JP2017195055A - Method for manufacturing positive electrode slurry for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a positive electrode slurry for a lithium ion secondary battery, which can achieve a suitable initial viscosity and a suitable temporal viscosity without using a thickening inhibitor.SOLUTION: A method for manufacturing a positive electrode slurry for a lithium ion secondary battery comprises the steps of: (1) coating a residual alkaline component-containing positive electrode active material for a nonaqueous electrolyte secondary battery with at least a conductive material, thereby obtaining a positive electrode mixture for a nonaqueous electrolyte secondary battery; and (2) adding an organic solvent to the positive electrode mixture for a nonaqueous electrolyte secondary battery obtained in the step (1), thereby obtaining the positive electrode slurry for a nonaqueous electrolyte secondary battery.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery. In more detail, this invention relates to the manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries which can implement | achieve suitable initial viscosity and time-dependent viscosity, without using a thickening inhibitor.

  Conventionally, by suppressing the thickening and gelation caused by the alkali component of the positive electrode mixture slurry, the application work of the positive electrode mixture slurry to the current collector is simplified, and the purpose is to suppress a decrease in yield. A method for producing a positive electrode for a lithium ion secondary battery has been proposed (see Patent Document 1).

  This method for producing a positive electrode for a lithium ion secondary battery comprises mixing a positive electrode active material capable of occluding and releasing lithium ions, a nitrile group-containing polymer as a thickening inhibitor, a binder, and an organic solvent to prepare a positive electrode mixture slurry. Including a preparation step, 0.001 to 0.5 parts by weight of the nitrile group-containing polymer is mixed with 100 parts by weight of the positive electrode active material.

JP2012-89312A

  By the way, in the positive electrode for lithium ion secondary batteries manufactured by the manufacturing method of the positive electrode for lithium ion secondary batteries described in Patent Document 1, thickening which is a component other than the positive electrode active material, the conductive material, and the binder. An inhibitor will be included. Therefore, various problems such as a decrease in volume energy density may occur due to the inclusion of the thickening inhibitor.

  The present invention has been made in view of such problems of the prior art. And an object of this invention is to provide the manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries which can implement | achieve a suitable initial viscosity and a time-dependent viscosity, without using a thickening inhibitor.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, it was found that the above object can be achieved by coating the positive electrode active material for a non-aqueous electrolyte secondary battery containing a residual alkali component with at least a conductive material to obtain a positive electrode mixture for a non-aqueous electrolyte secondary battery. The invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries which can implement | achieve suitable initial viscosity and a time-dependent viscosity can be provided, without using a thickening inhibitor.

FIG. 1 is a flowchart showing a method for producing a positive electrode slurry for a lithium ion secondary battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an outline of an example of a positive electrode mixture for a lithium ion secondary battery. FIG. 3 is a cross-sectional view schematically illustrating another example of the positive electrode composite material for a lithium ion secondary battery. FIG. 4 is a cross-sectional view showing an outline of still another example of the positive electrode composite material for a lithium ion secondary battery. FIG. 5 is a flowchart showing an example of the step (1) shown in FIG. FIG. 6 is a flowchart showing another example of the step (1) shown in FIG. FIG. 7 is a flowchart showing still another example of the step (1) shown in FIG. FIG. 8 is a flowchart showing still another example of the step (1) shown in FIG. FIG. 9 is a flowchart showing an example of the step (2) shown in FIG. FIG. 10 is a graph showing the relationship between the particle sizes of the active material and the conductive material and the power unit.

  Hereinafter, the manufacturing method of the positive electrode slurry for non-aqueous electrolyte secondary batteries which concerns on one Embodiment of this invention is demonstrated in detail, referring drawings. The positive electrode slurry for a lithium ion secondary battery will be described as an example of the positive electrode slurry for a non-aqueous electrolyte secondary battery.

  FIG. 1 is a flowchart showing a method for producing a positive electrode slurry for a lithium ion secondary battery according to an embodiment of the present invention. As shown in FIG. 1, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries of this embodiment includes the following process (1) and process (2). In the figure, step (1) is abbreviated as S1 (the same applies hereinafter).

  Step (1) is a step of obtaining a positive electrode mixture for a lithium ion secondary battery by coating at least a conductive material with a residual alkaline component-containing positive electrode active material for a lithium ion secondary battery.

  Step (2) is a step of obtaining a positive electrode slurry for a lithium ion secondary battery by adding an organic solvent to the positive electrode mixture for a lithium ion secondary battery obtained in step (1).

  Thus, before the organic solvent is added to obtain the positive electrode slurry for the lithium ion secondary battery, the residual alkali component-containing positive electrode active material for the lithium ion secondary battery is almost uniformly coated with the conductive material, so that the lithium ion A positive electrode composite material for a secondary battery can be obtained. Thereby, without using a thickening inhibitor, it is possible to suppress an increase in pH in the vicinity of the binder due to elution of the alkali component. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve suitable initial stage viscosity and time-dependent viscosity can be provided. Then, the occurrence of discharge failure when the positive electrode slurry for lithium ion secondary batteries is applied to the current collector, and the streak in the coating film formed by applying the positive electrode slurry for lithium ion secondary batteries to the current collector It is possible to suppress the occurrence of coating film defects such as.

  Further, since it is not necessary to use a thickening inhibitor that is a component other than the positive electrode active material, the conductive material, and the binder, there is no possibility that various problems such as a decrease in volume energy density occur. Furthermore, there is a secondary advantage that an increase in cost due to the use of the thickening inhibitor can be avoided.

  In addition, although not particularly limited, the step (1) includes coating a positive electrode active material for a lithium ion secondary battery containing a residual alkali component with a conductive material and a binder, and a positive electrode for a lithium ion secondary battery. It may be a step of obtaining a composite material.

  Even in this case, before adding the organic solvent to obtain the positive electrode slurry for the lithium ion secondary battery, the residual alkaline component-containing positive electrode active material for the lithium ion secondary battery is almost uniformly coated with the conductive material, A positive electrode mixture for an ion secondary battery can be obtained. Thereby, without using a thickening inhibitor, it is possible to suppress an increase in pH in the vicinity of the binder due to elution of the alkali component. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve suitable initial stage viscosity and time-dependent viscosity can be provided. As a result, in the coating film formed by applying a positive electrode slurry for a lithium ion secondary battery to a current collector or generating a discharge failure when the lithium ion secondary battery positive electrode slurry is applied to a current collector Occurrence of coating film defects such as streaks can be suppressed.

  In the case where the binder is not added in the step (1), for example, the binder may be added when the organic solvent is added in the step (2).

  Further, although not particularly limited, in the step (1), it is preferable to use a uniaxial mixer having a rotating blade and a fixed blade and having a constant clearance between the rotating blade and the fixed blade. When such a uniaxial mixer, specifically, a uniaxial continuous kneading extruder (for example, Asada Tekko Co., Ltd. (Miracle K.C.K.) can be used), a thickening inhibitor is used. In addition, an increase in pH in the vicinity of the binder due to elution of the alkali component can be suppressed. Thereby, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a suitable initial stage viscosity and time-dependent viscosity can be provided. Furthermore, since an appropriate shearing force can be applied, the residual alkali component-containing positive electrode active material for lithium ion secondary batteries can be more evenly coated with the conductive material.

  In addition, although not particularly limited, in the step (1), it has a temperature adjusting device that adjusts the temperature of the positive electrode mixture for lithium ion secondary batteries when mixing the rotating blade and the fixed blade, A single screw mixer is used in which the clearance between the rotating blade and the fixed blade is constant, and the temperature adjusting device adjusts the temperature when mixing the positive electrode mixture for the lithium ion secondary battery to 70 ° C. or lower, preferably 50 ° C. or lower. It is preferable. When such a uniaxial mixer, specifically, a uniaxial continuous kneading extruder (for example, Asada Tekko Co., Ltd. (Miracle K.C.K.) can be used), a thickening inhibitor is used. In addition, it is possible to suppress increase in viscosity and gelation due to temperature increase caused by frictional heat of the active material or the like due to elution of the alkaline component in the vicinity of the binder. Thereby, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided. Furthermore, since an appropriate shearing force can be applied, the residual alkali component-containing positive electrode active material for lithium ion secondary batteries can be uniformly coated with a conductive material. Note that the temperature adjusting device includes, for example, a cooling device that uses a medium such as water in a mixing container of a positive electrode mixture for a lithium ion secondary battery in which a rotating blade and a fixed blade are accommodated. In order to adjust the temperature to 50 ° C. or lower, for example, it is preferable to flow cold water of 10 ° C. or lower. Moreover, the temperature control apparatus may be equipped with the cooling device in the position where the positive electrode mixture for lithium ion secondary batteries is discharged.

  Furthermore, although not particularly limited, in the case of using the above-described uniaxial mixer in the step (1), the total of the remaining alkaline component-containing positive electrode active material for lithium ion secondary battery, conductive material and binder. It is preferable that the feed amount is 1 to 5 kg / h, the rotation speed of the rotary blade is 30 to 90 rpm, and the peripheral speed of the rotary blade is 1.0 m / s or more. If the peripheral speed of the rotating blade is within such a range, a more appropriate shear force can be applied. On the other hand, when the total feed amount and the rotation speed of the rotary blade are within such a range, for example, since the filling amount is small, material crushing can be suppressed. Thereby, without using a thickening inhibitor, it is possible to suppress the increase in viscosity and gelation due to the increase in pH in the vicinity of the binder due to the elution of the alkali component and the increase in temperature caused by frictional heat such as the active material. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided. Furthermore, since an appropriate shearing force can be applied, the residual alkali component-containing positive electrode active material for lithium ion secondary batteries can be more evenly coated with the conductive material.

In addition, although not particularly limited, in the step (1), when the above-described uniaxial mixer is used, the materials of the prepared positive electrode mixture for the lithium ion secondary battery (positive electrode active material and conductive material) D50 3 cube of numerical few microns in particle size numeric (d ³⁾ a clearance micrometers of (c) (where, satisfying 50 ≦ c ≦ 150.) values when the division at ( It is preferable to use a uniaxial mixer that satisfies the relationship of (display value of load power) to (display value of load power) +1. In addition, (the display value of load power) means the value at the time of idling, and the display value of load power when the material is actually input becomes larger than this.

  Here, each configuration will be described in more detail.

(Residual alkali component-containing positive electrode active material for lithium ion secondary battery)
As the positive electrode active material for a lithium ion secondary battery containing the residual alkali component described above, for example, for a lithium ion secondary battery obtained by a method for producing a positive electrode active material for a lithium ion secondary battery including a step of removing an alkali component A positive electrode active material can be mentioned. Such a positive electrode active material for a lithium ion secondary battery usually contains a trace amount of an alkaline component. Moreover, as a positive electrode active material for lithium ion secondary batteries, for example, a lithium transition metal composite oxide containing lithium and a transition metal element can be used. Further, the lithium transition metal composite oxide includes a phosphate compound containing lithium and a transition metal element, a solid solution containing lithium and a transition metal element, and the like. Moreover, these may be used individually by 1 type and may be used in combination of 2 or more type. Moreover, you may mix the thing from which D50 particle diameter differs about 1 type.

  Here, in this specification, “particle diameter” means, for example, an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) unless otherwise specified as “D50 particle diameter”. This means the maximum distance among any two points on the contour line of the active material, conductive material, etc. (observation surface) observed.

Specific examples of the lithium transition metal composite oxide include lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium nickel cobalt composite oxide (LiNiCoO ₂ ), lithium nickel manganese composite oxide ( LiNi _0.5 Mn _1.5 O ₄ ), lithium nickel manganese cobalt composite oxide (Li (NiMnCo) O ₂ , Li (LiNiMnCo) O ₂ ), lithium manganese composite oxide having a spinel structure (LiMn ₂ O ₄₎ ) And the like.

Specific examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) and a lithium iron manganese phosphate compound (LiFeMnPO ₄ ). In these composite oxides, for example, for the purpose of stabilizing the structure, a part of the transition metal may be substituted with another element.

Furthermore, as a specific example of a solid solution containing lithium and a transition metal element, xLiM ^I O _2. (1-x) Li ₂ M ^II O ₃ (0 <x <1, M ^I has an average oxidation state of 3+, M ^II Is one or more transition metal elements having an average oxidation state of 4+), LiM ^III O ₂ —LiMn ₂ O ₄ (M ^III is a transition metal element such as Ni, Mn, Co, Fe).

(Conductive material)
The conductive material is not particularly limited as long as conductivity can be imparted, but a carbon material can be cited as a suitable example. As the carbon material, for example, carbon black such as acetylene black, channel black, thermal black, ketjen black, etc., and one kind of powdery carbon such as graphite, carbon nanotube, carbon nanohorn are used alone or in combination of two or more kinds. It is preferable. However, it is not limited to these, For example, carbon fibers, such as a vapor growth carbon fiber, can also be used.

Further, although not particularly limited, it is preferable to use, for example, a porous conductive material having pores into which a residual alkali component can enter as the conductive material. In addition, although it does not specifically limit, It is preferable that a BET specific surface area is 10-100 m < ² > / g, for example. Examples of such a porous conductive material include acetylene black and carbon black produced by high-temperature firing. Alkali components such as hydroxide ions have a particle size of less than 10 nm. Therefore, for example, an alkaline component can be captured by using a porous conductive material having pores of about 1 to 20 nm. Thereby, without using a thickening inhibitor, it is possible to suppress thickening and gelation due to pH increase in the vicinity of the binder due to elution of the alkali component. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  Further, although not particularly limited, as the conductive material, for example, the content of the conductive material having a particle diameter of 20 μm or more is preferably 25 ppm by volume or less. By setting the particle size within such a range that there are few large particles, the positive electrode active material for a lithium ion secondary battery containing a residual alkali component can be more evenly coated with a certain amount of conductive material. Thereby, without using a thickening inhibitor, it is possible to suppress thickening and gelation due to pH increase in the vicinity of the binder due to elution of the alkali component. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  Moreover, although it does not specifically limit, As a electrically conductive material, it is preferable that content of sulfur is 0.03 mass% or less, for example. By setting the content of impurities such as sulfur that may react with the alkali component within such a range, for example, an increase due to a temperature rise caused by heat of reaction with the alkali component without using a thickening inhibitor. Viscosity and gelation can be suppressed. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

(Binder)
Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). ), Ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), or the like is preferably used. Among these, it is preferable to use polyvinylidene fluoride (PVDF). However, it is not limited to these, For example, the conventionally well-known thing used for lithium ion secondary batteries, such as a polyimide, a styrene butadiene rubber, carboxymethylcellulose, polyethylene, a polypropylene, a polyacrylonitrile, polyamide, can also be used. Moreover, these may be used individually by 1 type and may be used in combination of 2 or more type.

(Organic solvent)
As the above-mentioned organic solvent, N-methyl-2-pyrrolidone (NMP) can be cited as a preferred example, but is not limited thereto. A conventionally well-known thing used for manufacture of a lithium ion secondary battery can also be used.

  FIG. 2 is a cross-sectional view illustrating an outline of an example of a positive electrode mixture for a lithium ion secondary battery. Moreover, FIG. 3 is sectional drawing which shows the outline of another example of the positive electrode compound material for lithium ion secondary batteries. FIG.2 and FIG.3 is the positive mix for lithium ion secondary batteries in the positive electrode slurry for lithium ion secondary batteries obtained by the manufacturing method of the positive electrode slurry for lithium ion secondary batteries of this embodiment. In the positive electrode slurry for a lithium ion secondary battery, a positive electrode active material, a conductive material, and a binder for a lithium ion secondary battery are impregnated with an organic solvent (not shown).

  As shown in FIGS. 2 and 3, the lithium ion secondary battery positive electrode composites 1 and 2 are substantially uniformly covered with the conductive material 20 by the positive electrode active material 10 for lithium ion secondary batteries. Further, the binder 30 is also coated almost uniformly. The positive electrode composites 1 and 2 for lithium ion secondary batteries differ in the degree of adhesion of the binder 30 to the positive electrode active material 10 for lithium ion secondary batteries. As will be described in detail later, the positive electrode mixture for lithium ion secondary batteries as shown in FIG. 2 and the positive electrode mixture for lithium ion secondary batteries as shown in FIG. The ratio of is different. When the positive electrode active material for a lithium ion secondary battery containing a residual alkali component is coated with a conductive material before the binder, it is easy to obtain the positive electrode mixture for a lithium ion secondary battery shown in FIG.

  FIG. 4 is a cross-sectional view showing an outline of still another example of the positive electrode composite material for a lithium ion secondary battery. FIG. 4 shows a positive electrode mixture for a lithium ion secondary battery in a positive electrode slurry for a lithium ion secondary battery obtained by a method for producing a positive electrode slurry for a lithium ion secondary battery outside the present invention. In the positive electrode slurry for a lithium ion secondary battery, a positive electrode active material, a conductive material, and a binder for a lithium ion secondary battery are impregnated with an organic solvent (not shown).

  As shown in FIG. 4, in the positive electrode mixture 100 for a lithium ion secondary battery, the positive electrode active material 10 for a lithium ion secondary battery is covered with a conductive material 20 and a binder 30. However, it is not evenly coated with the conductive material 20. From the positive electrode active material 10 for the lithium ion secondary battery in such a positive electrode mixture for the lithium ion secondary battery, the eluted alkaline component tends to act on the binder, and the viscosity of the positive electrode slurry for the lithium ion secondary battery is increased. And gelation easily proceeds. At the present time, the alkali component is present from the pores of the positive electrode active material for a lithium ion secondary battery containing a residual alkali component or an exposed surface newly formed upon mixing (hereinafter sometimes referred to as “elution site”). I think it is eluting.

  Step (1) will be described in more detail.

  FIG. 5 is a flowchart showing an example of the step (1) shown in FIG. As shown in FIG. 5, in the method for producing a positive electrode slurry for a lithium ion secondary battery of this example, the step (1) includes the following steps (1-1) and (1-2).

  Step (1-1) is a step of obtaining a positive electrode mixture precursor for a lithium ion secondary battery by covering the positive electrode active material for a lithium ion secondary battery containing a residual alkali component with a conductive material.

  In the step (1-2), the positive electrode mixture precursor for the lithium ion secondary battery obtained in the step (1-1) is covered with a binder to obtain a positive electrode mixture for the lithium ion secondary battery. It is.

  As described above, by covering the positive electrode active material for a lithium ion secondary battery containing a residual alkali component with a conductive material, it is easy to cover the elution site with the conductive material almost without using a thickening inhibitor. An increase in pH in the vicinity of the binder due to elution of the alkali component can be further suppressed. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  FIG. 6 is a flowchart showing another example of the step (1) shown in FIG. As shown in FIG. 6, in the method for producing the positive electrode slurry for the lithium ion secondary battery of this example, the step (1) includes the following steps (1-1 ′) to (1-3 ′).

  Step (1-1 ') is a step of crushing the conductive material to obtain crushing conductivity.

  In the step (1-2 ′), the positive electrode active material for a lithium ion secondary battery containing the residual alkali component is coated with the pulverized conductive material obtained in the step (1-1 ′), and the positive electrode for a lithium ion secondary battery This is a step of obtaining a composite precursor.

  In the step (1-3 ′), the positive electrode mixture precursor for the lithium ion secondary battery obtained in the step (1-2 ′) is covered with a binder, and the positive electrode mixture for the lithium ion secondary battery is coated. It is a process to obtain.

  As described above, by covering the positive electrode active material for lithium ion secondary battery containing residual alkali component with the pulverized conductive material, it is easy to cover the elution site with the conductive material almost uniformly. It is difficult to increase the elution site derived from the newly formed exposed surface when the positive electrode active material for the secondary battery is mixed. Furthermore, the binder which an alkali component can act on can be suppressed to a local portion. Therefore, without using a thickening inhibitor, an increase in pH in the vicinity of the binder due to elution of the alkali component can be further suppressed. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  FIG. 7 is a flowchart showing still another example of the step (1) shown in FIG. As shown in FIG. 7, in the method for producing a positive electrode slurry for a lithium ion secondary battery of this example, the step (1) includes the following steps (1-1 ″) to (1-3 ″).

  Step (1-1 ″) is a step of crushing the conductive material to obtain a crushed conductive material.

  Step (1-2 ″) is a step in which the pulverized conductive material obtained in step (1-1 ″) and the binder are mixed to obtain a mixture.

  In the step (1-3 ″), the positive electrode active material for a lithium ion secondary battery containing a residual alkali component is coated with the mixture obtained in the step (1-2 ″), and the positive electrode composite for a lithium ion secondary battery is coated. This is a process for obtaining a material.

  As described above, by covering the positive electrode active material for lithium ion secondary battery containing residual alkali component with the pulverized conductive material, it is easy to cover the elution site with the conductive material almost uniformly. The elution site originating from the exposed surface newly formed during the mixing of the positive electrode active material for the secondary battery is less likely to increase. Furthermore, the binder which an alkali component can act on can be suppressed to a local portion. Therefore, without using a thickening inhibitor, an increase in pH in the vicinity of the binder due to elution of the alkali component can be further suppressed. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  FIG. 8 is a flowchart showing still another example of the step (1) shown in FIG. As shown in FIG. 8, in the method for producing a positive electrode slurry for a lithium ion secondary battery of this example, the step (1) includes the following step (1-1 ′ ″).

  Step (1-1 ′ ″) is a step of obtaining a positive electrode mixture for a lithium ion secondary battery by coating a positive electrode active material for a lithium ion secondary battery containing a residual alkali component with a mixture of a conductive material and a binder. It is.

  As described above, by covering the positive electrode active material for a lithium ion secondary battery containing a residual alkali component with a mixture of a conductive material and a binder, it is easy to cover the elution site with the conductive material almost uniformly. The elution site derived from the exposed surface newly formed at the time of mixing the component-containing lithium ion secondary battery positive electrode active material is less likely to increase. Furthermore, the binder which an alkali component can act on can be suppressed to a local portion. Therefore, without using a thickening inhibitor, an increase in pH in the vicinity of the binder due to elution of the alkali component can be further suppressed. As a result, the manufacturing method of the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a more suitable initial viscosity and time-dependent viscosity can be provided.

  Step (2) will be described in more detail.

  FIG. 9 is a flowchart showing an example of the step (2) shown in FIG. As shown in FIG. 9, in the method for producing a positive electrode slurry for a lithium ion secondary battery of this example, the step (2) includes the following steps (2-1) and (2-2).

  Step (2-1) is a step of obtaining a positive electrode slurry precursor for a lithium ion secondary battery by adding a predetermined small amount of an organic solvent to the positive electrode mixture for the lithium ion secondary battery obtained in step (1). is there.

  Step (2-2) is a step of further adding an organic solvent to the positive electrode slurry precursor for lithium ion secondary battery obtained in step (2-1) to obtain a positive electrode slurry for lithium ion secondary battery. .

  As described above, after adding a predetermined small amount of an organic solvent to the positive electrode mixture for a lithium ion secondary battery, the organic solvent is added in stages to suppress scattering of the positive electrode mixture for the lithium ion secondary battery. be able to. In addition, a shearing force suitable for dispersing the positive electrode mixture for a lithium ion secondary battery in an organic solvent can be imparted, so that granular aggregates, so-called lumps are less likely to occur. Furthermore, liquid absorption of the positive electrode mixture for lithium ion secondary batteries can be promoted. As a result, the positive electrode slurry for a lithium ion secondary battery can be produced efficiently.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to such an Example.

Example 1
First, 70 parts by mass of a positive electrode active material 1 for lithium ion secondary battery (composition: lithium manganese cobalt composite oxide, D50 particle size: 11 μm) and a positive electrode active material 2 for lithium ion secondary battery (composition: lithium manganese cobalt composite) 23 parts by mass of oxide, D50 particle size: 6 μm), 3 parts by mass of conductive material (type: carbon black, specific surface area: 64 m ² / g, D50 particle size: 3.6 μm), and binder (type: polyfluoride) 4 parts by weight of vinylidene chloride (PVDF) and a single-screw continuous kneading extruder (Asada Tekko Co., Ltd. (Miracle K.K.K), clearance: 1 mm, (material) Total feed amount: 3.6 kg / h, rotating blade Rotating speed: 60 rpm, peripheral speed of rotating blade: 1.5 m / s, cold water temperature in cooling device: 10 ° C. or less) To obtain a positive electrode for lithium ion secondary battery.

  Here, the shear stirring and mixing will be described in detail with reference to the drawings. FIG. 10 is a graph showing the relationship between the D50 particle diameter of a positive electrode mixture in which a positive electrode active material is coated with a conductive material and the power unit per material weight. The “power consumption per material weight” has a correlation with the torque in the uniaxial continuous kneading extruder, and in order to give an appropriate shearing force corresponding to a torque of 200 Wh / kg, the positive electrode mixture It can be seen that the D50 particle size is preferably small to some extent.

  Next, the obtained positive electrode mixture for a lithium ion secondary battery was put into a stirring / mixing vessel of a planetary biaxial mixer (Inoue Seisakusho Co., Ltd. (Trimix)), and N-methyl- A predetermined small amount of 2-pyrrolidone (NMP) was added and mixed with stirring for 15 minutes.

  Further, N-methyl-2-pyrrolidone (NMP) was added in several portions while flowing 50 ° C. warm water through the jacket of the container, and the mixture was stirred and mixed for a total of 125 minutes.

  Thereafter, N-methyl-2-pyrrolidone (NMP) is added so as to obtain a predetermined viscosity while flowing 50 ° C. warm water through the jacket of the container, and the mixture is mixed for 25 minutes. A positive electrode slurry for a battery was obtained.

(Comparative Example 1)
First, 70 parts by mass of a positive electrode active material 1 for lithium ion secondary battery (composition: lithium manganese cobalt composite oxide, D50 particle size: 11 μm) and a positive electrode active material 2 for lithium ion secondary battery (composition: lithium manganese cobalt composite) 23 parts by mass of oxide, D50 particle size: 6 μm), 3 parts by mass of conductive material (type: carbon black, specific surface area: 64 m ² / g, D50 particle size: 3.6 μm), and binder (type: polyfluoride) 4 parts by mass of vinylidene fluoride (PVDF) was put into a stirring and mixing vessel of a planetary twin-screw type mixer (Inoue Seisakusho Co., Ltd. (Trimix)), and N-methyl-2-pyrrolidone (NMP) ) Was added in a predetermined small amount and mixed with stirring for 15 minutes.

  Next, N-methyl-2-pyrrolidone (NMP) was added in several portions while flowing warm water of 50 ° C. through the jacket of the container, and the mixture was stirred and mixed for a total of 125 minutes.

  Thereafter, N-methyl-2-pyrrolidone (NMP) is added so as to obtain a predetermined viscosity while flowing 50 ° C. warm water through the jacket of the container, and the mixture is mixed for 25 minutes. A positive electrode slurry for a battery was obtained. A part of the specification of each example is shown in Table 1.

[Performance evaluation]
For the measurement sample (0.6 mL) of the positive electrode slurry for the lithium ion secondary battery in each example, using a viscometer (manufactured by Eiko Seiki Co., Ltd., digital viscometer DV-II + Pro), the initial viscosity after 60 minutes has elapsed. And the viscosity with time was measured after 2 weeks (336 hours). The obtained results are also shown in Table 1. In the initial viscosity determination and the time-dependent viscosity determination, “O” means that the required viscosity range of 5000 to 10,000 cP is satisfied, and “X” means that the required viscosity range of 5000 to 10,000 cP is not satisfied. To do.

  From Table 1, before adding an organic solvent, this invention which coat | covered the positive electrode active material for nonaqueous electrolyte secondary batteries containing a residual alkali component with at least electrically conductive material, and obtained the positive electrode compound material for nonaqueous electrolyte secondary batteries It can be seen that, in Example 1 belonging to the range, a positive electrode slurry for a lithium ion secondary battery capable of realizing suitable initial viscosity and time-dependent viscosity was obtained as compared with Comparative Example 1 outside the present invention.

  Moreover, since the used conductive material (a mixture of the positive electrode active material 1 and the positive electrode active material 2) is a porous conductive material having pores into which a residual alkali component can enter, a suitable initial viscosity and viscosity over time can be realized. It is thought that the positive electrode slurry for lithium ion secondary batteries was obtained.

  Furthermore, since the conductive material used (the mixture of the positive electrode active material 1 and the positive electrode active material 2) has a content of a conductive material having a particle size of 20 μm or more and 25 volume ppm or less, a suitable initial viscosity and viscosity over time are obtained. It is also considered that a positive electrode slurry for a lithium ion secondary battery that could be realized was obtained.

  Moreover, since the sulfur content of the used conductive material (a mixture of the positive electrode active material 1 and the positive electrode active material 2) is 0.03% by mass or less, a lithium ion secondary capable of realizing a suitable initial viscosity and viscosity over time. It is thought that the positive electrode slurry for batteries was obtained.

  Furthermore, since a positive electrode active material for a non-aqueous electrolyte secondary battery was obtained by coating a positive electrode active material for a non-aqueous electrolyte secondary battery containing a residual alkali component with at least a conductive material using a predetermined uniaxial mixer. It is thought that the positive electrode slurry for lithium ion secondary batteries which can implement | achieve initial viscosity and time-dependent viscosity was obtained.

  Further, using a predetermined uniaxial mixer, the temperature when mixing the positive electrode mixture for a nonaqueous electrolyte secondary battery is set to 70 ° C. or less, and the residual alkaline component-containing positive electrode active material for a nonaqueous electrolyte secondary battery is at least a conductive material It was considered that a positive electrode slurry for a lithium ion secondary battery capable of realizing a suitable initial viscosity and aging viscosity was obtained because the positive electrode mixture for a nonaqueous electrolyte secondary battery was obtained.

  Furthermore, using a predetermined uniaxial mixer, the residual alkaline component-containing non-aqueous electrolyte secondary battery positive electrode active material is coated with at least a conductive material to obtain a non-aqueous electrolyte secondary battery positive electrode mixture. The total feed rate of the positive electrode active material for the alkaline component-containing nonaqueous electrolyte secondary battery, the conductive material and the binder is 1 to 5 kg / h, the rotational speed of the rotating blade is 30 to 90 rpm, and the peripheral speed of the rotating blade is 1 Since it was 0.0 m / s or more, it is considered that a positive electrode slurry for a lithium ion secondary battery capable of realizing a suitable initial viscosity and viscosity with time was obtained.

  In addition, since the organic solvent was added stepwise to the positive electrode mixture for the non-aqueous electrolyte secondary battery so as to obtain a predetermined small amount, a positive electrode slurry for the non-aqueous electrolyte secondary battery was obtained. It is thought that the positive electrode slurry for lithium ion secondary batteries which can implement | achieve a viscosity was obtained.

  As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

  For example, in step (1), step (1-1) to step (1-2), step (1 to 1 ′) to step (1-3 ′), step (1 to 1 ″) to step ( 1-3 ″) and the steps (1-1 ′ ″) can be appropriately employed. Moreover, in the step (2), the steps (1-1) to (1-2) can be appropriately employed. And it can combine suitably in a process (1) and a process (2).

1,2,100 Positive electrode mixture for lithium ion secondary batteries (positive electrode mixture for nonaqueous electrolyte secondary batteries)
10 Positive electrode active material for lithium ion secondary battery (positive electrode active material for non-aqueous electrolyte secondary battery)
20 Conductive material 30 Binder

Claims (13)

It is a manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries, Comprising: The following process (1) and (2)
Step (1): A step of coating a positive electrode active material for a nonaqueous electrolyte secondary battery containing a residual alkali component with at least a conductive material to obtain a positive electrode mixture for a nonaqueous electrolyte secondary battery,
Step (2): adding an organic solvent to the positive electrode mixture for nonaqueous electrolyte secondary battery obtained in step (1) to obtain a positive electrode slurry for nonaqueous electrolyte secondary battery, A method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery.   Step (1) is a step of obtaining a positive electrode mixture for a non-aqueous electrolyte secondary battery by coating a positive electrode active material for a non-aqueous electrolyte secondary battery containing a residual alkali component with a conductive material and a binder. The manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries of Claim 1 characterized by the above-mentioned.   The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the conductive material is a porous conductive material having pores into which a residual alkali component can enter.   4. The positive electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the conductive material has a content of a conductive material having a particle size of 20 μm or more of 25 ppm by volume or less. 5. A method for producing a slurry.   The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the conductive material has a sulfur content of 0.03% by mass or less. Step (1) is the next step (1-1) and (1-2)
Step (1-1): A step of obtaining a positive electrode mixture precursor for a nonaqueous electrolyte secondary battery by coating a positive electrode active material for a nonaqueous electrolyte secondary battery containing a residual alkali component with a conductive material,
Step (1-2): The non-aqueous electrolyte secondary battery positive electrode mixture precursor obtained in the step (1-1) is covered with a binder to obtain a non-aqueous electrolyte secondary battery positive electrode mixture. The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 2, comprising a step. Step (1) is the next step (1-1 ′) to (1-3 ′)
Step (1-1 ′): a step of crushing the conductive material to obtain a crushed conductive material,
Step (1-2 ′): Residual alkali component-containing positive electrode active material for nonaqueous electrolyte secondary battery is coated with the pulverized conductive material obtained in step (1-1 ′), and used for nonaqueous electrolyte secondary battery. Obtaining a positive electrode mixture precursor;
Step (1-3 ′): The positive electrode mixture precursor for the nonaqueous electrolyte secondary battery obtained in the step (1-2 ′) is covered with a binder, and the positive electrode mixture for the nonaqueous electrolyte secondary battery is coated. The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 2, comprising the step of: Step (1) is the next step (1-1 ″) to (1-3 ″)
Step (1-1 ″): a step of crushing the conductive material to obtain a crushed conductive material,
Step (1-2 ″): a step of mixing the pulverized conductive material obtained in Step (1-1 ″) and the binder to obtain a mixture,
Step (1-3 ″): a positive electrode material for a nonaqueous electrolyte secondary battery obtained by coating the positive active material for a nonaqueous electrolyte secondary battery containing a residual alkali component with the mixture obtained in the step (1-2 ″). The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 2, comprising a step of obtaining a composite material. Step (1) is the next step (1-1 ′ ″)
Step (1-1 '''): A positive electrode active material for a nonaqueous electrolyte secondary battery containing a residual alkali component is coated with a mixture of a conductive material and a binder to obtain a positive electrode mixture for a nonaqueous electrolyte secondary battery. The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 2, comprising a step.   In the step (1), a uniaxial mixer having a rotating blade and a fixed blade and having a constant clearance between the rotating blade and the fixed blade is used. The manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries as described.   In the step (1), a temperature adjusting device for adjusting the temperature of the positive electrode mixture for the non-aqueous electrolyte secondary battery when mixing the rotating blade and the fixed blade is provided, and the clearance between the rotating blade and the fixed blade is constant. The temperature control device uses a uniaxial mixer that adjusts the temperature when mixing the positive electrode mixture for a non-aqueous electrolyte secondary battery to 70 ° C. or less. The manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries as described in any one of.   In the step (1), the total feed amount of the positive electrode active material for the residual alkaline component-containing nonaqueous electrolyte secondary battery, the conductive material and the binder is 1 to 5 kg / h, and the rotational speed of the rotary blade is 30 to 90 rpm. The method for producing a positive electrode slurry for a non-aqueous electrolyte secondary battery according to claim 10 or 11, wherein the peripheral speed of the rotating blade is 1.0 m / s or more. Step (2) is the next step (2-1) and (2-2)
Step (2-1): A step of obtaining a positive electrode slurry precursor for a nonaqueous electrolyte secondary battery by adding a predetermined amount of an organic solvent to the positive electrode mixture for the nonaqueous electrolyte secondary battery obtained in the step (1). ,
Step (2-2): a step of further adding an organic solvent to the non-aqueous electrolyte secondary battery positive electrode slurry precursor obtained in the step (2-1) to obtain a non-aqueous electrolyte secondary battery positive electrode slurry, The manufacturing method of the positive electrode slurry for nonaqueous electrolyte secondary batteries of any one of Claims 1-12 characterized by the above-mentioned.

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