Electrode manufacturing method

Abstract

To reduce specific foreign substances (magnetic substances, Cu).SOLUTION: An electrode material containing active material powder is prepared. A classifier performs a dry classification process on the electrode material. An electrode is manufactured by using an electrode material that has undergone the dry classification process. The breakage of a mesh screen is detected by monitoring at least one of the operating sound of the classifier and the torque of a motor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode, a classification system, an electrode material, and an electrode. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2014-102967 (Patent Document 1) discloses a filter for filtering a slurry for forming an active material layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-102967 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, electrodes are manufactured by applying a liquid coating. That is, an electrode material is mixed with a solvent to prepare a slurry. The electrode material may contain, in addition to an active material powder, a binder, a conductive material, etc. The slurry is applied to the surface of a substrate to manufacture an electrode.

[0005] The solvent can dissolve the binder. The solvent also serves as a dispersion medium for solid particles. The solvent can include, for example, an organic solvent. For example, from the viewpoint of production costs, environmental impact, etc., it is desired to reduce the amount of solvent used in electrode production. Therefore, processes that do not go through a slurry have also been proposed. For example, a powder coating is prepared by mixing an active material powder and a binder. The powder coating is a wet powder or a dry powder. An electrode can be produced by applying the powder coating to the surface of a substrate.

[0006] Active material powder is an aggregate of active material particles. The active material particles cause an electrode reaction. Ideally, active material powder consists of active material particles. However, active material powder may also contain trace amounts of foreign matter. Foreign matter is unintentional impurities. Foreign matter includes metals. Foreign matter is thought to be generated, for example, by wear of active material powder manufacturing equipment. The foreign matter is in particulate form. Foreign matter mixed into an electrode may have a negative impact on battery performance. This impact is particularly noticeable when the foreign matter is coarse particles. For example, it may increase the battery's self-discharge rate.

[0007] The foreign matter may include magnetic substances. Magnetic substances may include, for example, iron (Fe), iron oxide, and stainless steel (SUS)-derived components. Conventionally, after active material powder synthesis, the active material powder is subjected to a magnetic separation process (hereinafter referred to as "magnetic separation process") to reduce the amount of magnetic substances. However, the separation efficiency of magnetic separation process is not sufficient. For example, active material particles such as lithium cobalt oxide may also be magnetic. When active material particles are magnetic, the separation efficiency of foreign matter may decrease. This is because the active material particles also adhere to magnets. Furthermore, non-magnetic foreign matter also exists. For example, copper (Cu) is not magnetic. Hereinafter, "magnetic substances and foreign matter containing Cu" will also be referred to as "specific foreign matter."

[0008] Conventionally, specific foreign matter has been reduced by filtering a slurry containing an electrode material, but this method cannot be applied to powder coatings (wet powder or dry powder).

[0009] The object of the present disclosure is to reduce specific foreign matter (magnetic matter, Cu). [Means for solving the problem]

[0010] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action in this specification includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0011] 1. The method for producing an electrode includes the following steps (a) to (c): (a) An electrode material containing an active material powder is prepared. (b) The electrode material is subjected to dry classification using a classification device. (c) An electrode is manufactured using the electrode material that has been subjected to (b) above. The classification device includes a mesh screen, a blade, and a motor. The mesh screen has a cylindrical outer shape. The mesh screen is electrically insulating. The mesh screen is configured to separate coarse particles from the electrode material. The motor is configured to rotate the blade along the inner circumferential surface of the mesh screen. The blade is configured to press the electrode material against the mesh screen. The above (b) includes detecting breakage of the mesh screen by monitoring at least one of the operating sound of the classification device and the torque of the motor. In the above (b), when breakage of the mesh screen is detected, the electrode material in the classification device is not used for manufacturing electrodes.

[0012] According to the new findings of the present disclosure, the specific foreign matter (magnetic material, Cu) is a coarse particle. The coarse particle can be separated from the electrode material by dry classification. Compared to a method of filtering a slurry with a filter, dry classification can have a high separation efficiency. In other words, the specific foreign matter can be reduced compared to the conventional method.

[0013] In dry classification, mesh screens are used. Mesh screens tend to break easily. Breakage of the mesh screen can cause specific foreign matter to get into the electrode. In other words, there is room for improvement in the stability of quality.

[0014] One method for detecting breakage of the mesh screen is to monitor changes in the electrical resistance of the mesh screen. That is, the mesh screen is made conductive. When the mesh screen breaks, the electrical resistance of the mesh screen may increase. Breakage of the mesh screen can be detected by the increase in electrical resistance. However, electrode materials generally contain conductive substances. If the electrode material contains conductive substances, breakage of the mesh screen may not be detected.

[0015] Therefore, damage to the mesh screen is detected by the operating sound of the classification device and the torque of the motor. This makes it possible to detect damage to the mesh screen even if the electrode material contains a conductive substance. By detecting damage to the mesh screen, electrodes with reduced specific foreign matter can be produced stably. In other words, stable quality is expected.

[0016] 2. The electrode material may include, for example, a conductive substance.

[0017] 3. (b) above may include, for example, detecting frequency components resulting from breakage of the mesh screen by analyzing the frequency of the operating noise.

[0018] 4. (b) above may include determining that breakage of the mesh screen has occurred when the torque falls outside a reference range.

[0019] 5. The above (c) may include, for example, the following (c1) and (c2): (c1) A paint containing an electrode material is prepared. (c2) The paint is applied to the surface of the substrate. The coating material may contain, in addition to the electrode material, at least one selected from the group consisting of a conductive material, a solid electrolyte, a binder, an additive, and a solvent.

[0020] 6. The paint may have a solids content of 70 to 100% by mass.

[0021] A paint having a solid content of 70 to 100% can be a powder paint (wet powder, dry powder), while a liquid paint (slurry) can have a solid content of, for example, 60% or less.

[0022] 7. The classification system performs dry classification on the electrode material. The classification system includes a classification device and a detection device. The classification device includes a mesh screen, a blade, and a motor. The mesh screen has a cylindrical outer shape. The mesh screen is electrically insulating. The mesh screen is configured to separate coarse particles from the electrode material. The motor is configured to rotate the blade along the inner circumferential surface of the mesh screen. The blade is configured to press the electrode material against the mesh screen. The detector is configured to detect breakage of the mesh screen by monitoring at least one of the operating sound of the classifier and the torque of the motor.

[0023] 8. The classification system may further include a control device, which may be configured to stop operation of the classification device when the detection device detects damage.

[0024] 9. The electrode material includes an active material powder, and the electrode material has a magnetic material content of 4 ppm or less by mass fraction and a copper content of 1 ppm or less by mass fraction.

[0025] 10. The electrode includes the electrode material described in "9." above.

[0026] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") and an example of the present disclosure (hereinafter may be abbreviated as "the present example") will be described. However, the present embodiment and the example do not limit the technical scope of the present disclosure. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a block diagram showing a classification system according to this embodiment. [Figure 2] FIG. 2 is a first schematic cross-sectional view showing an example of the classification device according to the present embodiment. [Figure 3] FIG. 3 is a second schematic cross-sectional view showing an example of the classification device in this embodiment. [Figure 4] FIG. 4 is a schematic flowchart of a method for producing an electrode in this embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the first coating method. [Figure 6] FIG. 6 is a schematic diagram showing the second coating method. DETAILED DESCRIPTION OF THE INVENTION

[0028] <Definitions of terms, etc.> In this specification, the terms "comprise," "include," "have," and variations thereof (e.g., "consisting of") are open-ended. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even in closed-ended terms, additional elements that are normally incidental impurities or unrelated to the disclosed technology are not excluded. The term "consisting essentially of..." is semi-closed. Semi-closed terms allow for the addition of elements that do not substantially affect the basic and novel characteristics of the disclosed technology.

[0029] In this specification, expressions such as "may" and "can" are used in the permissive sense of "possibly" rather than the obligatory sense of "must."

[0030] In this specification, elements expressed in the singular include the plural unless otherwise specified. For example, a "particle" can mean not only "one particle" but also "an aggregate of particles (powder, powder, particle group)."

[0031] In this specification, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described unless otherwise specified. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0032] In this specification, unless otherwise specified, a numerical range such as "m to n%" includes both the upper and lower limits. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." Furthermore, a numerical value arbitrarily selected from within the numerical range may be set as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0033] In this specification, all numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the disclosed technology. All numerical values ​​may be expressed with significant figures. Measured values ​​may be the average value of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values ​​may be rounded off based on the number of significant figures. Measured values ​​may include errors, such as those associated with the detection limits of the measuring device.

[0034] In this specification, when a compound is expressed by a stoichiometric formula (e.g., "LiCoO2"), the stoichiometric formula is merely a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobalt oxide is expressed as "LiCoO2," unless otherwise specified, the lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2" and may contain Li, Co, and O in any composition ratio. Furthermore, doping or substitution with trace elements may be permitted.

[0035] Geometric terms used in this specification (e.g., "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms used in this specification may include, for example, tolerances, errors, etc. in design, work, manufacturing, etc. The dimensional relationships in each drawing may not match the actual dimensional relationships. To facilitate understanding of the disclosed technology, the dimensional relationships (length, width, thickness, etc.) in each drawing may be changed. Furthermore, some configurations may be omitted.

[0036] In this specification, the term "electrode" refers collectively to a positive electrode and a negative electrode. The electrode may be a positive electrode or a negative electrode. The electrode may be applied to any battery system. In this embodiment, an application to a lithium ion battery will be described as an example.

[0037] In this specification, "D50" refers to the particle size at which the cumulative frequency of the smaller particle size reaches 50% in a volume-based particle size distribution. "D99" refers to the particle size at which the cumulative frequency of the smaller particle size reaches 99% in a volume-based particle size distribution. D50 and D99 can be measured by a laser diffraction method.

[0038] In this specification, particles have a minor axis and a major axis. The "major axis" refers to the distance between the two most distant points on the contour of a particle image. The "minor axis" refers to the diameter perpendicular to the line segment that forms the major axis at its midpoint. The minor axis may be equal to the major axis.

[0039] In this specification, the term "solid content" refers to the total mass fraction of solid components in the paint. Components dissolved in the solvent (such as polymer binders) are considered to be solid components.

[0040] In this specification, "slurry" refers to a dispersion system in which a solid (powder) is dispersed in a liquid (solvent), and "wet powder" refers to a dispersion system in which a solid (powder) is dispersed in a liquid (solvent).

[0041] In this specification, the "volume resistivity (Ω·cm)" of a powder can be measured, for example, using a powder resistivity measurement system "MCP-PD" series manufactured by Nitto Seiko Analytech Co., Ltd. (or an equivalent product). The sample weight is 2.0 g. The measurement load is 20 kN.

[0042] <Classification system> FIG. 1 is a block diagram showing a classification system according to this embodiment. Hereinafter, the "classification system according to this embodiment" may be abbreviated as "the present classification system." The present classification system 1000 includes a classification device 100 and a detection device 200. The present classification system 1000 may further include, for example, a control device 300. The classification device 100, the detection device 200, and the control device 300 may be separate and independent, or may be integrated and inseparable.

[0043] 《Classifying device》 2 is a first schematic cross-sectional view showing an example of a classification device according to the present embodiment. The classification device 100 performs dry classification on an electrode material (powder material 10). The classification device 100 includes a housing 110, a mesh screen 120, a blade 130, a rotor 140, and a motor 150.

[0044] The housing 110 includes a main body 111, a supply section 112, a first discharge section 113, and a second discharge section 114. The main body 111 has a cylindrical outer shape. The main body 111 may have a cylindrical outer shape. The main body 111 houses a mesh screen 120, a blade 130, and a rotor 140. The supply section 112 extends to guide the powder material 10 to the main body 111. The first discharge section 113 is disposed below the main body 111. Fine particles 11 are discharged from the first discharge section 113. The second discharge section 114 is disposed in the axial direction (Y-axis direction) of the main body 111. Coarse particles 12 are discharged from the second discharge section 114. The second discharge section 114 extends to guide the coarse particles 12 downward.

[0045] The mesh screen 120 has a cylindrical outer shape. The mesh screen 120 may have, for example, a cylindrical outer shape. The mesh screen 120 is disposed inside the main body 111. The axis of the mesh screen 120 may coincide with the axis of the main body 111.

[0046] The mesh screen 120 is a mesh sieve. The mesh screen 120 separates coarse particles 12 from the powder material 10. The size of the coarse particles 12 to be separated can be determined by the opening size of the mesh screen 120. The opening size of the mesh screen 120 can be adjusted so that the coarse particles 12 (specific foreign matter) do not pass through and the fine particles 11 (electrode material) pass through.

[0047] The fine particles 11 (electrode material) may have a D99 of less than 50 μm. The fine particles 11 may have a D99 of, for example, 30 to 40 μm. The coarse particles 12 (specific foreign matter) may have a minor axis of, for example, 50 μm or more. The minor axis of the coarse particles 12 may be, for example, 2 to 10 times, 2 to 5 times, or 2 to 3 times the D99 of the fine particles 11.

[0048] The mesh screen 120 is electrically insulating. The mesh screen 120 may be made of, for example, a resin. The mesh screen 120 may contain, for example, at least one selected from the group consisting of polyester, polyamide, and polyarylate.

[0049] The motor 150 rotates the shaft 151. The shaft 151 is inserted into the rotor 140. The rotation of the shaft 151 rotates the rotor 140. The axes of the shaft 151, the rotor 140, and the mesh screen 120 may be aligned.

[0050] The rotor 140 includes a screw portion 141. The screw portion 141 is disposed below the supply portion 112. The screw portion 141 extends spirally on the surface of the rotor 140 along the rotation axis of the rotor 140. As the rotor 140 rotates, the screw portion 141 transports the powder material 10 to the main body portion 111.

[0051] The blades 130 are connected to the rotor 140. As the shaft 151 rotates, the blades 130 rotate along the inner circumferential surface of the mesh screen 120.

[0052] FIG. 3 is a second schematic cross-sectional view illustrating an example of a classification device according to this embodiment. The cross section in FIG. 3 is perpendicular to the rotation axis of the shaft 151. The blade 130 may extend, for example, radially from the shaft 151 toward the inner circumferential surface of the mesh screen 120. The blade 130 may be, for example, plate-shaped. As the blade 130 moves along the inner circumferential surface of the mesh screen, the powder material 10 is dispersed onto the inner circumferential surface of the mesh screen 120. The powder material 10 is then pressed against the mesh screen 120. Fine particles 11 in the powder material 10 pass through the mesh screen 120 and are discharged from the first discharge section 113. Coarse particles 12 in the powder material 10 cannot pass through the mesh screen 120. The coarse particles 12 move in the Y-axis direction along the inner circumferential surface of the mesh screen 120. The coarse particles 12 are discharged from the second discharge section 114.

[0053] For example, the blade 130 presses the powder material 10 against the mesh screen 120, causing an impact on the mesh screen 120. For example, the impact may cause damage to the mesh screen 120. If operation continues after the mesh screen 120 is damaged, the coarse particles 12 (specific foreign matter) may enter the first discharge section 113 (non-defective product side).

[0054] Detector The detection device 200 detects damage to the mesh screen 120. Damage to the mesh screen 120 may change the operating noise of the classifier 100. Damage to the mesh screen 120 may change the torque of the motor 150. The detection device 200 detects damage to the mesh screen 120 by monitoring at least one of the operating noise of the classifier 100 and the torque of the motor 150. The detection device 200 may monitor either the operating noise or the torque, or may monitor both the operating noise and the torque.

[0055] The detection device 200 may include, for example, a sound sensor (not shown) and an analysis device (not shown). The sound sensor measures the operating sound of the classifier 100. The analysis device collects and analyzes data on the operating sound. The analysis device may, for example, analyze the frequency of the operating sound. The analysis device may, for example, decompose the data on the operating sound into frequency components by Fast Fourier Transformation (FFT). Of the decomposed frequency components, a frequency component resulting from damage to the mesh screen 120 may be identified. By detecting the frequency component, damage to the mesh screen 120 may be detected.

[0056] The detection device 200 may include, for example, a torque sensor. The torque sensor measures the torque of the motor 150. When the mesh screen 120 is damaged, the torque may increase. When the mesh screen 120 is damaged, the torque may decrease. For example, a reference range (lower limit value, upper limit value) may be set for the torque. During steady operation, the torque may fluctuate within the reference range. When the mesh screen 120 is damaged, the torque may deviate from the reference range. When the torque deviates from the reference range, it may be determined that damage to the mesh screen 120 has occurred.

[0057] Control device The control device 300 can control the operation and cooperation of each device. For example, when the detection device 200 detects damage to the mesh screen 120, the control device 300 may stop the operation of the classifier 100. For example, when the detection device 200 detects damage to the mesh screen 120, the control device 300 may determine that the electrode material in the classifier 100 is defective. For example, when the detection device 200 detects damage to the mesh screen 120, the control device 300 may discharge the electrode material in the classifier 100 to the second discharge unit 114 (defective product side).

[0058] The defective product may be subjected to dry classification again. The defective product that has been subjected to dry classification again may be determined to be a non-defective product.

[0059] <Electrode manufacturing method> 4 is a schematic flowchart of the method for manufacturing an electrode according to this embodiment. Hereinafter, the "method for manufacturing an electrode according to this embodiment" may be abbreviated as "the present manufacturing method." The present manufacturing method includes "(a) preparation of an electrode material," "(b) dry classification," and "(c) manufacturing of an electrode."

[0060] (a) Preparation of electrode materials The manufacturing method includes preparing an electrode material. The electrode material includes an active material powder. The electrode material may consist of, for example, the active material powder. The electrode material may also include an additional component. In addition to the active material powder, the electrode material may also include, for example, at least one selected from the group consisting of a conductive material, a solid electrolyte, a binder, and an additive. An electrode material including an additional component such as a binder may also be referred to as an "electrode mixture."

[0061] For example, the electrode material may be prepared by mixing at least one selected from the group consisting of a conductive material, a solid electrolyte, a binder, and an additive with an active material powder. For example, the electrode material may be prepared by simple dry mixing. For example, the active material powder may be composited with other materials by mechanochemical treatment or the like.

[0062] <Active material powder> The active material powder is the main component of the electrode material. In the electrode material, the active material powder may account for, for example, 50 to 100% by mass. The active material powder may have a D50 of, for example, 1 to 30 μm, or 5 to 20 μm.

[0063] The active material powder may be, for example, a powder of a positive electrode active material. The positive electrode active material may contain, for example, at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, "(NiCoMn)" in "Li(NiCoMn)O2" indicates that the sum of the composition ratios in parentheses is 1. As long as the sum is 1, the amounts of the individual components are arbitrary. Li(NiCoMn)O2 may be, for example, Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 ) O2, etc.

[0064] The active material powder may be, for example, a powder of a negative electrode active material, such as graphite, soft carbon, hard carbon, silicon, silicon oxide, tin, tin oxide, and Li4Ti5O. 12 It may contain at least one selected from the group consisting of:

[0065] The active material powder may be magnetic. For example, active materials containing transition metal elements such as Fe, cobalt (Co), and nickel (Ni) may be magnetic. For example, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4 may be magnetic.

[0066] <Conductive material> The conductive material may be in powder form. The conductive material may include, for example, conductive carbon particles, conductive carbon fibers, etc. The conductive material may include, for example, at least one material selected from the group consisting of carbon black, vapor-grown carbon fiber, carbon nanotubes (CNT), graphene flakes, and graphite. The carbon black may include, for example, at least one material selected from the group consisting of acetylene black, furnace black, channel black, and thermal black. The amount of the conductive material to be blended may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material powder.

[0067] <Solid electrolyte> The solid electrolyte may be in powder form. The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes, and boron hydride solid electrolytes. The solid electrolyte may include, for example, at least one selected from the group consisting of Li2S-P2S5, LiI-Li2S-P2S5, LiBr-Li2S-P2S5, and LiI-LiBr-Li2S-P2S5. The amount of solid electrolyte may be, for example, 1 to 100 parts by volume per 100 parts by volume of the active material powder.

[0068] <Binder> The binder may be in powder form. The binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide (PI), polyamideimide (PAI), and polyacrylic acid (PAA). The amount of binder blended may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material powder.

[0069] <Additives> The additive may be in powder form. The additive may have any function. The additive may contain, for example, lithium phosphate. The amount of the additive may be, for example, 0.01 to 10 parts by mass per 100 parts by mass of the active material powder.

[0070] <Conductive substance> Conductive materials can interfere with the detection of mesh screen damage due to changes in electrical resistance in a classification device. In this manufacturing method, the classification system described above is used, so that mesh screen damage can be detected even if the electrode material contains a conductive material. The conductive material can be, for example, 1×10 2 The volume resistivity may be less than Ω·cm. Table 1 below shows the relationship between the volume resistivity of various materials and whether or not damage can be detected by changes in electrical resistance. 2 When the resistance is less than Ω·cm, it tends to become difficult to detect damage based on changes in electrical resistance.

[0071] [Table 1]

[0072] 《(b) Dry classification》 This manufacturing method includes subjecting the electrode material to a dry classification process using a classification device. The processing target may be only the active material powder, or may be the electrode mixture. The dry classification process in this manufacturing method can be performed using the classification system described above. The dry classification process can separate coarse particles (specific foreign matter) from the electrode material. If damage to the mesh screen is detected during operation of the classification device, the electrode material in the classification device will not be used in the manufacture of electrodes.

[0073] <Electrode material> Dry classification can produce an electrode material with reduced specific foreign matter (magnetic material, Cu). The content of magnetic material in the electrode material is 4 ppm or less by mass fraction. The magnetic material can include, for example, Fe, iron oxide, SUS-derived components, etc. The SUS-derived components may include, for example, Ni, chromium (Cr), manganese (Mn), etc. The content of magnetic material may be, for example, 2.2 ppm or less, 1.9 ppm or less, 1.8 ppm or less, or 1.3 ppm or less. The content of magnetic material may even be zero.

[0074] In the electrode material, the Cu content is 1 ppm or less in mass fraction, and the Cu content may be zero.

[0075] <Method for quantifying magnetic substances> The magnetic material can be quantified by the following procedure. (1) N-methyl-2-pyrrolidone (NMP) is prepared as a dispersion medium. An electrode material is prepared as a sample. The sample is dispersed in the dispersion medium using a mixer. This prepares a particle dispersion. (2) A bar magnet is immersed in the particle dispersion to capture magnetic substances in the particle dispersion. (3) The bar magnet is pulled out of the particle dispersion, and the magnetic material attached to the bar magnet is collected. For example, the magnetic material may be collected using adhesive tape. (4) The maximum diameter (dmax) of the magnetic particles and the number of magnetic particles are measured using a microscope. (5) The volume of the magnetic material can be calculated by considering the magnetic material as a sphere with a diameter of dmax. The density of the magnetic material can be calculated from the composition of the magnetic material. The mass fraction of the magnetic material can be calculated from the volume, number, and density of the magnetic material.

[0076] <Cu quantification method> Cu can be quantified by the following procedure, where "1 ppm" may be the detection limit for the procedure. (1) An electrode material is prepared as a sample. The sample is decomposed with an acid to form a solution. (2) The solution is filtered to recover the residue and the filtrate. (3) The residue is incinerated. The incinerated material is dissolved in alkali and then extracted with acid. (4) The filtrate obtained in (2) above and the extract obtained in (3) above are mixed to prepare a sample solution. The sample solution is adjusted to a fixed volume. (5) The sample solution is analyzed by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), which measures the mass fraction of Cu.

[0077] (c) Electrode Manufacturing The manufacturing method includes manufacturing an electrode by using an electrode material that has undergone a dry classification process.

[0078] (c1) Preparation of paint The manufacturing method may include, for example, preparing a paint. The paint includes an electrode material. For example, the electrode material in a dry state may be used as the paint itself. For example, a wet powder may be prepared by mixing the electrode material with a solvent. The wet powder may include, for example, granules (aggregates of granulated particles).

[0079] <solvent> The solvent is a liquid. The solvent can promote particle aggregation in the wet powder. The solvent may contain, for example, water, an organic solvent, etc. The solvent may contain a component capable of dissolving the binder. The solvent may contain, for example, at least one selected from the group consisting of water, butyl butyrate, and NMP.

[0080] (c2) Painting This manufacturing method may include, for example, applying a coating material to the surface of the substrate. Any coating method may be used in this manufacturing method. The first and second coating methods described below are merely examples. For example, coating may be performed continuously by a roll-to-roll method. This is expected to improve productivity.

[0081] <Base material> The substrate may be, for example, in the form of a sheet. The substrate may be, for example, an electrode current collector. The substrate may include, for example, a metal foil. The metal foil may include, for example, at least one selected from the group consisting of aluminum (Al), Cu, Ni, titanium (Ti), Cr, and Fe. The substrate may be, for example, an Al foil or a Cu foil. The substrate may have a thickness of, for example, 5 to 50 μm, or 10 to 30 μm.

[0082] <First painting method> 5 is a schematic diagram showing a first coating method. The first coating method is similar to the liquid film transfer method. In the first coating method, the coating material 20 may be, for example, a wet powder. The coating material 20 may have a solid content of, for example, 70 to 90%.

[0083] In the first coating method, three rolls are used. The first roll 2101, the second roll 2102, and the third roll 2103 may be arranged, for example, horizontally. The rotation axes of the rolls are parallel to each other. The arrows on each roll indicate the rotation direction of each roll.

[0084] A first gap AB is formed between the first roll 2101 and the second roll 2102. A second gap BC is formed between the second roll 2102 and the third roll 2103.

[0085] The paint 20 is supplied to the first gap AB. The paint 20 is leveled in the first gap AB to form the active material layer 32. The second roll 2102 transports the active material layer 32 to the second gap BC. The third roll 2103 transports the substrate 31. In the second gap BC, the active material layer 32 is transferred to the substrate 31. That is, an electrode 30 including the active material layer 32 and the substrate 31 can be manufactured.

[0086] <Second painting method> 6 is a schematic diagram showing a second coating method. In the second coating method, electrostatic coating is performed. In the second coating method, the coating material 20 may be, for example, a dry powder. The coating material 20 may have a solid content of, for example, 90 to 100%.

[0087] The first roll 2201, the second roll 2202, and the third roll 2203 have parallel rotation axes. The third roll 2203 may be disposed vertically above the first roll 2201. The power source 2204 forms an electric field between the first roll 2201 and the third roll 2203. The first roll 2201 includes a magnet.

[0088] The paint 20 is supplied to a container 2205. The paint 20 may be stirred in the container 2205. For example, a ferromagnetic material may be mixed with the paint 20 in the container 2205. The paint 20 is attracted to the first roll 2201 by a magnetic force F1 from the first roll 2201. The first roll 2201 transports the paint 20. The squeegee 2206 scrapes off a portion of the paint 20, so that a substantially constant amount of paint 20 is supplied to the gap between the first roll 2201 and the third roll 2203.

[0089] The second roll 2202 conveys the substrate 31. The substrate 31 is fed into the gap between the first roll 2201 and the third roll 2203.

[0090] In the gap between the first roll 2201 and the third roll 2203, an electric field is formed such that the electrostatic force F2 acting on the paint 20 is greater than the magnetic force F1 acting on the paint 20. The paint 20 is pulled away from the first roll 2201 by the electrostatic force F2. The paint 20 is then caused to fly toward the third roll 2203 by the electrostatic force F2. A substrate 31 is supported on the surface of the third roll 2203. The paint 20 adheres to the surface of the substrate 31, thereby forming an active material layer 32. That is, an electrode 30 including the active material layer 32 and the substrate 31 can be manufactured.

[0091] <electrode> In this way, an electrode (raw sheet) can be produced. If the coating material (active material layer) contains a solvent, the electrode may be dried. For example, the active material layer may be fixed to the substrate by applying at least one of pressure and heat to the active material layer.

[0092] Furthermore, the electrodes may be compressed to a predetermined thickness according to the battery design, and the electrodes may be cut into a predetermined planar shape according to the battery design.

[0093] The active material layer may be formed on only one side of the substrate. The active material layer may be formed on both the front and back sides of the substrate. The active material layer may have a thickness of, for example, 10 to 1000 μm. The active material layer may have a thickness of, for example, 50 to 200 μm.

[0094] The active material layer includes an electrode material. That is, the electrode includes an electrode material. The electrode material includes an active material powder. In the electrode, the electrode material may have a magnetic material content of 4 ppm or less. In the electrode, the electrode material may have a Cu content of 1 ppm or less. [Example]

[0095] <First Experiment> The following materials were prepared: Active material powder: LiFePO4 Conductive material: CNT Binder: CMC, SBR Solvent: Water

[0096] <Production Example 1> The content of specific foreign matter (magnetic material, Cu) in the active material powder was measured, and the results are shown in Table 2 below.

[0097] A wet powder was formed by mixing an active material powder, a conductive material, a binder, and a solvent using a planetary mixer. A three-roll mill was prepared. The wet powder was kneaded using the three-roll mill. The solid content of the wet powder was 75% or more.

[0098] An electrode was fabricated using the first coating method (see FIG. 5). A test battery including the electrode was then fabricated. The test battery was a small laminate battery.

[0099] <Production Example 2> A test battery was fabricated in the same manner as in Fabrication Example 1, except that the active material powder was subjected to magnetic separation before forming the wet powder. After the magnetic separation, the content of specific foreign matter in the active material powder was measured. The results are shown in Table 2 below.

[0100] <<Production Example 3>> Test batteries were fabricated in the same manner as in Fabrication Example 1, except that the active material powder was subjected to dry classification before forming the wet powder. After dry classification, the content of specific foreign matter in the active material powder was measured. The results are shown in Table 2 below.

[0101] <Self-discharge test> Four test batteries (N1 to N4) were manufactured for each manufacturing example. A self-discharge test was conducted on each test battery. The results are shown in Table 2 below. "OK" indicates that the voltage drop was 0.7 mV or less. "NG" indicates that the voltage drop was more than 0.7 mV.

[0102] [Table 2]

[0103] "result" There is a tendency for the amount of voltage drop to increase as the content of specific foreign matter increases. Production Example 3 (dry classification treatment) had the lowest content of specific foreign matter. Production Example 3 also had the smallest amount of voltage drop in the self-discharge test.

[0104] <Second Experiment> A classification system was prepared. The classification system included a classification device and a detection device. The detection device was configured to detect breakage of the mesh screen by monitoring at least one of the operating sound of the classification device and the torque of the motor.

[0105] <<Production Example 4>> In Production Example 4, the classifier was operated for 6 hours with the detector inactive (OFF state). The content of specific foreign matter was measured for each of the active material powders after 1 hour of treatment, 3 hours of treatment, and 6 hours of treatment. The results are shown in Table 3 below.

[0106] Example 5 In Production Example 5, the classifier was operated for 6 hours with the detector activated (ON state). When the detector detected damage to the screen mesh, the classifier was stopped, the active material powder being processed was discharged, and the screen mesh was replaced. After the active material powder was replaced and the screen mesh was replaced, the operation of the classifier was resumed. The content of specific foreign matter was measured for each of the active material powders after 1 hour of processing, 3 hours of processing, and 6 hours of processing. The results are shown in Table 3 below.

[0107] [Table 3]

[0108] "result" By detecting damage to the screen mesh, the quality (content of specific foreign matter) tends to remain stable over a long period of time.

[0109] <Additional Notes> This embodiment also supports the "method for manufacturing an electrode material." The method for producing the electrode material includes the following steps (a) and (b). (a) An electrode material containing an active material powder is prepared. (b) The electrode material is subjected to dry classification treatment using a classification device to produce an electrode material. The classification device includes a mesh screen, a blade, and a motor. The mesh screen has a cylindrical outer shape. The mesh screen is electrically insulating. The mesh screen is configured to separate coarse particles from the electrode material. The motor is configured to rotate the blade along the inner circumferential surface of the mesh screen. The blade is configured to press the electrode material against the mesh screen. The above (b) includes detecting breakage of the mesh screen by monitoring at least one of the operating sound of the classification device and the torque of the motor.

[0110] The present embodiment and examples are illustrative in all respects. The present embodiment and examples are not limiting. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and examples and that they may be combined in any desired manner. [Explanation of symbols]

[0111] 10 powder material, 11 fine particles, 12 coarse particles, 20 paint, 30 electrode, 31 substrate, 32 active material layer, 100 classification device, 110 housing, 111 main body, 112 supply section, 113 first discharge section, 114 second discharge section, 120 mesh screen, 130 blade, 140 rotor, 141 screw section, 150 motor, 151 shaft, 200 detection device, 300 control device, 1000 classification system, 2101, 2201 first roll, 2102, 2202 second roll, 2103, 2203 third roll, 2204 power supply, 2205 container, 2206 squeegee, AB first gap, BC second gap, F1 magnetic force, F2 electrostatic force.

Claims

1. (a) providing an electrode material including an active material powder; (b) subjecting the electrode material to a dry classification treatment using a classification device; and (c) producing an electrode by using the electrode material that has been subjected to (b); Including, The classifying device includes a mesh screen, a blade, and a motor; The mesh screen has a cylindrical outer shape, the mesh screen is electrically insulating; the mesh screen is configured to separate coarse particles from the electrode material; The motor is configured to rotate the blade along an inner circumferential surface of the mesh screen, the blade is configured to press the electrode material against the mesh screen; (b) includes detecting breakage of the mesh screen by monitoring torque of the motor; (b) includes determining that the damage has occurred when the torque falls outside a reference range; In the step (b), when the breakage of the mesh screen is detected, the electrode material in the classification device is not used to manufacture the electrode. Electrode manufacturing method.

2. The electrode material includes a conductive material. A method for manufacturing the electrode according to claim 1.

3. The (c) is (c1) preparing a paint containing the electrode material; and (c2) applying the coating material to the surface of a substrate; Including, The coating material contains, in addition to the electrode material, at least one selected from the group consisting of a conductive material, a solid electrolyte, a binder, an additive, and a solvent. The method for manufacturing the electrode according to claim 1 or 2.

4. The coating material has a solid content of 70 to 100% by mass. The method for manufacturing the electrode according to claim 3 .

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