Method for producing electrode dispersion

Abstract

To provide a manufacturing method for electrode dispersion elements, capable of implementing: dispersion element performance that is stable viscosity without gelation; coating performance for suppressing band occurrence and the like at the time of coating; and battery performance of uniform quality of the dispersion elements for withstanding repeated charging / discharging for a long period of time, eliminating variation in quality of respective produced batteries, and inhibiting a failure due to the generation of gas.SOLUTION: A manufacturing method for electrode dispersion elements of the present invention includes: a mixing step (first step) S1 of mixing at least a solvent, binding material, conductive material, and active material; a dispersion step (second step) S2 with no input of material; and a dispersion step (third step) S3 with no input of material, where a dispersion condition differs from that of the second step. In the first step S1, the solvent is input to a mixer before inputting the binding material and the conductive material and, after the binding material and the conductive material are input, the active material is input. Environments from the first step S1 to the third step S3 have temperatures at least equal to or lower than dew point temperature -25°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an electrode dispersion used in electrodes of lithium ion secondary batteries and the like. [Background technology]

[0002] Conventionally, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are required to have battery performance that can withstand repeated charge and discharge over a long period of time. As one attempt to ensure such battery performance, studies have been conducted on the manufacturing methods of electrodes.

[0003] For example, Patent Document 1 discloses a method for producing a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material, the method including a step of producing an electrode slurry for producing the positive electrode and the negative electrode, the step of producing the electrode slurry including at least a first step of mixing the positive electrode active material or the negative electrode active material with a conductive additive and a non-aqueous solvent, and a second step of diluting or concentrating the slurry obtained in the first step and kneading the diluted slurry to produce an electrode slurry, the first step comprising mixing the materials so that the resulting slurry has a water content of 1000 ppm or less and a viscosity of 500 cP to 8000 cP, and the second step comprising kneading the materials so that the water content of the resulting electrode slurry is maintained at the water content of the slurry after the first step. The method also proposes a technique for suppressing chemical damage to the active material due to gelation and mixing by controlling the water content and viscosity of the slurry in the first and second steps. However, in Patent Document 1, there is a concern that moisture in the air will be absorbed into the slurry even in a low dew point environment due to the frequent opening and closing of the mixing device from the first step to the second step. Even if the moisture contained in the slurry is removed by utilizing heating or decompression, the active material is irreversibly altered by the moisture in an extremely short time, and therefore chemical damage to the active material caused by the moisture cannot be reliably suppressed.

[0004] Patent Document 2 proposes a method for producing an electrode paint for lithium-ion secondary batteries or capacitors, which is a mixture of materials containing powder and a solvent, comprising: a pre-stirring step of pre-stirring the materials; a high-speed stirring step of supplying the intermediate material obtained in the pre-stirring step to a high-speed stirrer having a container and a rotating member that rotates at high speed just inside the inner wall surface of the container, and continuously stirring the intermediate material that has been caused to exist in a film-like form between the rotating member and the inner wall surface by the centrifugal force of the rotating member; and a vacuum degassing step of introducing the stirred material obtained in the high-speed stirring step into a processing tank equipped with stirring blades and performing a vacuum degassing process.The method proposes a method for producing a paint, which eliminates or simplifies the step of removing aggregates and the like by continuously supplying the intermediate material that has undergone the storage step to the high-speed stirrer. However, in Patent Document 2, the preliminary mixing step is a batch process, which can cause material to adhere to the large-diameter mixing blades rotating at low speed or to the top of the container, potentially preventing the production of a uniform slurry with the intended composition. Furthermore, the inventors have confirmed that agglomerates and the like cannot be reliably removed by mixing with a high-speed mixer. Furthermore, the document does not mention the effect of moisture absorption by the slurry during the process.

[0005] Furthermore, Patent Document 3 discloses a method for producing an electrode slurry, which includes a mixing step of feeding an electrode active material powder and a binder powder into a mixing device and mixing them, and a kneading step of feeding a solvent into the mixing device after the mixing step and kneading a powder material containing the electrode active material powder and the binder powder, characterized in that in the mixing step, the binder powder is fed into the mixing device, and then the electrode active material powder is fed into the mixing device.The method proposes a method in which the binder is mixed using a batch method, and then an active material that has a high specific gravity and is to be mixed in a large amount is added, thereby suppressing the generation of lumps in the binder and avoiding the generation of streaks on the electrode surface and the need for a long kneading time to eliminate the lumps. However, in Patent Document 3, the kneading process is a batch process, so it is not possible to prevent the material from adhering to areas where kneading does not occur, such as the upper part of the container, and it is not possible to reliably remove agglomerates, etc. In addition, it takes time to adjust the viscosity during kneading, and because the container is opened and closed to remove the material from the upper part of the container, as described above, there is a problem that the slurry is prone to absorbing moisture even in a low dew point environment. Furthermore, because the removal of the material from the upper part of the container is done by hand, there is also the problem that the slurry is significantly affected by moisture generated by the person. Furthermore, there is no mention of the effect of moisture absorption by the slurry during the process.

[0006] Furthermore, Patent Document 4 discloses a method for producing a composite slurry containing an active material, a polyvinylidene fluoride resin, a good solvent for the polyvinylidene fluoride resin, and a conductive carbon material, which is characterized by sequentially performing the following steps: a first step of mixing the active material and the polyvinylidene fluoride resin to produce a mixed powder; a second step of adding the mixed powder to a good solvent for the polyvinylidene fluoride resin to simultaneously dissolve the polyvinylidene fluoride resin and disperse the active material, thereby producing a dispersion solution; and a third step of adding a conductive carbon material to the dispersion solution and kneading to produce a composite slurry.The method proposes a method in which the active material is mixed with the polyvinylidene fluoride resin as a binder, and the mixture is added to a solvent, thereby dispersing the active material and rapidly dissolving the polyvinylidene fluoride resin, and preventing any undissolved binder from remaining. However, Patent Document 4 requires a process of mixing the active material and the binder polyvinylidene fluoride resin in powder form in advance, which means that the active material and binder are in the form of powder with a large specific surface area and are exposed to the atmosphere for a long period of time, which causes a problem in that they are significantly affected by moisture absorption even in a low dew point environment.Furthermore, there is no mention of the effect of moisture absorption by the slurry during the process. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2017 / 188043 (Claims, Examples, etc.) [Patent Document 2] International Publication No. 2010 / 018771 (Claims, Examples, etc.) [Patent Document 3] JP 2015-141737 A (claims, examples, etc.) [Patent Document 4] JP 2013-196804 A (claims, examples, etc.) Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention seeks to solve the above-mentioned conventional problems, and aims to provide a method for manufacturing a dispersion for electrodes that achieves the following battery performance: dispersion performance with stable viscosity without gelation, coating performance that suppresses the occurrence of streaks during coating, and uniform dispersion quality that allows the battery to withstand repeated charge and discharge over long periods of time, with no variation in quality between batteries produced, and no defects due to gas generation. [Means for solving the problem]

[0009] As a result of intensive research into the above-mentioned conventional problems, the inventors have discovered that the above-mentioned objective method for producing an electrode dispersion can be obtained by the following first to fifteenth inventions, and have thus completed the present invention.

[0010] That is, the first invention is a method for producing an electrode dispersion, which includes a mixing step (first step) of mixing at least a solvent, a binder, a conductive material, and an active material, a dispersion step (second step) that does not involve the addition of any materials, and a dispersion step (third step) that does not involve the addition of any materials and has dispersion conditions different from those of the second step, wherein in the first step, the solvent is added to a mixing device, and then the binder and the conductive material are added, and after the binder and the conductive material are added, the active material is added, and the environment from the first step to the third step is at least −25° C. dew point temperature or lower.

[0011] The second invention is a method for producing a dispersion for an electrode according to the first invention, characterized in that it includes a vacuum degassing step (fourth step) that does not involve the addition of any material.

[0012] The third invention is a method for producing the electrode dispersion according to the first or second invention, characterized in that it includes a filtration step (fifth step) of filtering through a filter having a pore size of 10 μm to 50 μm.

[0013] The fourth invention is a method for producing the electrode dispersion according to the third invention, characterized in that a filter is used that has been dried for 3 hours or more in an environment with a dew point temperature of -25°C or lower, or that is made of a material that does not have a hydrophilic group in the liquid-contacting part.

[0014] The fifth invention is a method for producing a dispersion for an electrode according to any one of the first to fourth inventions, characterized in that the water content of the solvent is 200 ppm or less.

[0015] The sixth invention is a method for producing a dispersion for an electrode according to any one of the first to fifth inventions, characterized in that the viscosity of the dispersion in the first step is 8000 mPa·s or less.

[0016] The seventh invention is the method for producing a dispersion for an electrode according to the sixth invention, characterized in that the conductive material is added after the binder is added.

[0017] The eighth invention is a method for producing an electrode dispersion according to any one of the first to seventh inventions, characterized in that after the active material is added, the pressure is reduced to an absolute pressure of 20 kPa or less.

[0018] The ninth invention is a method for producing a dispersion for an electrode according to any one of the first to eighth inventions, characterized in that after the conductive material is added, the absolute pressure is reduced to 20 kPa or less.

[0019] The tenth invention is a method for producing a dispersion for an electrode according to any one of the first to ninth inventions, characterized in that after the binder is added, the pressure is reduced to an absolute pressure of 20 kPa or less.

[0020] The eleventh invention is a method for producing a dispersion for an electrode according to any one of the first to tenth inventions, characterized in that the active material is a lithium-nickel composite oxide.

[0021] The twelfth invention provides a method for producing a lithium-nickel composite oxide, comprising the steps of: X M1 Y M2 Z A method for producing a dispersion for an electrode according to the eleventh invention, characterized in that M1 and M2 are at least one metal element selected from the group consisting of Al, B, alkali metals, alkaline earth metals, and transition metals, and 0.8≦X≦1.0, 0≦Y≦0.2, and 0≦Z≦0.2.

[0022] The 13th invention is a method for producing a dispersion for an electrode according to any one of the first to 12th inventions, characterized in that the solid content concentration of the dispersion is 40% by mass or more and 90% by mass or less.

[0023] The 14th invention is a method for producing a dispersion for an electrode according to any one of the 1st to 13th inventions, characterized in that the median diameter (D50) of the dispersion calculated on a volume basis by laser diffraction method is 5 μm or more and 15 μm or less.

[0024] The fifteenth invention is a method for producing a dispersion for an electrode according to any one of the first to fourteenth inventions, characterized in that the environmental dew point temperature is -30°C or lower.

[0025] In this specification, the term "dew point temperature (dp)" refers to the temperature at which, when air containing water vapor is cooled, the relative humidity reaches 100%, reaching saturation, and part of the water vapor condenses to form dew. Furthermore, the term "environmental dew point" refers to the dew point temperature of the atmosphere in contact with the electrode dispersion or the raw materials that make up the electrode dispersion, and refers to the gas phase in a tank or mixer. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a method for manufacturing an electrode dispersion that achieves the following battery performance: dispersion performance with stable viscosity without gelation; coating performance that suppresses the occurrence of streaks during coating; and uniform dispersion quality that allows the battery to withstand repeated charge and discharge over a long period of time, with no variation in quality between batteries produced, and no defects due to gas generation. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is an explanatory diagram showing, in a flow chart form, each step for explaining an example of a method for producing an electrode dispersion of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following describes in detail the embodiments of the present invention. However, please note that the technical scope of the present invention is not limited to the embodiments described in detail below, but extends to the inventions set forth in the claims and their equivalents. Furthermore, the present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field (including design matters and obvious matters). FIG. 1 is an explanatory diagram showing, in a flow chart form, each step for explaining an example of a method for producing an electrode dispersion of the present invention.

[0029] The method for producing an electrode dispersion of the present invention includes, for example, a mixing step (first step: S1) of mixing at least a solvent, a binder, a conductive material, and an active material, a dispersion step (second step: S2) that does not involve the addition of any materials, and a dispersion step (third step: S3) that does not involve the addition of any materials and has dispersion conditions different from those of the second step, as shown in Figure 1, and is characterized in that in the first step, the solvent is added to a mixing device, followed by the addition of the binder and the conductive material, and after the addition of the binder and the conductive material, the active material is added, and the environment from the first step S1 to the third step S3 is at least -25°C or lower in dew point temperature.

[0030] In the present invention, in order to achieve the effects of the present invention, at least the first step S1 to the third step S3 are carried out in an environment with a dew point temperature of -25°C or lower. If the environment in the first step S1 to the third step S3 has a dew point temperature above -25°C (for example, -24°C or -20°C), the solvent will suddenly absorb moisture, which will make it easier for gelation and deterioration due to chemical damage to the active material to progress, and the effects of the present invention will not be fully achieved, which is undesirable. It is more preferable that the environmental dew point in the first step S1 to the third step S3 for producing the electrode dispersion is at least −25° C. or lower, and more preferably −30° C. or lower. As long as it is −25° C. or lower, the lower the dew-point temperature, including the environmental dew point, the better. However, from the perspective of the cost of creating a dry environment, the dew-point temperature, including the environmental dew point, may be −80° C. or higher, −75° C. or higher, −70° C. or higher, −65° C. or higher, −60° C. or higher, −55° C. or higher, −50° C. or higher, or −45° C. or higher.

[0031] In a situation where the electrode dispersion or the raw materials constituting the electrode dispersion are exposed to the atmosphere outside the mixing device or dispersing device in the first step S1 to the third step S3, the dew point temperature in the room must also be controlled to at least −25° C. or less. In this specification, the dew point temperature was measured using an online dew point meter TK-100 (manufactured by Techne Measurement Co., Ltd.).

[0032] The mixer used in the mixing step (first step) of mixing at least the solvent, binder, conductive material, and active material is not particularly limited, and may be a known mixer such as a planetary mixer, a combimix, a conical mixer, a kneader, a planetary mixer, a centrifugal mixer, a Henschel mixer, etc. These mixers are preferably designed to be able to reduce the pressure to an absolute pressure of 20 kPa or less using a vacuum pump, in view of the need to reliably wet the charged materials with the solvent in a short time and the need to remove any air bubbles generated during charging.

[0033] Furthermore, the stirring blades inside each of the mixers described above, which are used to uniformly mix the electrode dispersion and the raw materials that make up the electrode dispersion, can be designed to be reverse-rotatable to achieve even greater uniformity. By rotating in reverse, it is possible to reduce the frequency with which the sealed mixer is opened to expose the electrode dispersion and the raw materials that make up the electrode dispersion to the atmosphere outside the mixer. In addition to being reverse-rotatable, the stirring blades can also be designed to vibrate or move up and down while remaining sealed.

[0034] The dispersing machine used in the dispersing step (second step) S2, which does not involve the addition of any materials, and the dispersing step (third step) S3, which does not involve the addition of any materials and has dispersion conditions different from those of the second step S2, which follows the first step S1, is not particularly limited, and known machines such as a planetary mixer, a combimix, a kneader, a planetary mixer, a centrifugal mixer, a Henschel mixer, a ball mill, a bead mill, a high-pressure homogenizer, and a thin film rotary high-speed agitator can be used.

[0035] In the second step S2 and the third step S3, the electrode dispersion absorbs the moisture present outside the disperser, so no new raw materials are added. Adding raw materials will introduce a large amount of moisture present on or near the surface of the raw materials into the disperser, which is undesirable. Naturally, it is preferable that the dispersers in the second step S2 and the third step S3 and the piping and tanks that constitute the dispersers have a sealed structure that is isolated from the outside. When an open section is provided, dry air with a dew point temperature of -25°C or lower is supplied into the disperser so that the pressure inside the disperser becomes positive relative to the pressure outside the disperser. The positive pressure may be 1 Pa or more, 2 Pa or more, 3 Pa or more, 4 Pa ​​or more, 5 Pa or more, 6 Pa or more, 7 Pa or more, 8 Pa or more, 9 Pa or more, 10 Pa or more, 15 Pa or more, or 20 Pa or more, and may be 100,000 Pa or less, 90,000 Pa or less, 80,000 Pa or less, 70,000 Pa or less, 60,000 Pa or less, 50,000 Pa or less, 40,000 Pa or less, 30,000 Pa or less, 20,000 Pa or less, 10,000 Pa or less, 5000 Pa or less, 3000 Pa or less, 1000 Pa or less, 500 Pa or less, 300 Pa or less, 200 Pa or less, 100 Pa or less, 80 Pa or less, 60 Pa or less, 50 Pa or less, 40 Pa or less, or 30 Pa or less. If the positive pressure is less than 1 Pa, there is a risk that the outside air will flow into the inside of the disperser, while if the positive pressure is greater than 100,000 Pa, there is a risk that the shaft seal of the disperser will be adversely affected.

[0036] It is necessary to open the disperser in the second step S2 and the third step S3 and some of the piping and tanks that constitute the disperser, and when the inside of the disperser is brought into contact with the outside atmosphere, it is preferable to maintain the positive pressure. Also, in case it is not possible to maintain the positive pressure when the disperser is opened, it is preferable to provide valves for shutting off the flow at multiple locations from the upstream to downstream of the flow of the electrode dispersion in the second step S2 and the third step S3. The intervals at which the valves are installed may be 4 times or more, 8 times or more, 16 times or more, or 24 times or more the inner diameter of the pipe, or 200 times or less, 100 times or less, or 50 times or less. Known valves such as ball valves, diaphragm valves, and butterfly valves can be used, but diaphragm valves and butterfly valves, which have a structure that prevents the contents from stagnating, are preferred, and diaphragm valves with low pressure loss are more preferred. If the intervals at which the valves are installed are small, a large number of valves must be installed, which is undesirable in terms of cost and maintenance, and if the intervals are large, there is a risk that more water will flow into the disperser if the positive pressure cannot be maintained.

[0037] In the production of the electrode dispersion of the present invention, as shown in Figure 1, a vacuum degassing step (fourth step: S4) that does not involve the addition of any materials can be included after the dispersion step S3 in order to further enhance the effects of the present invention. The vacuum degassing machine used in this fourth step S4 can be any known machine, such as a planetary mixer, a combimix, an anchor mixer, a planetary ...

[0038] Preferably, the method further includes a filtration step (fifth step: S5) of filtering the mixture using a filter having a pore size of 10 μm to 50 μm after the vacuum degassing step (fourth step: S4). The filter used in the fifth step S5 may be made of a known material such as polytetrafluoroethylene, nylon, glass, polypropylene, or polyethylene, and is not particularly limited as long as it is not eluted in the solvent contained in the electrode dispersion. The filter may be a known type such as a cartridge type, a sheet-fed type, a bag type, or a cross-flow type, and is not particularly limited.

[0039] The pore size of the filter may be 10 μm or more, more preferably 12 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, or 25 μm or more, with the upper limit being 50 μm or less, more preferably 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, or 25 μm or less. Pore sizes smaller than 10 μm are undesirable because they increase the frequency of filter replacement due to clogging and increase the amount of water absorbed by the electrode dispersion from the filter. On the other hand, pore sizes greater than 50 μm are insufficient to remove coarse aggregates, resulting in reduced yields in the coating process. The pore size of the filter is defined as the particle size of the reference particle whose particle count after the filter is 20% of the particle count before the filter, i.e., closest to 80% collection efficiency, when water containing reference particles is passed through the filter at a constant flow rate and the particle counts before and after the filter are measured using a particle counter.

[0040] The filter is preferably made of a material that does not contain a hydrophilic functional group in the liquid-contacting portion, and is particularly preferably made of polytetrafluoroethylene, polypropylene, or polyethylene, with polypropylene and polyethylene being preferred from the viewpoints of cost and moisture content.

[0041] It is also preferable that the filter has a material that does not contain a hydrophilic functional group in the liquid-contacting portion and / or is dried in advance in an environment with a dew point temperature of −25° C. or lower. The drying time may be 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, 12 hours or more, 24 hours or more, 48 hours or more, 72 hours or more, 168 hours or more, or 400 hours or more. In the case of filters made of materials with hydrophilic functional groups, the drying time may be 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, 12 hours or more, 24 hours or more, 48 hours or more, 72 hours or more, 168 hours or more, or 400 hours or more. If the drying time is short, it may not be possible to sufficiently remove moisture adsorbed or contained in the filter material. On the other hand, if the drying time is long, the moisture removal efficiency will gradually decrease and the storage space will be constrained.

[0042] In the present invention, examples of materials constituting the electrode dispersion include various materials used for electrodes of lithium ion batteries and the like, including at least solvents, binders, conductive materials, and active materials. For example, the following can be used:

[0043] (solvent) Examples of solvents include 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, and amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. Hereinafter, N-methyl-2-pyrrolidone may be referred to as "NMP." These solvents may be used alone or in combination. The amount of these solvents is preferably 25 to 100 parts by mass, more preferably 40 to 70 parts by mass, per 100 parts by mass of the active material, in view of the need to achieve an appropriate viscosity when applying the electrode dispersion.

[0044] In order to further enhance the effects of the present invention, the water content of each of the above solvents is desirably 1000 ppm or less, more preferably 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, and particularly preferably 200 ppm or less. When two or more solvents are used in combination, the water content of the entire mixed solvent is controlled to the above-mentioned level. Water contained in the solvent can also be removed using known methods, such as adsorption removal using molecular sieves or distillation removal using an alkali metal and benzophenone.

[0045] (binding material) Examples of binders include fluororesins such as polyimide resins, polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers, and tetrafluoroethylene-perfluorovinyl ether copolymers, and polyolefin resins such as polyethylene and polypropylene. Two or more of these binders may be mixed together. These binders may also be used after being dissolved and / or dispersed in a solvent. It is also preferable to store the powder or packaging material in an atmosphere with a dew point temperature of −25°C or below before use to remove moisture from the powder or packaging material. Adherent moisture can also be forcibly removed using known methods such as vacuum drying or hot air drying. Hereinafter, polyvinylidene fluoride may be referred to as PVdF. The amount of these binders is preferably 0.2 to 3.0 parts by mass, and more preferably 0.5 to 2.5 parts by mass, per 100 parts by mass of active material, from the viewpoints of adhesion to the current collector foil, battery capacity after cell formation, and charge / discharge characteristics.

[0046] (Conductive material) Examples of conductive materials that can be used include carbon materials and metal compounds. Examples of carbon materials include graphite powder, carbon black (e.g., acetylene black), and fibrous carbon materials (e.g., multi-walled carbon nanotubes). These conductive materials can also be used after being dissolved and / or dispersed in a solvent. It is also preferable to store the conductive materials in an atmosphere with a dew point temperature of −25° C. before use to remove moisture adhering to the powder and packaging material. Adhering moisture can also be forcibly removed using known methods such as vacuum drying and hot air drying. The amount of these conductive materials is preferably 0.5 to 10.0 parts by mass, more preferably 1.0 to 6.0 parts by mass, per 100 parts by mass of the active material, from the viewpoint of battery capacity and charge / discharge characteristics after cell formation.

[0047] (active material) The active material is preferably a positive electrode active material, and is not particularly limited as long as it is a common positive electrode active material that can be used for the positive electrode of a lithium ion battery, for example, lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, lithium-nickel-manganese-aluminum composite oxide, lithium-nickel-manganese-aluminum composite oxide, transition metal sulfides such as TiS2, FeS, and MoS2, MnO, V---2O5, and VO 13 Examples of suitable lithium phosphate compounds include transition metal oxides such as TiO2 and olivine-type lithium phosphate compounds. The olivine-type lithium phosphate compounds contain at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe, as well as lithium, phosphorus, and oxygen. These compounds may have some of the elements partially substituted with other elements to improve their properties. A preferred active material is a lithium-nickel composite oxide, and more preferably, the lithium-nickel composite oxide is represented by the formula: LiNi X M1 Y M2 Z A lithium-nickel composite oxide represented by O2 (M1 and M2 are at least one metal element selected from Al, B, alkali metals, alkaline earth metals, and transition metals, 0.8≦X≦1.0, 0≦Y≦0.2, 0≦Z≦0.2) is desirable. These active materials for the positive electrode and the like may be used singly or in combination of two or more. These active materials may be used in a state where they are dissolved and / or dispersed in a solvent in advance. It is also preferable to store the active materials in an atmosphere with a dew point temperature of −25° C. or lower before use to remove moisture adhering to the powder and packaging material. Adhering moisture can also be forcibly removed using known methods such as vacuum drying and hot air drying. When the binder, conductive material, and active material are used in a state of being dissolved and / or dispersed in a solvent in advance, the total amount of the solvent used is, as described above, preferably 25 to 100 parts by mass, more preferably 40 to 70 parts by mass, per 100 parts by mass of the active material. In addition to the above-mentioned solvent, binder, conductive material, and active material, dispersants, leveling agents, solid electrolyte materials, and the like may be appropriately blended within limits that do not impair the effects of the present invention.

[0048] The average particle size and amount of each of the binder, conductive material, active material, etc. are adjusted within the respective predetermined ranges so as to produce a suitable electrode, and are adjusted so as to achieve the preferred average particle size of the particles in the electrode dispersion, viscosity of the dispersion, and solids concentration, which will be described later. These adjustments can be made by suitably combining the type of binder, conductive material, active material, particle size and amount thereof, type of solvent, etc., used, as well as the predetermined processing conditions for the mixing step and dispersion steps (1) and (2). In the present invention, the order in which the solvent, binder, conductive material, and active material are added to the mixer in the first mixing step is, in order to avoid moisture adsorption from the atmosphere onto the powder materials and to ensure uniformity within the mixing vessel, to add the solvent first, then the binder and conductive material, and then the active material, and then mix them. This mixing procedure allows the effects of the present invention to be achieved. However, if the active material is added and mixed before the binder and conductive material are added in the first mixing step, or if the solvent is added and mixed after the binder and conductive material are added, or if the solvent is mixed sequentially in the mixing and dispersing steps, undesirable moisture may be mixed into the electrode dispersion from the atmosphere, or the materials may become non-uniform in the mixing vessel, preventing the effects of the present invention from being achieved. Preferably, the solvent is added, then the binder is added, then the conductive material is added, and then the conductive material is added, and then the active material is added and mixed. In the mixing step of the first step, it is desirable to reduce the absolute pressure to 20 kPa or less each time after adding the binder, the conductive material, or the active material to the mixer into which the solvent has been added. These pressure reduction operations enable the added materials to be reliably wetted by the solvent in a short period of time.

[0049] The total mixing (kneading) time in this mixing step may be adjusted as appropriate so that the active material becomes uniform and has a viscosity value below the following value, and is preferably 0.5 hours or more and 8 hours or less. Furthermore, the dispersion conditions in the dispersion step (second step) S2, which does not involve the addition of any materials after the mixing step S1, include using a planetary mixer, combimix, kneader, planetary mixer, centrifugal mixer, Henschel mixer, ball mill, bead mill, high-pressure homogenizer, thin film rotary high-speed mixer, or the like to uniformly disperse and mix some of the various materials that have formed lumps or aggregated and are not sufficiently wetted or disintegrated, and the dispersion time can be adjusted as appropriate so that the portions of the various materials are sufficiently uniformly dispersed and mixed without deviating from the range of the preferred average particle size. The dispersion conditions in the dispersion step (third step) S3 after the second step S2, which does not involve the addition of materials with different dispersion conditions, are as follows: a planetary mixer, a combimix, a kneader, a planetary mixer, a centrifugal mixer, a Henschel mixer, a ball mill, a bead mill, a high-pressure homogenizer, a thin-film rotary high-speed agitator, etc., are used to uniformly disperse and mix the various materials that remain after the treatment in the dispersion step (second step) S2 and that have become lumpy or aggregated and are insufficiently wetted or disintegrated, and the dispersion time can be adjusted appropriately so that the various materials are sufficiently uniformly dispersed and mixed without deviating from the preferred average particle size range. If the dispersion conditions in the above dispersion steps (1) and (2) are the same, there is a tendency for the coatability and / or quality stability to be inferior due to some materials that do not disperse effectively under the same conditions. After the dispersion step S3, the treatment time in a vacuum degassing machine or the like in a preferred vacuum degassing step (fourth step: S4) that does not involve the addition of any materials is adjusted appropriately so as to obtain a suitable dispersion free of bubbles.

[0050] The viscosity of the dispersion after mixing in the first step (mixing step) is preferably 23,000 mPa·s or less, preferably 10,000 mPa·s or less, more preferably 8,000 mPa·s or less, and particularly preferably 4,000 mPa·s or less. By adjusting the viscosity of the dispersion in the first step to the above viscosities or less, the effects of the present invention can be further enhanced. Here, the "viscosity measurement" refers to the value measured after 1 minute at a shear rate of 38 / s using an E-type rotational viscometer at a liquid temperature of 25°C. The average particle size of the particles in the resulting electrode dispersion may be preferably 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more, from the viewpoint of suppressing side reactions during charge and discharge and suppressing a decrease in charge and discharge efficiency. Furthermore, from the viewpoint of coatability (such as smoothness of the electrode surface), the average particle size may be 30 μm or less, 25 μm or less, or 20 μm or less, preferably 15 μm or less, and particularly preferably 5 μm or more and 15 μm or less. Here, "average particle size" refers to the particle size (median size: D50) at 50% cumulative in the particle size distribution (volume basis) measured by laser diffraction scattering. The measurement was carried out using an MT3300EXII manufactured by Microtrackbell, and the measurement parameters were set as follows: Refractive index of solvent: refractive index of the main solvent of the electrode dispersion at 20° C. In the case of a mixed solvent, the refractive index at 20° C. of the mixed solvent mixed at the ratio of each solvent contained in the electrode dispersion was used. Transmittance: Reflection.

[0051] The solids concentration of the resulting electrode dispersion may preferably be 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, or 65% by mass or more, with an upper limit of 90% by mass or less, 85% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less. If the solids concentration is lower than 40% by mass, drying after coating takes time, resulting in a loss of productivity. If the solids concentration is higher than 90% by mass, uniform coating becomes difficult, resulting in a decrease in yield during the coating process. In the present invention, the "solids concentration" refers to the solids content measured using a halogen moisture meter (manufactured by Mettler-Toledo) at 200°C for 30 minutes.

[0052] The method for producing an electrode dispersion of the present invention, as configured above, includes a mixing step (first step: S1) of mixing at least a solvent, a binder, a conductive material, and an active material, a dispersion step (second step: S2) that does not involve the addition of any materials, and a dispersion step (third step: S3) that does not involve the addition of any materials and that operates under different dispersion conditions from the second step. In the first step, the solvent is introduced into a mixing device, followed by the binder and conductive material. After the binder and conductive material are introduced, the active material is introduced. The environment for the first step S1 through the third step S3 is at least −25° C. dew point temperature or below, thereby producing a dispersion for an electrode (positive electrode) used in a lithium-ion secondary battery or the like. This dispersion is then applied to a positive electrode current collector, which is a conductive member for the positive electrode of a lithium-ion secondary battery, and dried to produce a desired positive electrode for the lithium-ion secondary battery. In the present invention, as shown in FIG. 1, in order to obtain a dispersion for an electrode of even higher quality, a preferred embodiment is to obtain a dispersion for an electrode (positive electrode) by carrying out the above-mentioned vacuum degassing step (fourth step: S4) or the above-mentioned filtration step (fifth step: S5) after the dispersion step (third step: S3), and a more preferred embodiment is to obtain a dispersion for an electrode (positive electrode) by carrying out the above-mentioned vacuum degassing step (fourth step: S4) and the above-mentioned filtration step (fifth step: S5) after the dispersion step (third step: S3). By producing these steps (environments of S1 to S4, environments of S1 to S3 and S5, environments of S1 to S5) at a dew point temperature of −25° C. or less, a dispersion for an electrode (positive electrode) for use in a lithium-ion secondary battery or the like of even higher quality can be obtained.

[0053] According to the method of the present invention configured as described above, at least a solvent, a binder, a conductive material, and an active material are used, and the first step S1 to the third step S3 [the mixing step in the above procedure, and the dispersing steps (1) and (2)] are carried out, and the environment during these steps is maintained at a dew point temperature of at least -25°C or lower. This makes it possible to suppress chemical damage to the binder and active material, and since there are no undissolved binders or aggregates of various materials, the viscosity is stable without gelation, the occurrence of streaks during coating is suppressed, and the quality of the dispersion is uniform. This makes it possible to obtain a method for producing an electrode dispersion that can withstand repeated charge and discharge over a long period of time, has no variation in quality among the batteries produced, and achieves battery performance without defects due to gas generation. [Example]

[0054] The present invention will be described below with reference to examples, but is not limited to these examples. In each of the following examples, the mixing step (first step), dispersing step (1) (second step), dispersing step (2) (third step), vacuum degassing step (fourth step), and filtration step (fifth step) were mainly performed in a sealed structure isolated from the outside, and in a partially open section (such as the space where materials are introduced in the first step), dry air with a dew point temperature of -35°C or lower was supplied into the space to maintain a positive pressure relative to the pressure outside the space where materials are introduced into the mixer, thereby maintaining a dew point temperature of -35°C.

[0055] Example 1 <First step> In an environment with a dew point temperature of -35°C, 45 parts by mass of NMP was added to a planetary mixer as a mixer, and while stirring, 2 parts by mass of PVdF as a binder and 2 parts by mass of acetylene black (manufactured by Denka Co., Ltd.) as a conductive material were added, the pressure was reduced to an absolute pressure of 5 kPa, and processing was carried out for 1 hour. Next, LiNi 0.8 Co 0.1 Mn 0.1 100 parts by mass of O2 was added with stirring, the pressure was reduced to an absolute pressure of 5 kPa, and stirring was continued for 1 hour. The water content of the NMP used here was 100 ppm, and the viscosity after mixing was 3000 mPa·s. A Karl Fischer moisture meter was used to measure the water content of the solvent. Viscosity was measured using an E-type rotational viscometer at a shear rate of 38 / s.

[0056] <Second process> The electrode dispersion obtained in the first step was treated for 5 minutes using a media-less high-speed stirrer at a peripheral speed of 15 m / s.

[0057] <Third step> The electrode dispersion obtained in the second step was treated for 3 minutes using a bead mill under the conditions of zirconia beads of φ1.0 mm and a peripheral speed of 10 m / s.

[0058] <Fourth process> The electrode dispersion obtained in the third step was placed in a planetary mixer and treated for 30 minutes with stirring under a vacuum of 10 kPa absolute pressure.

[0059] <Fifth process> The electrode dispersion obtained in the fourth step was filtered using a polypropylene cartridge filter with a pore size of 25 μm that had been dried for 1 hour in an environment with a dew point temperature of −35° C. The obtained electrode dispersion had an average particle size D50 of 10 μm and a solid content of 70 mass %.

[0060] Example 2 The procedure was the same as in Example 1, except that in the first step, the pressure was reduced once (to an absolute pressure of 5 kPa) after adding the binder, and then the pressure was reduced again (to an absolute pressure of 5 kPa) after adding the conductive material. The viscosity after mixing in the first step was 3100 mPa s. The viscosities and solid contents in the examples and comparative examples are shown in Table 1 below.

[0061] Example 3 An electrode dispersion was produced in the same manner as in Example 1 above, except that the water content of the NMP used was 300 ppm.

[0062] Example 4 An electrode dispersion was produced in the same manner as in Example 1 above, except that the pressure was not reduced after the binder and conductive material were added.

[0063] Example 5 An electrode dispersion was produced in the same manner as in Example 4, except that the pressure was not reduced after the active material was added.

[0064] Example 6 An electrode dispersion was produced in the same manner as in Example 1 above, except that the amount of NMP added was 35 parts by mass.

[0065] Example 7 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the third step, the mixture was treated for 5 minutes using a media-less high-speed stirrer at a peripheral speed of 20 m / s.

[0066] Example 8 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the second step, treatment was carried out for 3 minutes using a bead mill with zirconia beads of 1.0 mm diameter and a peripheral speed of 10 m / s, and in the third step, treatment was carried out for 3 minutes using a bead mill with zirconia beads of 0.5 mm diameter and a peripheral speed of 10 m / s.

[0067] Example 9 LiNi as the active material 0.8 Co 0.15 Al 0.05 An electrode dispersion was produced in the same manner as in Example 1 above, except that O2 was used.

[0068] Example 10 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the fifth step, filtration was carried out using a nylon cartridge filter with a pore size of 25 μm that had been dried in an environment with a dew point temperature of −35° C. for 6 hours.

[0069] Example 11 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the fifth step, filtration was carried out using a nylon cartridge filter with a pore size of 25 μm that had been dried in an environment with a dew point temperature of −35° C. for 1 hour.

[0070] Example 12 An electrode dispersion was produced in the same manner as in Example 1 above, except that the amount of NMP added was 17 parts by mass.

[0071] Example 13 An electrode dispersion was produced in the same manner as in Example 1 above, except that the amount of NMP added was 156 parts by mass.

[0072] Example 14 A dispersion for an electrode was produced in the same manner as in Example 1 above, except that the pore size of the filter used in the fifth step was 10 μm.

[0073] Example 15 An electrode dispersion was produced in the same manner as in Example 1 above, except that the pore size of the filter used in the fifth step was 50 μm.

[0074] Example 16 An electrode dispersion was produced in the same manner as in Example 1 above, except that the fourth step was omitted.

[0075] Example 17 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the third step, treatment was carried out for 9 minutes using a bead mill with zirconia beads of φ1.0 mm and a peripheral speed of 10 m / s.

[0076] (Comparative Example 1) An electrode dispersion was produced in the same manner as in Example 1 above, except that the process was carried out in an environment with a dew point temperature of -20°C.

[0077] (Comparative Example 2) An electrode dispersion was produced in the same manner as in Comparative Example 1 above, except that the fourth step was omitted.

[0078] (Comparative Example 3) An electrode dispersion was produced in the same manner as in Example 1 above, except that in the first step, 12 parts by mass of NMP was added, in the second step, a planetary mixer was used to carry out a kneading treatment for 4 hours while gradually adding NMP to adjust the kneading condition as appropriate at a revolution of 20 rpm, and in the third step, a planetary mixer was used to gradually add NMP as appropriate so that the final solid content would be 70% by mass, and mixing was carried out for 2 hours at a revolution of 30 rpm.

[0079] Comparative Example 4 An electrode dispersion was produced in the same manner as in Example 1 above, except that in the third step, the mixture was treated for 5 minutes using a media-less high-speed stirrer at a peripheral speed of 15 m / s.

[0080] (Comparative Example 5) An electrode dispersion was produced in the same manner as in Example 1 above, except that in the second step, treatment was carried out for 3 minutes using a bead mill with zirconia beads of 1.0 mm diameter and a peripheral speed of 10 m / s.

[0081] (Comparative Example 6) An electrode dispersion was produced in the same manner as in Example 1 above, except that in the first step, the active material was added and the pressure was reduced before the binder and conductive material were added.

[0082] (Comparative Example 7) An electrode dispersion was produced in the same manner as in Example 1 above, except that in the first step, after the binder and conductive material were added, the solvent was added and the pressure was reduced.

[0083] (Comparative Example 8) An electrode dispersion was produced in the same manner as in Example 1 above, except that the production was carried out in an environment with a dew point temperature of -24°C.

[0084] Comparative Example 9 An electrode dispersion was produced in the same manner as in Example 17 above, except that the procedure was carried out in an environment with a dew point temperature of -24°C.

[0085] The electrode dispersions obtained in the above Examples and Comparative Examples were compared and evaluated based on the following evaluation indices (evaluation of viscosity over time, evaluation of coatability, evaluation of 100 cycle retention rate, evaluation of quality stability, and amount of gas generated). The results are shown in Table 1 below.

[0086] (Temporal viscosity evaluation index) The viscosity over time was evaluated according to the following criteria using the formula "(viscosity after 1 week at 25°C / viscosity at time of manufacture) x 100." Measurements were performed using a rheometer MC102 (manufactured by Anton Paar) at a shear rate of 1000 / s. Evaluation criteria: ◎: Within 110% of viscosity at time of manufacture ○: Within 150% of viscosity at time of manufacture △: Within 200% of viscosity at time of manufacture ×: gelation

[0087] (Coatability evaluation index) The coating properties were evaluated by visually counting the number of streaks of 10 mm or more when the resulting dispersion was coated onto aluminum foil at a wet film thickness of 50 μm using a comma coater with a coating width of 300 mm. Evaluation criteria: ◎:1m 2 Less than 1 muscle per ○:1m 2 Less than 10 muscle streaks per △:1m 2 Less than 20 muscle streaks per ×:1m 2 20 or more muscle growths per

[0088] (100 cycle maintenance rate evaluation index) To evaluate the 100-cycle retention rate, five coin secondary batteries were fabricated using the electrode dispersion of the example applied to aluminum foil as the positive electrode, and the average value of the five coin secondary batteries was calculated using the formula "B / A x 100" from the initial discharge capacity (A) and the discharge capacity (B) at the 100th time after 100 charge / discharge cycles at a charge / discharge rate of 1C, and evaluated according to the following criteria. Evaluation criteria: ◎: 98% or more ○: 95% or more △: 85% or more ×: Less than 85% A carbonate-based solvent was used for the electrolyte. A polypropylene separator was used. The negative electrode was made by applying and drying an electrode dispersion consisting of a titanium oxide-based active material, a conductive material, a binder, and a solvent onto aluminum foil.

[0089] (Quality stability evaluation index) The quality stability evaluation was based on the difference (percentage points) between the maximum and minimum values ​​of the five data points for each condition obtained using the 100 cycle maintenance rate evaluation index, and was evaluated according to the following criteria. Evaluation criteria: ◎: Less than 1% point ○: Less than 3% points △: Less than 5% points ×: 5% points or more

[0090] (Gas generation amount evaluation index) To evaluate the amount of gas generation, a 100mm x 200mm five-layer laminated cell was fabricated under the same conditions as the coin secondary battery, and the cell was charged and discharged 100 times at a charge / discharge rate of 1C in a 50°C environment. The amount of gas generated in the laminated cell was evaluated according to the following criteria. The amount of gas was measured using the Archimedes method. The lower the amount of gas generation, the better the performance. Evaluation criteria: ◎: Less than 5cc ○: Less than 10cc △: Less than 30cc ×:30cc or more

[0091] [Table 1]

[0092] The input conditions A1 to D1 for the first step, the dispersion conditions A2 to D2 and C3 for the second and third steps, the dispersion condition E2 for the second step, the dispersion condition F2 for the third step, the filters G to H, and the active materials J and K in Table 1 above are as follows. First step: Input condition A1: Input in the order of solvent → binder / conductive material → active material First step: Input condition B1: Input in the order of solvent → binder → conductive material → active material First step: Input condition C1: Input in the order of solvent → active material → binder and conductive material First step: Input condition D1: Input active material → binder / conductive material → solvent in that order Second and third steps: Dispersion condition A2: One pass through a high-speed mixer (circumferential speed 15 m / s, media-less, processing time 5 minutes) Second and third steps: Dispersion condition B2: One pass through a high-speed mixer (circumferential speed 20 m / s, media-less, processing time 5 minutes) Second and third steps: Dispersion condition C2: One pass through a bead mill (circumferential speed 10 m / s, zirconia beads φ1.0 mm, processing time 3 minutes) Second and third steps: Dispersion condition D2: One pass through a bead mill (circumferential speed 10 m / s, zirconia beads φ0.5 mm, processing time 3 minutes) Second and third steps: Dispersion condition C3: One pass through a bead mill (circumferential speed 10 m / s, zirconia beads φ1.0 mm, processing time 9 minutes) Second step: Dispersion condition E2: Planetary mixer (revolution 20 rpm, processing time 4 hours), main solvent was added appropriately to adjust the degree of mixing. Third step: Dispersion condition F2: The main solvent was added to a planetary mixer (revolution 30 rpm, processing time 2 hours) to dilute the mixture, and then the mixture was passed through a bead mill (circumferential speed 10 m / s, zirconia beads φ1.0 mm, processing time 3 minutes) once. Filter G: Nylon filter, drying time 6 hours Filter H: Nylon filter, drying time 1 hour Filter I: Polypropylene filter, drying time 1 hour Active material J: LiNi 0.8 Co 0.1 Mn 0.1 O2 Active material K: LiNi 0.8 Co 0.15 Al 0.05 O2

[0093] Considering the evaluation results in Table 1 above, it was confirmed that the electrode dispersions of Examples 1 to 17, which are within the scope of the present invention, are excellent in all aspects of battery performance, such as dispersion performance with stable viscosity without gelation, coating performance that suppresses the occurrence of streaks during coating, and battery performance withstands repeated charge and discharge over a long period of time due to uniform dispersion quality, no variation in quality between the batteries produced, and no defects due to gas generation. In contrast, the electrode dispersions of Comparative Examples 1 to 9 could not satisfy the above characteristics. [Industrial Applicability]

[0094] The dispersion obtained by the method for producing a dispersion for an electrode can be suitably used for producing electrodes (positive electrodes) for lithium ion secondary batteries and the like, and can achieve excellent battery performance that can withstand repeated charging and discharging over a long period of time.

Claims

1. A method for producing an electrode dispersion, comprising: a mixing step (first step) of mixing at least a solvent, a binder, a conductive material, and an active material; a dispersion step (second step) not involving the addition of any material; and a dispersion step (third step) not involving the addition of any material and having dispersion conditions different from those of the second step, the first step comprises adding the solvent to a mixing device, then adding the binder and the conductive material, and then adding the binder and the conductive material, and then adding the active material; and the environment from the first step to the third step has a dew-point temperature of at least −25° C. or lower.

2. 2. The method for producing an electrode dispersion according to claim 1, further comprising a vacuum degassing step (fourth step) that does not involve the addition of any material.

3. 3. The method for producing an electrode dispersion according to claim 1, further comprising a filtration step (fifth step) of filtering the dispersion through a filter having a pore size of 10 μm to 50 μm.

4. The method for producing a dispersion for an electrode according to claim 3, characterized in that a filter that has been dried for 3 hours or more in an environment with a dew point temperature of −25° C. or lower and / or a filter made of a material having no hydrophilic group in a liquid-contacting part is used.

5. 5. The method for producing a dispersion for an electrode according to claim 1, wherein the water content of the solvent is 200 ppm or less.

6. 6. The method for producing a dispersion for an electrode according to claim 1, wherein the viscosity of the dispersion in the first step is 8000 mPa·s or less.

7. 7. The method for producing an electrode dispersion according to claim 6, wherein the conductive material is added after the binder is added.

8. 8. The method for producing an electrode dispersion according to claim 1, wherein the pressure is reduced to an absolute pressure of 20 kPa or less after the active material is charged.

9. 9. The method for producing an electrode dispersion according to claim 1, wherein the pressure is reduced to an absolute pressure of 20 kPa or less after the conductive material is added.

10. 10. The method for producing an electrode dispersion according to claim 1, wherein the pressure is reduced to an absolute pressure of 20 kPa or less after the binder is added.

11. 11. The method for producing an electrode dispersion according to claim 1, wherein the active material is a lithium-nickel composite oxide.

Images