Method for producing slurry, and kneading system

Abstract

This method for producing a slurry comprises a premixing step, a kneading step, and a dilution step. The kneading step comprises a solution adjustment step in which a mixture is kneaded while a binder fluid is added and, subsequently to the solution adjustment step, a final kneading step in which the mixture is kneaded without the addition of the binder fluid. In the solution adjustment step, the amount of the binder fluid that has been added and a torque being applied to the mixture are measured, and the total addition amount of the binder fluid is determined on the basis of changes (dF / dV) in torque F with respect to the addition amount V of the binder fluid. Thereafter, the final kneading step is performed in which the mixture is kneaded without the addition of the binder fluid.

Description

Slurry manufacturing method and mixing system

[0001] This invention relates to a method for producing a slurry and a mixing system.

[0002] Techniques for producing slurries used in coatings and the like are known. For example, in the manufacturing method disclosed in Patent Document 1, the amount of solvent introduced into the solid mixing process is adjusted based on the noise level of the mixing mixer when the active material, binder, and solvent are mixed together.

[0003] Japanese Patent Publication No. 2012-150923

[0004] According to the manufacturing method described in Patent Document 1, the noise during mixing is measured, and the amount of solvent added is adjusted based on the measured noise level. However, when the powder being mixed changes, the noise peak fluctuates, making it impossible to determine the amount to add in real time, and requiring further prior verification. For example, even with powders of the same specifications, simply changing the manufacturing lot can alter the noise characteristics and cause significant fluctuations in the mixing state. As a result, it becomes impossible to supply the appropriate amount of solvent, leading to a decrease in the quality of the manufactured slurry. Furthermore, adjusting the noise characteristics for each lot requires a long lead time each time a lot is switched. Similar problems occur when adding other liquids, such as binders, to the powder during mixing. In particular, with mixed slurries, controlling the quality of the material powder is difficult, making stable, high-quality mixing even more challenging.

[0005] This invention has been made in view of the above circumstances, and aims to provide a slurry manufacturing method that allows for the appropriate determination of the amount and timing of additive addition, and a kneading system for producing a high-quality slurry.

[0006] To achieve the above objective, the slurry manufacturing method according to the present invention comprises a pre-mixing step, a kneading step, and a dilution step. The kneading step includes a solution preparation step in which the mixture is kneaded while adding a binder, and a main kneading step that follows the solution preparation step in which the mixture is kneaded without adding a binder. In the solution preparation step, the amount of binder to be added (V) and the torque applied to the mixture for mixing are measured, and the total amount of binder to be added is determined based on the change in torque (F) (dF / dV) with respect to the amount of binder added (V), after which the main kneading step is performed in which the mixture is kneaded without adding a binder.

[0007] According to the present invention, in the solution preparation step, the amount of binding solution to be added and the torque of the kneading mixer are measured, and the amount of binding solution is determined according to the change in torque relative to the amount of binding solution. This makes it possible to quickly and appropriately determine the amount of solvent to be added.

[0008] This figure illustrates a positive electrode slurry manufacturing process according to an embodiment of the present invention. Figures (a) to (d) show the water content of the powder, the mixed state, the state of the powder and liquid, a simulated state of the powder and liquid, and the torque curve when kneading them. This figure illustrates the torque curve shown in Figure 2(d). This figure shows examples of the actual torque curve of the mixer with respect to the amount of liquid added, and its first and second derivative curves. This is a block diagram of the kneading system according to an embodiment of the present invention. This is a flowchart of the kneading control process performed by the control device of the kneading system shown in Figure 5. This figure illustrates the time change of the torque of the mixer's stirring blades after the addition of the binding liquid. This figure illustrates how an embodiment of the present invention makes it possible to appropriately manufacture slurries of various materials and applications, such as positive electrode materials, SE materials, and negative electrode materials for all-solid-state batteries.

[0009] The slurry manufacturing method and manufacturing system according to embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals.

[0010] The slurry manufacturing method and mixing system according to an embodiment of the present invention will be described using the example of its application to the production of a slurry used for the positive electrode of an all-solid-state battery.

[0011] The slurry manufacturing method according to this embodiment includes a pre-mixing step P10, a kneading step P20, and a dilution (dilution and dispersion) step P30, as shown in Figure 1.

[0012] The pre-mixing step P10 is a step in which a powdered active material, which is an example of a material powder (hereinafter referred to as powder), a solid electrolyte, and a conductive additive are mixed dry.

[0013] The kneading step P20 is a process in which a binding solution is added to the mixture produced in the pre-mixing step P10, and the mixture, which has solidified into a ball-like mass with a high solid content, is kneaded. The binding solution is a liquid containing at least a solvent, and in addition to the solvent, a binder may also be included. Furthermore, it may contain any or all of the materials that constitute the electrode, such as the binder, active material, and conductive additive. The kneading step P20 applies a high shear force to the powder, promoting its dispersion. In order to apply an appropriate shear force to the powder, it is important to add an appropriate amount of binding solution and perform solid kneading. To achieve this, the kneading step P20 includes multiple solution preparation steps P21 and one main kneading step P22. The solution preparation step P21 is a process in which the appropriate amount of binding solution to be added is determined according to the state of the mixture, the determined amount of binding solution is added to the mixture, and kneading is performed. The main kneading step P22 is a solid kneading step in which the mixture is kneaded without the addition of additional binding solution. Details of the kneading step P20 will be described later.

[0014] The dilution step P30 is a step in which a binding solution and a solvent are added to the mixture produced in the kneading step P20, and the mixture is dispersed using a dispersion device or the like to obtain a positive electrode slurry.

[0015] As shown in the diagram, the raw materials for the positive electrode slurry are, for example, a positive electrode active material, a solid electrolyte, and a conductive additive.

[0016] The positive electrode active material is a substance that contributes to the reaction that generates electricity, for example, LiCoO ２ Li-Co composite oxides such as LiNiO ２ Li-Ni composite oxides such as spinel LiMn ２ O ４ Li-Mn composite oxides such as LiFeO ２Examples include Li-Fe composite oxides, but this is not limited to these.

[0017] Solid electrolytes are solid electrolytes with high ionic conductivity, and various types such as sulfide-based and oxide-based electrolytes can be selected and used.

[0018] Conductive additives are substances that enhance the conduction of electrons, such as acetylene black, carbon black, and graphite.

[0019] Furthermore, it is desirable that the binding solution added in the kneading process P20 includes a binder. The binder is a substance that binds the active material and conductive additive together, and examples include polyvinylidene fluoride (PVdF) and styrene-butadiene rubber.

[0020] The solvent is a liquid used to dissolve binders and conductive additives to create a solution. As solvents, for example, aprotic organic solvents such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide can be used alone or in combination of two or more.

[0021] Next, we will examine the changes in the mixing state of the powder and liquid during the slurry manufacturing process, referring to Figure 2. We will assume that the powder is stirred using a mixer or similar device while the liquid is added to it.

[0022] In this case, as shown in Figure 2(a), the mixing state changes sequentially to the following mixing states as the amount of liquid contained increases: Dry, Pendular, Funicular I, II, Capillary, and Slurry.

[0023] As the mixing state changes, the state of the powder and liquid sequentially changes from Aggrigate, PL (plastic limit), Closest Pack, Liq.L (liquid limit), to Flocculate (soft agglomeration), as shown in Figure 2(b).

[0024] Also, as schematically shown in Fig. 2(c), the relationship between the powder and the liquid in each mixing state changes sequentially from the state of only the particles indicated by white circles, to the state where the particles are most densely packed in the liquid represented by black and the liquid fills the inter-particle gaps, and to the state where the particles float and disperse in the liquid.

[0025] As shown in Fig. 2(d), the torque applied to the mixer increases as the amount of liquid increases from the state of dry granules. The torque reaches its maximum value in the state where the particles are most densely packed and the liquid fills the inter-particle gaps, i.e., the Closest Pack state. At this time, the mixture becomes in a state like a shiny dumpling. Then, by further adding liquid, the powder floats in a liquid state to form a slurry, so the torque decreases.

[0026] Since the maximum torque value, the amount of liquid, etc. change depending on the powder, it is difficult to determine the optimal addition amount of the liquid with a fixed threshold value.

[0027] On the other hand, regardless of the types of the powder and the liquid, the liquid volume - torque curve shape shows relatively similar characteristics. Therefore, by monitoring the torque value F, it is possible to specify which mixing state the mixture is in at that time. Therefore, by monitoring the torque value F, it becomes possible to specify the optimal addition amount in real time.

[0028] Analyze this point further. Fig. 3 is a diagram showing the relationship between the liquid volume V and the torque value F when the change in the liquid volume - torque value F shown in Fig. 2(d) is regarded as a Gaussian distribution. Further, the first derivative and the second derivative of the V - F relationship with respect to V are shown superimposed.

[0029] As shown in the figure, the liquid-containing state of the powder can be classified into the following four states from the torque value F of the mixer. i) With a small amount of liquid, (d ２ F ｎ / dV ｎ ２ ) > 0 and (d ２ F ｎ / dV ｎ ２ ) > (d ２ F n-１ / dV n-１ ２) the first state, ii) liquid is filling the particle space, (d ２ F ｎ / dV ｎ ２ ) > 0 and (d ２ F ｎ / dV ｎ ２ ) < (d ２ F n-１ / dV n-１ ２ ) the second state, iii) the particles are packed in the tightest possible space, the gaps between the particles are filled with liquid, and the torque is at its maximum, (d ２ F ｎ / dV ｎ ２ ) < 0, the third state, iv) the powder is suspended in the liquid, and the torque decreases, (dF ｎ / dV ｎ The fourth state is when ) ≤ 0. Note that n indicates the timing.

[0030] As shown in Figure 4, while adding liquid, the amount of liquid added V, the torque value F, its first derivative, and its second derivative are monitored. i) When it is detected that the mixture is in the first state, a first addition step is performed in which a relatively large amount of first addition Va, suitable for the first state, is added while kneading. ii) When it is detected that the mixture is in the second state, a second addition step is performed in which a second addition amount Vb, less than the first addition amount Va, is added while kneading. iii) When it is detected that the mixture is in the third state, a third addition step is performed in which a third addition amount Vc, less than the second addition amount Vb, is added while kneading. iv) When it is detected that the mixture is in the fourth state, solid kneading is continued without adding any liquid, thereby enabling proper kneading.

[0031] Next, with reference to Figure 5, a kneading system 1 for carrying out the slurry manufacturing method according to this embodiment will be described. The kneading system 1 is a system that performs the kneading step P20 of the slurry manufacturing method shown in Figure 1. However, the pre-mixing step P10 and the dilution step P30 may also be carried out by the kneading system 1.

[0032] As shown in Figure 5, the kneading system 1 includes a kneading device 2 which includes a kneading tank 21 used for kneading powder and binding liquid, and a kneading mixer 22 equipped with stirring blades 25, a measuring device 3 which measures the torque value F applied to the stirring blades 25, an adding device 4 which puts the binding liquid into the kneading tank 21, and a control device 5 which determines the amount of binding liquid to be added (amount added) to the kneading tank 21 and controls the adding device 4. The control device 5, the kneading device 2, the measuring device 3, and the adding device 4 are connected in a communication manner.

[0033] The kneading device 2 kneads the active material with the binder solution. The kneading tank 21 is a tank into which the mixture generated in the pre-mixing step P10 is introduced, and which can also contain the binder solution supplied from the additive device 4.

[0034] The mixing mixer 22 includes a rotating shaft 24, a stirring blade 25 provided at the tip of the rotating shaft 24, a motor 26 that rotates the rotating shaft 24, and a driver 27 that drives the motor 26. The driver 27 controls the on / off rotation of the motor 26, the rotation speed, etc., according to control commands from the control device 5. The motor 26 consumes power supplied by the driver 27 to rotate the rotating shaft 24 as shown by arrow A. As the rotating shaft 24 rotates, the stirring blade 25 rotates, kneading the mixture of powder and binder liquid in a high solid content state. The mixing mixer 22 is an example of a mixing means for kneading a mixture, and any mixing means of any structure can be used as long as it can knead the mixture by adding a binder liquid.

[0035] The measuring device 3 determines the torque value F applied to the stirring blade 25 by observing the rotation of the stirring blade 25. There is an almost linear relationship between the torque value F and the drive current flowing through the armature of the motor 26 and the power consumed by the motor 26. For this reason, in this embodiment, the current flowing through the motor 26 is measured with an ammeter, or the power consumption is measured with a wattmeter, and the measured value is used as a substitute for the torque value F. Alternatively, the torque applied to the stirring blade 25 itself may be measured with a torque meter. The measuring device 3 measures the drive current of the motor 26 at predetermined time intervals and periodically sends the measured values ​​to the control device 5.

[0036] The additive device 4 responds to commands from the control device 5 and, at the commanded timing, adds the instructed amount of binding liquid to the kneading tank 21.

[0037] The control device 5 controls the driver 27 to rotate the stirring blade 25, and at the same time, it determines the amount of binding liquid to be introduced into the kneading tank 21 according to the torque value (current value) F measured by the measuring device 3, and sends a liquid delivery command to the addition device 4 to control the addition of the binding liquid.

[0038] The control device 5 is, in terms of hardware, a computer comprising a processing unit 51 that executes the slurry manufacturing control process described later, a storage unit 52 that stores the control program executed by the processing unit 51, the numerical values ​​obtained by the processing unit 51, and a communication unit 53 that sends and receives information between the measuring device 3, the additive device 4, and the driver 27.

[0039] The processing unit 51 consists of a processor and executes a control program stored in the memory unit 52, and performs the kneading control process described later with reference to Figure 6. More specifically, as shown in Figure 4, each time a binding liquid is added to the kneading tank 21, the processing unit 51 calculates the change in torque ΔF with respect to the amount of liquid added ΔV, i.e., ΔF / ΔV. This corresponds to the first derivative of the relationship between the total amount of binding liquid added V and the torque value F with respect to V (dF / dV). The processing unit 51 further calculates the derivative of the differential curve dF / dV, i.e., the second derivative of the V-F curve d ２ F / dV ２ The processing unit 51 then calculates the change in torque value F with respect to the amount of added liquid ΔV. This corresponds to the first derivative of the relationship between the amount of added processing liquid V and the torque value F with respect to V (dF / dV). Furthermore, the processing unit 51 calculates the second derivative of the V-F curve with respect to V (d ２ F / dV ２ The processing unit 51 determines which of the first to fourth addition steps shown in Figure 4 these values ​​belong to, adjusts the amount added according to the determined step, and instructs the addition device 4 on the amount of solvent to add.

[0040] The communication unit 53 receives the current value F etc. measured by the measuring device 3 and transmits an instruction to the additive device 4 regarding the amount of bonding solution to be added.

[0041] Next, with reference to Figure 6, we will explain the slurry manufacturing method performed by the slurry manufacturing system shown in Figure 5.

[0042] First, the electrode material is dry-mixed in a pre-mixing step P10 using any mixing system. A kneading system 1 may be used for pre-mixing. The electrode material includes, as described above, an active material, a solid electrolyte, and a conductive additive.

[0043] The resulting mixed slurry is put into the kneading tank 21. Next, in order to start the kneading process P20, the control device 5 starts the kneading control process shown in Figure 6.

[0044] The processing unit 51 first sets the index value n, which indicates the number of stages of development of the binding solution, to 0 (step S101). The processing unit 51 sends a command to the addition device 4 to add the binding solution to the kneading tank 21 (step S102). Specifically, the processing unit 51 sends a command to the addition device 4 via the communication unit 53 to add an initial addition amount ΔVn = V0 based on the setting data of the storage unit 52. The initial addition amount V0 is preferably an amount that can bring the mixture into a pendula-like state. For example, it is preferably about 5% to 20% of the average oil absorption of the mixture. The average oil absorption can be measured by a method conforming to JIS K5101-13-1, for example. The initial addition amount V0 may be determined in advance by experimentation or other means. The reason for setting the initial addition amount V0 to such an amount is that if the initial addition amount V0 is too small, there is a risk that it will take too long to add the required amount of binding solution and knead it. The additive device 4, in response to the command, adds the instructed initial amount V0 of the binding solution to the kneading tank 21 and notifies the control device 5 that the addition is complete.

[0045] After the binding solution has been added, the processing unit 51 sends a command to the driver 27, drives the motor 26 at a predetermined rotational speed, and rotates the stirring blade 25 via the rotating shaft 24 at a rotational speed R1 [rounds / min] to start kneading (step S103). It is desirable that the rotational speed R1 is smaller than the rotational speed R2 of the stirring blade 25 in the kneading step P22 in order to suppress over-kneading. The step of adding the binding solution in an initial addition amount V0 and performing kneading is an example of the initial addition step.

[0046] The processing unit 51 determines whether a predetermined time Th has elapsed (step S103). Here, the predetermined time Th is, for example, the time required for the power value F to reach a steady state, which is determined by experimentation or the like and stored in the storage unit 52.

[0047] The method for determining this predetermined time Th will now be explained. When a motor is rotated at a constant speed and the mixture is kneaded by the stirring blades, the current flowing through the motor peaks immediately after the addition of the binding liquid, as shown in Figure 7, and then gradually decreases until it reaches a steady state after a certain period of time. The time required to reach a steady state varies depending on the material and amount of the mixture and binding liquid. For this reason, it is desirable to set the predetermined time Th to be longer than the time required for the current flowing through the motor 26 to reach a steady state after the addition of the binding liquid. Generally, the predetermined time Th is set to about 5 minutes, for example, 4 to 7 minutes. Alternatively, instead of pre-setting a reference time Th, it is also possible to monitor the drive current of the motor 26, determine whether the drive current has reached a steady state, and determine that the predetermined time Th has elapsed when it is determined that it has. For example, it is also possible to configure the system to determine that the predetermined time Th has elapsed when the absolute value of the change in the torque value F of the motor 26 (time derivative) remains below a reference value for a reference time or longer.

[0048] If it is determined in step S104 that the predetermined time Th has not elapsed (step S104: No), the process in step S104 is repeated, and the system waits for the predetermined time Th to elapse.

[0049] If it is determined that a predetermined time Th has elapsed (Step S104: Yes), the torque value F of the motor 26 is obtained from the measuring device 3 (Step S105). At this stage, the powder is almost uniformly wetted by the binding liquid, the state of the mixture is uniform, the torque value F is stable, and the error in the acquired data is considered to be small. For this reason, the torque value F of the motor 26 is obtained at this point.

[0050] Furthermore, the processing unit 51 stops the operation of the kneading mixer 22 and performs a calculation process (step S106). Specifically, it calculates the total amount V of the added binding liquid by accumulating the amount of liquid already added. Furthermore, as illustrated in Figure 4, the measured torque value F is plotted on the V-F curve. Furthermore, the previously measured torque value F n-１ And the torque value F measured this time n The difference ΔF n Plot the first derivative curve. Then, differentiate the first derivative curve once and obtain the second derivative value d. ２ F / dV ２ The processing unit 51 calculates the values. The processing unit 51 stores each calculated value in the storage unit 52. For ease of understanding, an example is shown in which the calculated values ​​are plotted on a curve, but if data can be obtained, processing such as blotting can be omitted.

[0051] The processing unit 51 is dF ｎ / dV ｎ It is determined whether or not the value is 0 (zero) or less, that is, whether or not it is in the proper mixing state (step S107). dF ｎ / dV ｎ If it is determined that the value is not 0 or less (Step S107: No), the process proceeds to Step S108 to determine which of the first to third addition steps the process is in.

[0052] The processing unit 51 is (d ２ F ｎ / dV ｎ ２ ) is greater than 0, and (d ２ F ｎ / dV ｎ ２ ) is (d ２ F n-１ / dV n-１ ２ (d ２ F ｎ / dV ｎ ２ ) is greater than 0, and (d ２ F ｎ / dV ｎ ２ ) is (d ２ F n-１ / dV n-１２ If it is determined that it is larger than )(step S108: Yes), the manufacturing process is considered to be in the first addition step. In this case, the processing unit 51 sets n = n + 1, and sets the addition amount ΔV ｎ of the next binder liquid to Va, which is a value smaller than the first addition amount V0 (step S109). Then, the process returns to step S102. In step S102, the first addition amount Va is added, and kneading is performed in step S103. The step of adding the binder liquid of the first addition amount Va and performing kneading is an example of the first addition step.

[0053] If it is determined as No in the determination process of step S108, the process proceeds to step S110.

[0054] The processing unit 51 determines whether (d ２ F ｎ / dV ｎ ２ )is greater than 0 and (d ２ F ｎ / dV ｎ ２ )is smaller than (d ２ F n-１ / dV n-１ ２ )(step S110). If (d ２ F ｎ / dV ｎ ２ )is greater than 0 and (d ２ F ｎ / dV ｎ ２ )is smaller than (d ２ F n-１ / dV n-１ ２ )(step S110: Yes), the manufacturing process is considered to be in the second addition step. In this case, the processing unit 51 sets n = n + 1, and sets the addition amount ΔV ｎThe second addition amount Vb is set to be smaller than the first addition amount Va set in step S109 (step S111). This is because the second addition step is closer to the point of maximum torque than the first addition step, and this prevents over-addition. The process then returns to step S102, where the second addition amount Vb is added, and kneading is performed in step S103. The process of adding the binding solution in the second addition amount Vb and kneading is an example of the second addition step.

[0055] In the determination process of step S110, if it is determined to be No, the manufacturing process is considered to be in the third addition step. In this case, the processing unit 51 sets n = n + 1 and adds the next amount ΔV. ｎ The second amount added, V ｂ A smaller third addition amount V ｃ This is set (step S112). This is because the third addition step is closer to the point of maximum torque than the second addition step, and this prevents over-addition. The process then returns to step S102, where the third addition amount Vc is added, and kneading is performed in step S103. The step of adding the binding solution in the third addition amount Vc and kneading is an example of the third addition step.

[0056] If the result in step S107 is determined to be Yes, i.e., dF ｎ / dV ｎ If it is determined that the value is 0 (zero) or less, the state of the mixture is in the optimal solid-knead range, and the manufacturing process is considered to have passed the stage of adding the binding solution and is in the main kneading stage. Therefore, the processing unit 51 operates the kneading mixer 22 and performs the main kneading without adding any additional binding solution (step S113). In the main kneading, it is desirable that the rotation speed R2 of the stirring blade 25 is greater than the rotation speed R1 of the stirring blade 25 for kneading in the solution preparation step P21.

[0057] In this kneading process S113 (P22), the initial torque tends to increase as the binding liquid blends with the powder, but the torque decreases due to a reduction in binding force caused by the rupture of binder molecules. To suppress excessive kneading, the kneading process is terminated when the kneading time or the cumulative value of the power consumption of the motor 26 exceeds a reference value. The reference value is determined in advance through experiments and stored in the memory unit 52. After the kneading execution time has elapsed, the process is terminated.

[0058] The slurry obtained in this way is transferred to another mixer, and a dilution step P30 is performed by adding a binder and solvent and kneading the mixture. This yields a positive electrode slurry. Alternatively, the dilution step P30 may be performed using the kneading system 1.

[0059] In the above embodiment, the present invention was explained using the case of producing a positive electrode slurry for an all-solid-state battery as an example. However, the present invention is not limited to this embodiment. The present invention can be widely used, for example, in the manufacture of slurry for positive electrode material, slurry for SE layer material, slurry for negative electrode material, and other slurries for all-solid-state batteries, as well as in the mixing of these materials, as schematically shown in Figure 8.

[0060] Furthermore, the methods for obtaining the V-F curve, its first derivative curve, and its second derivative curve are not limited to the methods shown in Figure 6. Any known data processing method can be used.

[0061] As described above, the slurry manufacturing method according to this embodiment comprises a pre-mixing step P10 in which material powders such as positive electrode active material, solid electrolyte, conductive additive, negative electrode active material, negative electrode material, and SE layer material are mixed dry; a kneading step P20 in which a binding solution containing, for example, a binder and a solvent is added to the mixture produced in the pre-mixing step P10 and kneaded in a high solid content state; and a dilution step P30 in which the kneaded product produced in the kneading step P20 is diluted with the binding solution to obtain a slurry.

[0062] The kneading step P20 includes a solution preparation step P21 in which the mixture is kneaded while adding a binding solution, and a main kneading step P22, for example, which follows multiple solution preparation steps and kneads the mixture without adding a binding solution.

[0063] In the solution preparation step P21, the amount V of the binding solution to be added and the torque value F applied to the mixture by the stirring blades 25 of the kneading mixer 22 for mixing are measured. Based on the change in torque value F with respect to the amount of binding solution added V (dF / dV), for example, when dF / dV = 0, the addition of the binding solution is stopped to determine and confirm the total amount of binding solution added V. After that, the main kneading step is carried out, in which the mixture is kneaded without adding the binding solution.

[0064] With this configuration, for example, the addition of the binding solution can be stopped when the change in the torque value F of the mixing mixer 22 (dF / dV) becomes zero, allowing for precise determination of the liquid volume. This makes it possible to perform solid mixing when the material powder is subjected to the maximum torque, resulting in a high-quality slurry. Furthermore, it becomes possible to accurately determine the amount of binding solution to be added in real time without having to perform prior verification due to deviations in the correlation formula or changes in thresholds caused by changes in the physical properties of the material powder, such as when changing manufacturing lots. As a result, it becomes possible to stably produce a high-quality slurry without lumps.

[0065] Furthermore, in this embodiment, the solution preparation step P21 comprises an initial addition step, a first addition step, a second addition step, and a third addition step.

[0066] In the initial addition step, the binder solution is added in an initial amount V0 and kneaded so that the mixture of material powders generated in the pre-mixing step P10 reaches a pendula-like state. In the first addition step, the second derivative d of the torque value F due to the total amount V of binder solution added is calculated. ２ F / dV ２ The value is greater than 0, and the second derivative d of the torque value F obtained by the previous addition of the bonding solution is also greater than 0. ２ F / dV ２ If the amount is greater, a first addition amount Va of the binder solution, which is less than or equal to the initial addition amount V0, is added and kneaded. In addition, the second addition step and the second derivative d of the torque value F due to the total amount V of the binder solution added are performed. ２ F / dV ２ The value is greater than 0, and the second derivative d of the torque value F obtained by the previous addition of the bonding solution is also greater than 0. ２ F / dV ２If the amount is smaller, a second amount Vb of the binder solution, which is less than the first amount Va, is added and kneaded. In the third addition step, the second derivative d of the torque value F due to the total amount V of the binder solution added is calculated. ２ F / dV ２ If the value is 0 or less, a third amount of binder solution, Vc, which is less than the second amount Vb, is added and kneaded. In this kneading process, after the third addition process, when the first derivative of the torque value F due to the total amount of binder solution V falls within the reference range, the addition of the binder solution is stopped and kneading is continued.

[0067] According to this mixing method, the amount of liquid to be added is d ２ F / dV ２ Based on this value, the appropriate amount can be determined in real time according to the mixing state, without any prior adjustments or preparations. Furthermore, as the mixing process progresses, the amount of binding solution added is reduced, preventing excessive addition and allowing for the addition of the appropriate amount of solid mixture.

[0068] In this embodiment, in the solution preparation step P21, after adding the binder solution, the torque is measured and used for determination after kneading for a reference time Th or longer, or when the torque fluctuation meets a certain standard. The torque tends to fluctuate immediately after adding the binder solution. By continuing kneading and measuring the torque after the powder has been almost uniformly wetted with the binder solution, the state of the powder and liquid can be accurately grasped. This allows for the addition of the appropriate amount of binder solution at the appropriate time, resulting in a high-quality slurry.

[0069] In this embodiment, kneading is performed by rotating a stirring blade 25, such as in a kneading mixer 22, to knead the mixture. The rotation speed R1 of the stirring blade 25 in the solution preparation step P21 is set lower than the rotation speed R2 of the stirring blade 25 in this kneading step. This makes it possible to suppress a decrease in dispersibility due to excessive kneading.

[0070] In this embodiment, the timing of the end of the mixing process is determined from the mixing time after the start of mixing and the cumulative value of the power or current used during mixing. This configuration prevents excessive kneading. As a result, the rupture of binder molecules caused by excessive kneading is suppressed, and a high-quality slurry without lumps can be stably produced.

[0071] The kneading system according to this embodiment can be used for kneading in the kneading process P20. This kneading system comprises a kneading tank 21 for kneading material powder and binder liquid, a kneading mixer 22 which is an example of a kneading means for kneading the material powder and binder liquid in the kneading tank 21, a measuring device 3 for measuring the torque applied to the mixture by the kneading means, and an adding device 4 which is an example of an adding device for adding binder liquid to the kneading tank 21 while controlling the amount added. This kneading system makes it possible to carry out the kneading process appropriately and automatically.

[0072] Furthermore, the kneading in the pre-mixing step may be carried out using a kneading device other than the kneading system of this embodiment, or it may be carried out using the kneading system of this embodiment. Also, the kneading in the dilution step may be carried out using a dispersion device other than the kneading system of this embodiment, or it may be carried out using the kneading system of this embodiment.

[0073] The slurry manufacturing method of this embodiment can be applied to the production of various slurries, even if the powder properties differ. For example, it can be applied to the production of slurries for the positive electrode layer, SE layer, and negative electrode layer of an all-solid-state battery.

[0074] The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of disclosure are considered to be within the scope of the invention.

[0075] 1. Mixing system, 2. Mixing device, 3. Measuring device, 4. Adding device, 5. Control device, 21. Mixing tank, 22. Mixing mixer, 25. Stirring blade, 24. Rotating shaft, 25. Stirring blade, 26. Motor, 27. Driver, 51. Processing unit, 52. Memory unit, 53. Communication unit

Claims

1. A method for producing a slurry, comprising: a pre-mixing step of dry-mixing material powders; a kneading step of adding a binding solution to the mixture produced in the pre-mixing step and kneading in a high solids concentration state; and a dilution step of diluting the kneaded product produced in the kneading step with a binding solution to obtain a slurry, wherein the kneading step includes a solution preparation step of kneading the mixture while adding a binding solution, and a main kneading step following the solution preparation step of kneading the mixture without adding a binding solution, wherein in the solution preparation step, the amount of binding solution to be added (V) and the torque applied to the mixture for mixing are measured, and the total amount of binding solution to be added is determined based on the change in torque (F) with respect to the amount of binding solution added (V) (dF / dV), and then the main kneading step of kneading without adding a binding solution is carried out.

2. The solution adjustment step includes: a first addition step of adding a binder liquid with an initial addition amount V0 and kneading so that the material powder generated in the pre-mixing step is in a pendular state; and the second derivative value d ２ F / dV ２ of the torque value F with respect to the total addition amount V of the binder liquid is greater than 0, and the second derivative value d ２ F / dV ２ obtained by the previous addition of the binder liquid is greater. In this case, a first addition step of adding a binder liquid with a first addition amount Va not exceeding the initial addition amount V0 and kneading; and the second derivative value d ２ F / dV ２ of the torque value F with respect to the total addition amount V of the binder liquid is greater than 0, and the second derivative value d ２ F / dV ２ obtained by the previous addition of the binder liquid is smaller. In this case, a second addition step of adding a binder liquid with a second addition amount Vb less than the first addition amount Va and kneading; and the second derivative value d ２ F / dV ２ of the torque value F with respect to the total addition amount V of the binder liquid is 0 or less. In this case, a third addition step of adding a binder liquid with a third addition amount Vc less than the second addition amount Vb and kneading. After the third addition step, when the first derivative value of the torque value F with respect to the total addition amount V of the binder liquid is within a reference range, the addition of the binder liquid is stopped and the main kneading is performed. The method for producing a slurry according to claim 1, characterized by the above.

3. The method for producing a slurry according to claim 1 or 2, characterized in that, in the solution preparation step, after adding the binding solution, the mixture is kneaded for a standard time or longer, and then the torque is measured and used for determination.

4. The method for producing a slurry according to claim 1, 2, or 3, characterized in that the mixing is performed by rotating a stirring blade to knead the mixture, and the rotation speed of the stirring blade in the solution preparation step is lower than the rotation speed of the stirring blade in the main mixing step.

5. The method for producing a slurry according to claim 2, characterized in that, in the kneading step, the timing of the end of kneading is determined from the kneading time after the start of kneading and the integrated value of the power or current used for kneading.

6. A kneading system comprising: a kneading tank for containing material powder and a binder liquid; a kneading means for kneading the material powder and binder liquid in the kneading tank; a measuring device for measuring the torque of the kneading means; and an adding device for adding the binder liquid to the kneading tank with controlled addition amounts based on the torque measured by the measuring device.

7. The kneading system according to claim 6, characterized in that, in the pre-mixing step described in claim 1, the mixing is performed by a mixing device other than the kneading means.

8. The kneading system according to claim 6, characterized in that, in the dilution step according to claim 1, the mixture kneaded by the kneading system and the binding liquid are mixed by a dispersion device other than the kneading system.

9. A method for producing a slurry according to any one of claims 1 to 5, characterized by producing a slurry for an all-solid-state battery.

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