Electrode manufacturing method

Abstract

Provided is a method for producing an electrode, which can shorten the production time of a slurry without deteriorating battery performance as compared with the conventional method. [Solution] The method for manufacturing an electrode includes a mixing step (S01) of mixing materials containing an active material, a conductive material, and a thickener, which constitute an electrode for use in a non-aqueous electrolyte secondary battery, in the form of dry powder; a dilution step (S03) of adding a liquid agent to the mixture mixed in the mixing step to produce a slurry; and a formation step (S04) of forming the slurry produced in the dilution step into an electrode. In the mixing step, the materials are mixed using a high-speed shear impact mixer 10 having a first blade 11 that mixes the materials overall and a second blade 12 that applies a shear force to the materials.

Description

[Technical field]

[0001] The present invention relates to a method for producing an electrode for use in a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Conventionally, in order to manufacture electrodes for use in non-aqueous electrolyte secondary batteries, a technique has been adopted in which a liquid agent is added to materials containing an active material, a conductive material, and the like to manufacture a slurry (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-103391 A Summary of the Invention [Problem to be solved by the invention]

[0004] When producing the above-mentioned slurry, a two-shaft planetary agitation mixer may be used. When adding a liquid agent to a material and producing a slurry with a two-shaft planetary agitation mixer, it is necessary to process the material for a long time, so there was a demand for improving productivity.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and the problem that the present invention aims to solve is to provide a method for producing an electrode that can shorten the production time of a slurry without deteriorating battery performance compared to conventional methods. [Means for solving the problem]

[0006] Means for solving the above problems will be described below.

[0007] The method for producing an electrode according to the present invention includes a mixing step of mixing materials containing an active material, a conductive material, and a thickener, which constitute an electrode for use in a non-aqueous electrolyte secondary battery, in the form of dry powder; a dilution step of adding a liquid agent to the mixture mixed in the mixing step to produce a slurry; and a formation step of forming the slurry produced in the dilution step into the electrode, in which the materials are mixed in the mixing step using a high-speed shear impact mixer having a first blade that mixes the materials overall and a second blade that applies a shear force to the materials.

[0008] In the dilution step, it is preferable to add a binder to the mixture.

[0009] In the electrode manufacturing method, it is preferable that in the mixing step, the speed of the tip of the second blade is set to 5 m / sec or more and 40 m / sec or less.

[0010] In addition, in the method for manufacturing an electrode, it is preferable to provide a kneading step, after the mixing step and before the dilution step, in which a solvent is added to the mixture mixed in the mixing step and kneaded, and in the dilution step, the liquid is added to the mixture kneaded in the kneading step to produce the slurry.

[0011] In the method for producing an electrode, it is preferable to use a two-shaft planetary agitation mixer in the kneading step and the dilution step. Effect of the Invention

[0012] According to the method for producing an electrode of the present invention, it is possible to reduce the production time of the slurry without deteriorating the battery performance, as compared with the conventional method. [Brief description of the drawings]

[0013] [Figure 1] FIG. 4 is a flow diagram showing a method for manufacturing an electrode. [Diagram 2] 1(a) and 1(b) are schematic cross-sectional views showing a high-speed shear impact mixer. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a two-shaft planetary agitation mixer. [Figure 4] FIG. 13 is a diagram showing the results of an evaluation test of an electrode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Electrode manufacturing method] First, a method for producing an electrode according to one embodiment of the present invention will be described with reference to Fig. 1. The method for producing an electrode according to this embodiment is used when constructing an electrode for a non-aqueous electrolyte secondary battery. As shown in Fig. 1, the method for producing an electrode includes a mixing step (S01), a kneading step (S02), a dilution step (S03), and a forming step (S04). Each step will be described in order below.

[0015] In this embodiment, the mixing step (S01) is a step of mixing materials including an active material, a conductive material, and a thickener in dry powder form. In this step, a high-speed shear impact mixer 10 is used, as shown in Figures 2(a) and (b). The high-speed shear impact mixer 10 has a mixing arm, which is a first blade 11 that mixes the materials overall, and a chopper blade, which is a second blade 12 that applies a shear force to the materials.

[0016] As shown in Figures 2(a) and (b), the high-speed shear impact mixer 10 in this embodiment is configured to rotate three first blades 11 and six second blades 12 inside a mixing vessel 10a with a material inlet 10b formed at the top. As shown in Figure 2(a), the first blade 11 rotates inside the mixing vessel 10a by the driving force of a motor (not shown) being transmitted through a first shaft 11a. Similarly, the second blade 12 rotates inside the mixing vessel 10a by the driving force of a motor (not shown) being transmitted through a second shaft 12a.

[0017] In the high-speed shear impact mixer 10 of this embodiment, the first blade 11 is configured to rotate in a first rotation direction, as shown by the arrow R1 in Fig. 2(b). On the other hand, the second blade 12 is configured to rotate in a direction opposite to the first rotation direction, as shown by the arrow R2 in Fig. 2(b). In the high-speed shear impact mixer 10 configured in this manner, the first blade 11 mixes the materials overall, and the second blade 12 applies a shear force to the materials.

[0018] The high-speed shear impact mixer 10 configured as described above mixes the materials thoroughly with the first blade 11 while applying a shear force to the materials with the second blade 12. In the high-speed shear impact mixer 10, the speed of the blade tip of the second blade 12 is set to 5 m / s or more and 40 m / s or less.

[0019] Next, in the kneading step (S02), a solvent is added to the mixture mixed in the mixing step (S01) and kneaded. After that, in the dilution step (S03), a liquid is added to the mixture kneaded in the kneading step (S02) to produce a slurry. Next, in the formation step (S04), the slurry produced in the dilution step (S03) is formed into an electrode.

[0020] In the above-mentioned kneading step (S02) and dilution step (S03), a two-shaft planetary agitation mixer 20 is used as shown in Fig. 3. Note that it is also possible to use other mixers in these steps.

[0021] As shown in Fig. 3, the two-shaft planetary stirring mixer 20 in this embodiment is configured such that a first stirring section 23a and a second stirring section 23b, which are bent rods, rotate inside a mixing vessel 20a. As shown in Fig. 3, the first stirring section 23a and the second stirring section 23b are connected to a rotating shaft 21 via a planetary gear mechanism 22. When a driving force from a motor (not shown) is transmitted to the rotating shaft 21, the first stirring section 23a and the second stirring section 23b are configured to revolve while rotating on their own axes.

[0022] As described above, according to the manufacturing method of the electrode of this embodiment, in the mixing step (S01), dry powder mixing is performed using a high-speed shear impact mixer 10 having a second blade 12 capable of applying a strong shear force, and this makes it possible to disperse a material consisting of multiple powders with fine particle sizes of several μm to several tens of μm. By dispersing multiple powders in this way, even if the material re-aggregates after dispersion, the effect on the performance of the battery can be suppressed.

[0023] As described above, in the manufacturing method of the electrode according to this embodiment, since the material consisting of a plurality of powders can be dispersed using the second blade 12 in the high-speed shear impact mixer 10, it is not necessary to disperse the agglomerated powder, and a slurry with less agglomeration can be produced in a short time by blending the powder with the solvent. Therefore, according to this embodiment, it is also possible to omit the kneading step (S02) and perform the dilution step (S03) after the mixing step (S01). However, since the kneading step does not affect the dispersibility, when using a powder that is not easily blended with the solvent, it is preferable to perform the kneading step to make the powder more easily blended with the solvent.

[0024] In addition, in the manufacturing method of the electrode according to the present embodiment, a thickener is mixed together with the dry powder when mixing, and the thickener, which tends to form lumps, is dispersed in a powder that is compatible with the solvent. This prevents the thickener from agglomerating, increases the contact area between the thickener and the solvent, and the thickener dissolves faster. As a result, the time for the dilution process can be shortened without affecting the battery performance.

[0025] When kneading particles that remain aggregated with a solvent in a two-shaft planetary agitation mixer 20 as in the past, it is necessary to add powder and a small amount of solvent and perform a kneading process to break up the aggregates and disperse them by applying shear (mixing force in kneading action such as compression, shear, and stretching) to the raw material. In this case, the shear in the kneading only works in the part where the blade and the container come close to each other, so it is necessary to process for a long time.

[0026] In addition, as the processing equipment becomes larger, the blades and container get closer to each other relative to the amount of powder put into the container, and the ratio of the shear that can be applied decreases (the amount of powder increases as the cube of the container diameter, but the length of the blades is only times the container diameter, so the ratio of the shear that can be applied decreases). Furthermore, as the container becomes larger, it is necessary to widen the gap between the blades and the container so that they do not come into contact, and the shear that can be applied decreases. Therefore, as the equipment becomes larger, the time required to produce the slurry becomes even longer, and productivity decreases.

[0027] In addition, since the thickener starts to dissolve from the part that comes into contact with the liquid, if the thickener aggregates, a high-viscosity film is formed where the liquid comes into contact, preventing the liquid from penetrating into the interior, creating a state known as "lumps," making it difficult to dissolve. Since the high-viscosity film on the surface of the lumps gradually thins out as they dissolve, it takes a long time for the entire thickener to dissolve.

[0028] [Electrode and slurry constituent materials] The electrode according to this embodiment is composed of at least an active material, a conductive material, a thickener, a binder, and a current collector.

[0029] The active material is not particularly limited as long as it is a material that can be used in non-aqueous electrolyte secondary batteries. In other words, it is sufficient if it is an inorganic material that can undergo oxidation and reduction by charging and discharging. For example, in the case of a positive electrode, LiCoO 2 , LiNiO 2 , Li(Ni-Co-Mn)O 2 , LiMn 2 O 4 , LiFePO 4 , LiMnPO 4 , sulfur modified materials, etc. For the negative electrode, graphite, hard carbon, soft carbon, Li 4 Ti 5 O 12 , Sn, SnO, SnS, Ge, Si, SiO, etc., and one type may be used alone, or two or more types may be used in combination. The shape of the active material may be spherical, granular, elliptical, fibrous, or plate-like, but spherical is preferred because the viscosity change during storage of the slurry is small and the mixture layer after application is easy to densify by pressing. The particle size of the active material is preferably 0.01 μm or more and 100 μm or less.

[0030] The conductive material is not particularly limited as long as it is a material used in non-aqueous electrolyte secondary batteries. That is, it may be a carbon powder having electronic conductivity. Examples of the conductive material include acetylene black, furnace black, graphite, hollow carbon, carbon fiber, carbon nanotubes, and graphene.

[0031] The thickener is not particularly limited as long as it is a material used in non-aqueous electrolyte secondary batteries. That is, it is sufficient if it is a resin that can increase the viscosity of the slurry. Examples of the thickener include carboxymethyl cellulose, hydroxypropyl cellulose, and xanthan gum.

[0032] The binder is not particularly limited as long as it is a material used in non-aqueous electrolyte secondary batteries. That is, it may be a resin capable of binding the active material, the conductive material, and the current collector. Examples of the binder include styrene-butadiene rubber, polyacrylic, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, and polyamide-imide. In the present disclosure, the binder may be used as a solid such as a powder, but is preferably used in the form of a solution or emulsion because this provides excellent homogeneity to the slurry.

[0033] The current collector is not particularly limited as long as it is a material used in non-aqueous electrolyte secondary batteries. That is, it is sufficient if it is a metal that has electronic conductivity and does not react during charging and discharging. Examples of the current collector include copper, aluminum, nickel, iron, titanium, and carbon. There is no particular restriction on the shape of the current collector, but for example, a foil, plate, fiber, mesh, or porous body can be used.

[0034] The electrode according to this embodiment is manufactured by vaporizing and removing the liquid agent contained in the slurry. For example, a slurry composed of an active material, a conductive material, a thickener, a binder, and a liquid agent is applied onto a current collector, and the liquid agent in the slurry can be vaporized and removed by heating at 50° C. or higher. This makes it possible to obtain an electrode having a structure in which a composite material composed of an active material, a conductive material, a thickener, and a binder is provided on a current collector.

[0035] Here, the term "slurry" refers to a fluid in which an active material, a conductive material, a thickener, and a binder are dispersed or dissolved in a liquid. In other words, the liquid agent refers to a fluid that has the property of dispersing or dissolving solids such as an active material, a conductive material, a thickener, and a binder, and can be vaporized and removed by heating.

[0036] Examples of the liquid used in the dilution step and the solvent used in the kneading step include water, N-methyl-2-pyrrolidone, alcohols, ketones, etc. The liquid used in the dilution step and the solvent used in the kneading step may be the same or different liquids.

[0037] [Nonaqueous electrolyte secondary battery] The electrode according to this embodiment can be used as an electrode for a non-aqueous electrolyte secondary battery. Here, the non-aqueous electrolyte secondary battery refers to a chargeable and dischargeable battery that uses an electrolyte that does not contain water, such as a lithium ion battery, a sodium ion battery, a potassium ion battery, a magnesium ion battery, or a calcium ion battery.

[0038] A non-aqueous electrolyte secondary battery is composed of at least three components: a positive electrode, a negative electrode, and an electrolyte. If the electrolyte has fluidity, a separator is also required between the positive electrode and the negative electrode.

[0039] The electrolyte is not particularly limited as long as it is a material used in non-aqueous electrolyte secondary batteries. In other words, it is sufficient if it has ion conductivity. Examples of the electrolyte include an electrolytic solution, a gel electrolytic solution, an ionic liquid, and a solid electrolyte.

[0040] The separator is not particularly limited as long as it is made of a material that can be used in non-aqueous electrolyte secondary batteries, that is, it may be a film made of a material that does not have electronic conductivity and has a large number of through holes.

[0041] The electrode according to this embodiment can be used as a positive electrode and / or a negative electrode.

[0042] [Evaluation test] The applicant of the present application conducted an evaluation test using an electrode manufactured by the manufacturing method of an electrode according to the present embodiment (hereinafter referred to as the "electrode of the present application") and an electrode manufactured by the manufacturing method of an electrode according to the prior art (hereinafter referred to as the "comparative electrode"). The method and results of the evaluation test are described below.

[0043] When manufacturing the electrode of the present invention, materials including an active material, a conductive material, and a thickener for manufacturing an electrode of a non-aqueous electrolyte secondary battery were mixed in a high-speed shear impact mixer 10 (mixing step S01). In this test, graphite was used as the active material, acetylene black as the conductive material, and carboxymethyl cellulose as the thickener. In addition, in the high-speed shear impact mixer 10, mixing was performed for 5 minutes at a rotation speed of 27 rpm by the mixing arm, which is the first blade 11 that mixes the entire mixture, and a rotation speed of 2200 rpm by the chopper blade, which is the second blade 12 that applies a strong shear force.

[0044] Thereafter, the powder mixed in the high-speed shear impact mixer 10 and styrene-butadiene rubber as a binder were charged into the biaxial planetary agitation mixer 20, 150 g of water as a liquid was added, and the biaxial planetary agitation mixer 20 was operated at 100 rpm for 5 minutes to produce a slurry (dilution step S03). Furthermore, a negative electrode (the present electrode) was formed using the slurry produced by the above method (formation step S04). As described above, the time required to produce the slurry used for the present electrode was 10 minutes in total, consisting of 5 minutes in the high-speed shear impact mixer 10 and 5 minutes in the biaxial planetary agitation mixer 20.

[0045] When producing the comparative electrode, materials including an active material, a conductive material, a thickener, and a binder were charged into the biaxial planetary stirring mixer 20 in the same manner as in the electrode of the present application, and 80 g of water as a liquid agent was added, and the biaxial planetary stirring mixer 20 was operated at 100 rpm for 100 minutes. Thereafter, the remaining 70 g of water was charged into the biaxial planetary stirring mixer 20, and the biaxial planetary stirring mixer 20 was operated at 100 rpm for 30 minutes to produce a slurry. As described above, the time required to produce the slurry used in the comparative electrode was 130 minutes in the biaxial planetary stirring mixer 20.

[0046] Coin cells were also produced using the present electrode or comparative electrode, current collector, counter electrode, separator, and electrolyte. The current collector was a 10 μm thick copper foil, the counter electrode was a 500 μm thick lithium metal, the separator was a 16 mm diameter glass filter (GA-100), and the electrolyte was 1M LiPF 6 The battery was an R2032 type coin cell, and the heat treatment conditions were vacuum, 120 degrees, and 12 hours.

[0047] The batteries manufactured using each electrode were evaluated by a cycle test. In the cycle test, the environmental temperature was 30 degrees, the cutoff voltage was 0.001V-1.0V, and the current value was 0.1C-rate.

[0048] As a result of cycle testing (100 cycles), both the electrode of the present invention and the comparative electrode exhibited the same battery performance, with a discharge capacity of 100% (see FIG. 4). In other words, as a result of evaluating the battery performance using the electrodes manufactured by both manufacturing methods, no difference in battery performance was observed. Thus, it was confirmed that the electrode of the present invention can drastically reduce the manufacturing time without deteriorating the battery performance, compared to the comparative electrode manufactured by the generally used standard manufacturing method. [Explanation of symbols]

[0049] 10 High-speed shear impact mixer 10a Mixing container 10b Inlet 11 First wing 11a First shaft 12 Second wing 12a Second shaft 20. Two-shaft planetary agitator mixer 20a mixing vessel 21 rotating shaft 22 Planetary gear mechanism 23a First stirring section 23b Second mixing section S01 Mixing process S02 Hardening process S03 Dilution process S04 Formation process R1 First rotation direction R2 Second rotation direction

Claims

1. A mixing step of mixing materials including an active material, a conductive material, and a thickener, which constitute an electrode for use in a nonaqueous electrolyte secondary battery, in the form of dry powder; A dilution step of adding a liquid agent to the mixture mixed in the mixing step to produce a slurry; A method for manufacturing an electrode, comprising: a forming step of forming the slurry produced in the dilution step into the electrode, In the mixing step, the materials are mixed using a high-speed shear impact mixer having a first blade that mixes the materials thoroughly and a second blade that applies a shear force to the materials.

2. The method for producing an electrode according to claim 1 , wherein a binder is added to the mixture in the dilution step.

3. The method for manufacturing an electrode according to claim 2 , wherein in the mixing step, a speed of the tip of the second blade is set to 5 m / sec or more and 40 m / sec or less.

4. A kneading step is provided after the mixing step and before the dilution step, in which a solvent is added to the mixture mixed in the mixing step and kneaded; The method for producing an electrode according to claim 1 , wherein in the dilution step, the liquid is added to the mixture obtained in the thickening step to produce the slurry.

5. The method for producing an electrode according to claim 4 , wherein a two-shaft planetary agitation mixer is used in the kneading step and the dilution step.

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