Method for determining the position of a foil of an electrical storage device and method for calculating the distance between foils of an electrical storage device

Abstract

A method for determining the foil position of an energy storage device and a method for calculating the inter-foil distance of an energy storage device are disclosed. The method comprises: an analysis step, performing X-ray CT analysis to obtain the X-ray absorption at each position; an acquisition step, obtaining the X-ray absorption at each position on a specific virtual trajectory through which the electrode plate passes; and a foil position determination step, determining the foil position of the electrode foil through which the specific virtual trajectory passes based on the X-ray absorption on the trajectory. The foil position determination step includes: a fitting step, defining an approximate curve that varies accordingly with changes in the X-ray absorption on the trajectory within a fitting region and generates a single peak within the fitting region; and a foil position inference step, inferring the position on the trajectory corresponding to the single peak in the defined approximate curve as the foil position of a single electrode foil.

Description

Technical Field

[0001] This invention relates to a method for determining the foil position of the electrode foil of the electrode plate in an energy storage device, and a method for calculating the foil distance of an energy storage device using the method to calculate the foil distance between electrode foils of the same electrode or adjacent opposite electrodes separated by opposite electrodes. Background Technology

[0002] There are situations where it is desirable to analyze and inspect the internal structure of energy storage devices, such as lithium-ion batteries, in a non-destructive manner. For example, there are situations where it is desirable to detect the appropriateness of the stacking state of the electrode plates (positive and negative plates) that form the electrode body of the energy storage device, the change of the stacking state over time, the distance between the electrodes, and the change of the distance over time.

[0003] In such cases, X-ray CT analysis may be performed using a computed tomography (CT) device that utilizes X-rays. For example, Patent Document 1 illustrates an example in which the spectral profile of a secondary battery is obtained through X-ray CT analysis, and the foil positions of the positive and negative electrode foils of the multiple positive and negative electrode plates of the secondary battery can be determined.

[0004] Patent Document 1: International Publication No. 2020 / 031431

[0005] However, due to the large size of the energy storage device, it is necessary to increase the distance from the X-ray source to the energy storage device to be inspected. As a result, there are cases where the positional resolution of the X-ray absorption at each location obtained by X-ray CT analysis is low. In other words, due to reasons such as the high energy of the irradiated X-rays and low contrast, the peaks indicating the foil positions of the positive and negative electrode foils are not clearly shown in the obtained cross-sectional images and spectral profiles that represent the amount of X-ray absorption. The foil positions of the electrode foils included in the electrode plate cannot be clearly determined by cross-sectional images and spectral profiles alone. Summary of the Invention

[0006] The present invention was made in view of the present situation, and provides a method for determining the foil position of an energy storage device that can appropriately determine the foil position of the electrode foil included in the electrode plate of the energy storage device, and a method for calculating the foil distance of an energy storage device that uses the method to calculate the foil distance between electrode foils of the same electrode or adjacent opposite electrodes separated by opposite electrodes.

[0007] One aspect (1) of the present invention for solving the above-mentioned problems is a method for determining the foil position of a storage device, wherein the method comprises: an analysis step, performing X-ray CT analysis of the storage device to obtain the X-ray absorption at each position of the storage device; an acquisition step, based on the acquired X-ray absorption, obtaining the trajectory X-ray absorption at each position on a specific virtual trajectory through which the electrode plate of the storage device passes; and a foil position determination step, based on the acquired trajectory X-ray absorption, determining the foil position of the electrode foil of the electrode plate through which the specific virtual trajectory passes, wherein the foil position determination step comprises: a fitting step, defining an approximate curve that changes accordingly with respect to the change in the trajectory X-ray absorption in a fitting region of the specific virtual trajectory that includes a single electrode foil, and generating a single peak in the fitting region; and a foil position inference step, inferring the position on the trajectory in the fitting region of the specific virtual trajectory that corresponds to the single peak in the defined approximate curve as the foil position of the single electrode foil.

[0008] According to the above-described method for determining the foil position of an energy storage device, in the fitting process, an approximate curve that generates a single peak within the fitting region is defined. In the foil position inference process, the position on the trajectory corresponding to the single peak in the approximate curve is inferred as the foil position of a single electrode foil within the fitting region. In this way, the foil position of the electrode foil on the electrode plate can be appropriately determined.

[0009] Examples of energy storage devices used in X-ray CT analysis include secondary batteries such as lithium-ion batteries and capacitors such as lithium-ion capacitors. The electrode bodies included in the energy storage devices can be any type of stacked electrode body or wound electrode body (cylindrical wound electrode body, flat wound electrode body). The "electrode plates" that are the objects of inspection include, for example, positive electrode plates, negative electrode plates, and bipolar electrode plates.

[0010] (2) can also be configured as follows: based on the foil position determination method of the energy storage device in (1) above, the specific virtual trajectory is a straight line and is a virtual trajectory that is perpendicular to the electrode foil of the electrode plate that is penetrated by the specific virtual trajectory. The electrode plate has an electrode layer of the same thickness on both sides of the electrode foil. The approximate curve of the fitting process is a curve that is symmetrical about the position on the trajectory corresponding to the single peak.

[0011] In the foil position determination method described above, the specific virtual trajectory is a straight line that runs perpendicularly through the electrode foil relative to the electrode plate. Therefore, the change in X-ray absorption along the trajectory within the fitting region represents the difference in the composition (X-ray absorption coefficient) of different parts of the electrode plate in the thickness direction. Furthermore, the approximate curve is set as a curve symmetrical about the position on the trajectory corresponding to a single peak (a left-right symmetrical curve). Therefore, by inferring the position on the trajectory corresponding to the single peak of this approximate curve as the foil position of a single electrode foil, the foil position can be determined with good accuracy.

[0012] Furthermore, as approximating curves, those centered on the position of the trajectory that becomes a single peak can be exemplified by, for example, the Gaussian function, the Lorentz function, the quadratic function, the cosine function, etc.

[0013] (3) It can also be configured as follows: based on the foil position determination method of the energy storage device in (1) or (2) above, the electrode plate is the electrode plate of one of the positive electrode plate and the negative electrode plate, the electrode foil is the electrode foil of one of the positive electrode foil and the negative electrode foil, the specific virtual trajectory passes through multiple electrode foils of the one electrode, the foil position determination process performs the fitting process and the foil position inference process on each electrode foil of the one electrode, and determines the foil position of the electrode foil of the one electrode for each electrode foil of the one electrode, and also includes another foil position inference process, in which the foil position of the other electrode foil located between the adjacent electrode foils of the one electrode is inferred based on a pair of foil positions determined for the adjacent electrode foils of the one electrode.

[0014] When the positive electrode layer of the positive plate uses an alkali metal transition metal oxide such as LiNiO3, while the negative electrode layer uses a carbon-based material such as graphite, the X-ray absorption of the positive electrode layer is relatively large, and the X-ray absorption of the negative electrode layer is relatively small. If X-ray CT analysis is performed on an energy storage device with such positive and negative electrodes to obtain the X-ray absorption at various locations of the device, the X-ray absorption is large at the positive electrode layer of the positive electrode, showing a clear peak, while the X-ray absorption is small at the negative electrode layer of the negative electrode, and it is not easy to obtain a clear peak.

[0015] Therefore, it is relatively easy to determine the foil position of the positive electrode based on the X-ray absorption at each location obtained from X-ray CT analysis, and to determine the position of the positive electrode foil (e.g., sandwiched between two positive electrode layers) based on the position of the positive electrode layer of the positive electrode (where the X-ray absorption becomes larger). However, there are cases where, even after determining the foil position of the negative electrode, it is difficult to determine the position of the negative electrode foil (e.g., sandwiched between two negative electrode layers) based on the position of the negative electrode layer of the negative electrode (where the X-ray absorption becomes smaller).

[0016] In contrast, by using the foil position determination method of (3) above, in addition to being able to properly determine the foil position of multiple electrode foils of one pole, it is also possible to easily infer the foil position of the electrode foil of the other pole whose electrode plates are sandwiched between the electrode plates of one pole.

[0017] As another foil position estimation process, an example method can be given as follows: when the positive electrode plate has a positive electrode layer of the same thickness on both sides of the positive electrode foil, the negative electrode plate has a negative electrode layer of the same thickness on both sides of the negative electrode foil, and the separator sandwiched between the positive and negative electrode plates is also of the same thickness, the position of the midpoint of the estimated positive electrode foil position on a specific virtual trajectory is estimated as the negative electrode foil position of the negative electrode foil. However, it is not limited to this; any method that can appropriately estimate the foil position of the electrode foil of the other electrode plate from the foil position of the electrode plate of one electrode plate based on the layer structure and thickness of the positive and negative electrode plates used in the energy storage device, the thickness of the separator, and the assumed specific virtual trajectory is acceptable.

[0018] (4) Another form is a method for calculating the inter-foil distance of an energy storage device. This method includes an inter-foil distance calculation step. In this inter-foil distance calculation step, the inter-foil distance between the electrode foils that are adjacent to each other or adjacent to opposite poles is calculated by using the foil position of the electrode foil determined by any of the above-mentioned (1) to (3) methods for determining the foil position of the energy storage device.

[0019] According to the method for calculating the inter-foil distance of the energy storage device, even if the energy storage device has changes in X-ray absorption on an unclear trajectory, the foil position of each electrode foil can be properly determined by X-ray CT analysis alone, and the inter-foil distance between electrode foils that are adjacent to opposite poles or adjacent opposite poles can be properly calculated. Attached Figure Description

[0020] Figure 1 This is a flowchart of each step in the method for determining the foil position of the battery and the method for calculating the distance between foils involved in the implementation method.

[0021] Figure 2 This is an explanatory diagram illustrating the use of an X-ray CT analysis apparatus in the analysis process to perform X-ray CT analysis of a battery and obtain the X-ray absorption at each location, as per the implementation method.

[0022] Figure 3 This is an explanatory diagram showing the layer structure of the electrode body in the inspected area of ​​the battery according to the embodiment.

[0023] Figure 4This is an example of a cross-sectional image of a battery made from the X-ray absorption at various locations obtained through X-ray CT analysis.

[0024] Figure 5 This is an example of an implementation method that includes a graph of X-ray absorption at each position on a specific virtual trajectory in a battery, the foil position of each electrode, and the distance between foils.

[0025] Figure 6 It is an explanatory diagram, as described in the embodiment, showing the X-ray absorption curves, approximate curves, and inferred foil positions at each position on the trajectory within the fitting region.

[0026] Explanation of reference numerals in the attached figures

[0027] 10…Battery (energy storage device); 21…Positive electrode plate; 22…Positive electrode foil; 23a, 23b…Positive electrode layer; 23at, 23bt…(Thickness of positive electrode layer); 25…Negative electrode plate; 26…Negative electrode foil; 27a, 27b…Negative electrode layer; P(r, θ, z)…Position; AB(r, θ, z)…X-ray absorption; HT…Specific virtual trajectory; d…Position on the trajectory; AB(d)…X-ray absorption on the trajectory; AF, AF1, AF2, …, AF6, …, AF9…Fitting region; FC, FC6…Approximate curve; FCP, FCP6…(Approximate curve of… Single peak value; dpf, dpf1, dpf2, ..., dpf6, ..., dpf8... (positive electrode foil) foil position; dnf, dnf1, dnf2, ..., dnf7... (negative electrode foil) foil position; DP, DP1, DP2, ..., DP7... (positive electrode foil to each other) foil distance; S1... analysis process; S2... acquisition process; S3... positive electrode foil position determination process (foil position determination process); S32... fitting process; S33... positive electrode foil position inference process (foil position inference process); S4... negative electrode foil position inference process (other electrode foil position inference process); S5... foil distance calculation process. Detailed Implementation

[0028] Hereinafter, embodiments of the present technology will be described with reference to the accompanying drawings. Figure 1 The diagram shows flowcharts of each step in the method for determining the foil position and calculating the inter-foil distance of the battery 10 according to this embodiment. Figure 2As shown, the X-ray CT analysis apparatus XCT for determining the foil position and calculating the inter-foil distance of battery 10 includes an X-ray source SX that emits X-rays in a conical shape from the X-ray focus SXO, an X-ray detector DX that detects the X-rays emitted from the X-ray source SX, and a rotary stage RB that holds the object to be inspected (battery 10 in this example) and rotates about the rotation axis AX. It also includes a processing computer CMP and a monitor MN. The processing computer CMP controls these components and, based on the intensity data of the X-rays detected by the X-ray detector DX, calculates the X-ray absorption AB(r, θ, z) at each position P(r, θ, z) of battery 10, a cross-sectional image showing the distribution of X-ray absorption AB at an arbitrary virtual cross-section, and a graph (absorption distribution map) showing the change of X-ray absorption AB along an arbitrary specific virtual trajectory HT. The monitor MN displays the obtained data, cross-sectional images, and absorption distribution maps.

[0029] In this embodiment, firstly, in the analysis process S1, an X-ray CT analysis device (XCT) is used to perform X-ray CT analysis on the battery 10, which is the object to be inspected. In the processing computer (CMP), the X-ray absorption amount AB(r, θ, z) at each position P(r, θ, z) (where (r, θ, z) represents the coordinates in the cylindrical inspection area 10S irradiated by X-rays, indicated by the dashed line, is obtained in the battery 10.

[0030] Furthermore, the ratio of the first distance SRD from the X-ray focus SXO to the rotation axis AX to the second distance SDD from the X-ray focus SXO to the X-ray detector DX is the magnification R (R = SDD / SRD). Generally, the larger the magnification R, the higher the resolution of the X-ray absorption AB(r, θ, z). Due to the constraints of the overall shape of the X-ray CT resolving apparatus XCT, the second distance SDD is usually a fixed size. On the other hand, the first distance SRD can be changed by changing the position of the rotating stage RB. In cases where the size of the object being inspected (e.g., battery 10) is large, when the battery 10 is rotated on the rotating stage RB, in order to avoid interference between the battery 10 and the X-ray source SX, the first distance SRD must be increased, thereby decreasing the magnification R and lowering the resolution of the calculated X-ray absorption AB(r, θ, z). Furthermore, if the object being inspected (e.g., battery 10) is large, the distance X-rays travel through the object increases, resulting in a lower overall intensity of X-rays reaching the X-ray detector DX. Consequently, the resolution of X-ray absorption AB(r, θ, z) tends to decrease in this respect. If, to prevent this, the energy of the X-rays emitted from the X-ray focus SXO of the X-ray source SX is increased, the contrast in intensity of the X-rays reaching the X-ray detector DX decreases. In this case, the resolution of X-ray absorption AB(r, θ, z) also tends to decrease.

[0031] Therefore, for example, such as Figure 3 As shown, when X-ray CT analysis was performed on the portion of the stacked electrode body 20 of the battery 10 where positive electrode plates 21 and negative electrode plates 25 are alternately stacked with spacers 29, for example, it was found that... Figure 4 An example of a cross-sectional image of battery 10 with lower resolution, as shown.

[0032] In addition, such as Figure 3 As shown, the positive electrode plate 21 is composed of a positive electrode foil 22 and positive electrode layers 23a and 23b of equal thickness formed on both sides thereof. The positive electrode foil 22 is made of aluminum. The positive electrode layers 23a and 23b contain, for example, a positive electrode active material, which includes LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3Transition metal elements such as O2 are present, thus exhibiting a higher X-ray absorption coefficient than the positive electrode foil 22. On the other hand, the negative electrode plate 25 is composed of a negative electrode foil 26 and negative electrode layers 27a and 27b of equal thickness formed on both sides thereof, wherein the negative electrode foil 26 is made of copper. The negative electrode layers 27a and 27b contain, for example, a large amount of negative electrode active material composed of carbon-based materials such as graphite, and therefore have a relatively lower X-ray absorption coefficient compared to the negative electrode foil 26, the positive electrode foil 22, and the positive electrode layers 23a and 23b. The separator 29, made of polyethylene or the like, also similarly has a low X-ray absorption coefficient.

[0033] Therefore, in Figure 4 In the cross-section, the portions of the positive electrode plate 21 containing the positive electrode layers 23a and 23b with high X-ray absorption at each position P(r, θ, z) are shown relatively in white, while the portions of the negative electrode plate 25 containing the negative electrode layers 27a and 27b with low X-ray absorption and the separator 29 are shown relatively in black. Furthermore, the positive electrode foil 22, the negative electrode foil 26, and the separator 29 are thinner (approximately 1 / 10 or less) than the positive electrode layers 23a and 23b and the negative electrode layers 27a and 27b, therefore, according to... Figure 4 The cross-sectional images make it difficult to clearly identify the positive foil 22 and the negative foil 26 to determine their positions.

[0034] Therefore, in the acquisition step S2, the X-ray absorption AB(d) on the trajectory is obtained by processing the computer CMP. This X-ray absorption AB(d) is the X-ray absorption AB(r, θ, z) at each position d on the trajectory of a specific virtual trajectory HT through which the positive electrode plate 21 or negative electrode plate 25, which serves as the electrode plate of the battery 10, is passed. The position d on the trajectory can also be expressed as the distance measured along the specific virtual trajectory HT from any position on the specific virtual trajectory HT as the origin. In this embodiment, the specific virtual trajectory HT is assumed to be used for... Figure 3 , Figure 4 An example of a specific virtual trajectory HT represented by a straight, dotted line extending horizontally and perpendicularly through multiple positive plates 21 and multiple negative plates 25. Figure 3 In this process, the position d on the trajectory of the point where the specific virtual trajectory HT intersects with the positive electrode foil 22 is set as the foil position dpf of the positive electrode foil 22. Similarly, the position d on the trajectory of the point where the specific virtual trajectory HT intersects with the negative electrode foil 26 is set as the foil position dnf of the negative electrode foil 26.

[0035] exist Figure 5 The diagram shows the variation of X-ray absorption AB(d) at position d (distance d from the origin) on each trajectory of a specific virtual trajectory HT (absorption distribution diagram). Figure 5In the graph, besides observing multiple peaks where the X-ray absorption AB(d) value exceeds 150 on the trajectory corresponding to the positive electrode layers 23a and 23b of each positive electrode plate 21 with high X-ray absorption, valleys corresponding to each negative electrode plate 25 with low X-ray absorption are also observed. In each valley, smaller peaks are observed due to the presence of a thin copper negative electrode foil with a high X-ray absorption coefficient. However, a comparison with Figures 7 and 8 of Patent Document 1 shows that, by observing this... Figure 5 The curve diagram makes it difficult to accurately determine the foil position dpf of each positive foil 22 and the foil position dnf of each negative foil 26.

[0036] Therefore, in this embodiment, firstly, in the positive electrode foil position determination step S3, the foil position dpf (e.g., dpf1 to dpf9) of each positive electrode foil 22 is determined as follows. In the region setting step S31, a fitting region AF (in which a single positive electrode foil 22 is included within a specific virtual trajectory HT) is defined. Figure 5 The range is AF1 to AF9. Specifically, in Figure 5 In the curve diagram, the range where the X-ray absorption AB(d) on the trajectory exceeds 100 is set as the fitting region AF1~AF9.

[0037] Next, by repeatedly performing the fitting process S32 and the positive electrode foil position inference process S33 through the repeated judgment process S34, the foil position dpf (e.g. dpf1 to dpf8) of a single positive electrode foil 22 is determined for each fitting region AF (e.g. AF1 to AF9).

[0038] For example, such as Figure 6 As shown, in the fitting process S32, the approximate curve FC6 is specified (in... Figure 6 (Represented by a thick dashed line in the figure) The approximate curve FC6 changes accordingly with respect to the change in X-ray absorption AB(d) on the trajectory in the fitting region AF6, and generates a single peak FCP6 within the fitting region AF6. Furthermore, in this embodiment, a Gaussian function is used for the approximate curve FC6. This is because the positive electrode plate 21 has electrode layers 23a and 23b of equal thickness on both sides of the positive electrode foil 22, so it is appropriate to fit an approximate curve FC6 that is centered on the position d (foil position dpf) on the trajectory corresponding to the single peak FCP6 and symmetrical with respect to a specific virtual trajectory HT (distance d) (left-right symmetry). This allows for accurate determination of the foil position dpf1, etc. Furthermore, as an approximate curve FC that is symmetrical with respect to a specific virtual trajectory HT (distance d), for example, a Lorentz function, a quadratic function, a cosine function, etc., can also be used.

[0039] Next, in the positive electrode foil position inference step S33, the position d on the trajectory corresponding to the single peak FCP6 in the fitting region AF6 and the specified approximate curve FC6 is inferred as the foil position dpf6 of the single positive electrode foil 22.

[0040] Furthermore, in the iterative determination process S34, the fitting process S32 and the positive electrode foil position estimation process S33 are repeatedly performed for each set fitting region AF (e.g., AF1 to AF8) until the approximate curve FC is defined by the fitting process S32 and the foil position dpf position of the positive electrode foil 22 is estimated by the positive electrode foil position estimation process S33. Thus, for each fitting region AF (e.g., AF1 to AF8), the foil position dpf (e.g., dpf1 to dpf8) of the positive electrode foil 22 included in each fitting region AF can be estimated (see reference). Figure 5 In this way, the foil position dpf (e.g., dpf1 to dpf8) of each positive foil 22 in the plurality of positive foils 22 and negative foils 26 can be determined.

[0041] Next, in the negative electrode foil position estimation step S4, the foil positions dpf (e.g., dpf1 to dpf8) of the positive electrode foil 22 determined in the aforementioned positive electrode foil position determination step S3 are used to estimate the foil positions dnf (e.g., dnf1 to dnf7) of each negative electrode foil 26 that is opposite to the positive electrode foil. Specifically, the foil positions dnf (e.g., dnf1) of the negative electrode foil 26 located between adjacent positive electrode foils 22 are estimated based on a pair of foil positions dpf (e.g., a pair of foil positions dpf1 and dpf2) determined for adjacent positive electrode foils 22. Specifically, for example, the position d on the trajectory between the pair of foil positions dpf1 and dpf2 is estimated as the foil position dnf1 of the negative electrode foil 26. This is because the positive electrode layers 23a and 23b have the same thickness, the negative electrode layers 27a and 27b also have the same thickness, and the separator 29 also has a uniform thickness. Similarly, the foil positions dnf2 to dnf7 of each negative electrode foil 26 are inferred from the foil positions dpf2 to dpf8 of the positive electrode foil 22 (refer to...). Figure 5 In this way, in addition to being able to properly determine the foil positions dpf1, etc. of multiple electrode foils of one pole (positive electrode foil 22 in this embodiment), it is also possible to easily deduce the foil position dnf1, etc. of the other electrode foil (negative electrode foil 26 in this embodiment) sandwiched between them.

[0042] Furthermore, in the foil distance calculation step S5, the foil positions dpf1 to dpf8 of the positive electrode foil 22 determined in the positive electrode foil position determination step S3 are used to calculate the foil distances DP1 to DP7 between the positive electrode foils 22 that are adjacent to the negative electrode foil 26 as opposite electrodes, which are of the same polarity. Thus, even for energy storage devices where X-ray absorption varies along unclear trajectories, X-ray CT analysis (see reference) is sufficient. Figure 4 It is also possible to appropriately determine the foil position dpf1 of each electrode foil (positive electrode foil 22 in this embodiment), and to appropriately calculate the foil distance DP1 between adjacent opposite or same electrode foils (positive electrode foils 22 of the same polarity in this embodiment).

[0043] The present invention has been described above according to embodiments, but the present invention is not limited to these embodiments. It is self-evident that appropriate modifications can be made without departing from its spirit. For example, in the embodiments, in each fitting region AF1, etc., an approximate curve FC that varies accordingly with the change in X-ray absorption AB(d) on the trajectory is defined to determine the foil position dpf1, etc., for the positive electrode foil 22. On the other hand, for the foil position dnf1, etc., of the negative electrode foil 26, fitting based on the approximate curve is not used, but it is calculated based on the foil position dpf1, etc., of the positive electrode foil 22. This is because, in Figure 5 In the example shown in the curve diagram, the magnitude of the X-ray absorption AB(d) on the d trajectory is small near the location corresponding to each negative electrode foil 26, making it difficult to properly determine the foil position dnf1 of each negative electrode foil 26 using an approximate curve in the same way as the foil position dpf1 of the positive electrode foil 22.

[0044] However, when the magnitude of the X-ray absorption AB(d) on the trajectory obtained near the location corresponding to each negative electrode foil 26 is large enough that the foil position dnf of each negative electrode foil 26 can be appropriately determined using an approximate curve, it can also be determined using an approximate curve in the same way as the foil position dpf1 of the positive electrode foil 22. In this case, in the foil distance calculation process, the determined foil positions dpf1 of the positive electrode foil 22 and dnf1 of the negative electrode foil 26 can also be used to calculate the foil distance between adjacent opposite positive electrode foils 22 and negative electrode foils 26.

[0045] Additionally, in the implementation method, such as Figure 3 As shown, for the inspected area 10S of the stacked electrode body 20 of battery 10, where the positive electrode plate 21, negative electrode plate 25, and separator 29 are all stacked in a flat shape, X-ray CT analysis was performed, and the foil position dpf1 of each positive electrode foil 22 was determined. Additionally, examples were shown of inferring the foil position dnf1 of each negative electrode foil 26 and calculating the foil distance DP1 between the positive electrode foils 22. However, the same method can also be applied to the flat portion of a flat, wound electrode body where the positive electrode plate, negative electrode plate, and separator are stacked in a flat shape.

[0046] In addition, the same method as in this embodiment can be applied to the R-section of a flat wound electrode body, where the positive electrode plate, negative electrode plate, and separator are bent into a semi-cylindrical shape and stacked, and to a cylindrical wound electrode body to determine the foil position of each positive electrode foil. Furthermore, the foil position of each negative electrode foil can be deduced, and the foil distance between the positive electrode foils can be calculated.

Claims

1. A method for determining the foil position of an energy storage device (10), wherein, The method for determining the foil position of the energy storage device (10) includes: In the analysis process (S1), X-ray CT analysis of the energy storage device (10) equipped with electrode plates (21, 25) is performed to obtain the X-ray absorption (AB(r, θ, z)) at each position of the energy storage device (10), wherein the electrode plates (21, 25) have electrode foils (22, 26). In the acquisition process (S2), based on the acquired X-ray absorption (AB(r, θ, z)), the X-ray absorption at each trajectory position (d) on a specific virtual trajectory (HT) through which the electrode plates (21, 25) of the energy storage device (10) are acquired (AB(d)); and In the foil position determination process (S3), based on the obtained X-ray absorption amount (AB(d)) on the trajectory, the foil position (dpf, dnf) of the electrode foil (22, 26) of the electrode plate (21, 25) through which the specific virtual trajectory (HT) passes is determined. The foil position determination process (S3) includes: The fitting process (S32) defines an approximate curve (FC6) that varies accordingly with respect to the change in X-ray absorption (AB(d)) on the trajectory within a fitting region (AF6) that includes a single electrode foil (22) in the specific virtual trajectory (HT), and produces a single peak (FCP6) within the fitting region (AF6); and In the foil position inference step (S33), the position (d) on the trajectory corresponding to the single peak (FCP6) in the fitting region (AF6) of the specific virtual trajectory (HT) is inferred as the foil position (dpf6) of the single electrode foil (22). The specific virtual trajectory (HT) is a straight line and is a virtual trajectory that passes perpendicularly to the electrode foil (22) of the electrode plate (21) through which the specific virtual trajectory (HT) passes.

2. The method for determining the foil position of the energy storage device (10) according to claim 1, wherein, The electrode plate (21) has electrode layers (23a, 23b) of the same thickness on both sides of the electrode foil (22). The approximate curve (FC6) in the fitting process (S32) is a curve symmetrical about the specific virtual trajectory (HT) with the position (dpf6) on the trajectory corresponding to the single peak (FCP6) as the center.

3. The method for determining the foil position of the energy storage device (10) according to claim 1 or 2, wherein, The electrode plates (21, 25) are multiple electrode plates (21) of one of the positive electrode plate (21) and the negative electrode plate (25). The electrode foils (22, 26) are multiple electrode foils (22) of one of the positive electrode foils (22) and the negative electrode foils (26). The specific virtual trajectory (HT) runs through the electrode foil (22) of multiple poles. The foil position determination process (S3) is configured as follows: The fitting process (S32) and the foil position inference process (S33) are performed on each of the electrode foils (22) of the first pole to determine the foil position (dpf) of the electrode foil (22) of the first pole. It also includes a second electrode foil position inference step (S4), in which the foil position (dnf) of the other electrode foil (26) located between the adjacent electrode foils (22) is inferred based on a pair of foil positions (dpf) determined for the adjacent electrode foils (22).

4. A method for calculating the inter-foil distance of an energy storage device (10), wherein, The device includes a foil distance calculation step (S5), in which the foil positions (dpf, dnf) of the electrode foils (22, 26) determined by the foil position determination method of the energy storage device (10) according to any one of claims 1 to 3 are used to calculate the foil distance (DP) between the electrode foils (22, 26) that are adjacent to each other of the same pole or adjacent to each other of opposite poles.

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