Manufacturing method of electrode

Abstract

To provide a manufacturing method of an electrode, capable of reducing a manufacturing time of a slurry without deteriorating a battery performance as compared with conventional ones.SOLUTION: A manufacturing method of an electrode, comprises: a mixing step (S01) of mixing a material containing an active material, a conductive material, and a viscosity improver, which constitutes an electrode used for a non-aqueous electrolyte secondary with a dry powder; a dilution step (S03) of manufacturing a slurry by adding a liquid agent to a mixture mixed in the mixing step; and a formation step (S04) of forming the slurry manufactured in the dilution step to the electrode. In the mixing step, the material is mixed by using a high-speed shearing force impact type mixing machine 10 including a first blade 11 into which the material is fully mixed and a second blade 12 for adding a shearing force to the material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrode used in a non-aqueous electrolyte secondary battery.

Background Art

[0002] Conventionally, in order to manufacture an electrode used in a non-aqueous electrolyte secondary battery, a technique of adding a liquid agent to a material containing an active material, a conductive material, etc. to produce a slurry has been adopted (see, for example, Patent Document 1).

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When manufacturing the above slurry, a biaxial planetary stirring type mixer may be used. When adding a liquid agent to the material and manufacturing the slurry with a biaxial planetary stirring type mixer, it is necessary to perform the treatment for a long time, so an improvement in productivity has been demanded.

[0005] The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is to provide a method for manufacturing an electrode that can shorten the manufacturing time of the slurry without degrading the battery performance as compared with the conventional method.

Means for Solving the Problems

[0006] Hereinafter, means for solving the above problems will be described.

[0007] The method for manufacturing an electrode according to the present invention includes a mixing step of mixing, in dry powder form, a material containing an active material, a conductive material, and a thickener that constitutes an electrode used in a non-aqueous electrolyte secondary battery, a dilution step of adding a liquid agent to the mixture mixed in the mixing step to produce a slurry, and a forming step of forming the slurry produced in the dilution step on the electrode. In the mixing step, the material is mixed using a high-speed shear impact mixer having a first blade for mixing the material as a whole and a second blade for applying a shearing force to the material.

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

[0009] Also, in the method for manufacturing an electrode, in the mixing step, it is preferable that the speed of the tip of the second blade is set to be 5 m / s or more and 40 m / s or less per second.

[0010] Also, in the method for manufacturing an electrode, after the mixing step and before the dilution step, a kneading step of adding a solvent to the mixture mixed in the mixing step and kneading is provided, and in the dilution step, it is preferable to add the liquid agent to the kneaded product kneaded in the kneading step to produce the slurry.

[0011] Also, in the method for manufacturing an electrode, it is preferable to use a twin-shaft planetary stirring mixer in the kneading step and the dilution step.

Effects of the Invention

[0012] According to the method for manufacturing an electrode of the present invention, the manufacturing time of the slurry can be shortened without degrading the battery performance as compared with the conventional method.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

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

[0015] In this embodiment, the mixing step (S01) is a step of mixing a material containing an active material, a conductive material, and a thickener in dry powder form. In this step, as shown in FIGS. 2(a) and (b), a high-speed shear impact type mixer 10 is used. The high-speed shear impact type mixer 10 has a mixing arm which is a first blade 11 for mixing the material as a whole, and a chopper blade which is a second blade 12 for applying a shearing force to the material.

[0016] As shown in FIGS. 2(a) and (b), in the high-speed shear impact type mixer 10 in this embodiment, inside a mixing container 10a having a material inlet 10b formed at the upper part, three first blades 11 and six second blades 12 are configured to rotate. As shown in FIG. 2(a), the first blade 11 rotates inside the mixing container 10a when the driving force of a motor (not shown) is transmitted through a first shaft 11a. Similarly, the second blade 12 rotates inside the mixing container 10a when the driving force of a motor (not shown) is transmitted through a second shaft 12a.

[0017] In the high-speed shear impact mixer 10 according to the present embodiment, as shown by the arrow R1 in FIG. 2(b), the first blade 11 is configured to rotate in the first rotation direction. On the other hand, as shown by the arrow R2 in FIG. 2(b), the second blade 12 is configured to rotate in a direction opposite to the first rotation direction. In the high-speed shear impact mixer 10 configured as described above, the material is globally mixed by the first blade 11, and a shearing force is applied to the material by the second blade 12.

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

[0019] Next, in the kneading step (S02), a solvent is added to the mixture mixed in the mixing step (S01) and kneaded. Then, in the dilution step (S03), a liquid agent is added to the kneaded product kneaded in the kneading step (S02) to produce a slurry. Next, in the forming step (S04), the slurry produced in the dilution step (S03) is formed on the electrode.

[0020] In the above-described kneading step (S02) and dilution step (S03), as shown in FIG. 3, a twin-shaft planetary stirring mixer 20 is used. It should be noted that it is also possible to use other mixers in these steps.

[0021] As shown in FIG. 3, in the twin-shaft planetary stirring mixer 20 according to the present embodiment, inside the mixing container 20a, a first stirring part 23a and a second stirring part 23b, which are bent rods, are configured to rotate. As shown in FIG. 3, the first stirring part 23a and the second stirring part 23b are connected to the 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 part 23a and the second stirring part 23b are each configured to revolve while rotating on their own axes.

[0022] As described above, according to the method for manufacturing an electrode according to the present embodiment, in the mixing step (S01), dry powder mixing is performed using the high-speed shear impact mixer 10 having the second blade 12 capable of applying a strong shearing force. As a result, it is possible to disperse a material composed of a plurality of powders having a fine particle size of several μm to several tens of μm. By dispersing a plurality of powders in this way, even if the material aggregates again after being dispersed, the influence on the performance of the battery can be suppressed.

[0023] As described above, in the method for manufacturing an electrode according to the present embodiment, since the material composed 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 aggregated powders, and a slurry with less aggregation can be manufactured in a short time by making the solvent and the powders compatible. Therefore, according to the present embodiment, it is also possible to omit the kneading step (S02) and perform the dilution step (S03) after the mixing step (S01). However, since performing the kneading step does not affect the dispersibility, when using powders that are difficult to be compatible with the solvent, it is preferable to perform the kneading step in order to make the solvent and the powders easily compatible.

[0024] Further, in the method for manufacturing an electrode according to the present embodiment, a thickener is also mixed together during dry powder mixing, and the thickener that easily forms lumps is dispersed in a solvent and a powder that is easily compatible with the solvent. As a result, the aggregation of the thickener disappears, and the contact area between the thickener and the solvent increases, so that the dissolution of the thickener is accelerated. As a result, the time of the dilution step can be shortened without affecting the battery performance.

[0025] In addition, when kneading the conventionally aggregated particles together with a solvent using a biaxial planetary stirring mixer 20, it is necessary to apply a share (kneading force in kneading actions such as compression, shear, and stretching) to the raw materials by performing a kneading step with the powder and a small amount of solvent to crush the aggregation and perform dispersion. In this case, since the share in kneading acts only in a part where the blade and the container approach each other, it is necessary to perform the treatment for a long time.

[0026] In addition, when the size of the processing device increases, the ratio at which the blades approach the container and share the powder amount input into the container decreases (since the powder amount increases by the cube of the container diameter, while the blade length can only be doubled the container diameter, the sharing ratio decreases). Furthermore, when 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, resulting in a decrease in the shared ratio. Therefore, as the device size increases, the slurry production time becomes even longer and productivity decreases.

[0027] In addition, since the thickener starts to dissolve from the part in contact with the liquid agent, if the thickener is aggregated, a high-viscosity film forms at the part where the liquid agent touches, and the liquid cannot penetrate inside, resulting in a state called "lump" where dissolution is difficult to proceed. Since the high-viscosity film on the surface of the lump gradually thins and dissolves, it takes a long time for the entire thickener to dissolve.

[0028] [Constituent Materials of Electrodes and Slurry] 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 used in a non-aqueous electrolyte secondary battery. That is, it may be an inorganic material capable of undergoing oxidation-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 bodies, etc. may be mentioned. In the case of a negative electrode, graphite, hard carbon, soft carbon, Li 4 Ti 5 O 12 , Sn, SnO, SnS, Ge, Si, SiO, etc. may be mentioned, and they may be used alone or in combination of two or more. The shape of the active material may be spherical, granular, elliptical, fibrous, or plate-like, but it is preferably spherical because the viscosity change during storage of the slurry is small and the composite layer after coating can be easily densified by pressing. The particle diameter of the active material is preferably a powder of 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 a non-aqueous electrolyte secondary battery. That is, carbon powder having electron conductivity may be sufficient. For example, acetylene black, furnace black, graphite, hollow carbon, carbon fiber, carbon nanotube, graphene, etc. can be mentioned.

[0031] The thickener is not particularly limited as long as it is a material used in a non-aqueous electrolyte secondary battery. That is, a resin that can increase the viscosity of the slurry may be sufficient. For example, carboxymethyl cellulose, hydroxypropyl cellulose, and chitosan gum can be mentioned.

[0032] The binder is not particularly limited as long as it is a material used in a non-aqueous electrolyte secondary battery. That is, a resin that can bind each of the active material, the conductive material, and the current collector may be sufficient. For example, styrene-butadiene rubber, polyacrylic, polyvinyl alcohol, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamideimide, etc. can be mentioned. In the present disclosure, the above binder can be used as a solid such as powder, but it is preferably used in a solution or emulsion state because of its excellent slurry homogeneity.

[0033] The current collector is not particularly limited as long as it is a material used in a non-aqueous electrolyte secondary battery. That is, a metal having electron conductivity and not reacting during charge and discharge may be sufficient. For example, copper, aluminum, nickel, iron, titanium, carbon, etc. can be mentioned. There is no particular restriction on the shape of the current collector, but for example, foil-like, plate-like, fibrous, mesh, and porous bodies 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 heated at 50°C or higher, so that the liquid agent in the slurry can be vaporized and removed. Thereby, 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 the current collector can be obtained.

[0035] Here, the slurry means a fluid in which an active material, a conductive material, a thickener, and a binder are dispersed or dissolved in a liquid. That is, 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 agent used in the dilution step and the solvent used in the kneading step include water, N-methyl-2-pyrrolidone, alcohols, ketones, and the like. Either the same liquid or different liquids may be used for the liquid agent in the dilution step and the solvent in the kneading step.

[0037] [Non-aqueous electrolyte secondary battery] The electrode according to this embodiment can be used as an electrode of a non-aqueous electrolyte secondary battery. Here, the non-aqueous electrolyte secondary battery refers to a rechargeable battery using an electrolyte that does not contain water as a component. For example, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, calcium-ion batteries, etc. are applicable.

[0038] The non-aqueous electrolyte secondary battery is composed of at least three members: a positive electrode, a negative electrode, and an electrolyte. When the electrolyte has fluidity, a separator is further 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 a non-aqueous electrolyte secondary battery. That is, it only needs to have ion conductivity. Examples include electrolytic solutions, gel electrolytic solutions, ionic liquids, solid electrolytes, and the like.

[0040] The separator is not particularly limited as long as it is a material used in a non-aqueous electrolyte secondary battery. That is, it may be a film made of a material having no electronic conductivity and provided with innumerable through-holes.

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

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

[0043] When manufacturing the electrode of the present application, a material containing an active material, a conductive material, and a thickener for manufacturing an electrode of a non-aqueous electrolyte secondary battery was mixed in a high-speed shear impact mixer 10 (mixing step S01). In this test, graphite was used as the active material, acetylene black was used as the conductive material, and carboxymethyl cellulose was used as the thickener. In the high-speed shear impact mixer 10, the rotation speed of the mixing arm, which is the first blade 11 for mixing the whole, was 27 rpm, and the rotation speed of the chopper blade, which is the second blade 12 for applying a strong shearing force, was 2200 rpm, and mixing was performed for 5 minutes.

[0044] Thereafter, the powder mixed by the high-speed shear impact mixer 10 and styrene-butadiene rubber as a binder were put into a twin-shaft planetary stirring mixer 20, 150 g of water as a liquid agent was added, and the twin-shaft planetary stirring mixer 20 was operated at 100 rpm for 5 minutes to produce a slurry (dilution step S03). Further, a negative electrode (electrode of the present application) was formed using the slurry manufactured by the above method (forming step S04). As described above, the time required for manufacturing the slurry used for the electrode of the present application was 5 minutes in the high-speed shear impact mixer 10 and 5 minutes in the twin-shaft planetary stirring mixer 20, for a total of 10 minutes.

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

[0046] Also, using the electrode of the present application or the comparative electrode, a current collector, a counter electrode, a separator, and an electrolytic solution, coin cells were each manufactured. A copper foil with a thickness of 10 μm was used for the current collector, a lithium metal with a thickness of 500 μm was used for the counter electrode, a glass filter (GA-100) with a diameter of 16 mm, a PP / PE / PP microporous membrane (thickness 25 μm) was used for the separator, and 1M LiPF 6 / EC:DEC (=50:50 vol.%) was used for the electrolytic solution, an R2032 type coin cell was adopted for the battery cell, and the heat treatment conditions were vacuum, 120 degrees, and 12 hours.

[0047] Regarding the batteries manufactured using each electrode, evaluation by a cycle test was performed. In the cycle test, the environmental temperature was 30 degrees, the cut-off voltage was 0.001V - 1.0V, and the current value was 0.1C-rate.

[0048] As a result of the cycle test (100 cycles), for both the electrode of the present application and the comparative electrode, a battery performance with a discharge capacity equivalent to 100% was obtained (see Figure 4). That is, as a result of performing a performance evaluation of the battery using the electrodes of both manufacturing methods produced, no difference was observed in the battery performance. Thus, it was confirmed that the electrode of the present application can significantly shorten the manufacturing time without degrading the battery performance as compared with the comparative electrode manufactured by a generally implemented standard manufacturing method.

Explanation of Reference Signs

[0049] 10 High-speed shear impact mixer 10a Mixing container 10b Inlet 11 First blade 11a First shaft 12 Second blade 12a Second axis 20 Two-axis planetary stirring mixer 20a Mixing container 21 Rotating shaft 22 Planetary gear mechanism 23a First stirring part 23b Second stirring part S01 Mixing process S02 Kneading process S03 Dilution process S04 Forming process R1 First rotation direction R2 Second rotation direction

Claims

1. A mixing step of dry-mixing a material containing an active material, a conductive material, and a thickener, which constitutes an electrode used in a non-aqueous electrolyte secondary battery; A dilution step of adding a liquid agent to the mixture mixed in the mixing step to produce a slurry; A forming step of forming the slurry produced in the dilution step on the electrode, the method for manufacturing an electrode comprising: In the mixing step, the material is mixed using a high-speed shear impact mixer having a first blade for mixing the material as a whole and a second blade for applying a shearing force to the material.

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

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

4. After the mixing step and before the dilution step, a kneading step of adding a solvent to the mixture mixed in the mixing step and kneading is provided, In the dilution step, the slurry is produced by adding the liquid agent to the kneaded product kneaded in the kneading step. The method for manufacturing an electrode according to any one of claims 1 to 3.

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

Images