JP6973223B2 - Manufacturing method of active material mixture - Google Patents

Description

The present application discloses a method for producing an active material mixture.

As a positive electrode mixture or a negative electrode mixture for a solid battery, an active material mixture containing an active material, a solid electrolyte, and a conductive material is known. Such an active material mixture can be produced, for example, by mixing an active material, a solid electrolyte, a conductive material, and a dispersion medium using various kneaders as disclosed in Patent Documents 1 and 2. .. On the other hand, as disclosed in Patent Document 3, a powder mixing pump capable of sucking powder, feeding liquid, and mixing powder and liquid is known.

Japanese Unexamined Patent Publication No. 2017-20455 Japanese Unexamined Patent Publication No. 2017-20705 Japanese Patent No. 4458536

According to a new finding of the present inventor, in a circulation type mixing apparatus provided with a powder mixing pump as disclosed in Patent Document 3, when mixing an active material mixture while circulating a dispersion medium, a combination is performed. The solid electrolyte in the material tends to aggregate, and it may be difficult to reduce the particle size of the mixture.

The present application presents, as one of the means for solving the above-mentioned problems, a powder supply device, a stirring tank having a stirring device, a liquid feeding pump, powder suction, liquid feeding, and powder and liquid. The active material is provided with a powder mixing pump capable of mixing the above, and the mixing device is formed by connecting the powder supply device, the stirring tank, the liquid feeding pump, and the powder mixing pump. A method for producing a mixture, which is a circulation step in which the mixing device is operated to circulate a dispersion medium in the mixing device, and a solid electrolyte is supplied from the powder supply device in a state where the mixing device is operated. After the first dispersion step of supplying and dispersing in the dispersion medium and the first dispersion step, the active material and the conductive material are supplied from the powder supply device in a state where the mixing device is operated. Disclosed is a method for producing an active material mixture, which comprises a second dispersion step of dispersing in the dispersion medium.

In the case of mixing the active material mixture while circulating the dispersion medium in a circulation type mixing device equipped with a powder mixing pump as in the manufacturing method of the present disclosure, after the solid electrolyte is dispersed in the dispersion medium. By dispersing the active material and the conductive material in the mixture, it is possible to suppress the aggregation of the solid electrolyte in the mixture and reduce the particle size of the mixture.

It is a schematic diagram for demonstrating the structure of a mixing apparatus 100. It is a figure for demonstrating the flow of the manufacturing method S10 of an active material mixture. It is a figure which shows the result of an Example and a comparative example.

FIG. 1 schematically shows the configuration of a mixing device 100 used in the method for producing an active material mixture of the present disclosure. As shown in FIG. 1, the mixing device 100 includes a powder supply device 10, a stirring tank 20 having a stirring device 20a, a liquid feeding pump 30, and a powder mixing pump 40. The powder mixing pump 40 is capable of sucking powder, feeding liquid, and mixing powder and liquid. In the mixing device 100, the powder supply device 10, the stirring tank 20, the liquid feed pump 30, and the powder mixing pump 40 are connected, and the fluid can be circulated in the mixing device 100.

The powder supply device 10 may be any as long as it can supply powder into the mixing device 100, and its form is not particularly limited. For example, the powder charged from the charging port (hopper) 10a is introduced into the mixing device 100 by dropping, extrusion, or the like. As shown in FIG. 1, it is preferable that the powder supply device 10 is connected between the liquid feed pump 20 and the powder mixing pump 40. This is because the powder can be more appropriately supplied into the mixing device 100 by the liquid feeding by the liquid feeding pump 20 and the suction by the powder mixing pump 40. The configuration of the powder supply device 10 itself is known, and further description thereof will be omitted here.

The stirring tank 20 may be provided with a stirring device 20a inside and can stir a dispersion medium or powder. Specific examples of the stirring device 20a include, but are not limited to, a form in which the stirring blade is rotated by using the power as shown in FIG. The stirring tank 20 is provided with an inlet and an outlet for circulating the dispersion medium and the like in the mixing device 100, but may be further provided with an inlet and an outlet separately. For example, as shown by an arrow on the left side of the paper in FIG. 1, a supply port for supplying various liquids such as a dispersion medium into the stirring tank 20 and a supply port for discharging the dispersion medium and the like to the outside of the mixing device 100 are discharged. It may be provided with an outlet. The configuration of the stirring tank 20 itself is known, and further description thereof will be omitted here.

The liquid feed pump 30 may be any pump that can control the flow of the dispersion medium or the like in the mixing device 100. The liquid feed pump 30 allows the dispersion medium and the like to be circulated in one direction in the mixing device 100. As shown in FIG. 1, the liquid feed pump 30 is provided between the stirring tank 20 and the powder mixing pump 40 so as to send the dispersion medium or the like discharged from the stirring tank 20 to the powder mixing pump 40. Is preferable. The configuration of the liquid feed pump 30 itself is known, and further description thereof will be omitted here.

The powder mixing pump 40 is a pump capable of sucking powder, feeding liquid, and mixing powder and liquid. For example, as disclosed in Patent Document 3, "a rotor provided with a stirring blade is concentrically arranged inside a cylindrical casing, and the rotation of the stirring blade causes an inlet provided in front of the rotor to be used. In a pump in which a liquid is introduced to the outside of the stirring blade, a plurality of stirring blades are provided on the outer peripheral portion of a disk-shaped rotor, and a tubular stator having slits on the outside and inside of the stirring blade is provided. A powder mixing pump characterized in that a partition plate is formed to partition the inside of the inner stator into a liquid flow path and a chamber, and a powder inlet communicating with the chamber is provided in the casing. "And it is sufficient. In the circulation type mixing device 100 provided with the powder mixing pump 40, the powder can be supplied by vacuum suction, and the powder is put into the dispersion medium while preventing excessive pulverization by cavitation and shearing. It is possible to disperse efficiently.

The powder mixing pump 40 constituting the mixing device 100 is commercially available, for example, as a jet pacer (registered trademark) manufactured by Nihon Spindle Manufacturing Co., Ltd.

In the mixing device 100, the means for connecting the powder supply device 10, the stirring tank 20, the liquid feed pump 30, and the powder mixing pump 40 is not particularly limited, and if they are connected using general piping, they are not particularly limited. good. In this case, the pipe between the configurations 10 to 40 may be provided with an openable / closable discharge port. The arrangement (equipment arrangement) of the configurations 10 to 40 in the mixing device 100 shown in FIG. 1 is an example. The arrangement of the configurations 10 to 40 in the mixing device 100 is not limited to that shown in FIG. 1, and any arrangement may be used as long as the dispersion medium or the like can be circulated in the mixing device 100.

When the present inventor mixes the solid electrolyte, the active material, and the conductive material together with the dispersion medium by using the circulation type mixing device 100 equipped with the powder mixing pump 40 or the like as described above, the solid electrolyte in the mixture becomes We faced a new problem that it is easy to aggregate and it may be difficult to reduce the particle size of the mixture. As a result of trial and error in order to solve the problem, the present inventor suppresses the aggregation of the solid electrolyte and the grain size of the mixture by setting the order of supplying the solid electrolyte, the active material, and the conductive material to a specific order. Was found to be able to be significantly reduced.

FIG. 2 shows the flow of the method S10 for producing an active material mixture. As shown in FIG. 2, the manufacturing method S10 includes a powder supply device 10, a stirring tank 20 having a stirring device 20a, a liquid feeding pump 30, powder suction, liquid feeding, and powder and liquid. A powder mixing pump 40 capable of mixing the above-mentioned materials, and a mixing device 100 in which the powder supply device 10, the stirring tank 20, the liquid feeding pump 30, and the powder mixing pump 40 are connected are used. A method for producing an active material mixture, from the circulation step S1 in which the mixing device 100 is operated to circulate the dispersion medium in the mixing device 100, and from the powder supply device 10 in a state where the mixing device 100 is operated. After the first dispersion step S2 in which the solid electrolyte is supplied and dispersed in the dispersion medium and the first dispersion step S2, the active material and the conductive material are separated from the powder supply device 10 in a state where the mixing device 100 is operated. It is characterized by comprising a second dispersion step S2 which is supplied and dispersed in a dispersion medium.

1. 1. Circulation process S1
In the circulation step S1, the mixing device 100 is operated to circulate the dispersion medium in the mixing device 100. For example, the dispersion medium is supplied into the mixing device 100 from the supply port of the stirring tank 20 or the like, and the stirring device 20a, the liquid feed pump 30, and the powder mixing pump 40 are operated to bring the dispersion medium into the mixing device 100. Can be circulated. In the circulation step S1, the flow rate and the flow velocity of the dispersion medium are not particularly limited, and may be appropriately determined in consideration of productivity and the like.

The dispersion medium may be any medium that functions as a medium for dispersing the solid content described later. In particular, the dispersion medium preferably contains a solvent and a binder. In this case, the binder is preferably dissolved in a solvent, but not all of the binder is necessarily dissolved. It is also possible to use a dispersion medium in which the binder does not dissolve in the solvent and swells. The solvent constituting the dispersion medium is preferably one having as little reactivity as possible with a solid electrolyte or the like, and is preferably a non-aqueous solvent. As the non-aqueous solvent, a polar solvent, a non-polar solvent, or a combination thereof can be used without particular limitation. Examples of non-polar solvents include heptane, toluene, xylene and the like. Examples of polar solvents include ethanol, N-methylpyrrolidone, butyl acetate, butyl butyrate and the like. As the non-aqueous solvent, only one kind may be used, or two or more kinds may be mixed and used. On the other hand, as the binder, any known binder contained in the active material mixture can be adopted. For example, among styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI) and the like. At least one selected from can be used. The content of the binder in the dispersion medium is not particularly limited. The dispersion medium may contain additives such as a viscosity modifier (thickening agent) and a dispersant as long as the above problems can be solved.

2. 2. First dispersion step S2
In the first dispersion step S2, the solid electrolyte is supplied from the powder supply device 10 in a state where the mixing device 100 is operated and dispersed in the dispersion medium. The "state in which the mixing device 100 is operated" is a state in which at least one of the stirring device 20a, the liquid feed pump 30, and the powder mixing pump 40 is operated and the dispersion medium is circulated in the mixing device 100. means.

As the solid electrolyte, any known solid electrolyte constituting the active material mixture can be adopted. In particular, the above problems are likely to occur when a sulfide solid electrolyte is used. That is, from the viewpoint that the effect of the production method S10 becomes more remarkable, it is preferable to use a sulfide solid electrolyte as the solid electrolyte. As the sulfide solid electrolyte, for example, a solid electrolyte containing Li, P and S as constituent elements can be used. Specifically, Li ₂ SP ₂ S ₅ , Li ₂ S-SiS ₂ , LiI-Li ₂ S-SiS ₂ , LiI-Si _{2 SP 2} S ₅ , LiI-LiBr-Li _{2 SP. 2} S ₅ , LiI-Li _{2 SP 2} S ₅ , LiI-Li ₂ O-Li _{2 SP 2} S ₅ , LiI-Li _{2 SP 2} O ₅ , LiI-Li ₃ PO _4- P ₂ Examples thereof include S ₅ , Li ₂ S-P ₂ S _{5- GeS 2.} Among these, in _particular, sulfide solid electrolyte containing Li 2 _S-P 2 _{S 5} is more preferable. Only one type of solid electrolyte may be used alone, or two or more types may be mixed and used. The shape of the solid electrolyte is not particularly limited, but is usually particulate in the shape before being supplied to the dispersion medium (the shape when charged into the charging port 10a of the powder supply device 10). In this case, the particle size of the solid electrolyte before being supplied to the dispersion medium is preferably 0.01 μm or more and 5 μm or less. The lower limit is more preferably 0.05 μm or more, further preferably 0.1 μm or more, and the upper limit is more preferably 3 μm or less, still more preferably 2 μm or less. Alternatively, the average particle size (D ₅₀ ) of the solid electrolyte is preferably 0.01 μm or more and 5 μm or less. The lower limit is more preferably 0.05 μm or more, further preferably 0.1 μm or more, and the upper limit is more preferably 3 μm or less, still more preferably 2 μm or less. The average particle size (D ₅₀ ) referred to in the present application means a median diameter (50% volume average particle size) derived from a particle size distribution measured based on a particle size distribution measuring device based on a laser scattering / diffraction method.

In the first dispersion step S2, the supply amount of the solid electrolyte (volume ratio of the solid electrolyte to the dispersion medium, the solid content concentration in the dispersion medium) is not particularly limited, but even if the amount of the solid electrolyte is too small. If it is too much, there is a risk that productivity and the like will deteriorate. In this regard, in the first dispersion step S2, the solid electrolyte is divided into 1% by volume or more and 50% by volume or less based on the total volume of the dispersion medium and the solid electrolyte (100% by volume). It is preferable to adjust the supply amount. The lower limit is more preferably 5% by volume or more, further preferably 10% by volume or more, and the upper limit is more preferably 30% by volume or less, still more preferably 20% by volume or less.

In the first dispersion step S2, the solid electrolyte may be supplied dry from the powder supply device 10 or may be supplied wet together with a solvent or the like.

3. 3. Second dispersion step S3
In the second dispersion step S3, after the first dispersion step S2, the active material and the conductive material are supplied from the powder supply device 10 in a state where the mixing device 100 is operated and dispersed in the dispersion medium.

As the active material, any known active material that constitutes the active material mixture can be adopted. When the active material mixture is a positive electrode mixture, the active materials are lithium cobalt oxide, lithium nickel oxide, Li (Ni, Mn, Co) O ₂ (Li _{1 + α} Ni _1/3 Mn _1/3 Co _1/3). O ₂ ), lithium manganate, spinel-type lithium composite oxide, lithium titanate, lithium metal phosphate (LiMPO ₄ , M is at least one selected from Fe, Mn, Co, Ni) and other lithium-containing oxides. Can be adopted. When the active material mixture is used as a negative electrode mixture, the active material may be a silicon-based active material such as Si, Si alloy or silicon oxide, a carbon-based active material such as graphite or hard carbon, or lithium titanate. Various oxide-based active materials, lithium-based active materials such as metallic lithium and lithium alloys, and the like can be adopted. Only one type of active material may be used alone, or two or more types may be mixed and used. The shape of the active material is not particularly limited, but it is usually in the form of particles. In this case, in this case, the particle size of the active material before being supplied to the dispersion medium is preferably 0.01 μm or more and 50 μm or less. The lower limit is more preferably 0.5 μm or more, further preferably 1 μm or more, and the upper limit is more preferably 20 μm or less, still more preferably 5 μm or less. Alternatively, the average particle size (D ₅₀ ) of the active material is preferably 0.01 μm or more and 20 μm or less. The lower limit is more preferably 0.5 μm or more, further preferably 1 μm or more, and the upper limit is more preferably 20 μm or less, still more preferably 5 μm or less.

As the conductive material, any known conductive material as a conductive material constituting the active material mixture can be adopted. For example, carbon materials such as acetylene black, ketjen black, VGCF, and carbon nanofibers and metal materials such as nickel, aluminum, and stainless steel can be adopted. As the conductive material, only one kind may be used alone, or two or more kinds may be mixed and used. The shape of the conductive material is not particularly limited, but it is preferably in the form of particles or fibers. The particulate conductive material preferably has, for example, a primary particle diameter of 5 nm or more and 10 μm or less. The fibrous conductive material preferably has, for example, a fiber diameter of 10 nm or more and 1 μm or less and an aspect ratio of 20 or more.

In the second dispersion step S3, the supply amount of the active material and the conductive material (the volume ratio of the solid electrolyte to the dispersion medium, the active material and the conductive material, and the solid content concentration in the dispersion medium) is not particularly limited. If the amount of the active material and the conductive material is too small or too large, the productivity and the like may deteriorate. In this regard, in the second dispersion step S3, the total volume of the solid electrolyte, the active material, and the conductive material is 10 based on the total volume of the dispersion medium, the solid electrolyte, the active material, and the conductive material (100% by volume). It is preferable to adjust the supply amount of the active material and the conductive material so as to be 50% by volume or more and 70% by volume or less. The lower limit is more preferably 20% by volume or more, further preferably 30% by volume or more, and the upper limit is more preferably 50% by volume or less, still more preferably 40% by volume or less. The blending ratio of the solid electrolyte, the active material, and the conductive material is not particularly limited, and may be appropriately adjusted according to the composition of the target active material mixture.

In the second dispersion step S3, the active material and the conductive material may be supplied dry from the powder supply device 10 or may be supplied wet together with a solvent or the like.

As described above, in the manufacturing method S10, when the active material mixture is mixed while the dispersion medium is circulated in the circulation type mixing device 100 provided with the powder mixing pump 40, after the solid electrolyte is dispersed. By dispersing the active material and the conductive material, it is possible to suppress the aggregation of the mixture and reduce the particle size of the mixture. The active material mixture obtained through the production method S10 is in the form of a slurry (or a paste), and can be applied as it is to a coating process for producing an electrode, for example.

1. 1. Configuration of mixing device A mixing device was configured using a jet pacer (registered trademark) manufactured by Nihon Spindle Manufacturing Co., Ltd. in the arrangement shown in FIG.

2. 2. Comparative Example The mixing device was operated, and the solvent (butyl butyrate) and the binder (PVDF) were circulated in the mixing device as a dispersion medium. After that, with the mixing device activated, the solid electrolyte (main component: Li _{2 SP 2} S ₅ , particle size: about 0.2 to 2 μm) and the active material (NCM in the case of a positive electrode) from the powder supply device. In the case of a negative electrode, C, Si or Li ₃ TiO ₄ , particle diameter: about 1 to 5 μm) and a conductive material (VGCF, fiber diameter: about 150 nm, fiber length 3 to 20 μm) are collectively supplied into the dispersion medium. The solid electrolyte, the active material, and the conductive material were dispersed in the dispersion medium to obtain a slurry-like active material mixture (solid content concentration: 37% by volume). The operating time after supplying the solid electrolyte and the like was 20 minutes, and the peripheral speed of the rotor inside the powder mixing pump was set to 36 m / s.

3. 3. Example The mixing device was operated, and the solvent (same as above) and the binder (same as above) were circulated in the mixing device as a dispersion medium. Then, with the mixing device operated, the solid electrolyte (same as above) was supplied from the powder supply device into the dispersion medium, and the first dispersion treatment was performed. Subsequently, with the mixing device operated, the active material (same as above) and the conductive material (same as above) are supplied from the powder supply device into the dispersion medium, and the second dispersion treatment is performed, and the solid electrolyte is added to the dispersion medium. And the active material and the conductive material were dispersed to obtain a slurry-like active material mixture (solid content concentration 39.7% by volume). The operating time after supplying the solid electrolyte was 10 minutes, the operating time after supplying the active material and the conductive material was 10 minutes, and the peripheral speed of the rotor inside the powder mixing pump was 36 m / s.

4. Measurement of particle size of active material mixture For each of the comparative examples and the examples, the particle size of the slurry-like active material mixture was measured by a particle size distribution measuring device (grind gauge) according to JIS K5400-1990 (slurry was stretched, and the slurry was stretched. The number of the part where 4 or more grains or 3 or more streaks were generated was used as the grain gauge value. The scales of the parts that appeared side by side were read. When the values of the two grooves were different, the scale with the larger value was read). The results are shown in FIG. As is clear from the results shown in FIG. 3, in a circulation type mixing device using a powder mixing pump, the solid electrolyte, the active material, and the conductive material are divided and mixed in this order to finally obtain the result. It was found that the ultimate particle size of the grain gauge of the active material mixture was greatly reduced.

The active material mixture produced by the production method of the present disclosure can be suitably used as, for example, a positive electrode mixture or a negative electrode mixture of a sulfide solid-state battery. The sulfide solid-state battery can be widely and suitably used from a small power source for mobile devices to a large power source for mounting on a car.

10 Powder supply device 20 Stirring tank 30 Liquid transfer pump 40 Powder mixing pump 100 Mixing device

Claims (1)

It is provided with a powder supply device, a stirring tank having a stirring device, a liquid feeding pump, and a powder mixing pump capable of sucking powder, feeding liquid, and mixing powder and liquid. A method of manufacturing an active material mixture using a mixing device in which the powder supply device, the stirring tank, the liquid feeding pump, and the powder mixing pump are connected.
A circulation step in which the mixing device is operated to circulate the dispersion medium in the mixing device, and
The first dispersion step of supplying a solid electrolyte from the powder supply device and dispersing it in the dispersion medium while the mixing device is operated.
After the first dispersion step, the active material comprises a second dispersion step of supplying an active material and a conductive material from the powder supply device in a state where the mixing device is operated and dispersing the active material and the conductive material in the dispersion medium. Manufacturing method of material mixture.

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