Inspection Method and Inspection System for All-Solid-State Batteries

Abstract

To efficiently test an all-solid battery.SOLUTION: In a testing method for an all-solid battery, a cell 100 of the all-solid battery includes a plurality of coating layers. Each of the coating layers is formed by coating a current collector or a base material with a slurry manufactured through a kneading step of a solid electrolyte and a solvent. The coating layers include a positive electrode 1 formed by coating with a positive electrode slurry, a negative electrode 2 formed by coating with a negative electrode slurry, and a separator layer 3 formed by coating with a separator slurry. The testing method includes the steps of acquiring a measurement result of the viscosity of the corresponding slurry for at least one coating layer among the coating layers, and determining that the at least one coating layer is not usable if the acquired viscosity is out of a reference range determined based on a correlation between the viscosity of the corresponding slurry and the self-discharge amount of the cell 100 of the all-solid battery.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present disclosure relates to a method and a system for inspecting all-solid-state batteries.

Background Art

[0002] A method for inspecting an all-solid-state lithium battery (hereinafter referred to as "all-solid-state battery") using a lithium-ion conductive solid electrolyte has been proposed. For example, Japanese Patent Application Laid-Open No. 2017-27770 (Patent Document 1) discloses a method for inspecting the presence or absence of a short circuit in a cell. This inspection method includes an external short-circuit step of externally short-circuiting the positive and negative electrodes of the cell, a voltage measurement step of measuring the open-circuit voltage between the positive and negative electrodes of the cell after a certain period of time has elapsed since the end of the external short-circuit step, and a determination step of determining that the cell is unusable when the open-circuit voltage measured in the voltage measurement step is less than a threshold value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In general, there is always a demand for improving the efficiency of inspecting various batteries including all-solid-state batteries. Improving the inspection efficiency includes shortening the inspection time, saving inspection costs, reducing the number of man-hours for inspection, and the like.

[0005] The method described in Patent Document 1 requires assembling cells for the external short - circuit process and waiting for a certain period of time (so - called aging) for the voltage measurement process. These processes have room for improvement from the perspective of inspection efficiency.

[0006] This disclosure has been made to solve the above - mentioned problems, and one of the objects of this disclosure is to improve the inspection efficiency of all - solid - state batteries.

Means for Solving the Problems

[0007] (1) In the inspection method of an all - solid - state battery according to the first aspect of the present disclosure, the all - solid - state battery includes a plurality of coating layers. Each of the plurality of coating layers is formed by coating a slurry, which is produced through a kneading process of a solid electrolyte and a solvent, on a current collector or a substrate. The plurality of coating layers include a positive electrode layer formed by coating a positive electrode slurry, a negative electrode layer formed by coating a negative electrode slurry, and a separator layer formed by coating a separator slurry. The inspection method includes: a step of obtaining a measurement result of the viscosity of the corresponding slurry for at least one of the plurality of coating layers; and a step of determining that the at least one coating layer is not suitable for use when the obtained viscosity is outside a reference range determined based on the correlation between the viscosity of the corresponding slurry and the self - discharge amount of the all - solid - state battery.

[0008] (2) The at least one coating layer includes a positive electrode layer. The obtaining step is a step of obtaining a measurement result of the viscosity in the first stirring process of the positive electrode slurry.

[0009] (3) The reference range includes at least one of the first and second ranges. The first range is a range where the viscosity of the positive electrode slurry is more than 230 [mPa·s] and less than 370 [mPa·s] when the shear rate in the first stirring process of the positive electrode slurry is 38.3 [s -1 . The second range is a range where the viscosity of the positive electrode slurry is more than 230 [mPa·s] and less than 370 [mPa·s] when the shear rate in the first stirring process of the positive electrode slurry is 19.2 [s -1When it is [specific condition], the viscosity of the positive electrode slurry is in the range exceeding 400 [mPa·s] and less than 650 [mPa·s].

[0010] (4) At least one coating layer includes a separator layer. The obtaining step is a step of obtaining the measurement result of the viscosity in the first dispersion step of the separator slurry.

[0011] (5) The reference range includes a range where the shear rate in the first dispersion step of the separator slurry is 38.3 [s -1 When it is [specific condition], the viscosity of the separator slurry is in the range exceeding 165 [mPa·s] and less than 236 [mPa·s].

[0012] (6) Using a learned model by supervised learning, the manufacturing parameters of the slurry contributing to the self-discharge amount of the all-solid-state battery are extracted. The learned model has a first or second decision tree. The first decision tree includes the self-discharge amount as the target variable and the viscosity in the first stirring step of the positive electrode slurry as the explanatory variable. The second decision tree includes the self-discharge amount as the target variable and the viscosity in the first dispersion step of the separator slurry as the explanatory variable.

[0013] (7) The inspection system for the all-solid-state battery according to the second aspect of the present disclosure includes one or more processors and a memory. The memory causes the one or more processors to execute the inspection method described in (1) to (6) above when a program is executed by the one or more processors.

[0014] In the methods of (1) to (7) and the configuration of (8) above, the suitability of using the coating layer is determined based on the viscosity of the slurry. The coating layer determined to be unsuitable for use is not used in the assembly of the all-solid-state battery (cell). Therefore, it is possible to determine the quality before assembling the all-solid-state battery. Thus, according to the above methods and configurations, the inspection of the all-solid-state battery can be made efficient.

Advantages of the Invention

[0015] According to the present disclosure, the inspection of the all-solid-state battery can be made efficient.

Brief Description of the Drawings

[0016]

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Mode for Carrying Out the Invention

[0017] <Explanation of Terms> In this specification, elements expressed in the singular form include the plural form as well, unless otherwise specified. For example, "particle" can mean not only "one particle" but also "an aggregate of particles (powder, powder, particle group)".

[0018] When a compound is represented by a stoichiometric composition formula, the stoichiometric composition formula is only a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobaltate is expressed as "LiCoO 2 ", unless otherwise specified, lithium cobaltate is not limited to the composition ratio of "Li / Co / O = 1 / 1 / 2" and may contain Li, Co, and O in any composition ratio. Further, doping, substitution, etc. with trace elements may also be allowed.

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0020] [Embodiment 1] [System Configuration] FIG. 1 is a diagram showing an example of the configuration of an inspection system for an all-solid-state battery according to Embodiment 1 of the present disclosure. The inspection system 5 includes a server 51, an input device 52, a display 53, and a communication device 54. The server 51 includes a processor 511, a memory 512, a storage 513, and a network interface 514. The components of the inspection system 5 are connected to each other by a communication bus.

[0021] The processor 511 is, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The processor 511 reads out a system program 61 and a control program 62 (described later) and expands and executes them in the memory 512 to realize various processes.

[0022] The storage 513 is a rewritable non-volatile memory such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory. The storage 513 stores a system program 61 including an OS (Operating System), a control program 62 including computer-readable code necessary for control operations, battery management data 63 storing various manufacturing parameters (described later) for managing the all-solid-state battery, and a learned model 64 (described later).

[0023] The network interface 514 controls data communication between the server 51 and other external devices via the communication device 54.

[0024] The input device 52 is a keyboard, a mouse, etc., and receives input operations of an operator (measurer) who performs various measurements described later. The display 53 displays various information to the operator.

[0025] Note that, although FIG. 2 shows an example in which the server 51 includes one processor 511, the server 51 may include a plurality of processors. That is, the server 51 includes one or more processors. The same applies to the memory 512 and the storage 513.

[0026] In this specification, the term "processor" is not limited to a narrow sense processor that executes processing in a stored program manner, and may include hardwired circuits such as an ASIC (Application Specific Integrated Circuit) and an FPGA (Field-Programmable Gate Array). Therefore, the term "processor" can also be read as a processing circuitry whose processing is defined in advance by computer-readable code and / or a hardwired circuit.

[0027] <All-solid-state battery> FIG. 2 is a diagram showing an all-solid-state battery in Embodiment 2. The cell 100 of the all-solid-state battery includes a positive electrode 1, a negative electrode 2, and a separator layer 3. The cell 100 may include an exterior body (not shown) for housing a power storage element including the positive electrode 1, the negative electrode 2, and the separator layer 3. The exterior body is, for example, a pouch made of a metal foil laminate film. Note that the positive electrode 1 and the negative electrode 2 respectively correspond to the "positive electrode layer" and the "negative electrode layer" according to the present disclosure.

[0028] ≪Positive electrode≫ The positive electrode 1 includes a positive electrode active material layer 11 and a positive electrode current collector 12. The positive electrode active material layer 11 is formed by applying a positive electrode slurry (a slurry prepared by kneading a material and a solvent of the positive electrode active material layer 11) onto the surface of the positive electrode current collector 12 and drying it. The positive electrode active material layer 11 is in close contact with the separator layer 3. The positive electrode active material layer 11 may have a thickness of, for example, 10 to 200 μm.

[0029] The positive electrode active material layer 11 includes positive electrode active material particles and a sulfide solid electrolyte. The positive electrode active material particles are, for example, LiCoO 2 、LiNiO2 , LiMnO 2 , LiMn 2 O 4 , Li(NiCoMn)O 2 , Li(NiCoAl)O 2 , and LiFePO 4 may contain at least one selected from the group consisting of. The sulfide solid electrolyte contains S. The sulfide solid electrolyte may contain, for example, Li, P, and S. The sulfide solid electrolyte may further contain, for example, O, Si, etc. The sulfide solid electrolyte may further contain, for example, halogen, etc. The sulfide solid electrolyte may further contain, for example, I, Br, etc. The sulfide solid electrolyte may be, for example, of the glass-ceramics type or the argyrodite type. The sulfide solid electrolyte may be, for example, LiI-LiBr-Li 3 PS 4 , Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 S-P 2 S 5 , LiI-Li 2 O-Li 2 S-P 2 S 5 , LiI-Li 2 S-P 2 O 5 , LiI-Li 3 PO 4 -P 2 S 5 , Li 2 S-P 2 S 5 , and Li 3 PS 4 may contain at least one selected from the group consisting of.

[0030] The positive electrode active material layer 11 may further contain, for example, a conductive material. The conductive material can form an electron conduction path within the positive electrode active material layer 11. The compounding amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the coated active material. The conductive material may contain arbitrary components. The conductive material may contain, for example, at least one selected from the group consisting of carbon black, vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake.

[0031] The positive electrode active material layer 11 may further contain, for example, a binder. The compounding amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the coated active material. The binder may contain arbitrary components. The binder may contain, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride - hexafluoropropylene copolymer (PVdF - HFP), styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE).

[0032] The positive electrode current collector 12 may contain, for example, Al foil or the like. The positive electrode current collector 12 may have a thickness of, for example, 5 to 50 μm.

[0033] ≪Negative Electrode≫ The negative electrode 2 includes a negative electrode active material layer 21 and a negative electrode current collector 22. The negative electrode active material layer 21 is formed by coating a negative electrode slurry (a slurry prepared by kneading the material of the negative electrode active material layer 21 and a solvent) on the surface of the negative electrode current collector 22 and drying it. The negative electrode active material layer 21 is in close contact with the separator layer 3. The negative electrode active material layer 21 may have a thickness of, for example, 10 to 200 μm.

[0034] The negative electrode active material layer 21 contains negative electrode active material particles and a sulfide solid electrolyte. The negative electrode active material particles are, for example, graphite, Si, SiOx (0 < x < 2), and Li 4 Ti 5 O 12It may contain at least one selected from the group consisting of. The negative electrode active material layer 21 may further contain a conductive material and a binder. The sulfide solid electrolyte may be of the same type or different types between the positive electrode active material layer 11 and the negative electrode active material layer 21.

[0035] The negative electrode current collector 22 may contain, for example, a Cu foil, a Ni foil, etc. The negative electrode current collector 22 may have a thickness of, for example, 5 to 50 μm.

[0036] ≪Separator layer≫ The separator layer 3 is interposed between the positive electrode 1 and the negative electrode 2. The separator layer 3 separates the positive electrode 1 from the negative electrode 2. The separator layer 3 contains a sulfide solid electrolyte. The separator layer 3 may further contain a binder. The sulfide solid electrolyte may be of the same type or different types between the separator layer 3 and the positive electrode active material layer 11. The sulfide solid electrolyte may be of the same type or different types between the separator layer 3 and the negative electrode active material layer 21.

[0037] <Kneading of positive electrode slurry> The inspection method in the present embodiment predicts whether self-discharge (short circuit) of the all-solid-state battery cell 100 occurs based on the manufacturing parameters in the kneading process of the positive electrode slurry. To facilitate the understanding of the features of the inspection method in the present embodiment, the outline of the kneading process of the positive electrode slurry in Comparative Example 1 will be described. Note that kneading means at least one of dispersion and stirring.

[0038] Figure 3 is a flowchart showing the preparation procedure of the positive electrode slurry in Comparative Example 1. Hereinafter, the steps will be abbreviated as "S".

[0039] First, a positive electrode material for preparing a positive electrode slurry is weighed (S911). Subsequently, a first dispersion step and a first stirring step of the positive electrode slurry are performed (S912, S913). Thereafter, a second dispersion step and a second stirring step of the positive electrode slurry are performed (S914, S915). Further, a third dispersion step and a third stirring step of the positive electrode slurry are performed (S916, S917). Thereby, the kneading step of the positive electrode slurry is completed. Note that a part of the positive electrode material may be different or the same between the m-th dispersion step and the n-th dispersion step (m and n are different natural numbers).

[0040] In a series of steps including the dispersion step and the stirring step as described above three times each, the following can be mentioned as the manufacturing parameters of the positive electrode slurry that may cause self-discharge of the cell 100.

[0041] · Viscosity in the first stirring step · Viscosity in the second stirring step · Viscosity in the third stirring step · Particle size in the first dispersion step · Particle size in the second dispersion step · Particle size in the third dispersion step · Temperature in the first dispersion step · Temperature in the second dispersion step · Temperature in the third dispersion step · Temperature in the first stirring step · Temperature in the second stirring step · Temperature in the third stirring step · Solids content in the first stirring step · Solids content in the second stirring step · Solids content in the third stirring step <Machine learning> The inventors of the present invention used a machine learning method to extract from among the above-mentioned numerous manufacturing parameters which manufacturing parameter contributes to the self-discharge of the cell 100, in other words, which manufacturing parameter has a high correlation with the self-discharge amount of the cell 100. The result of the machine learning may be stored in the storage 513 as the learned model 64.

[0042] As the estimation model of machine learning, linear regression, logistic regression, support vector machine (SVM), decision tree, random forest, deep learning (neural network), naive Bayes, k-means, principal component analysis (PCA), LightGBM, XGBoost, Convolutional Neural Network (CNN), Recurrent Neural Network (RNN), Generative Adversarial Networks (GAN), etc. can be used. Among them, decision tree methods such as random forest, LightBGM, and XGBoost are preferred. Furthermore, the gradient boosting decision tree method (such as LightBGM, XGBoost) that can handle missing values enables learning even when some types of values of the explanatory variables are missing in the set of explanatory variables (manufacturing parameters of the positive electrode slurry) and target variables (self-discharge amount) used for learning. Therefore, it is preferred as the estimation model used in this embodiment. In this embodiment (the example in FIG. 4 described later), LightBGM is used.

[0043] As a method for calculating the contribution degree (importance) of each explanatory variable from the estimation model calculated by the above method, Feature Importance, Permutation Importance, SHapley Additive exPlanations (SHAP), etc. that can quantify the correlation between the explanatory variable and the target variable can be used. In this embodiment, Feature Importance is used.

[0044] Figure 4 is a diagram summarizing the contribution degrees of the manufacturing parameters of the positive electrode slurry to the self-discharge amount of the cell 100 obtained by machine learning. The manufacturing parameters with the top 5 contribution degrees are shown in Figure 4. As shown in Figure 4, the result was obtained that the contribution degree of the viscosity in the first stirring step was the highest. The second manufacturing parameter was the particle size in the first dispersion step. The third manufacturing parameter was the solid content rate in the second stirring step. The fourth manufacturing parameter was the viscosity in the third stirring step. The fifth manufacturing parameter was the viscosity in the second stirring step.

[0045] <Measured Results> The results of actually evaluating the relationship between the manufacturing parameters of the positive electrode slurry in the first to third places and the self-discharge amount of the cell 100 will be described.

[0046] ≪Positive Electrode≫ The following materials were used for the positive electrode slurry and the positive electrode current collector.

[0047] Positive electrode active material: NCA-based positive electrode active material Solid electrolyte: Sulfide solid electrolyte Conductive material: VGCF Binder: PVdF Dispersion medium: Butyl butyrate Positive electrode current collector: Al foil The positive electrode slurry was prepared by kneading the positive electrode active material, the solid electrolyte, the conductive material, the binder, and the dispersion medium. An ultrasonic homogenizer was used for the dispersion step of the positive electrode slurry. A stirring blade was used for the stirring step of the positive electrode slurry. A coating film was formed by coating the positive electrode slurry on the surface of the positive electrode current collector 12 by the blade method. The coating film was dried at 100 °C for 30 minutes using a hot plate. Thereby, a positive electrode raw sheet was manufactured. The positive electrode 1 was cut out from the positive electrode raw sheet.

[0048] ≪Negative Electrode≫ The following materials were used for the negative electrode slurry and the negative electrode current collector.

[0049] Negative electrode active material: LTO particles Solid electrolyte: Li 2S-P 2 S 5 is a sulfide solid electrolyte Conductive material: VGCF Binder: PVdF Dispersion medium: butyl butyrate Negative electrode current collector: Ni foil A negative electrode slurry was prepared by kneading a negative electrode active material, a solid electrolyte, a conductive material, a binder, and a dispersion medium. An ultrasonic homogenizer was used in the dispersion step of the negative electrode slurry. A stirring blade was used in the stirring step of the negative electrode slurry. A coating film was formed by applying the negative electrode slurry onto the surface of the negative electrode current collector 22 by the blade method. The coating film was dried at 100 °C for 30 minutes using a hot plate. Thereby, a negative electrode green sheet was manufactured. The negative electrode 2 was cut out from the negative electrode green sheet.

[0050] ≪Separator layer≫ The following materials were used for the separator slurry and the base material.

[0051] Solid electrolyte: sulfide solid electrolyte Binder: PVdF Dispersion medium: butyl butyrate Base material: Al foil A separator slurry was prepared by kneading a solid electrolyte, a binder, and a dispersion medium. An ultrasonic homogenizer was used in the dispersion step of the separator slurry. A stirring blade was used in the stirring step of the separator slurry. A coating film was formed by applying the separator slurry onto the surface of the base material by the blade method. The coating film was dried at 100 °C for 30 minutes using a hot plate. Thereby, a separator green sheet was manufactured. The separator layer 3 was cut out from the separator green sheet.

[0052] ≪Fabrication of battery≫ The negative electrode 2 was overlapped on one surface of the separator layer 3 and pressed at 1 [ton / cm 2 , and then the base material of the separator layer 3 was removed. Next, the positive electrode 1 was overlapped on the other surface of the separator layer 3 and pressed at 3 [ton / cm 2Pressing was performed. The power storage element and the tab with a welding tape were ultrasonically joined. Then, the power storage element was sealed with an aluminum laminate film to fabricate a small laminate cell of the all-solid-state battery.

[0053] ≪Judgment Criteria≫ The voltage of the cell 100 of the all-solid-state battery that had been initially charged was measured when it was left standing for two days. The voltage of the cell 100 when it was left standing for one more day was measured. The difference between these two voltages was taken as the self-discharge amount. When the self-discharge amount of the cell 100 is 3.4 mV or less, the cell 100 is judged to be a good product. On the other hand, when the self-discharge amount of the cell 100 exceeds 3.4 mV, the cell 100 is judged to be a defective product.

[0054] ≪Comparison of Viscosity, Particle Size, and Solids Content Ratio≫ The evaluation results of the viscosity, particle size, and solids content ratio of the positive electrode slurry with respect to the self-discharge amount will be described. Note that the viscosity, particle size, and solids content ratio can be measured using an E-type viscometer, a particle size gauge, and a moisture meter, respectively.

[0055] Figure 5 is a diagram showing the relationship between the viscosity (the first explanatory variable) in the first stirring step of the positive electrode slurry and the self-discharge amount (the target variable). The horizontal axis represents the viscosity of the positive electrode slurry in the first stirring step when the shear rate is 38.3 [s -1 . Figure 6 is a diagram showing the relationship between the particle size (the second explanatory variable) in the first dispersion step of the positive electrode slurry and the self-discharge amount. The horizontal axis represents the particle size of the positive electrode slurry in the first dispersion step. Figure 7 is a diagram showing the relationship between the solids content ratio (the third explanatory variable) in the second stirring step of the positive electrode slurry and the self-discharge amount. The horizontal axis represents the solids content ratio of the positive electrode slurry in the second stirring step. The vertical axis represents the self-discharge amount of the cell in all cases.

[0056] As shown in FIG. 5, the existence of a correlation between the viscosity and the self-discharge amount in the first stirring step of the positive electrode slurry was confirmed. From FIG. 5, it can be read that the self-discharge amount becomes 3.4 mV or less in the viscosity range where the viscosity in the first stirring step exceeds 230 [mPa·s] and is less than 370 [mPa·s]. In this viscosity range, since the self-discharge amount can be predicted from the viscosity, it is possible to determine the quality of cell 100 from the viscosity.

[0057] On the other hand, as shown in FIGS. 6 and 7, no clear correlation was confirmed between the particle size and the self-discharge amount in the first dispersion step of the positive electrode slurry, nor between the solid content ratio and the self-discharge amount in the second stirring step of the positive electrode slurry. Therefore, the self-discharge amount cannot be predicted from the particle size in the first dispersion step and the solid content ratio in the second stirring step, and the quality of cell 100 cannot be determined either.

[0058] ≪Effect of Shear Rate≫ It is conceivable that the state of the positive electrode slurry is affected by the shear force acting on the positive electrode slurry in the stirring step. The results of evaluating the effect of the shear rate will be described.

[0059] FIG. 8 is a diagram showing the relationship between the viscosity and the self-discharge amount in the first stirring step of the positive electrode slurry when the shear rate is 2 [s -1 . FIG. 9 is a diagram showing the relationship between the viscosity and the self-discharge amount in the first stirring step of the positive electrode slurry when the shear rate is 19.2 [s -1 . FIG. 10 is a diagram showing the relationship between the viscosity and the self-discharge amount in the first stirring step of the positive electrode slurry when the shear rate is 384 [s -1 . The horizontal axis represents the viscosity, and the vertical axis represents the self-discharge amount of cell 100.

[0060] Not only in the case where the shear rate is 38.3 [s -1 (see FIG. 5), but also in the case where the shear rate is 19.2 [s -1 , as shown in FIG. 9, the existence of a correlation between the viscosity and the self-discharge amount in the first stirring step was confirmed. When the shear rate is 19.2 [s -1When it is in the range where the viscosity in the first stirring step exceeds 400 [mPa·s] and is less than 650 [mPa·s], it can be read that the self-discharge amount becomes 3.4 mV or less. Note that the shear rate is 2 [s -1 or 384 [s -1 (see FIGS. 8 and 10), no clear correlation was confirmed.

[0061] <Processing Flow> FIG. 11 is a flowchart showing the preparation procedure of the positive electrode slurry in Embodiment 1. At least the steps of S104, S105, S106, and S111 among the steps described below are stored in the control program 62.

[0062] First, a positive electrode material for preparing the positive electrode slurry is weighed (S101). Subsequently, the first dispersion step and the first stirring step of the positive electrode slurry are performed (S102, S103). These steps are equivalent to the steps of S911 to S913 in Comparative Example 1 (see FIG. 3).

[0063] In S104, the server 51 (processor 511) acquires the measurement result of the viscosity in the first stirring step of the positive electrode slurry. The measurement result of the viscosity is preferably stored in the battery management data 63 together with the shear rate. For example, a signal indicating the measurement result of the viscosity may be output from an E-type viscometer to the server 51, and the measurement result of the viscosity may be automatically stored in the battery management data 63. Alternatively, the operator may input the measurement result of the viscosity by the E-type viscometer using the input device 52, and the input value may be stored in the battery management data 63. In these cases, the server 51 can acquire the measurement result of the viscosity (and the corresponding shear rate) in the first stirring step by reading the value stored in the battery management data 63.

[0064] In S105, the server 51 determines whether the measurement result of the viscosity in the first stirring step of the positive electrode slurry acquired in S104 is within a predetermined reference range. The reference range is determined based on the results of previous experiments. In the above example, the reference range is such that the shear rate is 38.3 [s-1 In the case of [], the viscosity range is more than 230 [mPa·s] and less than 370 [mPa·s] (see Fig. 5), and the shear rate is 19.2 [s -1 In the case of [], the viscosity range is more than 400 [mPa·s] and less than 650 [mPa·s] (see Fig. 9). The server 51 may display the determination result on the display 53. The server 51 may transmit the determination result to an external device (such as a terminal operated by an operator) via the communication device 54.

[0065] When the measurement result of the viscosity in the first stirring step of the positive electrode slurry is within the reference range (YES in S105), the server 51 determines that the positive electrode slurry is suitable for use (fabrication of the cell 100) (S106). In this case, the second dispersion step, the second stirring step, the third dispersion step, and the third stirring step are performed on the positive electrode slurry (S107 to S110). These steps are equivalent to the steps of S914 to S917 in Comparative Example 1.

[0066] On the contrary, when the measurement result of the viscosity in the first stirring step of the positive electrode slurry is outside the reference range (NO in S105), the server 51 determines that the positive electrode slurry is not suitable for use (S111). In this case, no further dispersion step and stirring step are performed on the positive electrode slurry. The positive electrode slurry is discarded, for example.

[0067] As described above, in Embodiment 1, based on the finding that there is a correlation between the viscosity in the first stirring step, which is one of the manufacturing parameters of the positive electrode slurry, and the self-discharge amount of the cell 100 (see Figs. 5 and 9), it is determined whether the viscosity in the first stirring step is within the reference range. While the positive electrode slurry with the viscosity in the first stirring step within the reference range is sent to the subsequent kneading step, the positive electrode slurry with the viscosity in the first stirring step outside the reference range is determined not to be suitable for incorporation into the cell 100. Thereby, it becomes possible to determine the quality of the cell 100 before assembling the cell 100. Therefore, according to Embodiment 1, the inspection of the cell 100 of the all-solid-state battery can be made more efficient.

[0068] In Embodiment 1, it was described that the kneading process of the positive electrode slurry includes the dispersion process and the stirring process three times each. However, the kneading process may include the dispersion process and the stirring process at least once each. The kneading process may include the dispersion process and the stirring process once or twice each, or may include one of the dispersion process and the stirring process once and the other twice, or may include the dispersion process and the stirring process four or more times.

[0069] [Embodiment 2] In Embodiment 1, an example of determining whether the positive electrode slurry can be used for manufacturing the cell 100 was described. In Embodiment 2, an example of determining whether the separator slurry can be used for manufacturing the cell 100 will be described. The configuration of the inspection system according to Embodiment 2 and the cell configuration of the all-solid-state battery are both the same as the configurations in Embodiment 1 (see FIGS. 1 and 2). Also, the machine learning method is the same. Therefore, detailed descriptions thereof will not be repeated.

[0070] <Kneading of Separator Slurry> FIG. 12 is a flowchart showing the preparation procedure of the separator slurry in Comparative Example 2. First, the separator layer material for preparing the separator slurry is weighed (S921). Subsequently, the first stirring process and the first dispersion process of the separator slurry are performed (S922, S923). Thereafter, the second stirring process of the separator slurry is performed (S924). Thereby, the kneading process of the separator slurry is completed.

[0071] <Machine Learning> FIG. 13 is a diagram summarizing the contribution degrees of the manufacturing parameters of the separator slurry to the self-discharge amount of the cell 100 obtained by machine learning. As shown in FIG. 13, for the control parameters of the separator slurry, the result that the contribution degree of the viscosity in the first dispersion process is the highest was obtained. The manufacturing parameters ranked second and below were, in descending order of contribution degree, the temperature in the first dispersion process, the temperature in the second stirring process, and the particle size in the first dispersion process.

[0072] <Measurement Results> The relationship between the manufacturing parameters of the separator slurries in the first to third positions and the self-discharge amount of Cell 100 will be described as a result of actual evaluation. The materials and manufacturing methods of the positive electrode 1, the negative electrode 2, and the separator layer 3 were the same as those described in Embodiment 1. Note that the temperature of the separator slurry can be measured using a thermometer.

[0073] FIG. 14 is a diagram showing the relationship between the viscosity (the first explanatory variable) in the first dispersion step of the separator slurry and the self-discharge amount. The horizontal axis represents the viscosity in the first dispersion step of the separator slurry when the shear rate is 38.3 [s -1 . FIG. 15 is a diagram showing the relationship between the temperature (the second explanatory variable) in the first dispersion step of the separator slurry and the self-discharge amount. The horizontal axis represents the temperature in the first dispersion step of the separator slurry. FIG. 16 is a diagram showing the relationship between the temperature (the third explanatory variable) in the second stirring step of the separator slurry and the self-discharge amount. The horizontal axis represents the temperature in the second stirring step of the separator slurry. The vertical axis represents the self-discharge amount of the cell in each case.

[0074] As shown in FIG. 14, the existence of a correlation between the viscosity in the first dispersion step of the separator slurry and the self-discharge amount was confirmed. From FIG. 14, it can be read that the self-discharge amount becomes 3.4 mV or less in the viscosity range where the viscosity in the first dispersion step exceeds 165 [mPa·s] and is less than 236 [mPa·s]. In this viscosity range, since the self-discharge amount can be predicted from the viscosity, it is possible to determine the quality of Cell 100 from the viscosity.

[0075] On the other hand, as shown in FIGS. 15 and 16, no clear correlation was confirmed between the temperature in the first dispersion step of the separator slurry and the self-discharge amount, nor between the temperature in the second stirring step of the separator slurry and the self-discharge amount. Therefore, the self-discharge amount cannot be predicted from these temperatures, and the quality of Cell 100 cannot be determined either.

[0076] FIG. 17 shows that the shear rate is 384 [s -1It is a diagram showing the relationship between the viscosity and the self-discharge amount in the first dispersion step of the positive electrode slurry in the case of -1 . When the shear rate is 384 [s -1 , unlike the case of (see Fig. 14), no clear correlation was confirmed between the viscosity and the self-discharge amount in the first stirring step.

[0077] <Processing flow> Fig. 18 is a flowchart showing the preparation procedure of the separator slurry in Embodiment 2. First, a separator layer material for preparing the separator slurry is weighed (S201). Subsequently, the first stirring step and the first dispersion step of the separator slurry are performed (S202, S203). These steps are equivalent to the steps of S921 to S923 in Comparative Example 2 (see Fig. 12).

[0078] In S204, the server 51 (processor 511) acquires the measurement result of the viscosity in the first dispersion step of the separator slurry. The measurement result of the viscosity may be automatically imported from the E-type viscometer together with the shear rate and stored in the battery management data 63, or may be stored in the battery management data 63 by manual input by the operator. The server 51 can acquire the measurement result (and the corresponding shear rate) of the viscosity in the first dispersion step of the separator slurry by reading the value stored in the battery management data 63.

[0079] In S205, the server 51 determines whether the measurement result of the viscosity in the first dispersion step of the separator slurry acquired in S204 is within a predetermined reference range. In the above example, the reference range is a viscosity range exceeding 165 [mPa·s] and less than 236 [mPa·s] when the shear rate is 38.3 [s -1 . (See Fig. 14)

[0080] If the measurement result of the viscosity in the first dispersion step of the separator slurry is within the reference range (YES in S205), the server 51 determines that the separator slurry is suitable for use (fabrication of the cell 100) (S206). In this case, a second stirring step is performed on the separator slurry (S207). This step is equivalent to the step of S924 in Comparative Example 2.

[0081] On the other hand, if the measurement result of the viscosity in the first dispersion step of the separator slurry is outside the reference range (NO in S205), the server 51 determines that the separator slurry is not suitable for use (S208). In this case, no further stirring step is performed on the separator slurry. The separator slurry is discarded, for example.

[0082] As described above, in Embodiment 2, based on the finding that there is a correlation between the viscosity in the first dispersion step, which is one of the manufacturing parameters of the separator slurry, and the self-discharge amount of the cell 100 (see FIG. 14), it is determined whether the viscosity in the first dispersion step is within the reference range. While the separator slurry with the viscosity in the first dispersion step within the reference range is sent to the second stirring step, the separator slurry with the viscosity in the first dispersion step outside the reference range is determined not to be suitable for incorporation into the cell 100. Thereby, it becomes possible to determine the quality of the cell 100 before assembling the cell 100. Therefore, according to Embodiment 2, similar to Embodiment 1, the inspection of the cell 100 of the all-solid-state battery can be made more efficient.

[0083] The kneading step of the separator slurry may include at least one dispersion step and at least one stirring step. The kneading step may include one dispersion step and two stirring steps as shown in FIG. 18, or may include each of the dispersion step and the stirring step three or more times.

[0084] Embodiment 1 and Embodiment 2 can be combined. That is, it is preferable to fabricate the positive electrode 1 using the positive electrode slurry determined to be suitable for use according to Embodiment 1, and fabricate the separator layer 3 using the separator slurry determined to be suitable for use according to Embodiment 2, and combine both to fabricate the cell 100 of the all-solid-state battery. However, the positive electrode 1 fabricated using the positive electrode slurry determined to be suitable for use according to Embodiment 1 may be combined with a separator layer fabricated by another method. The separator layer 3 fabricated using the separator slurry determined to be suitable for use according to Embodiment 2 may be combined with a positive electrode fabricated by another method.

[0085] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the description of the above embodiments but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0086] 100 Cell, 1 Positive electrode, 11 Positive electrode active material layer, 12 Positive electrode current collector, 2 Negative electrode, 21 Negative electrode active material layer, 22 Negative electrode current collector, 3 Separator layer, 5 Inspection system, 51 Server, 511 Processor, 512 Memory, 513 Storage, 514 Network interface, 52 Input device, 53 Display, 54 Communication device, 61 System program, 62 Control program, 63 Battery management data, 64 Learned model.

Claims

1. A method for inspecting an all-solid-state battery, wherein the all-solid-state battery includes a plurality of coated layers, each of the plurality of coated layers is formed by coating a slurry prepared through a kneading process of a solid electrolyte and a solvent on a current collector or a substrate, the plurality of coated layers include a positive electrode layer formed by coating a positive electrode slurry, a negative electrode layer formed by coating a negative electrode slurry, and a separator layer formed by coating a separator slurry, the inspection method includes a step of obtaining a measurement result of the viscosity of a corresponding slurry for at least one of the plurality of coated layers, and a step of determining that the at least one coated layer is not suitable for use when the obtained viscosity is outside a reference range, wherein the reference range is a viscosity range determined based on a measurement result of a correlation between the viscosity of the corresponding slurry and the self-discharge amount of the all-solid-state battery, and in which the self-discharge amount of the all-solid-state battery is equal to or less than a predetermined value, a method for inspecting an all-solid-state battery.

2. the at least one coated layer includes the positive electrode layer, the obtaining step is a step of obtaining a measurement result of the viscosity in the first stirring step of the positive electrode slurry, the method for inspecting an all-solid-state battery according to claim 1.

3. the reference range includes at least one of a first and a second viscosity range, The first viscosity range is such that when the shear rate in the first stirring step of the positive electrode slurry is 38.3 [s －１ , the viscosity of the positive electrode slurry is in the range of more than 230 [mPa·s] and less than 370 [mPa·s], The second viscosity range is such that when the shear rate in the first stirring step of the positive electrode slurry is 19.2 [s －１ , the viscosity of the positive electrode slurry is in the range of more than 400 [mPa·s] and less than 650 [mPa·s]. The method for inspecting an all-solid-state battery according to claim 2.

4. the at least one coated layer includes the separator layer, the obtaining step is a step of obtaining a measurement result of the viscosity in the first dispersion step of the separator slurry, the method for inspecting an all-solid-state battery according to claim 1.

5. The reference range includes a range where the viscosity of the separator slurry exceeds 165 [mPa·s] and is less than 236 [mPa·s] when the shear rate in the first dispersion step of the separator slurry is 38.3 [s －１ , the inspection method for an all-solid-state battery according to claim 4.

6. Using a learned model by supervised learning, manufacturing parameters of the slurry contributing to the self-discharge amount of the all-solid-state battery are extracted, and the extracted manufacturing parameters include the viscosity of the corresponding slurry, the learned model has a first or a second decision tree, the first decision tree includes the self-discharge amount as a target variable and the viscosity in the first stirring step of the positive electrode slurry as an explanatory variable, the second decision tree includes the self-discharge amount as a target variable and the viscosity in the first dispersion step of the separator slurry as an explanatory variable, the method for inspecting an all-solid-state battery according to claim 1.

7. one or more processors, and a memory, The memory causes the one or more processors to execute the inspection method according to any one of claims 1 to 6 when a program is executed by the one or more processors, for a solid-state battery inspection system.

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