Estimation device, estimation method and storage medium

Abstract

The present invention provides an estimation device, an estimation method and a computer program. The estimation device estimates the internal state of a storage element, the storage element having a positive electrode, including a SiO x The negative electrode of the negative electrode active material and the non-aqueous electrolyte are changed from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode. The estimation device estimates the internal state of the storage element using the voltage value and the amount of current flow within a given voltage range or a given measured voltage value of the storage element, or based on information related to the shape of the discharge curve of the storage element.

Description

Technical Field

[0001] One aspect of the present invention relates to an estimation device, an estimation method, and a computer program for estimating an internal state of a power storage element. Background Art

[0002] Storage elements such as lithium-ion secondary batteries are used as power sources for portable devices such as laptop computers and mobile phones. In recent years, they have been used in a wide range of fields such as power sources for EV (electric vehicles), HEV (hybrid electric vehicles), and PHEV (plug-in hybrid electric vehicles), and the realization of high-capacity secondary batteries is expected to be achieved according to the application.

[0003] As such a next-generation high-capacity battery, SiO, which is silicon oxide, is used as the active material of the negative electrode. x Batteries with (0.5≤x≤1.5) have attracted much attention in recent years.

[0004] In order to install a secondary battery in an EV or the like, it is important to estimate the degradation state of the storage element such as the amount of capacity reduction, and various techniques have been proposed (for example, refer to Patent Document 1).

[0005] Unlike the conventional carbon-based negative electrode that has been studied extensively in the past, SiO x In lithium-ion secondary batteries, the conventional degradation state estimation method cannot be applied due to the difference in characteristics. x There is a correlation between the change in the amount of current flow in the storage element relative to the change in the voltage value at the end of discharge, that is, dQ / dV, and the capacity retention rate, making it possible to estimate the degradation state (see Patent Document 2).

[0006] Prior Art Literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-68458

[0009] Patent Document 2: Japanese Patent Application Publication No. 2017-20916 Summary of the invention

[0010] Problems to be solved by the invention

[0011] When using SiO xIn the case of a negative electrode restricted type storage element, due to repeated charge and discharge, the amount of SEI (Solid Electrolyte Interface) film formed at the interface between the active material and the electrolyte of the negative electrode increases, and the amount of Li captured by the SEI film increases (the so-called restricted electrode refers to the electrode with a smaller discharge capacity in the battery design. Storage elements with a smaller discharge capacity of the negative electrode than the positive electrode are called negative electrode restricted type because the discharge capacity of the storage element is limited by the discharge capacity of the negative electrode). As a result, the deviation of the capacity balance between the positive and negative electrodes increases.

[0012] The present invention studies a method of pre-doping the negative electrode with Li to make it contain more Li ions than the positive electrode in terms of stoichiometry before starting the battery reaction, thereby forming a positive electrode-restricted storage element in which the discharge capacity is limited by the discharge capacity of the positive electrode. Since the discharge capacity ratio of the negative electrode to the positive electrode becomes larger, the utilization rate of the negative electrode decreases, and the increase in the deviation of the capacity balance between the positive and negative electrodes accompanying the repetition of charge and discharge can be suppressed. As a result, capacity degradation can be suppressed and cycle characteristics are improved.

[0013] In such a power storage element, it is required to estimate the internal state.

[0014] One aspect of the present invention aims to provide an estimation device, an estimation method, and a computer program capable of estimating the internal state of an electric storage element that has changed from a positive electrode limiting type to a negative electrode limiting type.

[0015] Means for solving problems

[0016] An estimation device according to one aspect of the present invention estimates the internal state of an electric storage element, wherein the electric storage element has a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changes from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode, the estimation device comprising: an acquisition unit, which acquires a voltage value and a current flow of the electric storage element within a given voltage range or a given measured voltage value; and an estimation unit, which uses the voltage value and the current flow to estimate the internal state of the electric storage element.

[0017] Another aspect of the present invention relates to an estimation device that estimates the internal state of an electric storage element, wherein the electric storage element has a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changes from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode, the estimation device comprising: an estimation unit that estimates the internal state of the electric storage element based on information related to the shape of a discharge curve of the electric storage element in a voltage range in which the potential of the negative electrode is greater than or equal to a first preset value, or information related to the shape of a discharge curve of the electric storage element in a voltage range below a second preset value.

[0018] Effects of the Invention

[0019] In an energy storage element that changes from a positive electrode-limited type to a negative electrode-limited type with use (cycling), the degradation state of the energy storage element can be estimated using a voltage value and a current flow rate within a given voltage range or a given measured voltage value of the energy storage element, or based on information related to the shape of a discharge curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a graph showing a charge and discharge curve when the amount of pre-doping (PD) of Li to the negative electrode is 0%.

[0021] Figure 2 This is a graph showing a charge and discharge curve when the pre-doping amount is 40%.

[0022] Figure 3 It is a graph showing the relationship between DOD and the cell voltage value when charge and discharge are repeated.

[0023] Figure 4 This is an external view of a power storage device including the estimation device according to the first embodiment.

[0024] Figure 5 This is a block diagram showing the functional structure of the estimation device according to the first embodiment.

[0025] Figure 6 1 is a flowchart showing the procedure of the internal state estimation process of the power storage element by the estimation device.

[0026] Figure 7 It is a graph showing the relationship between the number of cycles and the capacity retention rate when the pre-doping amount is changed.

[0027] Figure 8 This is a graph showing the relationship between the capacity retention rate and dQ / dV when the energy storage element is discharged and dQ / dV at a voltage value of 2.75V is obtained.

[0028] Fig. 9 This is a graph showing the relationship between dQ / dV at a voltage value of 2.75 V and the number of cycles when a storage element having a pre-doping amount of 40% is used and discharged.

[0029] Fig.10 This is a block diagram showing a vehicle according to the second embodiment.

[0030] Fig.11 This is a block diagram showing an internal state estimation server and a power storage element according to the third embodiment. DETAILED DESCRIPTION

[0031] Hereinafter, the present invention will be described in detail based on the drawings showing the present embodiments.

[0032] (Overview of Embodiments)

[0033] The negative electrode of the electric storage element (non-aqueous electrolyte secondary battery) according to the embodiment contains SiO x The active material of the storage element is a positive electrode-restricted type after manufacturing.

[0034] Figure 1 The charge and discharge curves are shown when the pre-doping amount (PD amount) of Li is 0% relative to the charge capacity of the negative electrode. Figure 2 The figure shows the charge and discharge curve when the pre-doping amount is 40%. The horizontal axis is SOC (State of Charge) and the vertical axis is the voltage value of the storage element cell. Figure 1 as well as Figure 2 In the figure, curve a is the charging curve of the negative electrode, curve b is the discharging curve of the negative electrode, curve c is the charging curve of the positive electrode, curve d is the discharging curve of the positive electrode, curve e is the charging curve of the single battery, and curve f is the discharging curve of the single battery.

[0035] like Figure 1 As shown, when the pre-doping amount is 0%, the discharge capacity of the negative electrode is smaller than that of the positive electrode, so the discharge capacity of the single cell is determined by the negative electrode. That is, the storage element is a negative electrode-limited type.

[0036] exist Figure 2 When the pre-doping amount is 40%, the discharge capacity of the positive electrode is smaller than that of the negative electrode, so the discharge capacity of the single cell is determined by the positive electrode. That is, the storage element is a positive electrode-restricted type. As described above, the cycle characteristics of the positive electrode-restricted type storage element are improved.

[0037] Figure 3This is a graph showing the relationship between DOD (Depth of Discharge) and cell voltage when charging and discharging are repeated in a storage element that changes from a positive electrode restricted type to a negative electrode restricted type. The horizontal axis is DOD (%) and the vertical axis is cell voltage (V). In the figure, curve g is a graph showing the curve before the start of the cycle, curve h is a graph showing the curve after 300 cycles, curve i is a graph showing the curve after 600 cycles, and curve j is a graph showing the curve after 900 cycles.

[0038] like Figure 3 As shown in the figure, as the number of charge and discharge repetitions increases, the degradation progresses. In a given voltage range, the shape of the discharge curve changes in the order of a first state (curve g), a second state (curve h, curve i) with a gentler slope than the first state, and a third state (curve j) with a steeper slope than the second state. It is believed that the main reason for the change from the second state to the third state is that the rise of the negative electrode potential at the end of the discharge becomes rapid due to the structural change or increased resistance of the silicon oxide of the negative electrode.

[0039] As the number of charge and discharge repetitions increases, the amount of SEI film formed on the negative electrode increases, and the film captures Li ions, thereby increasing the deviation in capacity balance, and it is believed that the storage element has reached the end of its life. By setting the storage element to a positive electrode-restricted type, the cycle characteristics are improved compared to a negative electrode-restricted type storage element, but when the number of cycles increases further, the storage element becomes a negative electrode-restricted type, and the capacity gradually decreases.

[0040] In one embodiment, a voltage value and a current flow rate within a given voltage range or a given measured voltage value are obtained when the storage element is discharged or charged. dQ / dV can also be calculated based on the voltage value and the current flow rate. When charging and discharging are performed, dQ / dV is calculated during charging or discharging.

[0041] For the negative electrode, SiO x In a storage element, the degree of change in voltage value changes as the number of charge and discharge repetitions increases within a given voltage range in a curve showing the relationship between voltage value and capacity during discharge or charge. dQ / dV in this voltage range changes uniquely as the number of charge and discharge repetitions increases.

[0042] The given voltage range is preferably a voltage range in which the potential of the negative electrode is greater than the first preset value, or a voltage range at the end of the discharge of the storage element. In this voltage range, the voltage of the storage element drops sharply due to the increase in the number of repetitions of charge and discharge. The absolute value of dQ / dV at a given measured voltage value within the voltage range increases with the increase in the number of repetitions of charge and discharge. When the number of repetitions of charge and discharge increases further after the inflection point, the absolute value of dQ / dV decreases.

[0043] The negative electrode potential of the battery cell is preferably greater than a first preset value. The first preset value may be, for example, 0.6 V (vs. Li / Li + ).

[0044] When the negative electrode potential cannot be obtained, the range is preferably a single cell voltage range below a second preset value. The second preset value may be, for example, 3.4 V. The single cell voltage range is preferably 2.5 V to 3.25 V, and more preferably 2.75 V to 3.2 V.

[0045] When the absolute value of dQ / dV is equal to or greater than a first determination value, it may be determined that the limiting electrode of the power storage element has been switched from the positive electrode to the negative electrode.

[0046] Then, when the absolute value of dQ / dV is equal to or smaller than the second determination value, it may be determined that the power storage element has reached the end of its life.

[0047] In other embodiments, the internal state of the storage element is estimated based on information about the shape of a discharge curve of the storage element in a voltage range where the potential of the negative electrode is greater than or equal to a first preset value, or information about the shape of a discharge curve of the storage element in a voltage range less than or equal to a second preset value.

[0048] Here, “information on the shape of the discharge curve” includes: (1) the shape of the discharge curve drawn based on the charge change and voltage change, (2) the slope of the straight line between two given points on the curve, and (3) the intersection angle of the tangent lines on the curve.

[0049] (Implementation Method 1)

[0050] Hereinafter, as Embodiment 1, a power storage device mounted on a vehicle will be described as an example.

[0051] Figure 4 1 is an external view of a power storage device 10 including an estimation device 100 according to the first embodiment.

[0052] The power storage device 10 includes an estimation device 100 , a plurality of power storage elements 200 , and a housing case 300 that houses the estimation device 100 and the power storage elements 200 .

[0053] The estimation device 100 may also include a circuit board on which a circuit for estimating the internal state of the storage element 200 is mounted, and is arranged above the plurality of storage elements 200. The estimation device 100 is connected to the plurality of storage elements 200, obtains information from the plurality of storage elements 200, and estimates the internal state of the storage element 200. The estimation device 100 may also be implemented by a CMU (Cell Monitoring Unit) or a BMU (Battery Management Unit).

[0054] Alternatively, estimation device 100 may be disposed outside housing case 300 or may be disposed at a location remote from power storage device 10 and connected to power storage device 10 via a network. The detailed functional configuration of estimation device 100 will be described later.

[0055] The storage element 200 is a secondary battery capable of charging and discharging electric power. In the present embodiment, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery is used. A plurality of rectangular storage elements 200 are connected / arranged in series to form a battery pack. The shape of the storage element 200 is not limited to a prismatic shape, and may also be a cylindrical shape, an oblong cylindrical shape, or a bag shape.

[0056] The storage element 200 includes a container 201 and an electrode terminal 202 (a positive terminal and a negative terminal) protruding from the container 201. An electrode body and a collector (a positive electrode collector and a negative electrode collector) connecting the electrode body and the electrode terminal 202 are arranged inside the container 201, and an electrolyte (a non-aqueous electrolyte) is sealed. The electrode body is formed by winding a positive electrode, a negative electrode, and a separator. The electrode body is not limited to a wound electrode body, and may also be a stacked electrode body in which flat plate-shaped plates are stacked.

[0057] The positive electrode is, for example, an electrode plate having a positive electrode active material layer formed on a positive electrode substrate of a long strip of metal foil composed of aluminum, aluminum alloy, etc. As the positive electrode active material used for the positive electrode active material layer, as long as it is a positive electrode active material that can absorb and release lithium ions, known materials can be used appropriately. For example, as the positive electrode active material, transition metal oxides, transition metal sulfides, lithium transition metal composite oxides, lithium-containing polyanionic metal composite compounds, etc. can be listed. As transition metal oxides, manganese oxides, iron oxides, copper oxides, nickel oxides, vanadium oxides, etc. can be listed. As transition metal sulfides, molybdenum sulfide, titanium sulfide, etc. can be listed. As lithium transition metal composite oxides, lithium manganese composite oxides, lithium nickel composite oxides, lithium cobalt composite oxides, lithium nickel cobalt composite oxides, lithium nickel manganese composite oxides, lithium nickel cobalt manganese composite oxides, etc. can be listed. As lithium-containing polyanionic metal composite compounds, lithium phosphate, lithium cobalt phosphate, etc. can be listed. Furthermore, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyphenylene glycol, polyacetylene, and polypropylene-based materials, and carbonaceous materials having a pseudo-graphite structure, etc. can be cited.

[0058] The lithium transition metal composite oxide type active material may be a Li-excess type active material in which the molar ratio of Mn in Me (transition metal) Mn / Me exceeds 0.5 and the composition ratio of Li to Me Li / Me exceeds 1.

[0059] The positive electrode active material can also be Figure 3 However, in this embodiment, since the change in the potential behavior of the negative electrode after cycling is used, it is preferred to select a positive electrode active material whose potential of the positive electrode hardly changes in a complex manner.

[0060] From this point of view, it is preferred that the discharge curve changes continuously or a flat portion is observed in a wide range of positive electrode active materials. Examples of such positive electrode active materials include lithium transition metal composite oxides having a layered structure and lithium iron phosphate having an olivine-type crystal structure.

[0061] Alternatively, even when a positive electrode with reduced capacity or a changed discharge curve shape is used, it is possible to estimate the deterioration state of the positive electrode and the change in curve shape due to imbalance, thereby accurately estimating the internal state of the storage element.

[0062] The negative electrode is, for example, an electrode plate having a negative electrode active material layer formed on a negative electrode substrate which is a long strip of metal foil made of copper, copper alloy, etc. As the negative electrode active material used for the negative electrode active material layer, only SiO x , SiO xand other negative electrode active materials that can absorb and release lithium ions. x Other negative electrode active materials used in combination include graphite, hard carbon, soft carbon, etc. Among these other active materials, graphite has a relatively low charge and discharge potential, so it can provide a high energy density storage element, so it is preferred. x The graphite used in the mixture includes flake graphite, spherical graphite, artificial graphite, natural graphite, etc. Among them, flake graphite is used because it is easy to maintain the bond with SiO even if the charge and discharge are repeated. x The contact of the particle surface is preferred because it can easily provide a storage element with excellent charge and discharge cycle performance. x The mixing ratio with other negative electrode active materials is not limited. For example, as the negative electrode active material, SiO x A negative electrode active material containing flaky graphite in a ratio of 8:2 or 2:8. Furthermore, a conductive additive such as acetylene black or Ketjen black may be contained. SiO in the negative electrode active material x The content of SiO is not particularly limited, but in order to exhibit the characteristics during discharge described below, it is preferably 5 wt % or more, and more preferably 10 wt % or more. x As particles, particles whose surfaces are preliminarily coated with carbon material can be used.

[0063] SiO x is doped with Li. x The period of Li doping can be any stage as long as it is before the initial charging between the positive and negative electrodes. x The particles are mixed with other negative electrode active materials, binders, etc. to form a negative electrode mixture.

[0064] In the positive electrode limited type storage element 200, the greater the pre-doping amount of Li, the lower the utilization rate of the negative electrode, so the cycle characteristics are improved, but the discharge capacity of the storage element is reduced. Therefore, the pre-doping amount is based on the coulomb efficiency of the positive electrode, the SiO in the negative electrode, and the amount of Li in the negative electrode. x The appropriate value is set based on the content of, the coulombic efficiency of the negative electrode, the cycle characteristics required of the storage element, the rated capacity, etc.

[0065] The separator is, for example, a microporous sheet made of a synthetic resin. As long as the separator does not impair the performance of the storage element 200, a known material can be used as appropriate. As long as the electrolyte (non-aqueous electrolyte) sealed in the container 201 does not impair the performance of the storage element 200, there is no particular limitation on its type, and a variety of types can be selected.

[0066] The energy storage element 200 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery.

[0067] Next, the functional structure of the estimation device 100 will be described.

[0068] Figure 5 2 is a block diagram showing the functional structure of the estimation device 100 according to the present embodiment.

[0069] The estimation device 100 estimates the internal state of the storage element 200. The estimation device 100 includes an information processing unit 110, an estimation unit 120, a storage unit 130, a timing unit 140, and an interface (I / F) 150. The storage unit 130 stores an estimation program 131 for estimating the internal state of the storage element 200, charge and discharge history data 132, and estimation data 133.

[0070] Sensors 600 such as current sensors, voltage sensors, and temperature sensors that detect physical quantities such as current values, voltage values, and temperatures of the power storage elements 200 are connected to the information processing unit 110 via the I / F 150. Here, a plurality of sensors are represented as one "sensor 600." There are also cases where the temperature is not detected by the sensor.

[0071] The estimation program 131 may also be stored in the storage medium 40 in a computer-readable state. In this case, the storage unit 130 stores the estimation program 131 read from the storage medium 40 by a reading device not shown in the figure. The storage medium 40 may also be a semiconductor memory such as a flash memory. Instead, the storage medium 40 may also be an optical disk such as a CD (Compact Disc)-ROM, a DVD (Digital Versatile Disc)-ROM, or a BD (Blu-ray (registered trademark) Disc). The storage medium 40 may also be a magnetic disk such as a floppy disk or a hard disk, a magneto-optical disk, or the like. The estimation program 131 involved in the present embodiment may also be obtained from an external computer not shown in the figure connected to the communication network and stored in the storage unit 130.

[0072] The information processing unit 110 acquires the detection information of the physical quantity of each storage element 200 from the sensor 600. The timing of acquiring the detection information is not particularly limited. The information processing unit 110 measures the timing with reference to the timing unit 140. The information processing unit 110 writes the acquired detection information into the charge and discharge history data 132 of the storage unit 130. By accumulating the detection information of the physical quantity of the storage element 200, the temporal data of the physical quantity can be obtained, which becomes the charge and discharge history record.

[0073] The charge and discharge history refers to the operation history of the storage element 200, and includes information indicating the period (usage period) during which the storage element 200 was charged or discharged, information related to the charge or discharge performed by the storage element 200 during the use period, etc. The information indicating the use period of the storage element 200 includes information indicating the time point when the storage element 200 was charged or discharged, the cumulative use period during which the storage element 200 was used, etc.

[0074] The information related to the charging or discharging performed by the storage element 200 indicates the voltage, current, and battery state when the storage element 200 is charging or discharging. The battery state indicates the operating state of the storage element 200, such as the charging state, the discharging state, and the rest state. When the battery state is estimated based on the information indicating the voltage or current of the storage element 200, the information indicating the battery state is not necessary.

[0075] The information processing unit 110 reads the voltage, current, energization period, etc. when the storage element 200 is discharged from the charge and discharge history data 132, and calculates the energization amount (Q). The information processing unit 110 calculates the change (dQ / dV) of the energization amount (Q) relative to the voltage (V) at a given measured voltage value in the given voltage range.

[0076] The information processing unit 110 may calculate the capacity maintenance rate of the power storage element 200 based on the calculated capacity.

[0077] The information processing unit 110 writes the acquired dQ / dV, the voltage value corresponding thereto, and the usage period (e.g., date and time) into the estimation data 133 stored in the storage unit 130. The estimation data 133 may be a data table in which "usage period", "voltage value", and "dQ / dV" are associated with each other.

[0078] The estimation unit 120 estimates the internal state of the storage element 200 using dQ / dV acquired by the information processing unit 110. Specifically, the estimation unit 120 determines that the limiting electrode of the storage element has switched from the positive electrode to the negative electrode when the absolute value of dQ / dV is equal to or greater than a first determination value.

[0079] Then, when the absolute value of dQ / dV after passing the local maximum value (inflection point) becomes equal to or smaller than the second determination value, the estimation unit 120 determines that the power storage element has reached the end of its life.

[0080] Figure 6 1 is a flowchart showing the procedure of the internal state estimation process of the power storage element 200 by the information processing unit 110 and the estimation unit 120 of the estimation device 100 .

[0081] When discharging the power storage element 200 at a predetermined time interval, the information processing unit 110 of the estimation device 100 acquires dQ / dV as described above and stores the absolute value of dQ / dV in the charge and discharge history data 132 of the storage unit 130 ( S1 ).

[0082] The estimation unit 120 of the estimation device 100 determines whether the limiting pole of the storage element 200 is the negative pole (S2). When the absolute value of dQ / dV becomes equal to or greater than the first determination value, it is determined that the limiting pole of the storage element has been switched from the positive pole to the negative pole. When the estimation unit 120 determines that the limiting pole is not the negative pole (S2: No), the process returns to S1.

[0083] When the estimation unit 120 determines that the limiting electrode of the storage element 200 is the negative electrode (S2: Yes), it determines whether the absolute value of dQ / dV is less than or equal to a threshold value (second determination value) (S3). When the estimation unit 120 determines that the absolute value of dQ / dV is not less than or equal to the threshold value (S3: No), the process returns to S1.

[0084] When determining that the absolute value of dQ / dV is equal to or smaller than the threshold value ( S3 : Yes), the estimation unit 120 determines that the power storage element has reached the end of its life ( S4 ), and terminates the process by, for example, notifying through a notifying unit.

[0085] The estimation process of the internal state by the estimation unit 120 described above will be described based on an embodiment.

[0086] The positive electrode was prepared by containing an active material represented by the composition formula LiCo1 / 3Ni1 / 3Mn1 / 3O2, acetylene black as a conductive aid, and polyvinylidene fluoride as a binder at a mass ratio of 94:3:3. SiO2 as an active material was contained at a mass ratio of 72:18:10. x The negative electrode was made of graphite and polyimide as a binder. Here, the pre-doping amount was changed to 0%, 20%, 30%, and 40% electrochemically relative to the charge capacity of the negative electrode to make a single cell. The discharge capacity of the single cell is 3 mAh / cm 2 .

[0087] The greater the pre-doping amount, the greater the discharge capacity ratio of the negative electrode to the positive electrode. When the pre-doping amount is 0% and 20%, the single cell is a negative electrode restricted type (comparative example), and when the pre-doping amount is 30% and 40%, the single cell is a positive electrode restricted type (exemplary example).

[0088] For each single cell, the relationship between the number of cycles when charge and discharge were repeated and the capacity retention rate (discharge capacity retention rate) was determined.

[0089] Figure 7It is a graph showing the relationship between the number of cycles of each single cell and the capacity retention rate at a voltage value of 2.75 V. The horizontal axis represents the number of cycles, and the vertical axis represents the capacity retention rate (%).

[0090] according to Figure 7 It is known that as the pre-doping amount increases, the capacity decrease can be suppressed even if the number of cycles increases, and the cycle characteristics are improved. It is believed that this is because the utilization rate of the negative electrode decreases as the discharge capacity ratio becomes larger, which can suppress the expansion of the deviation amount of the capacity balance between the positive and negative electrodes accompanied by repeated charge and discharge.

[0091] For each single cell, dQ / dV at a voltage value of 2.75 V during charge and discharge cycles was plotted against the capacity retention rate.

[0092] Figure 8 2 is a graph showing the relationship between the capacity retention rate and dQ / dV. The horizontal axis represents the capacity retention rate (%) and the vertical axis represents dQ / dV.

[0093] The values ​​in brackets at each point correspond to Figure 7 The number of cycles.

[0094] In the case of negative electrode-restricted storage elements with pre-doping amounts of 0% and 20%, Figure 8 In the region (A), the capacity retention rate and the absolute value of dQ / dV are in a proportional relationship.

[0095] In the case of positive electrode limited type storage elements with pre-doping amounts of 30% and 40%, after passing through region (B) where the absolute value of dQ / dV increases without a decrease in discharge capacity, the absolute value of dQ / dV decreases as the degradation behavior of region (A) occurs.

[0096] As described above, in an electric storage element that is positive electrode-limited when immediately after manufacture and becomes negative electrode-limited as charge and discharge are repeated, the internal state can be estimated regardless of the pre-doping amount, the balance between the positive and negative electrodes, and the history until reaching the region (A).

[0097] As the number of repetitions of charge and discharge increases, the capacity balance deviates. In the case where the capacity of the positive electrode does not decrease and the discharge curve does not change even if the charge and discharge are repeated, even if the capacity balance deviates, the capacity of the single cell will not decrease in appearance. As the deviation of the capacity balance between the positive and negative electrodes increases, the shape of the discharge curve changes. This corresponds to the area (B).

[0098] If the deviation of the capacity balance further increases, the capacity of the single cell starts to decrease. This corresponds to the region (A).

[0099] By monitoring the change in dQ / dV in the region (B), even when the capacity of the positive electrode does not decrease, it is possible to estimate the deviation of the capacity balance between the positive and negative electrodes, that is, the internal state of the energy storage device 200 .

[0100] Fig. 9 The graph shows the relationship between dQ / dV and the number of cycles at a voltage of 2.75 V when the storage element 200 with a pre-doping amount of 40% is used and discharged. The horizontal axis is the number of cycles, the left vertical axis is dQ / dV, and the right vertical axis is the capacity retention rate (%).

[0101] according to Fig. 9 As the number of cycles increases, the absolute value of dQ / dV increases, and when the number of cycles exceeds approximately 500, dQ / dV decreases. The inflection point of dQ / dV is the switching point from the region (B) to the region (A). At this switching point, the capacity retention rate begins to drop significantly.

[0102] The dQ / dV at the switching point may be set to the first determination value.

[0103] The first determination value is obtained by, for example, an experiment and stored in the estimation data 133. The second determination value may be set based on the use status of the power storage element 200 or the like.

[0104] According to the estimation device 100 of the present embodiment, in the storage element 200 that has changed from the positive electrode limiting type to the negative electrode limiting type, the degradation state of the storage element 200 can be estimated based on the change in dQ / dV at a given measured voltage value within a given voltage range when the storage element 200 is discharged. It is possible to determine whether the storage element has changed from the positive electrode limiting type to the negative electrode limiting type. If it changes to the negative electrode limiting type and the deviation of the capacity balance between the positive and negative electrodes increases, the capacity of the storage element 200 begins to decrease. The remaining life of the storage element 200 can be estimated based on the change in dQ / dV.

[0105] Therefore, the internal state of the power storage element 200 can be estimated.

[0106] The timing for acquiring dQ / dV at the end of discharge of the power storage element 200 may be, for example, during periodic maintenance of the power storage device or during regenerative charging by a charger (charging after temporary full discharge).

[0107] (Implementation Method 2)

[0108] In the second embodiment, an ECU (Electronic Control Unit) functions as an estimation device.

[0109] Fig.10 This is a block diagram showing a vehicle 20 according to the second embodiment.

[0110] The vehicle 20 includes an ECU 400 which is a general ECU such as an engine ECU or an ECU that controls the entire power supply device.

[0111] ECU 400 acquires signals indicating the states of the plurality of power storage elements 200 , determines the internal states of the power storage elements 200 , and controls the discharge state and charge state of the power storage elements 200 .

[0112] ECU 400 includes an information processing unit 410, an estimation unit 420, a storage unit 430, a timing unit 440, and an I / F 450. Sensors 600 such as a current sensor, a voltage sensor, and a temperature sensor for detecting physical quantities such as current value, voltage value, and temperature of each power storage element 200 are connected to the information processing unit 410 via the I / F 450. Here, a plurality of sensors are represented as one "sensor 600". There is also a case where the temperature is not detected by the sensor.

[0113] The storage unit 430 stores an estimation program 431 for estimating the internal state of the storage element 200, charge and discharge history data 432, and estimation data 433. The estimation program 431 may be stored in a computer-readable state in the storage medium 40. In this case, the storage unit 430 stores the estimation program 431 read from the storage medium 40 by a reading device not shown. The estimation program 431 may also be acquired from an external computer not shown connected to the communication network and stored in the storage unit 430.

[0114] The information processing unit 410 acquires the detection information of the physical quantity of each storage element 200 from the sensor 600. The information processing unit 410 measures the timing with reference to the timing unit 440. The information processing unit 410 writes the acquired detection information into the charge and discharge history data 432 of the storage unit 430. By accumulating the detection information of the physical quantity of the storage element 200, the temporal data of the physical quantity can be obtained, which becomes the charge and discharge history record.

[0115] The information processing unit 410 reads the voltage, current, power-on period, etc. when the storage element 200 is discharged from the charge and discharge history data 432, and calculates the power supply amount (Q). dQ / dV is calculated at a given measured voltage value in a given voltage range. The given voltage range is preferably 2.4V to 3.25V. The information processing unit 410 can also calculate the capacity maintenance rate corresponding to dQ / dV based on the calculated capacity.

[0116] The information processing unit 410 writes the acquired dQ / dV, the corresponding voltage, and the usage period (eg, date and time) into the estimation data 433 stored in the storage unit 430. The estimation data 433 is a data table in which "usage period", "voltage", and "dQ / dV" are associated with each other.

[0117] The estimation unit 420 estimates the internal state of the power storage element 200 using dQ / dV acquired by the information processing unit 410. Specifically, the estimation unit 420 determines that the limiting electrode of the power storage element has switched from the positive electrode to the negative electrode when the absolute value of dQ / dV is equal to or greater than a first determination value.

[0118] Then, when the absolute value of dQ / dV becomes equal to or smaller than the second determination value, the estimation unit 420 determines that the power storage element has reached the end of its life.

[0119] According to the ECU 400 of the present embodiment, in the storage element 200 that has changed from the positive electrode limiting type to the negative electrode limiting type, the degradation state of the storage element 200 can be estimated based on the change in dQ / dV at a given measured voltage value within a given voltage range when the storage element 200 is discharged. It is possible to determine whether the storage element has changed from the positive electrode limiting type to the negative electrode limiting type. If it changes to the negative electrode limiting type and the deviation of the capacity balance between the positive and negative electrodes increases, the capacity of the storage element 200 begins to decrease. The remaining life of the storage element 200 can be estimated based on the change in dQ / dV.

[0120] Therefore, the internal state of the power storage element 200 can be estimated.

[0121] (Implementation 3)

[0122] In the third embodiment, the internal state estimation server 500 functions as an estimation device.

[0123] Fig.11 1 is a block diagram showing an internal state estimation server 500 and a power storage device 700 according to the third embodiment.

[0124] The internal state estimation server 500 includes an information processing unit 510 , an estimation unit 520 , a storage unit 530 , a timer unit 540 , and a communication unit 550 .

[0125] The power storage device 700 includes a plurality of power storage elements 200, sensors 600 such as a current sensor, a voltage sensor, and a temperature sensor for detecting physical quantities such as current value, voltage value, and temperature of each power storage element 200, and a control unit 710. Fig.11 In FIG. 6 , a plurality of sensors are represented as one “sensor 600 ”, and only one power storage element 200 is shown.

[0126] The information processing unit 510 is connected to the control unit 710 of the power storage device 700 via the communication unit 550 and the network 30. The information processing unit 510 transmits and receives data to and from the control unit 710 via the network 30.

[0127] The storage unit 530 stores an estimation program 531 for estimating the internal state of the storage element 200, charge and discharge history data 532, and estimation data 533. The estimation program 531 may be stored in a computer-readable state in the storage medium 40. In this case, the storage unit 530 stores the estimation program 531 read from the storage medium 40 by a reading device not shown. The estimation program 531 involved in this embodiment may be obtained from an external computer not shown connected to the communication network and stored in the storage unit 530.

[0128] The information processing unit 510 acquires the detection information of the physical quantity of the storage element 200 from the sensor 600. The information processing unit 510 measures the timing with reference to the timing unit 540. The information processing unit 510 writes the acquired detection information into the charge and discharge history data 532 of the storage unit 530. By accumulating the detection information of the physical quantity of the storage element 200, the temporal data of the physical quantity can be obtained, which becomes the charge and discharge history record.

[0129] The information processing unit 510 reads the voltage, current, power-on period, etc. when the storage element 200 is discharged from the charge and discharge history data 532, and calculates the power supply amount (Q). dQ / dV is calculated at a given measured voltage value in a given voltage range. The given voltage range is preferably 2.4V to 3.25V. The information processing unit 510 can also calculate the capacity maintenance rate corresponding to dQ / dV based on the calculated capacity.

[0130] The information processing unit 510 writes the acquired dQ / dV, the corresponding voltage, and the usage period (for example, date and time) into the estimation data 533 stored in the storage unit 530. The estimation data 533 is a data table in which "usage period", "voltage", and "dQ / dV" are associated with each other.

[0131] The estimation unit 520 estimates the internal state of the storage element 200 using dQ / dV acquired by the information processing unit 510. Specifically, the estimation unit 520 determines that the limiting electrode of the storage element has switched from the positive electrode to the negative electrode when the absolute value of dQ / dV is equal to or greater than a first determination value.

[0132] Then, when the absolute value of dQ / dV becomes equal to or smaller than the second determination value, the estimation unit 520 determines that the power storage element has reached the end of its life.

[0133] According to the internal state estimation server 500 of the present embodiment, in the storage element 200 that changes from the positive electrode limiting type to the negative electrode limiting type, the degradation state of the storage element 200 can be estimated based on the change in dQ / dV at a given measured voltage value within a given voltage range when the storage element 200 is discharged. It is possible to determine whether the storage element has changed from the positive electrode limiting type to the negative electrode limiting type. If it changes to the negative electrode limiting type and the deviation of the capacity balance between the positive and negative electrodes increases, the capacity of the storage element 200 begins to decrease. The remaining life of the storage element 200 can be estimated based on the change in dQ / dV.

[0134] Therefore, the internal state of the power storage element 200 can be estimated.

[0135] To summarize the above, the estimation device estimates the internal state of the storage element, the storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changing from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode. The estimation device comprises: an acquisition unit that acquires a voltage value and a current flow of the storage element within a given voltage range or a given measured voltage value; and an estimation unit that estimates the internal state of the storage element using the voltage value and the current flow.

[0136] According to the above structure, in a storage element that changes from a positive electrode limiting type to a negative electrode limiting type with use (cycling), the degradation state of the storage element can be estimated based on the voltage value and the amount of current flow within a given voltage range or a given measured voltage value when the storage element is discharged. It is possible to determine whether the storage element has changed from a positive electrode limiting type to a negative electrode limiting type. If it changes to a negative electrode limiting type and the deviation of the capacity balance between the positive and negative electrodes increases, the capacity of the storage element begins to decrease. The remaining life of the storage element can be estimated based on the voltage value and the amount of current flow (for example, the change in dQ / dV).

[0137] Therefore, it is possible to estimate the internal state of the power storage element (whether it is a positive electrode limiting type or a negative electrode limiting type, how the power storage element will deteriorate in the near future, and what is the remaining life of the power storage element).

[0138] The estimation unit may determine whether dQ / dV obtained from the voltage value and the amount of energization has reached a first determination value or an inflection point.

[0139] The first determination value is arbitrarily set so as to determine whether the storage element has changed from the positive limiting type to the negative limiting type. According to the above configuration, since it is possible to determine whether the storage element has changed from the positive limiting type to the negative limiting type, it is possible to accurately estimate how the storage element will deteriorate in the near future.

[0140] The estimation unit may determine whether the dQ / dV has reached a second determination value.

[0141] The second determination value is arbitrarily set so that it can be determined that the storage element has reached the end of its life. According to the above configuration, it is possible to easily determine whether the storage element has reached the end of its life.

[0142] The given voltage range may be a voltage range in which the potential of the negative electrode is greater than a first preset value, or may be a voltage range in which the potential of the negative electrode is less than a second preset value.

[0143] In this range, the voltage characteristically drops sharply as the number of charge and discharge repetitions increases. The absolute value of dQ / dV at a given measured voltage value in this voltage range increases as the number of charge and discharge repetitions increases. When the number of repetitions increases further, the absolute value of dQ / dV decreases.

[0144] Therefore, it is easy to monitor / estimate the internal state of the power storage element.

[0145] The power storage device comprises: a positive electrode, a x ) of a negative electrode having a negative electrode active material and a non-aqueous electrolyte and a positive electrode-restricted type storage element whose discharge capacity is restricted by the positive electrode; and the above-mentioned estimation device.

[0146] According to the above configuration, for example, the internal state of the power storage element can be estimated by a CMU or a BMU built into or integrated with the power storage device.

[0147] The ECU has a positive electrode, including silicon oxide (SiO x ) and a negative electrode of a negative electrode active material and a non-aqueous electrolyte and the internal state of the storage element is estimated from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode. The ECU comprises: an acquisition unit that acquires dQ / dV based on a voltage value and a current flow rate within a given voltage range or a given measured voltage value of the storage element; and an estimation unit that estimates the internal state of the storage element using the dQ / dV.

[0148] According to the above configuration, the internal state of the power storage element can be estimated by the ECU mounted on the vehicle.

[0149] The server has a positive electrode, including silicon oxide (SiO x) and a negative electrode of a negative electrode active material and a non-aqueous electrolyte and the internal state of the storage element changes from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode. The server comprises: an acquisition unit that acquires dQ / dV based on a voltage value and a current flow rate within a given voltage range or a given measured voltage value of the storage element; and an estimation unit that estimates the internal state of the storage element using the dQ / dV.

[0150] According to the above configuration, the internal state of the power storage element can be estimated remotely.

[0151] The estimation method is effective for a positive electrode including a silicon oxide (SiO x ) and a negative electrode of a negative electrode active material and a non-aqueous electrolyte, and the internal state of the storage element changes from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode. The estimation method acquires dQ / dV based on a voltage value and a current flow rate within a given voltage range or a given measured voltage value of the storage element, and uses the dQ / dV to estimate the internal state of the storage element.

[0152] According to the above configuration, the internal state of the power storage element can be estimated based on the change in dQ / dV in a given voltage range or a given measured voltage value of the power storage element that changes from a positive electrode limiting type to a negative electrode limiting type.

[0153] The computer program enables the use of a positive electrode, including a silicon oxide (SiO x ) has a negative electrode and a non-aqueous electrolyte of a negative electrode active material and changes from a positive electrode limited type in which the discharge capacity is limited by the positive electrode to a negative electrode limited type in which the discharge capacity is limited by the negative electrode, and performs the following processing: dQ / dV is obtained based on the voltage value and the amount of power flow within a given voltage range or a given measured voltage value of the storage element, and the internal state of the storage element is estimated using the dQ / dV.

[0154] The computer-readable storage medium stores the above-mentioned computer program.

[0155] According to the above configuration, the internal state of the storage element can be estimated by any computer based on the change in dQ / dV in a given voltage range or a given measured voltage value of the storage element when the storage element changes from a positive electrode limiting type to a negative electrode limiting type.

[0156] The present invention is not limited to the contents of the above-mentioned embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

[0157] Explanation of symbols

[0158] 10. Electricity storage device;

[0159] 20 vehicles;

[0160] 40 storage medium;

[0161] 100 estimation device;

[0162] 110 Information Processing Department (Acquisition Department);

[0163] 120 Estimates Department;

[0164] 130, 430, 530 storage units;

[0165] 131, 431, 531 estimation procedures;

[0166] 200 storage elements;

[0167] 201 containers;

[0168] 202 electrode terminal;

[0169] 300 accommodating housing;

[0170] 400ECU;

[0171] 500 Internal state estimation server.

Claims

1. An estimation device for estimating an internal state of an electric storage element, the electric storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changing from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: The estimation device comprises: an acquisition unit that acquires a voltage value and a current flow amount of the power storage element within a given voltage range or a given measured voltage value; and an estimating unit that estimates an internal state of the power storage element using the voltage value and the amount of energization, thereby determining whether the power storage element has changed from a positive electrode limiting type to a negative electrode limiting type, The estimation unit determines whether the absolute value of dQ / dV obtained based on the voltage value and the amount of current flow is greater than a first judgment value or has reached an inflection point which is a maximum value. When the absolute value of dQ / dV is greater than the first judgment value or has reached the inflection point, it is determined that the energy storage element has changed from a positive pole limiting type to a negative pole limiting type.

2. The estimation device according to claim 1, wherein: The estimation unit determines whether the power storage element is a positive electrode limiting type or a negative electrode limiting type using the voltage value and the amount of energization.

3. The estimation device according to claim 1, wherein: The estimation section determines whether the dQ / dV reaches a second determination value after reaching the first determination value or the inflection point.

4. The estimation device according to claim 1 or 2, wherein: The given voltage range is a voltage range in which the potential of the negative electrode is greater than or equal to a first preset value, or a voltage range in which the potential of the negative electrode is less than or equal to a second preset value.

5. A method for estimating the internal state of an electric storage element, wherein the electric storage element has a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changes from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: Acquiring a voltage value and a current flow of the power storage element within a given voltage range or a given measured voltage value; The voltage value and the amount of current flow are used to estimate the internal state of the energy storage element, so as to determine whether the energy storage element has changed from a positive pole limiting type to a negative pole limiting type, wherein it is determined whether the absolute value of dQ / dV obtained based on the voltage value and the amount of current flow is above a first judgment value or has reached an inflection point which is a maximum value. When the absolute value of dQ / dV is above the first judgment value or has reached the inflection point, it is determined that the energy storage element has changed from a positive pole limiting type to a negative pole limiting type.

6. A computer-readable storage medium storing a computer program that causes a computer to estimate an internal state of an electric storage element, the electric storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changing from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: The computer program causes the computer to execute the following processing: Acquiring a voltage value and a current flow of the power storage element within a given voltage range or a given measured voltage value; The voltage value and the amount of current flow are used to estimate the internal state of the energy storage element, so as to determine whether the energy storage element has changed from a positive pole limiting type to a negative pole limiting type, wherein it is determined whether the absolute value of dQ / dV obtained based on the voltage value and the amount of current flow is above a first judgment value or has reached an inflection point which is a maximum value. When the absolute value of dQ / dV is above the first judgment value or has reached the inflection point, it is determined that the energy storage element has changed from a positive pole limiting type to a negative pole limiting type.

7. An estimation device for estimating the internal state of an electric storage element, the electric storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changing from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: The estimation device comprises: an estimating unit that estimates an internal state of the storage element based on information about a shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is greater than or equal to a first preset value, or information about a shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is less than or equal to a second preset value, thereby determining whether the storage element has changed from a positive electrode limiting type to a negative electrode limiting type, The shape of the discharge curve changes in the order of a first state, a second state having a gentler slope than the first state, and a third state having a steeper slope than the second state, and the estimation unit determines that the power storage element has changed from a positive electrode limiting type to a negative electrode limiting type when the shape of the discharge curve changes from the second state to the third state.

8. The estimation device according to claim 7, wherein: The estimation unit determines whether the power storage element is a positive electrode limiting type or a negative electrode limiting type based on information on the shape of the discharge curve.

9. The estimation device according to claim 7 or 8, wherein: The estimation unit estimates an internal state of the power storage element based on a change in a shape of a discharge curve of the power storage element in the voltage range.

10. A method for estimating the internal state of an electric storage element, the electric storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and the electric storage element changes from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: estimating the internal state of the storage element, thereby determining whether the storage element has changed from a positive electrode limiting type to a negative electrode limiting type, based on information about the shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is greater than a first preset value or information about the shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is less than a second preset value, The shape of the discharge curve changes in the order of a first state, a second state having a gentler slope than the first state, and a third state having a steeper slope than the second state. When the shape of the discharge curve changes from the second state to the third state, it is determined that the storage element changes from a positive electrode limiting type to a negative electrode limiting type.

11. A computer-readable storage medium storing a computer program that causes a computer to estimate an internal state of an electric storage element, the electric storage element having a positive electrode, a negative electrode including a negative electrode active material containing silicon oxide (SiOx), and a non-aqueous electrolyte, and changing from a positive electrode-limited type in which the discharge capacity is limited by the positive electrode to a negative electrode-limited type in which the discharge capacity is limited by the negative electrode, wherein: The computer program causes the computer to execute the following processing: estimating the internal state of the storage element, thereby determining whether the storage element has changed from a positive electrode limiting type to a negative electrode limiting type, based on information about the shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is greater than a first preset value or information about the shape of a discharge curve of the storage element in a voltage range in which the potential of the negative electrode is less than a second preset value, The shape of the discharge curve changes in the order of a first state, a second state having a gentler slope than the first state, and a third state having a steeper slope than the second state. When the shape of the discharge curve changes from the second state to the third state, it is determined that the storage element changes from a positive electrode limiting type to a negative electrode limiting type.

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