Powder and granular material mixing and transport equipment

Abstract

To provide mixing and conveying equipment which homogeneously mixes two kinds or more of particulate objects different in a specific gravity and an average particle diameter, then conveys the homogeneously mixed particulate objects not through human means, and can charge the particulate objects to a conveyance destination while substantially maintaining a state before being conveyed.SOLUTION: Mixing and conveying equipment comprises: first mixing means 10 comprised of a powder mixer with a chopper suitable for mixing two kinds or more particulate object having a specific gravity difference and / or an average particle diameter difference; conveyance means 20 preferably comprised of a pneumatically conveying device automatically conveying an obtained admixture; and second mixing means 30 preferably comprised of a ribbon type mixer or a double conical type mixer remixing the conveyed admixture in such a way as to become a homogeneous state of the same degree as before conveyed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mixing and conveying facility for powder and granular materials having differences in specific gravity and average particle size. [Background technology]

[0002] In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, there is an increasing demand for small, lightweight secondary batteries with high energy density. In addition, there is also an increasing demand for high-output secondary batteries in the field of electric vehicles, including hybrid vehicles. As a secondary battery suitable for these applications, non-aqueous electrolyte secondary batteries, which have a structure in which an electrolyte is filled between a negative electrode and a positive electrode facing each other with a separator in between, have attracted attention. In particular, research and development of lithium-ion secondary batteries using materials capable of desorbing and inserting lithium into the active materials of the negative and positive electrodes has been actively carried out. In addition, it is expected that in the future, all-solid-state batteries in which the positive electrode, negative electrode, and electrolyte are all solid, will be put to practical use as lithium-ion secondary batteries.

[0003] The positive electrode active materials for the lithium ion secondary batteries proposed so far include, for example, lithium nickel composite oxide (LiNiO2) and lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), and these positive electrode active materials are prepared, as disclosed in Patent Document 1, for example, by mixing a powdered nickel compound, such as nickel hydroxide or nickel oxide containing a metallic element such as nickel, cobalt, or manganese, with a powdered lithium compound, such as lithium hydroxide, lithium carbonate, or lithium nitrate, and then firing the resulting lithium-nickel mixture. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-192424 A Summary of the Invention [Problem to be solved by the invention]

[0005] When preparing a positive electrode active material by mixing and baking the nickel compound and the lithium compound, the ratio (Li / Me) of the number of lithium atoms (Li) to the number of atoms of metals other than lithium (Me) is adjusted to be within a specified range in order to prevent variation in the battery characteristics of a lithium ion secondary battery using the obtained positive electrode active material as a positive electrode material, because even a slight deviation of Li / Me from the specified range may cause the lithium ion secondary battery to fail to achieve the desired performance.

[0006] For this reason, when preparing a lithium-nickel mixture by mixing a nickel compound and a lithium compound as described above, a suitable powder mixer is used to mix the mixture homogeneously so that the powder particles do not become unevenly distributed or segregated in the mixture. The lithium-nickel mixture thus homogeneously mixed is generally transported to a heating furnace located at a distant location and then heat-treated, and the degree of homogeneity of the homogeneously mixed lithium-nickel mixture may be significantly reduced due to the difference in specific gravity and average particle size between the nickel compound and the lithium compound during this transportation. Therefore, for example, the lithium-nickel mixture after mixing is filled into a flexible container bag (flexible container bag), and the flexible container bag is carefully transported by a forklift while taking care to minimize vibration and impact.

[0007] However, the above-mentioned manual transportation using FIBC bags is inefficient, and since there are individual differences in how to handle FIBC bags and how to operate forklifts, different workers may cause differences in the degree of homogeneity of the lithium-nickel mixture in the FIBC bags, which may result in large variations in the battery characteristics of the lithium-ion secondary batteries that are ultimately produced.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a mixing and transporting facility that can transport two or more types of powdered or granular materials having different specific gravities and average particle sizes, such as nickel compounds and lithium compounds, after homogeneously mixing them without manual intervention, and that can load the materials into a destination device while maintaining almost the same homogeneous state as they were before transporting. [Means for solving the problem]

[0009] In order to achieve the above object, the mixing and conveying equipment according to the present invention is a device for mixing two or more kinds of powders having a difference in specific gravity and / or an average particle size. Consists of a powder mixer with a chopper A first mixing means, a conveying means for automatically conveying the mixture obtained by the first mixing means, and a remixing means for remixing the mixture conveyed by the conveying means so that the mixture is in a homogeneous state similar to that before the conveying. Consists of a ribbon mixer or a double cone mixer and a second mixing means. Effect of the Invention

[0010] According to the present invention, two or more types of powder or granular materials having differences in specific gravity or average particle size can be mixed homogeneously and then transported without manual intervention, and the mixture can be loaded into a device at the destination while maintaining almost the same homogeneous state as before transportation. [Brief description of the drawings]

[0011] [Figure 1] 1 is a partially cutaway front view showing one embodiment of a mixed conveying facility according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the manufacturing method of the positive electrode active material used for the positive electrode material of the non-aqueous electrolyte secondary battery will be described by taking as an example the case where the mixing and conveying equipment of the embodiment of the present invention is applied to the mixing step of the powdered nickel compound and the powdered lithium compound, which are the precursors of the positive electrode active material, the conveying step of the lithium nickel mixture obtained by this mixing, and the remixing step before the conveyed lithium nickel mixture is charged into the conveying destination equipment. First, the positive electrode active material for the non-aqueous electrolyte secondary battery prepared using the lithium nickel mixture handled by the mixing and conveying equipment of the embodiment of the present invention and the manufacturing method thereof will be described.

[0013] 1. Positive electrode active material for non-aqueous electrolyte secondary battery and its manufacturing method 1.1 Cathode active material Among non-aqueous electrolyte secondary batteries, a positive electrode active material used as a positive electrode material for a lithium ion secondary battery can be, for example, a lithium nickel composite oxide having a hexagonal layer structure. This lithium nickel composite oxide has a form of secondary particles in which a plurality of primary particles are aggregated, and in addition to lithium (Li) and nickel (Ni) as essential metal elements, at least one element selected from the group consisting of cobalt (Co), manganese (Mn), W (tungsten), Zr (zirconium), V (vanadium), Mg (magnesium), Mo (molybdenum), Nb (niobium), Ti (titanium), Si (silicon), and Al (aluminum) is contained as necessary. The substance amount ratio of the above metal elements is determined in consideration of the battery characteristics required for the secondary battery.

[0014] 1.2 Manufacturing method of positive electrode active material The lithium nickel composite oxide can be produced by mixing a powdered nickel compound and a lithium compound as precursors in a powder mixer at a predetermined mixing ratio, and then charging the resulting lithium nickel mixture into a calcination furnace and calcining the mixture at a predetermined calcination temperature for a predetermined time. The nickel compound is an alloy of nickel and any metal element other than lithium, and contains at least one of a nickel composite hydroxide produced by crystallization and a nickel composite oxide produced by subjecting the nickel composite hydroxide to a heat treatment. Each of the crystallization step of producing a nickel composite hydroxide as a nickel compound that is a precursor of the lithium nickel composite oxide, the mixing step of adding a lithium compound to the nickel compound obtained in the crystallization step at a predetermined mixing ratio and mixing them, and the calcination step of calcining the lithium nickel mixture obtained in the mixing step will be described below.

[0015] (Crystallization process) The method for producing the nickel composite hydroxide is not particularly limited, and it can be produced by various methods. In general, a crystallization method capable of efficiently producing a nickel composite hydroxide having a desired composition in the form of a powder having a desired particle size distribution is adopted, and in particular, a continuous crystallization method capable of maintaining the crystallization reaction under constant conditions is preferably adopted. By producing the nickel composite hydroxide by this continuous crystallization method, the average particle size of the secondary particles of the nickel composite hydroxide can be stably grown to, for example, about 8.0 to 30.0 μm. The nickel composite hydroxide produced by the above crystallization method has a particle structure consisting of secondary particles formed by agglomeration of primary particles. The secondary particles of this nickel composite hydroxide may contain a small amount of primary particles.

[0016] In the production of nickel composite hydroxide by this crystallization method, an aqueous alkali solution such as an aqueous sodium hydroxide solution, an aqueous ammonia solution containing an ammonium ion donor, and water are poured into a reaction tank equipped with a stirrer in advance so that the pH is within a range of 10.0 to 13.0 at a liquid temperature of 25°C and the ammonium ion concentration is 5 to 20 g / L, and then mixed to prepare a pre-reaction aqueous solution. The liquid temperature of this pre-reaction aqueous solution is preferably adjusted to 40 to 70°C. The pH of the pre-reaction aqueous solution can be adjusted by the amount of the aqueous alkali solution, and the ammonium ion concentration can be adjusted by the amount of the aqueous ammonia solution.

[0017] Next, prepare metal compounds blended so that the atomic ratio (substance ratio) of metals corresponds to the atomic ratio (substance ratio) of metals constituting the target nickel composite hydroxide particles, add them to water and dissolve them, and supply the raw material aqueous solution to the pre-reaction aqueous solution prepared above and mix them. In this way, it is preferable to maintain the liquid temperature of the reaction aqueous solution produced by mixing the pre-reaction aqueous solution and the raw material aqueous solution in the reaction tank at 40 to 70°C. If the liquid temperature is less than 40°C, it becomes difficult to control the produced nickel composite hydroxide within the desired volume average particle size range, and conversely, if the liquid temperature exceeds 70°C, the amount of ammonia volatilization becomes too large, making the concentration of the nickel ammine complex unstable.

[0018] The ammonium ion donor used in the preparation of the pre-reaction aqueous solution is not particularly limited, and for example, ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc. can be used. The alkaline aqueous solution used to adjust the pH of the pre-reaction aqueous solution is also not particularly limited, and for example, an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide can be used. The alkali metal hydroxide may be added to the aqueous solution in the reaction tank as a powder or granule, rather than as an aqueous solution. However, from the viewpoint of ease of controlling the pH value of the aqueous solution in the reaction tank, it is preferable to add the alkali aqueous solution to the aqueous solution in the reaction tank as described above.

[0019] When the nickel composite hydroxide used as a precursor is a nickel-cobalt-manganese composite hydroxide and the composition of this nickel composite hydroxide contains an element M selected from the group consisting of W, Zr, V, Mg, Mo, Nb, Ti, Si, and Al, the element M may be crystallized together with Ni, Co, and Mn to uniformly disperse the element M in the nickel-cobalt-manganese composite hydroxide. Alternatively, a nickel-cobalt-manganese composite hydroxide may be first produced by crystallization using a raw material not containing the element M, and then the surfaces of the obtained nickel-cobalt-manganese composite hydroxide particles may be coated with a compound containing the element M, or a compound containing the element M may be added and mixed at the same time as a lithium compound is added to this nickel-cobalt-manganese composite hydroxide.

[0020] As described above, when at least a part of the nickel compound is converted into a nickel composite oxide, the nickel composite hydroxide produced above may be oxidized and roasted. As a result, a part or all of the nickel composite hydroxide is oxidized and converted into a nickel composite oxide. The atmospheric temperature of this oxidizing roasting is preferably 350°C to 800°C, more preferably 600°C to 750°C. The time period for oxidizing roasting is preferably 2 hours to 8 hours, more preferably 6 hours to 7 hours.

[0021] (Mixing process) In the mixing step, the nickel compound containing at least one of the nickel composite hydroxide and the nickel composite oxide obtained in the crystallization step and a lithium compound prepared separately are charged into a mixer at a predetermined blending ratio and mixed. This produces a lithium-nickel mixture. The blending ratio of the nickel compound and the lithium compound is adjusted so that the ratio (Li / Me) of the substance amount of lithium (Li) to the substance amount (Me) of metal elements other than lithium in the lithium-nickel mixture is preferably 0.95 or more and less than 1.20.

[0022] The nickel compound and the lithium compound must be mixed thoroughly to be homogeneous, and if the mixing is insufficient, the lithium-nickel mixture may have some parts that are outside the Li / Me range. In particular, the nickel compound and the lithium compound have different specific gravities and average particle sizes, which may lead to localized bias in the Li / Me ratio.

[0023] The Li / Me ratio of the lithium nickel mixture obtained by the above mixing hardly changes before and after the next firing step. That is, the Li / Me ratio of the lithium nickel mixture obtained by this mixing step becomes the Li / Me ratio of the positive electrode active material as it is. Therefore, the mixing ratio of the nickel compound and the lithium compound is adjusted so that the Li / Me ratio of the lithium nickel mixture becomes the same value as the Li / Me ratio of the target positive electrode active material.

[0024] The lithium compound is not particularly limited, and for example, one of lithium hydroxide, lithium nitrate, and lithium carbonate or a mixture of two or more of them can be used. Among these, lithium hydroxide or lithium carbonate is preferred from the viewpoint of ease of handling and quality stability, and lithium hydroxide having an average particle size of 30 μm to 100 μm is more preferred. Here, the average particle size means the particle size at 50% of the volume accumulated value in the particle size distribution obtained by a laser diffraction / scattering method.

[0025] (Firing process) In the calcination step, the lithium-nickel mixture obtained in the mixing step is calcined to produce a lithium-nickel composite oxide as a positive electrode active material. The calcination conditions are, for example, in an oxidizing atmosphere, preferably at a calcination temperature of 650°C to 1100°C, more preferably at a calcination temperature of 800°C to 950°C. The calcination time in this case is not particularly limited, but is preferably 3 hours to 48 hours, more preferably 6 hours to 24 hours. The above calcination atmosphere, calcination temperature, and calcination time are appropriately adjusted depending on the composition and physical properties of the nickel compound to be calcined, the type of lithium compound, and the like.

[0026] The heating furnace used in the above calcination treatment is not particularly limited as long as it can heat-treat the lithium-nickel mixture in the air or oxygen flow, but since it is preferable to perform the calcination treatment while maintaining the atmosphere in the furnace uniform, it is preferable to use a furnace with a structure that does not generate combustion gas in the heat treatment chamber. An example of a heating furnace with such a structure is an electric furnace. The heating furnace may be of a batch type or a continuous type.

[0027] 2.Mixed transport equipment Next, a mixing and conveying equipment according to an embodiment of the present invention will be described. This mixing and conveying equipment is an equipment for mixing nickel compounds and lithium compounds in the above-mentioned mixing step, conveying the obtained lithium-nickel mixture to a heating furnace in the above-mentioned firing step, and remixing before charging the lithium-nickel mixture into the heating furnace. Specifically, as shown in FIG. 1, the mixing and conveying equipment according to an embodiment of the present invention includes a first mixing means 10 for mixing nickel compounds and lithium compounds in powder form having different specific gravities and average particle sizes, a conveying means 20 for automatically conveying the mixture obtained by the first mixing means 10, and a second mixing means 30 for remixing the mixture conveyed by the conveying means 20 so as to be in a homogeneous state similar to that before the conveying.

[0028] With this configuration, the lithium-nickel mixture homogeneously mixed by the first mixing means 10 can be transported to a predetermined position without manual intervention, and even if the degree of homogeneity is reduced by the transport, the lithium-nickel mixture is remixed by the second mixing means to the same degree of homogeneity as before the transport, so that the lithium-nickel mixture can be charged into the heating furnace in a state in which the bias in Li / Me, which is an index of the degree of homogeneity, is suppressed. This makes it possible to efficiently produce a high-quality positive electrode active material with reduced quality variation. Below, each device constituting the mixing and transporting facility of the embodiment of the present invention will be described in detail.

[0029] 2.1 First Mixing Method The first mixing means 10 constituting the mixing and conveying equipment according to the embodiment of the present invention is a device for homogeneously mixing two or more kinds of powders having differences in specific gravity and / or average particle size. The type of mixer used for this first mixing means 10 may be a powder mixer such as a ribbon mixer or a double cone mixer, but it is more preferable to use a batch-type powder mixer for dispersion mixing that is equipped with a stirring mixing blade 11 for mixing two or more kinds of powders and a high-speed rotating blade 12 for disintegrating and dispersing agglomerates by using a shear force.

[0030] As described above, the reason why it is more preferable to use a powder mixer for dispersion mixing as the first mixing means 10 is that, since the objects to be mixed may contain agglomerates formed by the aggregation of secondary particles due to heat treatment or the like, such as when the nickel compound contains a nickel composite oxide obtained by subjecting a nickel composite hydroxide to heat treatment, it is preferable for the first mixing means 10 to have a function for crushing these agglomerates. Crushing refers to the application of mechanical energy to agglomerates made up of secondary particles generated by sintering necking between secondary particles during firing, thereby separating the bonds between the secondary particles without destroying the secondary particles themselves, a so-called loosening operation.

[0031] A specific example of the powder mixer for dispersion mixing is a ribbon-type powder mixer with a chopper, which is equipped with a ribbon-type screw blade that rotates around an axis extending horizontally in the mixing vessel and a chopper blade that protrudes from diagonally below the mixing vessel. Alternatively, a shovel-type powder mixer with a chopper, which is equipped with a shovel-type blade that rotates around an axis extending horizontally in the mixing vessel and a chopper blade that protrudes from diagonally below the mixing vessel, or a fluidization mixer that performs dispersion mixing by rotating a lower fluidization blade and an upper chopper blade that are coaxially provided on a rotation axis extending vertically in the mixing vessel at high speed may be used.

[0032] By using a powder mixer equipped with a blade mainly responsible for stirring and mixing as described above and a chopper blade mainly responsible for crushing and dispersing as the first mixing means 10, even if the materials to be mixed contain agglomerates, the lithium-nickel mixture discharged from the bottom of the mixing container of the first mixing means 10 can be made extremely homogeneous, specifically, the variation (3σ) of Li / Me, which is an index of the degree of homogeneity, can be suppressed to 0.03 or less. As a result, the variation (3σ) of Li / Me of the positive electrode active material obtained after the firing treatment in the subsequent heating furnace can be suppressed to 0.03 or less, and the quality of the battery characteristics of the lithium-ion secondary battery using this can be stabilized.

[0033] If the material to be mixed contains almost no agglomerates, even a simple powder mixer can suppress the above-mentioned Li / Me variation (3σ) to 0.03 or less by appropriately adjusting the rotation speed and mixing time, but if the material to be mixed contains agglomerates, the above-mentioned Li / Me may vary greatly when mixed using a powder mixer that does not have a chopper blade in the first mixing means 10. For example, mixers such as a double cone mixer that rotates a mixing container shaped like two approximately cone-shaped members with asymmetric centers of gravity around an axis extending horizontally to perform stirring and mixing, or a ribbon mixer that rotates a ribbon-shaped screw blade around an axis extending horizontally in the mixing container to perform stirring and mixing, may have difficulty in suppressing the above-mentioned Li / Me variation (3σ) to 0.03 or less.

[0034] 2.2 Means of transportation The conveying means 20 constituting the mixing and conveying equipment of the embodiment of the present invention is located downstream of the above-mentioned first mixing means 10, and a known conveying device can be used. This conveying device is not particularly limited as long as it can automatically convey the mixture without manual intervention, and for example, a pneumatic conveying device that conveys powder and granular material by air flowing inside a pipe may be used, or a mechanical conveying device such as a screw conveyor, a belt conveyor, or a bucket conveyor may be used, and is appropriately selected in consideration of the facility layout of the factory, the facility cost, and the like.

[0035] 1 shows an example in which a pneumatic transport device capable of compactly arranging the transport line is adopted as the transport means 20. That is, the pneumatic transport device shown in Fig. 1 is mainly composed of a pressurized bin 21 located below the above-mentioned first mixing means 10, into which compressed air for pressure transport is introduced after receiving the lithium-nickel mixture mixed in the first mixing means 10, a transport pipe 22 for pressure transporting the lithium-nickel mixture discharged from the pressurized bin 21 at a constant discharge amount per unit time to a predetermined position, a recovery hopper 23 for receiving the lithium-nickel mixture pressure transported by the transport pipe 22, and an air compressor (not shown) for supplying compressed air for pressure transport to the pressurized bin 21.

[0036] With this configuration, the lithium-nickel mixture mixed in the first mixing means 10 is charged into the pressurized bin 21 connected to the bottom outlet 13 of the first mixing means 10, and then is supplied into the transport pipe 22 at a constant supply amount per unit time by compressed air supplied from the air compressor into the pressurized bin 21, and is pumped directly to the recovery hopper 23. A cyclone and a filter are provided at the inlet of the recovery hopper 23, and the lithium-nickel mixture separated into solid and gas here is charged into the recovery hopper 23. The pneumatic transport device may employ either a low-concentration transport method in which powder particles are pumped while suspended in a high-speed air current, or a high-concentration transport method in which powder particles are pumped in a plug-like shape by a low-speed air current, but the high-concentration transport method, which can pump the powder particles in a more homogeneous state, is preferred.

[0037] 2.3 Secondary mixing method The second mixing means 30 constituting the mixing and conveying equipment of the embodiment of the present invention remixes the lithium-nickel mixture conveyed by the conveying means 20, and thereby, a remixture that is almost as homogeneous as the lithium-nickel mixture before conveying can be obtained. This second mixing means 30 is provided below the recovery hopper 23, and the lithium-nickel mixture conveyed by the conveying means 20 is temporarily stored in the recovery hopper 23, and then cut out at a constant discharge rate per unit time continuously or in several batches and charged into the second mixing means 30 for remixing. The lithium-nickel mixture remixed by this second mixing means 30 is discharged as a remixture from the bottom discharge port 31 of the second mixing means 30, and then charged into a heating furnace for a calcination process (not shown) connected to the bottom discharge port 31.

[0038] This second mixing means 30 may be a powder mixer of the same type as the first mixing means 10 described above, but while the first mixing means 10 requires consideration of disintegrating agglomerates if the materials to be mixed contain agglomerates, the second mixing means 30 basically only requires remixing to restore the degree of homogeneity of the lithium-nickel mixture that was reduced during transport by the transport means 20, so it does not necessarily need to be equipped with chopper blades and a powder mixer of a simpler structure may be used.

[0039] That is, it is preferable to select a powder mixer for the second mixing means 30 that can restore the Li / Me variation (3σ) of the lithium nickel mixture obtained after remixing to the Li / Me variation (3σ) before transport, specifically, that can suppress the Li / Me variation (3σ) of the remix to 0.03 or less. For example, when a chopper-equipped ribbon mixer is used in the first mixing means 10, a powder mixer such as a ribbon mixer or a double cone mixer having a simpler structure than the chopper-equipped ribbon mixer can be used. This allows the second mixing means 30 to be installed relatively easily even in a narrow installation space or when the installation location is high.

[0040] By using the mixing and conveying equipment of the above configuration, two or more kinds of powders having differences in specific gravity and average particle size can be homogeneously mixed and then conveyed without manual means, and the homogeneous state before conveying can be almost maintained and charged into the device of the conveying destination. In addition, the lithium-nickel mixture conveyed via the conveying means 20 after being mixed and crushed as necessary in the first mixing means 10 is accumulated in layers when temporarily stored in the recovery hopper 23, and then cut out continuously or for each batch at a constant discharge rate per unit time from the bottom discharge outlet of the recovery hopper 23 and charged into the second mixing means 30. However, since the lithium-nickel mixture is already sufficiently homogeneously mixed in the first mixing means 10, it is possible to suppress the homogeneity of the lithium-nickel mixture remixed in the second mixing means 30 from fluctuating over time or varying from lot to lot.

[0041] That is, if the mixing in the first mixing means 10 and the disintegration performed as necessary are insufficient, for example, a lithium-nickel mixture containing residual agglomerates or a lithium-nickel mixture with a significantly reduced degree of homogeneity will be discharged from the first mixing means 10. As a result, there are cases in which the degree of homogeneity of the lithium-nickel mixture conveyed in constant amounts to the recovery hopper 23 by the conveying means 20 varies greatly over time, and as a result, the degree of homogeneity of the lithium-nickel mixture accumulated in the recovery hopper 23 differs greatly in the height direction of the recovery hopper 23.

[0042] In this way, if non-uniformity in the vertical direction occurs within the recovery hopper 23, when the lithium-nickel mixture is continuously charged from the recovery hopper 23 to the second mixing means 30, or when the lithium-nickel mixture stored in the recovery hopper 23 is divided into multiple batches and charged to the second mixing means 30, the degree of homogeneity of the lithium-nickel mixture discharged from the bottom of the recovery hopper 23 will vary, so that even if the mixture can be uniformly remixed by the second mixing means 30, the degree of homogeneity of this remix will differ for each mixing lot (batch).

[0043] In contrast, the mixing and conveying equipment of the embodiment of the present invention mixes two or more types of powders having differences in specific gravity or average particle size in the first mixing means and crushes them as necessary to mix them sufficiently homogeneously, so that the homogeneity of the remixed lithium-nickel mixture obtained by remixing in the second mixing means 30 can be made constant throughout the entire lot. This makes it possible to suppress variations in the quality of the lithium-ion secondary batteries finally obtained.

[0044] The powder / granular material mixing and conveying equipment according to the embodiment of the present invention has been described above in terms of the case where the precursor of the positive electrode active material used in the positive electrode material of a non-aqueous electrolyte secondary battery is mixed and conveyed, but the present invention is not limited thereto and includes various modifications and alternative examples within the scope of the present invention. For example, the powder / granular material mixing and conveying equipment of the present invention can be suitably applied to the case where the precursor of the positive electrode active material used in the positive electrode material of an all-solid-state battery in which the positive electrode, negative electrode, and electrolyte are all solid-state is mixed and conveyed. EXAMPLES

[0045] [Example 1] The nickel compound and the lithium compound were mixed, conveyed, and remixed using a mixing and conveying facility as shown in FIG. 1, and the degree of homogeneity of the mixture at each stage was evaluated by the variation (3σ) of Li / Me. Specifically, a nickel composite oxide (average particle size 12 μm, bulk density 1.1 g / cc) containing nickel, cobalt, and aluminum as metal elements was prepared as the nickel compound, and lithium hydroxide (average particle size 66.8 μm, bulk density 0.31 g / cc) was prepared as the lithium compound. These two compounds were weighed out to a predetermined blend ratio and charged into a chopper-equipped ribbon mixer as the first mixing means 10, and mixed for 10 minutes to prepare a lithium-nickel mixture. Ten samples were taken from this lithium-nickel mixture, and the components were quantitatively analyzed by ICP emission spectroscopy (ICP: Inductively Coupled Plasma) to obtain the variation (3σ) of Li / Me.

[0046] The obtained lithium-nickel mixture was discharged into the pressurized bin 21 of the conveying means 20, and then compressed air was introduced to pneumatically convey the lithium-nickel mixture toward the recovery hopper 23 via the transport pipe 22. Ten samples (n=10) were taken from the lithium-nickel mixture pressure-fed into the recovery hopper 23, and the components were quantitatively analyzed in the same manner as above to determine the variation (3σ) of Li / Me. The standard deviation σ was calculated based on the following formula. Here, x i is the value of Li / Me for each sample (i = 1 to n), and μ is the x i is the arithmetic mean value of

number

[0047] Thereafter, the lithium mixture was charged from the recovery hopper 23 into a ribbon-type mixer, which was the second mixing means 30, and remixed for 10 minutes. Ten samples (n=10) were taken from the remixed lithium-nickel mixture, and the components were quantitatively analyzed in the same manner as above to determine the Li / Me variation (3σ).

[0048] [Example 2] The nickel compound and the lithium compound were mixed, conveyed, and remixed in the same manner as in Example 1 above, except that the second mixing means 30 was a double cone mixer instead of a ribbon mixer.

[0049] [Reference example] As a reference example, the same procedure as in Example 1 was carried out except that only mixing was performed in the first mixing means 10, and transport and remixing were not performed. Then, 10 samples were taken from the obtained lithium-nickel mixture, and the components were quantitatively analyzed by the same analytical method as in Example 1 to obtain the Li / Me variation (3σ). As the first mixing means 10, a ribbon type mixer was used in Reference Example 1, and a double cone type mixer was used in Reference Example 2. The results of Examples 1 and 2 and Reference Examples 1 and 2 are shown in Table 1 below.

[0050] [Table 1]

[0051] As can be seen from the results of Examples 1 and 2 in Table 1 above, by using a chopper-equipped ribbon mixer as the first mixing means, the Li / Me variation (3σ) of the lithium nickel mixture after mixing can be suppressed to 0.03 or less. It can also be seen that the Li / Me can be suppressed to 0.03 or less when this lithium nickel mixture is pneumatically transported and then remixed by the second mixing means 30. In other words, even if the degree of homogeneity is reduced by pneumatic transport, it can be restored to the homogeneity before transport by remixing. In addition, by using the mixing and transporting equipment of Examples 1 and 2, a reduction in the number of steps of 6 per 1000 t of lithium nickel mixture was achieved compared to the conventional case of transporting by forklift after mixing.

[0052] On the other hand, when a ribbon mixer (Reference Example 1) or a double cone mixer (Reference Example 2) was used as the first mixing means 10, the Li / Me variation (3σ) of the lithium-nickel mixture after mixing could not be suppressed to 0.03 or less. This is thought to be because a large amount of agglomerates was contained because a nickel composite oxide produced by a firing process was used as the nickel compound, and agglomerates remained in the lithium-nickel mixture after mixing in the powder mixers of Reference Examples 1 and 2 that were not equipped with chopper blades.

[0053] In the case of such a lithium-nickel mixture with a low degree of homogeneity, it is believed that the degree of homogeneity will vary greatly for each mixed lot (batch) even if the mixture is thoroughly remixed, and when agglomerates are present, it is believed that it will be difficult to suppress the variation (3σ) of Li / Me in the remix to 0.03 or less throughout the entire lot unless a powder mixer similar to the powder mixer used in the above embodiment is used as the first mixing means 10. [Explanation of symbols]

[0054] 10 First mixing means 11 Stirring and mixing blade 12 High-speed rotor blades 13 Bottom outlet 20 Means of transportation 21 Pressurized Bottle 22 Transportation piping 23 Collection Hopper 30 Second mixing means 31 Bottom outlet

Claims

1. A mixing and conveying facility comprising: a first mixing means consisting of a powder mixer with a chopper that mixes two or more types of powder or granular materials having differences in specific gravity and / or average particle size; a conveying means that automatically conveys the mixture obtained by the first mixing means; and a second mixing means consisting of a ribbon-type mixer or a double cone-type mixer that remixes the mixture conveyed by the conveying means to a homogeneous state similar to that before the conveying.

2. 2. The mixing and conveying facility according to claim 1, wherein the first mixing means breaks down agglomerates that may be contained in the two or more types of powder or granular materials.

3. 3. The mixing and conveying facility according to claim 1 or 2, wherein the conveying means is a pneumatic conveying device.

4. 4. The mixed conveying facility according to claim 1, wherein the mixture is a lithium-nickel mixture obtained by mixing a nickel compound containing at least one of a nickel composite hydroxide and a nickel composite oxide obtained by heat-treating the nickel composite hydroxide, with a lithium compound.

5. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery or an all-solid-state battery, comprising: a mixing step and a conveying step of mixing and conveying a lithium-nickel mixture obtained by mixing a nickel compound containing at least one of a nickel composite hydroxide and a nickel composite oxide obtained by heat-treating the nickel composite hydroxide with a lithium compound, in a mixing and conveying facility described in any one of claims 1 to 4; and a calcination step of calcining the remixture produced in the mixing and conveying steps.

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