JP2019071229A - Electrode slurry, and production method of electrode slurry and manufacturing method of electrode for electric device - Google Patents

Abstract

To reduce molding loss by restraining occurrence of crack in a mixture layer.SOLUTION: Electrode slurry includes active material particles, a conductive aid, a solvent, and a binder precursor, and the number of surrender at the 15-200 Pa of the shear stress-distortion curve measured by a rheometer is one. A production method of electrode slurry includes a blending step of obtaining a mixed solution by blending the active material particles, the conductive aid, the solvent, and the binder precursor, and an agitation step of agitating the mixed solution until the number of surrender at the 15-200 Pa of the shear stress-distortion curve measured by the rheometer becomes one.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrode slurry, a method of producing an electrode slurry, and a method of producing an electrode for an electric device. In particular, the present invention relates to an electrode slurry capable of suppressing the occurrence of cracks in the mixture layer and reducing molding loss, a method of producing the electrode slurry, and a method of producing an electrode for an electric device using the same. .

  BACKGROUND In recent years, electric devices such as lithium ion secondary batteries have been widely used in electronic devices such as mobile phones and notebook computers, vehicles such as electric vehicles (EVs) and hybrid electric vehicles.

  An electrode for an electric device such as a lithium ion secondary battery is prepared, for example, by applying an electrode slurry, which is a mixture of an active material, a conductive additive, a binder, and a solvent, to a current collector and then heat treating it. A layer can be formed on the current collector.

  However, particles such as the active material and the conductive additive have a property of being easily aggregated in the electrode slurry. Therefore, if the mixture layer is formed in a state in which these aggregates remain, unevenness due to the aggregates may be generated on the electrode surface, and the separator may be broken at the time of battery manufacture to contact with the other electrode and cause a short circuit. Therefore, Patent Document 1 proposes that the yield value of the slurry be in the range of 1 Pa to 250 Pa to suppress the occurrence of a short circuit between the electrodes.

Unexamined-Japanese-Patent No. 2003-331829

  However, even when the yield value of the slurry was in the range of 1 Pa to 250 Pa as in Patent Document 1, it was found that cracks may occur in the mixture layer after the slurry is applied and heat treated. . When a crack occurs in the mixture layer, the crack may pierce the separator at the time of manufacturing the battery and may be in contact with the other electrode to cause a short circuit.

  In addition, even if the electrode is manufactured under a predetermined condition or a raw material that does not generate a crack, the crack may occur if the lot of the raw material is different. Such a crack can not be confirmed unless the electrode slurry is heat-treated once to form a mixture layer, and if the occurrence of the crack is found during production, a large amount of forming loss may occur. In addition, even when the electrode slurry sampled in advance is heat-treated to form a mixture layer, it takes a lot of time, which is not efficient.

  The present invention has been made in view of the problems that such prior art has. And the object of the present invention is to provide an electrode slurry capable of suppressing the generation of cracks in the mixture layer and reducing the forming loss, and a method of producing the electrode slurry and a method of producing the electrode for an electric device. is there.

  An aspect of the present invention is that the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one.

  According to the present invention, generation of cracks in the mixture layer can be suppressed, and molding loss can be reduced.

It is a shear stress-strain curve when the material of a reference example is measured with a rheometer. It is sectional drawing which shows an example of the electrode for electric devices which concerns on this embodiment, and an electric device. It is a shear stress-strain curve when the electrode slurry of an Example and a comparative example is measured by a rheometer. 5 is an appearance photograph of a mixture layer of Example 1. FIG. It is an external appearance photograph of the mixture layer of Comparative Example 2.

  Hereinafter, an electrode slurry according to the present embodiment, a method of manufacturing the electrode slurry, and a method of manufacturing an electrode for an electric device will be described in detail using the drawings. The dimensional ratios in the drawings are exaggerated for the convenience of description, and may differ from the actual ratios.

[Electrode slurry]
According to the prior art, by setting the yield value of the electrode slurry to be in the range of 1 Pa to 250 Pa, unevenness of the surface of the mixture layer due to the aggregates is reduced, and the separator is broken and a short circuit occurs between the electrodes. It is believed that it can be suppressed.

  However, even if the yield value of the slurry is in the range of 1 Pa to 250 Pa, cracks may occur in the mixture layer after the slurry is applied and heat treated. When a crack occurs in the mixture layer, the crack may pierce the separator at the time of manufacturing the battery and may be in contact with the other electrode to cause a short circuit.

  For example, in a solution in which a polyamic acid is dispersed in N-methyl-2-pyrrolidone (NMP) without active material particles and a conductive aid, there are no particles that form large aggregates. Therefore, in such a solution, as shown in Reference Example 1 of FIG. 1, the graph on the shear stress-strain curve obtained by the measurement with the rheometer draws a linear straight line having a positive slope.

  In addition, as shown in reference example 2 in FIG. 1, when polyamic acid and active material particles are dispersed in NMP without a conductive auxiliary agent, a portion surrounded by a circle in a graph of shear stress-strain curve The yield of the electrode slurry as shown in FIG. Since this yield is the minimum stress necessary to cause the fluid to flow, it represents a yield value defined by Japanese Industrial Standard JIS K5701-1: 2000 (Planar Ink-Part 1: Test Method) it is conceivable that. The mixture layer formed by the electrode slurry does not crack.

  On the other hand, as shown in Reference Example 3 of FIG. 1, when carbon particles are further added to the electrode slurry of Reference Example 2 in which polyamic acid and active material particles are dispersed in NMP, depending on the dispersion state of the electrode slurry, As circled in, there are cases where two surrenders can be confirmed. The two yields of Reference Example 3 are respectively 22 Pa and 47 Pa, and according to the definition of JIS K5701, 22 Pa is considered to be the yield value.

  However, although the yield value of the electrode slurry of Reference Example 3 is within the range of 1 Pa to 250 Pa as suggested by the prior art in any yield, when the mixture layer is formed of such an electrode slurry, the mixture layer is formed A crack has occurred.

  In the electrode slurry containing a plurality of particles as in Reference Example 3, there may be a case where a complex three-dimensional network structure is formed, and in addition to the yield value in the above-mentioned JIS K5701, shear stress is applied. It is thought that there is a point where the strain increases rapidly. In such an electrode slurry, the dispersion of the particles is not sufficient, and it is considered that the particles form complex aggregates.

  When an aggregate is formed in the electrode slurry, a sufficient amount of the binder precursor does not easily reach inside the aggregate due to steric hindrance, and sufficient strength is difficult to obtain, and a crack is generated when the mixture layer is formed. It is easy to become a starting point. In particular, in the case of using a binder having a large strength so as to be compatible with expansion and contraction of the active material particles during charge and discharge, or in the case of increasing the film thickness of the mixture layer, the mixture layer when the electrode slurry is heat-treated. Cracks tend to occur because the shrinkage stress of the

  Therefore, the electrode slurry of the present embodiment includes active material particles, a conductive support agent, a solvent, and a binder precursor, and the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is 1 It is one. Thus, in the electrode slurry of the present embodiment, the number of breakdowns is not two or more, but only one. Therefore, when the mixture layer of the electrode is formed using the electrode slurry of the present embodiment, the aggregates of the active material particles and the conductive additive are dispersed. Therefore, when the mixture layer is formed, it is possible to suppress the occurrence of cracks in the mixture layer due to the shrinkage of the binder. Hereinafter, the configuration of the present embodiment will be described in detail.

  The electrode slurry of the present embodiment includes active material particles, a conductive additive, a solvent, and a binder precursor.

  Active material particles participate in a chemical reaction that generates an electric current in an electrical device. The active material particles may be positive electrode active material particles or negative electrode active material particles.

As a material which forms a positive electrode active material particle, lithium-transition metal complex oxide, a lithium-transition metal phosphoric acid compound, a lithium-transition metal sulfuric acid compound etc. are mentioned, for example. Examples of the lithium-transition metal composite oxide include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni-Mn-Co) O ₂ , Li (Li-Ni-Mn-Co) O ₂ and their transition A metal in which a part of the metal is substituted by another element can be mentioned. Examples of lithium-transition metal phosphate compounds include LiFePO _{4 and the} like. Lithium - transition metal sulfate _compound, mention may be made of _{Li x Fe 2 (SO 4)} 3 and the like.

As a material for forming the negative electrode active material particles, for example, graphite (natural graphite, artificial graphite, etc.) which is high crystalline carbon, low crystalline carbon (soft carbon, hard carbon), carbon black (ketjen black, acetylene black, etc.) And channel black, lamp black, oil furnace black, thermal black, etc.), fullerenes, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon fibrils, and other carbon materials. In addition, the said carbon material contains what contains a silicon nanoparticle of 10 mass% or less. Moreover, as a material for forming the negative electrode active material particles, silicon (Si), germanium (Ge), tin (Sn), lead (Pb), aluminum (Al), indium (In), zinc (Zn), hydrogen ( H), calcium (Ca), strontium (Sr), barium (Ba), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), silver (Ag), gold ( Au), cadmium (Cd), mercury (Hg), gallium (Ga), thallium (Tl), carbon (C), nitrogen (N), antimony (Sb), bismuth (Bi), oxygen (O), sulfur ( S), elemental elements alloying with lithium such as selenium (Se), tellurium (Te), chlorine (Cl), etc., and oxides containing these elements (silicon monoxide (SiO), SiO _x (0 <x <2 , Tin _{(SnO 2)} dioxide, SnO x (0 <x < 2), etc. SnSiO ₃₎ and the like carbides (silicon carbide (SiC)), and the like. Furthermore, as a material for forming the negative electrode active material particles, mention may be made of metal materials such as lithium metal and lithium-transition metal complex oxides such as lithium-titanium complex oxide (lithium titanate: Li ₄ Ti ₅ O ₁₂ ). Can. These negative electrode active material particles may be used alone or in combination of two or more.

  The negative electrode active material particles are preferably silicon-based particles. Silicon-based particles have a large lithium ion storage amount per atom and a large discharge capacity as compared with particles using a carbon material or the like. The silicon-based particles can be, for example, an alloy containing 20% by mass or more of silicon.

  The content of the active material particles is preferably 40% by mass to 90% by mass, more preferably 50% by mass to 80% by mass, and more preferably 55% by mass to 75% by mass with respect to the entire solid content of the electrode slurry excluding the solvent. Is more preferred.

  The average particle size of the active material particles is not particularly limited, but is preferably 0.01 μm to 20 μm, and more preferably 0.4 μm to 10 μm. By setting the average particle size of the active material particles in such a range, the cycle durability of the electric device can be improved. The average particle size of the active material particles can be the particle size when the cumulative value of the particle size distribution on a volume basis measured by the laser diffraction / scattering method is 50%.

  The conductive aid can effectively form an electronic network inside the mixture layer. The conductive aid is preferably carbon particles. This is because carbon particles have good electrical conductivity. As a material which forms carbon particles, carbon materials, such as carbon black, such as acetylene black, a graphite, and carbon fiber, are mentioned, for example. These carbon particles may be used alone or in combination of two or more.

  The shape of the conductive aid is not particularly limited, and for example, a conductive aid having a spherical, flake, fibrous, short chain, long chain, or needle shape may be used.

  The particle diameter of the conductive aid is not particularly limited, but in the case of a fibrous conductive aid, for example, the fiber diameter is preferably 5 nm to 50 nm and the fiber length is preferably 50 nm to 50 μm. Further, for example, in the case of a spherical conductive auxiliary, the average primary particle diameter is preferably 45 nm or less. In addition, the particle diameter of a conductive support agent can be made into the average value of several-dozens of fiber length measured using the transmission electron microscope (TEM) or the scanning electron microscope (SEM) etc.

  1 mass%-10 mass% are preferable with respect to the whole solid content of the electrode slurry except a solvent, and, as for content of a conductive support agent, 2 mass%-8 mass% are more preferable. By making content of a conductive support agent into such a range, aggregation of a conductive support agent can be suppressed, maintaining the conductivity of a mixture layer.

  The solvent is preferably an organic solvent. The organic solvent is because the solubility of the binder precursor is high and the volatility is also excellent. Examples of the organic solvent include aromatic solvents such as N-methyl-2-pyrrolidone (NMP), toluene and xylene, amide solvents such as dimethylformamide and dimethylacetamide, ketone solvents such as methyl ethyl ketone and cyclohexanone, acetate ester And ester solvents such as H, and hydrocarbon solvents such as hexane and cyclohexane. These solvents may be used alone or in combination of two or more. Among these, the organic solvent is more preferably N-methyl-2-pyrrolidone because of high solubility and easy handling.

  Although content of the solvent in an electrode slurry is not specifically limited, 10 mass%-60 mass% are preferable, 20 mass%-50 mass% are more preferable, and 25 mass%-45 mass% are more preferable. By setting the content of the solvent in such a range, the coatability can be improved, and since the liquid drips hardly occur, the electrode slurry can be thickly coated.

  The binder precursor is a material that forms a binder of the mixture layer by heat treatment or the like. The binder can bind the active material particles to each other or bind the active material particles and the conductive aid.

  The binder precursor is preferably a polymer precursor. As a polymer precursor, a thermoplastic resin precursor, a thermosetting resin precursor, an elastomer precursor etc. are mentioned, for example. By using such a polymer precursor as a binder precursor, the binder function required as a mixture layer of an electrode can be exhibited effectively.

  As a thermoplastic resin precursor, for example, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyether nitrile (PEN), polyacrylonitrile (PAN) ), Polyimide (PI), polyamide (PA), polyamideimide (PAI), carboxymethylcellulose (CMC), ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), poly Precursors such as tetrafluoroethylene (PTFE) and polyvinyl fluoride (PVF) can be mentioned. Moreover, as a thermosetting resin precursor, the precursor of an epoxy resin etc. are mentioned, for example. Moreover, as an elastomer precursor, precursors, such as styrene butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), are mentioned, for example. These binder precursors may be used alone or in combination of two or more.

  Among these, the binder precursor is more preferably a polyimide precursor. That is, the binder precursor is more preferably a polyamic acid. Polyamic acid is a precursor of polyimide. Polyimide is preferable because it contributes to the improvement of the cycle durability of the electrode because it has high physical strength and high heat resistance. In addition, since the contraction force of the electrode slurry after heat treatment is larger than that of other binders, polyamic acid tends to easily generate a crack in the mixture layer after heat treatment. However, according to the method for manufacturing an electrode for an electric device of the present embodiment, since the number of aggregates is reduced to one, particle aggregates are reduced, and thus the mixture layer is unlikely to be cracked even if heat treatment is performed.

  The content of the binder contained in the mixture layer is not particularly limited, but is preferably 0.5% by mass to 20% by mass, and more preferably 1% by mass to 15% by mass with respect to the total solid content of the electrode slurry. .

  In the electrode slurry of the present embodiment, the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one. In the present embodiment, by setting the number of yield to one in this manner, the aggregates of the active material particles and the conductive additive are dispersed. Therefore, when the mixture layer is formed, it is possible to suppress the occurrence of cracks due to shrinkage of the mixture layer.

  The shear stress-strain curve can be measured by a rheometer. As a rheometer, an apparatus like a cone and plate viscometer can be used, for example. The shear stress-strain curve is measured by disposing the electrode slurry between the upper plate and the lower plate of the rheometer and rotating at least one of the upper plate and the lower plate while controlling with shear stress. Can. Then, a shear stress-strain curve can be created by measuring the amount of strain of the electrode slurry relative to the shear stress.

  The measurement conditions of the rheometer can be measured, for example, at room temperature (25 ° C.). Also, the electrode slurry disposed between the upper plate and the lower plate may be, for example, 0.08 mL, depending on the volume between the plates. Further, for example, a cone spindle with a diameter of 25 mm can be used as the upper plate, and a flat plate with a diameter of 25 mm can be used as the lower plate. In addition, the shortest distance between the plates (for example, the distance between the tip of the cone spindle and the flat plate) can be, for example, 50 μm. The method of controlling the shear stress can be controlled, for example, by continuously raising the shear stress from 10 Pa to 250 Pa at a scanning speed of 1 Pa / sec.

  Since the yield is a position where the strain changes rapidly when the shear stress is continuously increased, specify the number of yield at 15 Pa to 200 Pa by visually confirming the shear stress-strain curve. Can. When the location of the yield is specified more precisely, for example, in the shear stress-strain curve, it may be the intersection of the tangents of the baselines disposed so as to sandwich the position of the yield. In addition, when the angle formed of these two tangents is 145 degrees or less, it can be considered as a yield. Further, the position of yield may be a position at which the maximum value is obtained in the graph obtained by differentiating the slope of the tangent of the shear stress-strain curve. That is, the position of yield may be a portion where the maximum value is obtained in the graph obtained by second-order differentiation of the shear stress-strain curve. The term "yield" refers to a portion of the shear stress-strain curve that clearly forms a convex portion with respect to the baseline, and does not include a minute peak that is determined as noise.

  As described above, the electrode slurry of the present embodiment includes active material particles, a conductive support agent, a solvent, and a binder precursor, and the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer There is one. Thus, in the electrode slurry of the present embodiment, the number of breakdowns is one, not two or more. Therefore, in the electrode slurry of the present embodiment, aggregates of active material particles and a conductive additive are dispersed. Therefore, when the mixture layer is formed, it is possible to suppress the occurrence of cracks in the mixture layer due to the shrinkage of the binder.

[Electrode for Electric Device]
The electrode for an electric device of the present embodiment will be described. In addition, description is abbreviate | omitted about the part which overlaps with embodiment mentioned above. The electrode for an electric device of the present embodiment includes a substrate and a mixture layer. As shown in FIG. 2, the electrode for an electric device may be either the positive electrode 10 or the negative electrode 20, but generally, in the case of the negative electrode 20, cracks are easily generated at the time of formation of the negative electrode mixture layer. The effect of suppressing cracks is great.

  The substrate can be, for example, a current collector. The current collector transfers electrons between the mixture layer and an external device or the like outside the electrical device. The current collector may be the positive electrode current collector 11 or the negative electrode current collector 21. The material forming the base is, for example, metal such as aluminum (Al), copper (Cu), titanium (Ti), nickel (Ni), stainless steel (SUS), aluminum alloy, copper alloy, titanium alloy, nickel alloy and the like Can be mentioned. Among these, aluminum (Al) is preferably used as a material for forming the positive electrode current collector 11, and copper (Cu) is preferably used as a material for forming the negative electrode current collector 21.

  The thickness of the substrate is preferably 1 μm to 100 μm. By setting the thickness of the substrate in this range, the electrical resistance can be reduced and the mechanical properties can be maintained. The thickness of the substrate is more preferably 5 μm or more and 40 μm or less, and further preferably 10 μm or more and 25 μm or less.

  The mixture layer is formed by applying the above-mentioned electrode slurry to a substrate and heat treating it. Specifically, the solvent in the electrode slurry is volatilized by the heat treatment, and the binder precursor reacts to become a binder, thereby forming a mixture layer. That is, the mixture layer includes active material particles, a conductive additive, and a binder. The mixture layer may be the positive electrode mixture layer 12 or the negative electrode mixture layer 22.

  The thickness of the mixture layer after heat treatment is preferably 40 μm to 150 μm, and more preferably 60 μm to 100 μm. By setting the film thickness of the mixture layer in such a range, the mass of the active material per unit area can be increased, and the energy density per unit mass of the electric device can be improved. When the thickness of the electrode slurry to be coated is large, the contraction force of the electrode slurry at the time of heat treatment is large, and thus the mixture layer tends to be easily cracked. However, in the present embodiment, generation of cracks in the mixture layer after heat treatment can be suppressed by stirring the electrode slurry until the number of yield is one.

[Electric device]
The electric device of the present embodiment will be described. In addition, description is abbreviate | omitted about the part which overlaps with embodiment mentioned above. The electric device of the present embodiment includes the electrode for the electric device. According to the electrode for an electric device described above, it is possible to suppress a crack generated in the mixture layer. Therefore, according to the electrical device provided with the electrode for an electrical device, the risk of the crack of the mixture layer breaking through the separator and coming into contact with the other electrode to cause a short circuit can be reduced. Therefore, according to the electrical device of the present embodiment, a highly reliable electrical device can be provided.

  As an electric device, a lithium ion secondary battery, an electric double layer capacitor, etc. are mentioned, for example. Hereinafter, each structure is demonstrated taking the lithium ion secondary battery 100 shown by FIG. 2 as an example.

  As shown in FIG. 2, the lithium ion secondary battery 100 can include the positive electrode 10, the negative electrode 20, and the separator 30 disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10 and the negative electrode 20 correspond to the electrode for an electric device according to the above-described embodiment. In addition, as shown in FIG. 2, what laminated | stacked multiple electric cell layers 40 provided with the positive electrode 10, the negative electrode 20, and the separator 30, and was electrically arrange | positioned in parallel can also be used as the electric power generation element 50. Further, the lithium ion secondary battery 100 may further include a positive electrode tab 60, a negative electrode tab 65, an exterior body 70, and the like.

  Further, the lithium ion secondary battery 100 according to the present embodiment is not limited to the form as shown in FIG. 2 and, for example, the positive electrode mixture layer is disposed on one surface of the current collector and the other It may be a bipolar battery including a bipolar electrode in which a negative electrode mixture layer is disposed on the surface. Moreover, it is not limited to a lamination | stacking type lithium ion secondary battery like embodiment of FIG. 2, It is good also as a winding type lithium ion secondary battery.

(Separator 30)
The separator 30 can be disposed between the positive electrode 10 and the negative electrode 20. The separator 30 separates the positive electrode 10 and the negative electrode 20 and mediates the movement of lithium ions. The film thickness of the separator 30 is preferably 1 μm to 100 μm, and more preferably 5 μm to 50 μm from the viewpoint of reducing the internal resistance. The separator 30 can include a non-aqueous electrolyte. As the non-aqueous electrolyte, a gel-like or solid polymer electrolyte in which a lithium salt is dissolved in an ion conductive polymer, and a liquid electrolyte in which a lithium salt is dissolved in an organic solvent can be used while being held in a porous substrate layer.

  Examples of ion conductive polymers used for polymer electrolytes include polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinylidene fluoride (PVDF), hexafluoropropylene, polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethyl Examples thereof include methacrylate (PMMA) and copolymers thereof.

  Examples of the organic solvent used for the liquid electrolyte include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl Carbonates such as carbonate (EMC) and methyl propyl carbonate (MPC) can be mentioned.

The lithium _{salt, Li (CF 3 SO 2)} 2 N, Li (C 2 F 5 SO 2) 2 N, LiPF 6, LiBF 4, LiAsF 6, LiTaF 6, LiClO 4, compounds such as LiCF ₃ SO ₃ is It can be mentioned.

  Although the material which forms a porous base layer is not specifically limited, It is preferable to use thermoplastic resins, such as polyethylene, a polypropylene, and an ethylene-propylene copolymer. The porosity of the porous substrate layer is not particularly limited, but is preferably 40% to 85%. When the porosity is 40% or more, sufficient ion conductivity can be obtained. On the other hand, when the porosity is 85% or less, the strength of the porous substrate layer can be maintained well.

(Positive electrode tab 60 and negative electrode tab 65)
The positive electrode tab 60 can electrically connect the positive electrode current collector 11 and an external device of the lithium ion secondary battery 100. In addition, the negative electrode tab 65 can electrically connect the negative electrode current collector 21 and a device outside the lithium ion secondary battery 100. The material for forming the positive electrode tab 60 and the negative electrode tab 65 is not particularly limited. For example, at least one metal selected from the group consisting of aluminum, copper, titanium, and nickel can be used. The materials forming the positive electrode tab 60 and the negative electrode tab 65 may be the same or different.

(Exterior body 70)
The exterior body 70 can accommodate the unit cell layer 40 or the power generation element 50. The exterior body 70 is, for example, a can or one formed of a film. Further, the shape of the exterior body 70 is not particularly limited, and may be cylindrical, square, or sheet. Although not particularly limited, it is preferable that the exterior body 70 be formed of a film from the viewpoint of downsizing and weight reduction. Among them, from the viewpoint of achieving high output and cooling performance, the film is preferably a laminate film, and the laminate film preferably contains aluminum. The lithium ion secondary battery 100 is preferably a flat laminated lithium ion secondary battery. Such a lithium ion secondary battery can be made to have high discharge capacity and heat radiation performance, and thus is most suitable for being mounted in a vehicle. An example of a laminate film containing aluminum is a PP / aluminum / nylon three-layer laminate film.

  As mentioned above, the electric device of this embodiment is provided with the above-mentioned electrode for electric devices. Therefore, according to the electrical device of the present embodiment, a highly reliable electrical device can be provided.

[Method of producing electrode slurry]
The manufacturing method of the electrode slurry of this embodiment is demonstrated. In addition, description is abbreviate | omitted about the part which overlaps with embodiment mentioned above. In the electrode slurry, even if the electrode is manufactured under a predetermined condition or a raw material that does not generate a crack, if the lot of the raw material is different, there is a possibility that a crack may be generated in the mixture layer. Such cracks can not be confirmed unless the electrode slurry is subjected to heat treatment once to form a mixture layer, and when the occurrence of cracks is found during production, a large amount of forming loss may occur. . In addition, even when the electrode slurry sampled in advance is heat-treated to form a mixture layer, it takes a lot of time, which is not efficient.

  So, the manufacturing method of the electrode slurry of this embodiment is provided with a mixing process and a stirring process. And in a stirring process, it stirs until the number of the yield in 15 Pa-200 Pa of the shear stress-distortion curve measured by the rheometer becomes one. In the present embodiment, by providing such a stirring step, it is possible to provide an electrode slurry capable of suppressing the occurrence of cracks in the mixture layer and reducing the formation loss of the electrode by a simple method. Hereinafter, the configuration of the present embodiment will be described in detail.

(Mixing process)
In the mixing step, the active material particles, the conductive auxiliary agent, the solvent, and the binder precursor are mixed to obtain a mixed solution. As the active material particles, the conductive additive, the solvent and the binder precursor, those described in the embodiment of the electrode slurry can be used.

  The mixing method is not particularly limited, and the active material particles, the conductive additive, the solvent, and the binder precursor can be mixed by a known method. As a mixing method, active material particles, a conductive support agent, and a binder precursor can be dispersed in a solvent using, for example, a single-screw kneader, a twin-screw kneader, a planetary mixer, a kneader, or the like. The binder precursor is preferably dispersed in a solvent in advance.

(Stirring process)
In the stirring step, the mixed solution is stirred until the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one. In the present embodiment, since such a stirring step is included, the occurrence of cracks can be suppressed before forming the mixture layer. Therefore, the forming loss of the electrode can be reduced.

  The method for stirring the electrode slurry is not particularly limited. For example, the electrode slurry can be stirred using a single-screw kneader, a twin-screw kneader, a planetary mixer, a kneader, or the like.

  Further, the method of making the number of yield of the electrode slurry one is not particularly limited, but for example, the method of making the number of yield one by increasing the rotational speed of the kneader or prolonging the rotational time may be mentioned.

  As mentioned above, the manufacturing method of the electrode slurry of this embodiment is provided with a mixing process and a stirring process. In the mixing step, the active material particles, the conductive auxiliary agent, the solvent, and the binder precursor are mixed to obtain a mixed solution. In the stirring step, the mixed solution is stirred until the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one. In the present embodiment, by including such a step, it is possible to adjust the electrode slurry while predicting generation of a crack generated in the mixture layer by a simple method. Therefore, according to the electrode slurry manufactured in this manner, the forming loss of the electrode can be reduced.

[Method of manufacturing electrode for electric device]
The manufacturing method of the electrode for electric devices of this embodiment is demonstrated. In addition, description is abbreviate | omitted about the part which overlaps with embodiment mentioned above. The manufacturing method of the electrode for electric devices of this embodiment is provided with the mixture layer formation process of coating and heat-treating the electrode slurry manufactured by the manufacturing method of the electrode slurry mentioned above on a base material, and forming a mixture layer. . Specifically, the method for manufacturing an electrode for an electric device of the present embodiment includes a mixing step, a stirring step, and a mixture layer forming step. About a mixing process and a stirring process, it can be set as the process similar to the manufacturing method of electrode slurry. That is, in the mixing step, the active material particles, the conductive auxiliary agent, the solvent, and the binder precursor are mixed to obtain a mixed solution. In addition, in the stirring step, the mixed solution is stirred until the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one to obtain an electrode slurry.

(Mixture layer forming process)
In the mixture layer forming step, the electrode slurry of which the yield becomes one in the stirring step is applied to a substrate and heat-treated to form a mixture layer. That is, in the mixture layer forming step, the electrode slurry is coated and heat-treated on a substrate to form a mixture layer. The electrode slurry coated on the substrate can form a mixture layer by such coating and heat treatment.

  The method for applying the electrode slurry to the substrate is not particularly limited, and known methods such as spray coating, roll coating, doctor blade, flow coating, dip coating, screen printing, and ink jet are used. be able to.

  The electrode slurry can be coated on at least one side of the substrate. The thickness and the area for applying the electrode slurry are not particularly limited, and may be appropriately adjusted according to the properties of the electrode slurry and the use of the electrode.

  The method of heat-treating the electrode slurry coated on the substrate is not particularly limited, and known methods such as a hot plate method, a hot air drying method, a vacuum drying method, and a far-infrared drying method can be used.

  In the present embodiment, the heat treatment can include a drying step of volatilizing the solvent, and a reaction step of reacting the binder precursor into a binder. These steps may be performed collectively at one time, or may be performed separately in multiple times.

  In the drying step, the solvent in the coated electrode slurry can be volatilized. The volatilization of the solvent in the electrode slurry may be carried out in a plurality of divided steps, for example, once when placed on one side of the current collector, and twice when placed on both sides .

  Although the temperature of a drying process is not specifically limited, 60 to 130 degreeC is preferable and 70 to 110 degreeC is more preferable. By setting the drying temperature in such a range, the solvent of the mixture layer can be volatilized with high reliability and high productivity. Also, the drying step may be performed under reduced pressure to accelerate the volatilization of the solvent.

  Although the temperature of a reaction process is not specifically limited, 120 degreeC-350 degreeC is preferable, and 200 degreeC-320 degreeC is more preferable. By setting the reaction temperature within such a range, the mixture layer can be formed with high reliability and high productivity. The reaction step may be carried out under reduced pressure in order to accelerate the volatilization of the residual solvent.

  The mixture layer formed by the heat treatment may be pressed if necessary in order to improve the density of the electrode. The pressing step is not particularly limited, and for example, a calender roll, a flat plate press, etc. can be used.

  As mentioned above, the manufacturing method of the electrode for electric devices of this embodiment is a mixture layer which coats and heat-treats the electrode slurry manufactured by the manufacturing method of the electrode slurry mentioned above on a base material, and forms a mixture layer. The formation process is provided. According to the method of manufacturing an electrode for an electric device of the present embodiment, it is possible to suppress the occurrence of cracks in the mixture layer.

[Method of manufacturing electrical device]
The manufacturing method of the electric device of this embodiment is equipped with the manufacturing method of the said electrode for electric devices. According to the method of manufacturing an electrode for an electric device described above, the occurrence of cracks in the mixture layer can be suppressed. Therefore, by manufacturing an electrical device using the electrode manufactured by the method for manufacturing an electrode for an electrical device, the risk of the crack breaking the separator and contacting with the other electrode can be reduced. . Therefore, according to the method of manufacturing an electrical device of the present embodiment, a highly reliable electrical device can be provided.

  Hereinafter, although this embodiment is described in more detail by an example and a comparative example, this embodiment is not limited to these.

Example 1
A mixed solution of 64 parts by mass of the active material, 4 parts by mass of the conductive aid, 38.7 parts by mass of the binder precursor dispersion having a solid content concentration of 20% by mass, and 26.2 parts by mass of the solvent I got The active material is a silicon alloy, the conductive agent is an equivalent amount of acetylene black and carbon fiber, the binder precursor is a polyamic acid using N-methyl-2-pyrrolidone (NMP) as a dispersion medium, and the solvent is N-methyl- 2-pyrrolidone (NMP) was used.

  Next, the rotor (wheel) of a thin-film spinning high-speed mixer (Filmix 56-30 manufactured by Primix, Inc.) is rotated at 6 m / sec for 300 seconds, and the mixing obtained as described above is performed. The solution was stirred to obtain an electrode slurry.

  A part of the electrode slurry obtained as described above was sampled, and a shear stress-strain curve was created with a rheometer. As a result, only one yield was confirmed at a position of about 25 Pa. The results are shown in FIG.

  Next, the above electrode slurry was uniformly coated at a coating speed of 100 mm / min with an applicator so that the thickness of the mixture layer after drying was 50 μm on one surface of the current collector. As a current collector, a copper alloy foil with a thickness of 12 μm was used.

  Next, the electrode slurry coated on the current collector was dried in vacuum for 24 hours, and dried and fired in vacuum at 300 ° C. for 1 hour to form a mixture layer, to obtain an electrode.

Comparative Example 1
An electrode was produced in the same manner as in Example 1 except that the rotor (wheel) was rotated at 6 m / s for 180 seconds. In addition, when a part of electrode slurry was sampled and a shear stress-strain curve was created with a rheometer, two yield points were confirmed at about 18 Pa and about 44 Pa. The results are shown in FIG.

Comparative Example 2
An electrode was produced in the same manner as in Example 1 except that the rotor (wheel) was rotated at 6 m / sec for 60 seconds. In addition, when a part of electrode slurry was sampled and a shear stress-strain curve was created with a rheometer, two yield points were confirmed at about 22 Pa and about 47 Pa. The results are shown in FIG.

[Evaluation]
The number of yieldings and the presence or absence of cracks were evaluated as follows.

[Number of surrenders]
The number of yielding is applied by continuously increasing the shear stress to the electrode slurry under the following conditions by a rheometer, and a shear stress-strain curve is created by measuring the strain at that time, and the number of yielding is calculated from this graph. evaluated. The results are shown in FIG.

Measuring device: Cone-plate viscometer (R / S rheometer made by BROOKFIELD)
Measurement temperature: room temperature (25 ° C)
Sample volume: 0.08 mL
Upper plate: 25 mm diameter conical plate (Model: RC3-25-1)
Lower plate: distance between flat plates 25 mm in diameter: 50 μm
Stress measurement range: 10Pa to 250Pa
Scanning speed: + 1Pa / sec

[Presence of crack]
The appearance of the surface of the mixture layer was visually confirmed for the electrodes of Examples and Comparative Examples. The results of Example 1 and Comparative Example 2 are shown in FIGS. 4 and 5, respectively.

  The electrode slurry of Example 1 was sufficiently stirred, and only one yield could be confirmed in the shear stress-strain curve. Therefore, as shown in FIG. 4, no crack could be confirmed in the mixture layer after the heat treatment. On the other hand, since the electrode slurry of Comparative Example 1 and Comparative Example 2 did not have sufficient stirring time, a yield of 2 was confirmed in the shear stress-strain curve. Therefore, as in Comparative Example 2 shown in FIG. 5, cracks occurred in the mixture layer after drying.

  As mentioned above, although the present invention was explained by the example and comparative example, the present invention is not limited to these and various modification is possible within the limits of the present invention.

10 Positive electrode (electrode for electric device)
11 Positive current collector (base material)
12 Positive electrode mixture layer (mixture layer)
20 Negative electrode (electrode for electric device)
21 Negative electrode current collector (base material)
22 Negative electrode mixture layer (mixture layer)
100 lithium ion rechargeable battery (electrical device)

Claims (7)

An active material particle, a conductive auxiliary agent, a solvent, and a binder precursor,
The electrode slurry whose number of the yield in 15 Pa-200 Pa of the shear stress-strain curve measured by the rheometer is one.   The electrode slurry according to claim 1, wherein the active material particles are silicon-based particles, the conductive aid is carbon particles, and the solvent is an organic solvent.   The electrode slurry according to claim 1, wherein the solvent is N-methyl-2-pyrrolidone.   The electrode slurry according to any one of claims 1 to 3, wherein the binder precursor is a polymer precursor.   The said binder precursor is a polyamic acid, The electrode slurry of any one of Claims 1-4. Mixing the active material particles, the conductive auxiliary agent, the solvent, and the binder precursor to obtain a mixed solution;
Stirring the mixed solution until the number of yielding at 15 Pa to 200 Pa of the shear stress-strain curve measured by the rheometer is one;
A method of producing an electrode slurry comprising:   A method of manufacturing an electrode for an electric device, comprising: a mixture layer forming step of coating and heat treating the electrode slurry manufactured by the method of manufacturing an electrode slurry according to claim 6 on a substrate to form a mixture layer.