Method for producing electrode mixture and method for producing electrode

Abstract

A method for producing an electrode mixture (1) includes forming composite particles (8) by adhering a conductive material (6) to an electrode active material (4), forming a mixture (14) by mixing the composite particles (8) and clusters (12) of a fibrous binder (10), and forming an aggregate (16) in which a plurality of composite particles (8) are connected by the fibrous binder (10) by applying a shear force to the clusters (12) in the mixture (14) and defibrating the clusters (12).

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electrode mixture and a method for manufacturing an electrode. Background Art

[0002] Patent Document 1 describes the following technique: A granule containing an electrode active material, a binder, and a solvent is supplied into the gap between a pair of rolls and compressed to form a sheet-like electrode mixture layer.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018 - 186033 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] When forming a mixture plate from the powder of an electrode mixture, it is expected to stably maintain the shape of the mixture plate. However, it is not easy to achieve stable shape maintenance. This is especially true when forming a mixture plate from a dry electrode mixture with a low solvent content.

[0008] The present disclosure has been made in view of such a situation, and an object thereof is to provide a technique for easily forming a mixture plate from an electrode mixture.

[0009] Solutions to the Problems

[0010] One aspect of the present disclosure is a method for manufacturing an electrode mixture. The manufacturing method includes: attaching a conductive material to an electrode active material to form composite particles, mixing the composite particles with an aggregate of fibrous binders to form a mixture, and applying a shearing force to the aggregate in the mixture to defibrate it, thereby forming an aggregate in which a plurality of composite particles are connected by the fibrous binder.

[0011] Another aspect of the present disclosure is a method for manufacturing an electrode. The manufacturing method includes: forming an electrode mixture obtained by the method for manufacturing an electrode mixture according to the above aspect into a mixture plate, and laminating the mixture plate on a current collector to form an electrode.

[0012] Any combination of the above components, and a solution obtained by converting the expression of the present disclosure among methods, devices, systems, etc. is also effective as an aspect of the present disclosure.

[0013] Effects of the Invention

[0014] According to the present disclosure, a mixture plate can be easily formed from an electrode mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process diagram of the method for manufacturing an electrode mixture according to the embodiment.

[0016] Figure 2 It is a process chart of the manufacturing method of the electrode of the embodiment.

[0017] Figure 3 It is a figure showing the measurement results of the particle size distribution and the molding results of the binder plates in each example and each comparative example. Detailed Embodiments

[0018] Hereinafter, the present disclosure will be described with reference to the accompanying drawings based on preferred embodiments. The embodiments are illustrative and do not limit the present disclosure, and all features or combinations thereof described in the embodiments do not necessarily represent the essential content of the present disclosure. The same or equivalent components, parts, and processes shown in the respective drawings are denoted by the same reference numerals, and repeated explanations are appropriately omitted. In addition, the scales or shapes of the respective parts shown in the respective drawings are set for convenience of explanation, and are not to be construed in a limiting sense unless otherwise specified. Further, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, these terms do not indicate any order or importance, but are used to distinguish one component from another. In addition, in each drawing, a part of unimportant components is omitted for illustration when describing the embodiments.

[0019] Figure 1 It is a process chart of the manufacturing method of the electrode binder 1 of the embodiment. As Figure 1 shown, the manufacturing method of the electrode binder 1 includes a compounding process S101, a mixing process S102, and a coagulation process S103.

[0020] The composite chemical process S101 includes attaching a conductive material 6 to the electrode active material 4 to form composite particles 8. For example, the particulate electrode active material 4 and the particulate conductive material 6 are put into a known stirring granulator or a particle compounding device and stirred. As a result, the surface of the electrode active material 4 is covered with the conductive material 6, forming composite particles 8. Examples of the stirring granulator include an FM stirrer (manufactured by Nippon Coke Industry Co., Ltd.), a high-speed stirrer (manufactured by earthtechnica), a powerful internal mixer (manufactured by Nippon Eirich Co., Ltd.), Balance Gran (manufactured by Freund-turbo Co., Ltd.), a vertical granulator (manufactured by Powrex Co., Ltd.), etc. Examples of the particle compounding device include NOBILTA (registered trademark) (manufactured by HOSOKAWAMICRON Corporation), Mechanical Fusion (registered trademark) (manufactured by HOSOKAWA MICRON Corporation), etc. The electrode active material 4 and the conductive material 6 are appropriately selected according to the type of battery. For example, in the case of a normal lithium-ion secondary battery, the positive electrode of the electrode active material 4 is lithium cobaltate, lithium iron phosphate, etc., and the negative electrode is graphite, etc. In addition, the conductive material 6 is graphite, carbon black, acetylene black, etc. As an example, the median particle size of the conductive material 6 is less than 1 / 20 of the median particle size of the electrode active material 4.

[0021] The mixing process S102 includes: mixing the composite particles 8 and the clusters 12 of the fibrous binder 10 to form a mixture 14. For example, the clusters 12 of the fibrous binder 10 are added to the stirring granulator containing the composite particles 8 and stirred. As a result, the composite particles 8 and the clusters 12 are mixed to form a mixture 14. In the present embodiment, the fibrous binder 10 is polytetrafluoroethylene (PTFE).

[0022] When the electrode active material 4, the conductive material 6, and the fibrous binder 10 are mixed simultaneously, the attachment of the conductive material 6 to the surface of the electrode active material 4 may be hindered by the fibrous binder 10. As a result, the conductivity of the electrode mixture 1 may be reduced. In view of this, in the present embodiment, after the composite particles 8 are formed by the composite chemical process S101, the composite particles 8 and the fibrous binder 10 are mixed by the mixing process S102. As a result, the surface of the electrode active material 4 can be easily covered with the conductive material 6, and the conductivity of the electrode mixture 1 can be improved.

[0023] The agglomeration process S103 includes: applying a shearing force to the clusters 12 in the mixture 14 and defibrating them to form aggregates 16 in which a plurality of composite particles 8 are connected by fibrous binders 10. For example, by adjusting the rotational speed of the stirring blades in a stirring granulator containing the mixture 14, a desired shearing force is applied to the clusters 12. The clusters 12 are subjected to the shearing force, so that the fibrous binder 10 is unraveled linearly. Thereby, a network structure based on a plurality of fibrous binders 10 is formed. Moreover, a plurality of composite particles 8 are supported by this network structure to form aggregates 16 having a larger particle size than the composite particles 8. Through the above process, the electrode binder 1 containing a plurality of aggregates 16 is obtained.

[0024] In addition, when kneading the mixture 14 using a roll mill, the clusters 12 are subjected to a shearing force and defibrated by the peripheral speed difference between adjacent rolls, etc. In addition, when kneading the mixture 14 using a kneading screw, the clusters 12 are subjected to a shearing force and defibrated by the speed difference between the screw and the wall surface, etc. In addition, the mixing process S102 and the agglomeration process S103 can be implemented as a series of processes or simultaneously in parallel. That is, when the clusters 12 are put into the stirring granulator, the mixing of the composite particles 8 and the clusters 12 and the defibrating of the clusters 12 can be carried out continuously or simultaneously in parallel.

[0025] As an example, the electrode binder 1 is a dry electrode binder. For the dry electrode binder, the solvent content is 10% by mass or less, or 5% by mass or less, or 3% by mass or less, or 0.1% by mass, or substantially 0% with respect to the total mass of the dry electrode binder. When using the dry electrode binder, the drying furnace of the binder plate 18 described later can be omitted. In addition, the electrode binder 1 can also be a wet electrode binder with a solvent content higher than 10%.

[0026] The solvents used in the electrode binder 1, when the electrode binder 1 is used as the negative electrode, include, for example, water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc. In addition, when the solvent is used as the positive electrode in the electrode binder 1, amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine, ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone, ester solvents such as methyl acetate, dimethylacetamide, amide solvents such as N-methyl-2-pyrrolidone, etc. are exemplified.

[0027] In addition, in the mixing process S102, a conductive material 6 can be further added and mixed in addition to the composite particles 8 and the clusters 12. By adding the conductive material 6 when forming the mixture 14, the conductive material 6 is easily attached to the surface of the fibrous binder 10. Thereby, the conductivity between the composite particles 8 can be further improved in the aggregate 16. Therefore, the conductivity of the electrode binder 1 can be further improved.

[0028] The obtained electrode mixture 1 is used in the manufacture of the electrode 2. Figure 2 is a process chart of the manufacturing method of the electrode 2 of the embodiment. As Figure 2 shown, the manufacturing method of the electrode 2 includes a forming process S104 and a laminating process S105.

[0029] The forming process S104 includes: forming the electrode mixture 1 obtained by the above manufacturing method on the mixture plate 18. For example, the electrode mixture 1 is accommodated in a known storage unit 20. The storage unit 20 has a known structure such as a combination of a hopper and a feeding unit, for example. The electrode mixture 1 accommodated in the storage unit 20 is supplied into the gap between a pair of supply rollers 22 provided in the feeding unit. The pair of supply rollers 22 rotate in opposite directions to each other, and the electrode mixture 1 supplied into the gap is compressed into a sheet shape. Thus, the mixture plate 18 is formed. The mixture plate 18 is continuously sent out from the gap between the pair of supply rollers 22. The mixture plate 18 may be stretched to a desired thickness before entering the laminating process S105.

[0030] The laminating process S105 includes laminating the mixture plate 18 on the current collector 24 to form the electrode 2. For example, the mixture plate 18 is supported and conveyed by the circumferential surface of the conveying roller 26. In addition, at a position opposite to the conveying roller 26, a laminating roller 28 is provided. The current collector 24 is supported and conveyed by the circumferential surface of the laminating roller 28. The mixture plate 18 and the current collector 24 pass through the gap between the conveying roller 26 and the laminating roller 28. At this time, the mixture plate 18 and the current collector 24 are pressed in a state of overlapping each other. Thus, the mixture plate 18 is laminated on the current collector 24 to form the electrode 2. In addition, in the laminating process S105 of the present embodiment, the mixture plate 18 can be laminated on the current collector 24 without performing a heat treatment. When it is a normal lithium-ion secondary battery, the positive electrode of the current collector 24 is made of aluminum foil or the like, and the negative electrode is made of copper foil or the like.

[0031] As described above, in the manufacturing method of the electrode mixture 1 of the present embodiment, after forming the composite particles 8 of the electrode active material 4 and the conductive material 6, the clusters 12 of the composite particles 8 and the fibrous binder 10 are mixed. Then, the clusters 12 in the mixture 14 are defibrated to form an aggregate 16 in which a plurality of composite particles 8 are connected by the fibrous binder 10. Thus, compared with the case where the aggregate 16 without the composite particles 8 is formed, the mixture plate 18 can be easily formed from the electrode mixture 1.

[0032] In particular, when the electrode mixture 1 is a dry electrode mixture, it is more difficult to maintain the shape of the mixture plate 18 than when the electrode mixture 1 is a wet electrode mixture. Therefore, the manufacturing method of the electrode mixture 1 of the present embodiment can function particularly effectively when the electrode mixture 1 is dry. In addition, according to the manufacturing method of the electrode mixture 1 of the present embodiment, the conductivity of the electrode mixture 1 can be improved. In particular, when the electrode mixture 1 is a mixture for a positive electrode, a higher conductivity is tendentially required than when it is a mixture for a negative electrode. Therefore, the manufacturing method of the electrode mixture 1 of the present embodiment can function particularly effectively when the electrode mixture 1 is for a positive electrode.

[0033] In addition, when it is difficult to mold the mixture plate 18, it is considered to coat the electrode mixture 1 on the current collector 24 and mold the electrode mixture 1 into a sheet shape on the current collector 24 to form an electrode mixture layer. However, it is not easy to adjust the thickness of the electrode mixture layer at this time. In this regard, in the present embodiment, the mixture plate 18 is directly molded from the electrode mixture 1. Therefore, the thickness of the mixture plate 18 can be adjusted in a state without including the current collector 24. Therefore, the thickness of the mixture plate 18 can be adjusted simply and with high precision. In addition, by laminating the mixture plate 18 on the current collector 24 to form the electrode 2, an electrode 2 with higher quality can be obtained.

[0034] Above, the embodiments of the present disclosure have been described in detail. The foregoing embodiments only show specific examples when implementing the present disclosure. The content of the embodiments does not limit the technical scope of the present disclosure. Within the scope not departing from the idea of the present disclosure defined in the claims, various design changes such as changes, additions, and deletions of components can be made. The new embodiments with design changes have the effects of both combined embodiments and deformations. In the foregoing embodiments, regarding the content that allows such design changes, expressions such as "in the present embodiment" and "in the present embodiment" are used for emphasis, and design changes are allowed even for content without such expressions. Any combination of the components included in each embodiment is also effective as a solution of the present invention. The hatching marked on the cross-section of the drawings does not limit the material of the object marked with hatching.

[0035] The embodiments can also be determined by the items described below.

[0036] [First item]

[0037] A manufacturing method of an electrode mixture (1), comprising:

[0038] causing a conductive material (6) to adhere to an electrode active material (4) to form composite particles (8),

[0039] mixing the composite particles (8) and an aggregate (12) of a fibrous binder (10) to form a mixture (14),

[0040] Shearing force is applied to the clusters (12) in the mixture (14) to defibrate, forming an aggregate (16) in which a plurality of composite particles (8) are connected by a fibrous binder (10).

[0041] [Second item]

[0042] The method for manufacturing the electrode binder (1) as described in the first item,

[0043] In the formation of the mixture (14), it includes adding a conductive material (6) to the composite particles (8) and the clusters (12) and mixing them.

[0044] [Third item]

[0045] The method for manufacturing the electrode binder (1) as described in the first item or the second item,

[0046] The fibrous binder (10) is polytetrafluoroethylene.

[0047] [Fourth item]

[0048] A method for manufacturing an electrode (2), including:

[0049] Forming the electrode binder (1) obtained by the method for manufacturing the electrode binder (1) according to any one of the first item to the third item into a binder plate (18),

[0050] Stacking the binder plate (18) on the current collector (24) to form an electrode (2).

[0051] Examples

[0052] The examples of the present invention are described below. However, the examples are only illustrative for well explaining the present invention and are not used to limit the present invention in any way.

[0053] (Example 1)

[0054] 1000 g of a lithium transition metal composite oxide as an electrode active material and 10 g of acetylene black as a conductive material are put into a particle compounding device NOB300 - NOBILTA (registered trademark) (manufactured by Hosokawa Micron Corporation). Then, they are mixed for 5 minutes to form composite particles. Next, the obtained composite particles and 10 g of clusters of PTFE as a binder are put into a stirring granulator FM - 5 (manufactured by Nippon Coke & Engineering Co., Ltd.). The peripheral speed of the stirring blade is set to 32 m / s, and the mixture of the composite particles and PTFE is stirred for 3 minutes and kneaded. Thus, an electrode binder is obtained.

[0055] The particle size distribution of the obtained electrode mixture is measured by the sieving method. In addition, the obtained electrode mixture is put into a roll forming machine to attempt to form a mixture plate. Figure 3 The measurement results of the particle size distribution and the forming results of the mixture plate are shown.

[0056] (Example 2)

[0057] Except for the aspect of kneading the mixture with two roll mills (manufactured by Iwamoto Seisakusho), the production, particle size distribution measurement, and mixture plate forming of the electrode mixture are carried out in the same manner as in Example 1. In addition, for the two roll mills, the rotation speed of the first roll is set to 5 rpm, and the rotation speed of the second roll is set to 15 rpm. Therefore, the roll speed ratio is 1:3. In Figure 3 The measurement results of the particle size distribution and the forming results of the mixture plate are shown.

[0058] (Comparative Example 1)

[0059] Except for the aspect of setting the peripheral speed of the stirring blade to 15 m / s and stirring the mixture for 10 minutes, the production, particle size distribution measurement, and mixture plate forming of the electrode mixture are carried out in the same manner as in Example 1. In Figure 3 The measurement results of the particle size distribution and the forming results of the mixture plate are shown.

[0060] (Comparative Example 2)

[0061] Except for the aspect of using 10 g of polyvinylidene fluoride (PVdF) as the binder, the production, particle size distribution measurement, and mixture plate forming of the electrode mixture are carried out in the same manner as in Example 1. In Figure 3 The measurement results of the particle size distribution and the forming results of the mixture plate are shown.

[0062] (Comparative Example 3)

[0063] Except for the aspect of not performing the kneading treatment of the mixture, the production, particle size distribution measurement, and mixture plate forming of the electrode mixture are carried out in the same manner as in Example 2. In Figure 3 The measurement results of the particle size distribution and the forming results of the mixture plate are shown.

[0064] Figure 3 is a graph showing the measurement results of the particle size distribution and the forming results of the mixture plate in each example and each comparative example. As Figure 3As shown, in Example 1, the particles passing through a sieve with a mesh size of 45 μm accounted for 13% of the entire electrode mixture, and the particles remaining on the sieve accounted for 87% of the entire electrode mixture. In addition, in Example 2, the particles passing through a sieve with a mesh size of 45 μm accounted for 14.4% of the entire electrode mixture, and the particles remaining on the sieve accounted for 85.6% of the entire electrode mixture. From these results, it can be confirmed that the electrode mixtures of Examples 1 and 2 are mostly composed of large-sized aggregates. In addition, in Examples 1 and 2, a mixture plate can be formed.

[0065] In Comparative Examples 1 to 3, the particles passing through a sieve with a mesh size of 45 μm accounted for approximately 90% to approximately 92% of the entire electrode mixture, and the particles remaining on the sieve accounted for approximately 8% to approximately 10% of the entire electrode mixture. From these results, it can be confirmed that the electrode mixtures of Comparative Examples 1 to 3 are mostly composed of fine powders. In addition, in Comparative Examples 1 to 3, a mixture plate cannot be formed. That is, even if the electrode mixture is formed into a sheet shape, it cannot maintain that shape and will deform.

[0066] From the above results, it can be confirmed that the electrode mixture contains aggregates in which composite particles are connected by fibrous binders, and thus a mixture plate can be formed simply and stably. In addition, the PVdF contained in the electrode mixture of Comparative Example 2 is a binder that is more difficult to defibrillate than PTFE. Therefore, in Comparative Example 2, it is considered that although the same shear force was applied to the mixture as in Example 1, the composite particles did not aggregate. In Comparative Example 2, it is considered that a so-called mechanochemical reaction occurred, resulting in a state where the surface of each composite particle is covered with PVdF.

[0067] Industrial Applicability

[0068] The present disclosure can be used in a method for manufacturing an electrode mixture and a method for manufacturing an electrode.

[0069] Explanation of Reference Numerals

[0070] 1 Electrode mixture, 2 Electrode, 4 Electrode active material, 6 Conductive material, 8 Composite particle, 10 Fibrous binder, 12 Cluster, 14 Mixture, 16 Aggregate, 18 Mixture plate, 24 Current collector.

Claims

1. A manufacturing method of an electrode mixture, comprising: attaching a conductive material to an electrode active material to form composite particles, mixing the composite particles with clusters of a fibrous binder to form a mixture, applying a shearing force to the clusters in the mixture to defibrate and form an aggregate in which a plurality of the composite particles are connected by the fibrous binder.

2. The manufacturing method of the electrode mixture according to claim 1, in the formation of the mixture, including adding and mixing the conductive material in the composite particles and the clusters.

3. The manufacturing method of the electrode mixture according to claim 1 or 2, the fibrous binder is polytetrafluoroethylene.

4. A manufacturing method of an electrode, comprising: forming the electrode mixture obtained by the manufacturing method of the electrode mixture according to claim 1 or 2 into a mixture plate, laminating the mixture plate on a current collector to form an electrode.

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