JP7134590B2 - Method for producing crack-free lithium-ion battery positive electrode active material precursor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing crack-free, relatively large spherical or near-spherical composite metal hydroxide particles useful as a positive electrode active material precursor for lithium ion batteries.

Lithium-ion batteries have a long history, and their commercial production began in the 1990s. However, it can be said that the development of lithium-ion batteries has progressed in earnest with the spread of mobile terminals, smart phones, electric vehicles, and the like since 2000. Lithium-ion batteries, like other batteries, are made up mainly of a positive electrode, a negative electrode, an electrolyte, and an outer casing. be. As positive electrode active materials used in lithium-ion batteries, lithium cobaltate, ternary composite oxides, nickel-based composite oxides, spinel-type composite oxides, olivine-type compounds and the like are known. Ternary composite oxides and nickel-based composite oxides are known as composite oxides having a layered crystal structure and having a large discharge capacity.

In general, a positive electrode active material composed of a layered composite metal oxide is produced by powder-mixing a precursor composite metal hydroxide and a lithium compound and firing the mixture in an oxidizing atmosphere. In the baking step, the shape of the particles of the composite metal hydroxide, which is the precursor, is substantially maintained. Therefore, when a precursor having a spherical particle shape is used in the production of a positive electrode active material, a positive electrode active material having the same spherical particle shape can be obtained. In general, when filling and compressing powder, the more spherical the particles that make up the powder are, and the less cracks there are in individual particles, the more evenly distributed the particles will be, and The applied load is uniform and there is little further cracking or deformation of the particles due to filling. Therefore, even when the positive electrode active material particles are filled on the electrode, if the positive electrode active material particles have a spherical shape without cracks, a uniform positive electrode active material particle layer without defects can be formed on the electrode. can. An electrode on which such a uniform and defect-free positive electrode active material particle layer is formed is preferable for the charge/discharge characteristics of the battery. Therefore, a technology for controlling the shape of the precursor particles of the positive electrode active material into a spherical shape without cracks is required for improving the performance of the lithium ion battery. A precursor composed of spherical composite metal hydroxide particles with a larger particle size and no cracks is particularly preferred for forming a higher density positive electrode active material layer on an electrode.

A composite metal hydroxide as a precursor is generally produced by a coprecipitation method in which an alkaline aqueous solution and a complexing agent are added to an aqueous solution of a soluble metal salt. In the coprecipitation reaction, the particles of the composite metal hydroxide in the reaction slurry collide with each other due to stirring and gradually approach a spherical shape. However, when the particles of the composite metal hydroxide become large, there is a problem that the particles break when they collide with each other, so that the desired particle size cannot be achieved. Despite the importance of the technology for producing large-sized, crack-free, spherical or near-spherical precursor particles, it has not been studied in detail so far.

For example, Patent Literature 1 discloses a positive electrode active material having a spherical particle shape and uniformly uneven surfaces. Although it is mentioned here that the particle shape is spherical, there is no description of how to prevent cracking during preparation of the precursor. For example, in Patent Document 2, the particle shape is hexagonal columnar, and 0.5 ≤ (2c) / (a + b) ≤ 1 (where a is the average major axis diameter of the bottom surface, b is the average minor axis diameter of the bottom surface , c represents the average particle height). However, there is no mention here either of the preparation of the precursor.

By the way, a nickel-based positive electrode active material is generally produced by firing a mixture of a nickel-cobalt composite metal hydroxide as a precursor, a compound containing a trace element such as aluminum, and a lithium compound, which are used as necessary. can get. It is known that properties such as the particle size distribution of the precursor used for sintering are greatly involved in the performance of the nickel-based positive electrode active material. Accordingly, various methods have been proposed for producing a nickel-cobalt composite metal hydroxide that is effective as a precursor of a better positive electrode active material. For example, Patent Literature 3 describes the production of a nickel-cobalt composite metal hydroxide having spherical and regular particle shapes using a reactor having an inclined plate sedimentation device. The production method disclosed in Patent Document 3 is a highly versatile means for producing a composite metal hydroxide containing nickel and cobalt. However, in the production method described in Patent Document 3, the precursor of the positive electrode active material (NCA-based positive electrode active material) containing lithium, nickel, cobalt, and aluminum, which has attracted particular attention in recent years, that is, nickel and cobalt and optionally aluminum It did not focus on the production of composite metal hydroxides containing.

Thus, from a composite metal hydroxide containing nickel, cobalt, and optionally aluminum, which is useful as a positive electrode active material for a lithium ion battery, particularly as a precursor of an NCA-based positive electrode active material, having a large particle size and a crack-free spherical shape, There is still room for improvement in the method for producing such particles.

JP-A-6-333562 JP 2003-151546 A Japanese Patent No. 5227306

The present invention is directed to the production of particles of composite metal hydroxides containing nickel, cobalt and optionally aluminum, which are suitable as precursors for positive electrode active materials in lithium ion batteries. In the present invention, by improving the method for producing the above composite metal hydroxide, it is expected to be a raw material for a high-quality positive electrode active material with a large particle size and a crack-free spherical or near-spherical shape, which has not been obtained so far. We succeeded in obtaining positive electrode active material precursor particles.

The present inventors have found that, in a method for producing a composite metal hydroxide containing nickel, cobalt and optionally aluminum using a coprecipitation reaction, by controlling the temperature of the precipitation zone and the stirring power applied to the precipitation zone, the object The present inventors have found that it is possible to produce spherical or near-spherical composite metal hydroxide particles having a large particle size and no cracks. That is, the present invention is as follows.

(Invention 1) By mixing the starting materials in a reactor, precipitating the compound in the reaction zone in the reactor, filtering and drying the precipitated product, a compound of the formula: _{NiaCobAlc (} OH _{)d (} a = 0.70 to 0.95, b = 0.02 to 0.20, c = 0 to 0.1, d = 2.0 to 2.1, a + b + c = 1) average grain having the composition shown A method for producing particles composed of a composite metal hydroxide having a diameter of 10.0 μm or more, wherein the liquid temperature in the reaction zone is 60° C. or higher, and the stirring power applied to the reaction zone is 2.2 kw/m ³ . The following method for producing a composite metal hydroxide.
(Invention 2) The composite metal hydroxide of Invention 1, wherein the composite metal hydroxide particles are spherical or near-spherical, and cracks on the surface of the composite metal hydroxide particles are not observed in a scanning electron micrograph magnified 1000 times. A method of making things.
(Invention 3) The following device:
Apparatus for producing a compound by precipitation in a reactor, said reactor comprising a tilted plate settler for intimately mixing a starting material solution as it is introduced into the reaction zone of said reactor. an adapted apparatus, wherein said inclined plate settler is integrated with said reactor so as to be directly connected to said reaction zone and is connected via at least one pump to at least one circulation vessel; aspirating turbid liquid from the product suspension in the reactor to the at least one circulation vessel and removing the liquid from the circulation vessel after removing solid particulate fractions from the turbid liquid through a filter element; , and by direct recycling to the reactor, the particle size distribution of the product suspension in said reactor is shifted to higher D50 values. Equipment for:
The method for producing a composite metal hydroxide according to Invention 1 or 2, wherein
(Invention 4) A step of producing a precursor of a positive electrode active material for a lithium ion battery by the method for producing a composite metal hydroxide according to any one of Inventions 1 to 3, and firing a mixture containing the precursor and at least a lithium compound. A method for producing a lithium ion battery positive electrode active material, comprising:

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a spherical or near-spherical composite metal hydroxide having a large particle size and no cracks, which is highly useful as a positive electrode active material for lithium ion batteries, particularly as a precursor of an NCA-based positive electrode active material.

1 schematically represents an example of an inclined plate sedimentation apparatus that can be used in the manufacturing method of the present invention. 1 schematically represents an example of an inclined plate sedimentation apparatus that can be used in the manufacturing method of the present invention. Schematic diagram for understanding the function of an inclined plate sedimentation device that can be used in the manufacturing method of the present invention. 1 schematically represents a reactor and its ancillary equipment that can be used in the production method of the present invention. 1 is a scanning electron micrograph of composite metal hydroxide particles obtained in Example 1. FIG. 2 is a scanning electron micrograph of composite metal hydroxide particles obtained in Example 2. FIG. 4 is a scanning electron micrograph of composite metal hydroxide particles obtained in Example 3. FIG. 1 is a scanning electron micrograph of composite metal hydroxide particles obtained in Comparative Example 1. FIG. 4 is a scanning electron micrograph of composite metal hydroxide particles obtained in Comparative Example 2. FIG. 4 is a scanning electron micrograph of composite metal hydroxide particles obtained in Comparative Example 3. FIG.

The method of the invention is detailed below.
(starting material)
Starting materials in the production method of the invention are a nickel-containing water-soluble compound, a cobalt-containing water-soluble compound, and optionally an aluminum-containing water-soluble compound. Nickel sulfate is preferred as the nickel-containing water-soluble compound. Cobalt sulfate is preferred as the cobalt-containing water-soluble compound. Sodium aluminate is preferred as the aluminum-containing water-soluble compound. Commercially available products can be used without limitation as these preferred water-soluble compounds. The case where nickel sulfate, cobalt sulfate, and sodium aluminate are used as starting materials will be described below. Even when the starting material is a water-soluble compound other than the above compounds, equivalent composite metal hydroxide particles can be produced by appropriately changing the conditions described below.

Each starting material is prepared as an aqueous solution. That is, an aqueous solution of nickel sulfate having a concentration of generally 15% by weight or more and 30% by weight or less, preferably 20% by weight or more and 25% by weight or less is prepared. An aqueous solution of cobalt sulfate having a concentration of generally 15% by weight or more and 25% by weight or less, preferably 18% by weight or more and 23% by weight or less is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are charged into separate containers outside the reactor.

When producing a precursor containing nickel, cobalt, and aluminum corresponding to at least part of the aluminum atoms constituting the NCA-based positive electrode active material, an aqueous sodium aluminate solution is included in the starting material. In this case, the NCA-based positive electrode active material is produced by firing a mixture of a precursor which is a composite metal hydroxide containing nickel, cobalt, and aluminum, a lithium compound, and, if necessary, an additional aluminum-containing compound. can get. When producing nickel and cobalt containing precursors without aluminum atoms, the starting materials do not include sodium aluminate. In this case, the NCA-based positive electrode active material is obtained by firing a mixture of a precursor, which is a composite metal hydroxide containing nickel and cobalt, a lithium compound, and an aluminum compound. In the present invention, sodium aluminate dissolved in an aqueous sodium hydroxide solution, that is, as an alkaline aqueous solution of sodium aluminate, is charged into a container different from the container for the aqueous nickel sulfate solution or the aqueous cobalt sulfate solution outside the reactor.

In order to control the precipitation reaction in the reaction zone, the method of the present invention prepares a precipitant, ie, an aqueous sodium hydroxide solution, a complexing agent, ie, ammonia water, and pure water as auxiliary starting materials. The concentrations of the aqueous sodium hydroxide solution and aqueous ammonia solution are appropriately adjusted according to the capacity of the reaction zone and the pH to be set. These auxiliary starting materials are charged into containers separate from the containers of the above various aqueous solutions outside the reactor.

(mixture)
In the process of the present invention, the starting materials are mixed in a reactor having stirring means to form a starting material reaction zone. Connected to such a reactor is a container of the starting materials described above. The above starting materials are continuously or intermittently fed to the reactor, and the coprecipitation reaction starts and progresses in the reaction zone.

The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed in advance outside the reactor and then fed into the reactor. The aqueous alkali solution of sodium aluminate is fed to the reactor in a different flow path than the mixture of nickel sulfate and cobalt sulfate solution.

The starting materials are in concentrations or volumes depending on the elemental composition of the desired composite metal hydroxide, i.e. the elements nickel and cobalt and optionally aluminum contained in the starting materials in the reaction zone with the desired composition: Ni _a Co _b Al _c (OH) _d (a=0.70-0.95, b=0.02-0.20, c=0-0.1, d=2.0-2.1, a+b+c = 1) are mixed inside the reactor in a quantity ratio to produce a composite metal hydroxide.

As the reactor having stirring means used in the present invention, known reactors can be used without limitation. The shape and material of the reactor body are not particularly limited, and a tank-shaped stainless steel container is preferably used. As the stirring means, various shapes such as propellers, paddles, inclined paddles, turbines, cones, screws and ribbons are used. The supply line of the starting materials to the reactor consists of ordinary pipes, pumps and flow sensors, and the amount of supply is controlled. These feed lines generally connect to the top of the reactor.

(reaction zone)
In the present invention, nickel hydroxide, cobalt hydroxide, and aluminum hydroxide are coprecipitated in the reaction zone within the reactor to form a composition: Ni _a Co _b Al _c (OH) _d (a=0.7 to 0.95, b = 0.02 to 0.2, c = 0.0 to 0.1, d = 2 to 2.1, a + b + c = 1) fine particles dispersed in the aqueous solution of the reaction zone Generate as When such a composite metal hydroxide is used as a precursor of an NCA-based positive electrode active material, the size and shape of the composite metal hydroxide particles produced in the reaction zone are similar to those of the NCA-based positive electrode active material. Therefore, the present invention provides means for optimizing the size and shape of the composite metal hydroxide particles produced in the reaction zone.

In the production process of the present invention, the pH of the reaction zone is controlled within a suitable range for coprecipitation, generally 7-14, preferably 9-12. The liquid temperature in the reaction zone is controlled at 60°C or higher, preferably 65°C or higher and 85°C or lower. Cracking occurs in the particles when the reaction is carried out at temperatures below 60°C. If the liquid temperature in the reaction zone is too high, ammonia volatilizes from the system and hinders particle growth, which is not preferable.

The stirring power applied to the reaction zone is controlled to 2.2 kW /m ³ or less, preferably 0.5 kW /m ³ or more and 2.0 kW /m ³ or less. If the stirring power is too small, the shape of the composite metal hydroxide particles will be distorted, making it impossible to obtain the desired spherical or near-spherical composite oxide particles. If the stirring power in the reaction zone exceeds 2.2 kW /m ³ , cracks will occur in the finally obtained composite metal hydroxide particles.

The reactor is provided with an outlet for a slurry consisting of an aqueous solution containing the produced composite metal hydroxide and various starting materials. The position of the outlet may be any position from the top to the bottom of the reactor. A pipe for guiding the slurry out of the reactor and a pump connected to this pipe are connected to the outlet. When the precipitation reaction in the reaction zone reaches a steady state, the composite metal hydroxide slurry is withdrawn from the reactor at a constant flow rate by a pump and transferred to the next drying step.

The reactor used in the present invention preferably contains a high solid concentration slurry (a fraction in which the composite metal hydroxide is present in the desired particle shape) and a low solid concentration slurry (a fraction in which the composite metal hydroxide is in the desired shape). A device (separation device) is connected to separate the fraction present in unfinished fines). A centrifugal separator, a filter, or the like is used as the separation mechanism. A volume of slurry is sucked from the reaction zone using a pump and suction pipe and sent to a separation mechanism. A portion of the separated low solids slurry is discharged out of the reactor, and the remaining low solids slurry and high solids slurry are returned to the reactor zone. The coprecipitation reaction further proceeds in the reaction zone containing the returned slurry to produce a composite metal hydroxide having the desired particle shape. As the slurry circulates through the reaction zone through the separation mechanism in this manner, production of the desired composite metal hydroxide proceeds. Such slurry circulation can control the concentration of the composite metal hydroxide in the reaction zone. In the present invention, if the concentration of the composite metal hydroxide in the reaction zone is controlled to 50 g/L or more, there is no problem in terms of production efficiency.

(Incline plate sedimentation device)
In the process of the present invention, it is more efficient to use the inclined plate settling apparatus disclosed in Japanese Patent No. 5227306 to suction, separate and circulate the slurry from the reaction zone. Inclined plate settlers are used in apparatus and methods for making compounds by precipitating solids from solution. With a precipitation device with a tilted plate precipitation device, the physical and chemical properties of the solid particles formed during precipitation can be adjusted very flexibly and independently of each other, resulting in a tailor-made product. is produced with a very high space-time yield.

The inclined plate sedimentation device is connected to a reactor in which composite metal hydroxides are produced, separates the slurry in the reactor, and separates the high solid concentration slurry from the low solid concentration slurry consisting of aqueous solution and fine particles. , a body reactor and clarifier system (IRKS), which allows a portion of the slurry to be returned to the reactor.

By using an IRKS with a tilted plate settler, the concentration of solids is increased because the mother liquor and particles are removed via the tilted plate settler under the formation of a product suspension consisting of product and mother liquor after precipitation of the compound. is achieved.

The reactor may be provided with an opening via which the suspension can optionally be removed by means of a pump and pumped back into the reactor. In order to obtain a homogeneous precipitation product, it is important that the starting materials are well mixed during charging into the reactor. This reactor can also be operated as a stirred reactor. The precipitation process in the IRKS, equipped with a tilt plate settler, can be adjusted in temperature depending on the product. Process temperatures in the IRKS are controlled by heating or cooling via heat exchangers as required.

IRKS are used for the separation of compounds from slurries. In the tilt plate settler the mother liquor is separated from the product suspension together with the fine fraction. This cloudy liquid, containing traces of solids, is mostly returned to the reactor and recombined with the product suspension. Removing a portion of this cloudy liquid removes the fine fraction from the product suspension and shifts the particle size distribution to higher D50 values. A further purpose of the tilt plate settling device is to provide a liquid whose slurry has been pre-cleaned and which has a low solids content, from which the clear mother liquor can be separated by simple methods such as filtration.

In order to increase the separation performance of the inclined plate settler, one or more lamellae can be attached, on which the solid particles are pushed downwards after they reach the surface of the lamellae by settling. Slide into the homogeneously mixed suspension. The lamella provided in the inclined plate sedimentation device is schematically represented in FIGS. 1 and 2. FIG.

The lamellae (2,5) are arranged in a plane parallel to the floor in the inclined plate settler (1,4). A lamella is a rectangular plate that can be made of plastic, glass, wood, metal or ceramic. The thickness of the lamellae (2,5) can be up to 10 cm depending on the material and product. Lamellar layers having a thickness of 0.5 to 5 cm, particularly preferably 0.5 to 1.5 cm, are preferably used. The lamellae (2,5) are fixedly mounted in the tilt plate settling device (1,4). These may be removable. In this case they enter the inclined plate settler (1, 4) via a rail system (6) or a groove (3) laterally mounted inside the inclined plate settler (1, 4). be done. The height of said rail system (6) may be designed to be adjustable, which gives the inclined plate settling device (1, 4) great flexibility regarding the selection of the spacing of the lamellae (2, 5). be. The tilt plate settling device can be designed cylindrically with a round cross-section or parallelepiped-shaped with a square cross-section. The angle of the inclined plate settler with respect to the horizontal is 20-85°, preferably 40-70° and particularly preferably 50-60°, so that the sliding of the particles works without blockage of the inclined plate settler. The tilt plate settler may be attached to the reactor via a flexible connection. With this embodiment, the angle can be variably adjusted during the process.

In order to better understand the mode of functioning of the IRKS with the inclined plate settling device, a detailed description is given below on the basis of FIG. The solid particles (7) settle downwards at a constant velocity in the inclined plate settler, depending on their shape and size. For example, given Stokes friction, the sedimentation velocity of a spherical particle caused by effective gravity is proportional to the square of the particle diameter. This velocity is superimposed on the upper component of the laminar flow velocity in the tilt plate settler. All solid particles whose sedimentation velocity is less than or the same as the upper component of the liquid stream cannot settle to the surface of the lamella (8) or the floor of the inclined plate settler and eventually It is discharged with the overflow of the plate settler.

If the sedimentation velocity of the particles is greater than the upward component of the liquid flow, the downward motion of the particles will occur at a constant sedimentation velocity. Whether particles are so discharged from the tilt plate settler with overflow depends on the vertical spacing of the particles and lamellae as they enter the tilt plate settler, at a constant flow rate of liquid, as well as on the tilt plate settler. Depends on length and angle of inclination. It is easy to see that there is a critical particle radius r ₀ , so all particles with r>r ₀ are perfectly retained by the inclined plate settler. Line (9) in FIG. 3 indicates the trajectory of a particle with critical radius _r0 . All particle trajectories with a larger radius have a smaller angle with respect to the horizontal plane and therefore will certainly hit the lamella or floorboard. This means that these particles are retained. By adjusting the ratio, in particular the flow rate of the liquid, in the inclined plate settler, it is possible to adjust the upper limit of the particle diameter of the fine particles which overflow the inclined plate settler.

As long as the overflow of the tilt plate settler is returned to the stirred reactor via the circulation vessel, nothing changes in the overall system. If a pump is used to remove a portion of the liquid volume which is cloudy due to the fine content of solids from the circulation vessel, a defined fraction of fine particles is discharged and can directly interfere with the particle size distribution. Particle size and particle size distribution can thereby be influenced independently of other plant parameters.

By said withdrawal of a turbid stream whose solids concentration on entry into the circulation vessel is typically 0.5-5% solids concentration in the reactor, the solids concentration of the suspension in the reactor is of course also at the same time increased, because with the intentional removal of the fines content, a disproportionate amount of mother liquor is removed from the overall system. This is usually desirable, but not desirable if the solids concentration in the reactor is to be kept at a low level and if the increase in solids concentration cannot be sufficiently counteracted by adjusting the flow of other materials. Depending on the amount and specifications, this fine fraction can subsequently be mixed again with the product suspension. Separation in the reactor-clarifier-is decisive.

In this case, it is conceivable to remove the mother liquor from the circulation vessel via filter elements and pump it back directly into the reactor in order to increase the solids concentration of the turbidity. Less mother liquor is removed when discharging the same amount of granules. Particles whose size does not exceed 30% of the D50 value of the particle size distribution are called fines. It may also be advantageous to remove the mother liquor from the system in a circulation vessel via a filter element. This makes it possible, firstly, to increase the solids content in the reactor to several times the stoichiometric solids concentration, and secondly, to increase the concentration of neutral salts and solids concentration that may occur during the precipitation reaction. can achieve a decoupling between The concentration ratio of solids to salt in the reactor varies not only by the possibility of removing the mother liquor, e.g. It can also be increased by adding and simultaneously removing an equal amount of mother liquor from the system via a filter element.

The increased flexibility of the IRKS with the inclined plate settler, as well as the achievement of additional degrees of freedom, is illustrated in more detail for the general reaction AX + BY → AY solids + BX dissolution with the example of both parameters salt concentration and solids content. be. AX and BY represent the starting material in the starting material solution and BX represents the dissolved salt in the mother liquor. AY represents the product which occurs as an insoluble solid.

IRKS with a tilt plate settler can be used for batch-wise settling. Preferably, however, the IRKS is more suitable for use in precipitation processes in continuous operation.

Inclined plate sedimentation apparatus further relates to a process for the preparation of compounds by precipitation, in which the individual process parameters, such as (concentration of starting material, solids content in suspension, salt concentration in mother liquor) are , are adjusted independently of each other during precipitation, thus providing a controlled interference with the evolution of the particle size distribution during the precipitation process, and finally tailor-made products with defined physical properties are particularly economical. produced efficiently and with very high space-time yields.

The subject of the inclined plate sedimentation apparatus is therefore a process for the preparation of compounds by precipitation which consists of the following steps:
- providing at least first and second starting material solutions;
- combining at least the first and second starting material solutions in the reactor of claim 1;
- generating a homogeneously mixed reaction zone in the reactor;
- Precipitating the compound in the reaction zone to produce a product suspension consisting of insoluble product and mother liquor;
- partial separation of the mother liquor from the precipitated product via a tilt plate settler;
- producing a precipitated product suspension in which the concentration of the precipitated product is higher than the stoichiometric concentration;
- removing the product suspension from the reactor;
• Filtering, washing and drying the precipitated product.

The starting material solution in the inclined plate settler method is conducted into the reactor using a pump system. If this is an IRKS with a tilted plate settler with a stirred reactor, the starting materials are mixed using an agitator. If the IRKS is designed in the form of a jet reactor, the mixing of the starting materials takes place by means of jets emerging from nozzles. In order to achieve even better mixing of the starting materials, air or an inert gas can additionally be passed into the reactor. To achieve uniform product quality, it is necessary that the starting materials are homogeneously mixed in the reaction zone of the reactor. Already during mixing or homogenization of the starting materials, a precipitation reaction begins in which product and mother liquor are generated. The product suspension is enriched to the desired concentration in the lower part of the reactor. In order to achieve a purposeful enrichment of the product suspension, in the inclined plate settler method the mother liquor is partially removed via the inclined plate settler. Preferably, the partial separation of the mother liquor by withdrawal of the overflow of the tilt plate settler is carried out using a pump.

Concentrations of the precipitation product suspension which can be many times the stoichiometrically possible concentration of the precipitation product are achieved according to the method with the inclined plate settler. This can be up to 20 times higher than possible stoichiometric values. To achieve particularly high product concentrations in the suspension, partial removal of large amounts of mother liquor is necessary. Even up to 95% of the mother liquor can be partially separated. The amount of mother liquor to be partially separated depends on the selected process parameters, such as the starting material concentration, the salt concentration of the mother liquor and the solids concentration of the suspension.

In the precipitation process of the present invention, such an inclined plate precipitation apparatus can be combined with a reactor as schematically shown in FIG. 4 to produce composite hydroxides.

A reactor (13) equipped with a stirrer (10) capable of controlling the number of revolutions, a heat exchanger (11), a tilt plate sedimentation device (12), and independent pipes and pumps (23) to (27). Supply paths connect. Pumps (23) to (27) continuously feed nickel sulfate aqueous solution (a solution), cobalt sulfate aqueous solution (b solution), sodium aluminate aqueous solution (c solution), sodium hydroxide aqueous solution, and ammonia water into an integrated reaction. It is conveyed into the reaction zone of the vessel-clarifier system (IRKS). The slurry produced in the reactor (13) is removed through a level control device using a pump (14). It may be advantageous to operate the circulation pump (16) to prevent the risk of sedimentation when large particles are produced.
A pump (17) can convey the slurry with a very low concentration of fines into a circulation vessel (18) equipped with a stirrer and from there back into the reactor (13). Only particles below the separation size are transported into the circulation vessel (18), depending on the volumetric flow rate of the liquid and the sizing of the tilt plate settler. Nothing changes for the reactor (13) as long as all the turbid streams withdrawn using the pump (17) are returned via the free overflow (19).

Mother liquor and/or solid particles can also be removed from the system by removing the clarified mother liquor from the circulation vessel (18) and conveying it into the second circulation vessel (20). A pump (21) takes the clarified mother liquor from the first circulation vessel (18) and conveys it into the second circulation vessel (20). By continuously analyzing the pH value of the solution in the second circulation vessel (20), the composition of the mother liquor can be controlled throughout the coprecipitation reactor.

It is also possible to remove very fine sediments contained in the clear mother liquor from the precipitation reactor by pumping (22) the clear mother liquor accumulated in the first circulation vessel (18).

(Separation and drying of composite metal hydroxide)
When the desired amount of raw material has finished reacting in the reactor, the slurry is taken out from the outlet of the reactor and filtered. A solid fraction containing the composite metal hydroxide is thus separated. Further wash the solid fraction. Washing may be carried out according to a conventional method, using an alkaline aqueous solution and pure water until the sulfate and alkaline components contained in the composite metal hydroxide are sufficiently removed. In this way, the composite metal hydroxide containing moisture is separated.

Next, the separated composite metal hydroxide containing moisture is dried. The drying method may be any of hot air drying under atmospheric pressure, infrared drying, high frequency drying, vacuum drying, and the like. Vacuum drying, which can be dried in a short time, is preferred. Dry until the water content in the composite metal hydroxide reaches about 1% by weight.

(precursor)
In this way, composite metal hydroxide particles are obtained as a precursor of a positive electrode active material for lithium ion batteries. The size of the composite metal hydroxide particles obtained by the method of the present invention is relatively large, generally having an average particle size of 10.0 μm or more, typically 12.0 μm or more and 50 μm or less.

(Positive electrode active material)
A positive electrode active material for a lithium ion battery is obtained by firing a mixture of the above precursor, lithium compound, and optionally an aluminum compound in the presence of oxygen. The firing temperature is in the range of 450°C to 950°C, preferably in the range of 600°C to 900°C. The firing time is 2 hours to 20 hours, preferably 3 hours to 15 hours. The number of firings may be one or more. Equipment used for firing is not limited as long as it can achieve such firing conditions. Tubular furnaces, muffle furnaces, rotary kilns (RK) and roller hearth kilns (RHK) are generally used. RHK or RK is preferably used. The baked mixture is preferably washed with water and dried in order to remove excess alkali components in the positive electrode active material. There are no particular restrictions on the conditions for washing with water and drying. Generally, 100 ml or more of pure water is added to 100 g of the fired product to bring the fired product into sufficient contact with water, after which the lithium metal composite oxide powder is separated and dried in an oxygen-containing air current. There is no limitation on the method of manufacturing the positive electrode using the obtained positive electrode active material. A positive electrode member can be manufactured by preparing a positive electrode active material mixture containing a positive electrode active material obtained by a conventional method, and coating and drying it on an electrode.

[Example 1]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: A nickel sulfate aqueous solution having a nickel concentration of 8.2% by weight was prepared. A cobalt sulfate aqueous solution with a cobalt concentration of 8.2% by weight was prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution were mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=84:16 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
Alkaline aqueous solution of sodium aluminate: 3.567 g of sodium aluminate was dissolved in 1000 g of an aqueous sodium hydroxide solution having a sodium hydroxide concentration of 200 g/L.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Pure water The reactor shown in Fig. 4 is filled with an aqueous solution of sodium sulfate having a concentration of 133.6 g/L, and while the aqueous solution is circulated through the inclined plate sedimentation device ^, a stirring power of 0.89 kW/ m3 is applied to the reaction zone. The stirring speed was set to 600 rpm so that The liquid temperature in the reaction zone was maintained at 65°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the alkaline aqueous solution of sodium aluminate, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the air. The composition of the resulting composite metal hydroxide was Ni _0.825 Co _0.155 Al _0.02 (OH) ₂ . The average particle size was 12.5 μm. Thus, nickel-cobalt-aluminum composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-cobalt-aluminum composite metal hydroxide were evaluated from the following viewpoints. Table 1 shows the results.

(Average Particle Size) The average particle size (D ₅₀ ) of the obtained composite metal hydroxide particles was measured using a laser scattering particle size distribution analyzer (Mastersizer LS-230 manufactured by Malvern).

(Presence or absence of particle cracks and shape) The obtained composite metal hydroxide was observed with a scanning electron microscope (manufactured by JEOL, magnified 1000 times) to determine the presence or absence of cracks and particle shape. Enlarged photographs are provided as FIGS. 5-10.

[Example 2]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: Prepare a nickel sulfate aqueous solution with a nickel concentration of 8.2% by weight. An aqueous solution of cobalt sulfate having a cobalt concentration of 8.2% by weight is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=92.5:7.5 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Sodium hydroxide aqueous solution ・Pure water The reactor shown in Fig. 4 is filled with a sodium sulfate aqueous solution having a concentration of 133.6 g / L, and the reaction zone is supplied with 2.0 kW / while circulating the aqueous solution through the inclined plate sedimentation device. The stirring rotation speed was set to 1000 rpm so as to give a stirring power of ^m3 . The liquid temperature in the reaction zone was maintained at 65°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the sodium hydroxide aqueous solution, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the atmosphere. The composition of the obtained composite metal hydroxide was Ni _0.925 Co _0.075 (OH) ₂ . The average particle size of the particles was 12.5 μm. Thus, nickel-cobalt-aluminum composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-baltic-aluminum composite metal hydroxide were evaluated from the same viewpoint as in Example 1. Table 1 shows the results.

[Example 3]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: Prepare a nickel sulfate aqueous solution with a nickel concentration of 8.2% by weight. An aqueous solution of cobalt sulfate having a cobalt concentration of 8.2% by weight is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=87.5:12.5 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Sodium hydroxide aqueous solution ・Pure water The reactor shown in Fig. 4 was filled with a sodium sulfate aqueous solution having a concentration of 133.6 g/L, and the reaction zone was supplied with 0.63 kW / while circulating the aqueous solution through the inclined plate sedimentation device. The stirring rotation speed was set to 500 rpm so as to give a stirring power of ^m3 . The liquid temperature in the reaction zone was maintained at 65°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the sodium hydroxide aqueous solution, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the atmosphere. The composition of the obtained composite metal hydroxide was Ni _0.875 Co _0.125 (OH) ₂ . The average particle size of the particles was 18.3 μm. In this way, nickel-cobalt composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-cobalt-aluminum composite metal hydroxide were evaluated from the same viewpoint as in Example 1. Table 1 shows the results.

[Comparative Example 1]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: Prepare a nickel sulfate aqueous solution with a nickel concentration of 8.2% by weight. An aqueous solution of cobalt sulfate having a cobalt concentration of 8.2% by weight is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=85:15 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Sodium hydroxide aqueous solution ・Pure water The reactor shown in Fig. 4 is filled with a sodium sulfate aqueous solution having a concentration of 133.6 g/L, and the reaction zone is supplied with 1.68 kW / while circulating the aqueous solution through the inclined plate sedimentation device. The stirring rotation speed was set to 888 rpm so as to give a stirring power of ^m3 . The liquid temperature in the reaction zone was maintained at 50°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the sodium hydroxide aqueous solution, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the atmosphere. The composition of the obtained composite metal hydroxide was Ni _0.850 Co _0.150 (OH) ₂ . The average particle size of the particles was 16.3 μm. In this way, nickel-cobalt composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-cobalt composite metal hydroxide were evaluated from the same viewpoint as in Example 1. Table 1 shows the results.

[Comparative Example 2]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: Prepare a nickel sulfate aqueous solution with a nickel concentration of 8.2% by weight. An aqueous solution of cobalt sulfate having a cobalt concentration of 8.2% by weight is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=84.2:15.8 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Sodium hydroxide aqueous solution ・Pure water The reactor shown in Fig. 4 is filled with a sodium sulfate aqueous solution with a concentration of 133.6 g / L, and the reaction zone is supplied with 1.00 kW / while circulating the aqueous solution through the inclined plate sedimentation device. The stirring rotation speed was set to 640 rpm so as to give a stirring power of ^m3 . The liquid temperature in the reaction zone was maintained at 50°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the sodium hydroxide aqueous solution, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the atmosphere. The composition of the obtained composite metal hydroxide was Ni _0.842 Co _0.158 (OH) ₂ . The average particle size of the particles was 17.0 μm. In this way, nickel-cobalt composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-cobalt composite metal hydroxide were evaluated from the same viewpoint as in Example 1. Table 1 shows the results.

[Comparative Example 3]
The starting materials shown below were used.
• Nickel sulfate aqueous solution, cobalt sulfate aqueous solution, mixture thereof: Prepare a nickel sulfate aqueous solution with a nickel concentration of 8.2% by weight. An aqueous solution of cobalt sulfate having a cobalt concentration of 8.2% by weight is prepared. The nickel sulfate aqueous solution and the cobalt sulfate aqueous solution are mixed at a ratio of nickel sulfate aqueous solution:cobalt sulfate aqueous solution=85.8:14.2 (weight ratio). This mixture was charged into a vessel that was connected to the reactor via a feed line.
- Complexing agent: Ammonia water containing ammonia at a concentration of 25% by weight.
・Sodium hydroxide aqueous solution ・Pure water The reactor shown in Fig. 4 was filled with a sodium sulfate aqueous solution having a concentration of 133.6 g/L, and the reaction zone was supplied with 2.32 kW / while circulating the aqueous solution through the inclined plate sedimentation device. The stirring rotation speed was set to 1111 rpm so as to give a stirring power of ^m3 . The liquid temperature in the reaction zone was maintained at 50°C. A mixture of the nickel sulfate aqueous solution and the cobalt sulfate aqueous solution, the sodium hydroxide aqueous solution, and the complexing agent were fed into the reaction zone. A coprecipitation reaction was thus initiated in the reaction zone.

The reaction zone pH was controlled between 11.7 and 12.0 and the reaction zone starting material and slurry were withdrawn until the solids concentration stabilized at 400 g/L. The reaction equipment was continuously operated for 72 hours from the start of the coprecipitation reaction. The slurry was then discharged from the reaction zone via pump 14 . The slurry was filtered to separate and wash the composite metal hydroxide. This composite metal hydroxide was dried at 80° C. in the air. The composition of the obtained composite metal hydroxide was Ni _0.858 Co _0.142 (OH) ₂ . The average particle size of the particles was 8.6 μm. In this way, nickel-cobalt composite metal hydroxide particles were obtained in the form of powder. The properties of this nickel-cobalt composite metal hydroxide were evaluated from the same viewpoint as in Example 1. Table 1 shows the results.

As shown in FIGS. 5 to 10 and Table 1, in the comparative example in which the liquid temperature in the reaction zone was lower than 60° C. and the stirring power applied to the reaction zone exceeded 2.2 kW / m ³ , the obtained composite metal water Cracks are generated in the oxide particles, and the shape thereof is distorted compared to the examples. On the other hand, the composite metal hydroxides of Examples are spherical or near-spherical without cracks even if they have a large particle size. If such a composite metal hydroxide is used as a precursor, it can be expected to obtain spherical or near-spherical NCA-based positive electrode active material particles without cracks despite the large particle size.

According to the method of the present invention, a relatively large particle size and spherical NCA-based positive electrode active material precursor and a relatively large particle size and spherical NCA-based positive electrode active material using the same can be produced. The present invention contributes to improved discharge capacity and volumetric capacity for lithium ion batteries.

1 inclined plate settler 2 lamella 3 groove 4 inclined plate settler 5 lamella 6 rail system 7 solid particles 8 lamella 9 straight line 10 paddle blade 11 heat exchanger 12 inclined plate settler 13 reactor 14 pump 15 slurry flow 16 circulation pump 17 Pump 18 Circulation vessel 19 Slurry flow 20 Circulation vessel 21 Pump 22 Pump 23 Metal aqueous solution supply pump 24 Complexing agent supply pump 25 pH adjuster supply pump 26 Pure water supply pump

Claims (4)

Composition: Ni _a Co _b Al _c (OH) _d (a = 0.70 to 0.95, b = 0.02 to 0.20, c = 0 ~ 0.1, d = 2.0 to 2.1, a + b + c = 1).
Using an apparatus comprising a reactor comprising a supply of starting materials, a reaction zone in which the coprecipitation reaction proceeds, and a slurry outlet from the reaction zone, and ancillary equipment thereof ,
The liquid temperature in the reaction zone is 60° C. or higher,
The stirring power applied to the reaction zone is 0.5 kW/m ³ or more and 2.2 kW /m ³ or less,
When the coprecipitation reaction in the reaction zone reaches a steady state, the slurry of the composite metal hydroxide is removed from the reactor at a constant flow rate by a pump and transferred to the next drying step.
A method for producing a composite metal hydroxide. 2. The composite metal according to claim 1, wherein the particles comprising the composite metal hydroxide are spherical or near-spherical, and cracks on the surfaces of the composite metal hydroxide particles are not observed in a scanning electron micrograph magnified 1000 times. A method for producing a hydroxide. An apparatus for producing a compound by precipitation in a reactor, comprising:
The apparatus includes a reactor and its accessories, which are provided with a starting material supply, a reaction zone in which the coprecipitation reaction proceeds, and a slurry outlet from the reaction zone,
said reactor having a tilt plate settling device adapted to intimately mix a starting material solution upon introduction into a reaction zone of said reactor,
said inclined plate settler is integrated with said reactor such that it is directly connected to said reaction zone and is connected to at least one circulation vessel via at least one pump;
aspirating turbid liquid from the product suspension in the reactor to the at least one circulation vessel and removing the liquid from the circulation vessel after removing solid particulate fractions from the turbid liquid through a filter element; , and by direct recycling to the reactor, the particle size distribution of the product suspension in the reactor is shifted to higher D50 values, compound by precipitation in the reactor Equipment for manufacturing:
The method for producing a composite metal hydroxide according to claim 1 or 2, wherein A step of producing a precursor of a positive electrode active material for a lithium ion battery by the method for producing a composite metal hydroxide according to any one of claims 1 to 3, and a mixture containing the precursor and at least a lithium compound. A method for producing a lithium ion battery positive electrode active material, comprising the step of firing.

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