Evaluation apparatus and evaluation method

Abstract

To evaluate a power storage device with improved accuracy.SOLUTION: An evaluation apparatus according to the present disclosure is the evaluation apparatus that executes an evaluation of a power storage device including a positive electrode and a negative electrode includes a control unit that executes an evaluation of the power storage device using a transmission line model that includes an electronic resistance at the positive electrode and the negative electrode, an ion resistance, and an interfacial resistance including a diffusion resistance in addition to a charge transfer resistance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification discloses an evaluation apparatus and an evaluation method. [Background technology]

[0002] Conventionally, as a method for evaluating lithium secondary batteries as power storage devices, a three-dimensional porous electrode model (3D-PEM), which is a transmission line model that takes into account the influence of a three-dimensional battery structure for the purpose of evaluating internal resistance, has been proposed (see, for example, Patent Document 1 and Non-Patent Document 1). The transmission line model replaces the complex reactions in a battery with a simple circuit diagram, making it possible to evaluate the internal resistance faster than so-called battery simulations that use a continuum model that solves the time evolution of reactions in the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 11568102 [Non-patent literature]

[0004] [Non-Patent Document 1] iScience, 23, 101317 (2020). Summary of the Invention [Problem to be solved by the invention]

[0005] However, the evaluation methods of Patent Document 1 and Non-Patent Document 1 use simplified circuit diagrams, and therefore the evaluation accuracy is insufficient, and there has been a demand for further improvement in the evaluation accuracy.

[0006] The present disclosure has been made in consideration of such problems, and has as its main object to provide a novel evaluation apparatus and evaluation method capable of evaluating an electricity storage device with improved accuracy. [Means for solving the problem]

[0007] As a result of intensive research to achieve the above-mentioned object, the inventors discovered that by introducing a factor of diffusion resistance into the interfacial resistance, it is possible to evaluate an electricity storage device with improved evaluation accuracy, and have completed the invention disclosed in this specification.

[0008] That is, the evaluation device of the present disclosure is An evaluation device for evaluating an electricity storage device having a positive electrode and a negative electrode, a control unit that executes evaluation of the power storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; It is equipped with the following:

[0009] The evaluation method of the present disclosure is An evaluation method for evaluating an electricity storage device having a positive electrode and a negative electrode, comprising: A step of evaluating the electricity storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; It includes. Effect of the Invention

[0010] The evaluation apparatus and evaluation method of the present disclosure can evaluate the power storage device with improved accuracy. The reason why such an effect is obtained is presumed to be as follows. For example, in a transmission line model, the inside of the electrode of the power storage device is a two-layer circuit consisting of an electrolyte part where ions flow, whose corresponding resistance is ionic resistance, and a solid part where electrons flow, whose corresponding resistance is electronic resistance. In addition, since the current carrier is switched from ions to electrons by the electrode reaction, the ionic resistance and the electronic resistance are connected by an interface resistance. In order to simplify the circuit, this interface resistance was made a transmission line model that takes into account the charge transfer resistance, but since the contribution of ion diffusion is also included, the diffusion resistance is also taken into account. As a result, the evaluation accuracy can be improved when evaluating the power storage device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram showing an example of an evaluation device 20. [Diagram 2] FIG. 2 is an explanatory diagram showing an example of the structure of an electricity storage device 10. [Diagram 3] FIG. 2 is an explanatory diagram showing an example of a three-dimensional electrode model. [Figure 4] 1A and 1B are explanatory diagrams illustrating the configuration of a conventional interface resistance and the configuration of an interface resistance according to the present disclosure. [Diagram 5] FIG. 4 is an explanatory diagram of an example of structure generating conditions for generating a three-dimensional battery structure. [Figure 6] FIG. 1 is an explanatory diagram of a three-dimensional battery structure generated using the structure generation conditions. [Figure 7] This is a graph showing the results of predicting the energy of a reference example 3D battery structure using a regression model. [Figure 8] FIG. 13 is a graph showing the results of predicting the energy of a three-dimensional battery structure according to an embodiment using a regression model. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Evaluation device) Embodiments of the evaluation device disclosed in this specification will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram showing an example of the evaluation device 20. FIG. 2 is an explanatory diagram showing an example of the structure of the power storage device 10. FIG. 3 is an explanatory diagram showing an example of a three-dimensional electrode model. FIG. 3A is a conceptual diagram of a three-dimensional battery in which the positive and negative electrodes are not flat plates, and FIG. 3B is a circuit diagram considering the structure of FIG. 3A. FIG. 4 is an explanatory diagram of the configuration of the conventional interfacial resistance and the interfacial resistance configuration of the present disclosure. The evaluation device 20 may be configured, for example, as a device that evaluates the internal resistance of the power storage device 10 by calculation.

[0013] Examples of the power storage device 10 include a hybrid capacitor, a pseudo electric double layer capacitor, an alkali metal secondary battery such as lithium or sodium, an alkali metal ion battery, and an air battery. Among these, as the power storage device 10, a lithium secondary battery, particularly a lithium ion secondary battery, is preferable. Here, the power storage device 10 will be mainly described as being a lithium ion secondary battery. The power storage device 10 may include, for example, a positive electrode 12, a negative electrode 15, and an ion conductive medium 18 interposed between the positive electrode 12 and the negative electrode 15. The ion conductive medium 18 may be composed of, for example, an electrolytic solution and a separator containing the electrolytic solution. Alternatively, the ion conductive medium 18 may be a solid electrolyte interposed between the positive electrode 12 and the negative electrode 15. The positive electrode 12 includes a current collector 14 and a positive electrode active material layer 13 formed on one surface of the current collector 14. The positive electrode active material layer 13 contains a positive electrode active material and may further contain a conductive material and a binder as necessary. Examples of the positive electrode active material include sulfides containing a transition metal element, composite oxides containing lithium and a transition metal element, and phosphate compounds containing iron. The positive electrode active material has, for example, a basic composition formula of Li (1-x) MnO2 (0 < x < 1, etc., the same applies hereinafter) or Li (1-x) Mn2O4 and other lithium manganese composite oxides, a basic composition formula of Li (1-x) CoO2 and other lithium cobalt composite oxides, a basic composition formula of Li (1-x) NiO2 and other lithium nickel composite oxides, a basic composition formula of Li (1-x) Ni a Cob Mn c Lithium nickel cobalt manganese composite oxides having a formula of O2 (a+b+c=1) can be used. Examples of the positive electrode active material include lithium iron phosphate. The term "basic composition formula" means that other elements may be included. The negative electrode 15 includes a current collector 17 and a negative electrode active material layer 16 formed on one side of the current collector 17. The negative electrode active material layer 16 includes a negative electrode active material, and may further include a conductive material or a binder as necessary. The negative electrode active material may include metallic lithium or its alloy, a carbon material, a composite oxide containing lithium, or the like. Examples of the negative electrode active material include inorganic compounds such as lithium, lithium alloys, and tin compounds, carbon materials capable of absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of the carbon material include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite are preferred. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. The separator may include an electrolyte solution in which a supporting salt is dissolved. Examples of the supporting salt include lithium salts such as LiPF6 and LiBF4. Examples of the solvent for the electrolyte solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, which can be used alone or in combination. Specifically, examples of the carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate, and chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate. The ionically conductive medium 18 may be a solid ionically conductive polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bound by an organic binder.

[0014] The evaluation device 20 is a device that executes evaluation of the electricity storage device 10 having the positive electrode 12 and the negative electrode 15. For example, the evaluation device 20 may evaluate the internal resistance, cell energy, and the like of the electricity storage device 10 having a predetermined battery structure including the distribution of the positive electrode 12 and the negative electrode 15 by using a transmission line model 24. The evaluation device 20 includes a control unit 21, a storage unit 22, an input device 38, and a display device 39. The control unit 21 is configured as a microprocessor centered on a CPU, and controls the entire device. The storage unit 22 is configured as a large-capacity storage device such as an HDD, and stores the evaluation program 23, the transmission line model 24, and the like. The input device 38 includes a mouse, a keyboard, and the like for performing various inputs. The display device 39 displays a screen, and is, for example, a liquid crystal display.

[0015] The control unit 21 performs evaluation of the electricity storage device 10 using a transmission line model 24 including electronic resistance 27, ionic resistance 28, and interface resistance 29 including diffusion resistance 31 in addition to charge transfer resistance 30 in the positive electrode 12 and the negative electrode 15. The transmission line model 24 is constructed as a model that takes into account the influence of a three-dimensional battery structure for the purpose of evaluating the internal resistance of the electricity storage device 10. This transmission line model 24 is a three-dimensional porous electrode model (3D-PEM) that replaces complex reactions in a battery with a simple circuit diagram, and is capable of performing evaluation of the electricity storage device 10, such as internal resistance, at a higher speed than so-called battery simulation that uses a continuum model that solves the time evolution of reactions in the battery.

[0016] As shown in FIG. 3, the transmission line model 24 has a structure in which the positive electrode 12 and the negative electrode 15 are divided into blocks, and an electronic resistance 27, an interface resistance 29, and an ionic resistance 28 are connected to each block. The transmission line model 24 is defined as a two-layer circuit in which an electronic resistance 27 is connected between each block to a solid part where electrons are conducted, and an ionic resistance 28 is connected between each block to an electrolyte part where ions are conducted, and has a structure in which the electronic resistance 27 and the ionic resistance 28 are connected by an interface resistance 29 so that the movement of ions and electrons is switched by an electrode reaction. Furthermore, the transmission line model 24 has a structure in which the positive electrode block 25 and the negative electrode block 26, which are separated by an ion conductive medium 18, are connected by an ionic resistance 28. As shown in FIG. 4, the transmission line model 24 includes an interface resistance 29 in which a diffusion resistance 31 is connected in series to a charge transfer resistance 30. In the transmission line model 24, a black circle or a white circle in the divided elements represents the center of each element, and the centers of the elements are connected by a resistance. Since this model models a porous electrode, the inside of the electrode is a two-layer circuit consisting of an electrolyte part where ions flow, whose corresponding resistance is ionic resistance, and a solid part where electrons flow, whose corresponding resistance is electronic resistance. In addition, since the current carrier switches from ions to electrons due to the electrode reaction, the ionic resistance 28 and the electronic resistance 27 are connected by an interface resistance 29. Until now, the 3D-PEM has evaluated the internal resistance of a battery cell using three types of resistance: electronic resistance 27, ionic resistance 28, and interface resistance 29. However, since there was a concern that the error would be large compared to the internal resistance evaluated by experiments or a continuum model, in this disclosure, a diffusion resistance 31 is introduced into the 3D-PEM.

[0017] 3D-PEM is an extension of the transmission line model (TLM) used in the analysis of porous electrodes in a normal flat-plate facing structure, as disclosed in, for example, Reference 1 (Ogihara et al., J. Electrochem. Soc., 159, A1034 (2012)). In 3D-PEM, a three-dimensional battery is first divided into elements as shown in Figure 3A, and an equivalent circuit is created by connecting the centers of the elements with resistors as shown in Figure 3B. Here, by dividing the elements so as to reflect the structural features, it becomes possible to evaluate the internal resistance taking into account the effect of the three-dimensional structure of the electrode. Here, these divided elements are also called electrode elements. In addition, in the porous electrodes used in general lithium-ion batteries, an electrolyte is permeated into the inside of the electrode, and a reaction occurs inside the electrode. To express this, in the transmission line model24, two types of circuits are placed within the electrode: electronic resistance (resistance of the solid part inside the electrode) represented by a thin line, and ionic resistance (resistance of the liquid part inside the electrode) represented by a thick line, and these are connected by interface resistance represented by a square. Here, the content of the interface resistance differs depending on the phenomenon to be modeled and the purpose of the analysis (internal resistance evaluation or impedance analysis); for example, when evaluating internal resistance assuming only a charge transfer reaction, it becomes charge transfer resistance.

[0018] Here, we will explain the definition of the resistance that constitutes the 3D-PEM. int 3D-PEM When evaluating the ionic resistance R ion , electronic resistance R e , and the charge transfer resistance R ct For example, the ionic resistance R between the same type of electrode elements, such as between the positive electrodes, is required. ion and electronic resistance R e , and the resistance between the same current collector elements is evaluated by the following equation (1): where ρ is the ionic resistivity ρ ion or electron resistivity ρ e where l and a are the length and cross-sectional area of ​​the resistor connecting the centers of the two electrode elements. The ionic resistance of the positive / negative electrode interface is defined by equation (2). Here, s is the thickness of the separator, and ρ ionpos , ρ ion neg , and ρ ion sep represent the ionic resistivities of the positive electrode, negative electrode, and separator, respectively. Here, ρ ion pos , ρ ion neg , and ρ ion sep is affected by the properties of the electrodes and separators, such as the tortuosity, and is therefore different from the ionic resistivity of the bulk electrolyte. The charge transfer resistance is defined by the following equation (3). Here, ρ ct and a reac is the reaction resistivity (Ωcm) at the interface between the active material and electrolyte in the electrode 2 ) and the reactive surface area. It is assumed that the reactive surface area can be calculated using the following equation (4). Here, v electrode is the volume of one electrode element excluding the volume of the separator, and c is a constant that converts the reaction surface area and the electrode volume. By substituting equation (4) into equation (3), equation (5) is obtained. Here, σ ct (=ρ ct / c ) is called the charge transfer resistivity, and its unit is Ωcm 3 From the above, the ionic resistivity ρ ion , electronic resistivity ρ e , and the charge transfer resistivity σ ct If the material parameter can be obtained, the internal resistance can be evaluated. For further details on 3D-PEM, please refer to Non-Patent Document 1 (Miyamoto et al., iScience, 23, 101317 (2020)) and its Supplemental Information, and the explanation will be omitted here.

[0019] In addition, in this disclosure, the contribution of diffusion to the internal resistance is introduced by expressing the interface resistance as a series connection of charge transfer resistance and diffusion resistance as shown in Figure 4. When considering a specific expression of the diffusion resistance, the Warburg impedance Z w(6) was used as a reference. Here, j and σ are the imaginary unit and the constant related to the diffusion condition, respectively. However, since the diffusion resistance corresponds to the case where the frequency ω = 0 in this equation, Z w =∞, and when this formula is used, the internal resistance becomes infinite. In other words, Z w The diffusion resistance calculated from the above cannot be used for the present purpose. Therefore, since the diffusion resistance actually observed is a finite value and the concentration gradient is generated by the reaction at the electrode / electrolyte interface, the diffusion resistance R d electrode We decided to express it in the same way as the charge transfer resistance equation (3) (equation (7)). Here, ρ d electrode / sol is the diffusion resistivity Ωcm 2 When the resistance between element centers in FIG. 3B (element centers are black or white circles) is determined, for example, as shown in equations (1) to (5) and (7), the internal resistance can be evaluated by standard methods such as the closed-circuit current method or the nodal potential method (Reference 2: Circuit Analysis Using Graph Theory by Kenji Hattori, Morikita Publishing Co., Ltd. (2014)). Since the internal resistance is the resistance between the positive and negative collector foils in FIG. 3A, for example, when the nodal potential method is used, the internal resistance can be evaluated by using Kirchhoff's second law by determining the potentials V1 and V2 of the nodes connected to the external power source.

[0020]

number

[0021] Here, an example of the evaluation of the internal resistance will be explained. The diffusion resistivity (equation (7)) required to evaluate the diffusion resistance is first calculated by R ct electrode Similarly, we can derive equation (8) using equation (4). Here, σ d electrode / sol is called the diffusion resistivity. σ d electrode / solSince depends on the lithium ion concentration, it may be a variable or may be simplified to a constant. This diffusion resistivity can be set to match the average value of the internal resistance by performing a discharge calculation using a continuum model for a predetermined structure (see FIG. 5 described later). Regarding the diffusion resistance, since it is known that only the diffusion resistance of the positive electrode mainly affects the battery performance during discharge, only the positive electrode side can be considered. For example, an energy prediction model can be created using this formula (8). FIG. 5 is an explanatory diagram of an example of a structure generation condition for generating a three-dimensional battery structure. As shown in FIG. 5, the evaluation device 20 can evaluate the power storage device 10 having a predetermined battery structure including the distribution of the positive electrode 12 and the negative electrode 15 by using a transmission line model 24.

[0022]

number

[0023] (Evaluation method) Next, the processing of the evaluation device 20 of the present embodiment thus configured, particularly the evaluation method executed by the evaluation device 20, will be described. This evaluation method is a method for executing evaluation of the electricity storage device 10. For example, this evaluation method may be a method for evaluating the internal resistance, cell energy, etc., of the electricity storage device 10 having a predetermined battery structure including the distribution of the positive electrode and the negative electrode, using a transmission line model 24. This evaluation method includes a step of executing evaluation of the electricity storage device 10 using a transmission line model 24 including an electronic resistance 27 in the positive electrode 12 and the negative electrode 15, an ionic resistance 28, and an interface resistance 29 including a diffusion resistance 31 in addition to a charge transfer resistance 30. Here, the transmission line model 24 uses the one exemplified in the evaluation device described above. For example, the transmission line model 24 has a structure in which the positive electrode 12 and the negative electrode 15 are divided into blocks, and the electronic resistance 27, the ionic resistance 28, and the interface resistance 29 are connected to each block. A node is provided in each block, and each resistance is connected to this node. The transmission line model 24 may be defined as a two-layer circuit in which an electronic resistor 27 is connected between each block to the solid portion where electrons are conducted, and an ionic resistor 28 is connected between each block to the electrolyte portion where ions are conducted. In this case, the transmission line model 24 has a structure in which the ionic resistor 28 and the electronic resistor 27 are connected by an interface resistor 29 so that the movement of ions and electrons is switched by an electrode reaction. The transmission line model 24 also has a structure in which the positive electrode block and the negative electrode block separated by the ion conductive medium 18 are connected by the ionic resistor 28. The transmission line model 24 is used for a structure including an interface resistor 29 in which a diffusion resistor 31 is connected in series to a charge transfer resistor 30. The diffusion resistor 31 can be set to an appropriate value depending on the material and structure of the electrode material. The electricity storage device 10 is stacked in the stacking direction in the order of the current collector 14, the positive electrode active material layer 13, the ion conductive medium 18, the negative electrode active material layer 16, and the current collector 17. In addition, a positive electrode active material layer 13 and a negative electrode active material layer 16 are formed along a surface direction perpendicular to the stacking direction. An electronic resistor 27 is connected to a node along the stacking direction and the surface direction. An ionic resistor 28 is connected to a node along the stacking direction and the surface direction.The interface resistance 29 is connected between a node of the electronic resistance 27 and a node of the ionic resistance 28 on the same coordinates in FIG. 3A.

[0024] In general, a storage device such as a lithium-ion secondary battery has a structure in which an electrolyte is permeated into a porous electrode, and in order to handle it accurately, the positive electrode block 25 and the negative electrode block 26 in FIG. 3A need to express a structure in which the electrode part and the permeated electrolyte part are complicatedly intertwined at a micro level (for example, see FIG. 1 in Reference 3: J. Electrochem. Soc., 143, 1890 (1996)). Since it is difficult to handle this structure as it is, the transmission line model 24 of the present disclosure simplifies the specific structural information, for example, the information on the interface between the electrode solid and the electrolyte, and approximates that the electrolyte and the electrode material are present on average (in the same space) at a specified ratio. Under this approximation, the coordinates of the center (node) of each element in FIG. 3A are the coordinates of the actual battery (real space coordinates), but the node for ion resistance and the node for electronic resistance connected by the interface resistance 29 in FIG. 3B represent the same coordinates in real space. That is, the nodes for both ions and electrons represent the same corresponding nodes in FIG. 3A.

[0025] In this evaluation method, when a specific positive electrode structure and negative electrode structure of the electricity storage device 10 are given, the internal resistance can be evaluated using the transmission line model 24.

[0026] The evaluation device 20 and the evaluation method of the present embodiment described above can evaluate the electricity storage device with improved accuracy. The reason why such an effect is obtained is presumed to be as follows. For example, in the transmission line model, the inside of the electrode of the electricity storage device is a two-layer circuit of an electrolyte part where ions flow, whose corresponding resistance is ionic resistance, and a solid part where electrons flow, whose corresponding resistance is electronic resistance. In addition, since the current carrier is switched from ions to electrons by the electrode reaction, the ionic resistance and the electronic resistance are connected by an interface resistance. In order to simplify the circuit, this interface resistance is a transmission line model that takes into account the charge transfer resistance, but since the contribution of ion diffusion is also included, the diffusion resistance is also taken into account. As a result, the evaluation accuracy can be improved when evaluating the electricity storage device.

[0027] It goes without saying that the present disclosure is in no way limited to the above-described embodiment, and can be embodied in various forms as long as it falls within the technical scope of the present disclosure.

[0028] The present disclosure may be any one of the following [1] to

[11] . [1] An evaluation device for evaluating an electricity storage device having a positive electrode and a negative electrode, a control unit that executes evaluation of the power storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; An evaluation device comprising: [2] The evaluation apparatus according to [1], wherein the transmission line model includes the interface resistance in which a diffusion resistance is connected in series to the charge transfer resistance. [3] The evaluation device according to [1] or [2], wherein the transmission line model has a structure in which a positive electrode and a negative electrode are divided into blocks, and the electronic resistance, the interface resistance, and the ionic resistance are connected to each block. [4] The evaluation device described in [3], wherein the transmission line model is defined as a two-layer circuit in which the electronic resistance is connected between each block in a solid portion where electrons are conducted, and the ionic resistance is connected between each block in an electrolyte portion where ions are conducted, and the ionic resistance and the electronic resistance are connected by the interface resistance so that the movement of ions and electrons is switched by an electrode reaction. [5] The electric storage device includes an ionically conductive medium between the positive electrode and the negative electrode, The evaluation device described in [3] or [4], wherein the transmission line model has a structure in which a positive electrode block and a negative electrode block separated by the ion conductive medium are connected by the ionic resistance. [6] An evaluation method for evaluating an electricity storage device having a positive electrode and a negative electrode, comprising: A step of evaluating the electricity storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; Evaluation methods including. [7] The evaluation method according to [6], wherein the transmission line model includes the interface resistance in which a diffusion resistance is connected in series with the charge transfer resistance. [8] The evaluation method according to [6] or [7], wherein the transmission line model has a structure in which a positive electrode and a negative electrode are divided into blocks, and the electronic resistance, the interface resistance, and the ionic resistance are connected to each block. [9] The evaluation method described in [8], wherein the transmission line model is defined as a two-layer circuit in which the electronic resistance is connected between each block of a solid portion through which electrons are conducted, and the ionic resistance is connected between each block of an electrolyte portion through which ions are conducted, and the ionic resistance and the electronic resistance are connected by the interface resistance so that the movement of ions and electrons is switched by an electrode reaction.

[10] The electric storage device includes an ionically conductive medium between the positive electrode and the negative electrode, The evaluation method according to [8] or [9], wherein the transmission line model has a structure in which a positive electrode block and a negative electrode block separated by the ion conductive medium are connected by the ionic resistance.

[11] A program for causing one or more computers to implement the steps of the evaluation method described in any one of [6] to

[10] . EXAMPLES

[0029] Below, an example in which the evaluation method and evaluation device of the present disclosure are specifically examined will be described as an experimental example.

[0030] In order to evaluate the effect of the present invention, the error of 3D-PEM for the internal resistance evaluated from the discharge calculation of the continuum model was evaluated for a three-dimensional lithium-ion battery. Furthermore, as reported in Reference 4 (Miyamoto et al., Cell Rep. Phys. Sci., 2, 100504 (2021)), a model can be created to predict the energy, which is an important characteristic of a 3D battery, by using the internal resistance of this 3D-PEM as one of the features. Therefore, the accuracy of the energy prediction model was also evaluated. The calculation conditions of the continuum model are described in detail in Reference 4.

[0031] FIG. 5 is an explanatory diagram of an example of structure generation conditions for generating a three-dimensional battery structure. FIG. 6 is an explanatory diagram of a three-dimensional battery structure generated using the structure generation conditions. This FIG. 5 shows the structure generation conditions when the 3D battery structure of FIG. 6 is generated by the Automatic geometry generator. As shown in FIG. 5, the dimensions of the three-dimensional battery are 3000 μm×600 μm×3000 μm, and the design resolution of the structure is 50×10. In this cell, the volume ratio of the positive and negative electrodes is 5:5, and only the area within the dotted frame is allowed as the design freedom. The lower half is determined by the periodicity, that is, the structure of the upper half is copied. The rectangular parallelepiped on the left side represents the positive electrode, and the rectangular parallelepiped on the right side represents the negative electrode. Here, 100 types of structures shown in FIG. 6 are used as the calculation target. These are the first 100 structures out of 50,000 structures generated using the Automatic geometry generator under the calculation conditions of FIG. 5 in Non-Patent Document 1. The materials used were lithium manganese oxide (LMO) as the positive electrode active material and graphite as the negative electrode active material. The electrolyte was a polymer electrolyte made by mixing a polymer with LiPF6 dissolved in a 1:2 volume ratio (EC+DMC) solvent at a concentration of 1.0M. The parameters used in the 3D-PEM and continuum simulation, except for the diffusion resistivity, were those described in Reference 4.

[0032] Regarding the diffusion resistance, since it is known that only the diffusion resistance of the positive electrode mainly affects the battery performance during discharge, only the positive electrode side was considered. The diffusion resistivity (Equation (7)) required to evaluate the diffusion resistance is first calculated by R ct electrode Similarly, we used equation (4) and changed it to equation (8), where σ d electrode / sol is called the diffusion resistivity. σ d electrode / sol Since depends on the lithium ion concentration, there is room for innovation in how to express it, but in this case it is a constant. This constant was determined by performing discharge calculations using a continuum model for structure 1 in Figure 6, and matching it to the average value of the internal resistance. The diffusion resistivity σ of the positive electrode obtained by this method d pos / solis 0.835Ωcm 3 Regarding the energy prediction model, as described in Reference 4, 1C (= 3.16 mA / cm 2 ) was used as the objective function to create a prediction model using principal component regression. Of the 100 pieces of data, the first 50 were used as training data, and the remaining 50 were used as test data. As mentioned above, this model uses the internal resistance evaluated by 3D-PEM as one of the features. For details on creating the prediction model, including other features, see Reference 4.

[0033] (Results and Discussion) FIG. 7 is a graph showing the result of predicting, by a regression model, the energy at 1C for 100 types of structures in FIG. 6 of the three-dimensional battery structure of the reference example in which the internal resistance calculated without considering the diffusion resistance is one of the feature quantities. FIG. 8 is a graph showing the result of predicting, by a regression model, the energy at 1C for 100 types of structures in FIG. 6 of the three-dimensional battery structure of the embodiment in which the internal resistance calculated with consideration of the diffusion resistance is one of the feature quantities. Here, the True energy and Predicted energy in FIGS. 7 and 8 respectively represent the energy evaluated by the continuum model and the prediction result by the regression model. Details of other calculation conditions and comparison methods are described in detail in Reference 4. As shown in FIGS. 7 and 8, in the conventional evaluation method not considering the diffusion resistance, the R2 value of the test data is 0.41, whereas in the evaluation method of the present disclosure in which the diffusion resistance is considered, the R2 value is 0.56, which shows that the accuracy of the energy prediction model is improved.

[0034] Table 1 summarizes the average value (Ω) of the internal resistance evaluated by the continuum model and the internal resistance (Ω) evaluated by 3D-PEM for structures 1 to 5 in FIG. 6. In Table 1, the absolute error (%) from the average value of the internal resistance evaluated by the continuum model is shown in parentheses. As shown in Table 1, in the reference example in which the diffusion resistance is not taken into account, the absolute error is large at 35.6% to 37.9% and the average value is 36.7%, while in the example in which the diffusion resistance is taken into account, the absolute error is in the range of 0.62% to 2.39% and the average value is 1.2%, which is more accurate. In this way, it has been revealed that the evaluation of the electricity storage device can be performed more accurately by taking the diffusion resistance into account.

[0035] [Table 1]

[0036] It goes without saying that the evaluation device and evaluation method disclosed in this specification are in no way limited to the above-mentioned embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure. [Industrial Applicability]

[0037] The evaluation apparatus and evaluation method disclosed in this specification can be used in technical fields for evaluating the characteristics of electricity storage devices. [Explanation of symbols]

[0038] 10 electricity storage device, 12 positive electrode, 13 positive electrode active material layer, 14 current collector, 15 negative electrode, 16 negative electrode active material layer, 17 current collector, 18 ion conductive medium, 20 evaluation device, 21 control unit, 22 memory unit, 23 evaluation program, 24 transmission line model, 25 positive electrode block, 26 negative electrode block, 27 electronic resistance, 28 ionic resistance, 29 interface resistance, 30 charge transfer resistance, 31 diffusion resistance, 38 input device, 39 display device.

Claims

1. An evaluation device for evaluating an electricity storage device having a positive electrode and a negative electrode, a control unit that executes evaluation of the power storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; An evaluation device comprising:

2. The evaluation device according to claim 1 , wherein the transmission line model includes the interface resistance in which a diffusion resistor is connected in series with the charge transfer resistor.

3. 3 . The evaluation device according to claim 1 , wherein the transmission line model has a structure in which a positive electrode and a negative electrode are divided into blocks, and the electronic resistance, the interface resistance, and the ionic resistance are connected to each block.

4. 4. The evaluation device according to claim 3, wherein the transmission line model is defined as a two-layer circuit in which the electronic resistance is connected between each block of a solid portion through which electrons are conducted, and the ionic resistance is connected between each block of an electrolyte portion through which ions are conducted, and the ionic resistance and the electronic resistance are connected by the interface resistance so that the movement of ions and electrons is switched by an electrode reaction.

5. The power storage device includes an ionically conductive medium between the positive electrode and the negative electrode, The evaluation device according to claim 3 , wherein the transmission line model has a structure in which a positive electrode block and a negative electrode block separated by the ion conductive medium are connected by the ionic resistance.

6. An evaluation method for evaluating an electricity storage device having a positive electrode and a negative electrode, comprising: A step of evaluating the electricity storage device using a transmission line model including electronic resistance, ionic resistance, and interface resistance including diffusion resistance in addition to charge transfer resistance in the positive electrode and the negative electrode; Evaluation methods including.

7. The evaluation method according to claim 6 , wherein the transmission line model includes the interface resistance in which a diffusion resistor is connected in series with the charge transfer resistor.

8. The evaluation method according to claim 6 or 7, wherein the transmission line model has a structure in which a positive electrode and a negative electrode are divided into blocks, and the electronic resistance, the interface resistance, and the ionic resistance are connected to each block.

9. 9. The evaluation method according to claim 8, wherein the transmission line model is defined as a two-layer circuit in which the electronic resistance is connected between each block of a solid portion through which electrons are conducted, and the ionic resistance is connected between each block of an electrolyte portion through which ions are conducted, and the ionic resistance and the electronic resistance are connected by the interface resistance so that the movement of ions and electrons is switched by an electrode reaction.

10. The power storage device includes an ionically conductive medium between the positive electrode and the negative electrode, The evaluation method according to claim 8 , wherein the transmission line model has a structure in which a positive electrode block and a negative electrode block separated by the ion conductive medium are connected by the ionic resistance.

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