JP2015065119A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device performing charge and discharge control which is less likely to cause performance degradation of power storage elements.SOLUTION: A power storage device includes one or a plurality of power storage elements consisting of a positive electrode and a negative electrode, and a control section for controlling the power storage elements. The negative electrode active material of the power storage elements contains at least graphite. The control section diagnoses in which of the positive electrode or negative electrode the reaction rate is limiting, based on the discharge curve when first discharge is performed and the discharge curve when second discharge is performed at a discharge rate lower than that in the first discharge, and sets an operation range of the power storage elements depending on the results of diagnosis.

Description

  The present invention relates to a power storage device.

  When long-term use is assumed, such as in-vehicle lithium ion secondary batteries, there is a need for longer life. However, the progress of deterioration of a lithium ion secondary battery changes according to its usage history. In particular, depending on the range of the voltage used (or SOC (State Of Charge)), there is a region that deteriorates rapidly. Therefore, it is necessary to appropriately set the operating voltage range or the operating SOC range according to the deterioration state.

  Patent Document 1 discloses an invention in which an upper limit voltage (or upper limit SOC) is increased in accordance with capacity deterioration of a lithium ion battery to increase a usable voltage range (or SOC range).

  However, the deterioration phenomenon of the lithium ion battery varies depending on the positive electrode and the negative electrode. Specifically, the positive electrode tends to deteriorate at the end of discharge (low SOC, low battery voltage), and the negative electrode deteriorates at early discharge (high SOC, high battery voltage, close to full charge). It's easy to do. And the performance of a lithium ion battery largely depends on the side where deterioration of the positive electrode and the negative electrode is progressing. That is, the reaction rate-determining depends on the electrode whose deterioration is progressing.

JP 2012-85452 A

  Therefore, charge / discharge control of the battery is required so that the electrode that is mainly deteriorated does not deteriorate any more.

  The power storage device of the invention according to claim 1 includes one or a plurality of power storage elements composed of a positive electrode and a negative electrode, and a control unit that controls the power storage element, and the active material of the negative electrode of the power storage element includes at least graphite, Based on the discharge curve when the first discharge is performed and the discharge curve when the second discharge having a discharge rate lower than the first discharge is performed, the control unit determines whether the reaction rate limiting of the power storage element is positive or negative. And the operating range of the storage element (storage element operating range) is set according to the diagnosis result.

  According to the present invention, a long-life battery and a long-life power storage device can be provided.

1 is a partially cutaway view of a secondary battery according to an embodiment of the present invention. The schematic block diagram of the electrical storage apparatus of one Embodiment of this invention. The schematic block diagram of the electrical storage apparatus of one Embodiment of this invention. The secondary battery of one Embodiment of this invention WHEREIN: The figure which showed the difference in the discharge curve in case the reaction rate control is a positive electrode, and a negative electrode. 1 is a flowchart of a power storage device according to an embodiment of the present invention. The evaluation result of an Example.

--Embodiment--
FIG. 1 is a diagram showing a lithium ion secondary battery 10 (hereinafter also simply referred to as a single battery 10) of the present embodiment. In the battery container 26 of the unit cell 10, a positive electrode plate 11 using a composite lithium oxide as an active material and a negative electrode plate 12 using a material holding lithium ions as an active material are wound in a spiral shape via a separator 13. The produced electrode winding group 22 is accommodated together with a predetermined electrolytic solution.

  Examples of the positive electrode active material applied to the positive electrode plate 11 include lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (some of them). Nickel substituted with cobalt), lithium manganate and modified products thereof, and composite oxides thereof (nickel, cobalt, manganese, iron, aluminum, molybdenum). In addition, an olivine compound or a spinel type lithium manganese compound can be used alone, or an oxide obtained by combining the above compounds can be used.

  As the conductive material for the positive electrode, for example, carbon black and various graphites such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black can be used alone or in combination.

  As the positive electrode binder, for example, polyvinylidene fluoride (PVDF), a modified polyvinylidene fluoride, polytetrafluoroethylene (PTFE), a rubber particle binder having an acrylate unit, and the like can be used. It is also possible to mix an acrylic monolate monomer into which a reactive functional group is introduced or an acrylate oligomer in the binder.

  As the negative electrode active material applied to the negative electrode plate 12, various natural graphites or artificial graphites are used, or materials obtained by mixing various natural graphites or artificial graphites with amorphous carbon (non-graphitizable carbon, graphitizable carbon). Can be used.

  As the binder for the negative electrode, various binders such as PVDF and modified products thereof can be used. From the viewpoint of improving the acceptability of lithium ions, styrene-butadiene copolymer (SBR) and modified products thereof are added to carboxy. It is more preferable to use a cellulose-based resin such as methylcellulose (CMC) in combination or to add a small amount.

  At this time, as the negative electrode conductive material, for example, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and various graphites can be used alone or in combination.

  The separator is not particularly limited as long as it can withstand the range of use of the lithium ion secondary battery, but it is common to use a single layer or a composite of olefinic microporous films such as polyethylene and polypropylene. is there. The thickness of this separator is preferably 10 to 40 μm.

Regarding the electrolytic solution, various lithium compounds such as LiPF ₆ and LiBF ₄ can be used as the electrolyte salt. Further, ethylene carbonate (EC), dimethyl cardnate (DMC) diethyl carbonate (DEC) can be used alone or in combination as a solvent. In addition, it is preferable to use vinylene carbonate (VC), cyclohexylbenzene (CHB), or a modified product thereof in order to form a good film on the positive electrode and the negative electrode and to ensure stability during overcharge / discharge.

  The shape of the electrode winding group in the present embodiment is not necessarily a true cylindrical shape, and may be a long cylindrical shape having an elliptic winding group cross section or a prismatic shape having a rectangular winding cross section. A typical form of use is a cylindrical shape, in which a battery can with a bottom is filled with an electrode winding group and an electrolyte, and a tab for taking out current from the electrode plate is sealed in a state welded to the cap and the battery can. Are preferred.

  In addition, the battery can that fills the electrode winding group is not particularly limited. However, such as a battery can plated with iron for corrosion resistance, a stainless steel battery can, etc., strength, corrosion resistance, processing Those having excellent properties are preferred. Also, aluminum alloys and various engineering plastics can be used in combination with metals.

  FIG. 2 is a diagram illustrating the power storage device of the present embodiment. In the power storage device, N (N is an integer of 1 or more) secondary battery modules 50-1 to 50-N are connected in parallel, and the N secondary battery modules 50-1 to 50 are connected by one battery controller 52. -N is configured to control charging and discharging. Each of the secondary battery modules 50-1 to 50-N includes an assembled battery 41 that is a storage element, a voltage detector 42 that detects the voltage of the assembled battery 41, and a current detector 43 that detects the current of the assembled battery 41. A temperature detector 44 for detecting the temperature of the assembled battery 41, a switch device 45 for independently charging / discharging the plurality of single cells 10 constituting the assembled battery 41, and charging / discharging of the assembled battery 41 A cell controller 51 for controlling each of them is provided.

  The assembled battery 41 is configured by connecting a plurality of the unit cells 10 shown in FIG. 1 in series. However, the assembled battery 41 may be an assembled battery connected in series or parallel, or an assembled battery connected in parallel. Further, when a secondary battery module is configured by connecting N assembled batteries 41 in series, the positive electrode of the assembled battery 41 having the highest potential and the negative electrode of the assembled battery 41 having the lowest potential are connected via an inverter to an electric motor or the like. Connected to the load.

The current detector 43 detects the current of each unit cell 10 constituting the assembled battery 43. The current detector 43 can use a galvanometer, a shunt resistor, or a clamp meter, but is not limited thereto.
The temperature detector 44 detects the temperature of the assembled battery 41. The temperature detector 44 can use, for example, a thermocouple or a thermistor, but is not limited thereto. The temperature detector 44 can be used as the assembled battery temperature by measuring the surface temperature of the assembled battery 41, the internal temperature, the surface temperature of the housing that houses the assembled battery, or the temperature around the assembled battery 41. .

  Both the cell controller 51 and the battery controller 52 have a CPU, a ROM, a RAM, and other peripheral circuits. The arrow attached to the battery controller 52 means that the battery controller 52 receives a command from a host controller (not shown) having a determination unit that determines the state of future use of the assembled battery 41. The cell controller 51 performs charge / discharge control of the assembled battery 41 according to a predetermined program in accordance with a command from the battery controller 52.

  The cell controller 51 has a built-in timer and measures the discharge time of the assembled battery 41 and the like. Further, the time for diagnosing the deterioration state of the positive electrode and the negative electrode, that is, the time for diagnosing whether the reaction rate control is the positive electrode or the negative electrode is stored, and it is determined whether or not the time is to be diagnosed according to an instruction from the battery controller 52.

  The configuration and operation of the battery controller 52 will be described using the system block diagram of FIG. The cell controller 51 transmits to the data recording unit 521 of the battery controller 52 the voltage, current and temperature of the assembled battery 41, the time relating to the charge / discharge, and the capacity data calculated from the current and time. Based on the data received by the data recording unit 521, the battery state calculation unit 522 calculates the data. The battery state detection unit 523 detects the battery state from the result calculated by the battery state calculation unit 522. The diagnosis of the deterioration state of the assembled battery 41 (diagnosis as to whether the reaction rate is positive or negative) is performed according to the detected result, and the diagnosis result of the deterioration state is transmitted to the cell controller 51. The cell controller 51 sets the operating voltage range or operating SOC range of the battery according to the diagnosis result of the deterioration state of the assembled battery 41, and performs charge / discharge control with the switch 45.

  FIG. 4 is a diagram showing a discharge curve in the assembled battery 41. Here, the discharge curve is the capacity (or SOC) dependence of the voltage behavior of the battery. The following description of FIG. 4 is for the assembled battery, but this is the same for the unit cell 10. FIG. 4A is a diagram showing a discharge curve when the positive electrode of the unit cell 10 constituting the assembled battery 41 is mainly deteriorated, that is, when the reaction rate control is the positive electrode. The horizontal axis indicates the capacity, and the vertical axis indicates the battery voltage. The right side of the figure shows the initial stage of discharge (a state near full charge), and the left side of the figure shows the end stage of discharge. FIG. 4 (a) shows two types of discharge curves. These differ in the discharge rate. A discharge having a high discharge rate is referred to as a first discharge. The specific discharge rate of the first discharge is equivalent to 1C. On the other hand, a discharge having a low discharge rate is referred to as a second discharge. The specific discharge rate of the second discharge is equivalent to 0.02C. The discharge curve during the first discharge connects from coordinates (0, Vs) to coordinates (Q1, Ve). Here, Vs is a reference battery voltage (reference voltage Vs) in the vicinity of full charge, Ve is a battery voltage at the end of discharge (end voltage Ve), and Q1 is a discharge capacity at the time of first discharge. The discharge curve at the time of the second discharge connects from coordinates (0, Vs) to coordinates (Q2, Ve). Here, Q2 is the discharge capacity at the time of the second discharge, and takes a value larger than Q1. FIG. 4B is a diagram showing a discharge curve when the negative electrode of the unit cell 10 constituting the assembled battery 41 is mainly deteriorated, that is, when the reaction rate is the negative electrode. Since the difference between FIG. 4 (a) and FIG. 4 (b) is only the following points, detailed description of FIG. 4 (b) is omitted. V2 will be described in the description of FIG.

  There is no difference between the behavior of the discharge curve of the second discharge in FIG. 4A and the behavior of the discharge curve of the second discharge in FIG. On the other hand, between the behavior of the discharge curve of the first discharge in FIG. 4A and the behavior of the discharge curve of the first discharge in FIG. The discharge curve of the first discharge in FIG. 4 (a) reaches Ve with a smaller discharge amount than the discharge curve of the first discharge in FIG. 4 (b). That is, the discharge capacity Q1 in FIG. 4A is smaller than the discharge capacity Q1 in FIG. 4A and the discharge capacity Q1 in FIG. 4B. As a result, the difference (Q2-Q1) between the discharge capacity Q1 and the discharge capacity Q2 is smaller when the reaction rate control shown in FIG. 4 (b) is the negative electrode than when the reaction rate control shown in FIG. 4 (a) is the positive electrode. The assembled battery 41 has the following characteristics. The battery controller 52 of the power storage device of the present invention uses this characteristic to diagnose whether the positive electrode is deteriorated or the negative electrode is deteriorated. There are other indicators besides Q2-Q1, which will be described later in the explanation of step S6 shown in FIG.

  In any of the discharge curves shown in FIG. 4, the battery discharge curve changes monotonically with respect to the capacity, such that the battery voltage is high at the beginning of discharge and the battery voltage is low at the end of discharge. In other words, the discharge curve of the battery changes monotonously with respect to the SOC. Thus, since the discharge curve of the battery changes monotonously with respect to the SOC, the battery voltage and the SOC correspond one-to-one in one discharge curve. The same applies to the operating voltage range and the operating SOC range of a battery. When the operating voltage range of a certain battery is determined, a certain operating SOC range is uniquely determined. Therefore, for the sake of simplicity, hereinafter, the above-mentioned “battery operating voltage range or operating SOC range” will be collectively referred to as “storage element operating range”.

  The operating range of the electricity storage element in the present invention varies depending on which of the positive electrode and the negative electrode is mainly deteriorated. As described above, the positive electrode tends to deteriorate at the end of discharge and the negative electrode tends to deteriorate at the beginning of discharge. When the positive electrode is mainly deteriorated, it is necessary to prevent further deterioration of the positive electrode. Therefore, the storage element operating range is set to a range that does not include the end-of-discharge side. For example, the storage element operating range is set on the high voltage side (high SOC side). On the other hand, when the negative electrode is mainly deteriorated, it is necessary to prevent the negative electrode from further deterioration. Therefore, the storage element operating range is set to a range not including the initial discharge side. For example, the storage element operating range is set on the low voltage side (low SOC side).

  FIG. 5 is a flowchart showing a charge / discharge control method of the battery controller 52 of the power storage device of the present invention. The flow shown in this figure is periodically executed by executing the program of the battery controller 52 at a predetermined cycle. The period from the previous flow to the current flow is predetermined. In step S1, control of the battery controller 52 is started. In step S2, the battery controller 52 causes the cell controller 51 to determine whether or not it is a diagnosis time for diagnosing whether the reaction rate-limiting is positive or negative based on a determination criterion described later. If it is determined that it is the diagnosis time, the process proceeds to step S3. If it is determined that it is not the diagnosis time, the process proceeds to step S8. Further, the cell controller 51 sends a signal to the battery controller 52 regarding the determination result in step S <b> 2. Parameters for determining whether or not it is the diagnosis time in step S2 include the elapsed period from the previous diagnosis time, the travel distance from the previous diagnosis time, the total charge / discharge capacity from the previous diagnosis time, the previous diagnosis There are the number of charge / discharge cycles from the time, the current battery voltage, the current SOC, the current remaining fuel amount, and the like. By combining one or more of these determination criterion parameters, it is possible to determine whether or not it is a diagnosis time.

In step S3, the battery controller 52 first instructs the cell controller 51 to perform the first discharge, and causes the assembled battery 41 to execute the first discharge from the reference voltage Vs until the end voltage Ve is reached. The discharge curve is recorded. Thereafter, the battery controller 52 instructs the cell controller 51 to perform the second discharge, and causes the assembled battery 41 to execute the second discharge until the end voltage Ve is reached starting from the reference voltage Vs, and the discharge curve thereof. To record. At this time, the cell controller 51 records the time from the start of the first discharge to the end of the second discharge, voltage, current, temperature, and the like as measurement data.
In step S4, the battery controller 52 receives the measurement data obtained in step S3 from the cell controller 51.

  In step S5, the battery controller 52 calculates an index for diagnosing whether the reaction rate limiting is positive or negative based on the measurement data obtained in step S3. Here, it demonstrates with reference to FIG. As the above-mentioned index, a value Q2-Q1 obtained by subtracting the discharge capacity Q1 at the first discharge from the discharge capacity Q2 at the second discharge is suitable. The discharge capacity ratio Q1 / Q2 can also be an index. Or voltage V2 defined by Q1 on the discharge curve at the time of the 2nd discharge can also serve as an index.

  In step S6, the battery controller 52 compares the index calculated in step S5 with a predetermined threshold value, and diagnoses whether the reaction rate is positive or negative. Specifically, when the difference is Q2-Q1, if Q2-Q1 is larger than a predetermined threshold, it is diagnosed that the positive electrode is mainly deteriorated (reaction rate limiting is positive), and Q2-Q1 is lower than the predetermined threshold. If it is smaller, the negative electrode is diagnosed as being mainly deteriorated (reaction rate limiting is the negative electrode). When the index is the ratio Q1 / Q2, if the Q1 / Q2 is smaller than a predetermined threshold, the positive electrode is mainly diagnosed as being deteriorated (reaction rate limiting is positive), and if the Q1 / Q2 is larger than the predetermined threshold, the negative electrode Is mainly degraded (reaction rate limiting is negative electrode). When the index is the voltage V2, if the V2 is larger than a predetermined threshold, the positive electrode is diagnosed as being mainly deteriorated (reaction rate is positive), and if the V2 is smaller than the predetermined threshold, the negative electrode is mainly deteriorated (reaction). Diagnose that rate-limiting is negative electrode). It should be noted that an appropriate value is set as the predetermined threshold value in accordance with the above-described index. As described above, the positive electrode tends to deteriorate at the end of discharge and the negative electrode tends to deteriorate at the beginning of discharge. From this, when the reaction rate limiting is diagnosed as the positive electrode, the storage element operating range is set to the high voltage side (high SOC side) so as not to include the end-of-discharge side in order to prevent the positive electrode from further deterioration. . On the other hand, when the reaction rate limiting is diagnosed as the negative electrode, the storage element operating range is set to the low voltage side (low SOC side) so as not to include the initial discharge side in order to prevent the negative electrode from further deterioration.

In step S <b> 7, the battery controller 52 transmits the storage element operating range determined in step S <b> 6 to the cell controller 51.
In step S8, the control of the battery controller 52 is terminated.

The power storage device of the present invention has the following configuration and exhibits the following operational effects.
(1) One or a plurality of assembled batteries 41 (storage elements) each including a positive electrode and a negative electrode, and a cell controller 51 and a battery controller 52 (control unit) that control the assembled battery 41 are provided. The active material of the negative electrode of the assembled battery 41 includes at least graphite. In response to an instruction from the battery controller 52, the cell controller 51 performs the first discharge and the second discharge, which is a discharge having a discharge rate lower than that of the first discharge, on the assembled battery 41. The battery controller 52 diagnoses whether the reaction rate limiting of the assembled battery 41 is positive or negative based on the discharge curve when the first discharge is executed and the discharge curve when the second discharge is executed. Then, according to the diagnosed result, the operating range of the assembled battery 41 (hereinafter referred to as a storage element operating range) is set, and information on the storage element operating range is transmitted to the cell controller 51. Therefore, the cell controller 51 performs charge / discharge control of the assembled battery 41 within the battery operating range described above. Thereby, the battery capacity deterioration of the assembled battery 41 can be suppressed, and the assembled battery 41 can be extended in life. As the assembled battery 41 extends its life, the power storage device also extends its life.

(2) A specific index for diagnosis may be Q2-Q1 shown below. The battery controller 52 of the power storage device measures a discharge capacity Q1 which is a capacity discharged by the first discharge and a discharge capacity Q2 which is a capacity discharged by the second discharge, and subtracts the discharge capacity Q1 from the discharge capacity Q2. Calculated values Q2-Q1. If Q2-Q1 is larger than a predetermined threshold value, it is diagnosed that the reaction rate-limiting of the power storage element is a positive electrode, the power storage element operating range is set so as not to include the end-of-discharge side, and Q2-Q1 is smaller than the predetermined threshold value. For example, it is diagnosed that the reaction rate limiting of the electricity storage element is a negative electrode, and the electricity storage element operating range is set so as not to include the initial discharge side. As a result, the deterioration rate of the battery can be reduced while maintaining the usable SOC width, so that the life of the storage battery and the power storage system can be extended.

(3) A specific index for diagnosis may be Q1 / Q2. The battery controller 52 of the power storage device measures a discharge capacity Q1 which is a capacity discharged by the first discharge and a discharge capacity Q2 which is a capacity discharged by the second discharge, and divides the discharge capacity Q1 by the discharge capacity Q. The calculated value Q1 / Q2 is calculated. If Q1 / Q2 is smaller than a predetermined threshold value, it is diagnosed that the reaction rate limiting of the power storage element is positive, the power storage element operating range is set so as not to include the end stage of discharge, and Q1 / Q2 is larger than the predetermined threshold value. For example, it is diagnosed that the reaction rate limiting of the electricity storage element is a negative electrode, and the electricity storage element operating range is set so as not to include the initial discharge side. Thereby, the deterioration rate of the battery can be reduced while maintaining the usable SOC width.

(4) A specific index for diagnosis may be V2 shown below. The battery controller 52 of the power storage device measures the discharge capacity Q1, which is the capacity discharged by the first discharge. If the voltage value V2 at Q1 of the second discharge curve is larger than a predetermined threshold, the reaction rate limiting of the power storage element is positive. If the storage element operating range is set so as not to include the end-of-discharge side, and the voltage value V2 is smaller than a predetermined threshold value, it is diagnosed that the reaction rate limiting of the storage element is negative, The operating range of the storage element is set so as not to include the side. Thereby, the deterioration rate of the battery can be reduced while maintaining the usable SOC width.

--Example--
Here, the difference in battery capacity deterioration between Example 1 in which control is performed to switch the operating SOC range (storage element operating range), and Comparative Example 1 and Comparative Example 2 in which the control to switch the operating SOC range is not performed will be described. The necessity of switching control of the operating SOC range will be described.

  In both Example 1 and Comparative Examples 1 and 2, the unit cell 10 described in the embodiment was used. As the electrode material of the unit cell 10, layered lithium Mn oxide was used as the positive electrode active material, carbon black was used as the conductive material, and polyvinylidene fluoride was used as the binder. As the negative electrode active material, natural graphite was used, and as the binder, a material in which styrene-butadiene copolymer (binder resin) and carboxymethyl cellulose were mixed at a ratio of 98: 1: 1 was used. The size and shape of the unit cell 10 is a cylindrical shape having a diameter of 18 mm and a length of 65 mm.

  The number of charge / discharge cycles was 2000, and a cycle test was conducted at an environmental temperature of 50 ° C. in order to accelerate capacity deterioration. The charge rate during the charge / discharge cycle is 0.5C, and the discharge rate is 1C. In the cycle of Example 1, the operating SOC range is selected from the range of 0 to 80% or the range of 20 to 100% based on the diagnosis result whether the reaction rate is positive or negative. In the cycle of Comparative Example 1, the operating SOC range is fixed to a range of 0 to 80%. In the cycle of Comparative Example 2, the operating SOC range is fixed to a range of 20 to 100%. Here, a specific operating SOC range that does not include the initial stage of discharge, that is, an operating SOC range in which the negative electrode hardly deteriorates, is set to a range of 0 to 80%. A specific operating SOC range that does not include the end of discharge, that is, an operating SOC range in which the positive electrode hardly deteriorates is set to a range of 20 to 100%.

  In Example 1, it was diagnosed whether the reaction rate-limiting was the positive electrode or the negative electrode. Diagnosis was made once every 400 cycles. The discharge rates of the first discharge and the second discharge performed at the time of diagnosis are as follows. The discharge rate in the first discharge was 1C. The discharge rate in the second discharge was 0.02C.

  Under the above conditions, the battery capacity after carrying out a cycle test of 2000 cycles in Example 1, Comparative Example 1, and Comparative Example 2 was measured, and the results were compared with the capacity maintenance rate that is an index indicating the deterioration of the battery. . The measurement results are shown in the table of FIG. In FIG. 6, the capacity retention rate in Example 1 which is an example of the present invention was 86%. In Comparative Example 1, it was 75%. In Comparative Example 2, it was 81%. Therefore, the capacity retention rate was higher when the present invention was applied than when the conventional technique was applied. From the above, since the battery capacity deterioration of the secondary battery can be suppressed by controlling the operating SOC range by applying the present invention, a long-life secondary battery system can be provided. In addition, in the said Example, although implemented with the cell 10, even when it implements with the assembled battery 41, it becomes a result similar to a cell.

  The present invention is not limited to the above-described embodiments and examples, and can be applied with appropriate modifications without departing from the scope of the invention. For example, the battery is a wound lithium ion secondary battery, but the present invention is applied to a stacked lithium ion secondary battery in which a plurality of positive plates and a plurality of negative plates are alternately stacked via separators. May be. For example, a lithium ion secondary battery is used as the storage element, but a lithium ion capacitor may be used.

11: positive electrode plate 12: negative electrode plate 13: separator 22: electrode winding group 26: battery container 41: assembled battery 42: voltage detection unit 43: current detection unit 44: temperature detection unit 51: cell controller 52: battery controller Q1, Q2: Discharge capacity V2: Voltage

Claims (4)

One or more power storage elements comprising a positive electrode and a negative electrode;
A control unit for controlling the power storage element,
The negative electrode active material of the electricity storage element includes at least graphite,
The control unit includes a discharge curve when the first discharge is executed (hereinafter, a first discharge curve) and a discharge curve when the second discharge having a discharge rate lower than the first discharge is executed (hereinafter, Based on the second discharge curve), it is diagnosed whether the reaction rate-limiting of the electricity storage element is the positive electrode or the negative electrode, and the operation range of the electricity storage element (hereinafter, electricity storage element operation) is determined according to the diagnosis result. Range) is set. The power storage device according to claim 1,
The controller is
A discharge capacity Q1 which is a capacity discharged by the first discharge and a discharge capacity Q2 which is a capacity discharged by the second discharge are respectively measured, and a value Q2− which is obtained by subtracting the discharge capacity Q1 from the discharge capacity Q2. Calculate Q1,
If the Q2-Q1 is larger than a predetermined threshold, the storage element reaction range is diagnosed as a positive electrode, and the storage element operating range is set so as not to include the end-of-discharge side,
If the Q2-Q1 is smaller than a predetermined threshold value, the power storage device that diagnoses that the reaction rate limiting of the power storage element is a negative electrode and sets the power storage element operating range so as not to include the initial discharge side. The power storage device according to claim 1,
The controller is
A discharge capacity Q1 which is a capacity discharged by the first discharge and a discharge capacity Q2 which is a capacity discharged by the second discharge are respectively measured, and a value Q1 / which is obtained by dividing the discharge capacity Q1 by the discharge capacity Q. Calculate Q2,
If Q1 / Q2 is smaller than a predetermined threshold, diagnose that the reaction device's reaction rate-limiting is positive, and set the storage element operating range so as not to include the end-of-discharge side,
If the Q1 / Q2 is larger than a predetermined threshold, the power storage device that diagnoses that the reaction rate limiting of the power storage element is a negative electrode and sets the power storage element operating range so as not to include the initial discharge side. The power storage device according to claim 1,
The controller is
Measuring a discharge capacity Q1 which is a capacity discharged by the first discharge;
If the voltage value V2 at Q1 of the second discharge curve is greater than a predetermined threshold value, the storage element operating range is set so as not to include the end-of-discharge side by diagnosing that the reaction rate limiting of the storage element is positive. ,
If the voltage value V2 is smaller than a predetermined threshold value, the power storage device that diagnoses that the reaction rate limiting of the power storage element is a negative electrode and sets the power storage element operating range so as not to include the initial discharge side.

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