Evaluation method and evaluation device

Abstract

An evaluation method according to one embodiment of the present disclosure comprises: a strain formation step for generating a strain by applying vibration to a material having a dispersion medium and a particulate dispersoid dispersed in the dispersion medium; a measurement step of measuring the loss tangent of the material in which the strain has occurred for each frequency of the vibration; and an evaluation step for evaluating the moldability of the material on the basis of the minimum value or the maximum value of the loss tangent. The magnitude of the strain in the strain forming step is the magnitude of the arrangement of dispersoids in the breaking material.

Description

Technical Field

[0001] One aspect of the present disclosure relates to an evaluation method and an evaluation apparatus for evaluating the formability of a material. Background Art

[0002] In Patent Document 1, a viscoelasticity measurement method is disclosed in which even a substance having a high elastic modulus can be accurately measured for viscoelasticity. In this viscoelasticity measurement method, the viscoelasticity of a specimen is measured while the specimen is held between a pair of disk-shaped jigs. As the disk-shaped jigs, disk-shaped jigs having protrusions with a smaller cross-sectional area toward the front end on the surfaces in contact with the specimen are used.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open No. 7-260673. Summary of the Invention

[0006] The evaluation method according to one aspect of the present disclosure includes: a strain formation step of applying vibration to a material having a dispersion medium and particulate dispersoids dispersed in the dispersion medium to generate strain; a measurement step of measuring the loss tangent of the material in which the strain has been generated for each frequency of the vibration; and an evaluation step of evaluating the formability of the material based on (i) a minimum value or a maximum value of the loss tangent with respect to the frequency, or based on (ii) the frequency at which the minimum value is exhibited or the frequency at which the maximum value is exhibited, wherein the magnitude of the strain generated in the material in the strain formation step is a magnitude that disrupts the arrangement of the dispersoids in the material.

[0007] The evaluation apparatus according to one aspect of the present disclosure includes: a strain formation unit that applies vibration to a material having a dispersion medium and particulate dispersoids dispersed in the dispersion medium to generate strain; a measurement unit that measures the loss tangent of the material in which the strain has been generated for each frequency of the vibration; and an evaluation unit that evaluates the formability of the material based on (i) a minimum value or a maximum value of the loss tangent with respect to the frequency, or based on (ii) the frequency at which the minimum value is exhibited or the frequency at which the maximum value is exhibited, wherein the magnitude of the strain generated in the material by the strain formation unit is a magnitude that disrupts the arrangement of the dispersoids in the material. Brief Description of the Drawings

[0008] Figure 1 is a diagram illustrating the configuration of the evaluation apparatus of the present disclosure.

[0009] Figure 2 It is a diagram for explaining the absolute value |G*| of the complex elastic modulus of the material and tanδ (loss tangent).

[0010] Figure 3 It is a diagram showing an example of the measurement results of the material obtained by changing the amount of strain applied to the material by the strain forming section.

[0011] Figure 4 It is a diagram showing an example of the relationship between the frequency and |G*| obtained by changing the frequency of the vibration applied to the material by the strain forming section.

[0012] Figure 5 It is a diagram showing an example of the relationship between the frequency and tanδ obtained by changing the above frequency.

[0013] Figure 6 It is a diagram showing an example of the relationship between the defect rate and the minimum and maximum values of tanδ.

[0014] Figure 7 It is a diagram showing an example of the relationship between the defect rate and the frequency at which tanδ shows a minimum value or the frequency at which it shows a maximum value.

[0015] Figure 8 It is a flowchart showing an example of the evaluation method using the evaluation device of the present disclosure. Detailed Description of the Invention

[0016] (Example of the Configuration of Evaluation Device 1)

[0017] Figure 1 It is a diagram illustrating the configuration of the evaluation device 1 of the present disclosure. The evaluation device 1 may include a tray TR, a measurement jig 10, a thermoelectric conversion element 20, and a control device 30. The material MA to be evaluated using the evaluation device 1 is placed as a specimen on the tray TR.

[0018] The material MA may have a dispersion medium and particulate dispersoids dispersed in the dispersion medium. As an example, the material MA may be a so-called high-viscosity material. That is, when the dispersoids have an arbitrary arrangement at a certain moment, the dispersoids can maintain the original arrangement until an external force of a magnitude that can break the arrangement is applied to the material MA. The material MA may be, for example, a clay-like material. For example, the material MA may be a slurry. Specifically, the material MA may be, for example, a mixture of ceramic particles in a ceramic material and a solvent such as water, or a mixture of an electrode active material in a storage battery and a solvent such as water. Further, the material MA may also be an electrode material for a lithium-ion battery composed of a mixture of an electrode active material and a solvent. When the material MA is an electrode material for a lithium-ion battery, the evaluation device 1 of the present disclosure can evaluate the electrode material with high precision. The electrode material for a lithium-ion battery will be described later. However, the material MA of one aspect of the present disclosure may be any material that can be evaluated using the evaluation device 1 and is not limited to the above examples.

[0019] The evaluation device 1 is a device for evaluating the formability of the material MA. The material MA may be, for example, a material coated on an object to be coated. In this case, the "formability of the material MA" in this specification can be replaced, for example, with the "fluidity of the material MA". That is, a material with high formability can be replaced with a material with high fluidity. In addition, a material with low formability can be replaced with a material with low fluidity. As an example, in the dynamic viscoelasticity measurement described later, when the vibration frequency is set to 5 Hz and the strain is set to 0.5%, the absolute value |G*| of the complex elastic modulus of the material MA may be 100,000 Pa or more.

[0020] In addition, the ratio of the mass of the dispersoids to the mass of the material MA may be 60% by weight or more. According to the evaluation method of one aspect of the present disclosure, the formability of the material MA having the above ratio can be evaluated with high precision. In addition, according to the evaluation method of one aspect of the present disclosure, for example, the formability of ceramic clay can also be evaluated.

[0021] The measurement jig 10 can be designed to measure the dynamic viscoelasticity of the material MA. In other words, the measurement jig 10 can be configured to be able to measure the dynamic viscoelasticity of the material MA. Therefore, for example, the measurement jig 10 can be designed to generate strain in the material MA by vibration and output a signal corresponding to the response from the material MA. In other words, the measurement jig 10 can be configured to be able to output a signal corresponding to the above response from the material MA. As an example, the measurement jig 10 can output the complex elastic modulus G* corresponding to the response from the material MA. In other words, the measurement jig 10 can be configured to be able to output the complex elastic modulus G*. The control device 30 (more specifically, the measurement unit 32 described later) can derive the absolute value |G*| of the complex elastic modulus of the material MA and tanδ (loss tangent) from the complex elastic modulus G*.

[0022] For example, the measurement jig 10 is configured to include a display unit such as a liquid crystal display or an organic EL (Electro Luminescence) display, and can output the complex elastic modulus G* by displaying an image on the display unit. In addition, for example, the measurement jig 10 is configured to include a speaker and outputs the complex elastic modulus G* by outputting sound from the speaker.

[0023] Figure 2 It is a diagram for explaining the relationship between the complex elastic modulus G* of the material MA, |G*|, and tanδ. The complex elastic modulus G* can be used as an index representing the macroscopic hardness of the material MA.

[0024] As Figure 2 shown, the phase (deflection angle) of the complex elastic modulus G* is represented as δ. In this case, the real part G’ and the imaginary part G” of the complex elastic modulus G* are respectively expressed as follows,

[0025] G’ =|G*|×cosδ (1)

[0026] G’ ’ =|G*|×sinδ (2).

[0027] Therefore, tanδ is expressed as follows,

[0028] tanδ=sinδ / cosδ=G’ ’ / G’ (3)

[0029] tanδ represents the slope of the complex elastic modulus G* on the complex plane. tanδ can be used as an index representing which of the liquid characteristics or solid characteristics of the material MA is dominant. In Figure 2 the example, δ can take values from 0° to 90°. Therefore, tanδ can take values from 0 to ∞.

[0030] "G” and G’ correspond to the liquid characteristics and solid characteristics of the material MA, respectively. When tanδ is large (in other words, when δ is large), G” dominates over G’. In this case, the liquid characteristics of the material MA dominate over the solid characteristics of the material MA. Therefore, it can be considered that as tanδ increases, the physical properties of the material MA approach those of an ideal viscous body.

[0031] On the other hand, when tanδ is small (in other words, when δ is small), G’ dominates over G”. In this case, the solid characteristics of the material MA dominate over the liquid characteristics of the material MA. Therefore, it can be considered that as tanδ increases, the physical properties of the material MA approach those of an ideal elastic body.

[0032] Refer again to Figure 1 . The measurement fixture 10 may have a strain forming portion 11 as a portion that abuts against the material MA. The strain forming portion 11 may be designed to apply vibration to the material MA to cause strain in the material MA. Therefore, an evaluation method according to one aspect of the present disclosure may include a strain forming step of causing strain in the material MA.

[0033] The strain forming step may be executed by the strain forming portion 11. The strain forming portion 11 may include a disk-shaped measurement piece. The measurement piece rotates around a rotation axis, thereby causing strain in the material MA. As will be described later, the magnitude of the strain caused by the strain forming portion 11 in the material MA (in other words, the magnitude of the strain caused in the material MA in the strain forming step) only needs to be a magnitude that disrupts the arrangement of the dispersed substances in the material MA. The “magnitude that disrupts the arrangement of the dispersed substances in the material MA” described herein may refer to a magnitude such that 50% or more of the dispersed substances in the material MA are displaced from their positions before the strain is generated and do not return to their original positions.

[0034] By reducing the sliding between the material MA and the strain forming portion 11, the accuracy of measuring and evaluating the material MA can be improved. Therefore, for example, unevenness may be provided on the surface of the strain forming portion 11 that abuts against the material MA by knurling.

[0035] The thermoelectric conversion element 20 may be mounted on the tray TR. The thermoelectric conversion element 20 may include at least one of any heating element and cooling element. As an example of a heating element, a resistance element can be cited. As an example of a cooling element, a Peltier element can be cited.

[0036] The control device 30 performs overall control of each part of the evaluation device 1. In other words, the control device 30 is configured to be able to control each part of the evaluation device 1. The control device 30 may have a drive control portion 31, a measurement portion 32, and an evaluation portion 33. The drive control portion 31 may have a pressure control portion 311, a vibration control portion 312, and a temperature control portion 313.

[0037] The pressure control unit 311 can control the pressure applied by the strain forming unit 11 to the material MA. In other words, the pressure control unit 311 is configured to be able to control the pressure applied by the strain forming unit 11 to the material MA. Therefore, the strain forming unit 11 can apply the pressure specified by the pressure control unit 311 to the material MA and can cause the material MA to generate strain.

[0038] The vibration control unit 312 can control the rotation of the strain forming unit 11. In other words, the vibration control unit 312 is configured to be able to control the rotation of the strain forming unit 11. The vibration control unit 312 controls the rotation of the strain forming unit 11 and applies vibration to the material MA, thereby causing the material MA to generate strain. The vibration control unit 312 can also change the frequency of the vibration applied by the strain forming unit 11 to the material MA.

[0039] The temperature control unit 313 can control the thermoelectric conversion element 20. In other words, the temperature control unit 313 is configured to be able to control the thermoelectric conversion element 20. As an example, the temperature control unit 313 can control the temperature of the thermoelectric conversion element 20. In other words, the temperature control unit 313 is configured to be able to control the temperature of the thermoelectric conversion element 20. As described above, the temperature control unit 313 can set the temperature of the material MA to a specified temperature through the thermoelectric conversion element 20.

[0040] The measurement unit 32 can measure the tanδ (loss tangent) of the strained material MA for each frequency of the vibration applied to the material MA. Therefore, an evaluation method according to one aspect of the present disclosure can include a measurement step of measuring the tanδ of the material MA for each of the above frequencies. The measurement step can be executed by the measurement unit 32.

[0041] Whenever the strain forming unit 11 applies vibration of a specified frequency to the material MA, the measurement unit 32 can obtain the complex elastic modulus G* from the measurement jig 10. As described above, the measurement unit 32 can derive the absolute value |G*| of the complex elastic modulus of the material MA from the complex elastic modulus G*. And the measurement unit 32 can derive the tanδ of the material MA from the complex elastic modulus G*.

[0042] The evaluation unit 33 can evaluate the moldability of the material MA based on the measurement results obtained by the measurement unit 32. For example, as described later, the evaluation unit 33 can evaluate the moldability of the material MA based on the minimum or maximum value of tanδ with respect to the frequency of the vibration applied to the material MA. Therefore, the evaluation method according to one aspect of the present disclosure may include an evaluation step of evaluating the moldability of the material MA based on the above-mentioned minimum or maximum value. The evaluation step can be executed by the evaluation unit 33. For example, the evaluation unit 33 can evaluate the moldability of the material MA by comparing the minimum or maximum value of tanδ with a threshold value. The threshold value can be appropriately set in consideration of the relationship between the defect rate and the minimum or maximum value of tanδ described later and the magnitude of the strain.

[0043] (Relationship between strain and |G*| and tanδ)

[0044] The inventors of the present application (hereinafter, simply referred to as "the inventors") performed various measurements on the material MA using the evaluation device 1. Figure 3 An example of the measurement results of the material MA obtained by changing the strain amount (hereinafter, simply referred to as "strain amount") of the material MA by the strain forming unit 11 is shown. The strain amount can be replaced by the magnitude of the strain of the material MA.

[0045] Figure 3 In the measurement of the example, the material MA is a mixture (electrode material) of an electrode active material, a conductive assistant, a binder, and a solvent used in the electrode body constituting the negative electrode of the storage battery. In addition, the material MA can also be an electrode material that is a mixture of an electrode active material, a conductive assistant, a binder, and a solvent used in the electrode body constituting the positive electrode of the storage battery. Depending on the ratio of the solid components (dispersoids) composed of the electrode active material, the conductive assistant, and the binder in the electrode material, the electrode material can be in a slurry form or a clay form.

[0046] The electrode active material of the positive electrode can be, for example, lithium cobaltate, lithium nickelate, lithium iron phosphate, or lithium manganate. The electrode active material of the negative electrode can be, for example, graphite or lithium titanate. The conductive assistant can be, for example, carbon black composed of acetylene black or the like. However, the electrode active material of the positive electrode, the electrode active material of the negative electrode, and the conductive assistant are not limited to these.

[0047] In addition, the binder used in the positive electrode can be polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE). The solvent used in the positive electrode can be N-methyl-2-pyrrolidone (NMP). The binder used in the negative electrode can be carboxymethyl cellulose (CMC) or styrene-butadiene copolymer latex (SBR). The solvent used in the negative electrode can be purified water.

[0048] As the measurement jig 10, a rheometer (manufactured by Anton Paar, MCR301) was used. Specifically, the shape of the strain forming portion 11 used in this measurement was a circle with a diameter of 8 mm. The strain forming portion 11 abutted against the upper surface of the material MA formed in a cylindrical shape. The material of the strain forming portion 11 used in this measurement was stainless steel.

[0049] In the measurement, the strain amount was varied within the range of 0.001% to 100%. The strain amount described here refers to the value calculated by the following formula (1).

[0050] γ = θ × R / H (1)

[0051] In formula (1), γ is the strain amount, θ is the displacement angle (rotation amount) of the strain forming portion 11, R is the radius of the strain forming portion 11, and H is the interval between the strain forming portion 11 and the tray TR. That is, the strain amount refers to the offset amount of the outer edge portion of the uppermost surface of the material MA with respect to the height of the material MA formed in a cylindrical shape. In addition, in the measurement, the frequency of the vibration applied by the strain forming portion 11 to the material MA was set to a fixed value of 1 Hz.

[0052] In Figure 3 Figure 301 is a diagram showing an example of the relationship between the strain amount obtained by the measurement and |G*|. In the diagram of Figure 301, the horizontal axis represents the strain amount, and the vertical axis represents |G*|.

[0053] As shown in the diagram of Figure 301, within the range where the strain amount is 0.01% or less, |G*| has a substantially linear relationship with the strain amount. More specifically, within the range where the strain amount is 0.01% or less, |G*| is substantially constant regardless of the strain amount. This means that within the range where the strain amount is 0.01% or less, the arrangement of the dispersed substances in the material MA is maintained.

[0054] On the other hand, within the range where the strain amount is greater than 0.01%, |G*| has a non-linear relationship with the strain amount. More specifically, within the range where the strain amount is greater than 0.01%, |G*| decreases non-linearly as the strain amount increases. This indicates that within the range where the strain amount is greater than 0.01%, the arrangement of the dispersed substances in the material MA is disrupted.

[0055] In Figure 3 Figure 302 is a diagram showing an example of the relationship between the strain amount obtained by the above measurement and tanδ. In the diagram of Figure 301, the horizontal axis represents the strain amount, and the vertical axis represents tanδ.

[0056] As shown in the figure with reference numeral 302, in the range where the strain is 0.01% or less (the range where the arrangement of the dispersed substance in the material MA is considered to be maintained), tanδ shows a tendency to decrease as the strain increases, and then increase as the strain increases. On the other hand, in the range where the strain is greater than 0.01% (the range where the arrangement of the dispersed substance in the material MA is considered to be disrupted), tanδ shows a tendency to increase as the strain increases.

[0057] (Relationship between frequency and |G*|)

[0058] Figure 4 is a graph showing an example of the relationship between the frequency obtained by changing the frequency of the vibration applied to the material MA by the strain forming section 11 (hereinafter simply referred to as "frequency") and |G*|. Figure 4 in the measurement of the example of Figure 3 The material MA and the strain forming section 11 in the measurement of the example of Figure 4 in the measurement of the example, the frequency is changed in the range of 1 to 100 Hz. In Figure 4 In the graph, the horizontal axis represents the frequency and the vertical axis represents |G*|.

[0059] In Figure 4 In, reference numeral 401 is a graph showing the measurement result obtained when the strain is 0.01%. Reference numeral 402 is a graph showing the measurement result obtained when the strain is 1%. Reference numeral 403 is a graph showing the measurement result obtained when the strain is 5%. Reference numeral 404 is a graph showing the measurement result obtained when the strain is 10%.

[0060] According to the above description regarding Figure 3 it can be understood that when the strain is 0.01%, the arrangement of the dispersed substance in the material MA is considered to be maintained. On the other hand, when the strain is 1%, 5%, and 10%, the arrangement of the dispersed substance in the material MA is considered to be disrupted.

[0061] In Figure 4 In the example of, |G*| shows a tendency to decrease as the strain increases. On the other hand, for any strain, |G*| is independent of the frequency and is approximately constant. This indicates that |G*| has a dependence on the strain but almost no dependence on the frequency.

[0062] (Relationship between frequency and tanδ)

[0063] Figure 5 is a graph showing an example of the relationship between the frequency obtained by changing the frequency and tanδ. Figure 5In the example, the material MA and the strain forming section 11 are the same as Figure 4 in the example. In Figure 5 the figure, the horizontal axis represents the frequency and the vertical axis represents tanδ.

[0064] In Figure 5 , the reference numeral 501 is a graph showing the measurement results obtained when the strain is 0.01%. The reference numeral 502 is a graph showing the measurement results obtained when the strain is 1%. The reference numeral 503 is a graph showing the measurement results obtained when the strain is 5%. The reference numeral 504 is a graph showing the measurement results obtained when the strain is 10%.

[0065] As shown by the reference numeral 501, when the strain is 0.01%, tanδ does not have significant minimum and maximum values in the measurement frequency band (1 to 100 Hz). On the other hand, as shown by the reference numerals 502 to 504, when the strain is 1% or more, tanδ has significant minimum and maximum values in the measurement frequency band. Specifically, when the strain is 1% or more, tanδ has a significant minimum value around 6 Hz and a significant maximum value around 8 Hz. In addition, as the strain increases, the minimum and maximum values of tanδ also increase.

[0066] Figure 5 The measurement results in the example show that the frequency characteristics of tanδ become significant as the strain increases. The measurement results show that when the arrangement of the dispersed substance in the material MA is disrupted, the frequency characteristics of tanδ show a unique pattern.

[0067] Thus, when the arrangement of the dispersed substance in the material MA is disrupted, it is expected that useful information about the arrangement of the dispersed substance in the material MA can be obtained based on the frequency characteristics of tanδ. Therefore, for example, the amount of strain (the magnitude of the strain) generated in the material MA in the above strain forming step can be the amount that disrupts the arrangement of the dispersed substance in the material MA.

[0068] However, as described above, when the strain is 0.1%, it is also considered that the arrangement of the dispersed substance in the material MA is disrupted. As a result of further research by the inventors, it was confirmed that when the strain is 0.1%, tanδ also has a significant minimum value around 6 Hz and a significant maximum value around 8 Hz. Thus, when the strain is 0.1% or more, it is expected that useful information about the arrangement of the dispersed substance in the material MA can be obtained based on the frequency characteristics of tanδ.

[0069] (Example)

[0070] For example, when the material MA is an electrode active material, the formability of the material MA can be represented by the incidence rate (defect rate) of defective products in the case of manufacturing an electrode body by coating the material MA on a conductor.

[0071] The inventors prepared 9 kinds of samples to measure the defect rate. In graphite used as an electrode active material in the electrode body constituting the negative electrode of a storage battery, acetylene black as a conductive assistant and carboxymethyl cellulose as a binder were added, and the 9 kinds of samples were clay-like electrode materials obtained by mixing the thus obtained substances into purified water. Each sample was prepared by changing (i) the particle size of the electrode active material, (ii) the ratio of the solid components composed of the electrode active material, the conductive assistant, and the binder in the electrode material, (iii) the mixing conditions of the electrode active material and the conductive assistant in the mixer, and (iv) the kneading conditions of the electrode material in the kneader. The conditions, the absolute value |G*| of the complex elastic modulus, and the defect rate of the 9 kinds of samples are as shown in Table 1. |G*| in Table 1 is the measurement result obtained under a strain of 0.5% and a frequency of 5 Hz.

[0072] Table 1

[0073]

[0074] In Table 1, the "mixing conditions" represent the rotational speed of the scraper in the mixer for mixing the materials in three stages. The weakest rotational speed is the minimum, the strongest rotational speed is the maximum. The intermediate rotational speed is between the weakest and the strongest. In addition, in Table 1, the "kneading conditions" represent the mixing time of the materials using the mixer in three stages. The weakest mixing time is the shortest, the strongest mixing time is the longest. The intermediate mixing time is between the weakest and the strongest.

[0075] In addition, in Table 1, for the "defect rate", when the material MA was coated 100 times, it was classified into the following 5 grades based on the ratio of the coating without defects.

[0076] Grade 5: It can be coated without defects with a probability of 90% or more.

[0077] Grade 4: It can be coated without defects with a probability of 80% or more and less than 90%.

[0078] Grade 3: It can be coated without defects with a probability of 70% or more and less than 80%.

[0079] Grade 2: It can be coated without defects with a probability of 40% or more and less than 70%.

[0080] Grade 1: It can be coated without defects with a probability of less than 40%.

[0081] As used herein, "defects" refer to coating defects such as cracking that occur in the image of the electrode body manufactured by coating the conductive body with the material MA.

[0082] (Relationship between defect rate and minimum or maximum value of tanδ)

[0083] For example, when the material MA is an electrode active material, the formability of the material MA can be represented by the incidence rate (defect rate) of defective products in the case of manufacturing an electrode body by coating the conductive body with the material MA. The inventors et al. studied the relationship between the defect rate and the minimum and maximum values of tanδ.

[0084] Figure 6 is a graph showing an example of the relationship between the defect rate obtained by the inventors et al. and the minimum and maximum values of tanδ. In Figure 6 the example, tanδ was measured for 9 samples shown in Table 1. In Figure 6 the measurement in the example, the same rheometer as in Figures 3 to 5 the example was used as the measurement jig 10. However, Figure 6 in the measurement in the example, the shape of the strain forming portion 11 used was a circle with a diameter of 40 mm. In this measurement, the frequency was changed in the range of 1 to 50 Hz. On the other hand, the strain was set to a fixed value of 0.5%. Therefore, in this measurement, the arrangement of the dispersoid in the material MA was disrupted.

[0085] In Figure 6 the graph, the vertical axis represents the defect rate grade, and the horizontal axis represents the minimum and maximum values of tanδ. In Figure 6 the graph, a plurality of data points representing the measured values of the defect rate and the minimum and maximum values of tanδ are plotted. Figure 6 In Figure 6 the white square plotted points show the data of the minimum value, and the black circle plotted points show the data of the maximum value.

[0086] However, for the data of the maximum value of tanδ, the data of samples 7 to 9 in Table 1 were excluded. This is because it is speculated that if |G*| is 600000 Pa or more, the material MA itself becomes brittle and the damage caused by strain proceeds excessively, so that the maximum value of tanδ becomes too high to obtain an accurate value.

[0087] As Figure 6As shown, it was confirmed that tanδ tended to increase as the defect rate improved. In other words, it was confirmed that the defect rate tended to deteriorate as tanδ decreased. Therefore, Figure 6 the straight lines 601 and 602 in the example of

[0088] As an example of an index value indicating the degree to which a regression line matches a plurality of data points, the coefficient of determination R 2 can be cited. R 2 takes a value of 0 or more and 1 or less. It can be said that the larger R 2 is, the better the regression line explains a plurality of data points. In other words, a plurality of data points have a correlation represented by the regression line. In particular, if R 2 is 0.65 or more, it can be said that the regression line sufficiently well explains a plurality of data points. In other words, if R 2 is 0.65 or more, it can be said that a plurality of data points have a high correlation.

[0089] The inventors calculated the coefficient of determination R 2 for the straight lines 601 and 602. As a result, for the straight line 601, R 2 = 0.8157, and for the straight line 602, R 2 = 0.9425. As described above, the inventors found a high correlation between the defect rate and the minimum and maximum values of tanδ through the Figure 6 measurement results in the example of. In other words, the inventors found a high correlation between the minimum and maximum values of tanδ and the moldability of the material MA.

[0090] (Evaluation method based on the minimum or maximum value of tanδ)

[0091] Based on the above experimental results, the inventors found a new concept of "evaluating the moldability of the material MA based on the minimum or maximum value of tanδ when the arrangement of the dispersed substance in the material MA is disrupted".

[0092] Therefore, the evaluation method according to one aspect of the present disclosure may include the above-described strain forming step, measurement step, and evaluation step. And the amount of strain in the strain forming step may be the size that disrupts the arrangement of the dispersed substance in the material MA. According to this evaluation method, a minimum or maximum value of tanδ can be generated in a specific frequency region. Therefore, the moldability of the material MA can be evaluated based on this minimum or maximum value. Therefore, the evaluation device 1 only needs to be designed to be able to execute the strain forming step, measurement step, and evaluation step.

[0093] As an example, in the evaluation device 1, a threshold value corresponding to the minimum or maximum value of tanδ can be set. This threshold value can be set to the minimum or maximum value of tanδ corresponding to a specified defect rate. Thus, for example, referring to the straight line 601, in order to make the defect rate 3 or higher, when setting the threshold value for the minimum value of tanδ in the case where the strain is 0.5%, this threshold value can be set to 0.29. Further, referring to the straight line 602, in order to make the defect rate 3 or higher, when setting the threshold value for the maximum value of tanδ in the case where the strain is 0.5%, this threshold value can be set to 0.33, and |G*| can be set to less than 600000 Pa.

[0094] The evaluation unit 33 can evaluate the moldability of the material MA by comparing the minimum or maximum value of tanδ with the threshold value. When the minimum or maximum value of tanδ is equal to or greater than the threshold value, the evaluation unit 33 can determine that the moldability of the material MA is good. As described above, when tanδ is large, the material MA can be regarded as having physical properties close to those of an ideal viscous body. Thus, when the minimum or maximum value of tanδ is equal to or greater than the threshold value, it is considered that the material MA is suitable for coating on an object. When the material MA is a mixture of an electrode active material and an electrolytic solution, the object can be a conductor constituting an electrode.

[0095] On the other hand, when the minimum or maximum value of tanδ is less than the threshold value, the evaluation unit 33 can determine that the moldability of the material MA is poor. As described above, when tanδ is small, the material MA can be regarded as having physical properties close to those of an ideal elastic body. Thus, when the minimum or maximum value of tanδ is less than the threshold value, it is considered that the material MA is not suitable for coating on a conductor.

[0096] However, as described above, when the strain is 0.1% or more, it is expected that useful information regarding the arrangement of the dispersed substance in the material MA can be obtained based on the frequency characteristics of tanδ. Thus, for example, the magnitude of the strain generated in the material MA in the strain forming step can be 0.1% or more. As another example, as can be understood from the above Figure 5 example, the magnitude of the strain generated in the material MA in the strain forming step can also be 1% or more.

[0097] In the evaluation method according to one aspect of the present disclosure, during the strain forming step and the measurement step, the temperature of the material MA can be kept constant. Thereby, the influence of the temperature change of the material MA on tanδ can be reduced. Thus, the accuracy of measuring and evaluating the material MA can be improved. For example, by controlling the thermoelectric conversion element 20 by the temperature control unit 313, the temperature of the material MA can be kept constant.

[0098] The "constant temperature" in this specification can be interpreted to mean "substantially constant temperature". As an example, the temperature change of the material MA in the measurement step only needs to be within the range of ±0.1 °C.

[0099] In the evaluation method of one aspect of the present disclosure, in the strain formation step, the pressure when the measurement jig 10 (more specifically, the strain formation unit 11) applies vibration to the material MA can be kept constant. Thereby, the influence of the change in the pressure applied to the material MA on tanδ can be reduced. Therefore, the accuracy of measuring and evaluating the material MA can be improved. For example, by controlling the strain formation unit 11 by the pressure control unit 311, the pressure applied to the material MA can be kept constant.

[0100] The "constant pressure" in this specification can be interpreted to mean "substantially constant load". As an example, the change in the load applied to the material MA in the measurement step only needs to be within the range of ±0.25 N.

[0101] As an example, the evaluation device 1 may have a load detection unit that detects the load applied by the strain formation unit 11 to the material MA. The load detection unit can be, for example, a load cell installed in the strain formation unit 11. In this case, the pressure control unit 311 can control the strain formation unit 11 based on the load detected by the load detection unit. In other words, the pressure control unit 311 is configured to be able to control the strain formation unit 11 based on the load detected by the load detection unit. Thereby, the load when the strain formation unit 11 applies vibration to the material MA can be kept constant.

[0102] (Evaluation method based on the frequency at which tanδ shows a minimum value or the frequency at which it shows a maximum value)

[0103] Then, the inventors et al. studied the relationship between the defect rate and the frequency at which tanδ shows a minimum value or the frequency at which it shows a maximum value. Figure 7 It is a diagram showing an example of the relationship between the defect rate and the frequency at which tanδ shows a minimum value or the frequency at which it shows a maximum value obtained by the inventors et al. Figure 7 The measurement conditions and samples in the example of Figure 6 are the same as those in the example of

[0104] In Figure 7 the diagram, the vertical axis represents the defect rate, and the horizontal axis represents the frequency at which tanδ shows a minimum value or the frequency at which it shows a maximum value. In Figure 7 the diagram, a plurality of data points representing the measured values of the defect rate and the frequency at which tanδ shows a minimum or maximum value are plotted. Figure 7The black square plotted points therein represent the data of the minimum value, and the white circular plotted points represent the data of the maximum value. Figure 7 The straight lines 701 and 702 therein represent the approximate straight lines obtained by linear regression using the plurality of data points. The straight line 701 represents the approximate straight line related to the data points of the frequency at which tanδ shows the minimum value. The straight line 702 represents the approximate straight line related to the data points of the frequency at which tanδ shows the maximum value.

[0105] As Figure 7 shown, it was confirmed that as the defect rate improved, the frequency at which tanδ showed the minimum value or the maximum value tended to decrease. In other words, it was confirmed that as the frequency at which tanδ showed the minimum value or the maximum value increased, the defect rate tended to deteriorate. Therefore, Figure 7 the straight lines 701 and 702 in the example of

[0106] The inventors calculated the coefficient of determination R 2 for the straight lines 701 and 702. As a result, for the straight line 701, R 2 = 0.6743, and for the straight line 702, R 2 = 0.8305. As described above, the inventors found a high correlation between the defect rate and the frequency at which tanδ showed the minimum value or the maximum value through the measurement results in the example of Figure 7 . In other words, the inventors found a high correlation between the frequency at which tanδ showed the minimum value or the maximum value and the moldability of the material MA.

[0107] (Evaluation method based on the frequency at which tanδ shows the minimum value or the maximum value)

[0108] Based on the above experimental results, the inventors found a new concept of "evaluating the moldability of the material MA based on the frequency at which tanδ shows the minimum value or the maximum value when the arrangement of the dispersed substance in the material MA is destroyed".

[0109] Therefore, the evaluation method according to one aspect of the present disclosure may also include the above-mentioned strain forming step, measurement step, and evaluation step. And the amount of strain in the strain forming step may be the size that destroys the arrangement of the dispersed substance in the material MA. According to this evaluation method, a minimum value or a maximum value of tanδ can be generated in a specific frequency region. Therefore, the moldability of the material MA can be evaluated based on the frequency showing the minimum value or the frequency showing the maximum value. Therefore, the evaluation device 1 only needs to be designed to be able to execute the strain forming step, the measurement step, and the evaluation step.

[0110] As an example, in the evaluation device 1, a threshold value can be set corresponding to the frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value. The threshold value can be set to the frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value corresponding to a specified defective rate. Thus, for example, referring to the straight line 701, in order to make the defective rate 3 or above, when setting the threshold value for the frequency at which tanδ shows a minimum value in the case where the strain is 0.5%, the threshold value can be set to 13 Hz. Additionally, referring to the straight line 701b, in order to make the defective rate 3 or above, when setting the threshold value for the frequency at which tanδ shows a maximum value in the case where the strain is 0.5%, the threshold value can be set to 29 Hz.

[0111] The evaluation unit 33 can evaluate the moldability of the material MA by comparing the frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value with the threshold value. When the frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value is below the threshold value, the evaluation unit 33 can determine that the moldability of the material MA is good. As described above, when the frequency at which tanδ shows a minimum value or a maximum value is small, the material MA can be regarded as having the physical property of being easily fluidized under small shear force conditions. Thus, when the frequency at which tanδ shows a minimum value or a maximum value is below the threshold value, it is considered that the material MA is suitable for coating on the object. When the material MA is a mixture of an electrode active material and an electrolytic solution, the object can be a conductor constituting the electrode.

[0112] On the other hand, when the frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value is less than the threshold value, the evaluation unit 33 can determine that the moldability of the material MA is poor. As described above, when the frequency at which tanδ shows a minimum value or a maximum value is large, the material MA can be regarded as having the physical property that a larger shear force is required for fluidization. Thus, when the frequency at which tanδ shows a minimum value or a maximum value is greater than the threshold value, it is considered that the material MA is not suitable for coating on the conductor.

[0113] When the magnitude of the strain generated in the material MA in the strain forming step is small, for example, when it is less than 0.5%, the minimum value or the maximum value of tanδ tends to become smaller, and in the evaluation device 1, it is sometimes difficult to set the threshold value corresponding to the minimum value or the maximum value of tanδ. However, even when the strain amount is small, it is easy to set the threshold value corresponding to the frequency at which tanδ shows a minimum value or a maximum value. Therefore, the moldability of the material MA can be evaluated based on this threshold value.

[0114] When the viscosity of the material MA is high, that is, when |G*| is high, the material MA itself tends to become brittle. In this case, in order to reduce the strain amount, particularly, a threshold value corresponding to the frequency at which tanδ shows a minimum value can be set. On the contrary, when the viscosity of the material MA is low, that is, when |G*| is low, the strain amount can be increased, the maximum value of tanδ becomes larger, and thus it is easy to perform the evaluation. In this case, a threshold value corresponding to the frequency at which tanδ shows a maximum value can be set.

[0115] Tanδ sometimes has a minimum value or a maximum value within a certain frequency range, for example, 10 to 12 Hz. In this case, tanδ continuously takes a fixed minimum value or maximum value within this range. The frequency at which tanδ shows a minimum value or the frequency at which tanδ shows a maximum value in this case uses the minimum value within the range of the frequency at which tanδ shows a minimum value or a maximum value. In particular, tanδ mostly takes a minimum value within a certain frequency range. In the case where tanδ takes a minimum value within a certain frequency range, a threshold value can be set for the frequency at which tanδ shows a minimum value as described above. Or, as described above, instead of setting a threshold value for the frequency at which tanδ shows a minimum value, a threshold value can be set for the minimum value of tanδ.

[0116] In the evaluation method based on the frequency at which tanδ shows a minimum value or a maximum value, similar to the evaluation method based on the minimum value or the maximum value of tanδ, during the strain formation step and the measurement step, the temperature of the material MA can be kept constant. In addition, in the evaluation method based on the frequency at which tanδ shows a minimum value or a maximum value, similar to the evaluation method based on the minimum value or the maximum value of tanδ, the pressure when the measurement jig 10 (more specifically, the strain formation unit 11) applies vibration to the material MA can be kept constant.

[0117] (Example of the evaluation method using the evaluation device 1)

[0118] Figure 8 It is a flowchart showing an example of the evaluation method using the evaluation device 1. Before evaluating using the evaluation device 1, the strain formation unit 11 abuts against the material MA placed on the tray TR.

[0119] First, the vibration control unit 312 generates strain by applying vibration to the material MA through the strain formation unit 11 (S1, strain formation step). The measurement unit 32 measures tanδ of the material MA in which strain has been generated for each vibration frequency (S2, measurement step). The evaluation unit 33 evaluates the moldability of the material MA based on the maximum value of tanδ with respect to the frequency (S3, evaluation step). Through the above control, the evaluation device 1 can evaluate the moldability of the material MA.

[0120] 〔Summary〕

[0121] According to the evaluation method of one aspect of the present disclosure, the formability of a material MA having a high viscosity can be evaluated with high precision. Therefore, for example, the formability of a material in the case of manufacturing an electrode body by coating a clay-like material on a conductor can be evaluated with high precision.

[0122] Furthermore, by evaluating the formability of the material with high precision, the occurrence of defective products caused by using a material in a state with low formability can be reduced. That is, the resources consumed in manufacturing such defective products can be saved. Such an effect also contributes to, for example, achieving Goal 12, "Responsible consumption and production," of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0123] 〔Software-based implementation example〕

[0124] The functions of the evaluation device 1 (hereinafter referred to as "the device") can be implemented by a program for causing a computer to function as each control block of the device (particularly each part included in the control device 30), and this program is a program for causing a computer to function as the device.

[0125] In this case, the above-mentioned device has a computer, and this computer has at least one control device (such as a processor) and at least one storage device (such as a memory) as hardware for executing the above-mentioned program. By executing the above-mentioned program by this control device and storage device, the respective functions described in the above-mentioned respective embodiments are implemented.

[0126] The above-mentioned program can be recorded on one or a plurality of computer-readable recording media, rather than temporarily. The above-mentioned device may or may not have this recording medium. In the latter case, the above-mentioned program can be supplied to the above-mentioned device via any transmission medium, wired or wireless.

[0127] In addition, part or all of the functions of the above-mentioned respective control blocks can also be implemented by a logic circuit. For example, an integrated circuit formed with a logic circuit that functions as the above-mentioned respective control blocks is also included in the scope of the present disclosure. In addition to this, the functions of the above-mentioned respective control blocks can also be implemented by, for example, a quantum computer.

[0128] In addition, each process described in the above-mentioned respective embodiments can also be executed by AI (Artificial Intelligence). In this case, AI can operate in the above-mentioned control device, or can operate using other devices (such as an edge computer or a cloud server, etc.).

[0129] 〔Matters to be noted〕

[0130] As described above, the invention according to the present disclosure has been described with reference to the drawings and embodiments. However, the invention according to the present disclosure is not limited to the above-described embodiments. That is, the invention according to the present disclosure can be variously modified within the scope shown in the present disclosure, and embodiments obtained by appropriately combining the technical means separately disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. That is, it should be noted that those skilled in the art can easily make various deformations or modifications based on the present disclosure. In addition, it should be noted that these deformations or modifications are included in the scope of the present disclosure.

[0131] Description of Reference Numerals

[0132] 1 Evaluation device;

[0133] 11 Strain forming section;

[0134] 20 Thermoelectric conversion element;

[0135] 30 Control device;

[0136] 31 Drive control section;

[0137] 32 Measurement section;

[0138] 33 Evaluation section;

[0139] 311 Pressure control section;

[0140] 313 Temperature control section;

[0141] MA material.

Claims

1. An evaluation method, wherein, the evaluation method includes: a strain formation step of applying vibration to a material having a dispersion medium and particulate dispersoids dispersed in the dispersion medium to generate strain; a measurement step of measuring the loss tangent of the material in which the strain has been generated for each frequency of the vibration; and an evaluation step of evaluating the moldability of the material based on the minimum value or the maximum value of the loss tangent with respect to the frequency, or evaluating the moldability of the material based on the frequency showing the minimum value or the frequency showing the maximum value, the magnitude of the strain generated in the material in the strain formation step is a magnitude that disrupts the arrangement of the dispersoids in the material.

2. The evaluation method according to claim 1, wherein The magnitude of the strain generated in the material in the strain formation step is 0.1% or more.

3. The evaluation method according to claim 1 or 2, wherein The material is clay-like.

4. The evaluation method according to any one of claims 1 to 3, wherein, The ratio of the mass of the dispersoid to the mass of the material is 60% by weight or more.

5. The evaluation method according to any one of claims 1 to 4, wherein, During the strain formation step and the measurement step, the temperature of the material is kept constant.

6. The evaluation method according to any one of claims 1 to 5, wherein In the strain formation step and the measurement step, the pressure when the measurement jig that applies the vibration to the material applies the vibration to the material is kept constant.

7. An evaluation device, wherein, the evaluation device includes: a strain formation unit that applies vibration to a material having a dispersion medium and particulate dispersoids dispersed in the dispersion medium to generate strain; a measurement unit that measures the loss tangent of the material in which the strain has been generated for each frequency of the vibration; and an evaluation unit that evaluates the moldability of the material based on the minimum value or the maximum value of the loss tangent with respect to the frequency, or evaluates the moldability of the material based on the frequency showing the minimum value or the frequency showing the maximum value, the magnitude of the strain generated in the material by the strain formation unit is a magnitude that disrupts the arrangement of the dispersoids in the material.

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