JP2013092398A - Secondary battery deterioration determination system and deterioration determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately determine capacity deterioration of a secondary battery even when the secondary battery is installed in a vehicle.SOLUTION: A secondary battery deterioration determination system of the present invention comprises: a voltage sensor for detecting a voltage of the secondary battery; a pressure sensor for detecting an internal pressure of the secondary battery; and a control device for calculating capacity deterioration of the secondary battery. The control device calculates capacity deterioration of the secondary battery according to pressure fluctuations between an internal pressure in a predetermined reference state corresponding to a voltage value detected by the voltage sensor and an internal pressure detected by the pressure sensor, by using first relation data of the voltage and the internal pressure of the secondary battery in the predetermined reference state and second relation data of the internal pressure and the battery capacity of the secondary battery.

Description

  The present invention relates to a technique for determining a deterioration state of a secondary battery such as a lithium ion battery.

  Secondary batteries such as lithium ion batteries are deteriorated by repeated charge and discharge. In Patent Document 1, the battery voltage during constant current charging or constant current discharging is sequentially measured to determine the change in battery voltage per predetermined time, and the time during which the change in battery voltage is less than or equal to a predetermined value is calculated as the degree of deterioration. Yes.

  In Patent Document 2, the battery capacity of the secondary battery is detected by using the charge current integrated value when the secondary battery is discharged until the charging rate reaches 0% and then fully charged.

JP 2002-340997 A JP 2008-278624 A

  In Patent Documents 1 and 2, the battery capacity must be detected under specific conditions, such as when the battery capacity is detected during constant current charging or constant current discharging, or when the remaining battery capacity is charged from 0% to a fully charged state. I must. For this reason, it is difficult to determine the deterioration state of the battery capacity in an environment where the battery is mounted and used in a vehicle where charging and discharging are frequently repeated.

  In addition, in order to detect battery capacity deterioration, it is necessary to cause the secondary battery to be charged or discharged under specific conditions. Therefore, charging / discharging for battery capacity deterioration detection causes further battery capacity deterioration. End up.

  The secondary battery deterioration state determination system according to the first aspect of the present invention is a secondary battery deterioration state determination system, a voltage sensor for detecting the voltage of the secondary battery, and a pressure sensor for detecting the internal pressure of the secondary battery. And a control device for calculating the capacity deterioration of the secondary battery. The control device corresponds to the voltage value detected by the voltage sensor using the first relation data of the voltage and internal pressure of the secondary battery and the second relation data of the internal pressure and battery capacity of the secondary battery in a predetermined reference state. The capacity deterioration of the secondary battery is calculated according to the pressure fluctuation between the internal pressure in the predetermined reference state and the internal pressure detected by the pressure sensor.

  According to the first invention of this application, since the capacity deterioration due to the fluctuation of the internal pressure of the secondary battery is calculated, the capacity deterioration of the secondary battery is calculated without causing the secondary battery to operate (experience) under specific conditions. can do. For this reason, it is possible to appropriately determine the capacity deterioration even under the environment in which it is used, and it is possible to determine the capacity deterioration in a shorter time than when the secondary battery is operated under specific conditions, And it can suppress that a secondary battery deteriorates by charging / discharging accompanying deterioration state discrimination | determination. In particular, capacity degradation can be determined even in an environment where the secondary battery is mounted on a vehicle and used (secondary battery in an environment where charging and discharging are repeated frequently).

  The control device calculates a first pressure value in a predetermined reference state corresponding to the voltage value detected by the voltage sensor based on the first relationship data, and calculates the first pressure value based on the second relationship data. A corresponding first battery capacity and a second battery capacity corresponding to the second pressure value detected by the pressure sensor are calculated. From the calculated first battery capacity and second battery capacity, the capacity deterioration of the secondary battery can be calculated.

  The internal pressure of the secondary battery can include the pressure of only the negative electrode element of the battery element constituting the secondary battery or the pressure of each of the negative electrode element and the positive electrode element of the power generation element.

  The control device presets a predetermined reference voltage and a reference internal pressure corresponding to the reference voltage based on the first relation data, and detects the internal pressure at the time of the reference voltage with a pressure sensor, whereby the capacity of the secondary battery is determined. Degradation can be calculated. At this time, the control device can perform control so that the secondary battery is charged and discharged to the reference voltage when the voltage of the secondary battery detected by the voltage sensor is not the reference voltage.

  The pressure sensor can be provided on the outer periphery of the exterior member that covers the battery element constituting the secondary battery or between the battery element and the exterior member, and a lithium ion secondary battery can be used as the secondary battery. .

  A secondary battery deterioration state determination method according to a second invention of the present application is a step of detecting a voltage between terminals of a secondary battery, a step of detecting an internal pressure of the secondary battery, and calculating a capacity deterioration of the secondary battery. Including the steps of: The step of calculating the capacity deterioration of the secondary battery is detected by the voltage sensor using the relational data of the voltage and internal pressure of the secondary battery and the relational data of the internal pressure and battery capacity of the secondary battery in a predetermined reference state. The capacity deterioration of the secondary battery according to the pressure fluctuation between the internal pressure in a predetermined reference state corresponding to the voltage value and the internal pressure detected by the pressure sensor is calculated.

  According to the second invention of the present application, it is possible to appropriately determine the capacity deterioration even under the environment in which the battery is used, and the capacity deterioration can be shortened in a shorter time than when the secondary battery is operated under a specific condition. It can discriminate | determine and it can suppress that a secondary battery deteriorates by the charging / discharging accompanying degradation state discrimination | determination.

It is a schematic block diagram of the battery system mounted in a vehicle. It is a figure which shows an example of the cell provided with the pressure sensor. It is a figure which shows the relationship between the voltage value of a cell, and the internal pressure of a cell. It is a figure which shows the relationship between the internal pressure of a cell, and battery capacity. It is a flowchart which shows the deterioration state discrimination | determination operation | movement of a battery capacity. It is a figure which shows the relationship between the voltage value of a cell, and the internal pressure in consideration of the positive electrode pressure fluctuation of the cell. It is a figure which shows the relationship between the internal pressure in consideration of the positive electrode pressure fluctuation | variation of the cell, and battery capacity.

  Examples of the present invention will be described below.

Example 1
A secondary battery deterioration state determination system that is Embodiment 1 of the present invention will be described. FIG. 1 is a diagram showing the configuration of the battery system of this example.

  The assembled battery 10 includes a plurality of single cells (corresponding to secondary batteries) 11 connected in series. The number of the single cells 11 constituting the assembled battery 10 can be set as appropriate based on the required output. The assembled battery 10 may include a plurality of unit cells 11 connected in parallel.

  The assembled battery 10 of the present embodiment can be mounted on a vehicle. Vehicles include hybrid cars and electric cars. The hybrid vehicle includes an engine or a fuel cell in addition to the assembled battery 10 as a power source for running the vehicle. The electric vehicle includes only the assembled battery 10 as a power source of the vehicle.

  The assembled battery 10 is connected to a load 40. Relay devices (system main relays) 31 and 32 are provided between the assembled battery 10 and the load 40. The relay devices 31 and 32 receive a control signal from the controller 50, and are turned on (connected state) and turned off. The connection / disconnection between the assembled battery 10 and the load 40 is controlled by switching between (blocking states).

  As the load 40, for example, a motor / generator that operates with electric power supplied from the assembled battery 10 can be used. The motor / generator receives electric power from the assembled battery 10 and generates kinetic energy for running the vehicle. The motor generator is connected to the wheels, and the kinetic energy generated by the motor generator is transmitted to the wheels.

  When the vehicle is decelerated or stopped, the motor generator converts kinetic energy generated during braking of the vehicle into electrical energy. The electric power generated by the motor / generator is output to the assembled battery 10. Thereby, regenerative electric power can be stored in the assembled battery 10.

  The load 40 can include a boost converter and an inverter. The boost converter boosts the output voltage of the battery pack 10 and outputs the boosted power to the inverter. The boost converter steps down the output voltage of the inverter and outputs the reduced power to the assembled battery 10. The inverter converts the DC power output from the boost converter into AC power, and outputs the AC power to the motor / generator. The inverter converts AC power output from the motor / generator into DC power and outputs the DC power to the boost converter.

  The voltage monitoring IC 20 (corresponding to a voltage sensor) detects the voltage of each unit cell 11 constituting the assembled battery 10. The voltage monitoring IC 20 is connected to the controller 50 and outputs a detected value of the voltage between the terminals of the unit cell 11 to the controller 50.

  The pressure sensor 21 is provided in each of the plurality of unit cells 11 and detects the internal pressure of the unit cell 11. The pressure sensor 21 is a pressure detection unit that detects the internal pressure of the unit cell 11 by converting the pressure applied to the piezoelectric element, the piezoresistor, and the like into an electric signal. The pressure sensor 21 is connected to the controller 50 and outputs a detection result to the controller 50. The pressure sensor 21 can also be configured to be included in the voltage monitoring IC 20, for example, can be configured as a monitoring IC that detects the voltage and internal pressure of the assembled battery 10.

  FIG. 2 is a diagram illustrating an example of the unit cell 11 provided with the pressure sensor 21. The assembled battery 10 is arranged side by side in a predetermined direction, and can be composed of a plurality of unit cells 11. Two adjacent unit cells 11 are electrically connected by a bus bar (not shown). As shown in FIG. 2A, a partition member 13 made of an insulating material can be provided between two adjacent unit cells 11 arranged side by side in a predetermined direction. The cell 11 (the exterior member 16) and the partition member 13 can be provided. Moreover, the pressure sensor 21 can be provided between a pair of end plates (not shown) disposed at both ends of the assembled battery 10 and the unit cell 11.

  The unit cell 11 includes a power generation element (for example, a positive electrode body, a negative electrode body, a positive electrode body, and a separator (including an electrolytic solution) disposed between the negative electrode bodies can be stacked) 13. It is configured to include. The power generation element 13 (corresponding to a battery element) is covered and sealed with an exterior member 12 (a case member such as an exterior can that houses the power generation element 13). A positive electrode terminal 14 to which the positive electrode body of the power generation element 13 is connected and a negative electrode terminal 15 to be connected to the negative electrode body are provided on the exterior member 12.

The positive active material used for the positive electrode body is a lithium-transition element composite oxide, LiCoO ₂ , LiNiO ₂ , LiMO ₂ (M is at least 2 selected from the group consisting of Co, Ni, Fe, Cu and Mn). Species transition elements), LiMn ₂ O ₄ can be exemplified. Further, the negative active material used for the negative electrode body is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include natural graphite, artificial graphite, coke, an organic fired body, and metal chalcogenide.

Lithium salts used as the electrolyte solute include LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₄ , LiSbF ₆ and LiAsF. There are ₆ etc. The organic solvent used to dissolve the lithium salt is a mixed solvent of cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, and butylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. and so on. In addition, solid electrolyte can be used for electrolyte solution besides a non-aqueous electrolyte, and an inorganic solid electrolyte and a polymer solid electrolyte can be used as a solid electrolyte.

  As shown in FIG. 2B, the pressure sensor 21 can be provided at the outer periphery of the exterior member 12 in which the power generation element 13 is accommodated, for example, at the substantially central portion of the exterior member 12 of the unit cell 11. Further, as shown in FIG. 2C, a pressure sensor 21 can be provided inside the exterior member 12, for example, between the exterior member 12 and the power generation element 13.

  The voltage sensor 21 arranged as in the example of FIG. 2 detects pressure fluctuations of expansion / contraction of the power generation element 13 (active material) accompanying charging / discharging. The plurality of single cells 11 constituting the assembled battery 10 are restrained from both sides in the arrangement direction (stacking direction) with a predetermined restraining force. The voltage sensor 21 detects pressure fluctuations due to expansion (charging) and contraction (discharging) of the power generation element 13 in a state where a certain restraining force is applied to each unit cell 11. When the single battery 11 is used as a secondary battery, the voltage sensor 21 detects pressure fluctuation due to expansion / contraction of the power generation element 13 in a state where no binding force is applied.

  The controller 50 includes a deterioration state determination unit 51 and a storage unit 52 that perform deterioration state determination for determining the deterioration state of the unit cell 11. The voltage monitoring IC 20 (voltage sensor), the pressure sensor 21 and the deterioration state determination unit 51 constitute a deterioration state determination system for the unit cells 11 constituting the battery system.

  The controller 50 can operate as a control device that performs charge / discharge control of the assembled battery 10, and discharge control that outputs the power of the assembled battery 10 to the load 40 based on the vehicle output request, the vehicle decelerates, Charge control is performed to charge the assembled battery 10 with regenerative electric power during vehicle braking when stopping. The deterioration state determination unit 51 can also be configured as a control device separate from the controller 50.

  Next, the deterioration state determination process of the battery cell 11 of the present embodiment will be described in detail. The full charge capacity of the unit cell 11 is deteriorated by repeated charge and discharge and becomes smaller than the full charge capacity in the initial state at the time of manufacture. A lithium ion secondary battery will be described as an example. For example, in the case of overcharge (high rate charge, charge from a high charge state (high SOC), continuous long charge, low temperature charge, etc.), Lithium (Li) metal is sometimes deposited on the negative electrode surface by SEI (Solid Electrolyte interface) film formation, and this deposition of lithium metal is known as a factor causing deterioration of battery capacity.

  That is, in a lithium ion secondary battery, lithium ions move from the positive electrode body (positive active material) to the negative electrode body (negative active material) during charging and are stored, and conversely during discharge, the negative electrode body. Lithium ions return to the positive electrode body, but when lithium (Li) metal is deposited on the electrodes, the lithium ions in the electrolyte responsible for electrical conduction are reduced, and the battery capacity is reduced.

  At this time, the internal pressure of the unit cell 11 changes as the unit cell 11 deteriorates and the lithium ions in the electrolyte responsible for electrical conduction decrease. For example, when the density of lithium ions in the electrolyte decreases, the movement of lithium ions responsible for electrical conduction decreases, so the lithium ions stored in the negative electrode body during charging decrease, and the negative electrode body expands in the initial state. Smaller than the unit cell 11. For this reason, the internal pressure of the power generation element 13 decreases.

  The deterioration state determination of the cell 11 according to the present embodiment is performed by using various data measured in advance as a reference state of the unused cell 11 in an initial state that has not been deteriorated, for example, the cell 11 at the time of manufacture. Based on the voltage value and pressure value detected by the unit cell 11 below, the deterioration state of the battery capacity of the unit cell 11 is calculated and determined.

  In this embodiment, the voltage of the single cell 11 in the initial state is measured by measuring the inter-terminal voltage value (CCV: Closed Circuit Voltage) and the internal pressure value in each of a plurality of different SOC states of the single cell 11 in the initial state. Voltage-SOC relationship data (VS relationship map) indicating the relationship with the SOC, and internal pressure-SOC relationship data (PS relationship map) indicating the relationship between the internal pressure of the unit cell 11 and the SOC in the initial state, and Are previously obtained (created) by measurement.

  Voltage-internal pressure relationship data (VP relationship map) indicating the relationship between the voltage of the unit cell 11 in the initial state and the internal pressure from the two relationship data of the acquired voltage-SOC relationship data and internal pressure-SOC relationship data. : Corresponding to the first relation data). The SOC (State of Charge) indicates the ratio of the current charge capacity to the full charge capacity of the unit cell 11 and can be specified from the OCV (Open Circuit Voltage) of the unit cell 11.

  FIG. 3 is a diagram showing the relationship between the voltage value of the cell 11 and the internal pressure in the initial state. The horizontal axis represents the voltage (V) of the cell 11 and the vertical axis represents the internal pressure of the cell 11. The relationship between the voltage and the internal pressure in the initial state of the cell 11 is represented by a solid line (VP curve). Yes.

  Next, separately from each of the relationship maps described above, the unit cell 11 is deteriorated from the initial state, and the fluctuation of the internal pressure of the unit cell 11 due to the transition of the deterioration state is measured. First, the battery capacity C0 in the initial state can be calculated or measured in advance as an initial value, and the internal pressure P0 of the cell 11 at the battery capacity C0 is measured. Subsequently, the cell 11 in the initial state is charged and discharged to be deteriorated, and the internal pressure P1 of the cell 11 when the battery capacity C1 is reached is measured. The battery capacity C1 can be calculated from the integrated value of the charging current.

  Specifically, the unit cell 11 is deteriorated in a predetermined charging / discharging cycle in which charging and discharging are repeatedly performed up to a preset upper limit SOC, and the battery capacity and internal pressure of the unit cell 11 are acquired in each charging / discharging cycle. For example, when the initial SOC of the unit cell 11 is 80%, the pressure P0 of the unit cell 11 in this initial state is detected by a pressure sensor. The full charge capacity of the unit cell 11 at this time, that is, the battery capacity is the battery capacity C0 before deterioration. Subsequently, the unit cell 11 is discharged to lower the SOC to a certain lower limit value (for example, 20%), and charging is performed from the state where the SOC is the lower limit value until the SOC reaches the same 80%. Charging / discharging with one cycle of discharging and charging up to the same upper limit SOC is repeated, the full charge capacity (Ah) is calculated based on the integrated value of the charging current detected by the current sensor, and the SOC in each charging / discharging cycle The battery capacity and the internal pressure of the unit cell 11 in the state of 80% are measured.

  The pressure of the cell 11 of each battery capacity deteriorated from the battery capacity C0 in the initial state is measured, and the relational data (PC) of the internal pressure and the battery capacity indicating the relationship between the internal pressure of the cell 11 and the battery capacity. Relationship map: corresponding to second relationship data).

  FIG. 4 is a diagram showing the relationship between the internal pressure of the single battery 11 and the battery capacity. The horizontal axis represents the battery capacity (Ah) of the unit cell 11, and the vertical axis represents the internal pressure of the unit cell 11. The solid line represents the relationship between the battery capacity of the unit cell 11 that has been transitioned (deteriorated) by charging and discharging, and the internal pressure of the unit cell 11 at that battery capacity.

  Note that the internal pressure of the cell 11 in the initial state is measured, for example, by measuring the pressure of each of the positive electrode body and the negative electrode body of the power generation element 13 using a battery whose counterpart pole does not change. When the pressure contribution is sufficiently larger than that of the positive electrode body, only the measured pressure fluctuation of the negative electrode body can be used as the internal pressure of the unit cell 11. The example of FIG. 3 and FIG. 4 shows the relationship with the internal pressure including only the pressure fluctuation of the measured negative electrode body.

  In this embodiment, the deterioration state is determined by comparing the relationship between the voltage and internal pressure in the initial state of the cell 11 shown in FIG. 3, and the battery capacity and internal pressure of the cell 11 in each deterioration state shown in FIG. Is stored in the storage unit 52 in advance, and the voltage value and internal pressure of the unit cell 11 are detected by each sensor, thereby degrading the battery capacity of the unit cell 11 in the environment in use. Calculate and determine state.

  FIG. 5 is a flowchart showing the deterioration state determination operation of the cell 11 according to this embodiment. The deterioration state determination is performed by the deterioration state determination unit 51. The deterioration state determination unit 51 uses the detection value detected by the voltage monitoring IC 20 that detects the voltage of the single battery 11 and the detection value detected by the pressure sensor 21 to determine the deterioration state of each single battery 11. Functions as a discrimination device.

  The deterioration state determination unit 51 switches the load 40 after the vehicle ignition switch is switched from OFF to ON, and the relay devices 31 and 32 are turned ON so that the controller 50 can start charge / discharge control (READY-ON state). When charge / discharge control is not performed between the load 40 and the load 40 before the charge / discharge control by the controller 50 ends (READY-OFF state), the charge / discharge control is not performed. The deterioration state of the battery 11 can be determined.

  The deterioration state determination unit 51 acquires the voltage value and pressure value of the unit cell 11 from the voltage monitoring IC 20 and the pressure sensor 21. That is, the actual measurement voltage value V1 and the actual measurement pressure value P1 of the cell 11 in the use environment (use state) connected to the load 40 are acquired from each sensor (S101).

  In step S102, the deterioration state determination unit 51 initializes the pressure value P0 in the initial state corresponding to the actually measured voltage value V1 detected by the voltage monitoring IC 20 from the VP relationship map shown in FIG. Is calculated.

  In step S103, the deterioration state determination unit 51 uses the PC relationship map shown in FIG. 4 stored in the storage unit 52 as the initial state pressure value P0 calculated by the VP relationship map of FIG. A corresponding battery capacity C0 is calculated, and a battery capacity C1 corresponding to the actually measured pressure value P1 detected by the pressure sensor 21 is calculated.

  In step S104, the deterioration state determination unit 51 determines the difference (C0−C1) in the battery capacity corresponding to the pressure fluctuation in which the internal pressure of the battery cell 11 has changed from P0 to P1 with respect to the actually measured voltage value V1. Calculated as the amount of deterioration.

  The calculated deterioration amount can be used as information for determining the deterioration state of the unit cell 11. For example, when the calculated deterioration amount is 0, it can be determined that the cell 11 has not deteriorated from the initial state. When the battery capacity of the single battery 11 is equal to or less than a predetermined value from the calculated deterioration amount, the output limit of the battery pack 10 (for example, the travel distance using the power of the battery pack 10 is limited, or the battery pack 10 is charged / discharged) Current input / output values can be limited). Moreover, the lifetime of the assembled battery 10 can be estimated from the calculated deterioration amount.

  The determination of the deterioration state of the battery capacity of the single battery 11 using the relational data of FIG. 3 and FIG. 4 described above is the deterioration state of the battery capacity due to the fluctuation of the negative electrode body of the single battery 11 due to the deterioration, that is, the negative electrode. The battery capacity degradation state is determined when the body pressure fluctuation is sufficiently larger than the positive electrode body. If the pressure fluctuation of the positive electrode body of the unit cell 11 cannot be ignored, the pressure fluctuation amount of the positive electrode body is calculated. Create the relationship data of the voltage and internal pressure and the relationship data of the battery capacity and the internal pressure corresponding to FIG. 3 (relation data of the voltage and internal pressure) and FIG. 4 (relation data of the battery capacity and internal pressure). Can do.

  FIG. 6 is a diagram illustrating the relationship between the potential of each of the positive electrode body and the negative electrode body of the unit cell 11 and the SOC. The vertical axis represents the potential (V), the horizontal axis represents the SOC (%), and the solid line represents the potential of the positive electrode body and the negative electrode body in the initial state in each SOC.

  First, the relationship between the potential of each of the positive electrode body and the negative electrode body of the unit cell 11 in the initial state and the internal pressure is acquired in the same manner as the example shown in FIG. That is, the relationship data (solid line) between the potential of each of the positive electrode body and the negative electrode body and the SOC shown in FIG. 6 (solid line), and the relationship data between the pressure and SOC of each of the positive electrode body and the negative electrode body (not shown) Are respectively obtained, and the relational data of the internal pressure of the unit cell 11 including the voltage (potential difference between the positive electrode body and the negative electrode body) and the pressure fluctuation of the positive electrode body and the pressure fluctuation of the negative electrode body is created. A VP curve indicated by a two-dot chain line in FIG. 3 is a VP relationship map in which the pressure fluctuation of the positive electrode body is added (added).

  In the example of FIG. 3, the VP relationship map in which the pressure fluctuation of the positive electrode body indicated by the two-dot chain line is taken into consideration is the VP relation map indicated by the solid line considering only the pressure fluctuation of the negative electrode body. The internal pressure slides upward by the amount of pressure fluctuation of the positive electrode body. The internal pressure of the battery cell 11 at an arbitrary voltage V1 is Pa obtained by adding the pressure fluctuation of the positive electrode body to P0.

  Subsequently, a P-C relationship map is created in consideration of the pressure fluctuation of the positive electrode body corresponding to FIG. The cell 11 in the initial state (not deteriorated) of the battery capacity C0 is deteriorated, and each of the positive electrode body and the negative electrode body in an arbitrary SOC (voltage V1) of the cell 11 when the battery capacity C1 is reached. Calculate the potential.

  At this time, by utilizing the property that the amount of charge (discharge amount) of the negative electrode body is smaller than that of the positive electrode body by the amount of deterioration (C0-C1) deteriorated from the battery capacity C0 to the battery capacity C1. A curve indicated by a dotted line 6 can be created in advance. For this reason, the potential of the negative electrode body in a state of being deteriorated to the battery capacity C1 can be calculated from the curve indicated by the dotted line in FIG. As in the example of FIG. 6, the potential of the negative electrode body slides to the right with respect to the potential of the positive electrode body due to deterioration, and the potential increases by the amount of deterioration (the potential difference between the positive electrode body and the negative electrode body). Becomes smaller).

  As described above, the potentials of the positive electrode body and the negative electrode body of the unit cell 11 of each battery capacity deteriorated from the battery capacity C0 in the initial state in an arbitrary SOC are the same as the battery capacity created in advance shown in FIG. It is calculated from the potential fluctuation map of the negative electrode body of the unit cell 11 accompanying the deterioration. When the voltage difference V1 in the initial state of the battery capacity C0 and the potential difference V2 in the state deteriorated to the battery capacity C1 are obtained, the internal pressure of the cell 11 corresponding to each voltage difference V1 and V2 is indicated by a two-dot chain line in FIG. It can be calculated from the indicated VP curve, and the P-C related data can be acquired in consideration of the pressure fluctuation of the positive electrode body.

  FIG. 7 is a diagram showing the relationship between the internal pressure of the unit cell 11 and the battery capacity in consideration of the pressure fluctuation of the positive electrode body. The horizontal axis represents the battery capacity (Ah) of the unit cell 11, and the vertical axis represents the internal pressure of the unit cell 11. The solid line represents the relationship between the battery capacity of the battery cell 11 that has been transitioned (deteriorated) by charging and discharging, and the internal pressure of the battery cell 11 that takes into account the pressure fluctuation of the positive electrode body in that battery capacity.

  In the example of FIG. 7, the relational data indicated by the alternate long and short dash line is the PC relational data when only the pressure fluctuation of the negative electrode body shown in FIG. As shown in FIG. 7, the PC related data in which the pressure fluctuation of the positive electrode body indicated by the solid line is taken into account is the PC related data shown by the one-dot chain line considering only the pressure fluctuation of the negative electrode body. The internal pressure slides upward by the amount of pressure fluctuation of the positive electrode body. Each battery capacity is associated with the internal pressure obtained by adding the pressure fluctuation of the positive electrode body to the pressure fluctuation of the negative electrode body. For example, the internal pressure of the unit cell 11 in the initial state at an arbitrary voltage V1 is P0. The body pressure fluctuation is added to Pa, and the battery capacity C0 in the initial state is associated with the internal pressure Pa. The battery capacity C1 is also associated with Pb added with the pressure fluctuation of the positive electrode body shown in FIG.

  In addition, each relational data shown in FIG.3 and FIG.4, FIG.6 and FIG. 7 is created by applying CCV (Closed Circuit Voltage), and the voltage value of the cell 11 is detected in use environment. The amount of deterioration of the cell 11 is calculated and discriminated based on the CCV of the cell 11 and the internal pressure. However, the present invention is not limited to this, and each relationship data is created by applying OCV (Open Circuit Voltage), and the voltage monitoring IC 20 By calculating the OCV of the single cell 11 using the CCV (Closed Circuit Voltage) of the single cell 11 detected in the use environment acquired by the above, the OCV of the single cell 11 in the use environment and the detected internal pressure May be configured to calculate and determine the deterioration amount of the single battery 11.

  Next, a modified example of the deterioration state determination of this embodiment will be described. For example, an arbitrary voltage (reference voltage) is determined in advance, and the internal pressure of the cell 11 in the initial state corresponding to the arbitrary voltage is acquired in advance from the VP relationship map in the initial state shown in FIG. . The storage unit 52 does not store all the data of the VP relationship map shown in FIG. 3, but stores only an arbitrary voltage and the internal voltage of the cell 11 corresponding thereto. The deterioration state determination unit 51 can be configured to perform deterioration state determination when the voltage of the unit cell 11 detected by the voltage monitoring IC 20 is an arbitrary voltage determined in advance.

  In this case, the deterioration state determination unit 51 detects the internal pressure when the voltage of the unit cell 11 becomes a predetermined arbitrary voltage with the pressure sensor 21, and the internal state in the initial state with respect to the already acquired arbitrary voltage. Using the pressure and the detected internal pressure, the deterioration amount of the unit cell 11 can be calculated from the PC relationship data of FIG. Further, when the voltage of the unit cell 11 detected by the voltage monitoring IC 20 is not a predetermined voltage, the deterioration state determination unit 51 can charge / discharge the unit cell 11 to an arbitrary voltage. The deterioration state determination unit 51 uses the internal pressure detected by the pressure sensor 21 when an arbitrary voltage is reached after charge / discharge control and the internal pressure in the initial state with respect to the already acquired arbitrary voltage, as shown in FIG. The deterioration amount of the unit cell 11 can be calculated from the PC related data.

  In this modification, the processing procedure (for example, step S102 in FIG. 7) is simplified, and all data of the initial state VP relationship map shown in FIG. 3 must be stored in the storage unit 52. Therefore, the storage area of the storage unit 52 can be reduced.

  As described above, the secondary battery deterioration state determination system according to the present embodiment calculates the capacity deterioration due to the fluctuation of the internal pressure of the single battery 11, and thus operates in a specific condition for the single battery 11 to calculate the capacity deterioration. It is possible to calculate the capacity deterioration of the secondary battery without causing it.

  For this reason, it is possible to appropriately determine the capacity deterioration even under the environment in which the battery is used, and to determine the capacity deterioration in a shorter time than when the unit cell 11 is operated under a specific condition. And it can suppress that the cell 11 deteriorates by the charge / discharge accompanying deterioration state determination. In particular, even in an environment where the unit cell 11 is mounted on a vehicle and used (the unit cell 11 in an environment in which charge and discharge are frequently repeated), the unit cell 11 is deteriorated due to charge / discharge accompanying the deterioration state determination. In order to calculate the capacity deterioration, it is possible to appropriately determine the capacity deterioration in a short time without causing the cell 11 to operate under a specific condition.

  It is calculated from the amount of deterioration calculated due to fluctuations in the internal pressure of the cell 11 (expansion / contraction due to charging / discharging of the cell 11) and the integrated value of the charge / discharge current actually detected by the current sensor. The measured deterioration amount is compared, and when there is a difference between the calculated value and the measured value, factors other than the capacity deterioration due to the fluctuation of the internal pressure of the unit cell 11 (for example, the structure change of the positive electrode body) Therefore, it can be determined that the capacity deterioration due to has occurred.

10 battery pack (power supply)
11 Single battery (secondary battery)
12 exterior member 13 power generation element 14 positive electrode terminal 15 negative electrode terminal 16 partition member 20 voltage monitoring IC (voltage sensor)
21 Pressure sensors 31, 32 Relay device 40 Load 50 Controller 51 Degradation state determination unit 52 Storage unit

Claims (7)

A secondary battery degradation state determination system,
A voltage sensor for detecting a voltage of the secondary battery;
A pressure sensor for detecting an internal pressure of the secondary battery;
Corresponding to the voltage value detected by the voltage sensor using first relational data of the voltage and internal pressure of the secondary battery and second relational data of the internal pressure and battery capacity of the secondary battery in a predetermined reference state A control device that calculates capacity deterioration of the secondary battery in accordance with a pressure fluctuation between the internal pressure in the predetermined reference state and the internal pressure detected by the pressure sensor;
A degradation state determination system characterized by comprising:   The control device calculates a first pressure value of the predetermined reference state corresponding to the voltage value detected by the voltage sensor based on the first relation data, and based on the second relation data, A first battery capacity corresponding to the first pressure value and a second battery capacity corresponding to a second pressure value detected by the pressure sensor are calculated, and the capacity is calculated from the first battery capacity and the second battery capacity. The deterioration state determination system according to claim 1, wherein deterioration is calculated.   3. The deterioration state according to claim 1, wherein the internal pressure includes a pressure of only a negative electrode element of a battery element constituting the secondary battery or a pressure of each of a negative electrode element and a positive electrode element of the power generation element. Discriminating system.   The control device presets a predetermined reference voltage and a reference internal pressure corresponding to the reference voltage based on the first relation data, and the voltage of the secondary battery detected by the voltage sensor is the reference voltage. When the voltage is not a voltage, the secondary battery is charged / discharged up to the reference voltage, and the capacity according to the pressure fluctuation between the internal pressure detected by the pressure sensor when the reference voltage is reached and the reference internal pressure The deterioration state determination system according to any one of claims 1 to 3, wherein the deterioration is calculated.   The said pressure sensor is provided in the outer periphery of the exterior member which covers the battery element which comprises the said secondary battery, or between the said battery element and the said exterior member, The any one of Claim 1 to 4 characterized by the above-mentioned. Degradation state determination system described in 1.   The deterioration state determination system according to any one of claims 1 to 5, wherein the secondary battery is a lithium ion secondary battery. A method for determining the deterioration state of a secondary battery,
Detecting a voltage of the secondary battery;
Detecting an internal pressure of the secondary battery;
Using the relationship data between the voltage and internal pressure of the secondary battery and the relationship data between the internal pressure and battery capacity of the secondary battery in a predetermined reference state, the predetermined reference corresponding to the voltage value detected by the voltage sensor Calculating the capacity deterioration of the secondary battery according to the pressure fluctuation between the internal pressure of the state and the internal pressure detected by the pressure sensor;
A degradation state determination method comprising:

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