hours and stabilizing the open circuit voltage OCV (Open Circuit Voltage). The initial discharge capacity was defined as the capacity when the battery was charged to .3V, and then discharged to a cutoff voltage of 3.0V after a 1-hour rest.

[Elution lithium titration]
After dispersing 15 g of the obtained lithium-nickel composite oxide (positive electrode active material) in 75 ml of pure water, it was allowed to stand for 10 minutes, and 10 ml of the supernatant liquid was diluted with 50 ml of pure water to determine the amount of lithium eluted in the water. (Amount of eluted lithium) was measured by neutralization titration method by adding 1 mol/liter of hydrochloric acid.

(Example 1)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a moisture content including hydration water of 43.2%. Lithium hydroxide having a total carbon content of 1.0% or less was mixed so that the Li/Me ratio was 1.03 to prepare a lithium mixture. 290 g of the prepared lithium mixture powder was placed in a 100 mm x 100 mm mold and pressurized with a molding surface pressure of 290 kg/cm ² using a hydraulic press to form a molded product with a thickness of 20 mm (maximum distance between two points on the outside: 143 mm). ) was produced, and its density was 1.45 g/cm ³ . The temperature of the produced molded body was rapidly raised from room temperature to 760°C in a 90% oxygen atmosphere, and the rate of temperature increase at the center of the molded body at that time was measured, and it was 5.68°C/min.

(Example 2)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a moisture content including hydration water of 43.2%. Lithium hydroxide having a total carbon content of 1.0% or less was mixed so that the Li/Me ratio was 1.03 to prepare a lithium mixture. 9135 g of the prepared lithium mixture powder was placed in a 300 mm x 300 mm mold and pressed with a molding surface pressure of 300 kg/cm ² using a hydraulic press to form a molded product with a thickness of 70 mm (maximum distance between two points on the outside: 430 mm). ) was produced, and its density was 1.45 g/cm ³ . The temperature of the produced molded body was rapidly raised from room temperature to 760°C in a 90% oxygen atmosphere, and the rate of temperature increase at the center of the molded body at that time was measured, and it was found to be 4.21°C/min.

(Example 3)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a moisture content including hydration water of 43.2%. Lithium hydroxide having a total carbon content of 1.0% or less was mixed so that the Li/Me ratio was 1.03 to prepare a lithium mixture. 13,705 g of the prepared lithium mixture powder was placed in a 300 mm x 300 mm mold and pressed with a molding surface pressure of 300 kg/ ^cm2 using a hydraulic press to form a molded product with a thickness of 105 mm (maximum distance between two points on the outside: 437 mm). ) was produced, and its density was 1.45 g/cm ³ . The temperature of the produced molded body was rapidly raised from room temperature to 760°C in a 90% oxygen atmosphere, and the rate of temperature increase at the center of the molded body at that time was measured, and it was found to be 3.68°C/min.

(Comparative example 1)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a moisture content including hydration water of 43.2%. Lithium hydroxide having a total carbon content of 1.0% or less was mixed so that the Li/Me ratio was 1.03 to prepare a lithium mixture. 200 g of the prepared lithium mixture powder was placed in a 100 mm x 100 mm sagger (height of approximately 20 mm), and the temperature was rapidly raised from room temperature to 760 ° C. in a 90% oxygen atmosphere, and the temperature increase rate at the center of the compact was measured. As a result, the temperature was 4.62°C/min.

(Comparative example 2)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a moisture content including hydration water of 43.2%. Lithium hydroxide having a total carbon content of 1.0% or less was mixed so that the Li/Me ratio was 1.03 to prepare a lithium mixture. 9450 g of the prepared lithium mixed powder was placed in a 300 mm x 300 mm sagger (height of approximately 105 mm), and the temperature was rapidly raised from room temperature to 760°C in a 90% oxygen atmosphere. When measured, it was 2.22°C/min.

(Evaluation result 1)
Table 1 is a table showing the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 2. From the results of Examples 1 to 3 and Comparative Examples 1 to 2, heat conductivity is improved by forming the powder of the lithium mixture into a compact. It was found that the temperature rise rate of the molded body was faster despite its larger weight.

(Example 4)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 8255 g, the molding surface pressure was 200 kg/cm ² , and the temperature increase rate of the furnace was 4.50 ° C / min. Firing was performed. The thickness of the lithium mixture molded body was 70 mm, and the density was 1.31 g/cm ³ . Further, the temperature increase rate at the center of the molded body was 4.23°C/min. However, about 20% of the fabricated pieces broke during handling after molding.

(Example 5)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 10140 g, the molding surface pressure was 500 kg/cm ² , and the temperature increase rate of the furnace was 4.50° C./min. Firing was performed. The thickness of the lithium mixture molded body was 70 mm, and the density was 1.61 g/cm ³ . Further, the temperature increase rate at the center of the molded body was 4.23°C/min. There were no cracks during handling after molding.

(Example 6)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 10,900 g, the molding surface pressure was 750 kg/cm ² , and the temperature increase rate of the furnace was 4.50 ° C./min. Firing was performed. The thickness of the lithium mixture molded body was 70 mm, and the density was 1.73 g/cm ³ . Further, the temperature increase rate at the center of the molded body was 4.19°C/min. There were no cracks during handling after molding.

(Example 7)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 11,530 g, the molding surface pressure was 1,000 kg/cm ² , and the temperature increase rate of the furnace was 4.50 ° C./min. Firing was performed. The thickness of the lithium mixture molded body was 70 mm, and the density was 1.83 g/cm ³ . Further, the temperature increase rate at the center of the molded body was 4.22°C/min. There were no cracks during handling after molding.

(Example 8)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 12,050 g, the molding surface pressure was 1,500 kg/cm ² , and the temperature increase rate of the furnace was 4.50 ° C./min. Firing was performed. The thickness of the lithium mixture molded body was 70 mm, and the density was 1.91 g/cm ³ . Moreover, the temperature increase rate at the center of the molded body was 4.20° C./min. There were no cracks during handling after molding.

(Comparative example 3)
A lithium mixture molded body was produced in the same manner as in Example 2, except that the amount of lithium mixture powder was 7980 g, the molding surface pressure was 100 kg/cm ² , and the temperature increase rate of the furnace was 4.50°C/min. , it almost did not harden and could not be molded.

(Comparative Example 10)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=88:9:3 in a rotary kiln and a nickel composite oxide with a moisture content of 1.5% or less and a total carbon of 1.5% or less. A lithium mixture was prepared by mixing 0% or less lithium hydroxide (anhydrous lithium hydroxide) such that the Li/Me ratio was 1.03. 9450 g of the prepared lithium mixed powder was placed in a 300 mm x 300 mm sagger (height of approximately 105 mm), and the temperature was rapidly raised from room temperature to 760°C in a 90% oxygen atmosphere. When measured, it was 2.60°C/min.

Table 2 is a table showing the evaluation results of Examples 2, 4 to 8, and Comparative Examples 2, 3, and 10. Further, FIG. 7 is a graph showing the relationship between density and temperature increase rate for these Examples, Comparative Example 2, and Comparative Example 10. From the results of Comparative Example 3, in the case of a molded article containing nickel composite oxide and lithium hydroxide monohydrate having the above composition ratio and no binder, the density must be 1.3 g/cm ³ or more. It was shown that the molded product did not form.

Furthermore, from the results of Comparative Examples 2 and 10, when firing a lithium mixture powder, the lithium mixture of Comparative Example 10 using anhydrous lithium hydroxide (moisture content of 1% or less) is better than lithium hydroxide monohydrate. It was shown that the temperature increase rate was higher than that of the lithium mixture of Comparative Example 2 using lithium oxide. Furthermore, it was shown that when the powder of the lithium mixture was made into a molded body as in the example, the temperature increase rate was higher than that of the powder of the lithium mixture obtained in Comparative Examples 2 and 10. Further, the results of Examples 4 to 8 show that the heat transferability does not substantially change depending on the density of the molded body (see FIG. 7).

(Example 9)
The heating rate of the furnace was 4.50°C/min, the temperature was raised from room temperature (25°C) to 760°C, and the temperature at the center of the molded body was maintained at 760°C for 3 hours, and then the temperature was lowered. , and fired in the same manner as in Example 2. The temperature increase rate at the center of the molded body was 4.22°C/min (temperature increase time was approximately 2.9 hours). The total firing time was 5.9 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Example 10)
The temperature was raised from room temperature (25°C) to 760°C using a furnace heating rate of 4.50°C/min, and the temperature at the center of the molded body was maintained at 760°C for 2.5 hours, and then the temperature was lowered. Other than that, firing was carried out in the same manner as in Example 2. The heating rate at the center of the molded body was 4.20°C/min (the heating time was approximately 2.9 hours). The total firing time was 5.4 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Example 11)
The temperature was raised from room temperature (25°C) to 760°C using a furnace heating rate of 4.50°C/min, and the temperature at the center of the molded body was maintained at 760°C for 2.0 hours, and then the temperature was lowered. Other than that, firing was carried out in the same manner as in Example 2. The temperature increase rate at the center of the molded body was 4.23°C/min (temperature increase time was approximately 2.9 hours). The total firing time was 4.9 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Example 12)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=91:4.5:4.5 in a rotary kiln and a moisture content including hydration water of 43 Same as Example 9, except that lithium hydroxide with a total carbon content of .2% and 1.0% or less was mixed so that the Li/Me ratio was 1.02, and the firing temperature was set at 745°C. It was then baked. The temperature increase rate at the center of the molded body was 4.22°C/min (temperature increase time was approximately 2.8 hours). The total firing time was 5.8 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Example 13)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=91:4.5:4.5 in a rotary kiln and a moisture content including hydration water of 43 Same as Example 10, except that lithium hydroxide with a total carbon content of .2% and 1.0% or less was mixed so that the Li/Me ratio was 1.02, and the firing temperature was set at 745°C. It was then baked. The temperature increase rate at the center of the molded body was 4.23°C/min (temperature increase time was approximately 2.8 hours). The total firing time was 5.3 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 3. Table 3 also shows the results of battery characteristic evaluation for coin-type batteries.

(Example 14)
A nickel composite oxide obtained by oxidizing and roasting a nickel composite hydroxide with a composition ratio of Ni:Co:Al=91:4.5:4.5 in a rotary kiln and a moisture content including hydration water of 43 Same as Example 11, except that lithium hydroxide with a total carbon content of .2% and 1.0% or less was mixed so that the Li/Me ratio was 1.02, and the firing temperature was set at 745°C. It was then baked. The temperature increase rate at the center of the molded body was 4.23°C/min (temperature increase time was about 2.8 hours). The total firing time was 4.8 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 3. Table 3 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative example 4)
The temperature was raised from room temperature (25°C) to 760°C using a furnace heating rate of 4.50°C/min, and the temperature at the center of the molded body was maintained at 760°C for 1.5 hours, then the temperature was lowered. Other than that, firing was carried out in the same manner as in Example 9. The temperature increase rate at the center of the molded body was 4.22°C/min (temperature increase time was about 2.9 hours). The total firing time was 4.4 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 3. Table 3 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative example 5)
The temperature was raised from room temperature (25°C) to 745°C using a furnace heating rate of 4.50°C/min, and the temperature at the center of the molded body was maintained at 745°C for 1.5 hours, and then the temperature was lowered. Other than that, firing was carried out in the same manner as in Example 12. The temperature increase rate at the center of the molded body was 4.23°C/min (temperature increase time was about 2.8 hours). The total firing time was 4.3 hours. After firing, the compact was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 3. Table 3 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative example 6)
9450 g of lithium mixture powder was placed in a 300 mm x 300 mm sagger (height of approximately 105 mm), and the temperature was raised from room temperature (25 °C) to 760 °C at a heating rate of 4.50 °C/min. After maintaining the temperature at the center of 760° C. for 3 hours, baking was performed in the same manner as in Example 9, except that the temperature was lowered. The heating rate at the center of the lithium mixture powder was 2.23°C/min (heating time was approximately 5.5 hours). The total firing time was 8.5 hours. After firing, the obtained lithium-nickel composite oxide powder was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 3. Table 3 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative Example 7)
Firing was performed in the same manner as in Comparative Example 6, except that the holding time at 760°C was 2.5 hours. The heating rate at the center of the lithium mixture powder was 2.20°C/min. The total firing time was 8.1 hours. After firing, the obtained lithium-nickel composite oxide powder was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative example 8)
9450 g of lithium mixture powder was placed in a 300 mm x 300 mm sagger (height of the mound was approximately 105 mm), and the temperature was raised from room temperature (25 °C) to 745 °C at a heating rate of 4.50 °C/min. After maintaining the temperature at the center of the powder mixture at 745° C. for 3 hours, it was fired in the same manner as in Example 12, except that the temperature was lowered. The heating rate at the center of the lithium mixture powder was 2.22°C/min (heating time was about 5.4 hours). The total firing time was 8.4 hours. After firing, the obtained lithium-nickel composite oxide powder was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Comparative example 9)
Firing was performed in the same manner as Comparative Example 8 except that the holding time at 745°C was 2.5 hours. The heating rate at the center of the lithium mixture powder was 2.23°C/min (heating time was approximately 5.4 hours). The total firing time was 7.9 hours. After firing, the obtained lithium-nickel composite oxide powder was pulverized, washed with water, filtered, and dried, and the crystallite diameter and Li site occupancy of the dried powder were measured using X-ray diffraction. The results are shown in Table 1. Table 1 also shows the results of battery characteristic evaluation for coin-type batteries.

(Evaluation result 3)
The lithium-nickel composite oxide obtained in the example has a sufficiently large crystallite diameter, a high lithium seat occupancy rate, and a reduced amount of eluted lithium, and the sintering reaction progresses satisfactorily. It was shown to have high crystallinity. Further, it was shown that the secondary battery using the lithium nickel composite oxide obtained in the example as the positive electrode active material had very high initial charge/discharge capacity and initial discharge efficiency. From the above, according to the manufacturing method of the present embodiment, by forming a lithium mixture into a high-density compact, the amount of raw materials input per unit volume increases, and the short firing time allows lithium with high crystallinity to be produced. It is clear that a nickel composite oxide (positive electrode active material) can be obtained and productivity is greatly improved.

Note that the technical scope of the present invention is not limited to the aspects described in the above-mentioned embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. Furthermore, the requirements described in the above embodiments and the like can be combined as appropriate. In addition, to the extent permitted by law, the disclosures of all documents cited in the above-mentioned embodiments are incorporated into the description of the main text.

1... Plate member 2... Container 10... Molded body 20... Lithium mixture powder t... Thickness of molded body CBA... Coin type battery NC... Negative electrode can NE... Negative electrode PC... Positive electrode can PE... Positive electrode SE... Separator GA... Gasket WW…Wave washer

Claims (12)

A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery containing a lithium-nickel composite oxide, the method comprising:
Mixing a nickel composite oxide and lithium hydroxide monohydrate to obtain a lithium mixture;
Molding the lithium mixture to obtain a molded body having a density of 1.3 g/cm ³ or more and 2.0 g/cm ³ or less;
firing the molded body at 650°C or more and 850°C or less in an oxidizing atmosphere,
The molded body does not contain a binder,
The lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), and aluminum (Al), and the atomic ratio of each element is Li:Ni:Co:Al=s :(1-x-y):x:y (however, 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y≦0.10),
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the lithium hydroxide monohydrate has a moisture content of 42% by mass or more and 48% by mass or less. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the molded body has a density of 1.4 g/cm ³ or more. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the maximum distance between two points on the outer shape of the molded body is 1 mm or more. The calcination is performed by placing the molded body on a plate-like member placed in a calcination furnace. Production method. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, comprising crushing the fired product after the firing. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, comprising washing the fired product after the firing with water and drying it. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein in the firing, the firing temperature is maintained for 3 hours or less. The lithium-nickel composite oxide contains lithium (Li), nickel (Ni), cobalt (Co), aluminum (Al), and other elements M, and the atomic ratio of each element is Li:Ni. :Co:Al:M=s:(1-x-y):x:y:z (however, 0.93<s<1.03, 0.03≦x≦0.10, 0.03≦y ≦0.10, 0<z≦0.1, M is an element other than Li, Ni, Co, Al and O), A method for producing a positive electrode active material for an aqueous electrolyte secondary battery. A claim in which 5 g of the lithium-nickel composite oxide is dispersed in 100 ml of pure water, and the amount of lithium eluted into the supernatant liquid after standing for 10 minutes is 0.11% by mass or less based on the total amount of the lithium-nickel composite oxide. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 9. The lithium-nickel composite oxide according to any one of claims 1 to 10, wherein the lithium site occupancy rate of the 3a site obtained from Rietveld analysis of the X-ray diffraction pattern is 97.0% or more. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. Contains nickel (Ni), cobalt (Co), and aluminum (Al), and the molar ratio of each element is Ni:Co:Al=(1-xy):x:y (0.03≦x ≦0.10, 0.03≦y≦0.10);
Lithium hydroxide monohydrate;
A molded article that does not contain a binder, has a maximum distance between two points on the outer shape of 1 mm or more, and a density of 1.3 g/cm ³ or more and 2.0 g/cm ³ or less.

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