Mixing machine and mixing method

Abstract

The present invention provides a kneader and a kneading method that can reduce the likelihood of damage occurring during the kneading of electrode materials. [Solution] The kneader 1 comprises a barrel 2 into which the electrode material for the battery is fed, a pair of screws 6 that rotate in the same direction to transport the electrode material inside the barrel 2, and a pair of paddles 7 that are provided to rotate integrally with each of the screws 6 to shear the electrode material during the transport process. The barrel 2 has a powder inlet 11 located upstream of the paddles 7 into which the powder of the electrode material is fed, and a solvent inlet 12 located between the paddles 7 and the powder inlet 11 in the transport path of the electrode material into which the solvent for the electrode material is fed. The screws 6 have a first screw section 22 located opposite the powder inlet 11, and a second screw section 23 located opposite the solvent inlet 12 and formed in a shape that has a lower shear force than the first screw section 22.

Description

Technical Field

[0001] The present disclosure relates to a kneader for kneading an electrode material of a battery and a kneading method.

Background Art

[0002] Conventionally, as disclosed in Patent Document 1, an electrode paste manufacturing apparatus for manufacturing a paste-like electrode material used for an electrode plate of a battery is well-known. The paste-like electrode material is manufactured, for example, by kneading a powder and a solvent. Therefore, at the start of kneading the powder and the solvent, the viscosity of the slurry in which the powder and the solvent are mixed is high. Therefore, if a high shearing force is applied to the slurry at the start of kneading, the material may be damaged. Therefore, in the case of Patent Document 1, by providing a "coarse kneading zone" in which the distance between the inner wall of the barrel and the paddle is made larger than before, an excessive shearing force is not applied to the material at the start of kneading.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the powder and the solvent introduced into the barrel are first conveyed to the paddle while being stirred by the screw. The powder and the solvent stirred by the screw are in a state before being slurried and starting to be compatible with each other, that is, a so-called wet state. The wet state has a very high viscosity. Therefore, if an excessive shearing force is applied to the material in the wet state from the screw, the material may be damaged.

[0005] An object of the present disclosure is to provide a kneader and a kneading method that can hardly cause damage during kneading of an electrode material.

Means for Solving the Problems

[0006] A kneader that solves the above problem comprises a barrel into which battery electrode material is introduced, a pair of screws that rotate in the same direction to transport the electrode material inside the barrel, and a pair of paddles that are provided to rotate integrally with each of the pair of screws and shear the electrode material during the transport process, wherein the barrel has a powder inlet located upstream of the paddles into which powder of the electrode material is introduced, and a solvent inlet located between the paddles and the powder inlet in the transport path of the electrode material into which the solvent of the electrode material is introduced, and the screws have a first screw section located opposite the powder inlet, and a second screw section located opposite the solvent inlet and formed in a shape that has a lower shear force than the first screw section.

[0007] A kneading method for solving the above-mentioned problems is a method for conveying electrode material for a battery that has been placed inside a barrel by a pair of screws that rotate in the same direction, and shearing the electrode material during the conveying process by a pair of paddles that are provided to be rotatable integrally with each of the pair of screws, comprising the steps of: introducing powder of the electrode material from a powder inlet provided in the barrel so as to be located upstream of the paddles; introducing solvent of the electrode material from a solvent inlet provided in the barrel so as to be located between the paddles and the powder inlet in the conveying path of the electrode material; and using a screw having a first screw portion located opposite the powder inlet and a second screw portion located opposite the solvent inlet and formed in a shape that has a lower shear force than the first screw portion, to agitate the powder and the solvent and convey them to the paddles. [Effects of the Invention]

[0008] This disclosure makes it possible to reduce the likelihood of damage occurring during the mixing of electrode materials. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing the configuration of the kneading machine according to the first embodiment. [Figure 2] This is a diagram showing the shapes of the first screw section and the second screw section. [Figure 3] This is a cross-sectional view of the mixing machine. [Figure 4] This is an explanatory diagram showing the calculation points for the shear rate simulation. [Figure 5] This waveform diagram shows the change in shear viscosity as a function of shear rate for measured paste values. [Figure 6] This waveform diagram shows the simulation results of the shear rate at the calculation point. [Figure 7] This graph compares the cumulative energy values ​​of the conventional method and this example. [Figure 8] This graph compares the blackness of the conventional image with that of this example. [Figure 9] This is a configuration diagram showing the shapes of the first screw portion and the second screw portion according to the second embodiment. [Figure 10] This is an explanatory diagram showing the calculation points for the shear rate simulation. [Figure 11] This graph compares the cumulative energy values ​​of the conventional method and this example. [Figure 12] This graph compares the blackness of the conventional image with that of this example. [Modes for carrying out the invention]

[0010] (First Embodiment) The following describes a first embodiment of this disclosure. This disclosure is not limited to these examples and includes all modifications in the sense and scope equivalent to the claims. For illustrative purposes, the drawings may exaggerate or simplify some of the components, and the dimensional proportions of the components may differ from those of the actual components.

[0011] (Mixing machine 1) As shown in FIG. 1, the kneader 1 includes a barrel 2 into which the electrode material of the battery is charged, and a pair of kneading shafts 3 for kneading the electrode material charged into the barrel 2. The kneading shafts 3 are rotated in the same direction by an actuator 4 such as a motor. The kneading shafts 3 convey and knead the electrode material charged into the barrel 2 from upstream to downstream by rotation. The kneader 1 generates a paste to be applied to the current collector of the electrode plate by kneading the electrode material. The electrode plate in this example is a negative electrode plate. The paste in this example is a negative electrode composite paste. The battery in this example is a lithium-ion secondary battery.

[0012] Each of the kneading shafts 3 has a shaft portion 5 serving as a rotation axis. A plurality of screws 6 and paddles 7 arranged in the axial direction are integrally rotatably attached to the shaft portion 5. Thus, the kneader 1 includes a pair of screws 6 that convey the electrode material inside the barrel 2 by rotating in the same direction, and paddles 7 that are provided so as to be integrally rotatable with each of the pair of screws 6 and shear the electrode material during the conveying process.

[0013] (Electrode material) The electrode material to be kneaded by the kneader 1 shown in FIG. 1 includes an active material and an additive. When the electrode material is the material of the negative electrode plate, the electrode material of the negative electrode plate includes a negative electrode active material and a negative electrode additive. The negative electrode active material is, for example, a powdery carbon material made of graphite (graphite) or the like. The negative electrode active material in this example is, for example, natural graphite. The negative electrode additive includes, for example, a negative electrode solvent, a negative electrode thickener, and a negative electrode binder. The negative electrode solvent is, for example, water. As described above, the electrode material of the battery includes a solid component and a solvent.

[0014] The negative electrode thickener is, for example, a polymer system that is insoluble in an organic solvent and exhibits viscosity when dissolved in water. The polymer system uses, for example, cellulose derivatives such as carboxymethyl cellulose (CMC) and methyl cellulose (MC).

[0015] For the negative electrode binder, for example, a polymer material dispersed in water is used. As the polymer material, for example, rubbers such as vinyl acetate copolymer, styrene-butadiene block copolymer (SBR), acrylic acid-modified SBR resin (SBR-based latex), and gum arabic are used. As the polymer material, for example, fluorine-based resins such as polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylene-tetrafluoroethylene copolymer (ETFE) are used.

[0016] (Barrel 2) As shown in FIGS. 1 to 3, the barrel 2 has a housing chamber 9 that rotatably houses a pair of kneading shafts 3. As shown in FIG. 3, the housing chamber 9 has a first housing chamber 9a that houses the first kneading shaft 3a, which is one of the pair of kneading shafts 3, and a second housing chamber 9b that houses the second kneading shaft 3b, which is the other of the pair of kneading shafts 3. The first housing chamber 9a and the second housing chamber 9b are formed in a shape in which circular holes partially overlap when viewed from the axial direction of the kneading shaft 3.

[0017] As shown in FIG. 1, the barrel 2 has a powder inlet 11 into which the powder of the electrode material is introduced, a solvent inlet 12 into which the solvent of the electrode material is introduced, a binder inlet 13 into which the binder is introduced, and a discharge port 14 for discharging the kneaded electrode material. The solvent inlet 12 in this example is arranged near the powder inlet 11. The barrel 2 also has a downstream solvent inlet 12a for introducing the solvent between the solvent inlet 12 and the binder inlet 13. The powder inlet 11, the solvent inlet 12, the downstream solvent inlet 12a, the binder inlet 13, and the discharge port 14 are arranged in this order from the upstream to the downstream of the conveyance path of the electrode material in the housing chamber 9.

[0018] (Screw 6) As shown in Figure 1, the screw 6 has a first screw 6a, a second screw 6b, a third screw 6c, and a fourth screw 6d, arranged in order from upstream to downstream along the transport path of the electrode material in the containment chamber 9. These screws 6 have blades 16 that are formed in a spiral shape around the axis of the screw 6. These screws 6 are arranged so that the blades 16 of pairs of screws 6 interlock with each other.

[0019] The first screw 6a is positioned opposite the powder inlet 11 and the solvent inlet 12. The first screw 6a conveys the powder introduced from the powder inlet 11 and the solvent introduced from the solvent inlet 12 downstream while stirring them.

[0020] The second screw 6b is positioned opposite the downstream solvent inlet 12a. The second screw 6b transports the electrode material in the containment chamber 9 and the solvent introduced from the downstream solvent inlet 12a downstream while stirring them.

[0021] The third screw 6c is positioned opposite the binder inlet 13. The third screw 6c conveys the electrode material in the containment chamber 9 and the binder introduced from the binder inlet 13 downstream while stirring them.

[0022] The fourth screw 6d is located at the end of the transport path for the electrode material in the containment chamber 9. The fourth screw 6d is a return screw that directs the electrode material located at the end of the transport path for the electrode material in the containment chamber 9 toward the discharge port 14 by forming the spiral direction of the blade 16 in the opposite direction to the other screws (first screw 6a, second screw 6b, and third screw 6c).

[0023] (Paddle 7) As shown in Figure 1, the paddles 7 have a first paddle 7a, a second paddle 7b, and a third paddle 7c, arranged in order from upstream to downstream along the transport path of the electrode material in the containment chamber 9. These paddles 7 are formed as a group of paddles arranged in the axial direction of the paddles 7, with pairs of paddles positioned opposite each other in a direction perpendicular to the axis of the paddle 7. These paddles 7 mix the electrode material by shearing it during the transport process.

[0024] As shown in Figure 3, the paddle 7 is formed in a shape in which multiple tops 18 are arranged at equal intervals in the circumferential direction. In this example, there are a total of three tops 18 arranged at 120-degree intervals in the circumferential direction of the paddle 7. Multiple paddles 7 arranged in a line in the axial direction are positioned so that the tops 18 of adjacent paddles 7 are offset from each other by a predetermined amount in the circumferential direction.

[0025] As shown in Figure 1, the paddle 7 has a first resistance paddle 19 positioned between the first paddle 7a and the second screw 6b, and a second resistance paddle 20 positioned between the second paddle 7b and the third screw 6c. The first resistance paddle 19 and the second resistance paddle 20 are formed as a group of paddles arranged in the axial direction of the first resistance paddle 19 and the second resistance paddle 20, with pairs of paddles positioned opposite each other in directions perpendicular to their axes. The first resistance paddle 19 and the second resistance paddle 20 compress the electrode material being transported, thereby making the bulk density as uniform as possible.

[0026] The first paddle 7a is positioned between the first screw 6a and the first resistance paddle 19. The first paddle 7a is a wet paddle that mixes the electrode material stirred by the first screw 6a, specifically a mixture of powder introduced from the powder inlet 11 and solvent introduced from the solvent inlet 12, by shearing.

[0027] The second paddle 7b is positioned between the second screw 6b and the second resistance paddle 20. The second paddle 7b is a kneading paddle that kneads the electrode material stirred by the second screw 6b, specifically the mixture of the material compressed by the first resistance paddle 19 and the solvent introduced from the downstream solvent inlet 12a, by shearing.

[0028] The third paddle 7c is positioned between the third screw 6c and the fourth screw 6d. The third paddle 7c is a binder mixing paddle that mixes the electrode material stirred by the third screw 6c, specifically the material compressed by the second resistance paddle 20, and the binder introduced from the binder inlet 13, by shearing.

[0029] (Specific reference to the powder inlet 11 and the solvent inlet 12) As shown in Figure 1, the powder inlet 11 is located upstream of the paddle 7 (in this example, the first paddle 7a). Specifically, the powder inlet 11 is located at the upstream end of the electrode material transport path in the containment chamber 9. The powder introduced into the powder inlet 11 is, for example, an active material and a thickener. The solvent inlet 12 is located between the paddle 7 (in this example, the first paddle 7a) and the powder inlet 11 in the electrode material transport path.

[0030] (Specific reference to screw shape) As shown in Figure 2, the screw 6 (in this example, the first screw 6a) has a first screw portion 22 positioned opposite the powder inlet 11, and a second screw portion 23 positioned opposite the solvent inlet 12 and formed in a shape that has a lower shear force than the first screw portion 22. Thus, the screw 6 in this example has a first screw portion 22 and a second screw portion 23 with different shear forces in the region where the powder and solvent are mixed.

[0031] In this example, the second clearance W2, which is the clearance between the inner wall of barrel 2 and the second screw portion 23, is set to a value within the range of the first clearance W1, which is the clearance between the inner wall of barrel 2 and the first screw portion 22, and the third clearance W3, which is the clearance between the inner wall of barrel 2 and the paddle 7 (in this example, the first paddle 7a). In this way, the first screw portion 22, the second screw portion 23, and the first paddle 7a are set to generate different shear forces by changing the distance between them and the inner wall of barrel 2. In this example, the first clearance W1 is set to 0.5 mm and the second clearance W2 is set to 2.0 mm.

[0032] The first clearance W1 should be set to a value that allows the first screw portion 22 to be subjected to the required high shear force. The second clearance W2 should preferably be set to a value that prevents excessive shear force from being applied to the mixture of powder and solvent, which is wet at the beginning of mixing. The third clearance W3 is the distance between the top 18 of the first paddle 7a and the inner wall of the barrel 2. The third clearance W3 should be set to a value that allows the first paddle 7a to be subjected to the required shear force.

[0033] In this example, the first screw portion 22 and the second screw portion 23 are arranged coaxially. Furthermore, the second clearance W2 is formed to be larger than the first clearance W1 by making the diameter of the second screw portion 23 smaller than the diameter of the first screw portion 22. Thus, the first screw portion 22 and the second screw portion 23 have the same twist shape of the blade 16, but are formed to have different diameters.

[0034] (Operation of the first embodiment) Next, the operation of the kneader 1 and the kneading method of this embodiment will be described. (The process of mixing electrical materials) As shown in Figure 2, when manufacturing a paste by kneading electrode materials, the first step is to introduce powder through the powder inlet 11 provided in barrel 2. Subsequently, the second step is to introduce solvent through the solvent inlet 12 provided in barrel 2. The powder and solvent may be introduced simultaneously, or the powder may be introduced first, followed by the solvent.

[0035] When powder and solvent are introduced into barrel 2, a screw 6 (in this example, the first screw 6a) having a first screw section 22 and a second screw section 23 agitates the powder and solvent, and then transports them to the first paddle 7a. Specifically, the powder introduced from the powder inlet 11 is transported to the second screw section 23 by the rotation of the first screw section 22. When the powder reaches the second screw section 23, it mixes with the solvent introduced from the solvent inlet 12 and becomes wet, and this wet material is transported to the first paddle 7a while being agitated by the second screw section 23.

[0036] When the material reaches the first paddle 7a, it is kneaded while being sheared by the first paddle 7a. Thereafter, the material is kneaded by the first resistance paddle 19, the second screw 6b, the second paddle 7b, the second resistance paddle 20, the third screw 6c, and the third paddle 7c, and is discharged to the outside of the barrel 2 from the discharge port 14.

[0037] (Simulation of the shear rate of the first screw 6a) As shown in Figures 3 and 4, the shear rate applied to the paste from the blade 16 when the first screw 6a is rotated is calculated by simulation. Here, the calculation point Pa used in CAE (Computer Aided Engineering) analysis, specifically the shear rate occurring at the position where the change in shear rate is expected to be greatest when the first screw 6a rotates, is calculated by CAE simulation. In this example, the calculation point Pa is set to the position of the apex of rotation of the first screw member 6r, which is located on the right side of the paper when the screw 6 is viewed from the axial direction (the "12 o'clock" position on a clock face), among the screw pair (first screw member 6r, second screw member 6s).

[0038] The software used in the simulation, for example, employs 3D transient flow analysis and defines the slurry as a fluid. The physical properties of the paste used in the simulation include, for example, a density of "2019 kg / m³". 3 The viscosity definition is set to "Use measured paste values," and surface tension and contact angle are set to "None." Furthermore, the simulation input conditions are set, for example, to an inflow velocity of "0.0017 m / s," an inflow volume of "0.04 kg / s," a liquid phase filling rate of "100%," and a rotation speed of screw 6 of "800 rpm."

[0039] As shown in Figure 5, the simulation is performed using measured paste values. In this example, the measured paste values ​​show a peak in shear viscosity [Pa·s] when the shear rate [1 / s] is between 0.01 and 1, and the shear viscosity decreases from the peak value as the shear rate increases.

[0040] Figure 6 shows the simulation results of the shear rate at the calculation point Pa. In this figure, the shear rate that occurs in the case of a conventional screw is shown by a dashed line, and the shear rate that occurs with the first screw 6a (in this example, the second screw section 23) is shown by a solid line. In the conventional screw, the distance between the screw and the inner wall of the barrel 2 at the position facing the powder inlet 11 and the distance between the screw and the inner wall of the barrel 2 at the position facing the solvent inlet 12 are the same value (for example, 0.5 mm). Furthermore, the shear rates for the second screw section 23 in this example and the conventional screw are calculated at 15-degree intervals in the range from 0 to 120 degrees. Note that in this figure, after 120 degrees, the calculation point Pa passes through the barrel 2, so the shear rate does not change significantly from the range between 0 and 60 degrees. Therefore, the waveform after 120 degrees is omitted.

[0041] As shown in the figure, it can be seen that the shear rate of the second screw section 23 in this example is lower than that of a conventional screw. Specifically, when the phase of the measurement site is around 80 to 85 degrees, an effect of reducing the shear rate by about 50% is obtained. Therefore, when stirring a wet material in which powder and solvent have just begun to be mixed by the second screw section 23, excessive shear force is not applied to the material from the second screw section 23.

[0042] Figure 7 shows the integrated energy value [N / m] imparted to the slurry at calculation point Pa when the first screw 6a is rotated once. The integrated energy value is, for example, the mean shear stress [N / m]. 2 The cumulative energy value is calculated by multiplying the shear rate by the slurry distance [m]. The average shear stress is the average value of the shear stress calculated by multiplying the shear rate by the viscosity, for example. The slurry distance is the distance of one rotation of the first screw 6a. Thus, the cumulative energy value is calculated by multiplying the calculated shear rate by the viscosity of the paste, and then multiplying this multiplicative value by the distance covered when the first screw 6a is rotated once. The lower the cumulative energy value, the lower the shear force applied to the material.

[0043] As shown in the figure, the cumulative energy value is 284 [N / m] for a conventional screw, while it is 184 [N / m] for the second screw section 23. Thus, in the case of the second screw section 23 in this example, the cumulative energy value can be reduced by approximately -35% compared to a conventional screw. Therefore, from this point of view as well, it can be seen that excessive shear force is not applied to the material from the second screw section 23.

[0044] As shown in Figure 8, a paste of the anode material is manufactured using the actual kneader 1, and the blackness of this paste is evaluated. The kneader 1 used for the actual evaluation is a batch-type twin-screw kneader. The solid components of the paste composition used for the actual evaluation are, for example, 98.0 wt% active material, 1.0% thickener, and 1.0% binder. The solvent of the paste composition used for the actual evaluation is, for example, water. The solid fraction of the paste composition is, for example, 60% solid and 40% solvent. The rotation speed of the kneading shaft 3 is, for example, 800 rpm.

[0045] In Figure 8, the blackness ratio of the paste produced using the second screw section 23 of this example is shown, when the blackness of paste produced using a conventional screw is normalized to "1". Incidentally, blackness shows a high value when the shear force is too high due to damage to the active material, and a low value when the shear force is appropriate because damage to the active material is suppressed. Therefore, if the blackness is kept lower than that of paste produced using a conventional screw, it can be considered that the shear force has been kept low.

[0046] In this example, as shown in Figure 8, the paste produced using the second screw section 23 showed a significant decrease in blackness compared to the paste produced using the conventional screw. The decrease in blackness was, for example, about -65%. This is presumed to be because the peeling of the amorphous coating layer on the surface of the negative electrode active material was significantly suppressed. Therefore, this indicator also shows that the shear force applied to the material was kept low.

[0047] (Effects of the first embodiment) According to the configuration of this embodiment, the following effects can be obtained. (1.1) The kneader 1 comprises a barrel 2 into which the electrode material for the battery is fed, a pair of screws 6 that rotate in the same direction to transport the electrode material inside the barrel 2, and a pair of paddles 7 that are provided to rotate integrally with each of the pair of screws 6 and shear the electrode material during the transport process. The barrel 2 has a powder inlet 11 located upstream of the paddles 7 into which the powder of the electrode material is fed, and a solvent inlet 12 located between the paddles 7 and the powder inlet 11 in the transport path of the electrode material into which the solvent for the electrode material is fed. The screw 6 has a first screw section 22 located opposite the powder inlet 11, and a second screw section 23 located opposite the solvent inlet 12 and formed in a shape that has a lower shear force than the first screw section 22.

[0048] In this configuration, when powder is introduced into barrel 2 from the powder inlet 11 and solvent from the solvent inlet 12, the portion of screw 6 facing the powder inlet 11 and solvent inlet 12 will contain material in a highly viscous state, or so-called wet state, during the initial mixing stage. If high shear force is applied from screw 6 to highly viscous material, it can cause damage to the material. In this configuration, the second screw portion 23 facing the solvent inlet 12 is formed with a shape that has a lower shear force than the first screw portion 22 facing the powder inlet 11. Therefore, when mixing the powder and solvent, they are agitated by the second screw portion 23 with a lower shear force, so even if the powder and solvent are in a highly viscous state during the initial mixing stage, high shear force is not applied to the material. Thus, it is possible to reduce the likelihood of damage to the material when agitating the powder and solvent with screw 6.

[0049] (1·2) The electrode material is the material of the negative electrode plate of the battery. The powder contains the active material and the thickener of the negative electrode plate. According to this configuration, since a high shearing force is not applied from the screw 6 to the material of the negative electrode plate in which the powder and the solvent are mixed, the peeling of the amorphous coat layer existing on the surface of the negative active material can be suppressed.

[0050] (1·3) The second clearance W2, which is the clearance between the inner wall of the barrel 2 and the second screw part 23 facing the solvent inlet 12, is within the range of the first clearance W1, which is the clearance between the inner wall of the barrel 2 and the first screw part 22 facing the powder inlet 11, and the third clearance W3, which is the clearance between the inner wall of the barrel 2 and the paddle 7 (the relationship of W1 < W2 < W3). According to this configuration, in the barrel 2, the first screw part 22, and the second screw part 23, by means of a simple structure of changing the clearance with respect to the inner wall of the barrel 2, a high shearing force can be prevented from being applied to the wet material in which the powder and the solvent are mixed.

[0051] (1·4) The first screw part 22 and the second screw part 23 are arranged coaxially. The second clearance W2 is formed larger than the first clearance W1 by forming the diameter of the second screw part 23 smaller than the diameter of the first screw part 22. According to this configuration, the second screw part 23 only needs to have a shape with a different diameter from the first screw part 22. Therefore, when changing each of the first clearance W1 of the first screw part 22 and the second clearance W2 of the second screw part 23 with respect to the inner wall of the barrel | tube 2, the structure of the screw 6 does not become complicated. <>

[0052] (Second Embodiment) Next, the second embodiment will be described. The second embodiment is an example in which the shape of the second screw part 23 described in the first embodiment is changed. Therefore, the same reference numerals are given to the same parts as those in the first embodiment and the description thereof is omitted, and only the different parts will be described in detail.

[0053] (Specific Mention of Screw Shape) As shown in Figure 9, the first screw section 22 and the second screw section 23 are set to have different shear forces generated in the first screw section 22 and the second screw section 23 by setting the helix angle θ, which is the angle that the blade 16 makes with respect to the screw axis, to different values. In this example, if the helix angle θ of the blade 16 of the first screw section 22 is set to be the first helix angle θ1, and the helix angle θ of the blade 16 of the second screw section 23 is set to be the second helix angle θ2, then the second helix angle θ2 is set to be smaller than the first helix angle θ1 and to be at least half the value of the first helix angle θ1.

[0054] As shown in Figure 10, conventional screws have a screw twist of 240 degrees for a given screw width Wt. On the other hand, the second screw portion 23 of this example has a screw twist of 120 degrees for a given screw width Wt. Thus, the second screw portion 23 of this example is formed in a shape that results in a gentler screw twist angle.

[0055] (Operation of the second embodiment) Let's assume that the shear rate was simulated at the calculation point Pa shown in Figure 10. In this example, the distance between the blades 16 of the second screw section 23 and the inner wall of the barrel 2 is the same as the distance between the blades 16 of a conventional screw and the inner wall of the barrel 2. Therefore, the shear rate generated by the second screw section 23 in this example is no different from the shear rate generated by a conventional screw. Thus, the effect of reducing shear force cannot be obtained from the shear rate as an indicator.

[0056] Figure 11 shows the integrated energy value [N / m] applied to the slurry at calculation point Pa when the first screw 6a is rotated once. The integrated energy value is 284 [N / m] for a conventional screw, while it is 220 [N / m] for the second screw section 23. Thus, in the case of the second screw section 23 in this example, the effect of reducing the integrated energy value by about -23% compared to a conventional screw is obtained. Therefore, from this point as well, it can be seen that excessive shear force is not applied to the material from the second screw section 23.

[0057] Figure 12 shows the evaluation results of the blackness of the paste of the negative electrode material produced using the second screw part 23 of this example. In the case of the paste produced using the second screw part 23 of this example, the blackness reduction rate is about -39% compared to the paste produced using the conventional screw, indicating that the blackness has decreased. This is presumably because the peeling of the amorphous coating layer on the surface of the negative electrode active material could be suppressed. Therefore, it can be seen from this point that the shearing force applied to the material is kept low.

[0058] (Effect of the Second Embodiment) According to the configuration of the above embodiment, in addition to the effects described in the second embodiment, the following effects can be obtained.

[0059] (2·1) The second twist angle θ2, which is the twist angle θ of the blade 16 of the second screw part 23 facing the solvent inlet 12, is smaller than the first twist angle θ1, which is the twist angle θ of the blade 16 of the first screw part 22 facing the powder inlet 11, and is set to a value of 1 / 2 or more of the first twist angle θ1. According to this configuration, by means of a simple structure that changes the first twist angle θ1 of the blade 16 of the first screw part 22 and the second twist angle θ of the blade 16 of the second screw part 23, a high shearing force can be prevented from being applied to the wet material in which the powder and the solvent are mixed.

[0060] (Other Embodiments) Note that this embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically non - conflicting range.

[0061] ·In each embodiment, each of the first clearance W1, the second clearance W2, and the third clearance W3 may be changed step - by - step or continuously as long as the relationship of "W1 < W2 < W3" is satisfied.

[0062] ·In each embodiment, the powder introduced into the powder inlet 11 may be only the powder of the active material. In each embodiment, the powder other than the active material introduced into the powder inlet 11 is not limited to a thickener, but may be other materials.

[0063] In each embodiment, the number of screws 6 and paddles 7 on the kneading shaft 3 may be changed to a number other than those in the embodiment. In each embodiment, the paddle 7 may be configured to have only a wet paddle.

[0064] In each embodiment, multiple powder inlet 11s and solvent inlet 12s may be provided. In each embodiment, the rotational speed of the mixing shaft 3 (screw 6) may be faster than in the conventional model.

[0065] In each embodiment, the electrode material to be kneaded is not limited to a paste for the negative electrode of a lithium-ion secondary battery, but may also be a paste for the positive electrode of a lithium-ion secondary battery. In each embodiment, the secondary battery is not limited to a lithium-ion secondary battery, but may be other types of batteries, such as a nickel-metal hydride secondary battery.

[0066] In each embodiment, the battery is not limited to being a sealed battery with a rectangular parallelepiped shape, but may also have 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 electric vehicles or hybrid vehicles, but may also be installed in vehicles such as gasoline vehicles or diesel vehicles. Furthermore, the secondary battery may be used as a power source for mobile vehicles such as trains, ships, aircraft, and robots, or for electrical products such as information processing devices.

[0067] • In each embodiment, the Disclosure has been described in accordance with the examples, but is not limited to the structures of these embodiments and includes various modifications and variations within the equivalence range. The Disclosure also includes various combinations and forms, as well as combinations and forms of one, more, or fewer of these elements. [Explanation of Symbols]

[0068] 1... Mixer, 2... Barrel, 6... Screw, 7... Paddle, 11... Powder inlet, 12... Solvent inlet, 16... Blade, 22... First screw section, 23... Second screw section, W1... First clearance, W2... Second clearance, W3... Third clearance, θ... Helix angle, θ1... First helix angle, θ2... Second helix angle.

Claims

1. A kneader comprising: a barrel into which battery electrode material is fed; a pair of screws that rotate in the same direction to transport the electrode material inside the barrel; and a pair of paddles that are rotatably mounted integrally with each of the pair of screws to shear the electrode material during the transport process, The barrel has a powder inlet located upstream of the paddle into which the powder of the electrode material is introduced, and a solvent inlet located between the paddle and the powder inlet in the transport path of the electrode material into which the solvent of the electrode material is introduced. The kneader comprises a screw having a first screw portion positioned opposite the powder inlet and a second screw portion positioned opposite the solvent inlet and formed in a shape that reduces the shear force compared to the first screw portion.

2. The electrode material is the material for the negative electrode plate of the battery, The kneader according to claim 1, wherein the powder comprises the active material of the negative electrode plate and a thickening agent.

3. The kneader according to claim 1, wherein the clearance between the inner wall of the barrel and the first screw portion facing the powder inlet is defined as the first clearance, the clearance between the inner wall of the barrel and the second screw portion facing the solvent inlet is defined as the second clearance, and the clearance between the inner wall of the barrel and the paddle is defined as the third clearance, the second clearance is set to a value within the range of the first clearance and the third clearance.

4. The first screw portion and the second screw portion are arranged coaxially. The kneader according to claim 3, wherein the second clearance is formed to be larger than the first clearance by forming the diameter of the second screw portion to be smaller than the diameter of the first screw portion.

5. The kneader according to claim 1, wherein when the twist angle of the blades of the first screw portion facing the powder inlet is defined as the first twist angle, and the twist angle of the blades of the second screw portion facing the solvent inlet is defined as the second twist angle, the second twist angle is set to be smaller than the first twist angle and to be at least half the value of the first twist angle.

6. A kneading method comprising conveying electrode material for a battery placed inside a barrel using a pair of screws rotating in the same direction, and shearing the electrode material during the conveying process using a pair of paddles that are rotatably mounted integrally with each of the screws, A step of introducing the electrode material powder from a powder inlet provided in the barrel so as to be located upstream of the paddle, A step of introducing the solvent for the electrode material from a solvent inlet provided in the barrel so as to be positioned between the paddle and the powder inlet in the transport path of the electrode material, A kneading method comprising the steps of using a screw having a first screw portion positioned opposite to the powder inlet and a second screw portion positioned opposite to the solvent inlet and formed in a shape with lower shear force than the first screw portion to stir the powder and the solvent and convey them to the paddle.

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