Dehydration Method and Apparatus for Paste for Manufacturing Lithium Ion Secondary Batteries

Abstract

Provided are a method and an apparatus for continuously dehydrating a paste for manufacturing a lithium-ion secondary battery and recycling a gas used as a drying gas. A method for dehydrating a paste for manufacturing a lithium-ion secondary battery having a viscosity at 100 °C of 30 mPa·s or more and less than 5,000 mPa·s, wherein the paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a constituent component of a solid content, and contains an organic solvent having a boiling point higher than that of water or having an azeotropic point with water as a dispersion medium, the paste and a drying gas for removing moisture from the paste are brought into contact with each other in a countercurrent or a cross-flow, moisture contained in the paste volatilizes to the gas side from a gas outlet and a gas containing moisture is discharged, and a paste dehydrated to moisture within a range of 1×10 -7 to 1×10 -4 is discharged from a paste outlet. The present invention relates to a method and an apparatus for dehydrating a paste for manufacturing a lithium-ion secondary battery.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for dehydrating a paste for manufacturing a lithium-ion secondary battery. Specifically, it relates to a method and apparatus for dehydrating a paste used in manufacturing a positive electrode, a negative electrode, a solid electrolyte layer, etc. of a lithium-ion secondary battery.

Background Art

[0002] When manufacturing the positive electrode of a lithium-ion secondary battery by a wet process, there is a step of coating a positive electrode paste containing a positive electrode material on a metal foil. The positive electrode paste contains a binder resin for bonding to the metal foil, and polyvinylidene fluoride (PVDF) is mainly used. In a paste containing polyvinylidene fluoride, especially when a basic substance is contained, there is a problem that the paste becomes highly viscous and gels during storage, and it has been suggested that this may be promoted by the presence of moisture (Patent Document 1).

[0003] Also, in a lithium-ion secondary battery, an electrolyte using a flammable organic solvent or the like in a diluting solvent has been conventionally used as a medium for moving ions. However, in a battery using such an electrolyte, there is a possibility of problems such as leakage of the electrolyte, ignition, and explosion. To solve such problems, development of an all-solid-state lithium-ion secondary battery that uses a solid electrolyte instead of a liquid electrolyte and has all other elements composed of solids has been underway. Since the all-solid-state lithium-ion secondary battery has a very small charge transfer resistance between the solid electrolyte and lithium ions, the internal resistance of the battery can be reduced. Also, since the electrolyte is solid, there is little concern about ignition or fire, it does not leak, and problems such as deterioration of battery performance due to corrosion are less likely to occur. As a solid electrolyte material used for such a solid electrolyte layer, sulfide-based solid electrolyte materials are known. Since sulfide-based solid electrolytes generate hydrogen sulfide, which is toxic due to its reaction with water, strict low-moisture management is required as the moisture value of the solid content when in use. The inventors previously developed a method of evaporating the moisture in a dispersion by bringing it into gas-liquid contact by blowing a dry inert gas into a heated carbonaceous material dispersion shown in Patent Document 2 while stirring, but the above operation is carried out in a batch manner and is not suitable for continuous operation. In a batch process, it is necessary to increase the size of the apparatus to increase the production volume, and also, since the heat history due to heating becomes longer, the conductive auxiliary agent added to the paste may be denatured, affecting the stability of the paste. Also, since it is a method of ventilating gas through the paste, as the batch capacity increases, the contact efficiency between the gas and the paste decreases, resulting in an increase in the amount of dry inert gas used and an increase in the exhaust gas treatment load.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above problems, an object of the present invention is to provide a method and an apparatus for continuously dehydrating a paste for manufacturing a lithium-ion secondary battery and recycling the gas used as the dry gas.

Means for Solving the Problems

[0006] As a result of intensive research and deliberation to solve the above problems, the inventors have invented a method and an apparatus for continuously dehydrating a paste and recycling the gas used as the drying gas. The gas continuously flows in a countercurrent or crossflow manner with the paste in multiple stages or at a distance where the paste and the gas can sufficiently contact each other. Compared with batch operation, the amount of aeration gas per unit mass of the paste can be reduced to less than 60 L per 1 kg of the paste, and the moisture content of the paste can be reduced to 3×10 -5 or less in terms of mass fraction. To further improve the dehydration efficiency, based on the vapor-liquid equilibrium relationship between the moisture contained in the paste and the volatile organic solvent constituting the paste, the temperature, pressure, and required distance necessary for dehydration were estimated, and dehydration was performed under those conditions, thereby constructing a paste dehydration system capable of dehydrating the paste to the required moisture content within the range of 1×10 -7 to 1×10 -4 in terms of mass fraction.

[0007] That is, the present invention for solving the above problems is a method for dehydrating a paste for manufacturing a lithium-ion secondary battery, wherein the paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a constituent of the solid content, and contains an organic solvent having a boiling point higher than that of water or having an azeotropic point with water as a dispersion medium, and further has a viscosity at 100 °C of 30 mPa·s or more and less than 5,000 mPa·s, the paste and a drying gas for removing moisture from the paste are brought into contact in multiple stages in a countercurrent or crossflow manner, and the moisture contained in the paste volatilizes to the gas side and the gas containing moisture is discharged from the gas outlet, and the paste dehydrated to a moisture content within the range of 1×10 -7 to 1×10 -4 in terms of mass fraction is discharged from the paste outlet. This is a method for dehydrating a paste for manufacturing a lithium-ion secondary battery.

[0008] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is shown that the organic solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone, butyl butyrate, pentyl butyrate, hexyl butyrate, xylene, mesitylene, and heptane.

[0009] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that the variation in the non-volatile content of the dehydrated paste is 0.5 mass% or less.

[0010] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that the temperature of the paste to be supplied is in the range of 20 to 100°C, and the system internal pressure during the dehydration operation is in the range of 5 to 105 kPa.

[0011] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that the discharged gas can have its moisture value reduced to less than -10°C dew point under atmospheric pressure by at least one method of cooling, pressurization by a compressor, and adsorption, and a part or all of it can be recycled.

[0012] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that when the paste is brought into contact with the drying gas, at least one fluid of the paste and the drying gas is caused to flow and come into contact by kinetic energy such as centrifugal force.

[0013] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that the moisture value of the discharged gas after dehydration is analyzed by an in-line gas analyzer to confirm the moisture value of the paste after dehydration.

[0014] In one embodiment of the method for dehydrating the paste for manufacturing a lithium ion secondary battery of the present invention, it is also shown that the flow state of the paste and the flow rate of the drying gas are controlled by feedback control from the moisture value to dehydrate the paste to a target moisture value.

[0015] In one embodiment of the method for dehydrating the paste for manufacturing a lithium-ion secondary battery of the present invention, it is also shown that an inert gas such as nitrogen gas is used as the drying gas.

[0016] The present invention for solving the above problems is also a dehydration device for a paste for manufacturing a lithium-ion secondary battery having a viscosity at 100 ° C of 30 mPa·s or more and less than 5,000 mPa·s, The paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a solid content as a constituent component, and as a dispersion medium, it contains an organic solvent having a boiling point higher than that of water or having an azeotropic point with water, A dehydration device for a paste for manufacturing a lithium-ion secondary battery, characterized in that the paste and a drying gas for removing moisture from the paste are brought into contact in multiple stages in a countercurrent or cross-flow manner.

[0017] In one embodiment of the dehydration device for a paste for manufacturing a lithium-ion secondary battery of the present invention, it is shown that it has a centrifugal gas-liquid contact device as a structure in which the contact between the paste and the drying gas is brought into contact in multiple stages in a countercurrent or cross-flow manner.

Effects of the Invention

[0018] According to the present invention, it is possible to provide a paste for manufacturing a lithium-ion secondary battery with low moisture quickly and by a simple method without requiring a pretreatment step or additives or consumables that are difficult to separate and remove, and without impairing the stability of the dispersion. Further, making the paste for manufacturing a lithium-ion secondary battery low in moisture can contribute to improving the stability and characteristics of the dispersion. Furthermore, in terms of quality control, the quality of the paste moisture value is ensured by analyzing the exhaust gas rather than the paste itself. Moreover, the low-moisture paste for manufacturing a lithium-ion secondary battery thus obtained can suppress the occurrence of gelation in the lithium-ion secondary battery and suppress the generation of hydrogen sulfide from the sulfide solid electrolyte in the all-solid-state lithium-ion secondary battery. Furthermore, for example, in the case of a paste having a viscosity of 5,000 mPa·s or more when in contact with a gas, it is difficult to fluidize the paste and efficiently contact it with the gas. However, by feeding the paste with kinetic energy by centrifugal force such as in a spinning cone column, sufficient contact opportunities between the gas and the paste can be obtained, and dehydration from the paste becomes possible.

Brief Description of the Drawings

[0019]

Figure 1

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described in detail based on embodiments. The present invention according to a first aspect is a method for dehydrating a paste for manufacturing a lithium-ion secondary battery, wherein the paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a constituent component as a solid content, and contains an organic solvent having a boiling point higher than that of water or having an azeotropic point with water as a dispersion medium, and further has a viscosity at 100 °C of 30 mPa·s or more and less than 5,000 mPa·s, The paste 10 and the drying gas 20 for removing moisture from the paste are brought into contact in a countercurrent or co-current manner in multiple stages or with a sufficient distance, and the moisture contained in the paste volatilizes to the gas side and the gas containing moisture is discharged from the gas outlet. From the paste outlet, the paste dehydrated to moisture within the range of 1×10 -7 to 1×10 -4 is discharged. This is a method for dehydrating a paste for manufacturing a lithium-ion secondary battery, characterized by this.

[0021] Regarding the method for dehydrating a paste for manufacturing a lithium-ion secondary battery according to the present invention, first, the outline of the operation will be described based on the drawings. FIG. 1 is a schematic diagram showing an embodiment of the dehydration device of the present invention.

[0022] In one embodiment shown in FIG. 1, the paste 10 for manufacturing a lithium-ion secondary battery prepared from a predetermined raw material, as will be described later, is first temporarily held in a storage container 11 and is maintained at a predetermined temperature for dehydration treatment, for example, 20 to 100°C, by a temperature adjustment mechanism (not shown) equipped in the container.

[0023] The temperature adjustment mechanism is not particularly limited as long as it can maintain a predetermined temperature. For example, it may be a jacket provided outside the container 11, configured to be maintained by circulating warm water in the jacket, or various types such as an electric heater or a heat exchanger provided outside or inside the container can be adopted.

[0024] In the embodiment shown in FIG. 1, the temperature-adjusted paste 10 for manufacturing a lithium-ion secondary battery, which is the object to be processed, is fed from the container 11 into a dehydration device 30 connected through a paste supply pipe 13 via a liquid feed pump 12. In the dehydration device 30, the paste inlet 32 is provided on the upper side in the vertical direction of the dehydration device 30. Also, a flow meter 14 is provided in the middle of the supply pipe 13.

[0025] On the one hand, in the embodiment shown in FIG. 1, in the dehydration device 30, a gas supply pipe 21 for introducing the paste 10 for manufacturing the lithium-ion secondary battery and the dry gas 20 used for contacting and degassing in the device 30 into the dehydration device 30 is connected. In the dehydration device 30, the gas inlet 34 is provided on the lower side in the vertical direction of the dehydration device 30.

[0026] The configuration of the dehydration device 30 is not particularly limited as long as it can efficiently bring the paste 10 and the dry gas 20 for removing moisture from the paste into contact with each other in a countercurrent or cross-flow manner. In order to increase the surface area of the paste to enhance the contact efficiency, a spraying device such as a spray nozzle or an atomizer may be arranged, or a packing material may be arranged in the device to form a thin film of the paste. Furthermore, a configuration that utilizes the centrifugal force due to the rotational effect of a spinning cone, a rotating disk, a rotating drum, etc., gives kinetic energy to the paste while thinning the paste to promote stirring and improve the mass transfer rate may be used alone or in combination of a plurality of them.

[0027] More specifically, non-centrifugal motion energy-imparting type gas-liquid contact devices such as various packed towers using various fixed packing materials, and rotating devices such as centrifugal gas-liquid contact devices such as a spinning cone column, a rotating disk type contactor, a rotating drum type contactor, and a rotating packed tower using a rotating packing material can be mentioned. In addition, spraying devices such as the above-mentioned spray nozzles and atomizers can be used in arbitrary combination with these.

[0028] Note that when a centrifugal gas-liquid contact device such as a spinning cone column is used, for example, even when the temperature of the paste when contacting with the gas is relatively low and the viscosity is 5,000 mPa·s or more, sufficient contact efficiency with the gas can be obtained by feeding the paste with the kinetic energy due to the centrifugal force, and the desired dehydration can be achieved.

[0029] In the embodiment shown in FIG. 1, the dehydration device 30 is a packed tower having a height equivalent to three theoretical plates filled with regular packing.

[0030] During the dehydration process, it is desirable to reduce the pressure inside the system to a reduced pressure condition as necessary. Although not particularly limited, during the dehydration process, it is somewhat influenced by the type of organic dispersion medium used in the paste. For example, the pressure condition is set to 5 kPa to 105 kPa, more preferably about 5 kPa to 50 kPa.

[0031] In this state, the paste 10 for manufacturing a lithium-ion secondary battery maintained at a predetermined temperature in the range of 20°C to 100°C is supplied from the upper part of the apparatus 30 at a predetermined speed, and from the bottom of the tower, dry nitrogen gas, which is the dry gas 20, is supplied at a predetermined flow rate. Although it depends on the size of the dehydration apparatus 30, for example, it is supplied at 1 to 10 NL / min, and continuous operation is performed. As a result, the paste 10 is dehydrated in the dehydration apparatus 30, and the dried paste is continuously taken out from the paste outlet 33 of the dehydration apparatus 30. In the embodiment shown in FIG. 1, the paste outlet 33 is located at the lower part in the vertical direction (bottom of the tower) of the dehydration apparatus 30.

[0032] On the other hand, the gas containing moisture discharged from the gas outlet 31 at the upper part in the vertical direction (top of the tower) of the dehydration apparatus 30 is, if necessary, first passed through a small heat exchanger (not shown) for heat exchange with the cooled gas to be re-supplied and cooled, and then introduced into a condenser through which the cooled refrigerant, which is the gas dehydration unit 40, is passed, and dehydrated by reducing the dew point under atmospheric pressure to below the freezing point, for example, at least -10°C or lower, more preferably -15 to -50°C. For example, it is dried to a dew point of -15°C under atmospheric pressure, returned from the gas dehydration unit 40 to the gas introduction side of the gas supply pipe 21, the temperature is raised to about 5 to 20°C through the small heat exchanger as described above, and then introduced again into the dehydration apparatus 30 from the gas inlet 34 of the dehydration apparatus 30 by the gas circulation blower 24 for recycling. A gas flow meter 26 is provided in the gas supply pipe 21 immediately before the gas inlet 34 of the dehydration apparatus 30.

[0033] In this way, since the dry gas 20 is recycled in the continuous dehydration treatment operation, its consumption is substantially only the hold amount of the circulating gas path. Furthermore, the drying gas introduced through the circulation or path preferably has a dew point of at least -10°C or lower, more preferably -15 to -50°C, and even more preferably -60°C or lower.

[0034] The drying gas used is not particularly limited to the dried nitrogen gas used in this embodiment. For example, dried air or other dried inert gases such as argon, helium, and neon can also be used. Among these, dried nitrogen gas is preferably used. When a dried inert gas such as dried nitrogen gas is used as the drying gas, if the processed material, the paste 10, contains dissolved gases such as dissolved oxygen, it is also possible to remove such dissolved gases together during the dehydration treatment.

[0035] By setting the temperature of the paste during processing to 20 to 100°C, moisture can be efficiently removed by the drying gas that comes into efficient contact with the paste without adversely affecting the composition, physical properties, and properties of the paste, as well as the properties of the components in the paste. Although it is somewhat influenced by the type of organic dispersion medium used in the paste, the temperature of the paste is more preferably about 30 to 90°C, and even more preferably about 40 to 60°C.

[0036] Also, as the ventilation volume of the dried inert gas, by setting it to 30 to 300 L with respect to 1 kg of the dispersion having a moisture value of 1×10 -3 ~1×10 -2 moisture can be sufficiently removed without significantly affecting the composition of the dispersion. If the ventilation volume is less than necessary, it becomes difficult to effectively remove moisture. On the other hand, if it is more than necessary, the amount of the organic dispersion medium removed from the dispersion also increases, and there is a risk of unnecessarily varying the composition (non-volatile content) of the dispersion.

[0037] Note that the ventilation volume of the above-mentioned dried inert gas is the volume at normal temperature and pressure. In this specification, "normal temperature and pressure" refers to conditions in the range of, for example, 10 to 30°C and 96 kPa to 105 kPa, and typically specifically refers to conditions of a temperature of 23°C and 101.325 kPa (1 atmosphere).

[0038] Although not particularly limited, in one embodiment of the method for removing moisture of the present invention, as described above, the dispersion 10 and the dry gas 20 are brought into contact with each other to evaporate the moisture in the dispersion together with a small amount of the organic dispersion medium. The change in the non-volatile content of the dispersion before and after this treatment step is 0.5 mass% or less, more preferably 0.1 mass% or less, and the moisture content of the dispersion after the step is 5×10 -5 or less, more desirably 2×10 -5 or less, still more desirably 1×10 -5 or less, which is preferable.

[0039] In the method for removing moisture of the present invention, although it is preferable that the moisture content of the dispersion after the treatment is as small as possible, if the organic dispersion medium in the dispersion is removed by the inert gas more than necessary and the composition of the dispersion and the change in the non-volatile content of the dispersion change more than necessary, there is a risk of causing changes in the dispersion state, an increase in viscosity, aggregation of the dispersed substance, etc. in the dispersion. However, in the method for removing moisture of the present invention, even if the moisture content of the dispersion after the treatment is sufficiently dehydrated to be 5×10 -5 or less in mass fraction, typically, the change in the non-volatile content of the dispersion before and after the treatment step remains at 0.5 mass% or less, which is desirable. A method of preliminarily adding an excess of the organic dispersion medium and evaporating the excess organic dispersion medium added together with the moisture to remove the moisture is also considered. However, since it involves the use of excessive organic substances and an increase in the amount of waste gas emissions, it is not environmentally recommended.

[0040] The change in the non-volatile content of the dispersion before and after the treatment step can be calculated from the residue weight after drying at 140°C. In addition, the moisture content of the dispersion can be measured, for example, using a Karl Fischer moisture concentration meter, a near-infrared absorbance type trace moisture concentration meter, a refractive index type concentration meter, or the like. Alternatively, it can also be carried out with higher accuracy by gas chromatography using an ionic liquid column.

[0041] In one embodiment of the present invention, the moisture content of the exhaust gas after dehydration can be analyzed by an in-line gas analyzer to confirm the moisture content of the paste after dehydration. In a steady state, since the paste and gas discharged from the dehydration device are in an equilibrium relationship, the moisture content of the paste after dehydration can be calculated by measuring the moisture content of the exhaust gas. To continuously measure the moisture content of the paste, the influence of the solid content adhering to the detector can be considered. However, the measurement of the moisture content of the exhaust gas can be performed without problems using a general-purpose gas analyzer. Specifically, for example, the moisture content of the exhaust gas can be measured by using a dew point meter, a gas chromatograph equipped with a thermal conductivity detector (TCD), or the like.

[0042] In another embodiment of the present invention, the flow state of the paste and the flow rate of the drying gas are controlled by feedback control from the moisture content to dehydrate the paste to a target moisture content. By optimizing the rotation speed of the rotating equipment and the flow rate of the drying gas by feedback control from the moisture content, dehydration to the target moisture content can be achieved.

[0043] (Paste for manufacturing lithium-ion secondary batteries) Next, the paste for manufacturing lithium-ion secondary batteries to be processed in the present invention will be described in detail. The paste 10 for manufacturing lithium-ion secondary batteries to be processed is not particularly limited as long as at least one of an electrode active material, a conductive assistant, and a solid electrolyte is dispersed as a solid content in an organic dispersion medium.

[0044] (Electrode active material) In the paste for manufacturing lithium-ion secondary batteries to be processed in the present invention, the positive electrode active material that can be blended as a solid content is not particularly limited, but metal compounds such as metal oxides and metal sulfides capable of doping or intercalating lithium ions, and conductive polymers can be used.

[0045] For example, inorganic compounds such as oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium, transition metal sulfides, etc. can be mentioned. Specifically, transition metal oxide powders such as MnO, V2O5, V6O 13 , TiO2, etc., composite oxide powders of lithium and transition metals such as layered lithium nickelate, lithium cobaltate, lithium manganate, spinel-structured lithium manganate, lithium iron phosphate-based materials which are olivine-structured phosphate compounds, transition metal sulfide powders such as TiS2, FeS, etc. can be mentioned. Also, conductive polymers such as polyaniline, polyacetylene, polypyrrole, polythiophene, etc. can be used. Further, the above inorganic compounds and organic compounds may be mixed and used.

[0046] In the paste for manufacturing a lithium-ion secondary battery to be processed in the present invention, the negative electrode active material that can be blended as a solid content is not particularly limited as long as it can dope or intercalate lithium ions. For example, metal Li, alloy systems such as its alloys tin alloy, silicon alloy, lead alloy, etc., Li X Fe2O3, Li X Fe3O4, Li X WO2, metal oxide systems such as lithium titanate, lithium vanadate, lithium silicate, etc., conductive polymer systems such as polyacetylene, poly-p-phenylene, etc., amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbonaceous materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbonaceous materials, vapor-grown carbon fibers, carbon fibers, etc. can be mentioned. These negative electrode active materials can be used alone or in combination of two or more.

[0047] These electrode active materials preferably have an average particle diameter in the range of 0.05 to 100 μm, and more preferably in the range of 0.1 to 50 μm. The average particle diameter of the electrode active material referred to in this specification is the average value of the particle diameters measured by an electron microscope.

[0048] (Conductive aid) In the paste for manufacturing a lithium ion secondary battery to be processed in the present invention, as the conductive auxiliary agent that can be blended as a solid content, a carbon material, a metal material, or a mixture thereof can be used. The conductive auxiliary agent may contain, for example, at least one element selected from the group consisting of carbon, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osmium, rhodium, tungsten, and zinc. The conductive auxiliary agent is preferably a simple substance of carbon, carbon, nickel, copper, silver, cobalt, magnesium, lithium, ruthenium, gold, platinum, niobium, osmium, or rhodium having high conductivity, a simple substance of metal, a mixture, or a compound containing them. Examples of the carbon material include graphite, carbon black (CB), carbon nanotube (CNT), carbon nanofiber (CNF), carbon fiber (CF), fullerene, natural graphite, etc., and these can be used alone or in combination of two or more kinds. As the carbonaceous material, CB is particularly preferable. Further, examples of CB include furnace black, channel black, acetylene black, thermal black, etc., and any of them can be used. Among these, for example, acetylene black is preferable for blending in the paste for manufacturing a lithium ion secondary battery used for secondary battery applications because the metal component content is inherently low in its manufacturing method.

[0049] In addition, as CB, oxidized carbon black or graphitized carbon black that is usually performed can also be used. The oxidation treatment of CB is a treatment for directly introducing (covalently bonding) oxygen-containing polar functional groups such as phenolic groups, quinone groups, carboxyl groups, and carbonyl groups onto the surface of carbon black by subjecting carbon black to high-temperature treatment in air or secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., and improves the dispersibility of CB.

[0050] Herein, the "powder and granular" form of the carbon material is not particularly limited as long as it can form a uniform dispersion by being dispersed in a dispersion medium. For example, primary particles having an average particle diameter of about 10 to 60 nm, those in which such primary particles are aggregated or the like to exhibit secondary particles having an average particle diameter of about 1 to 1000 μm, or those that are further processed particles having an average particle diameter of about 0.5 to 5 mm by compression treatment or granulation treatment may be included. Furthermore, the shape is not particularly limited, and is not limited to a substantially spherical shape, and may include an elliptical shape, a flaky shape, a needle shape or a short fiber shape, an amorphous shape, etc. The average particle diameter of the carbonaceous material is more preferably about 0.5 mm or more to 5 mm or less. In addition, after being dispersed in a dispersion medium and prepared in a paste for manufacturing a lithium-ion secondary battery, it is desirable that the average particle diameter of the carbonaceous material in the dispersion medium is about 10 μm or less.

[0051] In addition, in this specification, the "average particle diameter" of the carbon material means the volume-based average particle diameter d50 (so-called median diameter) measured using a laser diffraction scattering particle size distribution measuring device.

[0052] Regarding carbon black, for example, as also described on the website of the Carbon Black Association (https: / / carbonblack.biz / index.html), the smallest unit that cannot be decomposed of carbon black is an aggregate (primary aggregate), and a part thereof (a domain) is generally referred to as a particle. This particle can be considered to correspond to a particle defined as the smallest unit in nanomaterials, but it is still only a part of the aggregate. Aggregates form agglomerates (secondary aggregates) by physical forces such as van der Waals forces. Furthermore, carbon black products are almost always transported and sold in the form of processed particles called beads by compression treatment or granulation treatment for preventing scattering and improving handleability.

[0053] For example, it may include primary aggregates having a particle size of about 10 to 100 nm, those in which such primary aggregates aggregate to form secondary aggregates having an average particle size of about 0.1 to 100 μm, or those that are processed particles having an average particle size of about 500 to 5000 μm by compression treatment or granulation treatment considering handleability, and the like.

[0054] From the viewpoint of the conductivity of carbon black, as the conductive carbon fine particles, those in which primary particles are connected to some extent to form a structure such as a chain or a bundle are preferable. The connection of the primary particles in the aggregate is also called a structure, and the degree of such development can be grasped by measuring the particle size distribution (dynamic light scattering method or laser diffraction / light scattering method) or observing with an electron microscope (either a scanning type or a transmission type can be used). Those having such a structure can efficiently form a conductive path between the electrode active material particles. Therefore, excellent conductivity can be imparted to the electrode active material layer with a smaller usage amount.

[0055] (Solid electrolyte) In the paste for manufacturing a lithium-ion secondary battery to be treated, as the solid electrolyte that can be blended as a solid content, the solid electrolyte is not particularly limited as long as it has lithium-ion conductivity. For example, sulfide-based solid electrolytes, hydride-based solid electrolytes, oxide-based solid electrolytes, etc. can be used. Among these, sulfide-based solid electrolytes with high lithium-ion conductivity are preferable.

[0056] The above-mentioned sulfide-based solid electrolyte is not particularly limited as long as it contains sulfur (S) and has ion conductivity. Examples of the sulfide solid electrolyte material include those obtained using a raw material composition containing Li2S and sulfides of elements in Groups 13 to 15.

[0057] Examples of the Group 13-15 elements include B, Al, Si, Ge, P, As, Sb, etc. Specific examples of the sulfides of the Group 13-15 elements include B2S3, Al2S3, SiS2, GeS2, P2S3, P2S5, As2S3, Sb2S3, etc. Among these, a sulfide solid electrolyte material using a raw material composition containing Li2S and a sulfide of a Group 13-15 element is preferably a Li2S-P2S5 material, a Li2S-SiS2 material, a Li2S-GeS2 material, or a Li2S-Al2S3 material from the viewpoint of excellent Li ion conductivity. Note that the Li2S-P2S5 material is a sulfide solid electrolyte material obtained using a raw material composition containing Li2S and P2S5, and it may contain Li2S and P2S5 as main raw materials, and may further contain other materials.

[0058] In addition to Li2S and the sulfides of the Group 13-15 elements, the above raw material composition may contain at least one lithium orthooxoacid selected from the group consisting of Li3PO4, Li4SiO4, Li4GeO4, Li3BO3, and Li3AlO3. By adding such a lithium orthooxoacid, a more stable sulfide solid electrolyte material can be obtained.

[0059] Furthermore, Li 10 GeP2S 12 (LGPS-based) and Li6PS5Cl (Ardydite-based) can also be used.

[0060] In addition, the sulfide solid electrolyte material may preferably contain LiI in that it can be a sulfide solid electrolyte material with high Li ion conductivity. Also, the sulfide solid electrolyte material may preferably contain Li2O in that it can be a sulfide solid electrolyte material with a small amount of hydrogen sulfide generation.

[0061] The sulfide solid electrolyte material in the present invention may be a sulfide glass, or may be a sulfide glass ceramic obtained by heat-treating the sulfide glass. The sulfide glass can be obtained, for example, by performing an amorphization method on the above raw material composition. Examples of the amorphization method include a mechanical milling method and a melt quenching method. Among them, the mechanical milling method is preferred because it enables processing at room temperature and simplifies the manufacturing process. Mechanical milling is not particularly limited as long as it is a method of mixing the raw material composition while imparting mechanical energy. Examples thereof include a ball mill, a turbo mill, mechanofusion, and a disk mill. Among them, a ball mill is preferred, and particularly, a planetary ball mill is preferred because a desired sulfide solid electrolyte material can be efficiently obtained. Also, the conditions of mechanical milling are preferably set so that a desired sulfide solid electrolyte material can be obtained. On the other hand, the sulfide glass ceramic can be obtained, for example, by heat-treating the sulfide glass at a temperature equal to or higher than the crystallization temperature. That is, by performing an amorphization method on the raw material composition and further performing a heat treatment, a sulfide glass ceramic can be obtained. Note that depending on the heat treatment conditions, there is a possibility that crosslinked sulfur and Li2S may be generated, or a stable phase may be generated. Therefore, in the present invention, it is preferable to adjust the heat treatment temperature and the heat treatment time so that these are not generated.

[0062] In addition, the sulfide solid electrolyte material preferably has high Li ion conductivity, and the Li ion conductivity at room temperature is, for example, 1×10 -4 S / cm or more, preferably 1×10 -3 S / cm or more.

[0063] Examples of the hydride-based solid electrolyte include a solid solution of LiBH4 and the following alkali metal compound (for example, a solid solution with a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1). Examples of the alkali metal compound in the solid solution include at least one selected from lithium halides (LiI, LiBr, LiF, LiCl), rubidium halides (RbI, RbBr, RbF, RbCl), cesium halides (CsI, CsBr, CsF, CsCl), lithium amide, rubidium amide, and cesium amide.

[0064] Examples of the oxide-based solid electrolyte include, for example, Li7La3Zr2O 12 , LiTi(PO4)3, LiGe(PO4)3, LiLaTiO3, and the like.

[0065] (organic dispersion medium) On the other hand, the organic dispersion medium used to disperse the solid content as described above is not particularly limited as long as it is an organic solvent having a boiling point higher than that of water or having an azeotropic point with water, and can be appropriately selected.

[0066] Although not particularly limited, examples of the organic solvent include ester solvents such as dibutyl ether, ethyl acetate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, hexyl propionate, heptyl propionate, octyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, pentyl butyrate, hexyl butyrate, heptyl butyrate, octyl butyrate, ethyl valerate, propyl valerate, butyl valerate, amyl valerate, hexyl valerate, heptyl valerate, octyl valerate, ethyl caproate, propyl caproate, butyl caproate, pentyl caproate, hexyl caproate, heptyl caproate, octyl caproate, ethyl heptanoate, propyl heptanoate, butyl heptanoate, pentyl heptanoate, hexyl heptanoate, heptyl heptanoate, octyl heptanoate; ketone solvents such as diethyl ketone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone (anone); aprotic polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP); alkane solvents such as pentane, cyclopentane, hexane, cyclohexane, heptane, cycloheptane, octane, cyclooctane, nonane, decane; chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate; toluene, xylene, benzene, mesitylene, paraffin, carbon tetrachloride, etc. These can be used alone or in combination of two or more.

[0067] Among these, particularly, NMP, butyl butyrate, pentyl butyrate, hexyl butyrate, xylene, mesitylene, heptane, etc. are preferable.

[0068] (Other formulations) In addition to the above-mentioned solid content and organic solvent, the paste for manufacturing a lithium-ion secondary battery, which is the object to be processed, may contain, for example, a dispersant, a pH adjuster, or other additives. As other additives, in addition to those such as a dispersion aid and a stabilizer, for example, those containing a binder resin may also be blended.

[0069] (Dispersant) The dispersant is not particularly limited. For example, polyvinyl butyral (PVB), polyvinyl acetal, polyvinyl alcohol, methyl cellulose, polyvinyl acetate, polyester resin, epoxy resin, polyether resin, alkyd resin, urethane resin, etc. can be exemplified.

[0070] As a preferable example among these, an example can be given of a form in which polyvinyl butyral is the main component, particularly 80% by mass or more, and further, 100% by mass of the total amount of the dispersant is polyvinyl butyral. When the paste for manufacturing a lithium-ion secondary battery is used for all-solid lithium-ion secondary battery applications, by using polyvinyl butyral as the dispersant in this way and combining it with the above-mentioned organic-based dispersion medium as the dispersion medium, good dispersibility of the carbonaceous material in the paste for manufacturing a lithium-ion secondary battery can be obtained, and the viscosity can be reduced.

[0071] Polyvinyl butyral is not particularly limited, but it preferably has a relatively low hydroxyl group content. Specifically, for example, the hydroxyl group content in the polymer is 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and still more preferably 12.5% by mass or more and 17.5% by mass or less. Also, although not particularly limited, the acetic acid group content of polyvinyl butyral is preferably about 1 to 7% by mass, and the viscosity is preferably such that the solution viscosity of a 10% by mass ethanol solution of polyvinyl butyral measured at 20 °C in accordance with DIN53015 is 10 to 100 mPa·s, particularly about 20 to 60 mPa·s.

[0072] (pH adjuster) Examples of the pH adjuster include amine compounds such as tertiary amines, secondary amines, primary amines, cyclic amines, and alkanolamines or amino alcohols which are compounds having an amino group and a hydroxy group in an alkane skeleton, or other amines such as diglycolamine, tris(hydroxymethyl)aminomethane (THAM), and morpholine. Although not particularly limited, among them, for example, 2-methylaminoethanol, 2-amino-1-butanol, 4-ethylamino-1-butanol, triethylamine, 2-amino-2-ethyl-1,3-propanediol (AEPD), 2-amino-2-methyl-1-propanol (AMP), THAM, etc. are preferable.

[0073] (Binder resin) In an embodiment where the paste for manufacturing a lithium-ion secondary battery, which is an object to be treated, is an electrode slurry for an all-solid-state lithium-ion secondary battery, the binder resin blended in the dispersion medium is not particularly limited, and a polymer insoluble in water can be used. Specifically, for example, polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamide, polyamideimide, butadiene rubber, isobutylene rubber, styrene-butadiene rubber, ethylene-propylene rubber, and nitrile-butadiene rubber can be used. Among these, polyvinylidene fluoride and styrene-butadiene rubber can be particularly preferably used.

[0074] (Mixing ratio in the paste for manufacturing a lithium-ion secondary battery) In the paste for manufacturing a lithium - ion secondary battery, which is the object to be processed, although not particularly limited, in an organic dispersion medium, the solid content composed of at least one of an electrode active material, a conductive assistant, and a solid electrolyte is adjusted to, for example, 10 to 25% by mass, more preferably 12 to 18% by mass, based on the total mass of the dispersion. When a dispersant is blended, although not particularly limited, the blending amount is adjusted to, for example, 5% by mass or more and less than 20% by mass, more preferably 6% by mass or more and less than 12% by mass, based on the mass of the solid content (that is, based on 100% by mass of the solid content). If the blending amounts of the solid content composed of at least one of the electrode active material, the conductive assistant, and the solid electrolyte and the dispersant are within these ranges respectively, it is possible to obtain a dispersion containing a high - concentration solid content while maintaining good dispersibility and low viscosity. Also, when the concentration of the solid content is less than the above, there are an increase in the energy required for solvent removal in product manufacturing, an increase in the transportation cost of the dispersion, and an increase in the cost of the solvent. On the other hand, when the concentration of the solid content is more than the above, it becomes difficult to obtain sufficient fluidity, and the handleability deteriorates.

[0075] Also, when a pH adjuster is blended as described above, although not particularly limited, the addition amount of the pH adjuster is 0.01 to 5%, more preferably about 0.05 to 3%, based on the total amount of the dispersion. By blending the pH adjuster within this range, it is possible to obtain better dispersibility of the paste for manufacturing a lithium - ion secondary battery.

[0076] (Characteristics of the paste for manufacturing a lithium - ion secondary battery as the object to be processed) And for the composition with the above - described composition and blending amounts, for example, the paste for manufacturing a lithium - ion secondary battery obtained by performing a dispersion treatment as exemplified below has a viscosity at 100 °C of 30 mPa·s or more and less than 5,000 mPa·s, preferably 40 mPa·s or more and less than 3,000 mPa·s, more preferably 50 mPa·s or more and less than 2,000 mPa·s. If the viscosity is too low compared to the above range, the contact time between the paste and the gas will be shortened, leading to an easy reduction in efficiency. On the other hand, if the viscosity is too high, flooding is likely to occur in the dehydration device due to poor fluidity.

[0077] In addition, in this specification, the viscosity of the paste for manufacturing a lithium-ion secondary battery at 100 °C is measured with a rheometer at a shear rate of 10 s -1 while pressurizing the measurement atmosphere with nitrogen to prevent volatilization.

[0078] Also, the water content in the paste for manufacturing a lithium-ion secondary battery as the object to be treated (i.e., before being treated by the dehydration method of the present invention) is not particularly limited. For example, it is about 1×10 -3 ~2×10 -2 or more preferably about 1×10 -3 ~1×10 -2 .

[0079] (Preparation of the paste for manufacturing a lithium-ion secondary battery as the object to be treated) The method for preparing the paste for manufacturing a lithium-ion secondary battery as the object to be treated is not particularly limited. However, it is prepared by adding a solid content composed of at least one of an electrode active material, a conductive assistant, and a solid electrolyte, as well as a dispersant, a pH adjuster, or other components that are added as necessary, to an organic dispersion medium in the above-described predetermined ratios, stirring and mixing them, and dispersing them. Note that the order of addition of the compounding components and the like are not particularly limited, and any mode is included in the scope of the present invention.

[0080] The dispersing device is not particularly limited, and a dispersing machine commonly used for pigment dispersion or the like can be used. For example, mixers such as a disper, a homomixer, a planetary mixer, homogenizers (such as "Clear Mix" manufactured by M Technique Co., Ltd., "Film Mix" manufactured by PRIMIX Co., Ltd., "Abramic Mix" manufactured by Silverson Co., Ltd., etc.), paint conditioners (manufactured by Red Devil Co., Ltd.), colloid mills (such as "PUC Colloid Mill" manufactured by PUC Co., Ltd., "Colloid Mill MK" manufactured by IKA Co., Ltd.), cone mills (such as "Cone Mill MKO" manufactured by IKA Co., Ltd.), ball mills, sand mills (such as "Dynomill" manufactured by Shinmaru Enterprises Co., Ltd.), attritors, pearl mills (such as "DCP Mill" manufactured by Eriez Co., Ltd.), media type dispersing machines such as coball mills, wet jet mills (such as "Genus PY" manufactured by Genus Co., Ltd., "Starburst" manufactured by Sugino Machine Co., Ltd., "Nanomizer" manufactured by Nanomizer Co., Ltd.), media-less dispersing machines such as "Clear SS-5" manufactured by M Technique Co., Ltd., "MICROS" manufactured by Nara Machinery Co., Ltd., and other roll mills, etc., but it is not limited thereto.

[0081] Preferably, it is finally prepared by dispersing the carbonaceous material using a media mill, particularly a media mill using beads with an average particle size of 0.05 to 2 mm. More preferably, it is prepared by performing a dispersion treatment using a shear type dispersing device as described in detail below prior to the dispersion treatment by such a media mill, and then performing a dispersion treatment by a media mill.

[0082] Also, prior to the dispersion treatment by such a media mill, it is possible to perform a preliminary dispersion treatment using other stirring devices, for example, shear type stirrers such as a disper and a homomixer.

[0083] Although not particularly limited, prior to the preparation of the paste for manufacturing a lithium-ion secondary battery, dehydration treatment can be performed on each component to be used by any known method such as dehydration using an adsorbent such as an ion exchange resin, zeolite, molecular sieve, alumina fine particles, phosgene-based compound, and metal oxide, dehydration by distillation or azeotropic dehydration, or dehydration by heating.

Example

[0084] Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0085] Preparation Example 1 [Preparation of Paste A for Manufacturing a Lithium-Ion Secondary Battery] First, Paste A for manufacturing a lithium-ion secondary battery, which is used as an object to be treated, was prepared as follows. That is, acetylene black was blended at a ratio of 15 parts by mass, butyl butyrate as a dispersion medium was blended at 84 parts by mass, and polyvinyl butyral as a dispersant was blended at 1 part by mass. The mixture was subjected to a dispersion treatment using a bead mill to prepare an acetylene black dispersion, which was used as Paste A for manufacturing a lithium-ion secondary battery. The water content of this Paste A for manufacturing a lithium-ion secondary battery was 1.3×10 mass fraction -3 It was, the non-volatile content was 16.00% by mass, and the viscosity at 25°C was 178 mPa·s. The viscosity at 100°C was 65 mPa·s, and the dissolved oxygen concentration was 22 mg / L. The water content (mass fraction) was measured using a Karl Fischer moisture concentration meter, and the non-volatile content was measured based on the residue weight after drying at 140°C. The viscosity at 25°C was measured using a B-type viscometer. After sufficiently stirring the dispersion with a spatula (for example, for 1 minute) at a rotor rotation speed of 60 rpm of the B-type viscometer, the value was immediately measured. Rotor No. 21 was used. The dissolved oxygen concentration in the paste was measured using a commercially available organic solvent-compatible DO meter. The viscosity at 100°C was measured using a rheometer at a shear rate of 10 s -1Measurement was carried out while pressurizing the measurement atmosphere with nitrogen to prevent volatilization. In addition, the measurement of each characteristic value in the following Examples, Comparative Examples, and Preparation Examples was carried out in the same manner as above, unless otherwise specified separately. Then, the paste A for manufacturing a lithium-ion secondary battery was dehydrated for the purpose of reducing it to less than 3.0×10 -5 in terms of mass fraction of water.

[0086] Comparative Example 1 10 kg of the above-prepared paste A for manufacturing a lithium-ion secondary battery was charged into a 15-L tank equipped with a stirrer, the pressure inside the system was reduced to 20 kPa, and it was stirred with a stirrer. The dispersion was heated to 50 °C with a heating jacket, and dry nitrogen was blown in from the bottom of the dispersion at a flow rate of 6 NL / min for 120 minutes (72 NL per kg of the paste) for dehydration treatment. The nitrogen discharged from the upper part of the tank was introduced into a condenser through which 10 °C cooling water passed to remove the solvent component, and then released to the atmosphere. The water content of the carbonaceous material dispersion after dehydration was 1.8×10 -5 in terms of mass fraction, and the non-volatile content was 16.32% by mass.

[0087] Example 1 The pressure inside the system of a packed tower with a tower diameter of 50 mm filled with regular packing and having a height equivalent to three theoretical plates was reduced to 20 kPa, and the paste A for manufacturing a lithium-ion secondary battery heated to 50 °C was supplied from the upper part of the tower at 0.1 kg / min, and nitrogen was supplied from the bottom of the tower at 3 NL / min, and continuous operation was carried out for 120 minutes. The nitrogen discharged from the top of the tower initially had a gas temperature of 48 °C. After first exchanging heat with the cooled gas to be re-supplied through a small heat exchanger, the temperature was lowered to 16 °C, introduced into a condenser through which a refrigerant at -20 °C passed to lower the dew point under atmospheric pressure to -15 °C, and then raised to 17 °C through a heat exchanger and introduced again from the bottom of the tower by a blower for recycling. Nitrogen with a dew point of -15 °C (water value 1630 ppm) was re-supplied and continuous operation was carried out. As a result, the water value of the treated paste discharged from the bottom of the tower was 2.5×10 -5It was 16.23% by mass of the non-volatile content. Also, the dissolved oxygen concentration of the paste after dehydration was 1 mg / L or less (below the detection limit). In the above treatment, the inert gas contacted per 1 kg of the paste was 30 NL, and the contact efficiency was better than that of Comparative Example 1. Also, although 12 kg of the paste was treated, since the nitrogen used for drying was recycled, the actual nitrogen consumption was only 4.5 L, which was the hold amount of the recycled portion.

[0088] Example 2 In Example 1, continuous operation was carried out in the same manner as in Example 1 except that the nitrogen supply amount from the bottom of the column was changed to 4.5 NL / min. The moisture value of the treated paste discharged from the bottom of the column was 6.0×10 mass fraction -6 It was 16.30% by mass of the non-volatile content.

[0089] Example 3 In Example 1, continuous operation was carried out in the same manner as in Example 1 except that the nitrogen supply amount from the bottom of the column was changed to 6 NL / min. The moisture value of the treated paste discharged from the bottom of the column was 8.0×10 mass fraction -7 It was 16.42% by mass of the non-volatile content.

[0090] Preparation Example 2 [Preparation of Paste B for Lithium Ion Secondary Battery Manufacturing] Paste B for lithium ion secondary battery manufacturing was prepared as follows. That is, it was blended at a ratio of 20 parts by mass of acetylene black, 79 parts by mass of NMP as a dispersion medium, and 1 part by mass of polyvinyl alcohol as a dispersant, and dispersion treatment was performed with a bead mill to prepare an acetylene black dispersion, which was used as Paste B for lithium ion secondary battery manufacturing. The moisture content of this Paste B for lithium ion secondary battery manufacturing was 1.5×10 mass fraction -3 It was 21.00% by mass of the non-volatile content, and the viscosity at 25°C was 221 mPa·s. The viscosity at 100°C was 87 mPa·s.

[0091] Example 4 The system pressure inside a packed tower with a tower diameter of 50 mm filled with a regular packing material and having a height equivalent to three theoretical stages was reduced to 6.7 kPa, and paste B for manufacturing a lithium-ion secondary battery heated to 100 °C was supplied from the upper part of the tower at 0.1 kg / min. Nitrogen was supplied from the bottom of the tower at 4 NL / min, and continuous operation was carried out for 120 minutes. The nitrogen discharged from the top of the tower initially had a gas temperature of 48 °C. After first performing heat exchange with a cooled gas that was re-supplied through a small heat exchanger, the temperature was lowered to 16 °C, introduced into a condenser through which a refrigerant at -20 °C was passed to lower the dew point under atmospheric pressure to -15 °C, then raised to 17 °C through a heat exchanger, and re-introduced from the bottom of the tower by a blower for recycling. When nitrogen with a dew point of -15 °C was re-supplied and continuous operation was carried out, the moisture content of the treated paste discharged from the bottom of the tower was 2.8×10 -5 in mass fraction, and the non-volatile content was 21.15 mass%.

[0092] Preparation Example 3 [Preparation of Paste C for Manufacturing Lithium-Ion Secondary Battery] Paste C for manufacturing a lithium-ion secondary battery was prepared as follows. That is, with respect to 10.0 g of paste A for manufacturing a lithium-ion secondary battery prepared as described above, 30.0 g of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 powder (manufactured by Fujifilm Wako Pure Chemical Corporation, particle size 1 to several μm), a binder solution in which styrene-butadiene rubber was dissolved in 10 mass% butyl butyrate, and butyl butyrate were blended so that the total solid content concentration became 65 mass%, and using a revolution and rotation stirring and defoaming machine, revolution and rotation were carried out at a rotation speed of 1200 rpm for both, and the treatment was carried out for 5 minutes. The moisture content of the obtained paste C for manufacturing a lithium-ion secondary battery was 1.5×10 -3 in mass fraction, the non-volatile content was 65.00 mass%, and the viscosity at 25 °C was 3,476 mPa·s. The viscosity at 100 °C was 1,842 mPa·s. The measurement methods for the moisture content, non-volatile content, and viscosity at 100 °C are the same as those described above. The measurement method for the viscosity at 25 °C is the same as that described above except that the rotor of the B-type viscometer was changed to No. 22. Then, dehydration was carried out with the aim of reducing the moisture content of this paste C for manufacturing a lithium-ion secondary battery to less than 3.0×10 -5 by mass fraction.

[0093] Example 5 The internal pressure of a packed tower with a tower diameter of 50 mm filled with regular packing and having a height equivalent to three theoretical plates was reduced to 20 kPa, and the paste C for manufacturing a lithium-ion secondary battery heated to 50 °C was supplied from the upper part of the tower at 0.05 kg / min, and nitrogen was supplied from the bottom of the tower at 1.5 NL / min, and continuous operation was carried out for 120 minutes. The nitrogen discharged from the top of the tower initially had a gas temperature of 48 °C. After first passing through a small heat exchanger for heat exchange with the cooled gas to be re-supplied, the temperature was lowered to 16 °C, then introduced into a condenser through which a refrigerant at -20 °C was passed to lower the dew point under atmospheric pressure to -15 °C, and then raised to 17 °C through a heat exchanger and re-introduced from the bottom of the tower by a blower for recycling. When nitrogen with a dew point of -15 °C was re-supplied and the operation was continuously carried out, the moisture value of the treated paste discharged from the bottom of the tower was 2.3×10 -5 by mass fraction, and the non-volatile content was 65.13% by mass.

[0094] Example 6 In a spinning cone column distillation tower with a tower diameter of 150 mm equipped with a spinning cone column instead of regular packing, the pressure was reduced to 20 kPa as an operating condition, dry nitrogen was supplied from the bottom of the tower, and the paste C for manufacturing a lithium-ion secondary battery heated to 40 °C was supplied from the top of the tower. When one fixed cone and one rotating cone of the spinning cone column were regarded as one stage, the angle of the cone was 60° with respect to the horizontal direction at five stages, the rotation speed of the rotating cone was 300 rpm, the supply amount of nitrogen was 5 L / min, and the supply amount of the paste was 0.2 kg / min. When the operation was carried out, the moisture value of the paste discharged from the bottom of the tower was 1.6×10 -5 by mass fraction, and the non-volatile content was 65.17% by mass. Since a paste with a high viscosity could be forcibly fed, it became possible to process more efficiently by bringing the paste into contact with the gas by natural fall of the paste.

Industrial Applicability

[0095] According to the present invention, in the manufacturing process of a lithium-ion secondary battery, it becomes possible to efficiently remove moisture in an electrode mixture paste or the like. Further, according to the present invention, in the manufacturing process of an all-solid-state lithium-ion secondary battery using a sulfide-based solid electrolyte, it becomes possible to efficiently remove moisture in the solid electrolyte material.

Explanation of Signs

[0096] 10 Paste for manufacturing a lithium-ion secondary battery 12 Liquid feed pump 14 Flow meter 20 Drying gas 22 Vacuum pump 24 Gas circulation blower 26 Gas flow meter 30 Dehydration device 31 Gas outlet 32 Paste inlet 33 Paste outlet 34 Gas inlet 40 Gas dehydration section 50 Dehydrated paste

Claims

1. A method for dehydrating a paste for manufacturing a lithium ion secondary battery, comprising the steps of: The paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a solid component, and The dispersion medium contains an organic solvent that has a boiling point higher than that of water or has an azeotropic point with water, Furthermore, the viscosity at 100°C is 30 mPa·s or more and less than 5,000 mPa·s, The paste is contacted with a dry gas for removing moisture from the paste in a counterflow or crossflow manner, and the moisture contained in the paste is volatilized into the gas side from the gas outlet, and a gas containing moisture is discharged from the paste outlet. －７ From 1 x 10 －４ and discharging the paste dehydrated to a moisture content within the range of 100%.

2. 2. The method according to claim 1, wherein the organic solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone, butyl butyrate, pentyl butyrate, hexyl butyrate, xylene, mesitylene and heptane.

3. 2. The method according to claim 1, wherein the non-volatile content of the dehydrated paste varies by 0.5% by mass or less.

4. 2. The method for dehydrating the paste according to claim 1, wherein the temperature of the paste to be fed is in the range of 20 to 100° C. and the pressure in the system during the dehydrating operation is in the range of 5 to 105 kPa.

5. The dehydration method according to claim 1, wherein the moisture content of the discharged gas is reduced to a dew point of less than −10° C. under atmospheric pressure by at least one of cooling, compression by a compressor, and adsorption, and a part or all of the gas is recycled and reused.

6. 2. The method for dehydrating a paste according to claim 1, wherein at least one of the paste and the dry gas is caused to flow by kinetic energy when the paste and the dry gas are brought into contact with each other.

7. 2. The method of claim 1, further comprising the step of: analyzing the moisture content of exhaust gas after dehydration with an in-line gas analyzer to confirm the moisture content of the paste after dehydration.

8. 8. A method for dehydrating the paste according to claim 7, further comprising controlling the flow state of the paste and the flow rate of the drying gas through feedback control based on the moisture value, thereby dehydrating the paste to a target moisture value.

9. 2. The method according to claim 1, wherein nitrogen is used as the drying gas.

10. A dehydration device for a paste for manufacturing a lithium ion secondary battery having a viscosity at 100°C of 30 mPa·s or more and less than 5,000 mPa·s, The paste contains at least one of an electrode active material, a conductive assistant, and a solid electrolyte as a solid component, and The dispersion medium contains an organic solvent that has a boiling point higher than that of water or has an azeotropic point with water, A dehydration device for paste for manufacturing lithium ion secondary batteries, characterized in that it has a structure in which the paste is contacted with a dry gas for removing moisture from the paste in multiple stages in a countercurrent or crosscurrent manner.

11. The dehydration apparatus according to claim 10, further comprising a centrifugal gas-liquid contactor as a structure for contacting the paste with the dry gas in a countercurrent or crossflow manner in multiple stages.

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