JP2018032494A - Biaxial kneader for positive electrode mixture paste production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxial kneader for positive electrode mixture paste production, which can reduce the variation in the viscosity of a positive electrode mixture paste.SOLUTION: In a biaxial kneader 10 for positive electrode mixture paste production, when a plurality of resistance paddle parts 61b-64b, 61c-64c are classified into two groups, i.e. a group of feeding port-side resistance paddle parts 65b, 65c located on a side of a feeding port 31, and a group of exhaust port-side resistance paddle parts 66b, 66c located on a side of an exhaust port 32 by axis 35, 36, the feeding port-side resistance paddle parts 65b, 65c are larger than the exhaust port-side resistance paddle parts 66b, 66c in the clearance B1-B4 between an inner circumferential face 30b of a barrel 30, and each of outer circumferential faces 51f-54f of resistance paddles 51-54.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a biaxial kneader for producing a positive electrode mixture paste.

  Patent Document 1 discloses a biaxial kneader for producing a positive electrode mixture paste, in which a positive electrode active material that is a positive electrode material, acetylene black, a binder, and a solvent are kneaded to produce a positive electrode mixture paste. This biaxial kneader for producing a positive electrode mixture paste includes two shafts arranged in parallel, a cylindrical barrel extending in the axial direction in which the shaft extends, and a shear paddle arranged inside the barrel. A shear paddle portion that rotates around the shaft as a rotation axis, and a resistance paddle portion that rotates around the shaft as a rotation axis together with the shear paddle portion. ing.

JP-A-2015-109175

  The barrel is located on one end side in the axial direction, and is located on the other end side in the axial direction, and an inlet for feeding the positive electrode material into the barrel, and the positive electrode material is kneaded. And a discharge port for discharging the positive electrode mixture paste to the outside of the barrel. In each of the shafts, a plurality of resistance paddle portions are arranged side by side in the axial direction from the input port side toward the discharge port side. Moreover, the shear paddle part is arrange | positioned adjacent to the said axial direction with respect to each said resistance paddle part in each said axis | shaft. In this biaxial kneader for producing a positive electrode composite paste, all the resistance paddles have the same dimensions, and the inner peripheral surface of the barrel and the outer peripheral surface of the resistive paddle over the entire biaxial kneader for producing the positive electrode mixture paste. The clearance between is fixed.

  By the way, in the positive electrode active material contained in the positive electrode material in the same lot, the physical property may vary. Specifically, the positive electrode active material included in the positive electrode material in the same lot may vary in the solvent adsorptivity (solvent adsorption amount) for adsorbing the solvent on the surface of the positive electrode active material. In a positive electrode material that includes a large amount of a positive electrode active material having a high solvent adsorptivity (a large amount of solvent adsorption), a large amount of solvent is adsorbed to the positive electrode active material, thereby reducing the amount of solvent in a free state. On the other hand, in a positive electrode material containing a large amount of a positive electrode active material with low solvent adsorptivity (small amount of solvent adsorption), the amount of solvent adsorbed on the positive electrode active material is small, so that the amount of solvent in the free state increases.

  For this reason, when the positive electrode material is kneaded by the above-described biaxial kneader for producing the positive electrode mixture paste, the solvent adsorbability is high (solvent adsorption amount) in the initial stage of kneading (the stage passing through the inlet side resistance paddle part). The viscosity of the mixture of the positive electrode material containing a large amount of the positive electrode active material and the mixture of the positive electrode material containing a large amount of the positive electrode active material having a low solvent adsorbability (low solvent adsorption amount) are different. Specifically, in the initial stage of kneading, a mixture of positive electrode materials having a high solvent adsorbing property (high solvent adsorbing amount) and containing a large amount of positive electrode active material has a low solvent adsorbing property (low solvent adsorbing amount). Compared to a mixture of positive electrode materials containing a lot of substances, the viscosity is high, so it is difficult to pass through the clearance (clearance) between the resistance paddle part on the inlet side and the barrel, and the moving speed toward the outlet side is slow. Become.

  For this reason, in the initial stage of kneading, a mixture of positive electrode materials containing a large amount of positive electrode active material having a high solvent adsorptivity (a large amount of solvent adsorption) has a low positive solvent active material (a small amount of solvent adsorption). Compared with a mixture of many positive electrode materials, the time (shear time) for receiving a shearing force by the shear paddle part (input side shear paddle part) becomes longer. As a result, in a mixture of positive electrode materials having a high amount of positive electrode active material having a high solvent adsorptivity (a large amount of solvent adsorption), a positive electrode material having a high amount of a positive electrode active material having a low solvent adsorbability (a low amount of solvent adsorption). Compared with the mixture, the shearing force applied by the inlet side shear paddle portion was increased, and the acetylene black having a shape in which the primary particles were connected in a linear shape tended to be shorter (smaller in particle size).

  Accordingly, in the positive electrode mixture paste in the same lot produced by the above-described biaxial kneader for producing the positive electrode mixture paste, the length of the acetylene black (the length of the secondary particles in which the primary particles are linearly connected) In some cases, the variation became large. When the variation in the length of acetylene black increases, the variation in internal resistance (and thus the output) may increase between a plurality of batteries manufactured using these positive electrode mixture pastes (between batteries in the same lot). It was. The length of the acetylene black contained in the positive electrode mixture paste has a correlation with the viscosity of the positive electrode mixture paste. Therefore, the variation in the length of the acetylene black increases so that the variation in the viscosity of the positive electrode mixture paste increases. It was getting bigger.

  This invention is made | formed in view of this present condition, Comprising: It aims at providing the biaxial kneading machine for positive electrode compound paste manufacture which can make the dispersion | variation in the viscosity of positive electrode compound paste small.

  One aspect of the present invention includes two shafts arranged in parallel, a cylindrical barrel extending in an axial direction in which the shaft extends, and a shear paddle disposed inside the barrel, And a resistance paddle part that has a resistance paddle disposed inside the barrel, and that rotates together with the shear paddle part about the axis as a rotational axis, and is a positive electrode material. In a biaxial kneading machine for producing a positive electrode mixture paste by kneading a positive electrode active material, acetylene black, a binder and a solvent, the barrel is located on one end side in the axial direction, An inlet for introducing the positive electrode material into the barrel, and the positive electrode mixture paste, which is located on the other end side in the axial direction and is kneaded with the positive electrode material, is discharged to the outside of the barrel. And a plurality of the resistance paddle portions are arranged side by side in the axial direction from the input port side toward the discharge port side in each of the shafts, and the shear paddle portion However, each of the shafts is disposed adjacent to the resistance paddle portion in the axial direction with respect to each of the resistance paddle portions, and a plurality of the resistance paddle portions are positioned on the inlet side with respect to each of the shafts. When divided into two, the inlet side resistance paddle part and the outlet side resistance paddle part located on the outlet side, the clearance between the inner peripheral surface of the barrel and the outer peripheral surface of the resistive paddle is This is a biaxial kneader for producing a positive electrode mixture paste in which the inlet side resistance paddle part is larger than the outlet side resistance paddle part.

  In the above-described biaxial kneader for producing the positive electrode mixture paste (hereinafter also simply referred to as a biaxial kneader), the clearance (shortest distance) between the inner peripheral surface of the barrel and the outer peripheral surface of the resistance paddle is the discharge port. The inlet side resistance paddle part is made larger than the side resistance paddle part. That is, the clearance (gap) between the outer peripheral surface of the resistance paddle included in the inlet side resistance paddle part and the inner peripheral surface of the barrel is the same as the outer peripheral surface of the resistance paddle included in the outlet side resistance paddle part. It is made larger than any clearance (gap) between the inner peripheral surface of the barrel.

  As a result, even if there is a variation in the solvent adsorptivity (solvent adsorption amount) in the positive electrode active material contained in the positive electrode material put into the biaxial kneader, the initial stage of kneading (the inlet side resistance paddle part and the barrel) A mixture of a positive electrode material containing a large amount of a positive electrode active material having a high solvent adsorption property (a large amount of solvent adsorption) and a positive electrode active material having a low solvent adsorption property (a low amount of solvent adsorption). The difference in easiness of passing through the gap between the inlet side resistance paddle part and the barrel is reduced with the mixture of the positive electrode material contained in large quantities.

  For this reason, in the initial stage of kneading, a mixture of a positive electrode material containing a large amount of a positive electrode active material having a high solvent adsorption property (a large amount of solvent adsorption) and a positive electrode active material having a low solvent adsorption property (a low solvent adsorption amount). A difference in time (shear time) during which shear force is received by the shear paddle part (input-side shear paddle part) can be reduced with a mixture of many positive electrode materials. As a result, the shear time (total shear) by all the shear paddle parts (input side shear paddle part and outlet side shear paddle) provided in the biaxial kneader for the mixture of positive electrode materials charged into the barrel Variation in time) can be reduced.

  In the second half of the kneading (the stage of passing through the gap between the outlet side resistance paddle part and the barrel), in the positive electrode material mixture (paste) containing a large amount of the positive electrode active material having a high solvent adsorptivity (a large amount of solvent adsorption). However, since the viscosity decreases due to the progress of kneading, the solvent adsorbability is low (the amount of solvent adsorption is small) and passes through the resistance side paddle part on the outlet side as compared with a mixture of positive electrode materials containing a large amount of positive electrode active material. The easiness to do is almost the same, and the shear time by the discharge side shear paddle is also almost the same.

  Therefore, in the positive electrode mixture paste produced by the above-described biaxial kneader for manufacturing the positive electrode mixture paste, the variation in the length of the acetylene black is reduced, and as a result, the variation in the viscosity of the positive electrode mixture paste is reduced. As described above, according to the above-described biaxial kneader for producing the positive electrode mixture paste, the variation in the viscosity of the positive electrode mixture paste can be reduced.

  In addition, when each row of the plurality of resistance paddle portions arranged in the axial direction (the direction in which the shaft of the biaxial kneader extends) is divided into two in the axial direction (divided into two equal parts), the resistance located on the inlet side The paddle part is referred to as the inlet side resistance paddle part, and the resistance paddle part located on the outlet side is referred to as the outlet side resistance paddle part.

  Further, the resistance paddle hinders the movement of the positive electrode material that moves (conveys) in the barrel of the twin-screw kneader from the inlet side toward the outlet side, thereby moving the positive electrode material in the barrel (conveying speed). ) Is a member that controls (limits, suppresses). On the other hand, the shear paddle is a member that kneads the positive electrode material while applying a shearing force to the positive electrode material that moves (conveys) in the barrel of the biaxial kneader from the inlet side toward the outlet side. .

In addition, the positive electrode materials (positive electrode active material, acetylene black, binder, solvent, etc.) to be introduced into the barrel (biaxial kneader) through the inlet are each independently (that is, a plurality of types of positive electrode materials are mixed in advance). You may make it throw in (without setting it as a mixture), and you may make it throw in the state of the mixture which mixed multiple types beforehand. In any embodiment, the positive electrode active material paste, acetylene black, binder and solvent are kneaded using a biaxial kneader to produce a positive electrode mixture paste. Examples of the latter include, for example, a mixture (paste) in which acetylene black, a binder, and a solvent are mixed in advance (hereinafter, this mixture is also referred to as an AB paste). A mode in which the mixture is introduced into the interior of the kneading machine is mentioned.
Further, the positive electrode material that is a raw material of the positive electrode mixture paste is not limited to the positive electrode active material, acetylene black, binder, and solvent, but may include other materials.

1 is a perspective view of a lithium ion secondary battery according to an embodiment. It is a perspective view of the positive electrode of the lithium ion secondary battery. It is a perspective view of the negative electrode of the lithium ion secondary battery. It is a side view of the biaxial kneader for positive electrode compound paste manufacture concerning embodiment. It is a fragmentary sectional view which shows the structure inside the biaxial kneader for the positive electrode compound paste manufacture. It is a figure which shows the resistance paddle arrange | positioned inside the barrel of the biaxial kneader for the positive electrode compound paste manufacture. It is a figure which shows the shear paddle arrange | positioned inside the barrel of the biaxial kneader for the positive electrode compound paste manufacture. It is a flowchart which shows the flow of the manufacturing method of a lithium ion secondary battery. It is a subroutine of the same flowchart. It is a subroutine of the flowchart shown in FIG.

Next, the lithium ion secondary battery 100 of this embodiment will be described.
As illustrated in FIG. 1, the lithium ion secondary battery 100 includes an electrode body 110 and a battery case 180 that accommodates the electrode body 110. The electrode body 110 includes a positive electrode 130, a negative electrode 120, and a separator 150. The separator 150 is made of an electrically insulating resin film (for example, polyethylene), and is interposed between the positive electrode 130 and the negative electrode 120 to separate them. The separator 150 is impregnated with a non-aqueous electrolyte 160 having lithium ions. The non-aqueous electrolyte 160 is a non-aqueous electrolyte obtained by adding LiPF ₆ as a solute in an organic solvent.

  The battery case 180 is made of aluminum and has a rectangular parallelepiped shape. The battery case 180 has a battery case main body 181 and a sealing lid 182. Among these, the battery case main body 181 has a bottomed rectangular box shape. Note that an insulating film (not shown) made of resin and bent in a box shape is interposed between the battery case main body 181 and the electrode body 110.

  The sealing lid 182 has a rectangular plate shape, closes the opening of the battery case body 181, and is welded to the battery case body 181. The sealing lid 182 is provided with a rectangular plate-shaped safety valve 197.

  The electrode body 110 is a flat wound electrode body in which a belt-like positive electrode 130 and a belt-like negative electrode 120 are wound into a flat shape with a belt-like separator 150 interposed therebetween (see FIG. 1). . Specifically, the strip-like positive electrode 130, the negative electrode 120, and the separator 150 extending in the longitudinal direction DB are wound in the longitudinal direction DB to form a flat wound electrode body 110 (see FIGS. 1 to 3). ).

As shown in FIG. 2, the positive electrode 130 includes a positive electrode current collector foil 138 made of an aluminum foil in a strip shape extending in the longitudinal direction DB, and two positive electrode mixture layers disposed on the surface (both sides) of the positive electrode current collector foil 138. 131, 131. The two positive electrode mixture layers 131 and 131 each have a strip shape extending in the longitudinal direction DB. The positive electrode mixture layer 131 includes a positive electrode active material 137, acetylene black 133 (conductive material), and a binder 134 made of PVDF. In the present embodiment, a lithium transition metal composite oxide (specifically, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) is used as the positive electrode active material 137. In addition, the acetylene black 133 has a shape in which primary particles are linearly connected.

  Further, as shown in FIG. 3, the negative electrode 120 includes a negative electrode current collector foil 128 made of a copper foil in a strip shape extending in the longitudinal direction DB, and two negative electrode composites disposed on the surface (both sides) of the negative electrode current collector foil 128. Material layers 121 and 121. The two negative electrode mixture layers 121 and 121 each have a strip shape extending in the longitudinal direction DB. The negative electrode mixture layer 121 includes a negative electrode active material 127 and a binder. In the present embodiment, graphite is used as the negative electrode active material 127.

  Further, a plate-like positive electrode current collecting member 191 bent in a crank shape is welded to the positive electrode 130 of the electrode body 110 (see FIG. 1). Further, the negative electrode 120 is welded with a plate-shaped negative electrode current collecting member 192 bent in a crank shape. Of the positive electrode current collecting member 191 and the negative electrode current collecting member 192, the positive electrode terminal portion 191A and the negative electrode terminal portion 192A located at the respective tips penetrate the sealing lid 182 and protrude from the lid surface 182A. Insulating members 195 made of electrically insulating resin are interposed between the positive electrode terminal portion 191A and the sealing lid 182 and between the negative electrode terminal portion 192A and the sealing lid 182, respectively.

  Next, the biaxial kneader 10 for producing a positive electrode mixture paste according to the present embodiment (hereinafter also simply referred to as the biaxial kneader 10) will be described. FIG. 4 is a side view of the biaxial kneader 10 for producing the positive electrode mixture paste 131A. FIG. 5 is a diagram showing an internal configuration of the biaxial kneader 10, and is a partial cross-sectional view of the biaxial kneader 10 cut in the axial direction DA. FIG. 6 is a view showing resistance paddles 51 (52, 53, 54) arranged inside the barrel 30 of the twin-screw kneader 10, and FF (GG, HH, I) in FIG. This corresponds to a cross-sectional view of the twin-screw kneader 10 at the position indicated by -I). FIG. 7 is a diagram showing the shear paddles 11 (12, 13, 14) arranged inside the barrel 30 of the twin-screw kneader 10, and are shown by BB (CC, DD, E) in FIG. This corresponds to a cross-sectional view of the twin-screw kneader 10 at the position indicated by -E).

  The biaxial kneader 10 of the present embodiment is a continuous biaxial kneader for producing a positive electrode mixture paste 131A by kneading a positive electrode active material 137 that is a positive electrode material, acetylene black 133, a binder 134, and a solvent 135. . The biaxial kneader 10 includes two shafts 35 and 36 (see FIGS. 5 to 7) arranged in parallel to each other, and an axial direction DA (a direction in which the shafts 35 and 36 extend, right and left in FIGS. 4 and 5). Direction), a cylindrical shaft 35 having a central axis AX1, a cylindrical shaft 36 having a central axis AX2, first shear paddle portions 21b and 21c, and a second shear paddle portion. 22b, 22c, third shear paddle portions 23b, 23c, fourth shear paddle portions 24b, 24c, screws 41b, 41c, 42b, 42c, first resistance paddle portions 61b, 61c, and second resistance paddle portions. 62b, 62c, third resistor paddle portions 63b, 63c, and fourth resistor paddle portions 64b, 64c.

  Shafts 35, 36, first shear paddle portions 21b, 21c, second shear paddle portions 22b, 22c, third shear paddle portions 23b, 23c, fourth shear paddle portions 24b, 24c, and screws 41b, 41c , 42b, 42c, the first resistance paddle portions 61b, 61c, the second resistance paddle portions 62b, 62c, the third resistance paddle portions 63b, 63c, and the fourth resistance paddle portions 64b, 64c are in the axial direction DA. It is arranged inside the barrel 30 extending in the direction in which the shafts 35 and 36 extend (the left-right direction in FIGS. 4 and 5).

  In the barrel 30, a positive electrode material (positive electrode active material 137, acetylene black 133, binder 134, and solvent 135) is charged into the barrel 30 at one end side in the axial direction DA (left end side in FIGS. 4 and 5). Input port 31. Furthermore, the barrel 30 has a discharge port 32 for discharging the positive electrode mixture paste 131A formed by kneading the positive electrode material to the outside of the barrel 30 on the other end side in the axial direction DA (right end side in FIGS. 4 and 5). Have

  6 and 7, the inner peripheral surface 30b of the barrel 30 has a cylindrical inner peripheral surface 30b1 having a radius R1 centered on the central axis AX1 and a cylinder having a radius R1 centered on the central axis AX2. A shape in which the inner peripheral surface 30b2 having a shape is connected so that a part of the circumferential direction overlaps (intersects) (a shape in which the inner peripheral surface 30b1 having a C-shaped cross section and an inner peripheral surface 30b2 having a C-shaped reverse direction are connected ).

  The shafts 35 and 36 are arranged in parallel in the barrel 30. Among these, the axis | shaft 35 rotates centering on the center axis line AX1. On the other hand, the shaft 36 rotates about the center axis AX2 as a rotation center. 5 to 7, the rotation directions of the shafts 35 and 36 are the same.

  The first resistor paddle portion 61b, the second resistor paddle portion 62b, the third resistor paddle portion 63b, and the fourth resistor paddle portion 64b are fixed to the shaft 35, and rotate (rotate) together with the shaft 35 using the shaft 35 as a rotation axis. Move). The first resistance paddle portion 61b, the second resistance paddle portion 62b, the third resistance paddle portion 63b, and the fourth resistance paddle portion 64b are arranged in this order in the axial direction DA from the input port 31 side to the discharge port 32 side. Are arranged side by side at intervals (see FIG. 5).

  Here, the four resistance paddle portions on the shaft 35 are halved into two, that is, an inlet side resistance paddle portion 65b located on the inlet 31 side and an outlet side resistance paddle portion 66b located on the outlet 32 side. Divide each one. Then, among the first resistor paddle part 61b, the second resistor paddle part 62b, the third resistor paddle part 63b, and the fourth resistor paddle part 64b, the first resistor paddle part 61b and the second resistor paddle part 62b are connected to the insertion port 31. It becomes the insertion side resistance paddle part 65b located in the side. On the other hand, the 3rd resistance paddle part 63b and the 4th resistance paddle part 64b become the discharge side resistance paddle part 66b located in the discharge port 32 side (refer FIG. 5).

  The first resistance paddle portion 61c, the second resistance paddle portion 62c, the third resistance paddle portion 63c, and the fourth resistance paddle portion 64c are fixed to the shaft 36, and rotate together with the shaft 36 with the shaft 36 as a rotation axis ( Rotate). The first resistance paddle portion 61c, the second resistance paddle portion 62c, the third resistance paddle portion 63c, and the fourth resistance paddle portion 64c are arranged in this order in the axial direction DA from the input port 31 side to the discharge port 32 side. Are arranged side by side at intervals (see FIG. 5).

  Here, the four resistance paddle portions on the shaft 36 are halved into two, that is, an inlet side resistance paddle portion 65c located on the inlet 31 side and an outlet side resistance paddle portion 66c located on the outlet 32 side. Divide each one. Then, among the first resistor paddle part 61c, the second resistor paddle part 62c, the third resistor paddle part 63c, and the fourth resistor paddle part 64c, the first resistor paddle part 61c and the second resistor paddle part 62c are connected to the insertion port 31. It becomes the insertion port side resistance paddle part 65c located in the side. On the other hand, the 3rd resistance paddle part 63c and the 4th resistance paddle part 64c become the discharge side resistance paddle part 66c located in the discharge port 32 side (refer FIG. 5).

  The first resistance paddle portion 61b (or 61c) has a resistance paddle 51 fixed to the shaft 35 (or 36) (see FIG. 5). The resistance paddle 51 has a form in which two disk-shaped portions having different diameters overlap each other in the axial direction DA. Specifically, the resistance paddle 51 includes a large-diameter portion 51c having a large diameter (outer diameter) and a small-diameter portion 51d having a smaller diameter (outer diameter) than the large-diameter portion 51c. The small diameter part 51d is integrally formed. A through hole 51b is formed at the center of the resistance paddle 51 (see FIG. 6). The resistance paddle 51 is fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through hole 51b. In addition, the diameter (outer diameter) of the large diameter part 51c is R51.

  However, the resistance paddle 51 of the first resistance paddle portion 61b is fixed to the shaft 35 in such a direction that the large-diameter portion 51c is located on one end side (input port 31 side) in the axial direction DA. The resistance paddle 51 of the paddle portion 61c is fixed to the shaft 36 in such a direction that the large diameter portion 51c is located on the other end side (the discharge port 32 side) in the axial direction DA. Therefore, the large-diameter portion 51c of the resistor paddle 51 forming the first resistor paddle portion 61b and the small-diameter portion 51d of the resistor paddle 51 forming the first resistor paddle portion 61c are orthogonal to the central axes AX1 and AX2 (FIG. 5). The small-diameter portion 51d of the resistance paddle 51 and the large-diameter portion 51c of the resistance paddle 51 forming the first resistance paddle portion 61c are located adjacent to each other in the vertical direction in FIG. It is located adjacent to the direction orthogonal to AX2 (vertical direction in FIG. 5).

  As shown in FIG. 6, the clearance B1 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 51f of the resistance paddle 51 is such that both the first resistance paddle portions 61b and 61c are from R1. The value obtained by subtracting R51 (B1 = R1-R51).

  The second resistance paddle portion 62b (or 62c) has a resistance paddle 52 fixed to the shaft 35 (or 36) (see FIG. 5). The resistance paddle 52 also has a form in which two disk-shaped portions having different diameters overlap each other in the axial direction DA. Specifically, the resistance paddle 52 includes a large diameter portion 52c having a large diameter (outer diameter) and a small diameter portion 52d having a diameter (outer diameter) smaller than the large diameter portion 52c. The small diameter portion 52d is integrally formed. A through hole 52b is formed at the center of the resistance paddle 52 (see FIG. 6). The resistance paddle 52 is fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through hole 52b. The diameter (outer diameter) of the large diameter portion 52c is R52.

  However, the resistance paddle 52 of the second resistance paddle portion 62b is fixed to the shaft 35 in such a direction that the large diameter portion 52c is located on one end side (input port 31 side) in the axial direction DA. The resistance paddle 52 of the paddle portion 62c is fixed to the shaft 36 in such a direction that the large diameter portion 52c is located on the other end side (the discharge port 32 side) in the axial direction DA. Therefore, the large diameter portion 52c of the resistance paddle 52 forming the second resistance paddle portion 62b and the small diameter portion 52d of the resistance paddle 52 forming the second resistance paddle portion 62c are orthogonal to the central axes AX1 and AX2 (FIG. 5). The small-diameter portion 52d of the resistor paddle 52 and the large-diameter portion 52c of the resistor paddle 52 forming the second resistor paddle portion 62c are positioned adjacent to each other in the vertical direction in FIG. It is located adjacent to the direction orthogonal to AX2 (vertical direction in FIG. 5).

  As shown in FIG. 6, the clearance B2 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 52f of the resistance paddle 52 is such that both the second resistance paddle portions 62b and 62c are from R1. A value obtained by subtracting R52 (B2 = R1-R52).

  The third resistance paddle portion 63b (or 63c) has a resistance paddle 53 fixed to the shaft 35 (or 36) (see FIG. 5). The resistance paddle 53 also has a form in which two disk-shaped portions having different diameters overlap each other in the axial direction DA. Specifically, the resistance paddle 53 includes a large-diameter portion 53c having a large diameter (outer diameter) and a small-diameter portion 53d having a smaller diameter (outer diameter) than the large-diameter portion 53c. The small-diameter portion 53d is integrally formed. A through hole 53b is formed at the center of the resistance paddle 53 (see FIG. 6). The resistance paddle 53 is fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through hole 53b. The diameter (outer diameter) of the large diameter portion 53c is R53.

  However, the resistance paddle 53 of the third resistance paddle portion 63b is fixed to the shaft 35 in such a direction that the large diameter portion 53c is located on one end side (the inlet 31 side) in the axial direction DA, while the third resistance paddle portion 63b The resistance paddle 53 of the paddle portion 63c is fixed to the shaft 36 in such a direction that the large diameter portion 53c is located on the other end side (the discharge port 32 side) in the axial direction DA. Therefore, the large-diameter portion 53c of the resistor paddle 53 forming the third resistor paddle portion 63b and the small-diameter portion 53d of the resistor paddle 53 forming the third resistor paddle portion 63c are orthogonal to the central axes AX1 and AX2 (FIG. 5). The small diameter portion 53d of the resistance paddle 53 forming the third resistance paddle portion 63b and the large diameter portion 53c of the resistance paddle 53 forming the third resistance paddle portion 63c are located adjacent to each other in the vertical direction in FIG. It is located adjacent to the direction orthogonal to AX2 (vertical direction in FIG. 5).

  As shown in FIG. 6, the clearance B3 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 53f of the resistance paddle 53 is such that both the third resistance paddle portions 63b and 63c are from R1. A value obtained by subtracting R53 (B3 = R1-R53).

  The fourth resistance paddle portion 64b (or 64c) has a resistance paddle 54 fixed to the shaft 35 (or 36) (see FIG. 5). The resistance paddle 54 also has a configuration in which two disk-shaped portions having different diameters overlap each other in the axial direction DA. Specifically, the resistance paddle 54 includes a large diameter portion 54c having a large diameter (outer diameter) and a small diameter portion 54d having a smaller diameter (outer diameter) than the large diameter portion 54c. The small diameter portion 54d is integrally formed. A through hole 54b is formed at the center of the resistance paddle 54 (see FIG. 6). The resistance paddle 54 is fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through hole 54b. The diameter (outer diameter) of the large diameter portion 54c is R54.

  However, the resistance paddle 54 of the fourth resistance paddle portion 64b is fixed to the shaft 35 in such a direction that the large diameter portion 54c is located on one end side (the inlet 31 side) in the axial direction DA, The resistance paddle 54 of the paddle portion 64c is fixed to the shaft 36 in such a direction that the large diameter portion 54c is located on the other end side (discharge port 32 side) in the axial direction DA. Therefore, the large-diameter portion 54c of the resistor paddle 54 forming the fourth resistor paddle portion 64b and the small-diameter portion 54d of the resistor paddle 54 forming the fourth resistor paddle portion 64c are orthogonal to the central axes AX1 and AX2 (FIG. 5). The small diameter portion 54d of the resistance paddle 54 and the large diameter portion 54c of the resistance paddle 54 forming the fourth resistance paddle portion 64c are positioned adjacent to each other in the vertical direction in FIG. It is located adjacent to the direction orthogonal to AX2 (vertical direction in FIG. 5).

As shown in FIG. 6, the clearance B4 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 54f of the resistance paddle 54 is such that both the fourth resistance paddle portions 64b and 64c are from R1. A value obtained by subtracting R54 (B4 = R1-R54).
The resistance paddles 51 to 54 described above move (convey) in the barrel 30 of the biaxial kneader 10 from the inlet 31 side toward the outlet 32 side (from left to right in FIG. 5). The movement of the positive electrode material (the mixture of the positive electrode active material 137, acetylene black 133, the binder 134, and the solvent 135) is prevented, and the moving speed (conveying speed) of the positive electrode material in the barrel 30 is controlled (restricted or suppressed).

  In the present embodiment, the clearances B1, B2, B3, B4 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surfaces 51f, 52f, 53f, 54f of the resistance paddles 51, 52, 53, 54 are as follows. Are larger at the inlet side resistance paddle portions 65b and 65c than at the outlet side resistance paddle portions 66b and 66c. That is, the clearances B1 and B2 (shortest distance) between the outer peripheral surfaces 51f and 52f of the resistance paddles 51 and 52 and the inner peripheral surface 30b of the barrel 30 included in the insertion-side resistance paddle portions 65b and 65c are both It is made larger than any of clearances B3 and B4 (shortest distance) between the outer peripheral surfaces 53f and 54f of the resistance paddles 53 and 54 and the inner peripheral surface 30b of the barrel 30 included in the discharge-side resistance paddle portions 66b and 66c. Yes.

The first shear paddle part 21b, the second shear paddle part 22b, the third shear paddle part 23b, and the fourth shear paddle part 24b are fixed to the shaft 35, and rotate together with the shaft 35 with the shaft 35 as a rotation axis ( Rotate). The first shear paddle part 21b, the second shear paddle part 22b, the third shear paddle part 23b, and the fourth shear paddle part 24b are arranged in this order in the axial direction DA from the inlet 31 side toward the outlet 32 side. Are arranged side by side at intervals.
More specifically, the first shear paddle portion 21b is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the first resistance paddle portion 61b. Further, the second shear paddle portion 22b is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the second resistance paddle portion 62b. The third shear paddle portion 23b is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the third resistance paddle portion 63b. The fourth shear paddle portion 24b is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the fourth resistance paddle portion 64b.

  Here, the four shear paddle portions applied to the shaft 35 are halved into two, that is, the inlet side shear paddle portion 25b located on the inlet 31 side and the outlet side shear paddle portion 26b located on the outlet 32 side. Divide each one. Then, among the first shear paddle part 21b, the second shear paddle part 22b, the third shear paddle part 23b, and the fourth shear paddle part 24b, the first shear paddle part 21b and the second shear paddle part 22b are connected to the input port 31. It becomes the inlet side shear paddle part 25b located in the side. On the other hand, the 3rd shear paddle part 23b and the 4th shear paddle part 24b become the discharge port side shear paddle part 26b located in the discharge port 32 side.

The first shear paddle portion 21c, the second shear paddle portion 22c, the third shear paddle portion 23c, and the fourth shear paddle portion 24c are fixed to the shaft 36, and rotate together with the shaft 36 using the shaft 36 as a rotation axis ( Rotate). The first shear paddle portion 21c, the second shear paddle portion 22c, the third shear paddle portion 23c, and the fourth shear paddle portion 24c are arranged in this order in the axial direction DA from the input port 31 side to the discharge port 32 side. Are arranged side by side at intervals.
More specifically, the first shear paddle portion 21c is adjacent to one end side in the axial direction DA (left side in FIG. 5) with respect to the first resistance paddle portion 61c. The second shear paddle portion 22c is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the second resistance paddle portion 62c. The third shear paddle portion 23c is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the third resistance paddle portion 63c. The fourth shear paddle portion 24c is adjacent to one end side (left side in FIG. 5) in the axial direction DA with respect to the fourth resistance paddle portion 64c.

  The four shear paddle portions on the shaft 36 are divided into two halves, one on each of the inlet side shear paddle portion 25c located on the inlet port 31 side and on the outlet port side shear paddle portion 26c located on the outlet port 32 side. Divide. Then, among the first shear paddle part 21c, the second shear paddle part 22c, the third shear paddle part 23c, and the fourth shear paddle part 24c, the first shear paddle part 21c and the second shear paddle part 22c are connected to the inlet 31. The inlet side shear paddle portion 25c is located on the side. On the other hand, the 3rd shear paddle part 23c and the 4th shear paddle part 24c become the discharge port side shear paddle part 26c located in the discharge port 32 side.

  The first shear paddle portion 21b (or 21c) has three shear paddles 11, 11, and 11 fixed to the shaft 35 (or 36) (see FIG. 5). The shear paddle 11 is a plate-like member having a substantially triangular outer shape in plan view, and a through hole 11b is formed at the center thereof (see FIG. 7). The three shear paddles 11, 11, and 11 are fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the respective through holes 11b.

  Accordingly, the three shear paddles 11, 11, and 11 constituting the first shear paddle portion 21b (or 21c) rotate (rotate) together with the shaft 35 (or 36) about the shaft 35 (or 36). . As a result, in the first shear paddle portion 21b (or 21c), the positive electrode material (the positive electrode active material 137, the acetylene black 133, the binder 134, and the solvent 135) can be sheared to knead the positive electrode material.

  The three shear paddles 11, 11, 11 constituting the first shear paddle portion 21b (or 36) are arranged side by side in the axial direction DA in such a manner that the adjacent shear paddles 11 are in contact with each other in the axial direction DA. (See FIG. 5). In this embodiment, three shear paddles 12, 12, and 12 constituting a second shear paddle portion 22b (or 22c), which will be described later, and three shear paddles 13, 13, constituting a third shear paddle portion 23b (or 23c), are described. 13 and the three shear paddles 14, 14, and 14 constituting the fourth shear paddle portion 24b (or 24c) are the same.

  Of the three shear paddles 11, 11, 11 constituting the first shear paddle portion 21b (or 21c), the shear paddle 11 located in the center in the axial direction DA (the shear paddle 11 not hatched in FIG. 7) Is fixed to the shaft 35 (or 36) in a direction shifted by 180 degrees (half circumference) around the shaft 35 (or 36) with respect to the shear paddles 11 and 11 located on both sides in the axial direction DA (see FIG. 7). ). In this embodiment, three shear paddles 12, 12, and 12 constituting a second shear paddle portion 22b (or 22c), which will be described later, and three shear paddles 13, 13, constituting a third shear paddle portion 23b (or 23c), are described. 13 and the three shear paddles 14, 14, and 14 constituting the fourth shear paddle portion 24b (or 24c) are the same.

  As shown in FIG. 7, the three corners 11c, 11d, and 11e of the shear paddle 11 are all arcs having a radius R11 with the central axis AX1 (or AX2) as the center. The maximum diameter of the shear paddle 11 is the radius R11 of the three corner portions 11c, 11d, and 11e. Therefore, the clearance C1 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 11f of the shear paddle 11 is a value obtained by subtracting R11 from R1 (C1 = R1-R11).

  The second shear paddle portion 22b (or 22c) has three shear paddles 12, 12, and 12 fixed to the shaft 35 (or 36) (see FIG. 5). The shear paddle 12 is a plate-like member having a substantially triangular outer shape in plan view, and a through hole 12b is formed at the center thereof (see FIG. 7). The three shear paddles 12, 12, and 12 are fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the respective through holes 12b.

  Accordingly, the three shear paddles 12, 12, and 12 constituting the second shear paddle portion 22b (22c) rotate (rotate) together with the shaft 35 (or 36) about the shaft 35 (or 36). Thereby, also in the 2nd shear paddle part 22b (or 22c), a shear force is applied with respect to positive electrode material (The positive electrode active material 137, acetylene black 133, the binder 134, and the solvent 135), and a positive electrode material can be knead | mixed. .

  As shown in FIG. 7, the three corners 12c, 12d, and 12e of the shear paddle 12 are all arcs having a radius R12 with the center axis AX1 (or AX2) as the center. The maximum diameter of the shear paddle 12 is the radius R12 of the three corners 12c, 12d, 12e. Therefore, the clearance C2 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 12f of the shear paddle 12 is a value obtained by subtracting R12 from R1 (C2 = R1-R12).

  The third shear paddle portion 23b (or 23c) has three shear paddles 13, 13, and 13 fixed to the shaft 35 (or 36) (see FIG. 5). The shear paddle 13 is a plate-like member having a substantially triangular outer shape in plan view, and a through hole 13b is formed at the center thereof (see FIG. 7). The three shear paddles 13, 13, and 13 are fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through holes 13b.

  Accordingly, the three shear paddles 13, 13, and 13 constituting the third shear paddle portion 23b (23c) rotate (rotate) together with the shaft 35 (or 36) about the shaft 35 (or 36). Thereby, also in the 3rd shear paddle part 23b (or 23c), a shear force can be added with respect to positive electrode material (The positive electrode active material 137, acetylene black 133, the binder 134, and the solvent 135), and a positive electrode material can be knead | mixed. .

  As shown in FIG. 7, the three corners 13c, 13d, and 13e of the shear paddle 13 all form an arc having a radius R13 with the center axis AX1 (or AX2) as the center. The maximum diameter of the shear paddle 13 is the radius R13 of the three corners 13c, 13d, 13e. Therefore, the clearance C3 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 13f of the shear paddle 13 is a value obtained by subtracting R13 from R1 (C3 = R1-R13).

  The fourth shear paddle portion 24b (or 24c) has three shear paddles 14, 14, and 14 fixed to the shaft 35 (or 36) (see FIG. 5). The shear paddle 14 is a plate-like member having a substantially triangular outer shape in plan view, and a through hole 14b is formed at the center thereof (see FIG. 7). The three shear paddles 14, 14, and 14 are fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the respective through holes 14b.

  Accordingly, the three shear paddles 14, 14, and 14 constituting the fourth shear paddle portion 24b (24c) rotate (rotate) together with the shaft 35 (or 36) about the shaft 35 (or 36). Thereby, also in the 4th shear paddle part 24b (or 24c), a shear force is applied with respect to positive electrode material (The positive electrode active material 137, acetylene black 133, the binder 134, and the solvent 135), and a positive electrode material can be knead | mixed. .

  As shown in FIG. 7, all of the three corners 14c, 14d, 14e of the shear paddle 14 form an arc having a radius R14 with the center axis AX1 (or AX2) as the center. The maximum diameter of the shear paddle 14 is the radius R14 of the three corners 14c, 14d, 14e. Therefore, the clearance C4 (shortest distance) between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surface 14f of the shear paddle 14 is a value obtained by subtracting R14 from R1 (C4 = R1-R14).

  The screws 41b and 42b (or 41c and 42c) are cylindrical members having a spiral outer peripheral surface (see FIG. 5), and a through hole is formed at the center thereof. The screws 41b and 42b (or 41c and 42c) are fixed to the shaft 35 (or 36) by inserting the shaft 35 (or 36) into the through hole.

  Accordingly, the screws 41b and 42b (or 41c and 42c) rotate (rotate) together with the shaft 35 (or 36) with the shaft 35 (or 36) as a rotation axis. As a result, the positive electrode material (the positive electrode active material 137, the acetylene black 133, the binder 134, and the solvent 135) is transferred by the screws 41b and 42b (or 41c and 42c) to the first axial direction DA1 (of the axial direction DA). It is transported in the direction from the inlet 31 to the outlet 32 (from left to right in FIG. 5).

  Next, a manufacturing method of the lithium ion secondary battery 100, a manufacturing method of the positive electrode 130, and a manufacturing method of the positive electrode mixture paste 131A will be described. FIG. 8 is a flowchart showing a flow of a method for manufacturing a lithium ion secondary battery. FIG. 9 is a flowchart of the flowchart of FIG. 8 and shows the flow of the positive electrode manufacturing method. FIG. 10 is a flowchart of the subroutine of the flowchart of FIG. 9 and shows the flow of the manufacturing method of the positive electrode mixture paste.

  As shown in FIG. 8, first, in step S1, the positive electrode 130 is manufactured. Specifically, as shown in FIG. 9, first, in step S11 (positive electrode mixture paste preparation step), a positive electrode mixture paste 131A is prepared. Here, the manufacturing method of the positive electrode mixture paste 131A will be specifically described.

In the present embodiment, using the above-described biaxial kneader 10 (see FIGS. 4 to 7), the positive electrode active material 137, which is a positive electrode material, acetylene black 133 (conductive material), and a binder 134 (in this embodiment, PVDF ) And the solvent 135 are kneaded to produce the positive electrode mixture paste 131A.
Specifically, as shown in FIG. 10, first, in step S <b> 111, positive electrode materials (positive electrode active material 137, acetylene black 133, binder 134, and solvent 135) are charged into the biaxial kneader 10. Specifically, the positive electrode material is charged into the biaxial kneader 10 through the charging port 31 provided in the barrel 30. In this embodiment, acetylene black 133, binder 134, and solvent 135 are mixed in advance to form a mixture (this mixture is referred to as AB paste 132), and this AB paste 132 and positive electrode active material 137 are added to the inlet 31. Through the barrel 30 (biaxial kneader 10).

  In the present embodiment, the positive electrode active material 137, the acetylene black 133, the binder 134, and the solvent 135 are adjusted so that the solid content of the positive electrode mixture paste 131A is greater than 54% (for example, 63.5%). The amount added is adjusted. The solid content of the positive electrode mixture paste 131A is the content (wt%) of the positive electrode active material 137, acetylene black 133, and binder 134 in the positive electrode mixture paste 131A. Thus, by increasing the solid content ratio of the positive electrode mixture paste 131A, the positive electrode mixture paste can be dried in a short time in step S13 (drying step) described later.

  In step S112, the positive electrode material (positive electrode active material 137, acetylene black 133, binder 134, and solvent 135) charged into the biaxial kneader 10 through the inlet 31 is conveyed to the outlet 32 side. While kneading. Specifically, by rotating the shafts 35 and 36 in the same direction at the same rotational speed, the screws 41b and 42b, the first to fourth shear paddle parts 21b to 24b, and the first to fourth resistance paddle parts 61b to 61b. While rotating 64b with the axis | shaft 35, screw 41c, 42c, the 1st-4th shear paddle part 21c-24c, and the 1st-4th resistance paddle part 61c-64c are rotated with the axis | shaft 36.

  As a result, the positive electrode material introduced from the insertion port 31 is controlled by the first to fourth resistance paddle portions 61b to 64b while the conveyance speed is controlled (restricted or suppressed), and the first shaft by the screws 41b, 41c and 42b, 42c. While being conveyed in the direction DA1, the first shear paddle portions 21b and 21c, the second shear paddle portions 22b and 22c, the third shear paddle portions 23b and 23c, and the fourth shear paddle portions 24b and 24c are subjected to shearing force and kneaded. The Thereby, as the positive electrode material (the positive electrode active material 137, the acetylene black 133, the binder 134, and the solvent 135) proceeds from the inlet 31 side to the outlet 32 side, the dispersibility of solids such as the positive electrode active material 137 increases. At the same time, the viscosity of the mixture (paste) of the positive electrode material is decreased to become the positive electrode mixture paste 131A.

Next, the process proceeds to step S113, where the positive electrode mixture paste 131A obtained by kneading the positive electrode material (the positive electrode active material 137, acetylene black 133, the binder 134, and the solvent 135) as described above is supplied to the biaxial kneader through the discharge port 32. 10 is discharged to the outside.
As described above, the positive electrode mixture paste 131A is manufactured.

  By the way, the physical properties of the positive electrode active material 137 contained in the positive electrode material in the same lot may vary. Specifically, the positive electrode active material 137 included in the positive electrode material in the same lot may vary in the solvent adsorbability (solvent adsorption amount) for adsorbing the solvent 135 on the surface of the positive electrode active material 137. In the positive electrode material that includes a large amount of the positive electrode active material 137 that has a high solvent adsorptivity (a large amount of solvent adsorption), the amount of the solvent 135 in the free state decreases because a large amount of the solvent 135 is adsorbed to the positive electrode active material 137. . In particular, when the solid content ratio of the positive electrode mixture paste is larger than 54% (that is, when the amount of the solvent added is reduced), the amount of the solvent 135 in the free state is particularly small. On the other hand, in the positive electrode material containing a large amount of the positive electrode active material 137 having a low solvent adsorptivity (small amount of solvent adsorption), the amount of the solvent 135 adsorbed on the positive electrode active material 137 is small. Become more.

  For this reason, conventionally, when the positive electrode material is kneaded by the biaxial kneader for producing the positive electrode mixture paste, the solvent adsorbability is high (solvent adsorption amount) in the initial stage of kneading (stage passing through the inlet side resistance paddle part). The viscosity of the mixture of the positive electrode material containing a large amount of the positive electrode active material 137 and the mixture of the positive electrode material containing a large amount of the positive electrode active material 137 having a low solvent adsorbability (low solvent adsorption amount) are different. Become. Specifically, a mixture of positive electrode materials containing a large amount of positive electrode active material 137 having a high solvent adsorbability (a large amount of solvent adsorption) in the initial stage of kneading has a low solvent adsorbability (a low amount of solvent adsorption). ) Since the viscosity is higher than that of a mixture of positive electrode materials containing a large amount of the positive electrode active material 137, it becomes difficult to pass through the gap between the inlet side resistance paddle part and the barrel, and the moving speed toward the outlet side is high. Become slow.

  For this reason, conventionally, in the initial stage of kneading, the positive electrode material mixture containing a large amount of the positive electrode active material 137 having a high solvent adsorption property (a large amount of solvent adsorption) has a low solvent adsorption property (a small amount of solvent adsorption). Compared with a mixture of positive electrode materials containing a large amount of the active material 137, the time (shear time) for receiving a shearing force by the shear paddle part (the inlet-side shear paddle part) becomes longer. As a result, in a mixture of positive electrode materials containing a large amount of positive electrode active material 137 having a high solvent adsorption property (a large amount of solvent adsorption), a positive electrode containing a large amount of positive electrode active material 137 having a low solvent adsorption property (a low amount of solvent adsorption). Compared with the mixture of materials, the shearing force applied by the inlet side shear paddle portion was increased, and the acetylene black 133 in which the primary particles were connected in a linear shape tended to be shorter (smaller in particle size). In particular, when the solid content ratio of the positive electrode mixture paste is larger than 54% (that is, when the amount of the solvent added is reduced), the tendency becomes stronger.

  Therefore, conventionally, in the positive electrode mixture paste in the same lot produced by the biaxial kneader for producing the positive electrode mixture paste, the length variation of the acetylene black 133 may become large. When the variation in the length of acetylene black 133 increases, internal resistance (between lithium ion secondary batteries in the same lot) between a plurality of lithium ion secondary batteries manufactured using these positive electrode mixture pastes ( As a result, variation in output) sometimes increased. Since the length of the acetylene black 133 contained in the positive electrode mixture paste has a correlation with the viscosity of the positive electrode mixture paste, the variation in the length of the acetylene black 133 is increased, so that the viscosity of the positive electrode mixture paste is increased. The variation was large. In particular, when the solid content rate of the positive electrode mixture paste is larger than 54% as in this embodiment (that is, when the amount of the solvent added is reduced), the variation in the viscosity of the positive electrode mixture paste increases. There was a trend.

  On the other hand, in the biaxial kneader 10 of this embodiment, the clearances B1, B2 between the inner peripheral surface 30b of the barrel 30 and the outer peripheral surfaces 51f, 52f, 53f, 54f of the resistance paddles 51, 52, 53, 54 are as follows. , B3, B4 (shortest distance) are larger in the inlet side resistance paddle portions 65b, 65c than in the outlet side resistance paddle portions 66b, 66c. That is, the clearances B1 and B2 (shortest distance) between the outer peripheral surfaces 51f and 52f of the resistance paddles 51 and 52 and the inner peripheral surface 30b of the barrel 30 included in the insertion-side resistance paddle portions 65b and 65c are both It is made larger than any of clearances B3 and B4 (shortest distance) between the outer peripheral surfaces 53f and 54f of the shear paddles 53 and 54 included in the discharge-side resistance paddle portions 66b and 66c and the inner peripheral surface 30b of the barrel 30. Yes.

  Thus, by increasing the clearances B1 and B2 between the inlet side resistance paddle portions 65b and 65c and the barrel 30, the positive electrode active material 137 included in the positive electrode material charged into the biaxial kneader 10 is used. Even when there is variation in solvent adsorption (solvent adsorption amount), the positive electrode has high solvent adsorption (high solvent adsorption amount) in the initial stage of kneading (stage passing through the inlet side resistance paddle portions 65b and 65c). Between the mixture of the positive electrode material containing a large amount of the active material 137 and the mixture of the positive electrode material containing a large amount of the positive electrode active material 137 having a low solvent adsorptivity (low solvent adsorption amount), The difference in ease of passing through the gap between 65c and barrel 30 is reduced.

  For this reason, in the initial stage of kneading, the mixture of the positive electrode material containing a large amount of the positive electrode active material 137 having a high solvent adsorptivity (high amount of solvent adsorption) and the positive electrode active material having a low solvent adsorbability (low amount of solvent adsorption) A difference in time (shear time) during which shear force is received by the inlet-side shear paddle portions 25b and 25c can be reduced with the mixture of positive electrode materials containing a large amount of 137. Thereby, with respect to the mixture of the positive electrode material thrown in the barrel 30, all the shear paddle parts 21b-24b, 21c-24c (input side shear paddle parts 25b, 25c and 25c provided in the biaxial kneader 10 and Variation in shear time (total shear time) due to the discharge side shear paddles 26b and 26c) can be reduced.

  In the latter half of kneading (the stage of passing through the outlet side resistance paddle portions 66b and 66c), the positive electrode material mixture (paste) containing a large amount of the positive electrode active material 137 having a high solvent adsorptivity (a large amount of solvent adsorption) is also used. , Since the kneading progresses and the viscosity is reduced, the discharge side resistance paddle part 66b, compared with the mixture of the positive electrode material containing a large amount of the positive electrode active material 137 having a low solvent adsorptivity (low amount of solvent adsorption), The ease of passing through 66c is substantially the same, and the shear time by the discharge side shear paddles 26b and 26c is also substantially the same.

  Therefore, in the positive electrode mixture paste 131A produced by the biaxial kneader 10 of this embodiment, the variation in the length of the acetylene black 133 is reduced, and as a result, the variation in the viscosity of the positive electrode mixture paste 131A is reduced. As described above, according to the biaxial kneader 10 of the present embodiment, the variation in the viscosity of the positive electrode mixture paste 131A can be reduced.

Next, a method for manufacturing a lithium ion secondary battery and a method for manufacturing a positive electrode according to the present embodiment will be described.
Returning to the flowchart of FIG. 9, in step S12 (application process), the positive electrode mixture paste 131A manufactured in step S11 is applied to the surface (both surfaces) of the positive electrode current collector foil 138 made of aluminum foil.

  Next, the process proceeds to step S13 (drying step), and the positive electrode mixture paste 131A applied to the surface (both sides) of the positive electrode current collector foil 138 is dried. Then, it progresses to step S14 (press process), and the dried positive mix paste 131A is compression-molded with a roll press. Thereby, the positive electrode 130 (see FIG. 2) in which the positive electrode mixture layer 131 is laminated on the surface (both sides) of the positive electrode current collector foil 138 is completed.

  Thereafter, returning to the flowchart of FIG. 8, in step S2, the negative electrode 120 is fabricated. Specifically, the negative electrode active material 127, a binder, and a solvent are kneaded to prepare a negative electrode mixture paste. Thereafter, this negative electrode mixture paste was applied to the surface (both sides) of a negative electrode current collector foil 128 made of copper foil, dried, and then compression molded by a roll press. Thus, the negative electrode 120 (see FIG. 3) in which the negative electrode mixture layer 121 is laminated on the surface (both surfaces) of the negative electrode current collector foil 128 is completed.

  Next, in step S3, the electrode body 110 is manufactured. Specifically, the strip-shaped separator 150 is interposed between the strip-shaped positive electrode 130 and the strip-shaped negative electrode 120, and these are wound to produce the flat wound electrode body 110. Thereafter, the negative electrode current collector 192 is welded to the negative electrode 120 (negative electrode current collector foil 128), and the positive electrode current collector 191 is welded to the positive electrode 130 (positive electrode current collector foil 138). In addition, before performing this welding, the positive electrode current collection member 191 and the negative electrode current collection member 192 are assembled | attached to the sealing lid 182, and these are united.

Next, the process proceeds to step S <b> 4, and the electrode body 110 welded to the negative electrode current collecting member 192 and the positive electrode current collecting member 191 is accommodated in the battery case main body 181. At this time, the opening of the battery case body 181 is closed by the sealing lid 182. Thereafter, the sealing lid 182 and the battery case body 181 are welded to form a battery case 180.
Next, it progresses to step S5 and the nonaqueous electrolyte 160 is inject | poured in the battery case 180 through the injection hole which is not shown in figure. Then, the lithium ion secondary battery 100 is completed by performing a predetermined process (initial charge etc.).

Example 1
In Example 1, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 with clearances B1 = 2.5 mm, B2 = 2.0 mm, B3 = 1.0 mm, and B4 = 1.0 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured. In Example 1 and Examples 2 to 7 described later, the positive electrode material is introduced into the biaxial kneader 10 so that the solid content of the positive electrode mixture paste 131A is 63.5%. In Example 1 and Examples 2 to 6 described later, the clearances C1 = C2 = 4.0 mm, C3 = 1.5 mm, and C4 = 1.0 mm are set.

(Example 2)
In Example 2, the positive electrode mixture paste 131A, the positive electrode 130, and the lithium ion secondary battery 100 are manufactured in the same manner as in Example 1, except that only the clearance B2 of the biaxial kneader 10 is different. did. Specifically, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 with clearances B1 = 2.5 mm, B2 = 2.5 mm, B3 = 1.0 mm, and B4 = 1.0 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured.

(Example 3)
In Example 3, as compared with Example 1, only the clearance B3 of the biaxial kneader 10 is changed, and the others are similarly manufactured to produce the positive electrode mixture paste 131A, the positive electrode 130, and the lithium ion secondary battery 100. did. Specifically, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 with clearances B1 = 2.5 mm, B2 = 2.0 mm, B3 = 1.3 mm, and B4 = 1.0 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured.

Example 4
In Example 4, the positive electrode mixture paste 131A, the positive electrode 130, and the lithium ion secondary battery 100 are manufactured in the same manner as in Example 1, except that only the clearance B4 of the biaxial kneader 10 is different. did. Specifically, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 with clearances B1 = 2.5 mm, B2 = 2.0 mm, B3 = 1.0 mm, and B4 = 1.3 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured.

(Example 5)
In Example 5, compared with Example 1, the clearances B3 and B4 of the twin-screw kneader 10 are different, and the others are the same, and the positive electrode mixture paste 131A, the positive electrode 130, and the lithium ion secondary battery 100 are the same. Manufactured. Specifically, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 with clearances B1 = 2.5 mm, B2 = 2.0 mm, B3 = 1.3 mm, and B4 = 1.3 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured.

(Example 6)
In Example 6, as compared with Example 1, only the clearance B3 of the biaxial kneader 10 is changed, and the others are similarly manufactured to produce the positive electrode mixture paste 131A, the positive electrode 130, and the lithium ion secondary battery 100. did. Specifically, the positive electrode mixture paste 131A was manufactured by using the biaxial kneader 10 in which the clearances B1 = 2.5 mm, B2 = 2.0 mm, B3 = 1.5 mm, and B4 = 1.0 mm. Using this positive electrode mixture paste 131A, the positive electrode 130 and the lithium ion secondary battery 100 were manufactured.

(Comparative Example 1)
In Comparative Example 1, as compared with Example 1, only the clearance (shortest distance) between the inner peripheral surface of the barrel and the outer peripheral surface of the resistance paddle in the twin-screw kneader is different, and the others are the same. A composite paste, a positive electrode, and a lithium ion secondary battery were manufactured. Specifically, a positive electrode mixture paste was produced using a biaxial kneader with a clearance B1 = B2 = B3 = B4 = 1.0 mm. That is, in Comparative Example 1, a positive electrode mixture paste was prepared using a biaxial kneader in which the clearance (shortest distance) between the inner peripheral surface of the barrel and the outer peripheral surface of the resistance paddle was constant throughout the biaxial kneader. Manufactured. Using this positive electrode mixture paste, a positive electrode and a lithium ion secondary battery were produced.
In Comparative Example 1, as in Examples 1 to 6, the positive electrode material was charged into the biaxial kneader so that the solid content of the positive electrode mixture paste was 63.5%. Moreover, it is set as clearance C1 = C2 = 4.0mm, C3 = 1.5mm, C4 = 1.0mm similarly to Examples 1-6.

(Evaluation of viscosity variation of positive electrode mixture paste)
Regarding the positive electrode mixture pastes produced in Examples 1 to 6 and Comparative Example 1 described above, the respective viscosity variations were investigated. Specifically, in each embodiment, the positive electrode mixture paste 131A continuously discharged from the discharge port 32 of the biaxial kneader 10 is divided into sample pastes (positive electrode mixture) for 45 minutes. Collected as paste 131A). Thereby, 45 sample pastes were obtained for each example. Thereafter, the viscosity of these sample pastes was measured using a known viscometer. Furthermore, based on the measured viscosity value of each sample paste, the value of the process capability index Cpk relating to the viscosity of the positive electrode mixture paste 131A was calculated for each example. As the value of the process capability index Cpk is larger, the viscosity variation is smaller. The process capability index Cpk was similarly determined for Comparative Example 1. These results are shown in Table 1.

As shown in Table 1, in Comparative Example 1, the value of the process capability index Cpk was 1.34, and it was found that the viscosity variation of the positive electrode mixture paste produced using the biaxial kneader was large.
On the other hand, in Examples 1-6, the value of process capability index | exponent Cpk became 1.85 or more, and it turned out that the viscosity variation of the positive mix paste 131A produced using the biaxial kneader 10 is small.
From this result, it can be said that the biaxial kneader 10 of Examples 1 to 6 is a biaxial kneader capable of reducing the viscosity variation of the positive electrode mixture paste 131A.

  The reason for this result is that, in the biaxial kneader 10 of Examples 1 to 6, the inner peripheral surface 30b of the barrel 30 and the outer peripheral surfaces 51f, 52f, 53f, 54f of the resistance paddles 51, 52, 53, 54 are used. The clearances B1, B2, B3, and B4 (shortest distance) between the input port side resistance paddle portions 65b and 66c are larger than the discharge port side resistance paddle portions 66b and 66c. . That is, the clearances B1 and B2 (shortest distance) between the outer peripheral surfaces 51f and 52f of the resistance paddles 51 and 52 included in the insertion port side resistance paddle portions 65b and 65c and the inner peripheral surface 30b of the barrel 30 are both The clearances B3 and B4 (shortest distance) between the outer peripheral surfaces 53f and 54f of the shear paddles 53 and 54 included in the discharge-side resistance paddle portions 66b and 66c and the inner peripheral surface 30b of the barrel 30 are made larger. It can be said that. The effect is as described above.

(Low temperature output test)
Next, the low temperature output test was done about the lithium ion secondary battery of Examples 1-6.
Specifically, for each lithium ion secondary battery, the SOC is adjusted to 27%, and constant power discharge is performed at a certain output value (W) in a low temperature environment of −30 ° C. The time required to reach% (discharge seconds) was measured. Furthermore, the output value was set to various values, the same constant power discharge was performed, and the time (discharge seconds) required from the start of discharge to SOC 0% was measured.

  Based on these measurement results, for each lithium ion secondary battery, a correlation between the number of discharge seconds and the output value is obtained, and from this correlation, an output value (that is, −30 ° C. at which the discharge time is 2 seconds). Under a temperature environment, an output value in the case of constant power discharge from SOC 27% to SOC 0% in 2 seconds was determined as a low temperature output value (W). These results are shown in Table 1. In this test, for each example, a plurality of sample batteries were produced using the sample paste described above, and the average value of the low-temperature output values of these sample batteries was determined as the low-temperature output value (W) of each example. As shown in Table 1.

As shown in Table 1, the lithium ion secondary batteries of Example 2 and Example 6 had a low-temperature output value of less than 110W.
On the other hand, the lithium ion secondary batteries of Example 1 and Examples 3 to 5 all had a low temperature output value of 117 W or more.
From these results, the lithium ion secondary batteries of Example 1 and Examples 3 to 5 have better output characteristics (good low temperature output) than the lithium ion secondary batteries of Example 2 and Example 6. It can be said.

The reason for the difference in battery output is that the inner peripheral surface 30b of the barrel 30 and the outer peripheral surfaces 51f, 52f, 53f, 54f of the resistance paddles 51, 52, 53, 54 in the biaxial kneader 10 are as follows. This is considered to be due to the difference in the ratio of the clearances B1, B2, B3, and B4.
Specifically, in Example 1 and Examples 3 to 5, B1: B2: B3: B4 = 2.5: 2.0: 1.0 to 1.3: 1.0 to 1.3.
On the other hand, in Example 2, the ratio of B2 was increased so that B1: B2: B3: B4 = 2.5: 2.5: 1.0: 1.0. In Example 6, the ratio of B3 was increased to B1: B2: B3: B4 = 2.5: 2.0: 1.5: 1.0.

  In Examples 2 and 6, by increasing the ratio of B2 or B3, the moving speed of the positive electrode material in the twin-screw kneader 10 is increased and the shear time for the positive electrode material is shorter than in the other examples. It is thought that it became. For this reason, in Examples 2 and 6, the degree of crushing of acetylene black 133 is slightly lower than in the other examples, and the conductive material formed by connecting the positive electrode active materials 137 with acetylene black 133. The degree of the sex network is considered to be slightly lower. For this reason, in Examples 2 and 6, the internal resistance of the lithium ion secondary battery 100 is slightly higher than in the other examples, and the output characteristics (low temperature output characteristics) of the lithium ion secondary battery 100 are slightly higher. Probably lower.

  From the above results, the ratio of the clearances B1, B2, B3, and B4 is set to B1: B2: B3: B4 = 2.5: 2.0: 1.0 to 1.3: 1.0 to 1.3. Thus, it can be said that the viscosity variation of the positive electrode mixture paste 131A can be reduced and the output characteristics of the battery can be improved.

(Example 7)
In Example 7, compared with Example 3, the positive electrode mixture paste 131A was manufactured using the biaxial kneader 10 in which only the values of the clearances C1 to C3 were changed. Specifically, in Example 7, the clearance C1 = C2 = C3 = C4 = 1.0 mm. In Example 7 as well, the positive electrode material is charged into the biaxial kneader 10 so that the solid content of the positive electrode mixture paste 131A is 63.5%.

  For Example 7 as well, the value of the process capability index Cpk relating to the viscosity of the positive electrode mixture paste 131A produced was calculated in the same manner as in Examples 1 to 6 described above. The results are shown in Table 2.

As shown in Table 2, in Example 7, the value of the process capability index Cpk is 1.90, which is the same as that of Example 3 (Cpk = 1.91) using the twin-screw kneader 10. It was found that the viscosity variation of the positive electrode mixture paste 131A can be reduced.
From this result, regardless of the ratio of the clearances C1 to C4 (clearance between the barrel 30 and the shear paddle), the inner peripheral surface 30b of the barrel 30 and the outer peripheral surfaces 51f, 52f, 52f of the resistance paddles 51, 52, 53, 54 With respect to the clearances B1, B2, B3, and B4 (shortest distance) between 53f and 54f, the inlet-side resistance paddle portions 65b and 65c are made larger than the outlet-side resistance paddle portions 66b and 66c. It can be said that the viscosity variation of the positive electrode mixture paste 131A produced using the shaft kneader 10 can be reduced.

  In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

10 Biaxial kneaders 11, 12, 13, 14 for producing positive electrode composite paste Shear paddles 21 b, 21 c First shear paddle parts 22 b, 22 c Second shear paddle parts 23 b, 23 c Third shear paddle parts 24 b, 24 c Fourth shear Paddle portion 25b, 25c Input port side shear paddle portion 26b, 26c Discharge port side shear paddle portion 30 Barrel 31 Input port 32 Discharge port 35, 36 Shaft 41b, 41c, 42b, 42c Screw 51, 52, 53, 54 Resistance paddle 61b , 61c First resistor paddle portion 62b, 62c Second resistor paddle portion 63b, 63c Third resistor paddle portion 64b, 64c Fourth resistor paddle portion 65b, 65c Input port side resistor paddle portion 66b, 66c Discharge port side resistor paddle portion 100 Lithium ion secondary battery 110 Electrode body 120 Negative electrode 121 Negative electrode mixture layer 127 Negative electrode active Substance 130 Positive electrode 131 Positive electrode mixture layer 131A Positive electrode mixture paste 132 AB paste 133 Acetylene black (positive electrode material)
134 Binder (Positive electrode material)
135 Solvent (Positive electrode material)
137 Positive electrode active material (positive electrode material)
150 Separator 160 Non-aqueous electrolyte 180 Battery case B1, B2, B3, B4 Clearance DA Axial direction

Claims (1)

Two axes arranged in parallel,
A cylindrical barrel extending in the axial direction in which the axis extends;
A shear paddle disposed inside the barrel and rotating about the axis as a rotation axis;
A resistance paddle disposed inside the barrel, the resistance paddle rotating around the shaft as a rotation axis together with the shear paddle; and
In a biaxial kneading machine for producing a positive electrode mixture paste for kneading a positive electrode active material that is a positive electrode material, acetylene black, a binder and a solvent to produce a positive electrode mixture paste,
The barrel is
Located on one end side in the axial direction, and a charging port for charging the positive electrode material into the barrel,
A discharge port for discharging the positive electrode mixture paste formed by kneading the positive electrode material to the outside of the barrel, located on the other end side in the axial direction;
A plurality of the resistance paddle parts are arranged in the axial direction from the input port side to the discharge port side in each of the shafts,
The shear paddle portion is disposed adjacent to the resistance paddle portion in the axial direction in each of the shafts;
For each of the shafts, a plurality of the resistance paddle parts are divided into two: an inlet side resistance paddle part located on the inlet side and an outlet side resistance paddle part located on the outlet side. A twin screw kneader for producing a positive electrode mixture paste, wherein a clearance between the inner peripheral surface of the barrel and the outer peripheral surface of the resistance paddle is larger in the insertion port side resistance paddle portion than in the discharge port side resistance paddle portion.

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