Method for manufacturing an electrode

Abstract

The manufacturing method of the electrode includes: a mixing step (S01) of mixing materials including an active material, a conductive material, and a thickening agent, which constitute an electrode that can be used in a nonaqueous electrolyte secondary battery, in a dry powder form; a dilution step (S03) of manufacturing a slurry by adding a liquid agent to a mixture obtained in the mixing step; and a forming step (S04) of forming the slurry manufactured in the dilution step into an electrode, in the mixing step, the materials are mixed using a high-speed shearing impact mixer 10 having: a first blade 11 for mixing the materials as a whole; and a second blade 12 for applying a shearing force to the materials.

Description

Technical Field

[0001] This invention relates to a method for manufacturing electrodes used in non-aqueous electrolyte secondary batteries. Background Technology

[0002] In the past, in order to manufacture electrodes for use in non-aqueous electrolyte secondary batteries, a technique was used to create a slurry by adding a liquid agent to a material containing active materials, conductive materials, etc. (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-103391 Summary of the Invention

[0006] In manufacturing the aforementioned slurry, a twin-shaft planetary mixer is sometimes used. The process of adding liquids to materials and manufacturing the slurry using a twin-shaft planetary mixer requires a long processing time, thus necessitating increased productivity.

[0007] The present invention was made in view of the above-described circumstances, and the technical problem to be solved by the present invention is to provide a method for manufacturing an electrode that can shorten the slurry manufacturing time without reducing battery performance compared to the past.

[0008] The means used to solve the above-mentioned technical problems will be explained below.

[0009] The electrode manufacturing method of the present invention is characterized by comprising: a mixing step, wherein materials comprising an active material, a conductive material and a thickener constituting an electrode that can be used in a non-aqueous electrolyte secondary battery are mixed in dry powder form; a dilution step, wherein a liquid agent is added to the mixture obtained in the mixing step to produce a slurry; and a forming step, wherein the slurry produced in the dilution step is formed into the electrode, wherein in the mixing step, the materials are mixed using a high-speed shear-impact mixer having: a first blade for integrally mixing the materials; and a second blade for applying shear force to the materials.

[0010] Furthermore, preferably, during the dilution process, an adhesive is added to the mixture.

[0011] Furthermore, in the electrode manufacturing method, it is preferable that, in the mixing process, the speed of the leading edge of the second blade is set to be more than 5 m / s and less than 40 m / s.

[0012] Furthermore, in the method for manufacturing the electrode, it is preferable to include a high solids content mixing step (solid mixing step), after the mixing step and before the dilution step, adding a solvent to the mixture obtained in the mixing step for mixing, and in the dilution step, adding the liquid agent to the mixture obtained in the high solids content mixing step to manufacture the slurry.

[0013] Furthermore, in the electrode manufacturing method, it is preferable to use a biaxial planetary mixer in the high solids content mixing step and the dilution step.

[0014] The electrode manufacturing method of the present invention can shorten the slurry manufacturing time without reducing battery performance compared with the past. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the electrode manufacturing process.

[0016] Figure 2A This is a schematic cross-sectional view of a high-speed shear-impact mixer.

[0017] Figure 2B This is a schematic cross-sectional view of a high-speed shear-impact mixer.

[0018] Figure 3 This is a schematic cross-sectional view of a twin-shaft planetary mixer.

[0019] Figure 4 This is a graph representing the results of the electrode evaluation test. Detailed Implementation

[0020] [Electrode manufacturing method]

[0021] First, use Figure 1 A method for manufacturing an electrode according to one embodiment of the present invention will be described. This method for manufacturing an electrode can be used when constructing an electrode for a non-aqueous electrolyte secondary battery. Figure 1 As shown, the electrode manufacturing method includes a mixing process (S01), a high-solids-content mixing process (solid refining process) (S02), a dilution process (S03), and a forming process (S04). Each process will be described in turn below.

[0022] In this embodiment, the mixing step (S01) is a step of mixing materials containing active substances, conductive materials, and thickeners in dry powder form. In this step, such as... Figure 2A and Figure 2BAs shown, a high-speed shear-impact mixer 10 is used. The high-speed shear-impact mixer 10 has: a mixing arm as a first blade 11 for mixing the materials as a whole; and a shredding blade as a second blade 12 for applying shear force to the materials.

[0023] like Figure 2A and Figure 2B As shown, the high-speed shear-impact mixer 10 in this embodiment is configured such that three first blades 11 and six second blades 12 can rotate inside a mixing container 10a with a material inlet 10b formed at the top. Figure 2A As shown, the first blade 11 can rotate inside the mixing container 10a by transmitting a driving force from an electric motor (not shown) to the first blade 11 via the first shaft 11a. Similarly, the second blade 12 can rotate inside the mixing container 10a by transmitting a driving force from an electric motor (not shown) to the second blade 12 via the second shaft 12a.

[0024] In the high-speed shear-impact mixer 10 of this embodiment, such as Figure 2B As indicated by arrow R1, the first blade 11 is capable of rotating in the first rotational direction. On the other hand, as... Figure 2B As indicated by arrow R2, the second blade 12 is capable of rotating in the opposite direction to the first rotation direction. In the high-speed shear-impact mixer 10 configured as described above, the first blade 11 can be used to mix the material as a whole, and the second blade 12 can be used to apply shear force to the material.

[0025] The high-speed shear-impact mixer 10 configured as described above is capable of mixing the material as a whole using the first blade 11 while applying shear force to the material using the second blade 12. In the high-speed shear-impact mixer 10, the speed of the leading edge of the second blade 12 is set to be between 5 m / s and 40 m / s.

[0026] Next, in the high solids content mixing step (S02), a solvent is added to the mixture obtained in the mixing step (S01) for further mixing. Then, in the dilution step (S03), a liquid agent is added to the mixture obtained in the high solids content mixing step (S02) to produce a slurry. Finally, in the forming step (S04), the slurry produced in the dilution step (S03) is formed into an electrode.

[0027] In the aforementioned high-solids-content mixing process (S02) and dilution process (S03), such as Figure 3 As shown, a twin-shaft planetary mixer 20 is used. Alternatively, other mixers may be used in these processes.

[0028] like Figure 3As shown, the dual-shaft planetary mixer 20 in this embodiment is configured such that the first stirring section 23a and the second stirring section 23b, which are curved rods, can rotate inside the mixing container 20a. Figure 3 As shown, the first stirring section 23a and the second stirring section 23b are connected to the rotating shaft 21 via a planetary gear mechanism 22. By transmitting driving force from an electric motor (not shown) to the rotating shaft 21, the first stirring section 23a and the second stirring section 23b are each able to rotate on their own axis while revolving around a central axis.

[0029] As described above, in the electrode manufacturing method of this embodiment, dry powder mixing is performed in the mixing step (S01) using a high-speed shear-impact mixer 10 equipped with a second blade 12 capable of applying strong shear force. This allows for the dispersion of materials composed of various powders with particle sizes ranging from a few μm to tens of μm. By dispersing various powders as described above, even if the materials re-aggregate after dispersion, the impact on battery performance can be suppressed.

[0030] As described above, in the electrode manufacturing method of this embodiment, the material composed of various powders can be dispersed using the second blade 12 in the high-speed shear impact mixer 10. Therefore, it is not necessary to disperse the agglomerated powder. By dissolving the solvent and powder, a slurry with less agglomeration can be produced in a short time. Therefore, according to this embodiment, the high solids content mixing step (S02) can be omitted, and the dilution step (S03) can be performed after the mixing step (S01). However, even if the high solids content mixing step is performed, it will not affect the dispersibility. Therefore, when using powders that are difficult to dissolve in the solvent, it is preferable to perform the high solids content mixing step in order to facilitate the dissolution of the solvent and powder.

[0031] Furthermore, in the electrode manufacturing method of this embodiment, the thickener is also mixed during the dry powder mixing process, dispersing the thickener, which is prone to clumping, within the powder that is easily soluble in the solvent. As a result, the thickener does not agglomerate, the contact area between the thickener and the solvent increases, and therefore, the thickener dissolves more quickly. Consequently, the dilution process time can be shortened without affecting battery performance.

[0032] Furthermore, when mixing agglomerated particles with solvent in a twin-shaft planetary mixer 20 as in the past, a high-solids-content mixing process is required, involving the addition of powder and a small amount of solvent. This process disperses the agglomerates by applying shear force (the mixing force in the mixing action of compression, shearing, stretching, etc.) to the raw materials. In this case, the shear force during mixing only acts near the blades and container, thus requiring a long processing time.

[0033] Furthermore, as the processing equipment becomes larger, the proportion of blades that can be close to the container and apply shear force decreases relative to the amount of powder fed into the container (the amount of powder increases with the cube of the container diameter, while the length of the blades is only a multiple of the container diameter, thus reducing the proportion of shear force that can be applied). Additionally, as the container becomes larger, the gap between the blades and the container needs to be widened to prevent contact, thus reducing the shear force that can be applied. Therefore, as the equipment becomes larger, the slurry preparation time further increases, and productivity decreases.

[0034] Furthermore, thickeners dissolve starting from the portion in contact with the liquid. Therefore, when the thickener clumps together, a high-viscosity film forms at the point of contact with the liquid, creating a so-called "clump" that the liquid cannot penetrate, making dissolution difficult. The high-viscosity film on the surface of the clump gradually thins and dissolves; thus, the overall dissolution of the thickener takes a considerable amount of time.

[0035] [Materials constituting the electrodes and paste]

[0036] The electrode in this embodiment is composed of at least an active substance, a conductive material, a thickener, a binder, and a current collector.

[0037] There are no particular limitations on the active material, as long as it can be used in non-aqueous electrolyte secondary batteries. That is, any inorganic material that can undergo oxidation-reduction during charge-discharge processes is acceptable. For example, when used as the positive electrode, examples include LiCoO2, LiNiO2, Li(Ni-Co-Mn)O2, LiMn2O4, LiFePO4, LiMnPO4, and sulfur-modified materials. When used as the negative electrode, examples include graphite, hard carbon, soft carbon, and Li4Ti5O4. 12 Sn, SnO, SnS, Ge, Si, SiO, etc. can be used individually or in combination with two or more.

[0038] The active material can be spherical, granular, elliptical, fibrous, or plate-like, but spherical is preferred because it allows for minimal viscosity change during storage and facilitates densification of the coated layer through pressing. The particle size of the active material is preferably a powder between 0.01 μm and 100 μm.

[0039] There are no particular limitations on conductive materials, as long as they can be used in non-aqueous electrolyte secondary batteries. That is, any carbon powder with electronic conductivity is acceptable. Examples include acetylene black, furnace black, graphite, hollow carbon, carbon fiber, carbon nanotubes, and graphene.

[0040] There are no particular limitations on thickeners, as long as they are materials that can be used in non-aqueous electrolyte secondary batteries. That is, any resin that can increase the viscosity of the slurry is acceptable. Examples include carboxymethyl cellulose, hydroxypropyl cellulose, and xanthan gum.

[0041] There are no particular limitations on the adhesive, as long as it is a material that can be used in non-aqueous electrolyte secondary batteries. That is, any resin capable of bonding the active material, conductive material, and current collector can be used. Examples include styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, and polyamide-imide.

[0042] In this invention, the adhesive described above may also be a solid such as a powder, but for the sake of the excellent homogeneity of the slurry, it is preferred to use it in the form of a solution or emulsion.

[0043] There are no particular restrictions on the material of the current collector, as long as it can be used in a non-aqueous electrolyte secondary battery. That is, any metal that has electronic conductivity and does not react during charging and discharging is acceptable. Examples include copper, aluminum, nickel, iron, titanium, and carbon. There are no particular restrictions on the shape of the current collector; for example, foil, plate, fiber, mesh, and porous materials can be used.

[0044] The electrode of this embodiment can be manufactured by vaporizing and removing the liquid component contained in the slurry. For example, by coating a slurry consisting of an active substance, a conductive material, a thickener, a binder, and a liquid component onto a current collector and heating it at 50°C or higher, the liquid component in the slurry can be vaporized and removed. Thus, an electrode with a structure in which a mixture consisting of an active substance, a conductive material, a thickener, and a binder is disposed on the current collector can be obtained.

[0045] Here, slurry refers to a fluid obtained by dispersing or dissolving active substances, conductive materials, thickeners, and binders in a liquid. That is, liquid refers to a fluid that has the property of dispersing or dissolving solids such as active substances, conductive materials, thickeners, and binders, and can be removed by vaporization upon heating.

[0046] Examples of liquids used in the dilution process and solvents used in the high-solids-content mixing process include water, N-methyl-2-pyrrolidone, alcohols, and ketones. The liquid used in the dilution process and the solvent used in the high-solids-content mixing process can be the same liquid or different liquids.

[0047] [Non-aqueous electrolyte secondary battery]

[0048] The electrode of this embodiment can be used as an electrode in a non-aqueous electrolyte secondary battery.

[0049] Here, a non-aqueous electrolyte secondary battery refers to a battery that can be charged and discharged using an electrolyte whose composition does not contain water. Examples include lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, and calcium-ion batteries.

[0050] A non-aqueous electrolyte secondary battery consists of at least three components: a positive electrode, a negative electrode, and an electrolyte. Additionally, if the electrolyte is fluid, a separator is required between the positive and negative electrodes.

[0051] There are no particular limitations on the electrolyte, as long as it is a material that can be used in non-aqueous electrolyte secondary batteries. That is, it only needs to have ionic conductivity. Examples include electrolytes, gel electrolytes, ionic liquids, and solid electrolytes.

[0052] There are no particular limitations on the materials used in the separator, as long as they can be used in non-aqueous electrolyte secondary batteries. That is, any membrane made of a material that does not have electronic conductivity and has numerous through-pores is acceptable.

[0053] The electrode in this embodiment can be used as a positive electrode and / or a negative electrode.

[0054] [Evaluation Test]

[0055] The applicant of this application conducted evaluation tests using an electrode manufactured using the electrode manufacturing method of this embodiment (hereinafter referred to as the "electrode of this application") and an electrode manufactured using the electrode manufacturing method of the prior art (hereinafter referred to as the "comparative electrode"). The method and results of the evaluation tests will be described below.

[0056] In manufacturing the electrode of this application, the material comprising an active material, a conductive material, and a thickener for manufacturing the electrode of a non-aqueous electrolyte secondary battery was mixed in a high-speed shear-impact mixer 10 (mixing step S01). In this experiment, graphite was used as the active material, acetylene black as the conductive material, and carboxymethyl cellulose as the thickener. Furthermore, in the high-speed shear-impact mixer 10, mixing was performed for 5 minutes under the conditions that the rotational speed of the mixing arm, which serves as the first blade 11 for mixing the whole assembly, was 27 rpm, and the rotational speed of the chopping blade, which serves as the second blade 12 for applying strong shear force, was 2200 rpm.

[0057] Next, the powder mixed in the high-speed shear impact mixer 10 and the styrene-butadiene rubber as a binder are added to the twin-shaft planetary mixer 20, and 150g of water as a liquid agent is added. The twin-shaft planetary mixer 20 is then run at 100 rpm for 5 minutes to produce a slurry (dilution step S03). Furthermore, the slurry produced using the above method is used to form a negative electrode (the electrode of this application) (forming step S04). As described above, the time spent producing the slurry used in the electrode of this application is 5 minutes in the high-speed shear impact mixer 10 and 5 minutes in the twin-shaft planetary mixer 20, totaling 10 minutes.

[0058] In manufacturing the comparative electrode, similarly to the electrode of this application, a material comprising an active substance, a conductive material, a thickener, and a binder is added to a biaxial planetary mixer 20, and 80g of water is added as a liquid agent. The biaxial planetary mixer 20 is then run at 100 rpm for 100 minutes. Afterward, the remaining 70g of water is added to the biaxial planetary mixer 20, and the biaxial planetary mixer 20 is run at 100 rpm for 30 minutes to produce a slurry. As described above, the time spent manufacturing the slurry used in the comparative electrode is 130 minutes in the biaxial planetary mixer 20.

[0059] Furthermore, button cells were manufactured using the electrodes or comparative electrodes, current collector, counter electrode, separator, and electrolyte of this application. The current collector used a 10μm thick copper foil, the counter electrode used a 500μm thick lithium metal, the separator used a 16mm diameter glass filter membrane (GA-100) or a PP / PE / PP microporous membrane (25μm thick), the electrolyte used was 1M LiPF6 / EC:DEC (=50:50 vol.%), the battery casing used an R2032 type button cell, and the heat treatment conditions were vacuum, 120 degrees Celsius, and 12 hours.

[0060] Batteries manufactured using individual electrodes were evaluated through cycle testing. The cycle testing was conducted at an ambient temperature of 30 degrees Celsius, a cutoff voltage of 0.001V–1.0V, and a current rate of 0.1C.

[0061] The results of the cyclic testing (100 cycles) showed that both the electrode of this application and the comparative electrode achieved battery performance with discharge capacity equivalent to 100% (refer to...). Figure 4 In other words, the results of battery performance evaluation using electrodes manufactured using both methods showed no difference in battery performance. Therefore, it can be confirmed that the electrode of this application, compared to the comparative electrode manufactured using conventionally implemented standard manufacturing methods, can significantly shorten manufacturing time without degrading battery performance.

[0062] Industrial availability

[0063] The electrode manufacturing method of the present invention is useful because it can shorten the slurry manufacturing time without reducing battery performance compared to the conventional method.

[0064] Explanation of reference numerals in the attached figures

[0065] 10 High-speed shear impact mixer, 10a Mixing container, 10b Inlet, 11 First blade, 11a First shaft, 12 Second blade, 12a Second shaft, 20 Dual-shaft planetary mixer, 20a Mixing container, 21 Rotating shaft, 22 Planetary gear mechanism, 23a First stirring section, 23b Second stirring section, S01 Mixing process, S02 High solids content mixing process, S03 Dilution process, S04 Forming process, R1 First rotation direction, R2 Second rotation direction.

Claims

1. A method for manufacturing an electrode, characterized in that, include: The mixing process involves mixing materials containing active substances, conductive materials, and thickeners that form electrodes that can be used in non-aqueous electrolyte secondary batteries in dry powder form. The dilution process involves adding a liquid agent to the mixture obtained in the mixing process to produce a slurry; and The forming process involves shaping the slurry produced in the dilution process into the electrode. In the mixing process, the materials are mixed using a high-speed shear-impact mixer, which has: a first blade for mixing the materials integrally; and a second blade for applying shear force to the materials.

2. The method for manufacturing the electrode according to claim 1, characterized in that: In the dilution process, an adhesive is added to the mixture.

3. The method for manufacturing the electrode according to claim 2, characterized in that: In the mixing process, the speed of the leading edge of the second blade is set to be between 5 m / s and 40 m / s.

4. The method for manufacturing the electrode according to any one of claims 1 to 3, characterized in that: This includes a high-solids-content mixing process, in which, after the mixing process and before the dilution process, a solvent is added to the mixture obtained in the mixing process for further mixing. In the dilution step, the liquid agent is added to the mixture obtained in the high solids content mixing step to produce the slurry.

5. The method for manufacturing the electrode according to claim 4, characterized in that: In the high solids content mixing process and the dilution process, a twin-shaft planetary mixer is used.

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