Kneader and kneading method

Abstract

To provide a kneader and a kneading method that can achieve both restraint of damage to an electrode material and improvement in dispersibility when the electrode material is kneaded with a paddle.SOLUTION: A kneader 1 includes a barrel 2 into which an electrode material of a battery is injected, and a pair of rotating shafts 3 that is rotatably accommodated in the barrel 2 and have a plurality of paddles 16 for kneading the electrode material in the barrel 2, the plurality of paddles 16 being arranged in an axial direction. The paddle 16 has a plurality of protrusions 26 for kneading the electrode material in the barrel 2, the protrusions 26 being equally spaced in a circumferential direction. At least one of the plurality of protrusions 26 has a crest portion 28 and a sloped portion 29 (inlet side sloped portion 30). The crest portion 28 is disposed to be offset from a center to an opposite side of a paddle rotation direction A1 in a circumferential direction of the paddle 16. The sloped portion 29 (inlet side sloped portion 30) is disposed on a side of the crest portion 28 in the paddle rotation direction A1 and guides the electrode material to the crest portion 28 when the paddle 16 rotates.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a kneader and a kneading method for kneading electrode materials for batteries. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, an electrode paste manufacturing apparatus for manufacturing an electrode paste for use in a battery is well known. This electrode paste manufacturing apparatus has an input zone for inputting powder and a solvent and sending them downstream, a rough mixing zone for roughly mixing a mixture of powder and a solvent, and a kneading zone for kneading the mixture after rough mixing, inside the housing. However, the mixture has a high viscosity at the start of mixing, and if the shear force of the kneading is large, the material of the mixture may be damaged. Therefore, in the case of Patent Document 1, a rough mixing zone is provided inside the housing to prevent excessive shear force from being applied to the material at the start of mixing, making it difficult for damage to occur to the material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-50784 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of Patent Document 1, the gap between the inner wall of the housing and the paddle is widened in the rough mixing zone to achieve rough mixing without applying a large shear force to the material. However, when the gap is widened, the flow rate of the material decreases, making it difficult to disperse the material. Therefore, since the material becomes difficult to mix, there is a possibility that the efficiency of kneading will decrease.

[0005] An object of the present invention is to provide a kneading machine and a kneading method that can suppress damage to an electrode material and improve dispersibility at the same time when the electrode material is kneaded with a paddle. [Means for solving the problem]

[0006] The kneading machine that solves the above problem is configured to include a barrel into which battery electrode material is injected, and a pair of rotating shafts that are rotatably accommodated within the barrel and have a plurality of paddles in the axial direction that knead the electrode material within the barrel, wherein the paddles have a plurality of protrusions that are equally spaced in the circumferential direction and knead the electrode material within the barrel, and at least one of the plurality of protrusions has a top that is positioned offset from the center of the paddle in the circumferential direction to the opposite side of the paddle rotation direction, and a sloped portion that is positioned next to the top in the paddle rotation direction and guides the electrode material to the top when the paddle rotates.

[0007] A kneading method that solves the above problem involves injecting battery electrode material into a barrel, rotating a pair of rotating shafts having multiple paddles in the axial direction inside the barrel, and kneading the electrode material inside the barrel using the paddles having multiple protrusions spaced equally apart in the circumferential direction, wherein at least one of the multiple protrusions has a top that is positioned offset from the center of the paddle in the circumferential direction to the opposite side of the paddle rotation direction, and a sloped portion that is positioned beside the top in the paddle rotation direction, and when the paddle rotates, the electrode material is guided to the top by the sloped portion and scraped in by the top, thereby kneading the electrode material. Effect of the Invention

[0008] The present invention can suppress damage to the electrode material and improve the dispersibility of the electrode material when the electrode material is kneaded with a paddle. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a kneader according to a first embodiment. [Diagram 2] 2 is a cross-sectional view taken along line II-II of FIG. 1. [Diagram 3] FIG. 4 is an enlarged cross-sectional view showing a protrusion. [Figure 4] FIG. 13 is an explanatory diagram showing the rotation of a conventional paddle. [Diagram 5] FIG. 1 is a waveform diagram of a shear rate change waveform showing the relationship between the rotation angle of the paddle and the shear rate. [Figure 6] 1 is a graph showing the resistivity of the electrode materials of Comparative Example 2 and this Example when Comparative Example 1 is set to "1" with respect to the resistance of the electrode material obtained by drying the paste. [Figure 7] FIG. 4 is a cross-sectional view of a kneader according to a second embodiment. [Figure 8] FIG. 4 is an enlarged cross-sectional view showing a protrusion. [Figure 9] FIG. 1 is a waveform diagram of a shear rate change waveform showing the relationship between the rotation angle of the paddle and the shear rate. [Figure 10] FIG. 11 is a cross-sectional view of a kneader according to a third embodiment. [Figure 11] 11 is an enlarged cross-sectional view showing a protrusion in FIG. 10. [Figure 12] FIG. 11 is a cross-sectional view of a kneader according to a third embodiment. [Figure 13] 4 shows the protrusion of Comparative Example 3, which is a conventional paddle with a reduced gap. [Figure 14] FIG. 1 is a waveform diagram of a shear rate change waveform showing the relationship between the rotation angle of the paddle and the shear rate. [Figure 15] 13 is a table comparing the maximum shear rate [1 / s] and the maximum flow rate [m / s] of Comparative Example 3 and the third embodiment. [Figure 16] 13 is a graph showing the resistivity of the electrode material of the third embodiment when Comparative Example 3 is set as "1" with respect to the resistance of the electrode material obtained by drying the paste. [Figure 17] FIG. 11 is an enlarged cross-sectional view showing a protrusion of a first modified example. [Figure 18] FIG. 11 is an enlarged cross-sectional view showing a protrusion of a second modified example. [Figure 19] FIG. 13 is an enlarged cross-sectional view showing a protrusion of a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment) The first embodiment of the present disclosure will be described below. (Kneader 1) As shown in FIG. 1, the kneader 1 includes a barrel 2 and a shaft unit 4 having a pair of rotating shafts 3. The kneader 1 kneads, for example, an electrode material for a battery. Specifically, the kneader 1 kneads to generate a paste to be applied to a current collector of an electrode of a battery. The electrode is, for example, a positive electrode. The paste is, for example, a positive electrode composite paste. The battery is, for example, a lithium ion secondary battery.

[0011] The kneader 1 produces a positive electrode composite paste by kneading a slurry of a positive electrode material introduced into the inside of a barrel 2 with a shaft unit 4. Examples of the material for the positive electrode include a positive electrode active material, a conductive material, and a binder. The contents of the positive electrode active material, the conductive material, and the binder are not particularly limited. The conductive material is, for example, a carbon nanotube. The binder is, for example, PVDF.

[0012] (Barrel 2) 1 , the barrel 2 has a storage chamber 6 that rotatably stores the shaft unit 4. The barrel 2 has an inlet 7 for introducing an electrode material into the storage chamber 6, and an outlet 8 for discharging the electrode material kneaded by the shaft unit 4 inside the storage chamber 6. The inlet 7 and the outlet 8 are arranged such that the inlet 7 is disposed at one axial end of the barrel 2, and the outlet 8 is disposed at the other axial end of the barrel 2.

[0013] 2, the accommodation chamber 6 is formed in a shape in which a circular first accommodation chamber 10 accommodating the first rotating shaft 9 and a circular second accommodation chamber 12 accommodating the second rotating shaft 11 partially overlap when viewed from the axial direction of the accommodation chamber 6. Specifically, the accommodation chamber 6 is formed in a shape in which, for example, two D-shaped holes are symmetrically arranged when viewed from the axial direction of the accommodation chamber 6.

[0014] (Axis unit 4) 1, the shaft unit 4 has a pair of rotating shafts 3, that is, a first rotating shaft 9 and a second rotating shaft 11. The first rotating shaft 9 and the second rotating shaft 11 are arranged in parallel to each other so as to rotate in the same direction (paddle rotation direction A1 indicated by the arrow in the figure) inside the barrel 2. In this example, the first rotating shaft 9 rotates around an axis L1, and the second rotating shaft 11 rotates around an axis L2.

[0015] As shown in FIG. 2, the shaft unit 4 has a plurality of paddle pairs 14 (only one pair is shown in FIG. 2) arranged in the axial direction of the shaft unit 4. The paddle pair 14 includes a paddle 16 (first paddle 16a) attached to a shaft body 15 of the first rotating shaft 9 and a paddle 16 (second paddle 16b) attached to a shaft body 17 of the second rotating shaft 11. At both ends of the rotating shaft 3, screws 18 are formed to flow the electrode material from the upstream side to the downstream side. The screw 18 has an upstream screw 18a that flows the electrode material flowing in from the inlet 7 into the paddle 16, and a downstream screw 18b that blocks the progress of the electrode material flowing in from the paddle 16, pushes it back, and sends it to the discharge port 8. At multiple positions in the axial direction of the rotating shaft 3, pairs of resistance paddles 19 that increase the transport resistance of the electrode material are formed.

[0016] (Paddle 16) 2, first paddle 16a is accommodated in first accommodation chamber 10 so as to be rotatable about axis L1 of first rotating shaft 9. First paddle 16a is fixed to shaft body 15 by engaging with a protrusion 22 formed on the wall surface of shaft body 15. Second paddle 16b is accommodated in second accommodation chamber 12 so as to be rotatable about axis L2 of second rotating shaft 11. Second paddle 16b is fixed to shaft body 17 by engaging with a protrusion 23 formed on the wall surface of shaft body 17. First paddle 16a and second paddle 16b have a predetermined distance from the inner wall of barrel 2 (hereinafter referred to as barrel inner wall 24).

[0017] The paddle 16 (in this example, the first paddle 16a and the second paddle 16b) has a paddle body 25 that is circular when viewed in the axial direction, and a plurality of protrusions 26 that protrude partially from the paddle body 25. The protrusions 26 protrude radially outward from the paddle body 25 and are disposed at equal intervals in the circumferential direction of the paddle 16. The paddle 16 has three protrusions 26 that are equally spaced in the circumferential direction, and is thus formed in a substantially triangular shape when viewed in the direction of the rotation axis of the paddle 16.

[0018] The first paddle 16a and the second paddle 16b rotate in the same direction from the same starting point of the rotation direction. That is, the rotation phases of the first paddle 16a and the second paddle 16b are the same. In this example, the first paddle 16a and the second paddle 16b rotate to the left of the paper, that is, in the counterclockwise direction (paddle rotation direction A1 shown in FIG. 2). When the pair of paddles 16 rotate in the paddle rotation direction A1, most of the electrode material in the barrel 2 is moved in the paddle rotation direction A1 by being pushed out by the protrusion 26, but the electrode material that is around the barrel 2 and outside the circumference of the protrusion 26 passes through the gap between the barrel 2 and the protrusion 26. At that time, the electrode material is relatively transported in the opposite direction to the paddle rotation direction A1 (material flow direction: white arrow direction), and a strong shear force is applied to the electrode material in the process of passing through the protrusion 26.

[0019] 1, the multiple paddle pairs 14 are arranged such that the phase in the rotation direction is shifted by 180 degrees from each other with respect to adjacent paddle pairs 14 in the axial direction of the rotating shaft 3. Therefore, the multiple paddle pairs 14 arranged in the axial direction of the rotating shaft 3 are arranged such that every other paddle pair 14 has the same rotation phase in the axial direction of the rotating shaft 3.

[0020] (Specific shape of protrusion 26) As shown in Figures 2 and 3, at least one of the multiple protrusions 26 has an apex 28 and a sloped portion 29 (inlet-side sloped portion 30 in this example). The apex 28 is disposed offset from the center (dashed line in Figure 2) in the circumferential direction of the paddle 16 to the opposite side of the rotational direction. Three of the multiple apexes 28 are provided at intervals of 120 degrees in the circumferential direction. The apex 28 and the inlet-side sloped portion 30 are provided on all of the multiple protrusions 26. The apex 28 has a flat portion 31 that faces the barrel inner wall 24 as a surface.

[0021] The inlet-side slope portion 30 is disposed beside the apex 28 in the paddle rotation direction A1, and guides a portion of the electrode material to the apex 28 when the paddle 16 rotates. When the paddle 16 rotates, the electrode material is guided to the apex 28 by the inlet-side slope portion 30 and scraped in by the apex 28, thereby kneading the electrode material.

[0022] At least one of the multiple protrusions 26 has an outflow side slope portion 33 at a position opposite to the inflow side slope portion 30 at the apex 28. Specifically, the outflow side slope portion 33 is disposed to the side of the apex 28 in the counter paddle rotation direction A2 (shown by the dashed arrow in FIG. 3 ), and causes the electrode material that has reached the apex 28 to flow downstream. The outflow side slope portion 33 is provided on all of the multiple protrusions 26.

[0023] As shown in FIG. 3, the circumferential length R1 of the gap K1 between the barrel inner wall 24 and the inlet-side slope portion 30 is set to be longer than the circumferential length R2 of the gap K2 between the barrel inner wall 24 and the outlet-side slope portion 33. In this example, the circumferential lengths R1 and R2 are, for example, the lengths of the inlet-side slope portion 30 and the outlet-side slope portion 33. The curvature of the inlet-side slope portion 30 is set to be gentler than the curvature of the outlet-side slope portion 33. The curvature is an index that indicates how curved the curved surfaces are in the inlet-side slope portion 30 and the outlet-side slope portion 33. When the curvature is large, the degree of bending becomes steep, and when the curvature is small, the degree of bending becomes gentle. As described above, the protrusion 26 is formed in an asymmetric shape in the circumferential direction of the paddle 16.

[0024] Next, the operation of the kneading machine 1 (kneading method) of this embodiment will be described. (Kneading with paddle 16) 2, the kneader 1 kneads the slurry of the electrode material (positive electrode material in this example) introduced into the storage chamber 6 of the barrel 2 by rotating the first paddle 16a and the second paddle 16b in the same direction. When the first paddle 16a and the second paddle 16b rotate, the slurry in the storage chamber 6 is kneaded by stirring with the protrusion 26 of the first paddle 16a and the protrusion 26 of the second paddle 16b. When the protrusion 26 of the first paddle 16a and the protrusion 26 of the second paddle 16b face each other, the slurry is compressed and sheared in the process of flowing between the protrusions 26, and the slurry is kneaded.

[0025] Furthermore, when the paddle 16 rotates, the slurry in the storage chamber 6 takes a flow path that flows between the barrel inner wall 24 and the protrusions 26. That is, the slurry is not only scraped by the protrusions 26, but is also compressed and sheared by the protrusions 26 in the process of flowing between the barrel inner wall 24 and the protrusions 26. In this way, the slurry is sheared by the pressure applied to it by the protrusions 26.

[0026] The slurry introduced into the storage chamber 6 from the inlet 7 of the barrel 2 is transported from the upstream side to the downstream side while being mixed by the paddle pairs 14 arranged in the axial direction. Since resistance to transport is applied by the resistance paddles 19 on the way, the slurry is sufficiently mixed by the paddles 16 before being sent downstream. After being mixed by all the paddle pairs 14, the slurry in the storage chamber 6 is discharged to the outside from the outlet 8 of the barrel 2.

[0027] (Shear velocity occurring at protrusion 26) 4 shows an example of a conventionally shaped paddle 36 being rotated. In the case of the conventionally shaped paddle 36, the protrusions 37 have a bilaterally symmetrical shape. In this example, the rotation start position when a predetermined one of the three protrusions 37 of the conventionally shaped paddle 36 housed in the housing chamber 6 is located at the top of the page (12 o'clock on a clock) is defined as "0 degrees."

[0028] Focusing on the right side of the conventional paddle 36 on the paper, when it rotates, the shear rate generated in the protrusion 37 located at the top of the paper passes near "90 degrees" and becomes the highest. This is presumably because the protrusion 37 of one side of the paddle 36 passes opposite the paddle 36 on the opposite side, causing the flow of paste pushed out from the paddle 36 on the opposite side to collide with the protrusion 37 of the paddle 36 on the one side, and the flow rate of the paste flowing into the protrusion 37 is relatively accelerated, resulting in the highest shear rate.

[0029] The gap K4 between the conventional projection 37 and the barrel inner wall 24 is 7.5 mm. The gap K4 in the flat portion is 3.9 mm. FIG. 5 shows the result of calculation using simulation software of a shear rate change waveform S which shows the relationship between the rotation angle of the protrusion 26 (protrusion 37) at the top of the page of the right paddle 16 (conventional paddle 36) when it is rotated once and the shear rate acting on the protrusion 26 (protrusion 37). In the case of the conventional paddle 36, the shear rate is higher at the corner tip 39 than at the "center 38" of the protrusion 37. Therefore, the shear rate at the corner tip 39 is illustrated here. In FIG. 5, the shear rate change waveform S of the conventional paddle 36 is shown by a dashed line (waveform S1), and the shear rate change waveform S of the paddle 16 of this example (waveform S2) is shown by a solid line.

[0030] As can be seen from the figure, in the case of the paddle 16 of this example, the maximum value of the shear rate when the paddle 16 rotates once is reduced by about 40% compared to the conventional paddle 36. This is because the change in the material flow direction in the gap K1 between the barrel inner wall 24 and the protrusion 26 of the paddle 16 becomes gentler, suppressing the pressure applied to the paste to be sheared when the rotating protrusion 26 approaches the opposing paddle 16, and dispersing the paste over a wide area. It is presumed that the shear rate could be significantly reduced because the increase in shear force is suppressed in this way.

[0031] (Paste resistance) FIG. 6 shows the resistivity of the paste of Comparative Example 2 and this Example when Comparative Example 1 is set as "1" for the paste resistance. In order to make the resistance comparison clearer, a pair of batch-type twin-screw kneaders without screws 18 or the like was used, and the paddle shape was changed to knead paste of the same composition. Comparative Example 1 and Comparative Example 2 are pastes produced by the paddle 36 of the conventional shape described above, and the rotation speed (paddle rotation speed) of Comparative Example 1 is "800 [rpm]", and the rotation speed (paddle rotation speed) of Comparative Example 1 is "600 [rpm]". The kneading time of Comparative Example 1 and Comparative Example 2 is, for example, 10 minutes. The resistance of the paste is, for example, a value measured after drying the kneaded paste.

[0032] In the case of the sample of Comparative Example 1 with a rotation speed of 800 rpm, the maximum shear rate when simulated under the same conditions is 21530 1 / s, and the maximum flow rate is 4.6 m / s. In the case of Comparative Example 1, the paste flow rate is fast, which promotes dispersion of the conductive material. However, since the maximum shear rate is also large, the paste is easily damaged, and there is a concern that the conductive material may be defective. As a result, the resistance of the paste does not become sufficiently low.

[0033] In the case of the sample of Comparative Example 2 with a rotation speed of 600 rpm, the maximum shear rate is 13995 1 / s and the maximum flow rate is 3.4 m / s. In the case of Comparative Example 2, it is possible to lower the shear rate as the rotation speed decreases. However, the flow rate of the paste slows down, and the dispersion efficiency of the conductive material decreases. Therefore, the resistance of Comparative Example 2 is higher than that of Comparative Example 1.

[0034] The sample of this example is a paste produced by using the paddle 16 (first paddle 16a, second paddle 16b) at a rotation speed of 800 rpm. In this example, the maximum shear rate is 12908 1 / s, and the maximum flow rate is 4.6 m / s. In this way, it is possible to keep the flow rate high while keeping the shear rate low. This makes it difficult for the paste to be damaged, and also ensures the dispersion efficiency of the conductive material. Therefore, in the case of the sample of this example, the resistance is reduced by about 10% compared to Comparative Example 1. In other words, it is possible to set the resistance of the electrode to a suitable value.

[0035] (Effects of the embodiment) According to the configuration of the above embodiment, the following effects can be obtained. (1-1) The kneader 1 includes a barrel 2 into which a battery electrode material is injected, and a pair of rotating shafts 3 that are rotatably accommodated in the barrel 2 and have a plurality of paddles 16 in the axial direction that knead the electrode material in the barrel 2. The paddles 16 have a plurality of protrusions 26 that are equally spaced in the circumferential direction and that knead the electrode material in the barrel 2. At least one of the plurality of protrusions 26 has a crest 28 and a sloped portion 29 (inlet-side sloped portion 30). The crest 28 is disposed offset from the center in the circumferential direction of the paddle 16 to the opposite side of the paddle rotation direction A1. The sloped portion 29 (inlet-side sloped portion 30) is disposed next to the crest 28 in the paddle rotation direction A1, and guides the electrode material to the crest 28 when the paddle 16 rotates.

[0036] According to this configuration, the apex 28 formed on the protrusion 26 is arranged offset to the opposite side of the paddle rotation direction A1, so that the change in the gap K1 between the barrel inner wall 24 and the protrusion 26 can be made gentle in the circumferential direction. Therefore, it is possible to keep the shear force applied to the electrode material low during kneading, so that it is possible to suppress damage to the electrode material. In addition, since the apex 28 that is sufficiently close to the barrel inner wall 24 is formed on the protrusion 26, it is possible to provide a narrow flow path between the paddle 16 and the barrel inner wall 24. Therefore, the flow rate of the electrode material is also secured, so that the dispersibility of the electrode material can also be improved. As described above, it is possible to achieve both suppression of damage to the electrode material and improvement of dispersibility.

[0037] (1-2) The plurality of protrusions 26 are provided in threes at 120 degree intervals in the circumferential direction. The peaks 28 and the inclined surfaces 29 (inlet-side inclined surfaces 30) are provided on all of the plurality of protrusions 26. With this configuration, the electrode material inside the barrel 2 can be kneaded to a required viscosity by the pair of paddles 16 having a substantially triangular shape.

[0038] (1-3) At least one of the multiple protrusions 26 has an inlet-side inclined surface portion 30 as an inclined surface portion 29, and an outlet-side inclined surface portion 33 that is arranged to the side of the top portion 28 in the direction opposite to the paddle rotation direction A2 and flows the electrode material that has reached the top portion 28 downstream. The circumferential length R1 of the gap K1 between the barrel inner wall 24 and the inlet-side inclined surface portion 30 is set to be longer than the circumferential length R2 of the gap K2 between the barrel inner wall 24 and the outlet-side inclined surface portion 33. With this configuration, by focusing on the circumferential lengths R1 and R2 of the gap between the barrel inner wall 24 and the protrusion 26, it is possible to set the inflow path of the electrode material that enters between the barrel inner wall 24 and the top portion 28 during the paddle rotation to be sufficiently gentle. This further contributes to suppressing damage to the electrode material.

[0039] (1-4) The curvature of the inlet-side slope portion 30 is set to be gentler than the curvature of the outlet-side slope portion 33. With this configuration, by focusing on the curvature of the circumferential surface of the paddle 16, it is possible to set a sufficiently gentle inflow path for the electrode material that enters between the barrel inner wall 24 and the top portion 28 when the paddle rotates. This further contributes to suppressing damage to the electrode material.

[0040] (1-5) The top portion 28 has a flat portion 31 that faces the barrel inner wall 24. With this configuration, the change in the gap K1 between the barrel inner wall 24 and the protrusion 26 can be adjusted to a desired amount by changing the size of the flat portion 31. Therefore, the required shear force can be appropriately set to a desired value.

[0041] Second embodiment Next, a second embodiment will be described. The second embodiment is an example in which the paddle projection shape of the first embodiment is changed. Therefore, the same parts as those in the first embodiment are given the same reference numerals and the description is omitted, and only the different parts will be described in detail.

[0042] (Specific shape of protrusion 26) 7 and 8, the apex 28 has a corner 41 that is sharp toward the barrel inner wall 24. In this way, the apex 28 of this example is formed in a shape that does not have a flat portion. When the shape of the apex 28 has the corner 41, the circumferential length of the inlet-side slope portion 30 is longer than in the first embodiment.

[0043] (Shear velocity occurring at protrusion 26) 9 shows a shear rate change waveform S (waveform S3 in this example) showing the relationship between the rotation angle of the paddle 16 and the shear rate. As can be seen from the figure, in the case of the paddle 16 of this example, the shear rate is reduced by about 48% compared to the conventional paddle 36. This is because the change in the material flow direction is set more gently in the gap K1 between the barrel inner wall 24 and the protrusion 26 of the first paddle 16a, which promotes the suppression of the pressure applied to the paste to be sheared and the dispersion of the paste over a wide area. Therefore, the increase in shear force is further suppressed, making it possible to significantly reduce the shear rate.

[0044] (Effects of the embodiment) According to the configuration of the above embodiment, the following effects can be obtained. (2-1) The top portion 28 has a corner portion 41 that is sharpened toward the barrel inner wall 24. This configuration makes it possible to increase the distance that changes gradually in the circumferential direction in the gap K1 between the barrel inner wall 24 and the inclined surface portion 29 (the inlet-side inclined surface portion 30). This further contributes to suppressing damage to the electrode material.

[0045] Third embodiment Next, a third embodiment will be described. The third embodiment is an example in which the paddle projection shape of the first and second embodiments is changed. Therefore, the same parts as those of the first and second embodiments are given the same reference numerals, and the description is omitted, and only the different parts will be described in detail.

[0046] Basically, there was a problem that the narrower the gap K between the barrel inner wall 24 and the protrusion 26, the higher the shear rate [1 / s] and the more likely the electrode material would be damaged. Therefore, in the first and second embodiments, the length of the inlet side slope portion 29 (30) was made longer than the outlet side slope portion 33 to mitigate the sudden increase in pressure. However, with such a configuration, although the shear rate [1 / s] can be reduced, at the same time, there was a trade-off problem that the flow velocity [m / s] was slow and dispersibility could not be improved.

[0047] Therefore, in the kneader of the third embodiment, the gap K3 between the barrel inner wall 24 and the corner 43 is narrowed, so that the flow velocity [m / s] is increased and the dispersibility is improved. On the other hand, after the flow velocity [m / s] is increased, the pressure [Pa] on the paste is immediately reduced to reduce the shear force [Pa], thereby suppressing damage to the electrode material. This configuration makes it possible to achieve both suppression of damage to the electrode material and improvement of dispersibility.

[0048] (Specific shape of protrusion 26) FIG. 10 is a cross-sectional view of the kneader 1 according to the third embodiment. The rotation angle in this state is 0 degrees. FIG. 11 is a cross-sectional view showing an enlarged projection 26 of FIG. 10. As shown in FIG. 10, the top 28 of the projection 26 of the third embodiment has a corner 43 that is sharp toward the barrel inner wall 24. The top 28 of this embodiment is formed in a shape that does not have a flat portion. The shape of the top 28 has a corner 43, and the circumferential length of the inlet side slope 42 is configured to be longer than the circumferential length of the inlet side slope 30 of the first and second embodiments. Therefore, this configuration is more unlikely to cause a sudden change in compression force than the first and second embodiments.

[0049] As shown in FIG. 11, the outflow side of corner 43 is provided with step 44. Step 44 forms step 44, which is a flat surface that moves away from barrel inner wall 24 in a generally radial direction from corner 43 toward outflow slope 46, between corner 43 and outflow slope 46. The outflow end of step 44 has corner 45 that forms a recess between outflow slope 46. For example, in this embodiment, the interior angle of corner 45 is approximately 120 degrees. Outflow slope 46 forms a gentle curve that is slightly larger than the radius of shaft body 15 so as to contact the surface of shaft body 15 from corner 45. With this configuration, the paste that has passed through corner 45 has an increased cross-sectional area, and the pressure [Pa] applied to the paste is rapidly reduced.

[0050] As shown in Fig. 11, more specifically, the gap K3 between the barrel inner wall 24 and the corner 43 is narrowed, and in this embodiment, it is set to, for example, 1 [mm]. Therefore, the flow velocity [m / s] of the paste passing through this gap K3 is fast. Between the barrel inner wall 24 and the step 44, the gap suddenly becomes larger on the outflow side, and the flow velocity [m / s] of the paste also suddenly becomes slower. In addition, after passing the corner 45, the gap between the barrel inner wall 24 and the outflow side slope 46 gradually expands further, and becomes the largest gap at the contact point with the shaft body 15.

[0051] 4, the gap K4 between the protrusion 37 and the barrel inner wall 24 in the conventional shape is 7.5 mm, whereas the gap K3 between the barrel inner wall 24 and the corner 43 in this embodiment is very narrow. Also, while the gap gradually increases at the inclined surface on the outflow side of the protrusion 37 in the conventional shape, the gap suddenly increases at the step 44 in this embodiment.

[0052] FIG. 12 is also a cross-sectional view of the kneader 1 according to the third embodiment. However, FIG. 12 shows a state in which the first paddle 16a and the second paddle 16b are rotated 105 degrees counterclockwise in the cross-sectional view of the kneader according to the third embodiment shown in FIG. 10. As shown in FIG. 12, the rotation of the first paddle 16a and the second paddle 16b brings the corner 43 of the first paddle 16a and the inlet-side slope 42 of the second paddle 16b into a position close to each other. At this time, the gap K5 when the opposing corner 43 and the inlet-side slope 42 are closest to each other is about 1 [mm]. At this point, the shear force [Pa] also peaks, but immediately thereafter the shear force [Pa] drops sharply, suppressing damage to the electrode material.

[0053] (Shear velocity occurring at protrusion 26) FIG. 13 shows the projection 37 of Comparative Example 3, which is a conventional paddle 16 in which the gap K4=7.5 [mm] is reduced to the gap K6=1 [mm]. In the conventional paddle 16 shown in FIG. 4, the gap K4 between the projection 37 and the barrel inner wall 24 is provided in the housing to prevent excessive shear force [Pa] from being applied to the material at the start of mixing, thereby making it difficult for the material to be damaged. Specifically, K4=7.5 [mm]. However, in the conventional coarse mixing zone, although the shear force [Pa] can be suppressed, the flow rate [m / s] of the paste is slow, making it difficult for the material to disperse. Therefore, since the material becomes difficult to mix, there is a possibility that the efficiency of kneading will decrease.

[0054] 13, the paddle 16 of Comparative Example 3 has a gap K6 of 1 mm between the protrusion 37 and the barrel inner wall 24. The other shapes of the paddle 16 are the same as those of the paddle 16 shown in FIG.

[0055] FIG. 14 shows a shear rate change waveform S (waveform S5 in the third embodiment, and waveform S4 in the comparative example 3) showing the relationship between the rotation angle [°] of the paddle 16 and the shear rate [1 / s]. The maximum shear rate [1 / s] was derived by simulation. As can be seen from FIG. 12, in the case of the paddle 16 of the third embodiment, the maximum shear rate [1 / s] was 196318 [1 / s] at the time of 105 degrees of rotation counterclockwise as indicated by the arrow. In contrast, in the case of the paddle 36 of the conventional shape shown in the comparative example 3, the maximum shear rate [1 / s] was 237272 [1 / s] at the time of 90 degrees of rotation. That is, compared to the paddle of the comparative example 3, the shear rate [1 / s] of the paddle of the third embodiment is reduced by about 17%. This is because the change in the material flow direction is set more gently in the gap K3 between the barrel inner wall 24 and the protrusion 26 of the first paddle 16a, which promotes the suppression of the pressure applied to the paste to be sheared and the dispersion of the paste over a wide area. Therefore, the increase in the shear force [Pa] is further suppressed, making it possible to significantly reduce the shear rate [1 / s].

[0056] (Flow velocity occurring at protrusion 26) FIG. 15 is a table comparing the maximum shear rate [1 / s] and maximum flow rate [m / s] of Comparative Example 3 and the third embodiment. The maximum shear rate [1 / s] and maximum flow rate [m / s] were derived by simulation. The "ratio" is the ratio obtained for each of the maximum shear rate [1 / s] and maximum flow rate [m / s] by "A: Comparative Example 3 / B: Third embodiment". From FIG. 15, at the same rotation speed of 800 [rpm], the maximum shear rate [1 / s] of A: Comparative Example 3 was 237272 [1 / s], and the maximum shear rate [1 / s] of B: Third embodiment was 196318 [1 / s], resulting in B / A=0.83. On the other hand, at the same rotation speed of 800 [rpm], A: Comparative Example 3 has a maximum flow velocity [m / s] of 36.8 [m / s], and B: Third embodiment has a maximum flow velocity [m / s] of 34.3 [m / s], resulting in B / A=0.93. What can be derived from this result is that although the gaps K5 and K3 are both 1 [mm], a 13% reduction in the maximum shear velocity [1 / s] is achieved. On the other hand, the maximum flow velocity [m / s] is reduced by only 7%. That is, according to the configuration of the protrusion 26 of the third embodiment, the maximum shear velocity [1 / s] is greatly suppressed, while the reduction in the maximum flow velocity [m / s] is kept small.

[0057] From the above simulation experiments, it was confirmed that the configuration of the protrusions 26 of the third embodiment can simultaneously suppress damage to the electrode material and improve dispersibility. (Action of this embodiment) Fig. 16 is a graph showing the resistivity of the electrode material of the third embodiment when Comparative Example 3 is set as "1" for the resistance of the electrode material after drying the paste. As shown in Fig. 16, the electrode resistance of the third embodiment was able to achieve a 4% reduction compared to the electrode resistance of Comparative Example 3. This confirmed that the resistance of the electrode material could be reduced by achieving both suppression of damage to the electrode material and improvement of dispersibility.

[0058] (Effects of the embodiment) According to the configuration of the third embodiment, the following effects can be obtained. (3-1) The top 28 has a step portion 44 between the corner 43 and the outflow side slope 46, which is spaced apart from the barrel inner wall 24 from the corner 43 toward the outflow side slope 46. This configuration can increase the flow rate [m / s] of the paste in the gap K3 between the corner 43 and the outflow side slope 46. In addition, the pressure on the paste can be reduced on the outflow side of the corner 43, and an increase in shear force [Pa] can be suppressed. As a result, there is an effect that it is possible to simultaneously suppress damage to the electrode material and improve dispersibility.

[0059] (Other embodiments) This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0060] 17 is an enlarged cross-sectional view of the protrusion 26 of the first modified example. As shown in FIG. 17, the top 28 has a corner 43 at the outflow end of the inflow slope 42, as in the second embodiment. In the first modified example, a recess 47 having a curvature larger than the curvature of the curved surface of the outflow slope 46 is provided between the corner 43 and the outflow slope 46. In the third embodiment, the corner 45 is provided, but in this modified example, the recess 47 smoothly connects the step 44 and the outflow slope 46 with a curved surface. It goes without saying that the curved surface constituting the recess 47 can be appropriately optimized by a person skilled in the art. It is also possible to form the entire recess 47 from the corner 43 to the outflow slope 46 without the step 44.

[0061] Even with this configuration, the pressure on the paste can be reduced on the outflow side of the corner 43, and an increase in shear force [Pa] can be suppressed. As a result, it is possible to suppress damage to the electrode material and improve the dispersibility at the same time. Furthermore, it is possible to make the paste flow smoothly.

[0062] Fig. 18 is an enlarged cross-sectional view of the protrusion 26 of the second modified example. As shown in Fig. 18, the apex 28 has a flat portion 48 similar to the flat portion 31 of the first embodiment. It also has a step portion 44 similar to the third embodiment. That is, the apex 28 has a step portion 44 between the outflow side end portion 49 of the flat portion 48 and the outflow side slope portion 46, the step portion 44 being spaced away from the barrel inner wall 24 from the outflow side end portion 49 of the flat portion 48 toward the outflow side slope portion 46. The outflow side end of the step portion 44 has a corner portion 45 that forms a recess between the outflow side slope portion 46 and the outflow side slope portion 46.

[0063] Such a configuration provides the same effects as those of the first embodiment, as well as those of the third embodiment. In the case of this modification, the gap K can be made narrower than in the first embodiment.

[0064] Fig. 19 is an enlarged cross-sectional view of the protrusion 26 of the third modified example. As shown in Fig. 19, the top 28 has a flat portion 48 similar to the flat portion 31 of the first embodiment. It also has a recess 47 similar to the first modified example.

[0065] With this configuration, in addition to the same effects as the first embodiment, the same effects as the first modified example are achieved. In each embodiment, the number of protrusions 26 is not limited to three, but may be four or more, or may be two or less.

[0066] In each embodiment, among the plurality of protrusions 26 , only a specific protrusion 26 may have a shape including the peak 28 and the slope 29 . In each embodiment, the shape of the top portion 28 is not limited to a shape having a flat portion 31 or a shape having corners 41. For example, the shape may be changed to another shape, such as a shape having a plurality of projections and recesses on the surface.

[0067] In each embodiment, the electrode material to be kneaded is not limited to a paste for a positive electrode of a lithium ion secondary battery, but may be a paste for a negative electrode of a lithium ion secondary battery. In each embodiment, the secondary battery is not limited to a lithium ion secondary battery or a nickel hydrogen secondary battery. If a paste needs to be prepared, a secondary battery other than a lithium ion secondary battery or a nickel hydrogen secondary battery may be used.

[0068] In each embodiment, the battery is not limited to a sealed battery having an external shape of a rectangular parallelepiped, and may be a battery having a shape other than a rectangular parallelepiped, such as a cylindrical shape. In each embodiment, the secondary battery is not limited to being installed in an electric vehicle or a hybrid vehicle, but may be installed in a gasoline vehicle, a diesel vehicle, etc. The secondary battery may also be used as a power source for moving objects such as trains, ships, aircraft, and robots, and for electrical products such as information processing devices.

[0069] In each embodiment, the phrase "at least one" used in this disclosure means "one or more" of the desired options. As an example, the phrase "at least one" used in this disclosure means "only one option" or "both of two options" if the number of options is two. As another example, the phrase "at least one" used in this disclosure means "only one option" or "any combination of two or more options" if the number of options is three or more.

[0070] In each embodiment, the present disclosure has been described based on the examples, but it is understood that the present disclosure is not limited to the examples or structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0071] 1...kneader, 2 barrel, 3...rotating shaft, 16...paddle, 24...barrel inner wall, 26, 37...projection, 28...top, 29...slope, 30...inlet side slope, 31, 48...flat, 33, 46...outlet side slope, 41, 43, 45...corner, 44...step, 47...recess, 49...outlet side end, K (K1 to K5)...gap, A1...paddle rotation direction, A2...anti-paddle rotation direction, R1...circumferential length, R2...circumferential length.

Claims

1. A kneader including: a barrel into which a battery electrode material is injected; and a pair of rotating shafts that are rotatably accommodated in the barrel and have a plurality of paddles in the axial direction for kneading the electrode material in the barrel, The paddle has a plurality of protrusions at equal intervals in a circumferential direction for kneading the electrode material in the barrel, At least one of the plurality of protrusions is A top portion disposed on an opposite side to a paddle rotation direction from a center in the circumferential direction of the paddle; a sloped portion disposed beside the top portion in the paddle rotation direction and configured to guide the electrode material to the top portion when the paddle rotates.

2. The plurality of protrusions are provided in threes at intervals of 120 degrees in the circumferential direction, The kneader according to claim 1 , wherein the top portion and the inclined surface portion are provided on all of the plurality of protrusions.

3. At least one of the plurality of protrusions is An inlet side slope portion as the slope portion; an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; The kneader according to claim 1 , wherein a circumferential length of a gap between the barrel inner wall and the inlet-side inclined surface portion is set to be longer than a circumferential length of a gap between the barrel inner wall and the outlet-side inclined surface portion.

4. At least one of the plurality of protrusions is An inlet side slope portion as the slope portion; an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; The kneader according to claim 1 , wherein the inlet-side inclined surface portion has a curvature that is gentler than the curvature of the outlet-side inclined surface portion.

5. The kneader according to claim 1 , wherein the top portion has a flat portion that faces the inner wall of the barrel.

6. an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; 6. The kneader according to claim 5, wherein the top portion has a recess between the outflow side end portion of the flat portion and the outflow side slope portion, the recess having a curvature larger than the curvature of the curved surface of the outflow side slope portion.

7. an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; The kneader according to claim 5 , wherein the top portion has a step portion between the outflow side end portion of the flat portion and the outflow side slope portion, the step portion being spaced apart from the barrel inner wall from the outflow side end portion of the flat portion toward the outflow side slope portion.

8. The kneader according to claim 1 , wherein the top portion has a sharp corner portion facing an inner wall of the barrel.

9. an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; The kneader according to claim 8 , wherein the top portion has a recess between the corner portion and the outflow side slope portion, the recess having a curvature larger than the curvature of the curved surface of the outflow side slope portion.

10. an outflow side slope portion disposed to the side of the top in a direction opposite to the paddle rotation direction, for causing the electrode material that has reached the top to flow downstream; The kneader according to claim 8 , wherein the top portion has a step portion between the corner portion and the outflow side slope portion, the step portion being spaced apart from the inner wall of the barrel from the corner portion toward the outflow side slope portion.

11. A method for kneading a battery electrode material in a barrel, and rotating a pair of rotating shafts having a plurality of paddles in an axial direction in the barrel, thereby kneading the electrode material in the barrel by the paddles having a plurality of protrusions provided at equal intervals in a circumferential direction, comprising: a top portion disposed on at least one of the plurality of protrusions, the top portion being shifted toward the opposite side of the paddle rotation direction from the center in the circumferential direction of the paddle, and a sloped portion disposed beside the top portion in the paddle rotation direction, and the electrode material is kneaded by guiding the electrode material to the top portion by the sloped portion and scraping it in at the top portion when the paddle rotates.

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