Method for measuring the expansion amount of an energy storage device and apparatus for measuring the expansion amount of an energy storage device

Abstract

To measure the amount of expansion of an energy storage device due to charging and discharging. [Solution] The method for measuring the expansion amount of a power storage device includes a first imaging step S20, a charge / discharge step S30, a second imaging step S40, and a calculation step S50. In the first imaging step S20, the right side of the outer casing is imaged in the front-to-back direction when the power storage device has a first amount of stored energy. In the charge / discharge step S30, the power storage device is charged or discharged so that its stored energy changes from a first amount to a second amount of stored energy. In the second imaging step S40, the right side of the outer casing is imaged in the front-to-back direction when the power storage device has a second amount of stored energy. In the calculation step S50, the expansion amount of the outer casing is calculated from the image obtained in the first imaging step S20 and the image obtained in the second imaging step S40.

Description

Technical Field

[0001] The present invention relates to a method for measuring the expansion amount of a power storage device and a device for measuring the expansion amount of a power storage device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-113249 discloses a technique related to a method for evaluating the distance between foils in a flat laminated portion where electrode plates are flatly stacked among electrode bodies of a power storage device. This evaluation method includes a foil distance acquisition step, an average deviation calculation step, a reference distance acquisition step, and an evaluation step. In the foil distance acquisition step, X-ray CT analysis is performed on a flat laminated portion where electrode plates are flatly stacked among electrode bodies of a power storage device. In the foil distance acquisition step, for an evaluation site including a plurality of electrode plates in the flat laminated portion, the distance between foils of electrode foils included in adjacent different-polarity or adjacent same-polarity electrode plates via different polarities is acquired as 10 or more. In the average deviation calculation step, the average value and standard deviation of the acquired foil distances are calculated. In the reference distance acquisition step, an evaluation reference distance obtained by adding three times the above standard deviation to the above average value is acquired. In the evaluation step, it is evaluated whether there is a reference-exceeding foil distance greater than the evaluation reference distance in the acquired foil distance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a power storage device may expand with charge and discharge. The inventor intends to measure the expansion amount of the power storage device due to charge and discharge.

Means for Solving the Problems

[0005] The method for measuring the expansion amount of an energy storage device disclosed herein is a method for measuring the expansion amount of an outer casing of an energy storage device having an outer casing and an electrode body housed in the outer casing due to charging and discharging. The method for measuring the expansion amount of an energy storage device includes: a first imaging step of imaging one side of the outer casing in a direction along the extension direction of that side when the energy storage device is at a first energy storage amount; a charge / discharge step of charging or discharging the energy storage device so that the energy storage amount of the energy storage device changes from a first energy storage amount to a second energy storage amount; a second imaging step of imaging one side of the outer casing in a direction along the extension direction of that side when the energy storage device is at a second energy storage amount; and a calculation step of calculating the expansion amount of the outer casing from the image obtained in the first imaging step and the image obtained in the second imaging step. According to this expansion amount measurement method, the expansion amount of an energy storage device due to charging and discharging can be measured. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic perspective view of an energy storage device. [Figure 2] Figure 2 is a cross-sectional view of AA in Figure 1. [Figure 3] Figure 3 is a schematic diagram of the electrode body. [Figure 4] Figure 4 is a flowchart showing an example of a method for measuring the expansion amount of an energy storage device. [Figure 5] Figure 5 is a schematic diagram of the expansion amount measuring device. [Figure 6] Figure 6 is a schematic plan view of the expansion amount measuring device. [Figure 7] Figure 7 is a graph showing an example of the intensity distribution of X-ray transmitted light obtained in the first imaging step. [Figure 8] Figure 8 shows the graph obtained by differentiating the graph in Figure 7 with respect to the horizontal position. [Modes for carrying out the invention]

[0007] Hereinafter, an embodiment of the technology disclosed herein will be described with reference to the drawings. The embodiment described herein is, of course, not intended to particularly limit the present invention. Furthermore, components and parts that perform the same function will be appropriately denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In the drawings, the numerals X, Y, and Z represent the front-to-back, left-to-right, and up-to-down directions, respectively. The left-to-right direction is perpendicular to the front-to-back direction. The up-to-down direction is perpendicular to both the front-to-back and left-to-right directions. In the drawings, the numerals F, Rr, L, R, U, and D mean front, back, left, right, up, and down, respectively. The notation "A~B" indicating a numerical range means "A or greater and B or less" unless otherwise specified.

[0008] In this specification, "energy storage device" refers to a device capable of charging and discharging. Energy storage devices include batteries generally referred to as lithium-ion batteries and lithium secondary batteries, as well as batteries such as lithium polymer batteries and nickel-metal hydride batteries. A secondary battery refers to a battery in general that can be repeatedly charged and discharged by the movement of charge carriers between the positive and negative electrodes. Energy storage devices may use either an electrolyte or a solid electrolyte. For example, a secondary battery may be a secondary battery using a so-called liquid electrolyte, or a so-called all-solid-state battery using a solid electrolyte. Energy storage devices also include capacitors such as electric double-layer capacitors and lithium-ion capacitors.

[0009] Figure 1 is a schematic perspective view of the energy storage device 10. Figure 2 is a cross-sectional view of AA in Figure 1. In Figure 2, the electrode body 20 is shown in a partially broken section. The energy storage device 10 comprises a case 11 and an electrode body 20.

[0010] Case 11 comprises an outer casing 12 and a sealing plate 14. The outer casing 12 is formed in a substantially rectangular parallelepiped shape. The outer casing 12 has a bottom surface 12a, a right side surface 12b, a left side surface 12c, a front side surface 12d, and a rear side surface 12e. The bottom surface 12a extends in the front-rear and left-right directions. The right side surface 12b extends upward from the right end of the bottom surface 12a. The left side surface 12c extends upward from the left end of the bottom surface 12a. The right side surface 12b and the left side surface 12c face each other in the left-right direction. The right side surface 12b is an example of one side surface of the outer casing 12. The left side surface 12c is an example of an opposing surface of the outer casing 12. The front side surface 12d extends upward from the front end of the bottom surface 12a. The front side surface 12d connects the front end of the right side surface 12b and the front end of the left side surface 12c. The rear side surface 12e extends upward from the rear end of the bottom surface 12a. The rear side surface 12e connects the rear end of the right side surface 12b and the rear end of the left side surface 12c. The front side surface 12d and the rear side surface 12e face each other in the front-rear direction. The upper part of the exterior body 12 is open. The exterior body 12 is made of, for example, aluminum or an aluminum alloy, in order to reduce weight and ensure the required rigidity.

[0011] The sealing plate 14 is fitted into the opening of the outer casing 12. The sealing plate 14 closes the opening of the outer casing 12. The sealing plate 14 is joined to the outer casing 12 by means of welding, for example. By joining the sealing plate 14 to the outer casing 12, the inside of the case 11 is sealed. The sealing plate 14 constitutes the top surface of the case 11. The sealing plate 14 may be made of the same material as the outer casing 12. The sealing plate 14 may be made of aluminum or an aluminum alloy, for example, from the viewpoint of reducing weight and ensuring the required rigidity. The sealing plate 14 is provided with a gas discharge valve 15, a positive terminal 16, and a negative terminal 17.

[0012] The gas discharge valve 15 is located in the center of the sealing plate 14 in the front-to-back direction. The gas discharge valve 15 ruptures when the internal pressure of the case 11 rises above a predetermined value. As a result, when the internal pressure of the case 11 exceeds a predetermined value, the gas inside the case 11 is discharged to the outside of the case 11.

[0013] The positive terminal 16 and the negative terminal 17 are provided in pairs at both ends of the sealing plate 14 in the front-rear direction. In the configuration shown in Figure 1, the positive terminal 16 is positioned in front of the negative terminal 17. The positive terminal 16 comprises an external terminal 16a and an internal terminal 16b. The external terminal 16a is attached to the upper side of the sealing plate 14 via a gasket 19a. The internal terminal 16b is attached to the lower side of the sealing plate 14 via an insulator 19b. The internal terminal 16b extends in the vertical direction. The internal terminal 16b is electrically connected to the electrode body 20 inside the case 11.

[0014] The negative terminal 17 comprises an external terminal 17a and an internal terminal 17b. The external terminal 17a is attached to the upper side of the sealing plate 14 via a gasket 19a. The internal terminal 17b is attached to the lower side of the sealing plate 14 via an insulator 19b. The internal terminal 17b extends in the vertical direction. The internal terminal 17b is electrically connected to the electrode body 20 inside the case 11.

[0015] Figure 3 is a schematic diagram of the electrode body 20. The electrode body 20 in this embodiment is a so-called wound electrode body. The electrode body 20 comprises a long positive electrode sheet 21, a long negative electrode sheet 22, and sheet-shaped separators 24 and 25. The electrode body 20 is formed by winding the positive electrode sheet 21, separators 24 and 25 and the negative electrode sheet 22 in a superimposed state in the longitudinal direction around a winding axis WL to form a flattened shape. As shown in Figure 2, the electrode body 20 is housed inside the case 11. As shown in Figure 2, the electrode body 20 is positioned inside the case 11 such that the winding axis WL is substantially parallel to the front-rear direction. Therefore, in the configuration shown in Figure 2, the positive electrode sheet 21 and the negative electrode sheet 22 are stacked in the left-right direction. That is, in the configuration shown in Figure 2, the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22 is the left-right direction. A pair of right-side surfaces 12b and left-side surfaces 12c are located on both sides in the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22. However, the configuration of the electrode body 20 is not limited to this. The electrode body 20 may be a so-called laminated electrode body, for example, in which a plurality of rectangular positive electrode sheets 21 and a plurality of rectangular negative electrode sheets 22 are stacked in an insulated manner.

[0016] As shown in Figure 3, the positive electrode sheet 21 comprises a foil-shaped positive electrode current collector 21a and a positive electrode active material layer 21b formed along the longitudinal direction on both sides of the positive electrode current collector 21a. The positive electrode active material layer 21b contains various materials such as positive electrode active material, binder, and conductive material. On one side edge of the electrode body 20 in the front-to-back direction of the energy storage device 10, the positive electrode active material layer 21b is not formed, and an unformed portion 21a1 is provided where the positive electrode current collector 21a is exposed. Multiple positive electrode tabs 21t are intermittently provided in the unformed portion 21a1 at predetermined positions along the longitudinal direction of the positive electrode sheet 21. Each of the multiple positive electrode tabs 21t protrudes toward the front-to-back direction of the positive electrode sheet 21. In the configuration shown in Figure 2, the multiple positive electrode tabs 21t are arranged so that their positions are aligned when the sheet is wound. The positive electrode tab 21t is electrically connected to the internal terminal 16b of the positive electrode terminal 16.

[0017] The negative electrode sheet 22 includes a foil-shaped negative electrode current collector 22a and a negative electrode active material layer 22b formed along the longitudinal direction on one or both sides of the negative electrode current collector 22a. The negative electrode active material layer 22b contains various materials such as a negative electrode active material and a binder. On the other side edge portion of the electrode body 20 in the front-back direction of the power storage device 10, an unformed portion 22a1 where the negative electrode active material layer 22b is not formed and the negative electrode current collector 22a is exposed is provided. A plurality of negative electrode tabs 22t are intermittently provided at predetermined positions along the longitudinal direction of the negative electrode sheet 22 in the unformed portion 22a1. The plurality of negative electrode tabs 22t each protrude in the front-back direction of the negative electrode sheet 22. In the form shown in FIG. 2, the plurality of negative electrode tabs 22t are arranged so that their positions are aligned in the wound state. The negative electrode tab 22t is electrically connected to the internal terminal 17b of the negative electrode terminal 17.

[0018] The separators 24 and 25 are interposed between the positive electrode sheet 21 and the negative electrode sheet 22 to prevent the positive electrode sheet 21 and the negative electrode sheet 22 from coming into direct contact. Although not shown, a plurality of fine holes are formed in the separators 24 and 25. These fine holes are configured to allow charge carriers to move between the positive electrode sheet 21 and the negative electrode sheet 22. Note that a charge carrier is a particle that carries a charge. For example, in the case of a lithium-ion secondary battery, the charge carrier is a lithium ion. A resin sheet or the like having required heat resistance is used for the separators 24 and 25.

[0019] By the way, the power storage device 10 as described above may expand during charging and discharging. The inventor intends to measure the amount of expansion of the power storage device 10 due to charging and discharging.

[0020] FIG. 4 is a flowchart showing an example of a method for measuring the amount of expansion of the power storage device 10. As shown in FIG. 4, the method for measuring the amount of expansion of the power storage device 10 includes a preparation step S10, a first imaging step S20, a charge-discharge step S30, a second imaging step S40, and a calculation step S50. The measurement of the amount of expansion of the power storage device 10 is carried out using the expansion amount measurement device 50. The measurement of the amount of expansion of the power storage device 10 may be performed for the purpose of checking the state of the used power storage device 10, or may be performed as part of an inspection in the manufacturing process of the power storage device 10.

[0021] FIG. 5 is a schematic diagram of the expansion amount measurement device 50. The expansion amount measurement device 50 includes a thermostat 51, a restraint member 53, an imaging device 57, and a calculation device 60. The thermostat 51 is formed in a box shape. Inside the thermostat 51, the power storage device 10 is placed. The thermostat 51 is configured to be able to control the temperature inside the thermostat 51. Although not shown, the thermostat 51 may be provided with, for example, a heater for heating the inside of the thermostat 51, a temperature sensor for measuring the temperature inside the thermostat 51, and a controller for controlling the heater based on the measurement result of the temperature sensor. The thermostat 51 is preferably made of a material having an X-ray transmittance higher than a predetermined value. The thermostat 51 may be made of, for example, a plastic material or may be made of aluminum or the like. Thus, with the power storage device 10 placed inside the thermostat 51, the measurement of the amount of expansion is performed, so that the change in the amount of expansion due to temperature change can be suppressed, and the measurement of the amount of expansion due to charge-discharge can be performed accurately.

[0022] The restraining member 53 is located inside the constant temperature bath 51. The restraining member 53 restrains the energy storage device 10 by pressing the right side 12b and left side 12c of the outer casing 12 from the outside. The configuration of the restraining member 53 is not particularly limited. In the configuration shown in Figure 5, the restraining member 53 comprises a buffer member 54 and a metal plate 55. The buffer member 54 is a member that is pressed against the energy storage device 10. The buffer member 54 is made of a different material from the material that makes up the outer casing 12. The buffer member 54 may be made of, for example, various rubber materials or flexible resin materials. The metal plate 55 is located on the left and right outer sides of the buffer member 54. The metal plate 55 is made of a different material from the material that makes up the buffer member 54. The metal plate 55 may be made of, for example, aluminum.

[0023] The imaging device 57 images one side of the outer casing 12 in a direction along the extension direction of that side, with the energy storage device 10 restrained by the restraining member 53. In the configuration shown in Figure 5, the imaging device 57 images the right side 12b of the outer casing 12 in the front-rear direction. In the configuration shown in Figure 5, the imaging device 57 is located outside the constant temperature chamber 51. In the configuration shown in Figure 5, the imaging device 57 includes a light source 58 that irradiates X-rays in the front-rear direction and an X-ray detector 59 that detects transmitted light of X-rays irradiated from the light source 58. The light source 58 is located in front of the constant temperature chamber 51. The light source 58 generates X-rays and irradiates the X-rays toward the constant temperature chamber 51. The method by which the light source 58 generates X-rays is not particularly limited, and various conventionally known methods can be used. The X-ray detector 59 is located behind the constant temperature chamber 51. Therefore, the constant temperature chamber 51 is located between the light source 58 and the X-ray detector 59 in the front-rear direction. The X-ray detector 59 is a device that detects the intensity of X-rays irradiated from the light source 58 and transmitted through the constant temperature bath 51. The method by which the X-ray detector 59 detects the intensity of X-rays is not particularly limited, and various conventionally known methods can be used.

[0024] The calculation device 60 calculates the amount of expansion of the outer casing 12 due to charging and discharging of the energy storage device 10. The calculation device 60 calculates the amount of expansion of the outer casing 12 from the intensity distribution of X-rays detected by the X-ray detector 59. The calculation device 60 may be composed of a computer, for example, which includes storage, memory, and a processor. The storage stores programs and data necessary for the processor to perform various processes. The memory operates as the processor's work area.

[0025] As shown in Figure 4, the preparation step S10 includes the step S11 of preparing the energy storage device 10, the step S12 of placing the energy storage device 10 on the expansion amount measuring device 50, and the step S13 of aligning the energy storage device 10.

[0026] In step S11, the energy storage device 10 to be measured for expansion is prepared. The energy storage device 10 prepared in step S11 may be new or used. In step S12, the energy storage device 10 prepared in step S11 is placed in the constant temperature bath 51. In step S12, restraining members 53 are attached to the right side 12b and left side 12c of the outer casing 12. In the configuration shown in Figure 5, the energy storage device 10 is placed so that the front side 12d of the outer casing 12 faces the light source 58.

[0027] Figure 6 is a schematic plan view of the expansion amount measuring device 50. In step S13, the light source 58 and the energy storage device 10 are aligned. In step S13, the X-ray light source 58 is aligned so that it is in front of the front side surface 12d of the outer casing 12 and at the same position as the corner of the outer casing 12, which is composed of the front side surface 12d and the right side surface 12b, in the left-right direction. That is, in step S13, the light source 58 and the right end of the outer casing 12 are aligned so that they are at the same position in the left-right direction. Here, "same position" includes cases where they are at exactly the same position and cases where they are at approximately the same position. Alignment may be performed, for example, by irradiating the energy storage device 10 placed in the constant temperature bath 51 with X-rays from the light source 58 and checking whether an appropriate intensity distribution of transmitted X-ray light is obtained.

[0028] In the first imaging step S20, with the energy storage device 10 at a first energy storage level, one side of the casing 12 is imaged in a direction along the extension direction of that side. The first imaging step S20 is performed with the restraint member 53 attached to the casing 12. In the configuration shown in Figure 5, with the restraint member 53 attached to the casing 12, the right side 12b of the casing 12 is imaged in the front-to-back direction. The first imaging step S20 includes step S21, in which X-rays are irradiated along one side of the casing 12, and step S22, in which the transmitted light of the irradiated X-rays is imaged. In the configuration shown in Figure 5, in step S21, X-rays are irradiated along the right side 12b of the casing 12 from front to back. In the configuration shown in Figure 5, in step S22, the intensity of the X-rays that have passed through the constant temperature bath 51 is detected by the X-ray detector 59. As a result, in step S22, the intensity distribution of the transmitted X-ray light in the left-to-right and up-to-down directions is obtained.

[0029] In the charge / discharge step S30, the energy storage device 10 is charged or discharged so that its stored energy level changes from a first stored energy level to a second stored energy level. The charge / discharge step S30 includes step S31 of attaching the energy storage device 10 to the charge / discharge device 65 and step S32 of charging or discharging the energy storage device 10.

[0030] In step S31, the energy storage device 10 is attached to the charge / discharge device 65. In the configuration shown in Figure 5, the energy storage device 10 is attached to the charge / discharge device 65 by connecting the positive terminal 16 to the charge / discharge device 65 with an electrical cable 66, and by connecting the negative terminal 17 to the charge / discharge device 65 with an electrical cable 67. The charge / discharge device 65 is a device that charges or discharges the energy storage device 10. The configuration of the charge / discharge device 65 is not particularly limited. Conventional known charge / discharge devices can be used without any particular restrictions.

[0031] In step S32, the energy storage device 10 is charged or discharged so that its stored energy changes from the first stored energy to the second stored energy. The second stored energy may be greater than or less than the first stored energy. If the second stored energy is greater than the first stored energy, the energy storage device 10 is charged in step S32. If the second stored energy is less than the first stored energy, the energy storage device 10 is discharged in step S32. For example, the first and second stored energy may each be set to predetermined values ​​within the range of 0% to 100% SOC (state of charge). The C rate for charging and discharging in step S32 is not particularly limited.

[0032] In the second imaging step S40, with the energy storage device 10 at a second energy storage level, one side of the casing 12 is imaged in a direction along the extension direction of that side. The second imaging step S40 is performed with the restraint member 53 attached to the casing 12. In the configuration shown in Figure 5, with the restraint member 53 attached to the casing 12, the right side 12b of the casing 12 is imaged in the front-to-back direction. In this embodiment, the second imaging step S40 is performed in the same positional relationship between the energy storage device 10 and the X-ray light source 58 as when the first imaging step S20 was performed. The second imaging step S40 includes a step S41 in which X-rays are irradiated in a direction along one side of the casing 12, and a step S42 in which transmitted light of the irradiated X-rays is detected. In the configuration shown in Figure 5, in step S41, X-rays are irradiated along the right side 12b of the casing 12 from front to back. In the configuration shown in Figure 5, in step S42, the intensity of the X-ray transmitted light that has passed through the constant temperature bath 51 is detected by the X-ray detector 59. As a result, in step S42, the intensity distribution of the X-ray transmitted light in the left-right and up-down directions is obtained.

[0033] The calculation step S50 is performed by the calculation device 60. In the calculation step S50, the amount of expansion of the outer casing 12 is calculated from the image obtained in the first imaging step S20 and the image obtained in the second imaging step S40. In this embodiment, in the calculation step S50, the amount of expansion of the outer casing 12 is calculated from the intensity distribution of the X-ray transmitted light obtained in the first imaging step S20 and the intensity distribution of the X-ray transmitted light obtained in the second imaging step S40.

[0034] The following describes an example of a method for calculating the amount of expansion of the outer casing 12, which is performed in calculation step S50.

[0035] Figure 7 is a graph showing an example of the intensity distribution of X-ray transmitted light obtained in the first imaging step S20. Figure 7 shows the intensity distribution of X-ray transmitted light at a position equivalent to the vertical center of the energy storage device 10 in the vertical direction. The horizontal axis of Figure 7 indicates the position in the left-right direction. The vertical axis of Figure 7 indicates the intensity of X-ray transmitted light at each position in the left-right direction. The outer casing 12 and the buffer member 54 are made of different materials, so they have different X-ray transmittances. Similarly, the buffer member 54 and the metal plate 55 are made of different materials, so they have different X-ray transmittances. Therefore, as shown in Figure 7, the intensity of X-ray transmitted light changes significantly at the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55.

[0036] Figure 8 is a graph obtained by differentiating the graph in Figure 7 with respect to the position in the left-right direction. Therefore, the vertical axis in Figure 8 shows the degree of change in the intensity of transmitted X-ray light at each position in the left-right direction. As described above, the intensity of transmitted X-ray light changes significantly at the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55. Therefore, the degree of change in the intensity of transmitted X-ray light is large at the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55. Consequently, differentiating the graph in Figure 7 with respect to the position in the left-right direction yields a graph with two local maxima, as shown in Figure 8. The left-right positions corresponding to these two local maxima are the positions of the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55. By calculating the positions of the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55 in this way, it is possible to determine the positions of the boundaries of the outer casing 12, the buffer member 54, and the metal plate 55 in the left-right direction.

[0037] As described above, the positions of the boundaries of the exterior body 12, the buffer member 54, and the metal plate 55 at the time of the execution of the first imaging step S20 can be determined from the intensity distribution of the transmitted X-ray light obtained in the first imaging step S20. By performing the same process on the graph of the intensity distribution of the transmitted X-ray light obtained in the second imaging step S40, the positions of the boundaries of the exterior body 12, the buffer member 54, and the metal plate 55 at the time of the execution of the second imaging step S40 can be determined.

[0038] As the energy storage device 10 expands during charging and discharging, the position of the boundary between the outer casing 12 and the buffer member 54 changes. Therefore, by comparing the position of the boundary between the outer casing 12 and the buffer member 54 at the time of the first imaging step S20 with the position of the boundary between the outer casing 12 and the buffer member 54 at the time of the second imaging step S40, the amount of displacement of the boundary between the outer casing 12 and the buffer member 54 can be determined. From this amount of displacement, the amount of expansion of the energy storage device 10 can be calculated.

[0039] According to this embodiment, the method for measuring the expansion amount of the energy storage device 10 includes a first imaging step S20, a charge / discharge step S30, a second imaging step S40, and a calculation step S50. In the first imaging step S20, the right side 12b of the casing 12 is imaged in the front-to-back direction when the energy storage device 10 has a first energy storage amount. In the charge / discharge step S30, the energy storage device 10 is charged or discharged so that its energy storage amount changes from a first energy storage amount to a second energy storage amount. In the second imaging step S40, the right side 12b of the casing 12 is imaged in the front-to-back direction when the energy storage device 10 has a second energy storage amount. In the calculation step S50, the expansion amount of the casing 12 is calculated from the image obtained in the first imaging step S20 and the image obtained in the second imaging step S40. This measurement method allows for non-contact, in-situ measurement of the expansion amount of the energy storage device 10 associated with charging and discharging.

[0040] According to this embodiment, in the first imaging step S20 and the second imaging step S40, the right side surface 12b of the outer casing 12 is imaged in the front-rear direction. The right side surface 12b of the outer casing 12 is one of the sides located on both sides in the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22 of the electrode body 20. Thus, the pair of sides located on both sides in the stacking direction of the positive electrode sheet 21 and the negative electrode sheet 22 are the sides of the outer casing 12 that expand the most. Therefore, since the right side surface 12b of the outer casing 12 is a side that expands easily, it is easy to determine whether the expansion amount of the energy storage device 10 is normal or abnormal by measuring the expansion amount of the right side surface 12b of the outer casing 12.

[0041] According to this embodiment, the first imaging step S20 includes a step S21 of irradiating the right side surface 12b of the outer casing 12 with X-rays in the front-rear direction, and a step S22 of detecting the transmitted light of the X-rays irradiated in step S21. The second imaging step S40 includes a step S41 of irradiating the right side surface 12b of the outer casing 12 with X-rays in the front-rear direction, and a step S42 of detecting the transmitted light of the X-rays irradiated in step S41. In the calculation step S50, the amount of expansion of the outer casing 12 is calculated from the intensity distribution of the transmitted light obtained in the first imaging step S20 and the intensity distribution of the transmitted light obtained in the second imaging step S40. According to this measurement method, the amount of expansion of the outer casing 12 is calculated by detecting the transmitted light of X-rays and comparing its intensity distribution. Therefore, the amount of expansion of the outer casing 12 can be measured with higher accuracy than, for example, measuring from an image captured with visible light. Since X-rays can penetrate the restraining member 53, the amount of expansion can be measured even when the outer casing 12 is restrained by the restraining member 53.

[0042] According to this embodiment, the first imaging step S20 and the second imaging step S40 are performed with a restraining member 53 attached to the outer casing 12 that restrains the right side 12b and left side 12c of the outer casing 12 by pressing them from the outside. This makes it possible to measure the amount of expansion of the outer casing 12 in a state close to the actual usage state in which the energy storage device 10 is restrained as a stack.

[0043] According to this embodiment, the X-ray light source 58 is positioned in front of the front side surface 12d and, in the left-right direction, is positioned approximately at the same location as the corner of the outer casing 12, which is composed of the front side surface 12d and the right side surface 12b. With the light source 58 positioned in this way, the X-rays reach the right side surface 12b with almost no penetration of the front side surface 12d. Therefore, the amount of expansion can be measured with high accuracy.

[0044] The above describes one embodiment of the proposed technology. However, the above-described embodiment is merely an example, and the technology can be implemented in other ways.

[0045] In the above embodiment, the imaging step of imaging one side of the outer casing 12 was performed twice, in the first imaging step S20 and the second imaging step S40. However, the step of imaging one side of the outer casing 12 may be performed three or more times. In this case, the amount of charge stored in the energy storage device 10 in each imaging step should be different from each other.

[0046] In the above embodiment, the amount of expansion was measured with the energy storage device 10 placed in the constant temperature bath 51. However, when measuring the amount of expansion of the energy storage device 10, it is not always necessary to place the energy storage device 10 to be measured inside the constant temperature bath 51. Also, in the above embodiment, the amount of expansion was measured with the restraint member 53 attached to the energy storage device 10. However, the amount of expansion of the energy storage device 10 may be measured when the energy storage device 10 to be measured is not attached to the restraint member 53. Thus, when measuring the amount of expansion when the energy storage device 10 is not placed inside the constant temperature bath 51 and the restraint member 53 is not attached to the energy storage device 10, the measurement can be performed using, for example, a camera. In this case, for example, the calculation device 60 may perform image processing on the image captured by the camera to calculate the displacement of the position of the boundary between the outer casing 12 and the buffer member 54, and then calculate the amount of expansion.

[0047] In the above embodiment, the expansion amount of the energy storage device 10 was measured by measuring the expansion amount of the right side surface 12b of the outer casing 12. However, the expansion amount of the energy storage device 10 may also be measured by measuring the expansion amount of the left side surface 12c of the outer casing 12. When the measurement is performed in this manner, it is preferable that the X-ray light source 58 is positioned at the same location as the left corner of the outer casing 12, which is composed of the front side surface 12d and the left side surface 12c, with respect to the left-right direction.

[0048] The technologies disclosed herein have been described in detail above. Unless otherwise specified, the embodiments and other details mentioned herein do not limit the present invention. Furthermore, the technologies disclosed herein can be modified in various ways, and each component and each process mentioned herein may be omitted or combined as appropriate, unless no particular problems arise. This specification also includes the disclosures described in the following sections.

[0049] Section 1: A method for measuring the amount of expansion of an outer casing due to charging and discharging in an energy storage device having an outer casing and an electrode body housed in the outer casing, A first imaging step is performed in which, with the amount of energy stored in the energy storage device at a first energy storage level, one side of the outer casing is imaged in a direction along the extension direction of that side; A charge / discharge step in which the amount of energy stored in the energy storage device is charged or discharged from the energy storage device so that the amount of energy stored in the energy storage device changes from the first amount of energy stored to the second amount of energy stored, A second imaging step in which, with the amount of energy stored in the energy storage device at the second amount of energy stored, one side of the outer casing is imaged in a direction along the extension direction of that side, A method for measuring the expansion amount of an energy storage device, comprising: a calculation step of calculating the expansion amount of the outer casing from the image obtained in the first imaging step and the image obtained in the second imaging step.

[0050] Section 2: The electrode body is a laminated electrode body in which multiple electrode sheets are stacked, The method for measuring the expansion amount of an energy storage device according to item 1, wherein the aforementioned side surface is one of a pair of side surfaces arranged on both sides of the plurality of electrode sheets in the stacking direction.

[0051] Section 3: The electrode body is formed by winding or folding long electrode sheets in a stacked manner to create a flat shape. The method for measuring the expansion amount of an energy storage device according to item 1, wherein the aforementioned one side is one of a pair of side surfaces arranged on both sides of the electrode sheet in the stacking direction.

[0052] Section 4: The first imaging step and the second imaging step include irradiating the outer casing with X-rays in a direction along one side surface and detecting the transmitted light of the X-rays irradiated in the X-ray irradiation step, The method for measuring the expansion amount of an energy storage device according to any one of items 1 to 3, wherein the calculation step involves calculating the expansion amount of the outer casing from the intensity distribution of transmitted light obtained in the first imaging step and the intensity distribution of transmitted light obtained in the second imaging step.

[0053] Section 5: The method for measuring the expansion amount of an energy storage device according to item 4, wherein the first imaging step and the second imaging step are performed with a restraining member attached to the exterior body so as to restrain one side of the exterior body from the outside.

[0054] Item 6: The exterior body further comprises an opposing surface facing the one side surface, and a front surface connecting the front end of the one side surface and the front end of the opposing surface. The method for measuring the expansion amount of an energy storage device according to claim 4 or 5, wherein the X-ray light source is positioned in front of the front surface and at the same position as the corner of the exterior body composed of the front surface and the one surface, with respect to the direction in which the one surface and the opposing surface are aligned.

[0055] Section 7: A restraining member for restraining an energy storage device having an outer casing and an electrode body housed in the outer casing, With the energy storage device restrained by the restraining member, an imaging device is provided to image one side of the outer casing in a direction along the extension direction of that side. The system includes a calculation device for calculating the amount of expansion of the outer casing due to charging and discharging of the energy storage device, The calculation device is, An energy storage device expansion amount measuring device that calculates the expansion amount of the outer casing from a first image taken by the imaging device of one side of the outer casing when the energy storage device has a first amount of stored energy, and a second image taken by the imaging device of one side of the outer casing when the energy storage device has a second amount of stored energy.

[0056] Section 8: The imaging device includes a light source that irradiates X-rays in a direction along one side of the outer casing, and an X-ray detector that detects transmitted light of X-rays irradiated from the light source. The calculation device calculates the amount of expansion of the outer casing from the intensity distribution of transmitted light in the first image and the intensity distribution of transmitted light in the second image, as described in item 7, for measuring the amount of expansion of an energy storage device. [Explanation of symbols]

[0057] 10 Energy storage devices 12 Exterior 12b Right side (one side) 12c Left side (opposite side) 12d Anterior side 20 Electrode body 21 Positive electrode sheet (electrode sheet) 22. Negative electrode sheet (electrode sheet) 50 Expansion Amount Measuring Device 53 Restraining member 57 Imaging device 58 Light source 59 X-ray detector 60 Calculation device S20 First imaging step S30 Charge / Discharge Step S40 Second imaging step S50 Calculation Step

Claims

1. A method for measuring the amount of expansion of an outer casing due to charging and discharging in an energy storage device having an outer casing and an electrode body housed in the outer casing, A first imaging step in which, with the amount of energy stored in the energy storage device at a first energy storage level, one side of the outer casing is imaged in a direction along the extension direction of that side; A charge / discharge step in which the energy storage device is charged or discharged so that the amount of energy stored in the energy storage device changes from the first amount of energy to the second amount of energy, A second imaging step in which, with the amount of energy stored in the energy storage device at the second amount of energy stored, one side of the outer casing is imaged in a direction along the extension direction of that side, A method for measuring the expansion amount of an energy storage device, comprising: a calculation step of calculating the expansion amount of the outer casing from the image obtained in the first imaging step and the image obtained in the second imaging step.

2. The electrode body is a laminated electrode body in which multiple electrode sheets are stacked, The method for measuring the expansion amount of an energy storage device according to claim 1, wherein the aforementioned side surface is one of a pair of side surfaces arranged on both sides in the stacking direction of the plurality of electrode sheets.

3. The electrode body is formed by winding or folding long electrode sheets in a stacked manner to create a flat shape. The method for measuring the expansion amount of an energy storage device according to claim 1, wherein the aforementioned side surface is one of a pair of side surfaces arranged on both sides of the electrode sheet in the stacking direction.

4. The first imaging step and the second imaging step include irradiating the outer casing with X-rays in a direction along one side surface and detecting the transmitted light of the X-rays irradiated in the X-ray irradiation step, The method for measuring the expansion amount of an energy storage device according to claim 1, wherein the calculation step involves calculating the expansion amount of the outer casing from the intensity distribution of transmitted light obtained in the first imaging step and the intensity distribution of transmitted light obtained in the second imaging step.

5. The method for measuring the expansion amount of an energy storage device according to claim 4, wherein the first imaging step and the second imaging step are performed with a restraining member attached to the exterior body so as to restrain one side of the exterior body from the outside.

6. The exterior body further comprises an opposing surface facing the one side surface, and a front surface connecting the front end of the one side surface and the front end of the opposing surface. The method for measuring the expansion amount of an energy storage device according to claim 4, wherein the X-ray light source is positioned in front of the front surface and at the same position as the corner of the exterior body composed of the front surface and the one surface, with respect to the direction in which the one surface and the opposing surface are aligned.

7. A restraining member for restraining an energy storage device having an outer casing and an electrode body housed in the outer casing, With the energy storage device restrained by the restraining member, an imaging device is provided to image one side of the outer casing in a direction along the extension direction of that side. The system includes a calculation device for calculating the amount of expansion of the outer casing due to charging and discharging of the energy storage device, The calculation device is, An expansion amount measuring device for a power storage device, which calculates the expansion amount of the outer casing from a first image taken by the imaging device of one side of the outer casing when the power storage device has a first amount of stored energy, and a second image taken by the imaging device of one side of the outer casing when the power storage device has a second amount of stored energy.

8. The imaging device includes a light source that irradiates X-rays in a direction along one side of the outer casing, and an X-ray detector that detects transmitted light of X-rays irradiated from the light source. The device for measuring the expansion amount of an energy storage device according to claim 7, wherein the calculation device calculates the expansion amount of the outer casing from the intensity distribution of transmitted light in the first image and the intensity distribution of transmitted light in the second image.

Images