Short circuit indication detection system and short circuit indication detection method

Abstract

A short circuit indication detection system (1) includes a battery cell (21), a temperature sensor (13) that measures a battery temperature, a resistance measurement unit (101) that measures an electrolyte resistance of a solid electrolyte of the battery cell (21), and a determination unit (104) that determines whether there is an indication of occurrence of a short circuit between a positive electrode and a negative electrode. The determination unit (104) determines that the indication is present when the amount of decrease in the electrolyte resistance measured by the resistance measurement unit (101) during charging is greater than the amount of decrease in the electrolyte resistance caused by a change in the battery temperature by a predetermined value or more.

Description

Technical Field

[0001] This invention relates to a short circuit indication detection system and a short circuit indication detection method. Background Technology

[0002] A known method for detecting the state of a lithium secondary battery includes a discharge step of discharging the battery to 10% or lower SOC, a measurement step of measuring the impedance of the battery discharged by the discharge step, and a state detection step of detecting the battery state based on the impedance measurement obtained in the measurement step (see, for example, Patent Document 1). In the state detection step of this method, a reactive resistance value is calculated based on the impedance measured in the measurement step, and the calculated reactive resistance value is compared with a predetermined threshold to determine whether the battery has degraded due to lithium plating at the negative electrode.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: JP A 2012-212513 Summary of the Invention

[0006] The problem to be solved by the present invention

[0007] However, in the conventional method disclosed in Patent Document 1, the reaction resistance value is compared with a threshold to determine whether lithium plating at the negative electrode has caused battery degradation. Therefore, there may be a problem that short circuits caused by lithium plating are difficult to detect early.

[0008] The present invention addresses this problem by providing a short-circuit indication detection system and a short-circuit indication detection method for early detection of short circuits.

[0009] Problem-solving methods

[0010] The present invention solves the above-mentioned problem by having a short-circuit indication determining device indicate the presence of a short circuit between the positive and negative electrodes when the decrease in electrolyte resistance measured by the resistance measuring device during charging is greater than a predetermined value or more than the decrease in electrolyte resistance caused by changes in battery temperature.

[0011] The effects of the invention

[0012] This invention enables early detection of short circuits. Attached Figure Description

[0013] Figure 1 (a) is a graph showing the values ​​of current and voltage measured in Experiment Example 1, which was used to charge and discharge the battery under conditions unlikely to cause a short circuit.

[0014] Figure 1 (b) is a graph showing the values ​​of current and voltage measured in Experiment Example 2, which was used to charge and discharge the battery under conditions that could cause a short circuit.

[0015] Figure 2 (a) represents the Cole-Cole plot, which shows the situation as follows: Figure 1 The impedance measured during the discharge period in the first cycle indicated by II-a in (a).

[0016] Figure 2 (b) represents the Kol-Kol diagram, which shows the situation as follows: Figure 1 The impedance measured during charging in the first cycle indicated by II-b in (a).

[0017] Figure 3 (a) represents the Cole-Cole diagram, which shows the situation as follows: Figure 2 (b) Impedance measured during discharge in the first cycle indicated by III-a.

[0018] Figure 3 (b) represents the Kol-Kol diagram, which shows the situation as follows: Figure 2 (b) The impedance measured during charging in the first cycle indicated by III-b.

[0019] Figure 3 (c) represents the Kol-Kol diagram, which shows the situation as follows: Figure 2 (b) Impedance measured during discharge in the second cycle indicated by III-c.

[0020] Figure 4 It means as Figure 3 (b) shows a Cole-Cole plot, which uses the imaginary part of the impedance as the vertical axis and the frequency as the horizontal axis.

[0021] Figure 5 This is a block diagram illustrating a short-circuit indication and detection system according to an embodiment of the present invention.

[0022] Figure 6 This is a flowchart illustrating a short-circuit indication detection method according to an embodiment of the present invention.

[0023] Figure 7 This is a graph illustrating an example of the relationship between battery temperature and resistivity.

[0024] Figure 8 (a) is a graph showing an example of the measured and predicted values ​​of the electrolyte resistance during charging.

[0025] Figure 8 (b) is a graph showing an example of battery temperature changes during charging. Detailed Implementation

[0026] [Interfacial resistance of solid electrolytes]

[0027] The inventors investigated a method for detecting short circuits caused by dendrites deposited at the interface between the solid electrolyte and the negative electrode during charging of an all-solid-state battery. Based on experiments calculating the resistance of the solid electrolyte (interface resistance of the solid electrolyte) during charging using high-frequency impedance, the inventors discovered a decreasing trend in resistance before a short circuit occurs.

[0028] Figure 1 (a) is a graph showing the values ​​of current and voltage measured in Experiment Example 1, which was used to charge and discharge the battery under conditions unlikely to cause a short circuit. Figure 2 (a) represents the Kol-Kol diagram (Nyquist diagram), which shows the situation as follows: Figure 1 The impedance measured during the discharge period in the first cycle indicated by II-a in (a). Figure 2 (b) represents the Kol-Kol diagram, which shows the situation as follows: Figure 1 The impedance measured during charging in the first cycle indicated by II-b in (a).

[0029] In Experimental Example 1, experimental battery 1 was fabricated by providing a Li metal layer as the negative electrode on one surface of the solid electrolyte and a Li-In layer as the positive electrode on the other surface. Experimental battery 1 was then subjected to multiple cycles of charge and discharge under conditions unlikely to cause a short circuit between the negative and positive electrodes (conditions unlikely to cause dendrite precipitation at the contact interface between the negative electrode and the solid electrolyte during charging), while measuring the current, voltage, and impedance. Specifically, the current density was set to 0.32 mA / cm². 2 Experimental cell 1 was subjected to multiple cycles of charging and discharging. Impedance was measured multiple times during discharge and charging by EIS (electrochemical impedance spectroscopy).

[0030] like Figure 1 As shown in (a), during the charge-discharge cycle of Experimental Example 1, the voltage of Experimental Battery 1 exhibited a normal value, and no short circuit occurred. At this time, as... Figure 2 (a) shows the impedance during discharge in the first cycle and as shown in the figure. Figure 2 (b) shows that the impedance is almost the same during the first cycle of charging.

[0031] The vertical axis of the Cole-Cole plot indicates the imaginary part of the impedance, and its horizontal axis indicates the real part. It is assumed that the diameter of the leftmost semicircular portion in the figure corresponds to the resistance value of the solid-state electrolyte (SE) (in some cases, referred to as electrolyte resistance hereinafter), the diameter of the rightmost semicircular portion corresponds to the reaction resistance value of the Li-In layer, and the diameter of the semicircular portions between these semicircular portions corresponds to the reaction resistance value of the Li layer. Therefore, for example, the semicircles formed in the Cole-Cole plot allow for the calculation of the electrolyte resistance by fitting an equivalent circuit.

[0032] Figure 1 (b) is a graph showing the values ​​of current and voltage measured in Experiment Example 2, which was used to charge and discharge the battery under conditions that could cause a short circuit. Figure 3 (a) represents the Cole-Cole diagram, which shows the situation as follows: Figure 2 (b) Impedance measured during discharge in the first cycle indicated by III-a. Figure 3 (b) represents the Kol-Kol diagram, which shows the situation as follows: Figure 2 (b) The impedance measured during charging in the first cycle indicated by III-b. Figure 3 (c) represents the Kol-Kol diagram, which shows the situation as follows: Figure 2 (b) Impedance measured during discharge in the second cycle indicated by III-c.

[0033] like Figure 3 As shown in (a), the impedance was measured in the order of C1, C5, C10, C15, C20, and C25 during the first discharge cycle. Figure 3 As shown in (b), the impedance was measured in the order of D1, D5, D10, D15, D20, and D25 during the first charging cycle. Figure 3 As shown in (c), the impedance was measured in the order of 2C1, 2C5, 2C10, 2C15, 2C20 and 2C25 during the discharge in the second cycle.

[0034] In Experimental Example 2, similar to Experimental Example 1, experimental battery 2 was prepared by providing a Li metal layer as the negative electrode on one surface of the solid electrolyte and a Li-In layer as the positive electrode on the other surface. Then, experimental battery 2 was subjected to multiple cycles of charge and discharge under conditions that could cause a short circuit between the negative and positive electrodes, while measuring the current, voltage, and impedance. Specifically, the current density was set to 0.64 mA / cm². 2 The experimental battery 2 was subjected to multiple cycles of charging and discharging.

[0035] like Figure 1As shown in (b), in Experimental Example 2, the voltage of Experimental Battery 2 began to rise during the charging phase of the sixth cycle, and thereafter, as the charge-discharge cycle progressed, the voltage of Experimental Battery 2 gradually approached 0 [V] (short circuit). Figure 2 (a) shows the impedance during discharge in the first cycle and as shown in the figure. Figure 2 (b) shows a comparison of impedances during charging in the first cycle. The impedance during charging reveals a decrease in electrolyte resistance during charging. Figure 2 As shown in (c), the electrolyte resistance returns to its original value during discharge in the second cycle. Although not specifically shown, the electrolyte resistance also recovers to its original value during charging in the second and subsequent cycles, similar to... Figure 2 The impedance shown in (b) decreases similarly.

[0036] Figure 4 It means as Figure 3 (b) shows a Cole-Cole plot, which plots the imaginary part of the impedance on the vertical axis and the frequency on the horizontal axis. Figure 4 As shown, although no specific limitations are imposed, the electrolyte resistance can be calculated based on the impedance of experimental battery 2 relative to an AC signal at a frequency of 10 kHz or higher. In Experimental Example 2, the electrolyte resistance calculated based on the impedance at 10 kHz or higher shows that the imaginary part becomes smaller and smaller over time during charging. In other words, the electrolyte resistance decreases over time during charging. Meanwhile, the resistance values ​​of the Li metal layer and Li-In layer calculated based on impedances below 10 kHz remain almost unchanged during charging.

[0037] Before detecting a change in battery voltage, the inventors detected a decrease in electrolyte resistance during charging cycles. They discovered that by detecting this decrease in electrolyte resistance during charging cycles, an indication of a short circuit can be determined.

[0038] [The effect of temperature changes]

[0039] Furthermore, the inventors considered the possibility that the decrease in electrolyte resistance caused by dendrite growth during charging and the decrease in electrolyte resistance caused by the increase in battery temperature during charging could occur simultaneously. As described in detail later, the short-circuit indication detection system and method according to this embodiment allow the inventors to envision obtaining the characteristics of electrolyte resistance change with temperature variation experimentally and evaluating the decrease in electrolyte resistance caused by dendrite growth during charging by comparing the predicted value of the resistance change caused by temperature variation with the actual measured value of electrolyte resistance.

[0040] [Short Circuit Indication and Detection System]

[0041] The short-circuit indication detection system according to this embodiment will be described with reference to the accompanying drawings. Figure 5 This is a block diagram illustrating the short-circuit indication detection system 1 of this embodiment. While not specifically limited, the short-circuit indication detection system 1 of this embodiment is installed in a vehicle (e.g., an automobile). The vehicle is not specifically limited, as long as it has a battery module installed. Automobiles can be exemplified by, for example, EVs (electric vehicles), PHVs (plug-in hybrid vehicles), and HVs (hybrid vehicles).

[0042] A short-circuit indication detection system 1 controls the charging and discharging of battery module 2. Battery module 2 includes multiple stacked battery cells 21. Each battery cell 21, forming an all-solid-state battery, includes at least a positive electrode, a solid electrolyte, and a negative electrode. The positive electrode may be formed from a positive electrode material that can desorb and intercalate lithium (Li). Although not specifically limited, materials such as NCM and NCA may be used as the positive electrode material. For example, sulfide solid electrolytes or oxide solid electrolytes may be used as the solid electrolyte, but not limited to these. The negative electrode only needs to contain lithium (e.g., lithium metal).

[0043] like Figure 1 As shown, the short circuit indication detection system 1 includes a controller 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, a DC-DC converter 14 connected to the load (power network), a pressure application mechanism 16, and a pressure sensor 17.

[0044] The controller 10 of this embodiment corresponds to an example of the "resistance measuring device" and "short circuit indication determining device" according to the present invention. The temperature sensor 13 of this embodiment corresponds to an example of the "temperature measuring device" according to the present invention. The pressure applying mechanism 16 of this embodiment corresponds to an example of the "pressure applying device" according to the present invention. The pressure sensor 17 of this embodiment corresponds to an example of the "pressure measuring device" according to the present invention.

[0045] The controller 10 is a battery control unit (BCU). The controller 10 consists of a memory (such as ROM or RAM) and a processor (such as CPU). Based on the detection voltage detected by the voltage sensor 11, the detection current detected by the current sensor 12, the detection temperature detected by the temperature sensor 13, etc., the controller 10 manages the state of the battery module 2 and determines the SOC operating range of the battery module 2 according to the state of the battery module 2.

[0046] According to this embodiment, the controller 10 can also determine whether there is an indication of a short circuit in the battery cells 21 included in the battery module 2. The controller 10 includes a resistance measurement unit 101, a storage unit 102, a prediction unit 103, a determination unit 104, a current control unit 105, and a pressure control unit 106.

[0047] The resistance measurement unit 101 measures the impedance of the battery cells 21 included in the battery module 2 and calculates the electrolyte resistance of the battery cells 21 based on the measured impedance. The resistance measurement unit 101 can measure the impedance of the battery cells 21 by means of, for example, EIS measurement. For example, based on the impedance of the battery 21 to a high-frequency AC signal of 10 kHz or higher, the resistance measurement unit 101 can calculate the electrolyte resistance. More specifically, the diameter of the impedance circle at 10 kHz or higher in the aforementioned Cole-Cole diagram can be used as the electrolyte resistance. This allows the electrolyte resistance to be calculated without being affected by electrode reaction resistance, etc., appearing in the impedance at low frequencies.

[0048] The resistance measurement unit 101 can output the calculated electrolyte resistance to the storage unit 102 and the determination unit 104.

[0049] In this embodiment, although not limited, the controller 10 includes a resistance measuring unit for measuring impedance. In addition to the controller 10, the short-circuit indication detection system 1 may also be equipped with an impedance measuring device. Alternatively, a signal containing high-frequency components is generated by the conversion operation of the DC-DC converter 14 and can be input to the battery cell 21.

[0050] Storage unit 102 stores the temperature measurement value input by temperature sensor 13 and the electrolyte resistance input by resistance measurement unit 101. According to this embodiment, storage unit 102 stores the battery temperature before charging as the battery temperature measured by temperature sensor 13 before charging battery module 2, and stores the electrolyte resistance before charging as the electrolyte resistance measured by resistance measurement unit 101 before charging battery module 2. Storage unit 102 outputs the battery temperature before charging and the electrolyte resistance before charging to prediction unit 103.

[0051] The prediction unit 103 calculates a predicted value for the electrolyte resistance based on the battery temperature and electrolyte resistance before charging, and the battery temperature during charging. This predicted value is calculated based on the experimentally obtained characteristics of the electrolyte resistance's change with temperature. A more detailed method for calculating the predicted value will be described later.

[0052] The determination unit 104 determines whether there is an indication that a short circuit has occurred between the positive and negative terminals of the battery cell 21. The determination unit 104 determines that such an indication exists when the decrease in electrolyte resistance measured by the resistance measurement unit 101 during charging is greater than a predetermined value or more than the decrease in electrolyte resistance caused by changes in battery temperature.

[0053] For example, the determining unit 104 compares the predicted value calculated by the prediction unit 103 with the measured value of the electrolyte resistance measured by the resistance measuring unit 101 during charging. When the comparison result indicates that the measured value is less than a predetermined value or more than the predicted value, an indication of a short circuit can be determined.

[0054] The current control unit 105 controls the discharge current from the battery module 2 to the load (power network) and the charging current from the charging device 3 to the battery module 2. For example, when the determining unit 104 determines that there is an indication of a short circuit, the current control unit 105 according to this embodiment can prevent the charging current from the charging device 3 from increasing, or decrease the charging current, or discharge the battery.

[0055] The pressure control unit 106 controls the pressure applied to the battery module 2 by controlling the pressure application mechanism 16. While not specifically limited, the pressure applied to the battery module 2 during charging and discharging is set to a performance-required pressure or higher. The performance-required pressure is set such that the resistance value of the battery cell 21 is the same as a predetermined threshold. The threshold is the maximum value of the resistance of the battery cell 21 within the range that allows the output and input of the charging-discharging power required for the operation of the vehicle control system, etc.

[0056] According to this embodiment, the pressure control unit 106 can control the pressure application mechanism 16 to reduce the pressure to be applied to the battery when the determining unit 104 determines that there is an indication that a short circuit has occurred.

[0057] Voltage sensor 11 is used to detect the voltage across the battery module 2. Voltage sensor 11 is connected between the positive and negative terminals of the battery module 2. Current sensor 12 is used to detect the current input to / output from the battery module 2. Current sensor 12 is connected to either the positive or negative terminal of the battery module 2. The measured values ​​from voltage sensor 11 and current sensor 12 are output to the current control unit 105 of controller 10.

[0058] Temperature sensor 13 is disposed in battery module 2. Temperature sensor 13 is a sensor used to detect the temperature of battery module 2. Although not specifically limited, the temperature of battery module 2 can be regarded as the temperature of battery cell 21. The measured value of temperature sensor 13 is output to storage unit 102 and prediction unit 103.

[0059] DC-DC converter 14 is a power converter that converts the voltage input from battery module 2 into a predetermined voltage and outputs power to a load (such as a motor). DC-DC converter 14 also converts the voltage input from a load (such as a motor or charging device) into a predetermined voltage and outputs power to battery module 2. DC-DC converter 14 is controlled by controller 10. Battery module 2 is connected to the input side of DC-DC converter 14, and the load is connected to the output side of DC-DC converter 14. The load may include a power network such as a motor inverter. In other words, battery module 2 is connected to the load via DC-DC converter 14.

[0060] The pressure application mechanism 16 applies pressure to the battery module 2 by pressing the battery module 2 along the stacking direction of the battery cells 21 in the battery module 2. The pressure application mechanism 16 in this embodiment includes a motor driver circuit 161, a motor 162, a gearbox 163, a pressure transmitter 164, a fixed end plate 165, a movable end plate 166, and a plurality of shafts 167.

[0061] Motor driver circuit 161 operates motor 162. Motor driver circuit 161 controls the drive operation of motor 162 based on control signals from controller 10.

[0062] The motor 162 includes a first drive shaft 162a. The motor 162 drives the first drive shaft 162a to rotate according to the output of the motor driver circuit 161.

[0063] The gearbox 163 is connected to the first drive shaft 162a and converts the rotational drive of the first drive shaft 162a into a drive motion of the pressure transmission body 164 toward the stacking direction.

[0064] The pressure transmitter 164 moves vertically via a drive force transmitted through a gearbox 163. The pressure transmitter 164 includes a second drive shaft 164a and a pressure transmitter plate 164b. The second drive shaft 164a is connected to the gearbox 163 to receive rotational drive motion from a first drive shaft 162a of the motor 162, which is transmitted by the gearbox 163. The pressure transmitter plate 164b is a plate that moves in a stacking direction in association with the rotation of the second drive shaft 164a. In this embodiment, when the pressure transmitter plate 164b moves downwards (as shown in the figure), the pressure applied to the battery module 2 can be controlled to move in the direction of increasing pressure. When the pressure transmitter plate 164b moves upwards (as shown in the figure), the pressure applied to the battery module 2 can be controlled to move in the direction of decreasing pressure.

[0065] A fixed end plate 165 and a movable end plate 166 constitute a pair of plate members and are connected to each other via a plurality of shafts 167. The fixed end plate 165 is fixed to the shafts 167 to support the battery module 2. Meanwhile, the movable end plate 166 is not fixed to the shafts 167, but is movable along the extension direction of the shafts 167. The movable end plate 166 applies pressure to the battery module 2 from above according to the force transmitted from the pressure transmitter 164. The movable end plate 166 can move along the stacking direction according to the expansion and contraction of the battery module 2 associated with charging and discharging, and according to the expansion and contraction of the battery module 2 associated with changes in the pressure applied to the battery module 2 by the movable end plate 166.

[0066] Pressure sensor 17 is a sensor that can measure the pressure applied to battery module 2. Pressure sensor 17 can output the detected pressure to pressure control unit 106 of controller 10.

[0067] Battery module 2 is electrically connected to charging device 3. Charging device 3, connected to battery cells 21, can be a device configured to charge battery module 2 installed in, for example, electric vehicles and hybrid vehicles. Charging of the on-board battery module 2 can be performed by removing the charging cable of charging device 3, engaging the charging gun at the end of the charging cable with the connector of the vehicle's charging port, and then operating the charging start switch. Controller 10 can control each of DC-DC converter 14 and charging device 3, such that the charging state of battery module 2 enters a target charging state while managing the state of charge (SOC) of the battery cells 21 included in battery module 2. On-board type charging device 3 is also available. Specifically, charging device 3 can be configured to allow the HV engine to generate electricity to charge battery module 2.

[0068] As described above, battery module 2 is electrically connected to a load, such as a motor. The load is a device powered by battery module 2, such as a motor used as a drive source for the vehicle, and auxiliary units such as air conditioning and lights. Battery module 2 discharges in response to a system request or an external power request under the control of controller 10. The system request corresponds to an instruction issued by an on-board computer (such as an ECU) during vehicle operation. Regarding an external power request, for example, in the case where a timer is set to turn on the air conditioning before the vehicle starts moving in response to an instruction from an external device (such as a mobile terminal) to ensure the interior temperature of the vehicle is appropriate when starting to drive, the instruction from the external device corresponds to an external power request.

[0069] Battery module 2, installed in electric and hybrid vehicles, can be used for vehicle grid integration (VGI). VGI is a technology for connecting the power system of electric or hybrid vehicles, in which battery module 2 is installed so that the power stored in battery module 2 is supplied to the system (load) via the power grid.

[0070] [Short Circuit Indication Detection Method]

[0071] The following describes a method for detecting a short circuit indication of the battery module 2 using the short circuit indication detection system 1 described above. Figure 6 This is a flowchart illustrating the short-circuit indication detection method according to this embodiment. For example... Figure 6 The short-circuit indication detection method shown is repeated for each predetermined cycle.

[0072] First, in step S1 of the short-circuit indication detection method, the resistance measurement unit 101 of the controller 10 measures the impedance of the battery cell 21. Based on the measured impedance, the current electrolyte resistance R of the battery cell 21 is calculated. SE_mea .

[0073] Next, in step S2, the current control unit 105 of the controller 10 determines whether the battery module 2 is charging.

[0074] When battery module 2 is not charging, in step S3 it is determined whether the measured value of the pressure (surface pressure) applied to battery 21, measured by pressure sensor 17, is a predetermined value or greater. This determination can be performed by pressure control unit 106 of controller 10.

[0075] While no specific limitations are imposed, the predetermined pressure value can be the performance-required pressure as described above. The resistance of the battery cell 21 varies depending on the surface pressure applied to it. In particular, when the surface pressure is lower than the performance-required pressure, the resistance of the battery cell 21 tends to increase sharply as the surface pressure decreases. That is, when the pressure applied to the battery is lower than the predetermined pressure, the pressure sensitivity of the electrolyte resistor becomes higher. Therefore, the accuracy of short-circuit detection can be improved by avoiding the use of the electrolyte resistor in the above-described conditions.

[0076] Meanwhile, when the surface pressure is at or above the performance requirement, the change in resistance due to the surface pressure is negligible. In this embodiment, in step S4, the storage unit 102 stores the electrolyte resistance R when the surface pressure applied to the battery cell 21 is a predetermined value or higher. SE As described later, this allows for improved accuracy in short-circuit indication detection.

[0077] When the measured value of the pressure (surface pressure) applied to battery 21 is a predetermined value or greater, in step S4, storage unit 102 stores (stores) the current electrolyte resistance R calculated in step S1. SE_mea As the electrolyte resistance R before charging SE_ini And store the current temperature T of the battery cell 21 as measured by temperature sensor 13. CELL As the temperature before charging TCELL_ini .

[0078] Then, in step S5, the current control unit 105 of the controller 10 determines whether there is a request to charge the battery module 2. In step S3, if the measured value of the pressure (surface pressure) is less than a predetermined value, the process skips step S4 and proceeds to step S5.

[0079] When a request to charge battery module 2 is received, charging of battery module 2 begins in step S6, and the short circuit indication detection ends. When no request to charge battery module 2 is received, the short circuit indication detection ends without further processing.

[0080] In step S2, when it is determined that battery module 2 is charging, in step S7 it is determined whether the measured value of the pressure applied to battery 21, as measured by pressure sensor 17, is a predetermined value or greater. Although not specifically limited, the predetermined value of the pressure can be similar to the pressure required for performance in step S3.

[0081] In such Figure 6 In the short circuit indication detection shown in the flowchart, after executing steps S1 to S5, when charging begins in step S6, battery module 2 is determined to be charging, and thereafter, short circuit indication detection is executed again.

[0082] When it is determined in step S7 that the pressure measurement value is a predetermined value or greater, in step S8, the prediction unit 103 predicts the current (during charging) battery temperature T. CELL To calculate the electrolyte resistance R SE Predicted value R SE_est .

[0083] Since each of the battery cells 21 generates heat during charging, the battery temperature T measured during charging in step S1 is... CELL The pre-charging temperature T of the battery cell 21 is higher than that before charging. CELL_ini The electrolyte resistance R can be utilized. SE With the temperature T of the battery cell 21 CELL The predicted value R is calculated based on the property of increasing and decreasing. SE_est In this embodiment, the resistance coefficient K can be used. T To calculate the predicted value R SE_est Resistivity K T Represents electrolyte resistance R SE Regarding the temperature T of battery cell 21 CELL The rate of change of resistivity K. Although no specific limit is imposed, the resistivity K... T The initial setting can be determined by experimentally confirming the change in electrolyte resistance caused by battery temperature.

[0084] Figure 7 This indicates the battery temperature T. CELL With resistivity K T A graph illustrating the relationship between the two. For example... Figure 7 The graph in the figure shows that the vertical axis represents the resistivity K. T The horizontal axis represents the temperature of the battery cell 21. Figure 7 The graph shown is obtained by using the battery temperature T CELL The electrolyte resistance R at 25°C SE_25 Plotted as a reference value (K) T = R SE / R SE_25 ), that is, the corresponding temperature T CELL Electrolyte resistance R SE The value relative to the electrolyte resistance R SE_25 Each rate of change (resistivity K) T When the battery temperature T CELL With resistivity K T When the relationship between the two elements becomes different for each of the battery cells 21, it is preferable to set a resistivity K for each of the battery cells 21. T .

[0085] Predicted value R SE_est The resistivity K can be used T The calculation is as follows. That is, the calculation is performed based on the current temperature T of the battery cell 21. CELL_now The corresponding resistivity K T_now And based on the battery temperature T before charging stored in storage unit 102 CELL_ini To calculate the resistivity K before charging T_ini Predicted value R SE_est It is calculated based on the following formula (1):

[0086] R SE_est = R SE_ini × (K T_now / K T_ini (1).

[0087] When it is determined in step S7 that the pressure measurement value is less than the predetermined value, the short circuit indication detection ends.

[0088] After performing step S8, in step S9, the determining unit 104 determines the electrolyte resistance R measured by the resistance measuring unit 101 during charging. SE The reduction amount D _mea Is it more important than the electrolyte resistance R caused by changes in battery temperature? SE The reduction amount D _estThe predetermined value is C or more. Specifically, in this embodiment, the reduction amount D is determined when the following formula (2) is satisfied. _mea The reduction in amount D _est Larger predetermined value C or more:

[0089] R SE_est ≥ R SE_mea + C(2).

[0090] The predetermined value C in formula (2) above is a margin used to avoid incorrect determination. This margin is set to avoid incorrect determination of whether a short circuit indication exists, which is caused by the measurement noise of the impedance and the difference between the battery cells 21. This margin can be experimentally determined by charging and discharging the battery under conditions that may lead to a short circuit. That is, |R| can be experimentally determined. SE_est - R SE_mea A preliminary study is conducted on a specific value of | that is large enough to indicate a high probability of a short circuit. For example, a predetermined value C can be set in R. SE_mea Within the range of 3% to 50%, preferably in R SE_mea Within the range of 5% to 20%, and more preferably in R SE_mea The range is between 5% and 15%.

[0091] Figure 8 (a) is the measured value R representing the electrolyte resistance during charging. SE_mea and predicted value R SE_est Example graph. Figure 8 (b) represents the battery temperature T during charging. CELL A graph showing an example of change. Figure 8 An example of a short circuit occurring between the positive and negative terminals of battery cell 21 is shown.

[0092] like Figure 8 As shown in (b), when charging of battery cell 21 begins, the temperature T of battery cell 21 is... CELL It increases over time. For example... Figure 8 As shown in (a), the measured value R of the electrolyte resistance was actually measured after charging began. SE_mea It became significantly lower than the predicted value R of the electrolyte resistance caused by temperature rise. SE_est In this exemplary case, at battery temperature T CELL_now The actual measured electrolyte resistance R SE_mea Electrolyte resistance R before charging SE_ini The reduction amount D _mea Compared to battery temperature T CELL_now The predicted value R SE_est Electrolyte resistance R before charging SE_iniThe reduction amount D _est Larger predetermined value C or more (D) _mea - D _est ≥ C).

[0093] The resistance of battery cell 21 degrades with increasing charge and discharge cycles. Electrolyte resistance R SE This increase is also associated with the decline. Based on the state of battery cell 21 before charging, according to the electrolyte resistance R before charging... SE_ini Estimated predicted value R SE_est The comparison is used between the electrolyte resistance before charging and the electrolyte resistance during charging in the same charge-discharge cycle, as indicated by the above formula (1) (to obtain the difference). This allows the short-circuit indication to be determined by eliminating the effects of decay, and thus improves the accuracy of short-circuit indication detection.

[0094] In step S9 as described above, when the amount D is reduced _mea The reduction in amount D _est When the predicted value C or more is large, the determining unit 104 determines in step S10 that a short circuit indication exists between the positive and negative electrodes of the battery cell 21. In other words, the predicted value R is... SE_est The measured value R of the electrolyte resistance actually measured during charging. SE_mea Compare the measured values ​​R. SE_mea Compared to the predicted value R SE_est When the predetermined value C is less than or equal to a certain value, a short circuit indication is determined.

[0095] Subsequently, in step S11, the determining unit 104 outputs a signal containing information about the presence of a short circuit indication to the current control unit 105 and the pressure control unit 106. The current control unit 105 and the pressure control unit 106 perform processing to suppress the occurrence of a short circuit in the battery cell 21.

[0096] In this situation, after receiving a signal from the determining unit 104, the current control unit 105 prevents an increase in the charging current to the battery cell 21, or reduces the charging current, or discharges the battery cell 21. Alternatively, the above-described processes can be combined. Since this suppresses dendrite growth, it can suppress the occurrence of short circuits in the battery cell 21.

[0097] In the example using combined processing, control is executed to prevent an increase in the charging current (which remains constant) during this short-circuit indication detection. When a short-circuit indication is again determined in the next short-circuit indication detection, control is executed to reduce the charging current. If it is further determined that a short-circuit indication still exists in subsequent short-circuit indication detections, battery cell 21 can discharge. After the charging current is reduced, it is preferable to set the charging current to the minimum current value allowed by the vehicle control system.

[0098] Although not specifically limited, the pressure control unit 106 can perform processes to suppress short circuits, allowing for a reduction in the pressure applied to the battery cell 21. Since this suppresses dendrite growth, it can also suppress the occurrence of short circuits in the battery cell 21.

[0099] In step S9, when the reduction amount D is determined _mea There is no reduction in amount D _est When the value is greater than or equal to the predetermined value C, the short circuit indication detection ends.

[0100] According to the aforementioned short-circuit indicator detection system and method, the use of an electrolyte resistor allows for the detection of short-circuit indicators unaffected by changes in electrode reaction resistance, etc. Since indicators leading to a short circuit can be detected before dendrite growth and short-circuit occurrence, early detection of short circuits is possible.

[0101] Explanation of reference numerals in the attached figures

[0102] 1. Short Circuit Indication and Detection System

[0103] 10 Controllers

[0104] 11 Voltage Sensor

[0105] 12 Current Sensors

[0106] 13 Temperature Sensor

[0107] 14 DC-DC converter

[0108] 16 Pressure application mechanism

[0109] 17 Pressure Sensor

[0110] 2 Battery Modules

[0111] 21. Battery cell.

Claims

1. A short-circuit indication and detection system, comprising: A battery comprising a positive electrode, a lithium-containing negative electrode, and a solid electrolyte; A temperature measuring device that measures the battery temperature as the battery temperature; A resistance measuring device for measuring the electrolyte resistance of the solid electrolyte; and A short-circuit indication determining device that determines whether there is an indication of a short circuit between the positive and negative terminals, wherein... The short-circuit indication determination device determines that the indication exists when the decrease in electrolyte resistance measured by the resistance measuring device during charging is greater than a predetermined value or more than the decrease in electrolyte resistance caused by changes in battery temperature.

2. The short-circuit indication and detection system according to claim 1, wherein, The short-circuit indication and determination device includes: The storage unit stores the battery temperature before charging as the battery temperature measured by the temperature measuring device before charging, and stores the electrolyte resistance before charging as the electrolyte resistance measured by the resistance measuring device before charging. A prediction unit, based on the battery temperature before charging and the electrolyte resistance before charging, calculates a predicted value for the electrolyte resistance according to the battery temperature during charging; and The determining unit compares the predicted value with the measured value of the electrolyte resistance measured by the resistance measuring device during charging, and determines that the indication exists when the measured value is smaller than the predicted value by a predetermined value or more.

3. The short-circuit indication and detection system according to claim 1, wherein, The resistance measuring device calculates the electrolyte resistance based on the battery's impedance relative to an AC signal with a frequency of 10 kHz or higher.

4. The short-circuit indication and detection system according to claim 1, wherein, When the short circuit indication determination device has determined that the indication exists, the charge-discharge device that charges and discharges the battery avoids increasing the charging current of the battery, or decreases the charging current, or discharges the battery.

5. The short-circuit indication detection system according to any one of claims 1 to 4, wherein, The short-circuit indication detection system further includes: A pressure applying device that applies pressure to the battery; and A pressure measuring device measures the pressure applied to the battery, wherein... When the pressure measured by the pressure measuring device is equal to or greater than a predetermined value, the short-circuit indication determining device performs a determination of whether the indication exists.

6. The short-circuit indication and detection system according to claim 5, wherein, When the short circuit indication determination device has determined that the indication exists, the pressure application device reduces the pressure applied to the battery.

7. A short-circuit indication detection method for determining whether an indication of a short circuit has occurred between the positive and negative electrodes of a battery, the battery comprising the positive electrode, the lithium-containing negative electrode, and a solid electrolyte, the method comprising: The battery temperature is measured and recorded as the battery's temperature. Measure the electrolyte resistance of the solid electrolyte; as well as The indication is determined to exist when the decrease in electrolyte resistance during charging is greater than a predetermined value or more than the decrease in electrolyte resistance caused by temperature changes in the battery.

Images