JP2015153509A - secondary battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a secondary battery system for estimating the degradation of a cell.SOLUTION: A secondary battery system 20 is a system for determining the degradation of a cell 102 which includes an electrode body 70. The secondary battery system 20 comprises: a surface pressure sensor 24 for measuring one of a surface pressure value PC at a central part C of the electrode body 70 and a surface pressure value PL at a left end part L of the electrode body; and an electronic control unit (ECU) 300 which determines the degradation of the cell 102 on the basis of the surface pressure values PC and PL. Based on a pressure of the entire electrode body 70 (a total surface pressure value PT), which is determined by a temperature TB of the cell 102 and a state of charge (SOC) of the cell 102, and the pressure measured by the surface pressure sensor 24, the ECU 300 estimates the other one of the surface pressure values PC and PL. Then, the ECU 300 determines the degradation of the cell 102 by comparing the surface pressure value PC with the surface pressure value PL.

Description

  The present invention relates to a secondary battery system, and more particularly to a secondary battery system for determining cell deterioration.

  Generally, a battery mounted on a hybrid vehicle or an electric vehicle includes a plurality of cells. In these cells, the internal resistance of each cell increases as the electrode body deteriorates. As one of the factors that cause such an increase in internal resistance, high-rate degradation is known. High-rate degradation is a phenomenon that occurs mainly due to uneven salt concentration in the electrolyte, and is likely to occur, for example, when the charge / discharge current is relatively large.

  In high-rate degradation, the pressure in the cell increases as the charge and discharge are repeated, and the cell may expand. In order to determine whether or not high-rate deterioration has occurred, it has been proposed to install a surface pressure sensor in the cell and detect the swelling of the cell. For example, in the battery system disclosed in Japanese Patent Laid-Open No. 2013-122907 (Patent Document 1), an increase in internal resistance is caused based on the surface pressure at the center and the surface pressure at the end of the electrode body in the cell. It is determined whether or not there is.

JP2013-122907A

  In the battery system disclosed in Patent Document 1, both the central surface pressure and the end surface pressure are measured. For this reason, Patent Document 1 describes that a large surface pressure sensor capable of measuring the pressure distribution in the central portion and the entire end portion is installed. However, since the surface pressure sensor is generally expensive, the installation of a large surface pressure sensor increases the cost.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a technique for reducing the cost of a secondary battery system for determining cell deterioration.

  A secondary battery system according to an aspect of the present invention is a system for determining cell deterioration. The cell includes an electrode body having a positive electrode, a negative electrode, and a non-aqueous electrolyte. The secondary battery system is based on the measurement unit that measures one of the first pressure at the center of the electrode body and the second pressure at the end of the electrode body, and the first and second pressures. And a determination unit that determines cell deterioration. The determination unit estimates the other of the first and second pressures from the pressure of the entire electrode body determined from the temperature of the cell and the state of charge of the cell, and the pressure measured by the measurement unit. The deterioration of the cell is determined by comparing the pressure with the second pressure.

  According to the above configuration, the pressure of the entire electrode body is calculated from the cell temperature and the charged state of the cell. For example, when a rectangular flat electrode body is divided into three equal parts, the relationship is established by adding the first pressure at the center and twice the second pressure at the end to obtain the pressure of the entire electrode body. To do. Therefore, when one of the first and second pressures is measured, the other can be estimated from the above relationship. For example, when the first pressure is measured, the second pressure can be estimated from the measured value and the calculated value of the pressure of the entire electrode body. Alternatively, when the second pressure is measured, the first pressure can be estimated from the measured value and the calculated value of the pressure of the entire electrode body. When the cell expands, the first pressure and the second pressure are different. Therefore, it is possible to determine the deterioration by obtaining the pressure difference. According to said structure, since the measurement part for deterioration determination should just be provided only in any one of a center part and an edge part, the size of a measurement part can be made small. Therefore, cost can be reduced.

  Preferably, when the first pressure is higher than the second pressure, the determination unit determines that the cell is deteriorated due to excessive discharge, while the first pressure is higher than the second pressure. If it is smaller, it is determined that the cell has deteriorated due to excessive charging.

  According to the above configuration, by comparing the magnitude relationship between the first and second pressures, it can be determined whether the deterioration of the cell is caused by excessive charging or excessive discharging. Further deterioration of the cell can be suppressed by further executing appropriate processing based on the determination result. For example, when the deterioration of the cell is caused by excessive charging, the charging is suppressed by limiting the charging current to the cell, so that the deterioration of the cell can be suppressed. Alternatively, when the deterioration of the cell is caused by excessive discharge, the discharge is suppressed by limiting the discharge current from the cell, so that the deterioration of the cell can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the cost of the secondary battery system for determining deterioration of a cell can be reduced.

It is a block diagram which shows roughly the structure of the vehicle carrying the secondary battery system which concerns on embodiment of this invention. It is a figure which shows schematically the structure of the battery 10 shown in FIG. FIG. 3 is a perspective view for explaining the configuration of the cell 102 shown in FIG. 2 in more detail. It is a figure which shows the electrode body accommodated in the battery case 50 shown in FIG. It is sectional drawing which follows the VV line of FIG. It is a top view for demonstrating in detail about the plane 78 shown in FIG. It is a figure which shows notionally SOC and surface pressure distribution on the plane 78 in a normal state. It is a figure which shows notionally SOC distribution and pressure distribution in the high-rate degradation state by excessive charge. It is a figure which shows notionally SOC distribution and pressure distribution in the high rate degradation state by excessive discharge. It is a figure which shows an example of the relationship between battery temperature TB, SOC, and the whole surface pressure value PT. It is a flowchart which shows the process for determining high-rate degradation of a cell.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In the present embodiment, the secondary battery system is mounted on a vehicle such as a hybrid vehicle or an electric vehicle. However, the use of the secondary battery system is not limited to vehicles.

  FIG. 1 is a block diagram schematically showing the configuration of a vehicle equipped with a secondary battery system according to an embodiment of the present invention. Referring to FIG. 1, vehicle 1 includes a battery 10, a secondary battery system 20, SMR (System Main Relay) 31 and 32, a converter 41, an inverter 42, a motor generator 43, and drive wheels 44. Is provided. Secondary battery system 20 includes a voltage sensor 21, a current sensor 22, a temperature sensor 23, a surface pressure sensor 24, and an ECU (Electronic Control Unit) 300.

  ECU 300 includes a CPU (Central Processing Unit, not shown), a memory 310, and a buffer (not shown). The ECU 300 controls the devices so that the vehicle 1 is in a desired state based on the signals sent from the sensors and the map and program stored in the memory 310.

  The battery 10 supplies electric power to the motor generator 43. The battery 10 is a rechargeable secondary battery. In the present embodiment, a lithium ion battery is employed as the battery 10.

  The battery 10 is provided with a voltage sensor 21, a current sensor 22, and a temperature sensor 23. The voltage sensor 21 detects the voltage VB of the battery 10. The current sensor 22 detects a current IB input / output to / from the battery 10. The temperature sensor 23 detects the temperature TB of the battery 10. Each sensor outputs the detection result to ECU 300. ECU 300 estimates the state of charge (SOC) of battery 10 based on the detection result of each sensor. In addition, since various well-known methods can be utilized for estimation of SOC, detailed description is not repeated here.

  The battery 10 is further provided with a surface pressure sensor 24 (measurement unit). The surface pressure sensor 24 detects the pressure (surface pressure) on the installation surface and outputs the detection result to the ECU 300. As the surface pressure sensor 24, for example, a sheet-like or film-like tactile sensor can be adopted, but is not limited thereto. The form and installation location of the surface pressure sensor 24 will be described in detail later.

  SMR 31 is provided on a path connecting positive electrode (not shown) of battery 10 and converter 41. SMR 32 is provided in a path connecting negative electrode (not shown) of battery 10 and converter 41. Each of the SMRs 31 and 32 switches conduction / interruption between the battery 10 and the converter 41 under the control of the ECU 300.

  Converter 41 boosts DC power from battery 10 and supplies it to inverter 42. Inverter 42 converts DC power from converter 41 into AC power and supplies it to motor generator 43. The motor generator 43 is a three-phase AC motor generator in which, for example, permanent magnets are embedded in a rotor (both not shown). The motor generator 43 generates a driving force for driving the driving wheels 44 using the AC power from the inverter 42.

  The motor generator 43 can also generate power during regenerative braking. The AC power generated by the motor generator 43 is supplied to the inverter 42. Inverter 42 converts AC power from motor generator 43 into DC power and supplies it to converter 41. Converter 41 steps down DC power from inverter 42 and supplies it to battery 10. Thereby, the battery 10 is charged.

  FIG. 2 schematically shows a configuration of battery 10 shown in FIG. Referring to FIG. 2, battery 10 includes cells 101 to 103 arranged, for example. The arrangement direction of the cells 101 to 103 is determined on the y axis. The height direction of the cells 101 to 103 is determined on the z axis. A direction perpendicular to the y-axis and the z-axis is defined as the x-axis.

  Since the cells 101 to 103 are generally configured to be equal to each other, the cell 102 will be typically described below. The cell 102 is provided with a surface pressure sensor 24 on a surface adjacent to the cell 101.

  In FIG. 2, only three cells are shown, but the number is not particularly limited. Generally, in a battery mounted on a vehicle, more cells (for example, about several tens to 100 cells) are arranged. However, the number of cells may be one.

  FIG. 3 is a perspective view for explaining the configuration of the cell 102 shown in FIG. 2 in more detail. FIG. 4 is a diagram showing an electrode body housed in the battery case 50 shown in FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG.

  3 to 5, the cell 102 has a battery case 50 having a substantially rectangular parallelepiped shape. The upper surface (the upper surface in the z-axis direction) of the battery case 50 is sealed with a lid 52. The lid 52 is provided with a positive terminal 60 and a negative terminal 62 for external connection. One end of each of the positive terminal 60 and the negative terminal 62 protrudes from the lid 52 to the outside. The other end of each of the positive electrode terminal 60 and the negative electrode terminal 62 is electrically connected to the internal positive electrode terminal 64 and the internal negative electrode terminal 66 inside the battery case 50.

  The side surface of the battery case 50 includes a surface 54 and a surface 56. The surface 54 is two side surfaces that face each other in the arrangement direction (y-axis direction) of the cells 101 to 103. The surface 54 has a relatively wide width Wx. On the other hand, the surface 56 is two side surfaces facing each other in the direction (x-axis direction) perpendicular to the arrangement direction and the height direction of the cells 101 to 103. The surface 56 has a relatively narrow width Wy (Wx> Wy). The surface pressure sensor 24 is disposed on the surface 54 of the cell 102 between the cell 102 and another cell adjacent to the cell 102 (cell 101 in FIG. 2).

  An electrode body 70 is accommodated in the battery case 50. The electrode body 70 has a wound body shape in which a positive electrode sheet 72 (positive electrode) and a negative electrode sheet 74 (negative electrode) stacked via a separator 76 are wound in a cylindrical shape. The separator 76 is provided in contact with both a positive electrode active material layer (not shown) provided on the positive electrode sheet 72 and a negative electrode active material layer (not shown) provided on the negative electrode sheet 74. The separator 76 has pores, and the pores are impregnated with an electrolyte (non-aqueous electrolyte). As a result, a conductive path is generated between the positive electrode sheet 72 and the negative electrode sheet 74.

  Further, the electrode body 70 having a wound body shape is crushed. Thereby, a flat surface 78 (shown by a broken line in FIGS. 3 and 4) is formed on the electrode body 70. The electrode body 70 is disposed in the battery case 50 so that the plane 78 is substantially parallel to the surface 54.

  FIG. 6 is a diagram for explaining the plane 78 shown in FIG. 3 in detail. Referring to FIG. 6, the plane 78 has, for example, a rectangular shape when viewed in a plan view from a direction perpendicular to the plane 78 (y-axis direction). Therefore, the plane 78 is line symmetric with respect to the symmetry axis Lz.

  The plane 78 can be virtually divided into an odd number of regions. In the present embodiment, the plane 78 is virtually divided into three regions of a central portion C, a left end portion L, and a right end portion R. Hereinafter, the left end portion L and the right end portion R are also collectively referred to as “end portions”.

  The central portion C is a region sandwiched between the left end portion L and the right end portion R. The symmetry axis Lz passes through the central portion C. The left end portion L and the right end portion R are regions closer to the end portion than the central portion C, and are defined at positions that are line symmetric with respect to the symmetry axis Lz. Therefore, the area of the left end portion L and the area of the right end portion R are equal. As shown in FIGS. 3 and 6, in this embodiment, the area of each region is equal. However, the area of the central portion C may be different from the areas of the left end L and the right end R.

  The surface pressure sensor 24 is installed on the surface 54 of the battery case 50. The installation location of the surface pressure sensor 24 is a location corresponding to any one of the central portion C, the left end portion L, and the right end portion R. In the present embodiment, the surface pressure sensor 24 (indicated by a one-dot chain line in FIG. 3) is installed at a location corresponding to the central portion C.

  Since the plane 78 is disposed substantially parallel to the plane 54, when the electrode body 70 expands in a direction perpendicular to the plane 78 (y-axis direction), the plane 54 also expands in the same direction. Therefore, the pressure distribution on the surface 54 reflects the pressure distribution on the plane 78. Therefore, by installing the surface pressure sensor 24 on the surface 54, the pressure distribution in the central portion C can be acquired. As described above, the surface pressure sensor 24 is provided so as to measure any one of the pressure distributions in the central portion C, the left end portion L, and the right end portion R.

  The method for acquiring the pressure distribution in the central portion C will be described in more detail. The surface pressure sensor 24 includes a plurality of sensor elements (not shown) (not shown) arranged in a matrix. ECU 300 virtually further divides central portion C into strip-shaped regions C1 to Cn along a direction (x-axis direction) from left end L to right end R. And ECU300 adds the measured value from the sensor element in the area | region C1-Cn for every area | region. Thereby, the ECU 300 can acquire a pressure distribution along the x-axis direction of the central portion C.

  In the secondary battery system 20 having the above-described configuration, the cell 102 may deteriorate at a high rate. High-rate degradation is likely to occur when the charge / discharge current is relatively large. If charging is performed frequently with a relatively large charging current or for a long time, high rate deterioration may occur due to excessive charging. On the other hand, if the discharge current is carried out frequently with a relatively large state or for a long time, high-rate deterioration due to excessive discharge can occur.

  As a result of researches by the present inventors, the following phenomenon was found. In the high rate deterioration state, the electric energy stored in the electrode body 70 is uneven (uneven) between the areas of the plane 78. In this specification, the state of charge at a local portion in the electrode body 70 is referred to as “SOC”. The SOC of the region where the amount of power is relatively large is high, while the SOC of the region where the amount of power is relatively small is low. Further, the pressure increases in a region where the SOC is high, while the pressure also decreases in a region where the SOC is low. That is, the SOC distribution and the pressure distribution coincide to a certain extent.

  FIG. 7 is a diagram conceptually showing the SOC distribution and the pressure distribution in a normal state (a state before high-rate deterioration occurs). FIG. 8 is a diagram conceptually showing the SOC distribution and the pressure distribution when high-rate deterioration is caused by excessive charging. FIG. 9 is a diagram conceptually showing the SOC distribution and the pressure distribution when high-rate deterioration is caused by excessive discharge. 7 to 9, the horizontal axis represents a position on the plane 78 along the x-axis direction (see FIG. 6). The vertical axis represents SOC and pressure.

  In the normal state (see FIG. 7), since the SOC of the electrode body 70 does not occur on the plane 78, the SOC is substantially equal between the regions. Therefore, the pressure is also approximately equal between the regions. That is, the SOC distribution and pressure distribution on the plane 78 are flat.

  On the other hand, when high rate deterioration occurs due to excessive charging (see FIG. 8), the SOC of the central portion C is relatively lower than the SOC of the end portions (left end portion L and right end portion R). As a result, the pressure at the center C is lower than the pressure at the end. 8 and 9, the SOC distribution and pressure distribution in the normal state are indicated by broken lines L1 and L2, respectively. When high rate deterioration occurs due to excessive charging, it can be seen that the pressure at the center portion C is reduced while the pressure at the end portion is increased in comparison with the normal state. Furthermore, it can be seen that the average value of the pressure along the x-axis direction when high-rate deterioration has occurred due to excessive charging is substantially equal to the pressure in the normal state.

  On the other hand, when high-rate deterioration has occurred due to excessive discharge (see FIG. 9), the SOC at the center C is relatively higher than the SOC at the ends. As a result, the pressure at the center C is higher than the pressure at the end. Further, in comparison with the normal state, it can be seen that the pressure at the center portion C is increased while the pressure at the end portion is decreased. Furthermore, it can be seen that the average value of the pressure along the x-axis direction when high-rate deterioration is caused by excessive discharge is substantially equal to the pressure in the normal state.

  As described above, when the normal state, the high rate deterioration state due to excessive charge, and the high rate deterioration state due to excessive discharge are compared, the pressure distribution on the plane 78 of the electrode body is different. ECU 300 (determination unit) can determine whether or not high-rate deterioration has occurred in the cell by using this phenomenon. Furthermore, when high-rate deterioration occurs, ECU 300 can determine whether the high-rate deterioration is caused by excessive charge or excessive discharge based on the shape of the pressure distribution.

  Further, the bias of the electric energy in the electrode body does not occur only during charging / discharging of the cell, and is not eliminated immediately after completion of charging / discharging of the cell. Therefore, ECU 300 can determine the deterioration of the cell based on the pressure distribution even after a certain amount of time has elapsed after completion of charging / discharging (for example, after leaving vehicle 1 for a certain amount of time).

  In the present embodiment, as described with reference to FIGS. 3 to 5, the surface pressure sensor 24 has any one of the central portion C, the left end portion L, and the right end portion R (the central portion C in FIG. 3). ) Only. In this case, the pressure in the region where the surface pressure sensor 24 is not installed (the left end portion L and the right end portion R in FIG. 3) can be estimated as follows.

  In the present embodiment, the surface pressure sensor 24 includes a large number of sensor elements. A value obtained by adding the measurement results from all the sensor elements in the central portion C is represented as a surface pressure value PC. Further, assuming that surface pressure sensors having the same configuration as the surface pressure sensor 24 are also installed at the left end L and the right end R, the sum of the measurement results from all the sensor elements in the left end L is calculated as the surface pressure. It is represented as the value PL. The added value of the measurement results from all the sensor elements in the right end R is represented as a surface pressure value PR.

  When the pressure of the entire plane 78 (if a surface pressure sensor is installed on the entire plane 78, the total value of the measurement results from all the sensor elements) is expressed as the entire surface pressure value PT, the entire surface pressure value PT is the surface pressure value PL. , PC, PR. That is, the following formula (1) is established.

PT = PL + PC + PR (1)
As described above, since the left end portion L and the right end portion R are line symmetric, the surface pressure value PL and the surface pressure value PR are equal (PL = PR). Therefore, the following formula (2) is derived from the formula (1).

PL = (PT−PC) / 2 (2)
The electrode body 70 expands and contracts in response to increases or decreases in the temperature TB and SOC of the cell 102. Therefore, the overall pressure value PT in the normal state varies depending on the temperature TB and SOC of the cell 102. The memory 310 of the ECU 300 stores a relationship between the temperature TB, the SOC, and the entire surface pressure value PT of the cell 102 in advance as a map, for example.

  FIG. 10 is a diagram showing an example of a map representing the relationship between the temperature TB and SOC of the cell 102 and the overall pressure value PT. ECU 300 obtains temperature TB of cell 102 from temperature sensor 23 and estimates SOC from voltage VB, current IB and temperature TB of cell 102. ECU 300 then calculates overall pressure value PT from temperature TB and SOC of cell 102 in accordance with the map shown in FIG. However, the calculation method of the overall pressure value PT is not limited to the one using a map, and may be calculated using a predetermined function, for example.

  Thus, the ECU 300 measures the surface pressure value PC using the surface pressure sensor 24. Further, ECU 300 calculates overall pressure value PT in the normal state of cell 102 based on temperature TB of cell 102 and the SOC of entire cell 102. Then, ECU 300 calculates surface pressure value PL (and surface pressure value PR) according to equation (2).

  The surface pressure sensor 24 may be installed at the left end L (or right end R) instead of the central portion C. The following formula (3) is derived from the formula (2). Therefore, when the surface pressure value PL of the left end L is measured, the surface pressure value PC can be estimated based on the entire surface pressure value PT and the surface pressure value PL, as described above.

PC = PT-2 × PL (3)
FIG. 11 is a flowchart showing a process for determining a high rate deterioration of a cell. Referring to FIG. 11, this flowchart is executed when a predetermined condition is established or every elapse of a predetermined period. Each step of this flowchart is basically realized by software processing by ECU 300, but may be realized by hardware processing by an electronic circuit fabricated in ECU 300.

  In step S <b> 10, the ECU 300 measures the surface pressure value PC at the central portion C using the surface pressure sensor 24. ECU 300 obtains temperature TB of cell 102 from temperature sensor 23 and estimates the SOC of cell 102 from voltage VB, current IB and temperature TB of cell 102 (step S20). Further, ECU 300 calculates overall pressure value PT from temperature TB and SOC, for example, according to the map shown in FIG. 10 (step S30). Step S10 and steps S20 and S30 may be interchanged in order of processing.

  In step S40, the ECU 300 calculates the surface pressure value PL according to the equation (2) from the surface pressure value PC measured in step S10 and the entire surface pressure value PT calculated in step S30.

  In step S50, ECU 300 compares the magnitude relationship between surface pressure value PC and surface pressure value PL. If surface pressure value PC is less than surface pressure value PL (PC <PL in step S50), the process proceeds to step S60. In step S60, the ECU 300 determines that high rate deterioration due to excessive charging has occurred in the cell 102 (see FIG. 8). Therefore, ECU 300 limits the charging current to cell 102 (step S65). Thereby, since charging of the cell 102 is suppressed, it is possible to suppress further progress of high-rate deterioration due to excessive charging.

  In contrast, if surface pressure value PC is greater than surface pressure value PL (PC> PL in step S50), the process proceeds to step S70. In step S70, the ECU 300 determines that high rate deterioration due to excessive discharge occurs in the cell 102 (see FIG. 9). Therefore, ECU 300 limits the discharge current from cell 102 (step S75). Thereby, since the discharge of the cell 102 is suppressed, it is possible to suppress further progress of the high rate deterioration due to excessive discharge.

  If surface pressure value PC is equal to surface pressure value PL (PC = PL in step S50), the process proceeds to step S80. In step S80, ECU 300 determines that high rate deterioration has not occurred in cell 102 (see FIG. 7). When any one of steps S65, S75, and S80 is finished, a series of processes shown in FIG. 11 is finished.

  As described above, according to the present embodiment, if the surface pressure sensor is installed in any one of the central portion C, the left end portion L, and the right end portion R, the region where the surface pressure sensor is not installed is also provided. The pressure can be estimated. Therefore, the size (or the number of installations) of the surface pressure sensor can be reduced as compared with the case where the surface pressure sensor is installed on the entire plane. Therefore, cost can be reduced.

  It has been described that each of the surface pressure values PC, PL, PR is an addition value of measured values from all the sensor elements in the corresponding region. However, the surface pressure values PC, PL, and PR are not limited to this as long as the pressure can be compared between the regions. For example, when the area of the central portion C is different from the area of the end portion, each of the surface pressure values PC, PL, PR is an average value or a median value of measured values from the sensor elements in the corresponding region. Preferably there is. The number of sensor elements may be one.

  Furthermore, in the present embodiment, the plane 78 is divided into three regions (see FIG. 3), but the number of divisions of the plane 78 is not limited to this. The number of divisions may be other than 3 as long as it is an odd number. For example, when the plane 78 is virtually divided into five areas, the surface pressure sensor may be installed in at least two of the five areas (however, areas that are not line-symmetric with each other). More specifically, when the regions L2, L1, C, R1, and R2 are expressed in order from the end side, the combination of the region L1 and the region R1 and the combination of the region L2 and the region R2 are excluded. A surface pressure sensor may be installed in one area.

  Further, in FIG. 7, it has been described that the pressure distribution is flat in the normal state of the cell. However, it is conceivable that the pressure distribution is not completely flat even in the normal state. Therefore, the memory 310 of the ECU 300 may store a pressure distribution in an initial state (for example, a state when the battery is manufactured) in advance. By comparing the measured pressure distribution with the pressure distribution in the initial state, the amount of change in the measurement result based on the initial state can be calculated. Thereby, the determination accuracy of high rate degradation can be improved.

  Furthermore, when comparing the magnitude relationship between the surface pressure value PC and the surface pressure value PL, the range of the dead zone may be set in consideration of the measurement error of the surface pressure sensor. For example, when the surface pressure value PC is smaller than the surface pressure value PL by a predetermined value ΔP or more (PC ≦ PL−ΔP), the ECU 300 advances the process to step S60, and the surface pressure value PC is larger than the surface pressure value PL by a predetermined value ΔP. If it is larger (PC ≧ PL + ΔP), the process proceeds to step S70. In this case, when the surface pressure value PC is within a range determined by the predetermined value ΔP of the surface pressure value PL (PL−ΔP <PC <PL + ΔP), the process proceeds to step S80.

  Finally, referring to FIG. 1 again, the present embodiment will be summarized. The secondary battery system 20 is a system for determining deterioration of the cell 102. The cell 102 includes an electrode body 70 having a positive electrode sheet 72, a negative electrode sheet 74, and a non-aqueous electrolyte (not shown). The secondary battery system 20 uses one of the surface pressure value PC at the central portion C of the electrode body 70 and the surface pressure value PL (or surface pressure value PR) at the left end portion L (or right end portion R) of the electrode body. A surface pressure sensor 24 to be measured and an ECU 300 that determines deterioration of the cell 102 based on the surface pressure values PC and PL are provided. The ECU 300 calculates the surface pressure value PC and the surface pressure value PL from the pressure (entire pressure value PT) of the entire electrode body 70 determined from the temperature TB of the cell 102 and the SOC of the cell 102 and the pressure measured by the surface pressure sensor 24. The deterioration of the cell 102 is determined by estimating the other of these and comparing the surface pressure value PC with the surface pressure value PL.

  Preferably, when surface pressure value PC is greater than surface pressure value PL, ECU 300 determines that high rate deterioration has occurred in cell 102 due to excessive discharge, while surface pressure value PC is greater than surface pressure value PL. If it is smaller, it is determined that the high rate deterioration due to excessive charging occurs in the cell 102.

  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.

  DESCRIPTION OF SYMBOLS 1 Vehicle, 10 Secondary battery system, 21 Voltage sensor, 22 Current sensor, 23 Temperature sensor, 24 Surface pressure sensor, 41 Converter, 42 Inverter, 43 Motor generator, 50 Battery case, 58 Lid, 60, Positive terminal, 62 Negative electrode terminal, 64 internal positive terminal, 66 internal negative terminal, 70 electrode body, 72 positive electrode sheet, 74 negative electrode sheet, 76 separator, 78 plane, 80 open end, 100 battery, 101-103 cell, 300 ECU, 310 memory.

Claims (2)

A secondary battery system for determining cell deterioration,
The cell includes an electrode body having a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The secondary battery system includes:
A measuring unit for measuring one of a first pressure at a central portion of the electrode body and a second pressure at an end of the electrode body;
A determination unit that determines deterioration of the cell based on the first and second pressures,
The determination unit estimates the other of the first and second pressures from the pressure of the entire electrode body determined from the temperature of the cell and the state of charge of the cell, and the pressure measured by the measurement unit. A secondary battery system that determines deterioration of the cell by comparing the first pressure and the second pressure. The determination unit
If the first pressure is greater than the second pressure, while determining that the cell has deteriorated due to excessive discharge,
The secondary battery system according to claim 1, wherein when the first pressure is smaller than the second pressure, it is determined that the cell has deteriorated due to excessive charging.

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