Electric tomography method and electric tomography device

Abstract

An electric tomography method comprising extracting an electric equivalent circuit parameter obtained by electric measurement of a measurement target object, and visualizing a distribution of material properties of the measurement target object by inverse problem analysis of electric tomography of the electric equivalent circuit parameter.

Description

Electrical tomography method and electrical tomography apparatus

[0001] The present invention relates to an electrical tomography method and an electrical tomography apparatus.This application claims priority to Japanese Patent Application No. 2024-007043, filed on January 19, 2024, the contents of which are incorporated herein by reference.

[0002] Measuring the particle concentration distribution of positive electrode active materials and conductive additives within the positive electrode of a lithium-ion secondary battery, as well as visualizing and measuring the formation of interparticle networks due to aggregation and dispersion, are important because they contribute to improving battery performance and preventing accidents such as battery fires and explosions. The manufacturing process for the positive electrode used in the product includes, for example, a process of preparing a positive electrode slurry by stirring and mixing the positive electrode material and a solvent, a process of drying the positive electrode slurry, and a process of applying the dried positive electrode slurry to a current collector. Of these processes, the process of preparing the positive electrode slurry determines the particle concentration distribution within the positive electrode.

[0003] Therefore, there is a need for a technology that can visualize and measure the material properties (e.g., particle dispersion, aggregation, network formation) of positive electrode slurries during the process of preparing them. Electrical impedance spectroscopy (EIS) is known as a method for visually measuring the material properties of positive electrode slurries. This method involves passing a weak alternating current through the positive electrode slurry, which is the object being measured, and measuring the impedance, which represents the difficulty of current flow through the object. This allows for the acquisition of frequency-responsive electrochemical characteristics while minimizing the impact on the object being measured. Furthermore, electrical equivalent circuits (EECs) are commonly used as a means for analyzing data acquired by EIS. Representing the object being measured as an electrical circuit allows the evaluation of the electrical properties of the electrode interface and electrolyte. By fitting the impedance values ​​calculated from EECs to the measured impedance data, the values ​​of each element of EEC (EEC parameters) can be obtained. When this analysis method is applied to the process of preparing a positive electrode slurry, the state of the network formed by the positive electrode active material, the conductive additive, and the binder can be estimated by plotting the change in the EEC parameter with the stirring time (see, for example, Non-Patent Documents 1 and 2).

[0004] Electrical tomography (ET) is also known as a visualization measurement method using impedance data. ET is an image reconstruction method that performs impedance measurement using a multi-electrode sensor and visualizes the internal structure by utilizing the difference in electrical conductivity between the tissues of the object being measured. When this method is applied to positive electrode slurry, lithium cobalt oxide (LiCoO ２ The dispersion state of carbon black (CB) can be visualized by utilizing the fact that the conductivity of the conductive additive carbon black (CB) is higher than that of the conductive additive.

[0005] Z. Wang, T. Zhao, J. Yao, Y. Kishikawa, M. Takei, Evaluation of the Electrochemical Characteristics of Lithium-Ion Battery (LIB) Slurry with 10 Electrical Equivalent Circuits (EEC), Journal of the Electrochemical Society, 164(2), 2017, A8-A17. M. Itagaki, Special Feature: Fuel Cell Evaluation Technology, Volume 58, No. 3, 2007. N Ikeno, YAK Prayitno, PA Sejati, D Kawashima, M Takei-Advanced Powder Technology, 33(10), 2022, 103766.

[0006] The analysis of the positive electrode slurry by combining EIS and EEC has the problem that it evaluates the spatially averaged network formation between the electrodes and is unable to observe the local network formation that changes over time and space. On the other hand, the method of visualizing and measuring the mixed state of the positive electrode slurry by ET can observe the concentration (volume fraction) of CB particles, but it is difficult to observe the LiCoO ２ -There is a problem in that it is not possible to evaluate what kind of network is formed between CB particles.

[0007] The present invention has been made in consideration of the above circumstances, and provides a positive electrode slurry containing LiCoO ２The present invention aims to provide an electrical tomography method and an electrical tomography device that can spatiotemporally evaluate what kind of network is formed between -CB particles.

[0008] In order to solve the above problems, the present invention proposes the following means. [1] An electrical tomography method that extracts electrical equivalent circuit parameters obtained by electrical measurement of a measurement object and visualizes the distribution of material properties of the measurement object by electrical tomography inverse problem analysis of the electrical equivalent circuit parameters. [2] The electrical tomography method described in [1], wherein the electrical equivalent circuit parameters are electrical equivalent circuit parameters calculated from electrical elements configured according to the electrical properties of the measurement object. [3] The electrical tomography method described in [1] or [2], that visualizes the distribution of at least two of the material properties of the measurement object, time, and three-dimensional space. [4] An electrical tomography apparatus with three or more electrodes, comprising: a calculation unit that extracts electrical equivalent circuit parameters obtained by impedance measurement of the measurement object and performs electrical tomography inverse problem analysis of the electrical equivalent circuit parameters; and a display unit that displays the distribution of material properties of the measurement object based on the inverse problem analysis. [5] The electrical tomography apparatus according to [4], wherein the electrical equivalent circuit parameters are calculated from electrical elements configured according to the electrical properties of the object to be measured. [6] The electrical tomography apparatus according to [4] or [5], which visualizes the distribution of at least two of the material properties, time, and three-dimensional space of the object to be measured.

[0009] According to the above aspect of the present invention, in the positive electrode slurry, LiCoO ２ It is possible to provide an electrical tomography method and an electrical tomography device that can evaluate what kind of network is formed between -CB particles.

[0010] FIG. 1 is a diagram showing the overall configuration of an electrical tomography apparatus according to one embodiment of the present invention. FIG. 2 is a functional block diagram of an electrical tomography apparatus according to one embodiment of the present invention. FIG. 3 is a flow diagram of an electrical tomography method according to one embodiment of the present invention. FIG. 4 is a diagram showing an electrical equivalent circuit in the electrical tomography method according to one embodiment of the present invention. FIG. 5 is a Nyquist diagram drawn from the electrical equivalent circuit in the electrical tomography method according to one embodiment of the present invention. FIG. 6 is a diagram showing the overall configuration of an electrical tomography apparatus used in the examples, where (a) is a plan view and (b) is a front view. FIG. 7 is a diagram showing electrodes used in measuring the impedance of positive electrode slurry in the examples. FIG. 8 is a Nyquist diagram plotting impedance data obtained by measuring the impedance of positive electrode slurry in the examples. FIG. 9 is a diagram showing electrodes used in measuring the impedance of positive electrode slurry in the examples. FIG. 10 is a Nyquist diagram plotting impedance data obtained by measuring the impedance of positive electrode slurry in the examples. FIG. 11 is a diagram showing guidelines for fitting a Nyquist diagram using an electrical equivalent circuit in the examples. FIG. 12 is a Nyquist diagram drawn from an electrical equivalent circuit in the examples. FIG. 1 shows EEC-ET results for positive electrode slurry at stirring times t=30 seconds, 60 seconds, 120 seconds, and 1200 seconds in the examples. FIG. 2 shows the position where a sample was collected at a stirring time t=30 seconds in the examples. FIG. 3 shows the position where a sample was collected at a stirring time t=60 seconds in the examples. FIG. 4 shows the position where a sample was collected at a stirring time t=120 seconds in the examples. FIG. 5 shows the position where a sample was collected at a stirring time t=1200 seconds in the examples. FIG. 6 shows an SEM image of a sample collected at a stirring time t=30 seconds in the examples. FIG. 7 shows an SEM image of a sample collected at a stirring time t=60 seconds in the examples. FIG. 8 shows an SEM image of a sample collected at a stirring time t=120 seconds in the examples.

[0011] <Electrical tomography apparatus> An electrical tomography apparatus according to a first embodiment of the present invention will be described with reference to the drawings. Note that the dimensions and ratios of each component in the drawings do not represent the actual dimensions and ratios of each component.

[0012] 1 is a diagram showing the general configuration of an electrical tomography apparatus 1 according to this embodiment. The electrical tomography apparatus 1 includes a current application device 11, a multiplexer 12, an electrode-equipped container 13, multiple electrodes 14, a container 15, a connector 16, a display 17, a control device 18, electric wires 19, and a stirrer 20.

[0013] The current application device 11 is a device that applies a current to the electrode 14 disposed in the electrode-equipped container 13. The current application device 11 is, for example, an impedance analyzer that has a function of applying a current to the electrode 14 while changing the frequency and amplitude.

[0014] The multiplexer 12 is a device that switches between the electrodes 14 to which the current is applied by the current application device 11, among the plurality of electrodes 14. The multiplexer 12 has a function of determining a current application voltage measurement pattern (a pattern in which two electrodes 14 are selected in order from the plurality of electrodes 14, a current is applied, and a voltage is measured sequentially). That is, two of the electrodes 14 are selected, a current is applied, and two of the electrodes 14 are further selected, and a voltage is measured.

[0015] The electrode-equipped vessel 13 is equipped with a plurality of electrodes 14 and electric wires 19 connecting each electrode 14 to the multiplexer 12. The electric wires 19 and the electrode-equipped vessel 13 are connected by a connector 16.

[0016] The number of electrodes 14 is, for example, three or more, with no particular upper limit. The more electrodes 14 there are, the higher the resolution of the image that can be displayed by the display 17. The number of electrodes 14 is preferably eight or more, and more preferably sixteen or more. The number of electrodes 14 may be 32 or less, or may be 16 or less.

[0017] The arrangement positions of the electrodes 14 are not particularly limited as long as they are arranged on the inner surface 15a of the container 15 in which the object to be measured is accommodated. The electrodes 14 are preferably arranged at equal intervals along the inner surface 15a of the container 15 to suppress variations in the measurement voltage. However, some of the electrodes 14 may be arranged unevenly around the object to be measured, and the spacing between the electrodes 14 may be even or uneven. The unevenness or non-uniformity of the electrodes 14 is corrected in the calculation of the sensitivity matrix. In FIG. 1 , eight electrodes are arranged at equal intervals around the measurement area A.

[0018] The electrical tomography apparatus 1 of this embodiment is not particularly limited in the object to be measured, but examples of the object to be measured include biological substances and non-biological substances. Furthermore, when the object to be measured is a biological substance or a non-biological substance, the electrode 14 can also be used to control the potential of the biological substance or the non-biological substance. In this case, the electrode 14 is disposed, for example, within the measurement region A. The electrode 14 can image at least one of the permittivity and the conductivity while controlling ion channel activity.

[0019] The container 15 contains the object to be measured. The material of the container 15 is not particularly limited as long as it is not deteriorated by the object to be measured, and examples thereof include glass. Specific examples of the container 15 that can be used include a beaker and a chamber made of a metal such as stainless steel.

[0020] The display 17 displays an image of the distribution of material properties of the object to be measured (for example, the distribution of particle concentration or particle dispersion).

[0021] The control device 18 controls various operations of the electrical tomography apparatus 1. The control device 18 includes a storage device such as a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), or a hard disk drive (HDD) / solid state drive (SSD). The control device 18 is realized, for example, by the CPU executing a predetermined program. The program may be acquired via a recording medium or a network. Alternatively, a dedicated hardware configuration may be used to realize the configuration of the electrical tomography apparatus 1. Each component will be described below.

[0022] 2 is a functional block diagram of the electrical tomography apparatus 1 according to this embodiment. As shown in FIG. 2, the electrical tomography apparatus 1 includes a control unit 21, a calculation unit 22, a display unit 23, and a storage unit 24.

[0023] The control unit 21 has a function of controlling the overall operation of the electrical tomography apparatus 1. The control unit 21 is realized, for example, by causing a CPU included in the control device 18 to execute a program.

[0024] The calculation unit 22 extracts electrical equivalent circuit parameters obtained by measuring the impedance of the object to be measured, and performs an inverse problem analysis of electrical tomography of the electrical equivalent circuit parameters.

[0025] The display unit 23 displays the distribution of the material properties of the object to be measured. For example, the display unit 23 displays the distribution of at least two of the material properties of the object to be measured, time, and three-dimensional space.

[0026] The storage unit 24 stores information necessary for the calculations performed by the calculation unit 22, information related to the calculation process, and calculation results. The storage unit 24 also stores programs for the control unit 21 to perform various controls. The storage unit 24 is realized by a ROM, a RAM, and a HDD or SSD, etc.

[0027] <Electrical Tomography Method> Next, an electrical tomography method according to a second embodiment of the present invention will be described. The electrical tomography method of this embodiment utilizes a sensitivity matrix to extract electrical equivalent circuit parameters obtained by electrical measurement of a measurement object, and visualizes the distribution of material properties of the measurement object through inverse problem analysis of electrical tomography of the electrical equivalent circuit parameters. In the electrical tomography method of this embodiment, for example, the impedance of the measurement object is measured, and the obtained impedance data is plotted on a Nyquist diagram. Next, the Nyquist diagram is fitted with an electrical equivalent circuit. Next, using the obtained electrical equivalent circuit parameters, an image is reconstructed to visualize the distribution of material properties of the measurement object through inverse problem analysis of electrical tomography.

[0028] 3 shows a flow diagram of the electrical tomography method of this embodiment. In the electrical tomography method of this embodiment, for example, first, the impedance of the measurement object is measured (S1), and then the obtained impedance data is plotted on a Nyquist diagram (S2).

[0029] Next, the Nyquist diagram is fitted with an electrical equivalent circuit (S3). Guidelines for fitting the Nyquist diagram with an electrical equivalent circuit are shown below. Here, the measurement object is lithium cobalt oxide (LiCoO ２ The following example shows a positive electrode slurry containing PBN particles and carbon black (CB) particles. The components of the electrical equivalent circuit are the solution resistance R ｓｏ , resistance R due to dispersion of CB particles ｐｄ , capacitance C ｐｄ , LiCoO ２ Resistance at the particle interface R ｐｉ , electric double layer pseudocapacitance C ｐｉ , charge transfer resistance around the electrode R ｃｔ , electric double layer capacitance C ｄｌAs shown in Figure 4, for example, when the object to be measured is a positive electrode slurry, the positive electrode slurry has three parallel circuits, and the Nyquist diagram drawn from this electrical equivalent circuit has three semicircular arcs as shown in Figure 5. In addition, the semicircular arc portion in the low frequency part (first semicircular arc portion) is considered to be the characteristic due to the electric double layer around the electrode, the semicircular arc portion located in the center (second semicircular arc portion) is considered to be the electrical characteristic due to particle dispersion, and the semicircular arc portion in the high frequency part (third semicircular arc portion) is considered to be the electrical characteristic due to interface dispersion, and fitting was performed using the corresponding parallel circuits. Solution resistance R ｓｏ is the value of the real component of the impedance at the highest frequency point on the Nyquist diagram.

[0030] Next, among the obtained electrical equivalent circuit parameters, the dispersion resistance R of the CB particles ｐｄ , LiCoO ２ Resistance at the particle interface R ｐｉ The electrical conductivity distribution in the positive electrode slurry is extracted by inverse problem analysis of electrical tomography using the above equation (2). Then, an image reconstruction is performed to visualize the obtained electrical conductivity distribution (S4).

[0031] A current application voltage measurement pattern refers to a pattern in which two electrodes are selected in sequence from a plurality of (three or more) electrodes, a current is applied, and the potential difference between the electrodes is measured. The number of current application voltage measurement patterns varies depending on the method for measuring the potential difference, such as the adjacent method, the reference method, or the two-terminal method. Hereinafter, the total number of current application voltage measurement patterns is designated as M. Hereinafter, a pattern may be referred to as the mth current application voltage measurement pattern, where m is an integer between 1 and M.

[0032] Next, how to determine mesh coordinates will be explained. For example, to obtain an appropriate resolution, the area where the measurement object is placed (measurement area) is divided into a two-dimensional mesh according to the number of electrodes. For example, if there are eight electrodes, the measurement area can be divided into 64 areas in the x direction and approximately 64 areas in the y direction, resulting in a total of 4096 points, to create a mesh. A mesh refers to each divided area, and the coordinates of each mesh are the mesh coordinates. In the above example, the number of meshes N is 4096. Hereinafter, a mesh may be referred to as the nth mesh among multiple meshes, where n is an integer between 1 and N (the number of meshes).

[0033] Below, we will explain an electrical tomography method that visualizes (displays) the distribution of material properties of a measurement object in five dimensions: frequency, time, and three-dimensional space, using an example of a sensitivity matrix. Note that frequency refers to the frequency of the AC current flowing from the electrodes.

[0034] The linear equation of the inverse problem of five-dimensional electrical tomography is expressed by the following equation (1), similar to conventional electrical impedance tomography (EIT).

[0035]

[0036] In equation (1), J is the sensitivity matrix, L is the regularization function, and R ｅ is the resistance vector of the electric element e (number of measurement pairs M), λ is the regularization parameter, σ ｅ is the conductivity vector of the electric element e (number of meshes: M).

[0037] In the electrical tomography method of this embodiment, the inverse problem analysis is performed by iterative Gauss-Newton calculation using the following equation (2).

[0038]

[0039] The distribution of material properties of the object to be measured is imaged by the inverse problem analysis method described above.

[0040] In this embodiment, the object to be measured is not particularly limited, but examples of the object to be measured include biologically derived substances and non-biologically derived substances.

[0041] The biological substance is, for example, one or more selected from the group consisting of cells, tissues, living organisms, and biological constituents, such as ions, proteins, organelles, and cell nuclei.

[0042] Non-biological substances are not substances extracted from living organisms, but are generated, for example, during the manufacturing process of industrial products. Examples of non-biological substances include liquids, powders, slurries, and plastics containing gas bubbles. Therefore, the non-biological substance may be any one or more selected from the group consisting of liquids, powders, slurries, and plastics containing gas bubbles.

[0043] In the electrical tomography method according to the present embodiment, for example, the impedance of the object to be measured is measured, the obtained impedance data is plotted on a Nyquist diagram, the Nyquist diagram is fitted with an electrical equivalent circuit, and the obtained electrical equivalent circuit parameters are used to perform an inverse problem analysis of the electrical tomography to reconstruct an image that visualizes the distribution of the material properties of the object to be measured. Specifically, when the object to be measured is a positive electrode slurry, LiCoO ２ -The formation of a network between CB particles can be visualized.

[0044] The present invention has been described above using the present embodiment. However, the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0045] The effects of one embodiment of the present invention will be explained in more detail using examples. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0046] (Example) A positive electrode slurry was prepared according to the formulation shown in Table 1. First, in the container 15 of the electrode-equipped container 13 of the electrical tomography device, N-methyl-2-pyrrolidone (NMP) as an organic solvent and polyvinylidene fluoride (PVDF) as a binder were mixed by manual stirring to prepare an NMP-PVDF solution. A beaker with an inner diameter of 50 mm was used as the container 15. Next, lithium cobalt oxide (LiCoO ２ ) was added, and the NMP-PVDF solution and LiCoO ２ The mixture was thoroughly stirred. ２ Carbon black (CB) was added to an NMP-PVDF solution containing the above compound, and a positive electrode slurry was obtained in which the CB was floated on the supernatant of the NMP-PVDF solution, as shown in Figure 6. This state was designated as the initial state.

[0047]

[0048] Next, the impedance of the positive electrode slurry was measured using an apparatus similar to the electrical tomography apparatus 1 shown in FIG. 1. When measuring the impedance, the frequency range of the alternating current applied to the positive electrode slurry was 4 Hz to 5 MHz. The stirring speed of the stirrer 20 was set to 200 rpm, and the impedance of the positive electrode slurry was measured at stirring times t of 0 seconds, 30 seconds, 60 seconds, 90 seconds, 120 seconds, 150 seconds, 300 seconds, and 1200 seconds.

[0049] Next, of the obtained impedance data, data measured using two adjacent electrodes (No. 1 and No. 2) of the plurality of electrodes 14 as shown in FIG. 7 under five conditions (stirring time t = 0 seconds, 30 seconds, 60 seconds, 120 seconds, 1200 seconds) was plotted on a Nyquist diagram. The results are shown in FIG. 8. Furthermore, data measured using two electrodes (No. 1 and No. 3) sandwiching one electrode (No. 2) of the plurality of electrodes 14 as shown in FIG. 9 was plotted on a Nyquist diagram, and the results are shown in FIG. 10. As shown in FIGS. 8 and 10, it was found that the Nyquist diagram shrinks as the stirring time progresses. A shrinking Nyquist diagram indicates an increase in the conductivity of the positive electrode slurry.

[0050] Here, a guideline for fitting a Nyquist diagram using an electrical equivalent circuit is shown in Figure 11. The components of the electrical equivalent circuit include the solution resistance R ｓｏ , resistance R due to dispersion of CB particles ｐｄ , capacitance C ｐｄ , LiCoO ２ Resistance at the particle interface R ｐｉ , electric double layer pseudocapacitance C ｐｉ , charge transfer resistance around the electrode R ｃｔ , electric double layer capacitance C ｄｌ As shown in Figure 11, the positive electrode slurry has three parallel circuits, and the Nyquist diagram drawn from this EEC has three semicircular arcs as shown in Figure 12. The semicircular arc portion in the low frequency region (first semicircular arc portion) is considered to represent the characteristics due to the electric double layer around the electrode, the semicircular arc portion located in the center (second semicircular arc portion) is considered to represent the electrical characteristics due to particle dispersion, and the semicircular arc portion in the high frequency region (third semicircular arc portion) is considered to represent the electrical characteristics due to interface dispersion, and fitting was performed using the corresponding parallel circuits. Solution resistance R ｓｏ is the value of the real component of the impedance at the highest frequency point on the Nyquist diagram.

[0051] Next, among the EEC parameters, the dispersion resistance R of CB particles ｐｄ , LiCoO ２ Resistance at the particle interface R ｐｉ Image reconstruction by electrical tomography (ET) was performed using the above (EEC-ET). The EEC-ET results at stirring times of t = 30, 60, 120, and 1200 seconds are shown in Figure 13. In the reconstructed image, the initial state (NMP-PVDF solution + LiCoO ２ ), areas with high conductivity changes are shown in dark colors, and areas with low conductivity changes are shown in light colors. ２ Resistance at the particle interface R ｐｉ The EEC-ET results showed that as the stirring time t increased, the area with high conductivity changed spread from the center to the entire LiCoO ２ The increased conductivity at the particle interface is due to the LiCoO ２ This shows that CB particles are coating around the LiCoO２ The gaps between the particles are filled with CB particles, and LiCoO ２ This is thought to indicate that the formation of a network between CB particles is progressing. In addition, the conductivity change increases from the center, which indicates that the network formation begins around the position where the agitator blade is rotated. In addition, the resistance R due to the dispersion of CB particles ｐｄ The EIT results for LiCoO ２ Resistance at the particle interface R ｐｉ The results show the same tendency as the EEC-ET results of 1), but it was confirmed that the increase in conductivity spread more inclinedly toward three of the electrodes (No. 5, No. 6, and No. 7) among the electrodes 14. The resistance R due to the dispersion of CB particles ｐｄ In the image reconstructed using LiCoO, a high conductivity indicates that the CB particles are well dispersed, while a low conductivity indicates that the CB particles are aggregated and the conductive path is broken. The conductive path is formed by the CB particles being connected in a chain shape. This conductive path is formed by the LiCoO ２ A shape that fills the gaps between particles is the ideal shape for network formation.

[0052] Next, SEM images of the positive electrode material were taken to qualitatively compare the EEC-ET results with the particle distribution of the actual positive electrode slurry. Samples were collected at the positions indicated by dashed lines in Figures 14 to 17 at stirring times t = 30, 60, 120, and 1200 seconds. Figure 14 shows the sample collection position at stirring time t = 30 seconds. Figure 15 shows the sample collection position at stirring time t = 60 seconds. Figure 16 shows the sample collection position at stirring time t = 120 seconds. Figure 17 shows the sample collection position at stirring time t = 1200 seconds. Figure 18 shows an SEM image of the sample collected at stirring time t = 30 seconds. Figure 19 shows an SEM image of the sample collected at stirring time t = 60 seconds. Figure 20 shows an SEM image of the sample collected at stirring time t = 120 seconds. Figure 21 shows SEM images of the sample taken at a stirring time of t = 1200 seconds. In Figures 18 to 21, the white areas are LiCoO２ 18 to 21, as the stirring time t increases, the amount of LiCoO ２ It was found that the particles became uniformly distributed. As the stirring time t increased, the LiCoO ２ The CB particles and PVDF are distributed so as to fill the spaces between the particles, ２ It was found that the formation of a network between the LiCoO -CB particles was progressing. ２ The particles are sparse and no significant change is observed. At a stirring time of t = 1200 seconds, LiCoO ２ The particles are dispersed almost uniformly, and the LiCoO ２ The spaces between the particles are filled with CB particles and PVDF, so LiCoO ２ This result is considered to be due to the progress of the formation of a network between the LiCoO -CB particles. Compared with the EEC-ET results shown in FIG. 13, this result shows that the LiCoO ２ -It is consistent that the formation of a network between CB particles progresses.

[0053] The above examples show experimental results using electrical impedance tomography (EIT) that utilizes impedance measurement, but the present invention is not limited to EIT and can also be applied to ECT using capacitance and ERT using only resistance.

[0054] REFERENCE SIGNS LIST 1 Electric tomography device 11 Current application device 12 Multiplexer 13 Container with electrode 14 Electrode 15 Container 16 Connector 17 Display 18 Control device 19 Electric wire 20 Stirrer 21 Control unit 22 Calculation unit 23 Display unit 24 Memory unit

Claims

1. An electrical tomography method for extracting electrical equivalent circuit parameters obtained by electrical measurement of a measurement object and visualizing the distribution of the material properties of the measurement object by inverse problem analysis of electrical tomography of the electrical equivalent circuit parameters.

2. The electrical tomography method according to claim 1, wherein the electrical equivalent circuit parameters are electrical equivalent circuit parameters calculated from electrical elements configured according to the electrical properties of the measurement object.

3. The electrical tomography method according to claim 1, for visualizing at least any two distributions of the material properties, time, and three-dimensional space of the measurement object.

4. An electrical tomography apparatus comprising three or more electrodes, the apparatus comprising: a calculation unit that extracts electrical equivalent circuit parameters obtained by impedance measurement of a measurement object and performs inverse problem analysis of electrical tomography of the electrical equivalent circuit parameters; and a display unit that displays the distribution of the material properties of the measurement object based on the inverse problem analysis.

5. The electrical tomography apparatus according to claim 4, wherein the electrical equivalent circuit parameters are electrical equivalent circuit parameters calculated from electrical elements configured according to the electrical properties of the measurement object.

6. The electrical tomography apparatus according to claim 4, for visualizing at least any two distributions of the material properties, time, and three-dimensional space of the measurement object.

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