Estimation device, computer program, and estimation method

Abstract

To provide an estimation device, computer program and estimation method, capable of estimating a shape change in a power storage element.SOLUTION: An estimation device includes a determination section for determining whether a shape change mode of a power storage element is a first mode or a second mode and an estimation section for estimating a shape change of the power storage element according to the determined shape change mode.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an estimation device, a computer program, and an estimation method.

Background Art

[0002] In order to configure a battery module from a plurality of cells (single batteries), there are methods such as applying a compressive force with the long side surfaces of the plurality of cells facing each other, and methods of arranging the plurality of cells facing each other in a non-compressed state. In the latter case, the case of the cell may bulge as the battery module is used (charged and discharged).

[0003] Patent Document 1 discloses an electronic device that detects the degree of swelling of a secondary battery by means of swelling detection means provided in the secondary battery and warns the user to prevent damage or performance degradation due to the swelling of the secondary battery.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The swelling of a power storage element such as a secondary battery is considered to be mainly caused by a change in the element structure inside the power storage element or gas generation. In order to prevent damage to the battery module due to the swelling of the power storage element, or to grasp the state change and deterioration accompanying the swelling of the power storage element, it is necessary to examine the physical phenomena inside the power storage element. For example, in order to support model-based development, it is necessary to appropriately estimate the shape change of the power storage element in consideration of the physical phenomena inside the power storage element.

[0006] An object of the present invention is to provide an estimation device, a computer program, and an estimation method for estimating the shape change of a power storage element.

Means for Solving the Problem

[0007] An estimation device according to one aspect of the present invention includes a determination unit that determines whether the shape change mode of a power storage element is a first mode or a second mode, and an estimation unit that estimates the shape change of the power storage element according to the shape change mode determined by the determination unit.

Effect of the Invention

[0008] According to the above aspect, the shape change of the power storage element can be appropriately estimated.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 14

Embodiments for Carrying Out the Invention

[0010] The estimation device includes a determination unit that determines whether the shape change mode of the power storage element is the first mode or the second mode, and an estimation unit that estimates the shape change of the power storage element according to the shape change mode determined by the determination unit.

[0011] The computer program causes the computer to execute a process of determining whether the shape change mode of the power storage element is the first mode or the second mode, and estimating the shape change of the power storage element according to the determined shape change mode.

[0012] The estimation method determines whether the shape change mode of the power storage element is the first mode or the second mode, and estimates the shape change of the power storage element according to the determined shape change mode.

[0013] The determination unit of the above-described estimation device determines whether the shape change mode of the power storage element is the first mode or the second mode. The present inventor has found that there are at least two modes in the shape change of the power storage element. Specifically, the present inventor has found that there are at least two modes in the shape change of the power storage element as a dominant factor in the shape change of the electrode body (element). The determination unit determines whether the shape change mode of the power storage element is the first mode or the second mode based on predetermined conditions.

[0014] The estimation unit estimates the shape change of the power storage element according to the shape change mode determined by the determination unit. By preparing in advance the method for estimating the shape change of the power storage element in each shape change mode, an optimal method can be adopted according to the shape change mode, and the shape change of the power storage element can be accurately estimated.

[0015] The storage element may have a wound electrode body.

[0016] As will be described later, the inventor has found that a storage element having a wound electrode body exhibits a specific shape change mode. By grasping the shape change mode of the storage element having a wound electrode body, the shape change can be accurately estimated. Alternatively, the storage element may have a stacked electrode body.

[0017] The estimation device may perform estimation such that the shape change speed in the second mode shifted from the first mode is greater than the shape change speed in the first mode.

[0018] The shape change speed can be expressed, for example, as (amount of shape change / time) or (amount of shape change / total SOC fluctuation amount). With the above-described configuration, the shape change of the storage element can be accurately estimated before and after the mode transition.

[0019] The estimation device includes a first acquisition unit that acquires or calculates an elapsed parameter related to the elapsed period of the storage element, and the determination unit may determine the shape change mode based on the elapsed parameter acquired or calculated by the first acquisition unit.

[0020] The elapsed parameter related to the elapsed period of the storage element may be any parameter for determining whether the shape change mode of the storage element is either the first mode or the second mode. With the above-described configuration, the shape change of the storage element can be accurately estimated.

[0021] The estimation device includes a second acquisition unit that acquires or calculates an elapsed parameter related to the energization of the storage element, and the determination unit may determine the shape change mode based on the elapsed parameter acquired or calculated by the second acquisition unit.

[0022] The elapsed parameter related to the energization of the storage element may be any parameter for determining whether the shape change mode of the storage element is either the first mode or the second mode. With the above-described configuration, the shape change of the storage element can be accurately estimated.

[0023] The elapsed parameter may include any one of the number of days elapsed when the power storage element is non-energized or energized, the absolute value of the dimensions of the power storage element, the amount of change in the shape of the power storage element, and the total SOC fluctuation amount of the power storage element.

[0024] For example, by formulating the shape change in advance as a function of time, the value of the shape change can be obtained according to the time (number of days elapsed). If the number of days elapsed is equal to or less than the threshold value, it can be determined that the shape change mode is the first mode, and if the number of days elapsed exceeds the threshold value, it can be determined that the shape change mode is the second mode. The function indicating the shape change is different between the first mode and the second mode. The elapsed parameter may be the absolute value of the dimensions of the power storage element, the amount of change in the shape, or the total SOC fluctuation amount. If the absolute value of the dimensions or the amount of change in the shape is equal to or less than the threshold value, it can be determined that the shape change mode is the first mode, and if the absolute value of the dimensions or the amount of change in the shape exceeds the threshold value, it can be determined that the shape change mode is the second mode. Alternatively, if the total SOC fluctuation amount of the power storage element exceeds the threshold value, it can be determined that the shape change mode is the second mode.

[0025] The determination unit may determine the transition from the first mode to the second mode according to at least one of the types of the positive electrode active material and the negative electrode active material of the power storage element.

[0026] In the case of a lithium-ion battery, lithium ions are inserted into or desorbed from the active material during charge and discharge. The shape change rate is different depending on whether at least one of the types of the positive electrode active material and the negative electrode active material is an active material with a large volume change during insertion and desorption or an active material with a small volume change. Therefore, it is preferable to determine the transition from the first mode to the second mode according to the type of the active material. It is considered that power storage elements with different active materials have different transition points from the first mode to the second mode even if their usage environments, dimensions, and element structures are the same.

[0027] The shape change may include a change in the thickness of the wound electrode body.

[0028] The thickness direction is a direction orthogonal to the winding axis direction of the wound electrode body (a direction orthogonal to the long side surface of the power storage element). As will be described later, the inventor has found that the wound electrode body exhibits a specific shape change mode in its thickness direction. With the above configuration, the thickness change of the power storage element can be accurately estimated.

[0029] Hereinafter, embodiments of the estimation device, computer program, and estimation method will be described with reference to the drawings.

[0030] FIG. 1 is a perspective view of a battery module (power storage device) 10. The battery module 10 includes a rectangular parallelepiped case 11, a plurality of cells (power storage elements) 20 housed in the case 11 in a non-compressed state, and the like.

[0031] The cell 20 includes a rectangular parallelepiped (prismatic) cell case 21, a cover plate 22, terminals 23 and 26 provided on the cover plate 22, a rupture valve 24, and an electrode body 25. The terminals 23 and 26 may be welding terminals as shown in FIG. 1 or bolt terminals as shown in FIG. 2. The electrode body 25, also referred to as an element, is formed by winding a positive electrode plate, a separator, and a negative electrode plate in a flat shape by stacking. The longitudinally wound type electrode body 25 is housed in the cell case 21 in a posture where its winding axis direction is parallel to the cover plate 22. The horizontally wound type electrode body 25 is housed in the cell case 21 in a posture where its winding axis direction is orthogonal to the cover plate 22. Alternatively, the electrode body 25 may be a laminated type electrode body.

[0032] The positive electrode plate is formed by forming an active material layer on a positive electrode base material foil which is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of aluminum, an aluminum alloy, or the like. The negative electrode plate is formed by forming an active material layer on a negative electrode base material foil which is a plate-shaped (sheet-shaped) or long strip-shaped metal foil made of copper, a copper alloy, or the like. The separator is a microporous sheet made of a synthetic resin.

[0033] The positive electrode active material may be, for example, a lithium transition metal oxide such as lithium cobaltate, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate (Li1+aMeO2, a≧1, Me: transition metal elements such as Ni, Mn, Co containing one or more), spinel type lithium manganate (LiMe2O4: Me is one or more metal elements containing at least Mn), lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, etc., as long as a material capable of occluding and releasing Li is used. Also, two or more of these may be used in combination.

[0034] The negative electrode active material may be, for example, graphite, hard carbon, soft carbon, metallic Li, silicon monoxide, silicon or its alloy, tin or its alloy, lithium vanadate, tungsten oxide, titanium oxide, niobium oxide, etc., as long as a material capable of occluding and releasing Li is used. Also, two or more of these may be used in combination. If either the positive electrode active material or the negative electrode active material expands with charge and discharge, the present invention can be applied.

[0035] Adjacent terminals 23 and 26 of adjacent cells 20 of the battery module 10 are electrically connected by the bus bar 12, whereby a plurality of cells 20 are connected in series. Leads 14 and 13 for taking out electric power are provided at the terminals 23 and 26 of the cells 20 at both ends of the battery module 10.

[0036] FIG. 2 is a perspective view of the cell 20. The cell case 21 has opposing long side surfaces 21a and 21b, and opposing short side surfaces 21c and 21d. The dimension between the long side surfaces 21a and 12b indicated by the symbol D is referred to as the thickness (thickness), and the dimension between the short side surfaces 21c and 21d indicated by the symbol L is referred to as the length. The length L > thickness D. In the present embodiment, as a shape change of the cell 20 (power storage element), a change in the thickness (thickness) D is mainly assumed.

[0037] The inventor has established a hypothesis that there are at least two modes in the shape change (mainly the change in thickness D) of the cell 20, and has found that this hypothesis is correct. This will be specifically described below.

[0038] Figure 3 shows the relationship between the change in the thickness of the cell 20 and the change in the element structure. Figure 3A is a chart representing the change in thickness in the storage test. The state of charge (SOC) of the cell 20 was set to 100%, and it was left in an environment at a temperature of 55°C, and the change in thickness D was actually measured. The horizontal axis indicates time (days), and the vertical axis indicates the increase rate (%) of the thickness of the cell 20. The time t0 is the start time of the storage test. As shown in Figure 3A, near the time t1, the increase rate of the thickness of the cell 20 changes. Specifically, the change rate of the thickness from time t0 to time t1 is smaller than the change rate of the thickness after time t1 (from time t1 to time t2). That is, the shape change of the cell 20 progresses in two stages.

[0039] Figure 3B is a chart showing the transition of the element structure of the cell 20 (in this embodiment, two longitudinally wound electrode bodies housed and arranged closely in the cell case). The three charts schematically show the state inside the cell case at the times t0, t1, and t2 in Figure 3A. The line indicated by the symbol W shows the slit existing at the innermost winding start portion of the electrode body 25. The slit W appears as a thin line in a cross-sectional view as shown in Figure 3B. The slit W extends in the winding axis direction (a direction perpendicular to the paper surface of Figure 3B). At time t0, the slit W is linear. From time t0 to time t1, the thickness of the cell 20 increases, and at time t1, wrinkles occur inside the element structure, and the slit W is bent. Also, the outermost circumference of the electrode body 25 bulges. Further, after time t1, the change rate of the thickness increases, the wrinkles inside the element structure become larger, and the deformation of the slit W also becomes larger. The outermost circumference of the electrode body 25 bulges further.

[0040] The results of CAE (Computer Aided Engineering) simulation for confirming the reason why the shape change of the cell 20 progresses in two stages are shown in Figure 4.

[0041] Figure 4 is a diagram simulating a 1 / 4 cross-section of one of the wound electrode bodies housed in the cell case 21. In Figure 4, reference numeral 201 is a separator, reference numeral 202 is a positive electrode, and reference numeral 203 is a negative electrode. The element structure within the cell case 21 has the positive electrode 202, separator 201, and negative electrode 203 stacked and wound. Such a 2DCAE model (two-dimensional CAE model) was created based on the physical property values (such as thickness, Young's modulus, Poisson's ratio, coefficient of linear expansion, yield strength, etc.) and design values of the materials (separator, positive and negative electrode composite materials, foils, etc.) that make up the cell case 21 and the element structure. The expansion of the element structure was reproduced by increasing the thickness of the positive and negative electrode composite materials (for example, using the measured thickness increase trend). Figures 4A, B, and C show cross-sections of the element structure at times (elapsed time) t = 0, t = tb, and t = tc, respectively. As shown in Figure 4, wrinkles occur in the element structure near time t = tb. And after time t = tb, over time t = tc, the deformation gradually becomes larger.

[0042] Figure 5 is a diagram showing the simulation results and measured values of the change in the thickness of the cell 20. In the simulation results shown in Figure 5A, the horizontal axis represents the positive and negative electrode composite material expansion (%), and the vertical axis represents the thickness of the cell. In Figure 5A, the points indicated by reference numerals A, B, and C correspond to the states of the element structures in Figures 4A, 4B, and 4C, respectively. In the measured values shown in Figure 5B (open circuit voltage 100%, standing test at 45°C), the horizontal axis represents time (days), and the vertical axis represents the thickness of the cell. In Figure 5B, the dots indicate the measured values.

[0043] The simulation results show that, similar to the measured values, the swelling mode (shape change mode) changes at the inflection point of the cell swelling. That is, the shape change speed after the inflection point is greater than the shape change speed in the shape change mode (also referred to as the "first mode") from the initial stage to the inflection point. It is suggested that the change in the increase rate (shape change speed) of the cell thickness depends on the expansion of the element structure. It is suggested that there are at least two modes in the shape change of a part (mainly the positive and negative electrode composite materials) of the element structure of the energy storage element (such as the positive and negative electrode composite materials, positive and negative electrode current collectors, separator, etc.).

[0044] Next, the relationship between the occurrence of wrinkles and the change in the shape change mode will be considered.

[0045] FIG. 6 is a diagram showing the relationship between the occurrence of wrinkles in the element structure and the transition of the shape change mode. FIG. 6A shows the element structure from the initial stage to near the change point of the swelling of the cell (when the shape change mode is the first mode), and FIG. 6B shows the element structure after the change point of the swelling of the cell (when the shape change mode is the second mode). As described above, the electrode body 25 is formed by winding a positive electrode, a negative electrode, and a separator on a flat plate called a winding core, and the winding core is removed after the winding is completed. For this reason, a straight slit is formed in the center portion.

[0046] As shown in FIG. 6A, when the cell 20 is left unattended or energized (charged and / or discharged) and time elapses, the positive electrode and the negative electrode gradually swell. Along with this, the electrode body 25 tries to expand outward. On the other hand, the outer perimeter of the electrode body 25 does not change. When the positive electrode and the negative electrode expand, a reaction occurs at the arc portion (rounded portion; R portion), and the positive electrode plate and / or the negative electrode plate (also referred to as the "electrode plate") are pushed inward. For this reason, the flat portion of the electrode body 25 is pushed outward (first mode).

[0047] As shown in FIG. 6B, as time further elapses, due to the reaction at the R portion, the electrode plate continues to be pushed inward, and there is no other way for the escape space due to the expansion of the electrode plate to go toward the flat portion. The electrode plate begins to bend, and wrinkles occur. Due to the occurrence of wrinkles, the electrode plate becomes more prone to bending, so the speed of shape change (thickness change) increases (second mode).

[0048] FIG. 7 is a diagram showing the simulation results of the transition of the long-side surface load. In FIG. 7, the horizontal axis represents the expansion (%) of the positive and negative electrode composite material, and the vertical axis represents the thickness of the cell and the long-side surface load. The long-side surface load is the load when the flat portion of the electrode body 25 is pushed outward in FIG. 6. As shown in FIG. 7, the change mode of the load applied by the electrode body 25 to the long side surface of the cell case 21 also changes before and after the change point of the swelling of the cell.

[0049] Here, taking the swelling of a cell having a wound-type electrode body as an example, the prediction of the shape change of the power storage element was described in consideration of the change in the swelling mode from the first mode to the second mode depending on the degree of formation of wrinkles in the electrode body. Alternatively, for example, in a cell having a laminated electrode body, when the swelling mode (shape change mode) of the electrode changes (for example, when the active material is gradually pulverized with charge and discharge and the specific surface area increases, and the mode of the amount of deposits deposited on the electrode and the amount of gas generated inside the battery changes), the present invention can also be applied.

[0050] Next, the configuration of the estimation device will be described.

[0051] FIG. 8 is a diagram showing the configuration of the estimation device 50. The estimation device 50 includes a control unit 51 that controls the entire device, an input unit 52, a storage unit 53, a timing unit 54, an output unit 55, a determination unit 56, an estimation unit 57, and a communication unit 58. The control unit 51 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The storage unit 53 is composed of a hard disk, a semiconductor memory, or the like, and stores required data.

[0052] The input unit 52 acquires time-series data of a power storage element (for example, cell 20) whose shape change is to be estimated. There may be a plurality of target power storage elements. The time-series data includes, for example, time-series data of the voltage, current, and temperature of the power storage element. In addition to the time-series data, the input unit 52 acquires time data. The time data may be data indicating the start point and the end point of the estimation period for estimating the shape change. When the power storage element is in a standby state, the input unit 52 only needs to acquire the time data. When the power storage element is in an energized state, the input unit 52 acquires the time-series data within the estimation period together with the time data. The time-series data may be measured values or calculated values. The data acquired by the input unit 52 may be stored in the storage unit 53.

[0053] Based on the time-series data acquired by the input unit 52, the control unit 51 identifies the ΔSOC (State Of Charge) and the central SOC of the energy storage element. ΔSOC is the difference between the maximum value and the minimum value of the SOC that changes based on charging or discharging of the energy storage element. The central SOC is the average of the changing SOC.

[0054] The timing unit 54 counts the elapsed time when estimating the shape change of the energy storage element.

[0055] The determination unit 56 determines whether the shape change mode of the energy storage element is the first mode or the second mode. Specifically, the determination unit 56 determines whether the shape change mode of the energy storage element is either the first mode or the second mode based on a predetermined condition.

[0056] The estimation unit 57 estimates the shape change of the energy storage element according to the shape change mode determined by the determination unit 56. By preparing in advance the methods for estimating the shape change of the energy storage element in each shape change mode, an optimal method can be adopted according to the shape change mode, and the shape change of the energy storage element can be accurately estimated.

[0057] The output unit 55 outputs the estimation result by the estimation unit 57 to an external device (for example, a display device, a printing device, etc.).

[0058] The communication unit 58 is equipped with the required communication module and performs transmission and reception of data and information with an external device. For example, it receives and updates an application (program) that identifies the processing of the estimation device 50, and receives and updates each expansion coefficient described later.

[0059] Hereinafter, the estimation of the shape change of the energy storage element will be described in detail.

[0060] The inventor of the present invention has found that a power storage element having a wound electrode body exhibits a specific shape change mode. By grasping the shape change mode of a power storage element having a wound electrode body, the shape change can be accurately estimated. From the initial stage to the mode transition point (the change point of the swelling of the cell), the shape of the power storage element changes according to the first mode, and thereafter, the shape of the power storage element changes according to the second mode. The shape change of the power storage element is appropriately estimated according to whether the estimation time is before or after the mode transition point.

[0061] It may be estimated that the shape change rate in the second mode shifted from the first mode is larger than the shape change rate in the first mode. The shape change rate can be expressed, for example, as (amount of shape change / time) or (amount of shape change / total SOC fluctuation amount). With this configuration, the shape change of the power storage element can be accurately estimated before and after the mode transition.

[0062] FIG. 9 is a diagram showing a method for estimating the shape change of a power storage element during storage. In FIG. 9, the horizontal axis represents time (elapsed time) (days), and the vertical axis represents the thickness D of the cell. The thickness D of the cell is the thickness of the cell case (see FIG. 2). Alternatively, the vertical axis may be the amount of change in the thickness of the cell or the rate of change in the thickness of the cell. The coefficient of expansion with time K1 in the first mode represents the slope of the straight line indicated by the solid line, and the coefficient of expansion with time K2 in the second mode represents the slope of the straight line indicated by the broken line. The thickness D of the cell in the first mode can be obtained by a function F1 such as D = F1(K1, t). Here, K1 is the coefficient of expansion with time in the first mode, and t represents time. Also, the thickness D of the cell in the second mode can be obtained by a function F2 such as D = F2(K2, t). Here, K2 is the coefficient of expansion with time in the second mode, and t represents time. The function F1 (or the coefficient of expansion with time K1 in the first mode) and the function F2 (or the coefficient of expansion with time K2 in the second mode) may be stored in the storage unit 53. Alternatively, the functions F1 and F2 may be configured by an arithmetic circuit.

[0063] In the initial stage of estimating the shape change, the estimation unit 57 calculates the thickness D of the cell using the function F1. Here, the variable t of the function F1 and the value D obtained by the function F1 are referred to as elapsed parameters. That is, the estimation unit 57 estimates the shape change of the power storage element over time and simultaneously calculates the elapsed parameters.

[0064] The determination unit 56 determines the shape change mode based on the elapsed parameters calculated by the estimation unit 57 and a predetermined threshold value. The elapsed parameter may be any parameter for determining whether the shape change mode of the power storage element is the first mode or the second mode. In the example of FIG. 9, the elapsed time t may be used, or the thickness D of the cell may be used. The thickness D of the cell may be the thickness itself (absolute value) or the amount of change from the initial value of the thickness. With this configuration, for example, the shape change of the power storage element in a stationary state (when not energized) can be accurately estimated.

[0065] As shown in FIG. 9, when the elapsed time becomes equal to or greater than the threshold value, or when the thickness of the cell becomes equal to or greater than the threshold value, the estimation unit 57 calculates the thickness D of the cell using the function F2. With this configuration, for example, the shape change of the power storage element in a stationary state (when not energized) can be accurately estimated.

[0066] FIG. 10 is a diagram showing a method for estimating the shape change of a power storage element during energization. In FIG. 10, the horizontal axis represents time (elapsed time) (days), and the vertical axis represents the thickness D of the cell. Alternatively, the horizontal axis may be the total SOC variation (%)

[0067] During the initial stage of estimating the shape change, the estimation unit 57 calculates the thickness D of the cell using the function G1. Here, the variable t of the function G1 and the value D obtained by the function G1 are referred to as elapsed parameters. That is, the estimation unit 57 estimates the shape change of the power storage element as time elapses and simultaneously calculates the elapsed parameters.

[0068] The determination unit 56 determines the shape change mode based on the elapsed parameters calculated by the estimation unit 57 and a predetermined threshold value. The elapsed parameter may be any parameter for determining whether the shape change mode of the power storage element is the first mode or the second mode. In the example of FIG. 10, the elapsed time t may be used, or the thickness D of the cell may be used. The thickness D of the cell may be the thickness itself (absolute value) or the amount of change from the initial value of the thickness. With this configuration, for example, the shape change of the power storage element during energization can be accurately estimated.

[0069] As shown in FIG. 10, when the elapsed time becomes equal to or greater than the threshold value, or when the thickness of the cell becomes equal to or greater than the threshold value, the estimation unit 57 calculates the thickness D of the cell using the function G2. With this configuration, for example, the shape change of the power storage element during energization can be accurately estimated.

[0070] FIG. 11 is a diagram showing the relationship between the first-mode time-dependent expansion coefficient K1, the second-mode time-dependent expansion coefficient K2, and temperature. In FIG. 11, the horizontal axis represents time (days), and the vertical axis represents the change amount (%) of the cell thickness. FIG. 11 shows a solid-line straight line with the first-mode time-dependent expansion coefficient K1 at temperatures T1 and T2 (>T1) as the slope, and a dashed-line straight line with the second-mode time-dependent expansion coefficient K2 at temperatures T1 and T2 as the slope. As shown in FIG. 11, as the temperature T increases, the values of the first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 increase. In FIG. 11, for the sake of convenience, only temperatures T1 and T2 are shown, but by storing the first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 associated with each required temperature in the storage unit 53, the optimal first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 can be used according to the temperature around the power storage element. Although not shown, the first-mode energization expansion coefficient M1 and the second-mode energization expansion coefficient M2 during energization are also stored in the storage unit 53 in the same manner. Alternatively, the first-mode time-dependent expansion coefficient and the second-mode time-dependent expansion coefficient may be formulated as functions of temperature, and an arithmetic circuit that performs the formulated calculation may be used.

[0071] FIG. 12 is a diagram showing the relationship between the first-mode aging expansion coefficient K1, the second-mode aging expansion coefficient K2, and ΔSOC. In FIG. 12, the horizontal axis represents time (days), and the vertical axis represents the change amount (%) of the cell thickness. FIG. 12 shows a solid-line straight line with the first-mode aging expansion coefficient K1 at ΔSOC1 and ΔSOC2 (>ΔSOC1) as the slope, and a dashed-line straight line with the second-mode aging expansion coefficient K2 at ΔSOC1 and ΔSOC2 as the slope. As shown in FIG. 12, as ΔSOC increases, the values of the first-mode aging expansion coefficient K1 and the second-mode aging expansion coefficient K2 increase. In FIG. 12, for the sake of convenience, only ΔSOC1 and ΔSOC2 are illustrated, but by storing the first-mode aging expansion coefficient K1 and the second-mode aging expansion coefficient K2 associated with each required ΔSOC in the storage unit 53, the optimal first-mode aging expansion coefficient K1 and the second-mode aging expansion coefficient K2 can be used according to the ΔSOC of the energy storage element. Although not illustrated, the first-mode energization expansion coefficient M1 and the second-mode energization expansion coefficient M2 during energization are also stored in the storage unit 53 in the same manner. Alternatively, the first-mode aging expansion coefficient and the second-mode aging expansion coefficient may be formulated as functions of ΔSOC, and an arithmetic circuit that performs the formulated calculation may be used.

[0072] FIG. 13 is a diagram showing the relationship between the first-mode time-dependent expansion coefficient K1, the second-mode time-dependent expansion coefficient K2, and the central SOC. In FIG. 13, the horizontal axis represents time (days), and the vertical axis represents the change amount (%) of the cell thickness. FIG. 13 shows a solid-line straight line with the first-mode time-dependent expansion coefficient K1 at the central SOC1 and the central SOC2 (> central SOC1) as the slope, and a dashed-line straight line with the second-mode time-dependent expansion coefficient K2 at the central SOC1 and the central SOC2 as the slope. As shown in FIG. 13, the values of the first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 change depending on the central SOC. In FIG. 13, for convenience, only the central SOC1 and the central SOC2 are shown, but by storing the first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 associated with each required central SOC in the storage unit 53, the optimal first-mode time-dependent expansion coefficient K1 and the second-mode time-dependent expansion coefficient K2 can be used according to the central SOC of the energy storage element. Although not shown, the first-mode energization expansion coefficient M1 and the second-mode energization expansion coefficient M2 during energization are also stored in the storage unit 53 in the same manner. Alternatively, the first-mode time-dependent expansion coefficient and the second-mode time-dependent expansion coefficient may be formulated as functions of the central SOC, and an arithmetic circuit that performs the formulated arithmetic may be used.

[0073] The determination unit 56 may determine the transition from the first mode to the second mode according to at least one of the types of the positive electrode active material and the negative electrode active material of the energy storage element. It is considered that energy storage elements with different active materials may have different transition times from the first mode to the second mode even if the usage environment, dimensions, and element structures are the same. In the case of a lithium-ion battery, lithium ions are inserted into or desorbed from the active material during charge and discharge. Since the shape change rate is different according to whether at least one of the positive electrode active material and the negative electrode active material is an active material with a large volume change or a small volume change during insertion and desorption, it is possible to determine the transition time from the first mode to the second mode. For example, when the positive electrode active material is a lithium nickel oxide-based material, since the volume change during insertion and desorption is relatively large, it can be determined that the transition from the first mode to the second mode is relatively fast.

[0074] Figure 14 is a flowchart showing the processing procedure of shape estimation by the estimation device 50. Hereinafter, for convenience, the main body of the processing will be described as the control unit 51. The control unit 51 acquires time-series data of the current, voltage, and temperature of the energy storage element together with time data (S11), and specifies ΔSOC, central SOC, and average temperature (S12). When the energy storage element is in a standby state, ΔSOC, central SOC, and average temperature of the energy storage element are acquired. When the energy storage element is in a non-energized state (standby state) after being energized, ΔSOC, central SOC, and average temperature immediately before entering the non-energized state may be specified.

[0075] The control unit 51 calculates an elapsed parameter (S13), and determines whether the calculated elapsed parameter is equal to or greater than a threshold value (S14). When the elapsed parameter is less than the threshold value (NO in S14), the first-mode aging expansion coefficient K1 and the first-mode energization expansion coefficient M1 are selected (S15), and the shape change is estimated (S17).

[0076] When the elapsed parameter is equal to or greater than the threshold value (YES in S14), the control unit 51 selects the second-mode aging expansion coefficient K2 and the second-mode energization expansion coefficient M2 (S16), and performs the process of step S17.

[0077] The control unit 51 determines whether to end the process (S18). When the process is not ended (NO in S18), the processes after step S13 are continued. When the process is ended (YES in S18), the process is ended.

[0078] When the states of the energy storage element are a mixture of both the energized state and the standby state, the shape estimation can be obtained as the sum of the aging expansion amount (shape change during standby) and the energization expansion amount (shape change during energization) calculated using the aging expansion coefficients (K1, K2) and the energization expansion coefficients (M1, M2).

[0079] The estimation device 50 can also be realized by using a general-purpose computer equipped with a CPU (processor), a RAM (memory), etc. That is, as shown in FIG. 14, a computer program defining the procedures of each process is loaded into the RAM (memory) provided in the computer, and by executing the computer program with the CPU (processor), the estimation device 50 can be realized on the computer. The computer program may be recorded and distributed on a recording medium.

[0080] As described above, according to the present embodiment, in the development stage and design stage of the energy storage element, the shape change (thickness change) at the end of the life of the energy storage element can be estimated, and an optimal design of the battery module considering the shape (thickness) of the energy storage element at the end of the life becomes possible. Thereby, excessive enlargement of the battery module can be avoided, cost reduction can be achieved, and maximum battery performance can be achieved.

[0081] In the present embodiment, mainly the swelling of the element structure has been described. The present embodiment can be similarly applied not only to the swelling of the element structure but also to the shape change of the energy storage element due to gas generated from the electrolytic solution in the case of overcharging or the like. In the present embodiment, the case where the energy storage element has a prismatic cell case (for example, made of metal) has been described. Alternatively, the energy storage element may be a so-called pouch cell using a laminated film for the case.

[0082] The embodiments are illustrative in all respects and not restrictive. The scope of the present invention is shown by the scope of the claims, and includes all modifications within the meaning and scope equivalent to the scope of the claims.

Explanation of Reference Numerals

[0083] 10 Battery module (energy storage device) 11 Case 12 Bus bar 13, 14 Lead 20 Cell (energy storage element) 21 Cell case 21a and 21b long sides 21c and 21d short sides 22 cover plate 23 and 26 terminals 24 rupture valve 25 electrode body 50 estimation device 51 control unit 52 input unit 53 memory unit 54 timing unit 55 output unit 56 determination unit 57 estimation unit 58 communication unit

Claims

1. A determination unit that determines whether the shape change mode of a power storage element having a wound electrode body over time is a first mode or a second mode with a different shape change rate from the first mode based on a predetermined elapsed parameter and a threshold value; An estimation unit that estimates the shape change of the power storage element depending on the expansion of the element structure of the power storage element and the generation of wrinkles in the element structure according to the shape change mode determined by the determination unit Comprising An estimation device.

2. The shape change rate in the second mode shifted from the first mode is greater than the shape change rate in the first mode. The estimation device according to Claim 1.

3. Comprising a first acquisition unit that acquires or calculates an elapsed parameter related to the elapsed period from the start of leaving the power storage element, The determination unit Determines the shape change mode based on the elapsed parameter acquired or calculated by the first acquisition unit. The estimation device according to Claim 1 or Claim 2.

4. Comprising a second acquisition unit that acquires or calculates an elapsed parameter related to the energization of the power storage element, The determination unit Determines the shape change mode based on the elapsed parameter acquired or calculated by the second acquisition unit. The estimation device according to any one of Claims 1 to 3.

5. The elapsed parameter Includes any one of the number of days elapsed when the power storage element is non-energized or energized, the absolute value of the dimensions of the power storage element, the amount of change in the shape of the power storage element, and the total amount of change in the state of charge (SOC) of the power storage element. The estimation device according to Claim 3 or Claim 4.

6. The determination unit Determines the transition from the first mode to the second mode according to at least one of the types of the positive electrode active material and the negative electrode active material of the power storage element. The estimation device according to any one of Claims 1 to 5.

7. The shape change includes a change in the thickness of the wound electrode body. The estimation device according to Claim 1.

8. A computer program that causes a computer to Determine whether the shape change mode of a power storage element having a wound electrode body over time is a first mode or a second mode with a different shape change rate from the first mode based on a predetermined elapsed parameter and a threshold value, Estimate the shape change of the power storage element depending on the expansion of the element structure of the power storage element and the generation of wrinkles in the element structure according to the determined shape change mode. Execute the process.

9. Determining whether the shape change mode of a power storage element having a wound electrode body over time is the first mode or a second mode with a different shape change rate from the first mode based on a predetermined elapsed parameter and a threshold value, estimating the shape change of the power storage element depending on the expansion of the element structure of the power storage element and the generation of wrinkles in the element structure according to the determined shape change mode, estimation method.

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