JP2014109477A - Deterioration state detector for power storage element, deterioration state detection method and power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deterioration state detector capable of highly accurately detecting a deterioration state of a power storage element such as a lithium ion secondary battery.SOLUTION: A deterioration state detector 100 for detecting the deterioration state of a power storage element 200 includes: an acquisition unit 110 that defines, as a first capacity change amount, a degree of change in electric conduction amount relative to a voltage of the power storage element 200 when the power storage element 200 is charged or discharged, and acquires a second capacity change amount which is the degree of change in electric conduction amount relative to the first capacity change amount; and a detection unit 120 that detects a deterioration state of the power storage element 200 by comparing the second capacity change amount thus acquired and a predetermined threshold.

Description

  The present invention relates to a deterioration state detection device that detects a deterioration state of a power storage element, a deterioration state detection method, and a power storage system including a power storage element and a deterioration state detection device.

  Power storage elements such as lithium ion secondary batteries have been used as power sources for mobile devices such as notebook computers and mobile phones, but have recently been used in a wide range of fields such as power sources for electric vehicles. In particular, when the power storage element is used as a power source for an electric vehicle, long-term life performance is required. In addition, such a storage element is expected to be used as a power source for load leveling (power load leveling) after being used as a power source for an electric vehicle.

  For this reason, it is important to grasp the lifetime of the power storage element, and conventionally, a technique for detecting the deterioration state of the power storage element has been proposed (see, for example, Patent Document 1). In this technique, a change in voltage when a battery is discharged at a constant power value is acquired, and the deterioration state of the battery is determined by comparing the voltage value with a threshold value.

JP 2010-060408 A

  However, the above-described conventional technique has a problem that the deterioration state of the power storage element cannot be detected with high accuracy.

  That is, in particular, in lithium ion secondary batteries used in hybrid vehicles and electric vehicle applications, the battery capacity deteriorates abruptly, such as a sudden drop in battery capacity at the end of the life, but the technique disclosed in Patent Document 1 It is difficult to detect rapid deterioration with high accuracy.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a deterioration state detection device, a deterioration state detection method, and a power storage system that can accurately detect the deterioration state of a power storage element. .

  In order to achieve the above object, a storage element deterioration state detection device according to an aspect of the present invention is a deterioration state detection device that detects a deterioration state of a storage element, wherein the storage element is charged or discharged. An acquisition unit that obtains a second capacity change amount that is a magnitude of a change in the current-carrying capacity with respect to the first capacity change amount, with a magnitude of a change in the current-carrying capacity with respect to the voltage of the storage element as a first capacity change amount; A detector that detects a deterioration state of the power storage element by comparing the acquired second capacitance change amount with a predetermined threshold value;

  According to this, the deterioration state detection device sets the second capacity change amount, which is the magnitude of the change in the energization capacity with respect to the first capacity change amount, which is the magnitude of the change in the energization capacity with respect to the voltage of the storage element, as the predetermined threshold value. In comparison, the deterioration state of the power storage element is detected. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the deterioration state of the power storage element can be detected with high accuracy by comparing the magnitude of the second capacity change amount with a threshold value. For this reason, according to the degradation state detection device, it is possible to accurately detect the degradation state of the power storage element.

  The acquisition unit includes: a charge / discharge control unit that charges or discharges the power storage element with a constant current for a predetermined period; and an energization period of the power storage element when the charge / discharge control unit charges or discharges the power storage element. Using the charge / discharge information acquisition unit that acquires the voltage during the energization period and the acquired energization period and the voltage, the capacity change amount that calculates the second capacity change amount when the fixed period has elapsed You may decide to provide a calculation part.

  According to this, the deterioration state detection device charges or discharges the storage element with a constant current for a certain period, obtains the energization period and the voltage, and uses the energization period and the voltage, at the time when the certain period has elapsed. The second capacity change amount is calculated. Thus, the deterioration state detection device can easily calculate the second capacity change amount and accurately detect the deterioration state of the power storage element.

  The charge / discharge control unit may charge or discharge the power storage element with the period of 60 seconds or less as the fixed period.

  Here, as a result of intensive studies and experiments, the inventors of the present application have found that the deterioration state of the power storage element can be accurately detected by charging or discharging the power storage element at a constant current for 60 seconds or less. It was. For this reason, according to the said degradation state detection apparatus, the degradation state of an electrical storage element can be detected accurately in a short time, without performing a long-time charge / discharge test during actual use.

  Further, the capacity change amount calculation unit calculates the energization capacity by multiplying the constant current by the energization period, and calculates the first capacity change amount by differentiating the calculated energization capacity with the voltage. The second capacity change amount at the time when the predetermined period has elapsed may be calculated by differentiating the energization capacity with the first capacity change amount.

  According to this, the deterioration state detection device calculates the first capacity change amount by differentiating the energization capacity with the voltage, and calculates the second capacity change amount by differentiating the energization capacity with the first capacity change amount. Thus, the deterioration state detection device can easily calculate the second capacity change amount and accurately detect the deterioration state of the power storage element.

  In addition, when the detection unit determines whether the second capacitance change amount is larger than the threshold value and determines that the second capacitance change amount is larger than the threshold value, the deterioration state of the storage element However, it may be detected that the state is a state immediately before the transition from the first deterioration state where the deterioration is slow to the second deterioration state where the deterioration is abrupt or a state where the deterioration has occurred.

  Here, as a result of intensive studies and experiments, the inventors of the present application transition from a slow deterioration state to a rapid deterioration state when the second capacity change amount is larger than the threshold value. It was found that it was in the state just before or moved. For this reason, the deterioration state detection device can accurately detect that the power storage element has deteriorated rapidly or has deteriorated by comparing the magnitude of the second capacitance change amount with the threshold value.

  In addition, when the detection unit determines whether the second capacity change amount is larger than the threshold value, and determines that the second capacity change amount is larger than the threshold value, the charging upper limit of the power storage element is determined. The voltage may be limited.

  According to this, when it is determined that the second capacity change amount is larger than the threshold, the deterioration state detection device can suppress rapid deterioration of the power storage element by limiting the charging upper limit voltage of the power storage element. Yes, life-long life can be taken.

  In addition, the detection unit determines whether or not the second capacity change amount is larger than the threshold value, and when it is determined that the second capacity change amount is larger than the threshold value, energization of the power storage element is performed. The maximum current may be limited.

  According to this, when it is determined that the second capacity change amount is larger than the threshold, the deterioration state detection device suppresses rapid deterioration of the power storage element by limiting the maximum energization current to the power storage element. Can take measures to prolong life.

  The power storage element is a lithium ion secondary battery including a layered lithium transition metal oxide as a positive electrode active material, and the acquisition unit acquires the second capacity change amount of the lithium ion secondary battery. The detection unit may detect the deterioration state of the lithium ion secondary battery.

  According to this, the electric storage element is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Here, as a result of intensive studies and experiments, the inventors of the present application have found that when the power storage element is the lithium ion secondary battery, the deterioration state of the power storage element can be accurately detected by the above method. For this reason, the deterioration state detection apparatus can accurately detect the deterioration state of the lithium ion secondary battery.

  The present invention can be realized not only as such a storage element deterioration state detection device but also as a storage system including a storage element and a deterioration state detection device that indicates the deterioration state of the storage element. be able to. In addition, the present invention can also be realized as a degradation state detection method in which a characteristic process performed by the degradation state detection apparatus is a step. The present invention can also be realized as an integrated circuit including a characteristic processing unit included in the deterioration state detection apparatus. Further, the present invention is realized as a program for causing a computer to execute characteristic processing included in the degradation state detection method, or a computer-readable CD-ROM (Compact Disc-Read Only Memory) on which the program is recorded. It can also be realized as a recording medium. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  According to the present invention, in a power storage element such as a lithium ion secondary battery, it is possible to accurately detect the deterioration state of the power storage element.

It is an external view of an electrical storage system provided with the degradation state detection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the functional structure of the degradation state detection apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the data for a detection of the memory | storage part which concerns on embodiment of this invention. It is a flowchart which shows an example of the process in which the degradation state detection apparatus which concerns on embodiment of this invention detects the degradation state of an electrical storage element. It is a flowchart which shows an example of the process in which the acquisition part which concerns on embodiment of this invention acquires 2nd capacity | capacitance change amount. It is a flowchart which shows an example of the process which the detection part which concerns on embodiment of this invention detects the deterioration state of an electrical storage element. It is a figure for demonstrating the process in which the detection part which concerns on embodiment of this invention detects the deterioration state of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the state immediately before rapid degradation of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the state immediately before rapid degradation of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the state immediately before rapid degradation of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the state immediately before rapid degradation of an electrical storage element. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the rapid degradation state of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the rapid degradation state of an electrical storage element. It is a figure for demonstrating that the degradation state detection apparatus which concerns on embodiment of this invention can detect the rapid degradation state of an electrical storage element. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a figure for demonstrating that it is preferable that the acquisition part which concerns on embodiment of this invention is charged or discharged for a fixed period of 60 seconds or less, and acquires 2nd capacity | capacitance change amount. It is a block diagram which shows the structure which implement | achieves the degradation state detection apparatus which concerns on embodiment of this invention with an integrated circuit.

  Hereinafter, a deterioration state detection device according to an embodiment of the present invention and a power storage system including the deterioration state detection device will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment.

  First, the configuration of the power storage system 10 will be described.

  FIG. 1 is an external view of a power storage system 10 including a deterioration state detection device 100 according to an embodiment of the present invention.

  As shown in the figure, the power storage system 10 includes a deterioration state detection device 100, a plurality (six in the figure) of power storage elements 200, and a storage case 300 that stores the deterioration state detection device 100 and the plurality of power storage elements 200. And.

  Degradation state detection apparatus 100 is a circuit board on which a circuit that is disposed above a plurality of power storage elements 200 and detects a deterioration state of the plurality of power storage elements 200 is mounted. Specifically, the deterioration state detection apparatus 100 is connected to the plurality of power storage elements 200, acquires information from the plurality of power storage elements 200, and detects the deterioration state of the plurality of power storage elements 200.

  Here, although degradation state detection device 100 is arranged above a plurality of electrical storage elements 200, degradation state detection device 100 may be arranged anywhere. The detailed functional configuration of the deterioration state detection apparatus 100 will be described later.

  The storage element 200 is a secondary battery such as a nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode. In FIG. 6, six rectangular storage elements 200 are arranged in series to form an assembled battery. Note that the number of power storage elements 200 is not limited to six, but may be other plural numbers or one. Further, the shape of the electricity storage element 200 is not particularly limited.

  The power storage element 200 includes a positive electrode in which a positive electrode active material layer is formed on a long strip-like positive electrode base foil made of aluminum or an aluminum alloy, and a long strip-like negative electrode base foil made of copper or a copper alloy. A negative electrode on which a negative electrode active material layer is formed. Here, the positive electrode active material used for the positive electrode active material layer or the negative electrode active material used for the negative electrode active material layer may be a known material as long as it is a positive electrode active material or a negative electrode active material capable of occluding and releasing lithium ions. Can be used.

Here, the power storage element 200 is preferably a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Specifically, Li _{1 + x} M _1-y O ₂ (M is selected from Fe, Ni, Mn, Co, etc.) such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material. It is preferable to use a lithium transition metal oxide having a layer structure such as a seed or two or more transition metal elements, 0 ≦ x <1/3, 0 ≦ y <1/3). Note that as the positive electrode active material, spinel type lithium manganese oxide such as LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ , olivine type positive electrode active material such as LiFePO ₄ , and lithium having the above layered structure You may mix and use a transition metal oxide.

Examples of the negative electrode active material include lithium metal, lithium alloy (lithium metal such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloy). Alloys), alloys capable of inserting and extracting lithium, carbon materials (eg, graphite, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), silicon oxide, metal oxide, lithium metal oxides _{(Li 4} Ti _{6 O 12,} etc.), and the like polyphosphoric acid compound.

  Next, a detailed functional configuration of the deterioration state detection apparatus 100 will be described.

  FIG. 2 is a block diagram showing a functional configuration of degradation state detection apparatus 100 according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of the detection data 151 in the storage unit 150 according to the embodiment of the present invention.

  The deterioration state detection device 100 is a device that detects the deterioration state of the power storage element 200. Specifically, deterioration state detection apparatus 100 detects that the deterioration state of power storage element 200 is in a state immediately before or has shifted from a state in which deterioration is gradual to a state in which deterioration is abrupt. As illustrated in FIG. 2, the degradation state detection apparatus 100 includes an acquisition unit 110, a detection unit 120, and a storage unit 150. In addition, the storage unit 150 stores detection data 151 for detecting the deterioration state of the power storage element 200.

  The acquisition unit 110 acquires the second capacity change amount. Here, when the magnitude of the change in the energization capacity with respect to the voltage of the power storage element 200 when the power storage element 200 is charged or discharged is defined as the first capacity change amount, the second capacity change amount is the first capacity change amount. It is the magnitude of the change of the current carrying capacity with respect to. Detailed description of the first capacity change amount and the second capacity change amount will be described later. The acquisition unit 110 includes a charge / discharge control unit 111, a charge / discharge information acquisition unit 112, and a capacity change amount calculation unit 113.

  The charge / discharge control unit 111 charges or discharges the storage element 200 with a constant current for a fixed period. That is, the charge / discharge control unit 111 instructs the power storage element 200 to charge or discharge for a predetermined time with a constant current, and the power storage element 200 performs charging or discharging according to the instruction. Specifically, the charge / discharge control unit 111 preferably charges or discharges the power storage element 200 with a period of 60 seconds or less as a certain period.

  The constant current (energization current) and the constant period are previously written and stored in the detection data 151 of the storage unit 150 as shown in FIG. Then, the charge / discharge control unit 111 reads the constant current and the constant period from the detection data 151 and charges or discharges the power storage element 200. Note that the charge / discharge control unit 111 may calculate the values of the constant current and the constant period based on a predetermined calculation formula, and charge or discharge the power storage element 200.

  The charge / discharge information acquisition unit 112 acquires the energization period of the power storage element 200 and the voltage during the current supply period when the charge / discharge control unit 111 charges or discharges the power storage element 200. That is, the charging / discharging information acquisition unit 112 measures the voltage of the power storage element 200 for each energization period until the predetermined period elapses, and acquires the energization period and the measured voltage. The energization period is a period that increases at a time interval such as 1 second or 0.1 second, for example, and may be arbitrarily determined by the user, or the charge / discharge information acquisition unit 112 may be based on a predetermined calculation formula. May be calculated. Then, as shown in FIG. 3, the charge / discharge information acquisition unit 112 writes and stores the energization period and voltage in the detection data 151.

  The capacity change amount calculation unit 113 uses the energization period and voltage acquired by the charge / discharge information acquisition unit 112 to calculate the second capacity change amount at the elapse of a certain period. Specifically, the capacity change amount calculation unit 113 reads the constant current and the energization period from the detection data 151, and calculates the energization capacity by multiplying the constant current by the energization period.

  And the capacity | capacitance change calculation part 113 calculates a 1st capacity | capacitance change amount by differentiating the calculated electricity supply capacity with a voltage. Specifically, the capacity change amount calculation unit 113 reads the voltage from the detection data 151 and calculates the first capacity change amount from the relationship between the energization capacity and the voltage.

  And the capacity | capacitance change amount calculation part 113 calculates the 2nd capacity | capacitance change amount at the time of fixed period progress by differentiating an energization capacity | capacitance with a 1st capacity | capacitance change amount. That is, the capacity change amount calculation unit 113 calculates the second capacity change amount at a certain period of time from the relationship between the energization capacity and the first capacity change amount.

  The detection unit 120 detects the deterioration state of the power storage element 200 by comparing the second capacitance change amount acquired by the acquisition unit 110 with a predetermined threshold value. Here, the threshold is written and stored in advance in the detection data 151 of the storage unit 150, as shown in FIG. Then, the detection unit 120 reads out the threshold value from the detection data 151 and compares the second capacitance change amount with the threshold value to detect the deterioration state of the power storage element 200. Note that the detection unit 120 may calculate the threshold value based on a predetermined calculation formula and detect the deterioration state of the power storage element 200. In addition, the detection unit 120 may acquire the threshold value from another device, or the threshold value may be incorporated in the detection unit 120 by a program, a circuit configuration, or the like.

  Specifically, the detection unit 120 determines whether or not the second capacity change amount is larger than a threshold value. When the detection unit 120 determines that the second capacity change amount is larger than the threshold, the deterioration state of the power storage element 200 shifts from the first deterioration state where the deterioration is gradual to the second deterioration state where the deterioration is abrupt. It is detected that it is in the state immediately before the transition or the state has been shifted. Detailed description of the first deterioration state and the second deterioration state will be described later.

  Moreover, the detection part 120 restrict | limits the charge upper limit voltage of the electrical storage element 200, when it is judged that the 2nd capacity | capacitance change amount is larger than a threshold value. That is, in this case, the detection unit 120 issues a signal that limits the upper limit charging voltage of the power storage element 200 and stops charging the power storage element 200 before the power storage element 200 is fully charged.

  In addition, when the detection unit 120 determines that the second capacity change amount is larger than the threshold value, the detection unit 120 may limit the maximum energization current to the power storage element 200. That is, in this case, the detection unit 120 issues a signal that limits the maximum energization current to the power storage element 200 to suppress an excessive value of the current flowing through the power storage element 200.

  The detection unit 120 may issue a warning before or instead of limiting the charging upper limit voltage and the maximum energization current, and determines that the second capacity change amount is larger than the threshold value. In such a case, charging of the power storage element 200 may be stopped.

  Note that the degradation state detection device 100 does not include the storage unit 150, stores the data included in the detection data 151 in the memory of another device, and reads the data from the other device, thereby storing the storage element. 200 degradation states may be detected.

  Next, the process in which the deterioration state detection apparatus 100 detects the deterioration state of the electrical storage element 200 will be described.

  FIG. 4 is a flowchart illustrating an example of processing in which the deterioration state detection apparatus 100 according to the embodiment of the present invention detects the deterioration state of the power storage element 200.

  As shown in the figure, first, the acquisition unit 110 acquires a second capacity change amount (S102). That is, the acquisition unit 110 acquires the second capacity change amount that is the magnitude of the change in the energization capacity with respect to the first capacity change quantity that is the magnitude of the change in the energization capacity with respect to the voltage of the power storage element 200. A detailed description of the process in which the acquisition unit 110 acquires the second capacity change amount will be described later.

  Next, the detection unit 120 detects the deterioration state of the power storage element 200 by comparing the second capacity change amount acquired by the acquisition unit 110 with a predetermined threshold (S104). A detailed description of the process in which the detection unit 120 detects the deterioration state of the power storage element 200 will be described later.

  Thus, the process of detecting the deterioration state of the storage element 200 by the deterioration state detection device 100 ends.

  Next, the process in which the acquisition unit 110 acquires the second capacity change amount (S102 in FIG. 4) will be described in detail.

  FIG. 5 is a flowchart illustrating an example of processing in which the acquisition unit 110 according to the embodiment of the present invention acquires the second capacity change amount.

  As shown in the figure, first, the charge / discharge control unit 111 charges or discharges the storage element 200 with a constant current for a fixed period (S202). Specifically, the charge / discharge control unit 111 charges or discharges the power storage element 200 with a period of 60 seconds or less as a certain period. For example, the charge / discharge control unit 111 charges or discharges the storage element 200 with a constant current of 1 CmA for 24 seconds.

  Note that the charge / discharge control unit 111 charges or stores the storage element 200 for a certain period from the state where the storage element 200 stops charging / discharging when it is desired to detect the deterioration state of the storage element 200 in accordance with a request from the user. Discharge. For example, the charge / discharge control unit 111 discharges the power storage element 200 when the power storage element 200 is fully charged, or charges the power storage element 200 when the power storage element 200 is completely discharged. Further, the charge / discharge control unit 111 may charge or discharge when the power storage element 200 is not fully charged or completely discharged.

  Then, the charge / discharge information acquisition unit 112 acquires the energization period of the power storage element 200 and the voltage in the energization period when the charge / discharge control unit 111 charges or discharges the power storage element 200 (S204). Specifically, the charge / discharge information acquisition unit 112 charges or discharges the power storage element 200 with a constant current I, acquires the voltage V (t) in the energization period t until the predetermined period T, The voltage V (t) is written in the detection data 151.

  Then, the capacity change amount calculation unit 113 calculates the energization capacity by multiplying the constant current by the energization period (S206). That is, the capacity change amount calculation unit 113 reads the constant current I and the energization period t from the detection data 151 and calculates the energization capacity Q (t) in the energization period t using the following equation 1.

      Q (t) = I × t (Formula 1)

  Then, the capacity change amount calculation unit 113 calculates the first capacity change amount by differentiating the calculated energization capacity with the voltage (S208). That is, the capacity change amount calculation unit 113 reads the voltage V (t) in the energization period t from the detection data 151 and, from the relationship with the energization capacity Q (t) in the energization period t, the energization period is expressed by the following formula 2. A first capacity change amount R (t) at t is calculated.

      R (t) = dQ (t) / dV (t) (Formula 2)

  And the capacity | capacitance change calculation part 113 calculates the 2nd capacity | capacitance change amount at the time of a fixed period of time by differentiating energization capacity | capacitance by 1st capacity | capacitance change amount (S210). That is, the capacity change amount calculation unit 113 calculates the second capacity change amount S in the energization period t from the relationship between the energization capacity Q (t) and the first capacity change amount R (t) in the energization period t according to the following Equation 3. (T) is calculated.

S (t) = dQ (t) / dR (t)
= DQ (t) / d (dQ (t) / dV (t)) (Formula 3)

  Then, the capacity change amount calculation unit 113 calculates the second capacity change amount S (T) at the time of the fixed period T by substituting the fixed period T for the energization period t.

  Thus, the process of acquiring the second capacity change amount by the acquisition unit 110 (S102 in FIG. 4) ends.

  Next, a process (S104 in FIG. 4) in which the detection unit 120 detects the deterioration state of the power storage element 200 will be described in detail.

  FIG. 6 is a flowchart illustrating an example of processing in which the detection unit 120 according to the embodiment of the present invention detects the deterioration state of the power storage element 200. FIG. 7 is a diagram for explaining processing in which the detection unit 120 according to the embodiment of the present invention detects the deterioration state of the power storage element 200.

  As shown in the figure, first, the detection unit 120 determines whether or not the second capacity change amount is larger than a threshold value (S302).

  When the detection unit 120 determines that the second capacity change amount is greater than the threshold (Yes in S302), the detection unit 120 immediately before the deterioration state of the power storage element 200 shifts from the first deterioration state to the second deterioration state. It is detected that it is in a state or has been shifted (S304).

  Here, as shown in FIG. 7, the first deterioration state is a state in which the power storage element 200 is gradually deteriorated, and the second deterioration state is a state in which the power storage element 200 is rapidly deteriorated. Further, in the figure, the state immediately before the transition from the first deterioration state to the second deterioration state is shown as a rapid deterioration state P, and the state from the first deterioration state to the second deterioration state is shown as a rapid deterioration state Q. ing. In other words, when the detection unit 120 determines that the second capacity change amount is larger than the threshold value, the detection unit 120 detects that the deterioration state of the power storage element 200 is the state P immediately before the rapid deterioration or the rapid deterioration state Q.

  Then, returning to FIG. 6, the detection unit 120 limits the charging upper limit voltage of the electricity storage element 200 or restricts the maximum energization current to the electricity storage element 200 (S306). That is, when detecting that the deterioration state of the power storage element 200 is the state P immediately before the rapid deterioration or the rapid deterioration state Q, the detection unit 120 performs control so as to suppress the rapid deterioration of the power storage element 200.

  Thus, the process of detecting the deterioration state of the storage element 200 by the detection unit 120 (S104 in FIG. 4) ends.

  Next, the fact that the degradation state detection device 100 can accurately detect the degradation state of the power storage element 200 will be described.

  First, the fact that the deterioration state detection apparatus 100 can detect the state immediately before the rapid deterioration as the deterioration state of the storage element 200 will be described using the test results using the battery system A.

  8 to 10B are diagrams for explaining that the deterioration state detection device 100 according to the embodiment of the present invention can detect the state immediately before the rapid deterioration of the electric storage element 200. Specifically, FIG. 8 is a graph showing a deterioration state of the electricity storage element 200 in the battery system A, and FIG. 9 is a diagram for explaining that the deterioration state detection device 100 can accurately detect the deterioration state of the electricity storage element 200. FIG. 10A and FIG. 10B are diagrams for explaining a conventional method of detecting the deterioration state of the power storage element 200. FIG.

  In the following description, a charge / discharge cycle test that repeats charge / discharge under certain conditions is performed in order to continuously advance the degree of use of the electricity storage element 200, and based on the data acquired thereby, The cycle number in the charge / discharge cycle test is used as an index indicating the degree of use. However, in the actual embodiment, the charge / discharge conditions, particularly the discharge conditions are not constant. Needless to say, it is usually not possible to acquire. Therefore, in the following description, the part “when the number of cycles is XX” is in accordance with “the degree of use of the storage battery 200 when the number of cycles is XX in the charge / discharge cycle test”. Should be interpreted as “when appropriate”.

  First, in FIG. 8, as a specific example, the results of obtaining the reversible capacity of the electricity storage device 200 after performing the following 45 ° C., 1C cycle test in the electricity storage device 200 of the battery system A shown below are shown. Yes.

That is, in the following tests, a lithium ion secondary battery having a positive electrode in which a positive electrode mixture is formed on an aluminum foil and a negative electrode in which a negative electrode mixture is formed on a copper foil as the battery element A of the battery system A Was used. Here, the positive electrode mixture includes a positive electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material. The positive electrode active material is LiNi _1/3 Co _1/3 Mn _1/3. It is a lithium transition metal oxide having a layered structure represented by O ₂ . The negative electrode mixture includes a graphitic carbon material which is a negative electrode active material, and styrene butadiene rubber and carboxymethyl cellulose as a binder.

  In the 45 ° C., 1C cycle test, the charging is 45 ° C., the current is 1 CmA (= 700 mA), the voltage is 4.2 V, and the charging time is 3 hours. The discharging is 45 ° C., the current is 1 CmA ( = 700 mA) and a constant current discharge with a final voltage of 2.85V. In the discharge capacity confirmation test, charging is a constant current and constant voltage charging at 25 ° C., current 1 CmA (= 700 mA), voltage 4.2 V, charging time 3 hours, and discharging is 25 ° C., current 1 CmA (= 700 mA). A constant current discharge with a final voltage of 2.85V was used. In addition, a 10-minute rest period was provided between charging and discharging and between discharging and charging. During the downtime, the battery was in an open circuit state. That is, four steps of charging, resting, discharging, and resting are defined as one cycle.

  From the figure, it can be seen that when the number of cycles is 700 cycles, the state is immediately before the rapid deterioration P1, and when the number of cycles is 900 cycles, the state is the rapid deterioration state Q1.

  FIG. 9 is a graph showing the relationship between the degree of use of the storage element 200 (number of cycles) and the second capacity change amount (dQ / d (dQ / dV)), and the 1C cycle test described above was performed. Later, the result of plotting the second capacity change amount with the above-mentioned fixed period as 24 seconds is shown. That is, the figure is a graph showing the second capacity change amount at 24 seconds after constant current discharge at 25 ° C. and a current of 1 CmA (= 700 mA) after performing the 1C cycle test.

  In addition, although the graph about the case where the electrical storage element 200 was discharged was shown in the figure, the same graph is obtained also when the electrical storage element 200 is charged. For this reason, the acquisition part 110 can acquire the 2nd capacity | capacitance change amount similarly to the case where it discharges also about the case where the electrical storage element 200 is charged. The same applies to the following.

  As shown in FIG. 8, when the number of cycles shown in FIG. 8 is 700 immediately before the rapid deterioration state P1, the second capacity change amount exceeds the threshold A1 (out of the range of the thresholds A1 to B1). ing). In this case, detection unit 120 determines that the second capacity change amount is larger than the threshold, and detects that the deterioration state of power storage element 200 is state P1 immediately before the rapid deterioration when the number of cycles is 700 cycles. Thus, the deterioration state detection apparatus 100 can accurately detect that the power storage element 200 is in the state P1 immediately before the rapid deterioration as the deterioration state of the power storage element 200.

  In the figure, the vertical axis is a negative value. However, since the second capacity change amount and the threshold value are positive values (absolute values), even in the case of FIG. When the number is 700 cycles, it is determined that the second capacity change amount is larger than the threshold value. Note that the threshold is arbitrarily determined for each type of power storage element 200.

  FIG. 10A is a graph showing the relationship between the degree of use (number of cycles) and the battery resistance (impedance) of 1 kHz, and shows a conventional method for estimating deterioration based on an increasing tendency of impedance. As shown in the figure, it is possible to detect that the rapid deterioration state Q1 is reached when the number of cycles is 900 due to the increasing tendency of the impedance. However, when the number of cycles is 700, the storage element 200 rapidly It is difficult to detect the state P1 just before the deterioration.

  FIG. 10B is a graph showing the relationship between the degree of use (number of cycles) and the voltage at the 24th second, and shows a conventional method for estimating deterioration based on a decreasing tendency of the voltage. As shown in the figure, it is possible to detect the rapid deterioration state Q1 when the cycle number is 900 cycles due to the decreasing tendency of the voltage, but when the cycle number is 700 cycles, It is difficult to detect the state P1 just before the deterioration.

  Next, with respect to the battery system A, it will be described that it is preferable to charge or discharge the power storage element 200 for a certain period of 60 seconds or less to obtain the second capacity change amount.

  11A to 11C are diagrams for explaining that the acquisition unit 110 according to the embodiment of the present invention preferably acquires the second capacity change amount by charging or discharging for a certain period of 60 seconds or less. .

  Specifically, FIG. 11A is a graph showing changes in the second capacity change amount at 6 seconds after the start of discharge, and FIG. 11B is a graph showing changes in the second capacity change amount at 12 seconds after the start of discharge. FIG. 11C is a graph showing changes in the second capacity change amount 60 seconds after the start of discharge. In addition, in these figures, although the case where the electrical storage element 200 was discharged is demonstrated, since it is the same also when the electrical storage element 200 is charged as above-mentioned, description is abbreviate | omitted.

  As shown in these figures, when the number of cycles is 700 immediately before the rapid deterioration state P1, the second capacity change amount exceeds the threshold value A2, A3, or A4 (threshold value A2-B2, A3-B3, or A4). Is out of the range of ~ B4). In this case, detection unit 120 determines that the second capacity change amount is larger than the threshold, and detects that the deterioration state of power storage element 200 is state P1 immediately before the rapid deterioration when the number of cycles is 700 cycles. Thus, the deterioration state detection apparatus 100 can accurately detect that the power storage element 200 is in the state P1 immediately before the rapid deterioration as the deterioration state of the power storage element 200.

  As described above, the power storage element 200 is charged or discharged in a fixed period of 60 seconds or less and the second capacity change amount is acquired, thereby accurately detecting that the power storage element 200 is in a state immediately before the rapid deterioration or in a rapid deterioration state. Have been able to. Note that it is considered that the reaction state between the positive and negative electrodes changes after about 60 seconds from the start of charging or discharging, and the reaction state before the passage of 60 seconds becomes the deteriorated state of the storage element 200. Inferred to be deeply related. For this reason, it is thought that the deterioration state of the electrical storage element 200 can be detected with high accuracy by comparing the amount of change in the second capacity before 60 seconds have elapsed after the start of charging or discharging with a threshold value.

  Next, the fact that the deterioration state detection apparatus 100 can detect a sudden deterioration state as the deterioration state of the storage element 200 will be described using a test result using the battery system B. In the following, a test similar to the test performed in FIGS. 8 to 11C is performed using a battery system B of a different type from the battery system A described above.

  12-14 is a figure for demonstrating that the degradation state detection apparatus 100 which concerns on embodiment of this invention can detect the rapid degradation state of the electrical storage element 200. FIG. Specifically, FIG. 12 is a graph showing the deterioration state of the electricity storage element 200, and FIG. 13 is a diagram for explaining that the deterioration state detection device 100 can accurately detect the deterioration state of the electricity storage element 200. FIG. 14 is a diagram for explaining a method for detecting the deterioration state of the conventional power storage element 200.

  First, in FIG. 12, instead of the battery of the battery system A of FIG. 8, the battery system B shown below was used, and after performing the 45 ° C., 1C cycle test shown below, the reversible capacity was obtained. Is shown.

That is, in the following test, a lithium transition metal oxide having a layered structure represented by LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and a spinel-type lithium manganese oxide were used as positive electrode active materials for battery system B. (Mass ratio 7: 3).

  In the 1C cycle test and the discharge capacity confirmation test, charging was constant current constant voltage charging with a current of 1 CmA (= 650 mA), and discharging was constant current discharging with a current of 1 CmA (= 650 mA). The other conditions for the 1C cycle test and the discharge capacity confirmation test are the same as those described with reference to FIG.

  From the figure, it can be seen that when the number of cycles is 300 cycles, the state immediately before the rapid deterioration P2 is obtained, and when the number of cycles is 500 cycles, the sudden deterioration state Q2 is obtained.

  Further, as shown in FIG. 13, when the number of cycles shown in FIG. 12 is the rapid deterioration state Q2 of 500 cycles, the second capacity change amount exceeds the threshold A5 (out of the range of the thresholds A5 to B5). ) In addition, like FIG. 9, after performing said 1C cycle test, FIG. 13 performed the constant current discharge at 25 degreeC and electric current 1CmA (= 650mA), and showed the 2nd capacity | capacitance change amount of 24 seconds. It is a graph.

  In this case, detection unit 120 determines that the second capacity change amount is larger than the threshold, and detects that the deterioration state of power storage element 200 is rapid deterioration state Q2 when the number of cycles is 500 cycles. As described above, the degradation state detection apparatus 100 can accurately detect that the electrical storage element 200 is in the rapid degradation state Q2 as the degradation state of the electrical storage element 200.

  In addition, although the case where the electrical storage element 200 was discharged is demonstrated in the figure, since it is the same also when the electrical storage element 200 is charged as above-mentioned, description is abbreviate | omitted. In addition, the second capacitance change amount and the threshold value are set to positive values (absolute values) as described above.

  Further, as shown in FIG. 14, it is difficult to detect the rapid deterioration state Q2 when the number of cycles is 500 with the conventional method of estimating the deterioration based on the increasing tendency of the impedance. For this reason, in the battery system B, the deterioration state detection device 100 cannot detect the state P2 immediately before the rapid deterioration of the power storage element 200, but can detect the rapid deterioration state Q2 that is difficult to detect by the conventional method.

  Next, with respect to the battery system B, it will be described that it is preferable to charge or discharge the power storage element 200 for a certain period of 60 seconds or less to obtain the second capacity change amount.

  FIGS. 15A to 15C are diagrams for explaining that the acquisition unit 110 according to the embodiment of the present invention preferably acquires the second capacity change amount by charging or discharging for a certain period of 60 seconds or less. .

  Specifically, FIG. 15A is a graph showing changes in the second capacity change amount at 6 seconds after the start of discharge, and FIG. 15B is a graph showing changes in the second capacity change amount at 12 seconds after the start of discharge. FIG. 15C is a graph showing changes in the second capacity change amount 60 seconds after the start of discharge. In addition, in these figures, although the case where the electrical storage element 200 was discharged is demonstrated, since it is the same also when the electrical storage element 200 is charged as above-mentioned, description is abbreviate | omitted.

  As shown in these figures, when the number of cycles is 500, the second capacity change amount exceeds the threshold value A6, A7 or A8 (threshold values A6 to B6, A7 to B7 or A8 to A8). Out of the range of B8). In this case, detection unit 120 determines that the second capacity change amount is larger than the threshold, and detects that the deterioration state of power storage element 200 is rapid deterioration state Q2 when the number of cycles is 500 cycles. As described above, the degradation state detection apparatus 100 can accurately detect that the electrical storage element 200 is in the rapid degradation state Q2 as the degradation state of the electrical storage element 200.

  As described above, the power storage element 200 is charged or discharged in a fixed period of 60 seconds or less and the second capacity change amount is acquired, thereby accurately detecting that the power storage element 200 is in a state immediately before the rapid deterioration or in a rapid deterioration state. Have been able to.

  As described above, according to deterioration state detection apparatus 100 according to the embodiment of the present invention, the magnitude of change in energization capacity with respect to the first capacity change amount, which is the magnitude of change in energization capacity with respect to the voltage of power storage element 200. Is compared with a predetermined threshold value to detect the deterioration state of the electricity storage element 200. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the deterioration state of the storage element 200 can be detected with high accuracy by comparing the magnitude of the second capacitance change amount with a threshold value. . For this reason, according to the deterioration state detection apparatus 100, the deterioration state of the electrical storage element 200 can be detected with high accuracy.

  In addition, the deterioration state detection device 100 charges or discharges the power storage element 200 with a constant current for a certain period, acquires the energization period and the voltage, and uses the energization period and the voltage to generate the The amount of change in two capacities is calculated. As described above, the deterioration state detection device 100 can easily calculate the second capacity change amount and accurately detect the deterioration state of the power storage element 200.

  In addition, as a result of intensive studies and experiments, the inventors of the present application can accurately detect the deterioration state of the storage element 200 by charging or discharging the storage element 200 with a constant current for a fixed period of 60 seconds or less. I found it. For this reason, according to the deterioration state detection apparatus 100, the deterioration state of the electrical storage element 200 can be accurately detected in a short time without performing a long-time charge / discharge test during actual use.

  In addition, the deterioration state detection apparatus 100 calculates the first capacity change amount by differentiating the energization capacity with the voltage, and calculates the second capacity change amount by differentiating the energization capacity with the first capacity change amount. As described above, the deterioration state detection device 100 can easily calculate the second capacity change amount and accurately detect the deterioration state of the power storage element 200.

  Further, as a result of intensive studies and experiments, the inventors of the present application have made the deterioration state of the power storage element 200 shift from a slow deterioration state to a rapid deterioration state when the second capacity change amount is larger than the threshold value. It was found that it was in the state just before or moved. For this reason, the deterioration state detection apparatus 100 can accurately detect whether the power storage element 200 has deteriorated rapidly or has deteriorated by comparing the magnitude of the second capacitance change amount with the threshold value.

  Further, when the deterioration state detection device 100 determines that the second capacity change amount is larger than the threshold value, the deterioration state detection device 100 restricts the charging upper limit voltage of the power storage element 200, thereby suppressing rapid deterioration of the power storage element 200. Yes, life-long life can be taken.

  In addition, when the deterioration state detection device 100 determines that the second capacity change amount is larger than the threshold value, the deterioration state detection device 100 restricts the maximum energization current to the power storage element 200, thereby suppressing the rapid deterioration of the power storage element 200. Can take measures to prolong life.

  The power storage device 200 is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Here, as a result of intensive studies and experiments, the inventors of the present application have found that when the power storage element 200 is the lithium ion secondary battery, the deterioration state of the power storage element 200 can be accurately detected by the above method. For this reason, the deterioration state detection apparatus 100 can detect the deterioration state of the lithium ion secondary battery with high accuracy.

  The power storage system 10 and the deterioration state detection device 100 according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment. That is, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  In addition, the present invention can be realized not only as the power storage system 10 or the deterioration state detection device 100 but also as a deterioration state detection method using a characteristic processing unit included in the deterioration state detection device 100 as a step. Can be realized.

  Each processing unit included in the degradation state detection apparatus 100 according to the present invention may be realized as an LSI (Large Scale Integration) that is an integrated circuit. For example, as shown in FIG. 16, the present invention can be realized as an integrated circuit 160 including an acquisition unit 110 and a detection unit 120. FIG. 16 is a block diagram showing a configuration for realizing the degradation state detection apparatus 100 according to the embodiment of the present invention with an integrated circuit.

  Note that each processing unit included in the integrated circuit 160 may be individually made into one chip, or may be made into one chip so as to include some or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. There is a possibility of adaptation of biotechnology.

  Further, the present invention can be realized as a program for causing a computer to execute characteristic processing included in the degradation state detection method, or a computer-readable non-transitory recording medium in which the program is recorded, for example, a flexible disk, It can also be realized as a hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray Disc (registered trademark)), or semiconductor memory. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a deterioration state detection device that can accurately detect a deterioration state of a power storage element in a power storage element such as a lithium ion secondary battery.

DESCRIPTION OF SYMBOLS 10 Power storage system 100 Degradation state detection apparatus 110 Acquisition part 111 Charging / discharging control part 112 Charging / discharging information acquisition part 113 Capacity change amount calculation part 120 Detection part 150 Storage part 151 Data for detection 160 Integrated circuit 200 Electric power storage element 300 Storage case

Claims (11)

A deterioration state detection device for detecting a deterioration state of a storage element,
The magnitude of the change in energization capacity with respect to the voltage of the electricity storage element when the electricity storage element is charged or discharged is defined as the first capacity change amount, and the second is the magnitude of the change in the energization capacity with respect to the first capacity change amount. An acquisition unit for acquiring a capacity change amount;
A deterioration state detection apparatus comprising: a detection unit that detects a deterioration state of the power storage element by comparing the acquired second capacitance change amount with a predetermined threshold value. The acquisition unit
A charge / discharge control unit that charges or discharges the storage element with a constant current for a fixed period;
A charge / discharge information acquisition unit that acquires an energization period of the power storage element and a voltage in the energization period when the charge / discharge control unit charges or discharges the power storage element;
The deterioration state detection apparatus according to claim 1, further comprising: a capacity change amount calculation unit that calculates the second capacity change amount when the certain period has elapsed using the acquired energization period and the voltage. The deterioration state detection apparatus according to claim 2, wherein the charge / discharge control unit charges or discharges the power storage element with a period of 60 seconds or less as the fixed period. The capacity change amount calculation unit calculates the energization capacity by multiplying the constant current by the energization period, calculates the first capacity change amount by differentiating the calculated energization capacity with the voltage, The deterioration state detection apparatus according to claim 2 or 3, wherein the second capacity change amount at the time when the predetermined period has elapsed is calculated by differentiating an energization capacity with the first capacity change amount. The detector is
Determining whether the second capacity change amount is greater than the threshold;
When it is determined that the second capacity change amount is larger than the threshold value, the deterioration state of the power storage element is a state immediately before the transition from the first deterioration state where the deterioration is gradual to the second deterioration state where the deterioration is abrupt. The deterioration state detection device according to any one of claims 1 to 4, wherein the deterioration state detection device detects that the state is present or has been shifted. The detector is
Determining whether the second capacity change amount is greater than the threshold;
The deterioration state detection device according to any one of claims 1 to 5, wherein when the second capacity change amount is determined to be larger than the threshold value, a charging upper limit voltage of the power storage element is limited. The detector is
Determining whether the second capacity change amount is greater than the threshold;
The degradation state detection apparatus of any one of Claims 1-6 which restrict | limit the energization maximum current to the said electrical storage element, when it is judged that said 2nd capacity | capacitance change amount is larger than the said threshold value. The power storage element is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material,
The acquisition unit acquires the second capacity change amount for the lithium ion secondary battery,
The deterioration state detection device according to claim 1, wherein the detection unit detects the deterioration state of the lithium ion secondary battery. A storage element;
A power storage system comprising: the deterioration state detection device according to any one of claims 1 to 8 that detects a deterioration state of the power storage element. A computer is a deterioration state detection method for detecting a deterioration state of a storage element,
The magnitude of the change in energization capacity with respect to the voltage of the electricity storage element when the electricity storage element is charged or discharged is defined as the first capacity change amount, and the second is the magnitude of the change in the energization capacity with respect to the first capacity change amount. An acquisition step for acquiring a capacity change amount;
A degradation state detection method comprising: a detection step of detecting a degradation state of the power storage element by comparing the acquired second capacitance change amount with a predetermined threshold value. An integrated circuit for detecting a deterioration state of a storage element,
The magnitude of the change in energization capacity with respect to the voltage of the electricity storage element when the electricity storage element is charged or discharged is defined as the first capacity change amount, and the second is the magnitude of the change in the energization capacity with respect to the first capacity change amount. An acquisition unit for acquiring a capacity change amount;
An integrated circuit comprising: a detection unit that detects a deterioration state of the power storage element by comparing the acquired second capacitance change amount with a predetermined threshold value.

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