JP6809399B2 - Rechargeable battery system - Google Patents

Description

The present disclosure relates to a secondary battery system, and more specifically to a secondary battery system including a lithium ion secondary battery.

Vehicles equipped with a lithium-ion secondary battery as a traveling battery are commercially available. Generally, when a lithium ion secondary battery (hereinafter, also abbreviated as a secondary battery) is charged and discharged with a large current (so-called high-rate charge / discharge), the concentration of the lithium salt in the electrolytic solution (hereinafter, also abbreviated as the salt concentration). It is known that bias can occur. If the salt concentration is biased, the internal resistance of the secondary battery increases, which may reduce the battery performance (charge / discharge performance). Generally, such deterioration is also referred to as "high rate deterioration".

It is known that the higher the temperature of the secondary battery, the more likely the high rate deterioration of the secondary battery to progress. Therefore, in order to calculate an evaluation value indicating the degree of progress of high-rate deterioration, a configuration has been proposed in which the temperature of the secondary battery is detected by a temperature sensor (see, for example, Japanese Patent Application Laid-Open No. 2015-15309 (Patent Document 1)). ..

Japanese Unexamined Patent Publication No. 2015-15309 Japanese Unexamined Patent Publication No. 2013-122907

The parameter that truly affects the progress of high-rate deterioration is the internal temperature of the secondary battery (temperature of the electrode body and the electrolyte). However, from the viewpoint of ease of manufacture and maintainability, the temperature sensor is generally provided outside the housing.

On the other hand, in a vehicle equipped with a secondary battery as a traveling battery, a cooling device (cooling fan or the like) for cooling the secondary battery may be provided. The surface temperature of the housing of the secondary battery may be lower than the internal temperature of the secondary battery at the portion of the secondary battery where the cooling air from the cooling device is directly applied. That is, the error between the temperature detected by the temperature sensor and the internal temperature at which detection is desired can be large. As a result, the accuracy of determining the degree of progress of high-rate deterioration may decrease. In this respect, there is room for improvement in the determination accuracy of high rate deterioration in the method using the temperature sensor.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to improve the determination accuracy of high rate deterioration in a secondary battery system including a lithium ion secondary battery.

A secondary battery system according to an aspect of the present disclosure includes a secondary battery, first and second heat flow velocity sensors, and a determination device. The secondary battery has a housing that houses an electrode body impregnated with an electrolytic solution containing lithium ions. The first heat flow velocity sensor is provided in a portion of the housing corresponding to the "communication region" and detects the heat flow velocity in the communication region. The communication region is a region in which the current collector of the electrode body is exposed from the separator and the inside and the outside of the electrode body communicate with each other. The second heat flow velocity sensor is provided in a portion of the housing corresponding to the “non-communication region” and detects the heat flow velocity in the non-communication region. The non-communication region is a region of the electrode body that is covered with a separator so that the inside and the outside of the electrode body do not communicate with each other. The determination device is generated because the concentration distribution of lithium ions is biased inside the electrode body when the difference between the detection value of the first heat flow velocity sensor and the detection value of the second heat flow velocity sensor is equal to or more than the reference value. It is determined that high rate deterioration, which is deterioration, has occurred.

According to the above configuration, heat flow velocity sensors (first and second heat flow velocity sensors) are provided at two locations on the housing. Although details will be described later, when high-rate deterioration occurs, the electrolytic solution flows out from the communication region to the outside of the electrode body and stays in the vicinity of the communication region. Therefore, the heat capacity of the communication region is higher than the heat capacity of the non-communication region where the outflow of the electrolytic solution does not occur. That is, the temperature in the communication region is less likely to rise than the temperature in the non-communication region. Therefore, the heat flow velocity in the communication region (detected value by the first heat flow velocity sensor) is smaller than the heat flow velocity in the non-communication region (detected value by the second heat flow velocity sensor). Therefore, the difference between the value detected by the first heat flow velocity sensor and the value detected by the second heat flow velocity sensor is calculated, and when the difference is equal to or greater than the reference value, the electrolytic solution flows out and stays. Therefore, it can be determined that the high rate deterioration has occurred.

In this way, unlike the method using a temperature sensor such as a thermoelectric pair, the method using a heat flow velocity sensor detects the heat flow velocity (heat inflow and outflow) inside the secondary battery, so that it is different from the inside of the housing. It is not easily affected by the temperature difference with the outside. Therefore, it is possible to determine the high rate deterioration with high accuracy.

According to the present disclosure, in a secondary battery system including a lithium ion secondary battery, it is possible to improve the determination accuracy of high rate deterioration.

It is a figure which shows schematic the whole structure of the vehicle which mounted the secondary battery system which concerns on this Embodiment. It is a figure for demonstrating the configuration of a cell and a monitoring unit in more detail. It is a figure for demonstrating the change of the heat flow velocity before and after the high rate deterioration. It is a figure for demonstrating an example of the determination result of the deterioration state of the battery in this embodiment. It is a flowchart for demonstrating the determination control of high rate deterioration in this embodiment.

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

In the following, a configuration in which the secondary battery system according to the present embodiment is mounted on a hybrid vehicle will be described as an example. However, the secondary battery system according to the present embodiment is not limited to the hybrid vehicle, but is a set for traveling. It can be applied to all vehicles equipped with batteries (for example, plug-in hybrid vehicles, electric vehicles, fuel cell vehicles). Further, the application of the secondary battery system according to the present embodiment is not limited to the vehicle, and may be, for example, stationary.

[Embodiment]
<Configuration of secondary battery system>
FIG. 1 is a diagram schematically showing an overall configuration of a vehicle equipped with a secondary battery system according to the present embodiment. With reference to FIG. 1, the vehicle 1 includes a secondary battery system 2, a power control unit (PCU) 40, motor generators 51 and 52, an engine 60, a power dividing device 70, and a drive shaft. It includes 80 and a drive wheel 90. The secondary battery system 2 includes a battery 10, a monitoring unit 20, a cooling device 30, and an electronic control unit (ECU) 100.

The battery 10 includes a plurality of cells 110 (see FIG. 2), each of which is a lithium ion secondary battery. The detailed configuration of each cell 110 will be described with reference to FIG. The battery 10 stores electric power for driving the motor generators 51 and 52, and supplies electric power to the motor generators 51 and 52 through the PCU 50. Further, the battery 10 is charged by receiving the generated power through the PCU 40 when the motor generators 51 and 52 generate power.

The monitoring unit 20 monitors the state of the battery 10 and outputs the monitoring result to the ECU 100. The detailed configuration of the monitoring unit 20 will be described later.

The cooling device 30 is an air-cooled cooling device including, for example, a cooling fan and a cooling duct (neither shown). The cooling device 30 generates cooling air for cooling the battery 10 (each cell 110).

The PCU 40 executes bidirectional power conversion between the battery 10 and the motor generators 51 and 52 according to the control signal from the ECU 100. The PCU 40 is configured so that the states of the motor generators 51 and 52 can be controlled separately. For example, the motor generator 52 can be put into a power running state while the motor generator 51 is in a regenerative state (power generation state). The PCU 40 includes, for example, two inverters provided corresponding to the motor generators 51 and 52, and a converter (neither shown) that boosts the DC voltage supplied to each inverter to a voltage higher than the output voltage of the battery 10. Consists of.

Each of the motor generators 51 and 52 is an AC rotating electric machine, for example, a three-phase AC synchronous motor in which a permanent magnet is embedded in a rotor. The motor generator 51 is mainly used as a generator driven by the engine 60 via the power dividing device 70. The electric power generated by the motor generator 51 is supplied to the motor generator 52 or the battery 10 via the PCU 40.

The motor generator 52 mainly operates as an electric motor and drives the drive wheels 90. The motor generator 52 is driven by receiving at least one of the electric power from the battery 10 and the electric power generated by the motor generator 51, and the driving force of the motor generator 52 is transmitted to the drive shaft 80. On the other hand, when the vehicle is braking or the acceleration is reduced on a downhill slope, the motor generator 52 operates as a generator to generate regenerative power generation. The electric power generated by the motor generator 52 is supplied to the battery 10 via the PCU 40.

The engine 60 is an internal combustion engine that outputs power by converting the combustion energy generated when the air-fuel mixture is burned into the kinetic energy of movers such as pistons and rotors.

The power splitting device 70 includes, for example, a planetary gear mechanism (not shown) having three rotating shafts of a sun gear, a carrier, and a ring gear. The power dividing device 70 divides the power output from the engine 60 into a power for driving the motor generator 51 and a power for driving the drive wheels 90.

The ECU 100 includes a CPU (Central Processing Unit) 100A, a memory (more specifically, a ROM (Read Only Memory) and a RAM (Random Access Memory)) 100B, and an input / output port (shown) for inputting / outputting various signals. ) And is included. The ECU 100 controls the charging / discharging of the battery 10 by controlling the engine 60 and the PCU 40 based on the signals received from each sensor and the programs and maps stored in the memory 100B. Further, the ECU 100 determines the degree of progress of deterioration of the battery 10. This determination method will be described later. The ECU 100 corresponds to the "determination device" according to the present disclosure.

<High rate deterioration>
In the secondary battery system 2 configured as described above, for example, when the battery 10 is continuously charged and discharged with a large current, the salt concentration distribution inside the electrode body is biased, and the inside of each cell 110 It is known that high rate degradation occurs with increased resistance.

The degree of progress of high-rate deterioration can be expressed by various deterioration evaluation values. In order to calculate the deterioration evaluation value, it is conceivable to provide a temperature sensor (thermocouple or the like (not shown)) for detecting the temperature of the cell 110. In that case, the parameter that truly affects the progress of high-rate deterioration is the internal temperature of the cell 110 (the temperature of the electrode body and the electrolytic solution), but from the viewpoint of ease of manufacture and maintainability, the temperature sensor is the cell 110. It will be provided outside the housing (outside the housing).

On the other hand, the surface temperature of the housing of the cell 110 may be lower than the internal temperature of the cell 110 at the portion of the cell 110 where the cooling air from the cooling device 30 is directly applied. That is, the error between the temperature detected by the temperature sensor and the internal temperature at which detection is desired can be large. As a result, the deterioration evaluation value is not calculated accurately, and the accuracy of determining the degree of progress of high-rate deterioration may decrease. In this respect, there is room for improvement in the determination accuracy of high rate deterioration in the method using the temperature sensor.

Therefore, in the present embodiment, instead of the temperature sensor, a configuration is adopted in which the heat flow velocity sensor is installed at at least two places described later in the housing of the cell 110. By installing the heat flow velocity sensor at this position, it becomes possible to estimate the high rate deterioration of the cell 110 with high accuracy as described below.

<Cell configuration>
FIG. 2 is a diagram for explaining the configurations of the cell 110 and the monitoring unit 20 in more detail. In FIG. 2, the cell 110 is shown through the inside thereof. The cell 110 includes a battery case 111, a lid 112, a positive electrode terminal 113, a negative electrode terminal 114, and an electrode body 115 (shown by a broken line).

The battery case 111 has a square shape (substantially rectangular parallelepiped shape). In the following, the long side direction (length direction) of the battery case 111 is the x-axis direction, the short side direction (thickness direction) is the y-axis direction, and the height direction is the z-axis direction. The vertical direction is the negative z-axis direction, and the horizontal direction is the xy plane direction. The battery case 111 corresponds to the "housing" according to the present disclosure.

The lid 112 seals the upper surface (vertical upper surface) of the battery case 111. One end of each of the positive electrode terminal 113 and the negative electrode terminal 114 projects outward from the lid 112. The other ends of the positive electrode terminal 113 and the negative electrode terminal 114 are electrically connected to the internal positive electrode terminal and the internal negative electrode terminal (neither of them is shown) inside the battery case 111, respectively.

The electrode body 115 is formed by laminating a positive electrode 116 and a negative electrode 117 via a separator 118 and winding the laminated body. The electrode body 115 is housed in the battery case 111 so that its winding shaft extends in the long side direction (x-axis direction) of the battery case 111. Therefore, the active material layer is not formed in the electrode body 115, and the regions where the surfaces of the current collectors (positive electrode 116 and the negative electrode 117) are exposed from the separator 118 are located at both ends of the battery case 111 in the long side direction. Hereinafter, this region is also referred to as "exposed region" Rs.

On the other hand, the central region of the electrode body 115 in which the active material layer is formed and covered with the separator 118 and the surface of the current collector is not exposed is also referred to as a “central region” Rc. The exposed region Rs and the central region Rc correspond to the “communication region” and the “non-communication region” according to the present disclosure, respectively. The electrolytic solution is mainly held inside the electrode body 115 (central region Rc and exposed region Rs). Although FIG. 2 shows an example in which the electrode body 115 is a wound type, the electrode body 115 may be a laminated type.

For the positive electrode 116, the negative electrode 117, the separator 118, and the electrolytic solution, conventionally known configurations and materials as the positive electrode, the negative electrode, the separator, and the electrolytic solution of the lithium ion secondary battery can be used, respectively. As an example, a ternary material in which a part of lithium cobalt oxide is replaced with nickel and manganese can be used for the positive electrode. Graphite can be used for the negative electrode. Polyolefin (for example, polyethylene or polypropylene) can be used as the separator. The electrolytic solution is an organic solvent (for example, a mixed solvent of DMC (dimethyl carbonate), EMC (ethyl methyl carbonate) and EC (ethylene carbonate)), a lithium salt (for example, LiPF ₆ ), and an additive (for example, LiBOB (lithium bis)). (oxalate) carbonate) or Li [PF ₂ (C ₂ O ₄ ) ₂ ]).

With reference to FIGS. 1 and 2, the monitoring unit 20 includes a voltage sensor 21 and a current sensor 22. The voltage sensor 21 detects the voltage VB of each cell 110. The current sensor 22 detects the current IB input / output to / from the battery 10. Each sensor outputs the detection result to the ECU 100.

<Heat flow velocity sensor>
In the present embodiment, the monitoring unit 20 further includes heat flow velocity sensors 231 to 233 in addition to the voltage sensor 21 and the current sensor 22. The heat flow velocity sensors 231 to 233 detect the heat flow velocities Q1 to Q3 at the installation location of the battery case 111, respectively. More specifically, each heat flow velocity sensor 231 to 233 includes two heat sensitive elements (thin film thermistors) (not shown). When the thermal conductivity of the material of the battery case 111 is represented by C, the thickness of the installation location of the battery case 111 is represented by d, and the temperature difference between the two heat sensitive elements is represented by ΔT, these parameters and the heat flow velocity Q In the meantime, the relationship of Q = C / d × ΔT is established. Since the thermal conductivity C and the thickness d are known from the measured value or the specification value of the battery case 111, the heat flow velocity Q can be calculated from the detected value of the temperature difference ΔT.

The heat flow velocity sensor 231 is provided on one of the side surfaces in the short side direction facing each other at the bottom of the battery case 111 (the portion below the battery case 111 in the vertical direction). That is, the heat flow velocity sensor 231 is provided in a portion of the electrode body 115 corresponding to the exposed region Rs.

The heat flow velocity sensor 233 is provided at the bottom of the battery case 111 on the other side surface (the side surface facing the side surface on which the heat flow velocity sensor 231 is provided) of the side surfaces in the short side direction facing each other. That is, the heat flow velocity sensor 233 is also provided in the portion of the electrode body 115 corresponding to the exposed region Rs. The thermal flow velocity sensors 231 and 233 correspond to the "first flow velocity sensor" according to the present disclosure.

The heat flow velocity sensor 232 is provided at the bottom of the battery case 111 in the central region of the side surface extending in the long side direction of the battery case 111. That is, the heat flow velocity sensor 232 is provided in a portion of the electrode body 115 corresponding to the central region Rc. The heat flow velocity sensor 232 corresponds to the "second flow velocity sensor" according to the present disclosure.

Hereinafter, the reason for installing the heat flow velocity sensors 231 to 233 in this way will be described. The set of heat flow velocity sensors 231 to 233 may be provided for all the cells 110 included in the battery 10, or for each of a plurality of (for example, several to several tens) cells 110 as a monitoring unit. It may be provided in.

FIG. 3 is a diagram for explaining the change in the heat flow velocity before and after the high rate deterioration. FIG. 3A shows the state of the cell 110 before the high rate deterioration, and FIG. 3B shows the state of the cell 110 after the high rate deterioration.

With reference to FIG. 3A, the heat flow velocity sensors 231 and 233 are provided on the side surface of the battery case 111 in the short side direction. As described with reference to FIG. 2, the exposed region Rs of the electrode body 115 is located on the side surface of the battery case 111 in the short side direction. Therefore, the heat flow velocity sensors 231 and 233 detect the heat flow velocity accompanying the movement of the electrolytic solution in the exposed region Rs.

On the other hand, the heat flow velocity sensor 232 is provided in the central region of the side surface extending in the long side direction of the battery case 111. Therefore, the heat flow velocity sensor 232 detects the heat flow velocity accompanying the movement of the electrolytic solution in the central region Rc of the electrode body 115.

When high-rate deterioration does not occur, the electrolytic solution is mainly held in the electrode body 115, and a surplus electrolytic solution (an electrolytic solution in excess of the amount that can be held by the electrode body 115) is located at the bottom of the battery case 111. Does not exist much. In this case, the heat flow velocity Q2 in the central region Rc of the electrode body 115 and the heat flow velocities Q1 and Q2 in the exposed region Rs are substantially equal (Q1≈Q2≈Q3).

On the other hand, when high-rate deterioration occurs, as shown in FIG. 3B, the electrolytic solution flows out from the exposed region Rs that communicates the inside and the outside of the electrode body 115 to the outside of the electrode body 115, and the battery case. It stays at the bottom of 111. Then, the heat capacity of the region where the electrolytic solution stays (the region near the exposed region Rs) becomes larger than the heat capacity of the central region Rc where the electrolytic solution does not flow out. That is, the temperature of the exposed region Rs is less likely to rise than the temperature of the central region Rc. Therefore, the heat flow velocities Q1 and Q3 (magnitude) in the exposed region Rs are smaller than the heat flow velocities Q2 (magnitude) in the central region Rc. Therefore, the heat flow velocity difference ΔQ, which is the difference between the value detected by the heat flow velocity sensor 232 (Q2) and the value detected by the heat flow velocity sensors 231,233 (Q1, Q3), is calculated, and the heat flow velocity difference ΔQ is a predetermined reference value ΔQref. In the above case, it can be determined that the high rate deterioration has occurred, assuming that the electrolytic solution has flowed out and stayed.

Unlike temperature sensors such as thermocouples, the heat flow velocity sensors 231 to 233 detect the heat flow velocity in the electrode body 115 housed inside the cell 110, so that the external environment (cell 110 by cooling air from the cooling device 30) is detected. It is not easily affected by the temperature difference between the surface temperature and the internal temperature. Therefore, according to the present embodiment, it is possible to determine the high rate deterioration with high accuracy.

FIG. 4 is a diagram for explaining an example of a determination result of a deteriorated state of the battery 10 (or cell 110) in the present embodiment. In FIG. 4, the horizontal axis represents the elapsed time, and the vertical axis represents the rate of increase in the internal resistance (resistance increase rate) of the battery 10 with respect to the initial state.

As shown in FIG. 4, the internal resistance of the battery 10 is roughly classified into wear resistance and resistance increased due to high rate deterioration. The wear resistance is a resistance component that increases as the material (for example, active material, current collector, etc.) constituting the battery 10 wears (wear deteriorates) with the passage of time. As described above, the resistance due to high rate deterioration is a resistance component caused by a bias in the salt concentration distribution inside the electrode body 115. According to the present embodiment, since the high rate deterioration can be determined with high accuracy by using the heat flow velocity sensor, the internal resistance of the battery 10 is obtained with high accuracy by obtaining the wear resistance separately from the resistance due to the high rate deterioration. (See, for example, Japanese Patent Application Laid-Open No. 2013-247054).

<High rate deterioration judgment flow>
FIG. 5 is a flowchart for explaining the determination control of high rate deterioration in the present embodiment. This flowchart is called and executed from the main routine (not shown) when a predetermined condition is satisfied. Each step (hereinafter abbreviated as S) is basically realized by software processing by the ECU 100, but may be realized by hardware processing by an electronic circuit manufactured in the ECU 100.

With reference to FIGS. 1, 2 and 5, in S10, the ECU 100 acquires the heat flow velocities Q1 to Q3 from the heat flow velocity sensors 231 to 233, respectively.

In S20, the ECU 100 calculates the heat flow velocity difference ΔQ in the battery 10. The heat flow velocity difference ΔQ may be the difference between the heat flow velocity Q2 and the heat flow velocity Q1 (Q2-Q1), or may be the difference between the heat flow velocity Q2 and the heat flow velocity Q3 (Q2-Q3). Alternatively, the heat flow velocity difference ΔQ may be the difference ((Q2 + Q3) / 2) −Q1) between the average value of the heat flow velocity Q2 and Q3 and the heat flow velocity Q1.

In S30, the ECU 100 compares the heat flow velocity difference ΔQ calculated in S20 with the predetermined reference value ΔQref. The reference value ΔQref can be experimentally determined according to the surplus amount of the electrolytic solution, the size of the battery case 111, and the like, and can be set to a value of about 10% of the size of the heat flow velocity Q2, for example.

When the heat flow velocity difference ΔQ is equal to or greater than the reference value ΔQref (YES in S30), the ECU 100 determines that the high rate deterioration of the battery 10 is progressing (S40). Then, the ECU 100 executes "high rate deterioration mitigation control" for mitigating the high rate deterioration of the battery 10 (S50). The high rate deterioration mitigation control is, for example, one of the following first to fourth controls. However, the high-rate deterioration mitigation control may be a control in which a plurality of controls among the first to fourth controls are appropriately combined.

The first control is a control that raises both the upper limit value and the lower limit value of the SOC (State Of Charge) of the battery 10. The second control is a control that raises the control center value of the SOC of the battery 10. The third control is a control for raising the temperature of the battery 10 by, for example, stopping the cooling device 30 or suppressing the air volume of the cooling device 30. The fourth control is a control that sets the control upper limit value (Win) of the charge power and the control upper limit value (Wout) of the discharge power of the battery 10 lower than those in the normal time (when the high rate deterioration mitigation control is not executed). Is.

On the other hand, when the heat flow velocity difference ΔQ is less than the reference value ΔQref in S30 (NO in S30), the ECU 100 determines that the high rate deterioration of the battery 10 has not progressed (S60). In this case, the ECU 100 does not execute the high rate deterioration mitigation control (S70). When the control of S50 and S60 is completed, the processing is returned to the main routine.

As described above, according to the present embodiment, the heat flow velocity sensors 231 and 233 are provided in the portion corresponding to the exposed region Rs of the electrode body 115, and the heat flow velocity is provided in the portion corresponding to the central region Rc of the electrode body 115. The sensor 232 is provided. When the high rate deterioration progresses, the detected value of the heat flow velocity sensor 232 does not change much, but the detected value of the heat flow velocity sensor 231 and 233 changes (becomes smaller) due to the outflow and retention of the electrolytic solution. Therefore, by comparing the detected value of the heat flow velocity sensor 232 with the detected value of the heat flow velocity sensors 231 and 233, it is possible to determine whether or not the high rate deterioration is progressing. By using the heat flow velocity sensors 231 to 233, the influence of the external environment such as the temperature difference between the surface temperature and the internal temperature of the cell 110 due to the cooling air from the cooling device 30 can be reduced, so that the determination of high rate deterioration can be determined. The accuracy can be improved.

In the present embodiment, the configuration in which the heat flow velocity sensors 231 and 232 are provided instead of the temperature sensors (not shown) has been described as an example, but the temperature sensor and the heat flow velocity sensors 231,232 may be used in combination. Good.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present disclosure is shown by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

1 vehicle, 2 secondary battery system, 10 battery, 20 monitoring unit, 21 voltage sensor, 22 current sensor, 231 to 233 heat flow sensor, 30 cooling device, 40 PCU, 51, 52 motor generator, 60 engine, 70 power split Device, 80 drive shaft, 90 drive wheel, 100 ECU, 100A CPU, 100B memory, 110 cell, 111 battery case, 112 lid, 113 positive electrode terminal, 114 negative electrode terminal, 115 electrode body, 116 positive electrode, 117 negative electrode, 118 separator ..

Claims (1)

A secondary battery having a housing for accommodating an electrode body impregnated with an electrolytic solution containing lithium ions,
In the housing, the current collector of the electrode body is exposed from the separator and is provided in a portion corresponding to the communication region where the inside and the outside of the electrode body communicate with each other, and the heat flow velocity in the communication region is detected. The first heat flow velocity sensor to be
The housing is provided in a portion of the housing that is covered with the separator and corresponds to a non-communication region in which the inside and the outside of the electrode body are not communicated with each other, and the heat flow velocity in the non-communication region is measured. A second heat flow velocity sensor to detect,
When the difference between the detection value of the first heat flow velocity sensor and the detection value of the second heat flow velocity sensor is equal to or larger than the reference value, the concentration distribution of the lithium ions is biased inside the electrode body. A secondary battery system including a determination device for determining that high-rate deterioration, which is deterioration, has occurred.

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