All-solid-state battery system and method for controlling battery module in all-solid-state battery system

Abstract

To detect micro-short circuits caused by dendrites formed in an all-solid-state cell, and effectively eliminate or reduce the formed dendrites.SOLUTION: An all-solid-state battery system according to the present invention includes a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode. The all-solid-state battery system includes a pressurizing mechanism that pressurizes the battery module at a predetermined surface pressure equal to or lower than a predetermined upper pressure limit, a micro-short circuit detection unit that detects a micro-short circuit in a cell of the battery module, and a control device that controls charging and discharging of the battery module. When the micro-short circuit is detected, the control device controls the discharging of the battery module for a predetermined period of time. Furthermore, the control device controls the pressurizing mechanism to pressurize the battery module at a surface pressure lower than the predetermined surface pressure during the discharging.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an all-solid-state battery system and a method for controlling a battery module in an all-solid-state battery system. [Background technology]

[0002] In recent years, the use of all-solid-state lithium-ion secondary batteries using a solid electrolyte has been proposed for the on-board battery systems of electric vehicles, instead of lithium-ion secondary batteries (sometimes simply referred to as "lithium batteries") that use an electrolyte for the electrode reaction.

[0003] In lithium-ion secondary batteries, the internal state may deteriorate depending on the usage conditions, causing a phenomenon such as a sudden drop in output voltage, so the internal state is detected or estimated. For example, Patent Document 1 below discloses a technique for measuring impedance when a lithium-ion secondary battery is in a low charge state (SOC is 10% or less) and detecting the state of lithium deposition in the negative electrode according to the measured value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-212513 A Summary of the Invention [Problem to be solved by the invention]

[0005] Depending on the usage conditions of the lithium-ion secondary battery, lithium may precipitate at one electrode (e.g., the negative electrode) in the cell and grow through the electrolyte layer toward the other electrode (e.g., the positive electrode), forming so-called "dendrites" that cause micro-short circuits and progress in the deterioration of the internal state of the cell. The technology disclosed in the above Patent Document 1 was limited to simply detecting the state of lithium precipitation at the negative electrode of the lithium-ion secondary battery, but was unable to eliminate or reduce the formed dendrites and restore the internal state of the deteriorated lithium-ion secondary battery.

[0006] In recent years, the use of all-solid-state battery systems consisting of all-solid-state batteries using solid electrolytes has been proposed as on-board battery systems for electric vehicles, instead of battery systems consisting of conventional lithium-ion secondary batteries using electrolyte solutions. Therefore, even in such all-solid-state battery systems, a technology for detecting deterioration of the internal state of a cell and recovering the internal state is similarly desired.

[0007] Therefore, the present invention provides an all-solid-state battery system and a method for controlling a battery module in an all-solid-state battery system, which can detect a micro-short circuit caused by dendrites formed in an all-solid-state cell using an electrode made of a lithium-containing metal compound and a solid electrolyte, and can efficiently eliminate or sufficiently reduce the formed dendrites. [Means for solving the problem]

[0008] The present invention, which aims to solve the above problems, includes the following invention-specific matters and technical features.

[0009] The present invention according to one aspect is an all-solid-state battery system including a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode. The all-solid-state battery system includes a pressurizing mechanism that pressurizes the battery module at a predetermined surface pressure equal to or lower than a predetermined upper pressure limit, a micro-short circuit detection unit that detects a micro-short circuit in a cell of the battery module, and a control device that controls charging and discharging of the battery module. When the micro-short circuit is detected, the control device controls the discharging of the battery module for a predetermined period of time. Furthermore, the control device controls the pressurizing mechanism to pressurize the battery module at a surface pressure lower than the predetermined surface pressure during the discharging.

[0010] According to one aspect, the present invention is a method for controlling a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode. The control method includes controlling a pressurizing mechanism to pressurize the battery module at a predetermined surface pressure equal to or lower than a predetermined upper pressurization limit, detecting a micro-short circuit in a cell of the battery module based on a measurement signal output from a sensor while the battery module is being charged, and stopping the charging of the battery module and discharging the battery module when the micro-short circuit is detected. The discharging includes controlling the pressurizing mechanism to pressurize the battery module at a surface pressure lower than the predetermined surface pressure.

[0011] In this specification, the term "means" does not simply mean physical means, but also includes cases where the functions of the means are realized by software. The functions of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means. Furthermore, the term "system" refers to a logical collection of multiple devices (or functional modules that realize specific functions), and it does not matter whether each device or functional module is contained within a single housing. Effect of the Invention

[0012] According to the present invention, there are provided an all-solid-state battery system and a method for controlling a battery module in an all-solid-state battery system, which can efficiently eliminate or sufficiently reduce dendrites formed in a cell using an electrode made of a metal compound containing lithium.

[0013] Other technical features, objects, and operational effects or advantages of the present invention will become apparent from the following embodiments described with reference to the accompanying drawings. The effects described in this specification are merely examples and are not limited thereto, and other effects may also be present. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a block diagram showing an example of a schematic configuration of an all-solid-state battery system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram for explaining an example of a schematic configuration of an all-solid-state battery pack of the all-solid-state battery system according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing an example of the external configuration of a cell constituting a battery module in an all-solid-state battery system according to one embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining an example of a functional model of a control device of an all-solid-state battery system according to one embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart for explaining an example of a control method for an all-solid-state battery pack in an all-solid-state battery system according to one embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining dendrites formed in a cell that constitutes a battery module. [Figure 7] FIG. 7 is a flowchart for explaining another example of the control method of the all-solid-state battery pack in the all-solid-state battery system according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude various modifications and application of techniques not specified below. The present invention can be implemented by various modifications (for example, combining the respective embodiments) within the scope of the gist of the present invention. In addition, in the following description of the drawings, the same or similar parts are represented by the same or similar reference numerals. The drawings are schematic and do not necessarily correspond to actual dimensions, ratios, etc. The drawings may also include parts with different dimensional relationships and ratios.

[0016] 1 is a block diagram showing an example of a schematic configuration of an all-solid-state battery system according to an embodiment of the present invention. As shown in the figure, the all-solid-state battery system 1 includes, for example, a battery pack 10, a load 20, and a control device 30. Such an all-solid-state battery system 1 can be mounted on a vehicle and used as a driving power source for the vehicle.

[0017] The battery pack 10 is composed of a plurality of battery modules 11 electrically connected in series and / or parallel. As described below, each battery module 11 is composed of a plurality of cells 110 stacked together. In the present disclosure, the cells 110 are all-solid-state cells composed of a positive electrode, a solid electrolyte layer, and a negative electrode. The negative electrode of the cells 110 is composed of a metal compound containing at least lithium. The battery module 11 composed of all-solid-state cells is typically pressurized with a predetermined surface pressure by a pressurizing mechanism 130 so that the interfaces of the members of the cells 110 are securely in contact with each other (see FIG. 2).

[0018] The battery pack 10 also includes various sensors 12. The sensors 12 include, for example, a temperature sensor 12a, a voltage sensor 12b, and a current sensor 12c. The temperature sensor 12a measures the temperature of one or several cells 110 or battery modules 11, and outputs a signal (temperature measurement signal) corresponding to the measured value to the control device 30. The voltage sensor 12b is provided, for example, for each cell 110, and measures the voltage (for example, operating voltage or closed circuit voltage) of each cell 110, and outputs a signal (voltage measurement signal) corresponding to the measured value to the control device 30. The current sensor 12c measures the value of the current output from the battery module 11 (or the current input to the battery module 11), and outputs a signal (current measurement signal) corresponding to the measured value to the control device 30. The sensor 12 may also include an impedance sensor. The impedance sensor applies, for example, a small AC signal to the cell 110, and outputs a response signal to the control device 30.

[0019] The load 20 is a high-power device that consumes power supplied (output) from the battery pack 10 (i.e., each battery module 11). Typically, the load 20 is a motor for driving the wheels of a vehicle. The load 20 may also include a function as a power generation device or a power supply device. In other words, the battery pack 10 is configured to be chargeable by power supplied from the load 20 as a power generation device or a power supply device.

[0020] The charging device RC is a device for charging the battery pack 10. The charging device RC is installed in, for example, a charging station, and the battery pack 10 is connected to the charging device RC. Alternatively, the battery pack 10 may be charged from a general household power source instead of the charging device RC.

[0021] The control device 30 is configured to include a CPU, a memory, and various computer hardware elements, and is a battery management system (BMS) that controls the current or power of the battery pack 10 in the all-solid-state battery system 1. Specifically, the control device 30 can control the output current from the battery pack 10 to be optimal, based on measurement signals output from various sensors 12 of the battery pack 10.

[0022] In the present disclosure, the control device 30 detects a micro-short circuit occurring in a cell 110 constituting a battery module 11 of the battery pack 10 based on various measurement signals output from the sensor 12 while the battery pack 10 is being charged. The main cause of the micro-short circuit in the cell 110 is believed to be dendrites formed when lithium precipitated from the negative electrode N made of a lithium metal compound penetrates into the solid electrolyte layer SE and grows on the positive electrode P side (see FIG. 6(a)). The dendrites d formed inside the cell 110 generate a loop current and reduce the performance of the battery module 11. Such a micro-short circuit is detected, for example, from the voltage-current characteristics during charging.

[0023] For example, the control device 30 calculates the amount of rise in the voltage value per unit time based on the current value indicated by the current measurement signal and the voltage value indicated by the voltage measurement signal when the battery pack 10 is being charged, and determines the presence or absence of a micro-short circuit based on the calculated amount of rise in the voltage value. Alternatively, the control device 30 calculates the internal resistance of the cell 110 based on the current value indicated by the current measurement signal and the voltage drop amount indicated by the voltage measurement signal, and determines the presence or absence of a micro-short circuit based on the calculated internal resistance. Alternatively, the control device 30 compares the response signal with a reference AC signal to calculate a complex impedance consisting of a resistance component and a reactance component as the internal resistance of the cell 110, and determines the presence or absence of a micro-short circuit based on the calculated internal resistance.

[0024] When the control device 30 detects a micro-short circuit, it temporarily stops charging the battery pack 10 and switches to discharging. For example, the control device 30 discharges the battery module 11 at a maximum allowable current value defined for the battery module 11 in terms of design. At this time, the control device 30 controls the pressurizing mechanism 130 so that a predetermined surface pressure on the battery module 11 is reduced. Instead of or in addition to controlling the pressurizing mechanism 130, the control device 30 may control the temperature adjustment device 140 so that the temperature of the battery module 11 is reduced.

[0025] 2 is a diagram for explaining an example of a schematic configuration of an all-solid-state battery pack of an all-solid-state battery system according to an embodiment of the present invention. In the diagram, one of a plurality of battery modules 11 constituting a battery pack 10 is shown. As shown in the diagram, the battery module 11 includes a cell 110, a holding plate 120, a pressurizing mechanism 130, and a temperature adjustment device 140.

[0026] As described above, the battery module 11 is configured by stacking a plurality of cells 110. The cells 110 are solid-type cells in which components such as a positive electrode, a solid electrolyte layer, and a negative electrode are tightly bonded together.

[0027] 3 is a diagram showing an example of the external configuration of a cell 110 constituting the battery module 11. Specifically, FIG. 3(a) shows a side view of the cell 110, and FIG. 3(b) shows a plan view. As shown in these figures, the cell 110 includes a covering portion 111 that covers the entirety of each member (cell body) to protect it. The covering portion 111 is, for example, a composite laminate film made of a metal foil and a resin layer.

[0028] 2, a pair of holding plates 120 are disposed on the upper and lower surfaces of the battery module 11 and hold the battery module 11 in a sandwiched manner. That is, the holding plates 120 are composed of a holding plate 120 that abuts against the cell 110 located in the bottom layer among the stacked cells 110 of the battery module 11, and a holding plate 120 that abuts against the cell 110 located in the top layer. The holding plates 120 are, for example, rigid metal plates.

[0029] The pressurizing mechanism 130 applies a predetermined surface pressure to the battery module 11 via the holding plate 120 under the control of the control device 30. For example, the pressurizing mechanism 130 includes a pantograph jack 131 and a motor 132 that drives the pantograph jack 131 via a drive gear (not shown). Although the pressurizing mechanism 130 is shown as a jack-type pressurizing mechanism using the motor 132, the pressurizing mechanism 130 is not limited to this. For example, the pressurizing mechanism 130 may be configured by a hydraulic jack.

[0030] The temperature adjustment device 140 adjusts the temperature of the battery module 11 to a predetermined set temperature under the control of the control device 30. For example, the temperature adjustment device 140 may be a heat exchanger. Alternatively, the temperature adjustment device 140 may be a part of an air conditioning mechanism (so-called air conditioner) built into a vehicle or an air-cooling fan. In the present disclosure, when a micro-short circuit is detected in a cell 110 of a certain battery module 11 while the battery pack 10 is being charged, the temperature adjustment device 140 controls air conditioning under the control of the control device 30 so that the temperature of the battery module 11 that has been switched from charging to discharging is lowered.

[0031] 4 is a diagram for explaining an example of a functional model of a control device of an all-solid-state battery system according to an embodiment of the present invention. As shown in the figure, the functional model of the control device 30 includes, for example, a charge / discharge control unit 31, a micro-short circuit detection unit 32, a pressure control unit 33, and a temperature control unit 34.

[0032] The charge / discharge control unit 31 controls charging of the battery pack 10 by the charging device RC. For example, when the charge / discharge control unit 31 detects a charging current from the charging device RC, it controls the battery pack 10 to start charging at a predetermined charging current value. In the present disclosure, when a micro-short circuit (i.e., a dendrite) is detected in a cell 110 of a certain battery module 11 by a micro-short circuit detection unit 32 described later during charging, the charge / discharge control unit 31 controls the battery pack 10 to stop charging once and start discharging at a predetermined discharge current value. This causes lithium dendrites formed in the cell 110 to disappear or be sufficiently reduced, and the effect of the micro-short circuit on the performance of the battery module 11 can be eliminated or reduced. The predetermined discharge current value is, for example, a maximum allowable current value defined by design for the battery module 11 or a value close to this. By passing such a high discharge current value through the cell 110 of the battery module 11, it is possible to promote the disappearance or sufficient reduction of dendrites and quickly recover the internal state of the battery module 11.

[0033] After the above-mentioned discharge, the charge / discharge control unit 31 lowers the upper limit current value of the predetermined charging current value at the next charge. In other words, since it is considered that the cell 110 in which dendrites have been formed is likely to have dendrites formed again, the recurrence of micro-short circuit in the cell 110 can be prevented by keeping the upper limit current value at the time of charging low.

[0034] The micro short circuit detection unit 32 detects a micro short circuit in the battery module 11 (i.e., the cell 110) based on the measurement signal output from the sensor 12. For example, under the control of the charge / discharge control unit 31, the micro short circuit detection unit 32 judges whether or not the rise in voltage value per unit time is equal to or less than a predetermined reference value while the battery module 11 is being charged with a current of a predetermined charging current value, and judges that a micro short circuit has been detected in the cell 110 when it judges that the rise in voltage value per unit time is equal to or less than the predetermined reference value. In this way, the micro short circuit detection unit 32 can efficiently detect a micro short circuit when charging the battery module 11. When it judges that a micro short circuit has been detected, the micro short circuit detection unit 32 outputs a detection signal to the pressure control unit 33 and / or the temperature control unit 34.

[0035] Alternatively, the micro short circuit detector 32 may detect a micro short circuit in the cell 110 based on the internal resistance of the cell 110. For example, the micro short circuit detector 32 calculates the internal resistance of the cell 110 based on a voltage drop based on a voltage measurement signal output from the voltage sensor 12b at a predetermined timing and a current value based on a current measurement signal output from the current sensor 12c, and when it is determined that the calculated internal resistance is equal to or less than a predetermined reference value, it may determine that a micro short circuit has been detected and output a detection signal. Alternatively, the micro short circuit detector 32 may use a complex impedance consisting of a resistance component and a reactance component calculated by comparing a response signal output from an impedance sensor (not shown) with a reference AC signal as the internal resistance. This allows the micro short circuit detector 32 to efficiently detect a micro short circuit when charging the battery module 11.

[0036] The pressurization control unit 33 controls the pressurization mechanism 130 to apply a predetermined surface pressure to the battery module 11 that is equal to or less than a predetermined upper limit pressurization value. The predetermined surface pressure is, for example, but not limited to, several kPa to several MPa. The predetermined upper limit pressurization value is the upper limit of the surface pressure applied to the battery module 11 during normal operation, and can be dynamically set according to the specifications and state of the battery module 11 (the internal state of the cells 110).

[0037] In the present disclosure, when the pressurization control unit 33 receives a detection signal indicating that a micro-short circuit has been detected from the micro-short circuit detection unit 32, the pressurization control unit 33 controls the pressurization mechanism 130 to pressurize the corresponding battery module 11 at a surface pressure (for example, a first surface pressure) lower than the current surface pressure for a predetermined time in response to the start of discharge of the battery pack 10 under the control of the charge / discharge control unit 31. That is, when the battery module 11 during discharge is pressurized at a surface pressure lower than the predetermined surface pressure during normal operation, the internal resistance of the cell 110 as a whole increases, while the resistance value of the portion of the cell 110 where the dendrites are formed does not change at all or hardly at all even with the decrease in surface pressure. For this reason, the current density in the portion of the cell 110 where the dendrites are formed due to discharge increases relatively, and it can be expected that the discharge current will concentrate on the portion where the dendrites are formed, which will quickly dissolve the dendrites and cause them to disappear or be sufficiently reduced.

[0038] In addition, the pressurization control unit 33 lowers the predetermined upper limit pressurization value after a predetermined time has elapsed since pressurization was started at a low surface pressure. In other words, since it is considered that dendrites are easily formed again in the cell 110 in which dendrites have been formed, it is necessary to prevent the lithium dendrites precipitated from the electrode (e.g., the negative electrode) from corroding the solid electrolyte layer. Therefore, the pressurization control unit 33 lowers the predetermined upper limit pressurization value so that pressurization is not performed at the same surface pressure as in the state before the micro-short circuit was detected. This suppresses the corrosion of the solid electrolyte layer by the lithium dendrites precipitated from the electrode (e.g., the negative electrode) of the cell 110, making it possible to prevent the recurrence of the micro-short circuit.

[0039] In addition, the pressurizing control unit 33 may determine a set value of the surface pressure to be applied to the battery module 11 during discharge according to the current state of charge (SOC) of the battery module 11. The surface pressure referred to here is a surface pressure lower than the current surface pressure. That is, a lower surface pressure on the battery module 11 means an increase in the internal resistance of the cells 110, and therefore, when the battery module 11 is discharged in such a state, the output voltage reaches a lower limit voltage defined by design earlier than when the battery module 11 is pressurized with a normal surface pressure. Therefore, the pressurizing control unit 33 controls the pressurizing mechanism 130 so that the higher the SOC of the battery module 11 at the current time (i.e., at the start of discharge), the lower the surface pressure is compared to the current surface pressure. For example, the pressurizing control unit 33 determines whether the current SOC of the battery module 11 is equal to or higher than a first threshold value, and when it determines that the SOC of the battery module 11 is equal to or higher than the first threshold value, it determines a first surface pressure P1 (i.e., P>P1) lower than the current (normal operation) surface pressure P. On the other hand, when the pressurization control unit 33 determines that the pressure is not equal to or greater than the first threshold value, it determines a second surface pressure P2 (i.e., P>P2>P1) that is lower than the current surface pressure P and higher than the first surface pressure P1. This makes it possible to prevent the output voltage of the battery module 11 from reaching the lower limit voltage defined by design before the dendrites in the cells 110 disappear or are sufficiently reduced.

[0040] The temperature control unit 34 controls the temperature adjustment device 140 so that the temperature of each battery module 11 becomes a predetermined temperature. The predetermined temperature is, for example, 25 to 30 degrees, but is not limited thereto. In the present disclosure, when the temperature control unit 34 receives a detection signal from the micro-short circuit detection unit 32, the temperature control unit 34 controls the temperature adjustment device 140 so that the battery module 11 is cooled at a temperature (for example, a first temperature) lower than the current temperature for a predetermined time when the battery module 11 starts discharging. That is, by cooling the discharging battery module 11 at a temperature lower than the predetermined temperature during normal operation, the resistance value of the portion in which the dendrite is formed in the cell 110 does not change at all or almost even with the decrease in temperature, while the internal resistance of the entire cell 110 increases, so that the current density in the cell 110 due to discharging increases relatively, and the discharge current is concentrated in the portion in which the dendrite is formed, thereby quickly dissolving the dendrite and causing it to disappear or to be sufficiently reduced.

[0041] The temperature control unit 34 may also determine the set temperature of the battery module 11 during discharging according to the state of charge (SOC) of the battery module 11 at the present time. The set temperature here is a temperature lower than the current temperature. That is, a lower temperature for the battery module 11 means an increase in the internal resistance of the cells 110, and therefore, when the battery module 11 is discharged in such a state, the output voltage reaches the lower limit voltage defined by design earlier than when the battery module 11 is at a normal temperature. Therefore, the temperature control unit 34 controls the temperature adjustment device 140 so that the higher the SOC of the battery module 11 at the present time (i.e., at the start of discharging), the lower the temperature of the battery module 11 becomes compared to the present temperature. For example, the temperature control unit 34 determines whether the SOC of the battery module 11 at the present time is equal to or higher than a first threshold value, and when it determines that the SOC of the battery module 11 is equal to or higher than the first threshold value, it determines the first temperature T1 (i.e., T>T1) that is lower than the current (normal operation) temperature T. On the other hand, when the temperature control unit 34 determines that the temperature is not equal to or higher than the first threshold value, it determines a second temperature T2 that is lower than the current temperature T and higher than the first temperature T1 (i.e., T>T2>T1). This makes it possible to prevent the output voltage of the battery module 11 from reaching the lower limit voltage defined by design before the dendrites in the cells 110 disappear or are sufficiently reduced.

[0042] 5 is a flowchart for explaining an example of a control method for an all-solid-state battery pack in an all-solid-state battery system according to an embodiment of the present invention. The figure shows a control method for reducing the surface pressure on a battery module 11 to discharge the battery pack 10 when a micro-short circuit is detected in a cell 110 of the battery module 11 during charging of the battery pack 10. Such a control method is realized, for example, by the control device 30 executing a predetermined battery control program under the control of a CPU and cooperating with other hardware.

[0043] As shown in the figure, the control device 30 monitors whether charging of the battery pack 10 has started (S501). For example, if the charging device RC is connected to the battery pack 10 and charging has started, the control device 30 detects this (Yes in S501), and then performs a micro-short circuit detection process (S502) and determines whether a micro-short circuit has been detected (S503).

[0044] 6(a), depending on the usage of the battery pack 10, lithium precipitates from the negative electrode N made of a lithium-containing metal compound in the cell 110, and grows in the solid electrolyte layer SE toward the positive electrode P to form a dendrite d, causing a micro-short circuit. Therefore, the detection of a micro-short circuit is performed by electrically measuring the internal state of the cell 110.

[0045] More specifically, in the process of detecting a micro-short circuit, the control device 30 controls the battery module 11 so that a current of a predetermined charging current value is input, determines the amount of rise in the voltage value per unit time according to the time-dependent voltage measurement signal output from the voltage sensor 12b, and judges whether the determined amount of rise in the voltage value per unit time is equal to or less than a predetermined reference value. When the control device 30 judges that the amount of rise in the voltage value per unit time is equal to or less than the predetermined reference value, it detects that a micro-short circuit has occurred in the cell 110. Alternatively, the control device 30 may measure the internal resistance of the cell 110 as described above, and detect a micro-short circuit based on the measured internal resistance.

[0046] Returning to FIG. 5, if the control device 30 determines that no micro-short circuit has been detected in the cell 110 (No in S503), it continues charging the battery pack 10 as normal, and ends the process when charging is completed (Yes in S512).

[0047] On the other hand, if the control device 30 determines that a micro-short circuit has been detected in the cell 110 (Yes in S503), the control device 30 determines a set value of the surface pressure to be applied to the battery module 11 during discharge based on the current state of charge (SOC) of the battery module 11 (S504).

[0048] For example, the controller 30 controls the pressurizing mechanism 130 so that the higher the SOC of the battery module 11 at the current time (ie, at the time when discharge starts), the lower the surface pressure applied relative to the current surface pressure.

[0049] Next, the control device 30 temporarily stops charging the battery module 11 and switches to discharging at a predetermined discharge current value (S505). Next, the control device 30 controls the pressurizing mechanism 130 to pressurize the battery module 11 at the determined predetermined surface pressure. That is, the battery module 11 including the cell 110 in which a micro-short circuit has been detected is pressurized at a surface pressure lower than the predetermined surface pressure applied during normal operation during discharging. As a result, the resistance value of the portion other than the portion in which the dendrite, which is the cause of the micro-short circuit, is relatively increased, so that the current density in the portion in which the dendrite is formed relatively increases, and it is expected that the discharge current will concentrate in the portion in which the dendrite is formed. As a result, for example, as shown in FIG. 6(b), the dendrite d is quickly dissolved and disappears or is sufficiently reduced.

[0050] The control device 30 monitors whether the above-mentioned discharge and pressurization have continued for a predetermined time (S507). When the control device 30 determines that the above-mentioned discharge and pressurization have continued for a predetermined time (Yes in S507), the control device 30 stops the discharge and resumes the charging (S508), and monitors whether the charging has been completed (S509). Note that instead of resuming the charging after the predetermined time has passed, the control device 30 may, for example, detect a micro-short circuit again, and resume the charging when a certain level of improvement in the internal state of the cell 110 is observed.

[0051] When the control device 30 determines that charging is completed after resuming charging (Yes in S509), the control device 30 lowers the upper limit pressure value of the predetermined surface pressure during normal operation (S510). This suppresses the erosion of the solid electrolyte layer by lithium dendrites precipitated from the electrode (e.g., the negative electrode) of the cell 110, and makes it possible to prevent the recurrence of the micro-short circuit.

[0052] Next, the control device 30 lowers the upper limit current value during the next charge (S511). In other words, since it is considered that the cell 110 in which dendrites have been formed is prone to re-formation of dendrites, the upper limit current value during charging is kept low to prevent the recurrence of micro-short circuit in the cell 110.

[0053] In addition, if the control device 30 determines that the micro-short circuit in the cell 110 cannot be sufficiently reduced after the above-mentioned charging and pressurization, it can control the charging so that the battery module 11 or battery pack 10 including the cell 110 that still has a micro-short circuit is not charged.

[0054] FIG. 7 is a flowchart for explaining another example of the control method of the all-solid-state battery pack in the all-solid-state battery system according to one embodiment of the present invention. In the figure, a control method is shown in which, when a micro-short circuit is detected in a cell 110 of a certain battery module 11 during charging of the battery pack 10, the temperature of the battery module 11 is lowered to discharge the battery. Such a control method is realized, for example, by the control device 30 executing a predetermined battery control program under the control of a CPU and cooperating with other hardware. Note that the control method shown in the figure is similar to the control method of lowering the surface pressure shown in FIG. 5, and therefore, the details thereof will be omitted as appropriate in the following description.

[0055] As shown in the figure, when the control device 30 detects the start of charging of the battery pack 10 (Yes in S701), it performs a micro-short circuit detection process (S702) and determines whether a micro-short circuit has occurred (S703).

[0056] If the control device 30 determines that a micro-short circuit has occurred in the cell 110 (Yes in S703), the control device 30 determines the set temperature of the battery module 11 during discharging according to the current state of charge (SOC) of the battery module 11 (S704).

[0057] For example, the control device 30 controls the temperature adjustment device 140 so that the higher the SOC of the battery module 11 at the current time (i.e., at the start of discharge), the lower the temperature will be relative to the current set temperature. For example, the control device 30 determines whether the current SOC of the battery module 11 is equal to or higher than a first threshold value, and if it determines that the SOC of the battery module 11 is equal to or higher than the first threshold value, it determines a first set temperature that is lower than the current set temperature (during normal operation), whereas if it determines that the SOC is not equal to or higher than the first threshold value, it determines a second set temperature that is lower than the current set temperature and higher than the first set temperature.

[0058] Next, the control device 30 temporarily stops charging the battery module 11 and switches to discharging at a predetermined discharge current value (for example, a maximum allowable current value) (S705). Next, the control device 30 controls the temperature adjustment device 140 so that the temperature of the battery module 11 becomes the determined predetermined set temperature. That is, the battery module 11 including the cell 110 in which the micro-short circuit has occurred is cooled at a temperature lower than the set temperature during normal operation during discharging. As a result, the resistance value of the parts other than the part in which the dendrite is formed in the cell 110 that caused the micro-short circuit relatively increases, so that the current density in the part in which the dendrite is formed relatively increases, and it is expected that the discharge current will concentrate in the part in which the dendrite is formed. As a result, for example, as shown in FIG. 6(b), the dendrite d is quickly dissolved and disappears or is sufficiently reduced.

[0059] The control device 30 monitors whether the above-mentioned discharging and cooling have continued for a predetermined time (S707). When the control device 30 determines that the above-mentioned discharging and cooling have continued for a predetermined time (Yes in S707), the control device 30 stops discharging, switches to charging, resumes charging (S708), and monitors whether charging has been completed (S709). Note that the control device 30 may not resume charging after the predetermined time has passed, but may instead detect a micro-short circuit again, and resume charging when a certain level of improvement in the internal state of the cell 110 is observed.

[0060] When the control device 30 determines that charging is complete after resuming charging (Yes in S709), the control device 30 lowers the upper limit current value during the next charging (S710). In other words, the cell 110 in which a micro-short circuit has occurred is considered to be prone to a micro-short circuit occurring again, and by keeping the upper limit current value during charging low, the recurrence of a micro-short circuit in the cell 110 is prevented.

[0061] As described above, according to this embodiment, if a micro-short circuit is detected in a cell 110 of a battery module 11 while the battery pack 10 is being charged, the charging is temporarily stopped and the surface pressure is reduced before discharging. This causes the discharge current to concentrate in the portion of the cell 110 where the dendrite that causes the micro-short circuit has formed, thereby quickly dissolving the dendrite and eliminating or sufficiently reducing the micro-short circuit.

[0062] In the above example, the pressure control and the temperature control for the battery module 11 when a micro-short circuit of a cell is detected are described separately, but this is not limited to the above, and the pressure control and the temperature control may be performed simultaneously.

[0063] The above-described embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be embodied in various forms without departing from the spirit of the present invention.

[0064] For example, in the methods disclosed herein, steps, operations, or functions may be performed in parallel or in a different order, provided that the results are consistent. The steps, operations, and functions described are provided merely as examples, and some of the steps, operations, and functions may be omitted or combined into one, or other steps, operations, or functions may be added, without departing from the spirit of the invention.

[0065] In addition, although various embodiments are disclosed in this specification, specific features (technical matters) in one embodiment can be added to or replaced with specific features in other embodiments, with appropriate modifications, and such forms are also included in the spirit of the present invention. [Explanation of symbols]

[0066] 1. All-solid-state battery system 10. Battery pack 11…Battery module 110…Cell 111…Covering part 120…Retaining plate 130...Pressure mechanism 131...Pantograph jack 132...Motor 12…Sensor 12a...Temperature sensor 12b…Voltage sensor 12c…Current sensor 20…Load 30...Control device 31...Charge / discharge control unit 32...Micro-short circuit detection section 33...Pressure control section 35...Temperature control unit RC…Charging device N: Negative electrode SE…Solid electrolyte layer P…Positive electrode d…Dendrite

Claims

1. An all-solid-state battery system including a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode, a pressure mechanism for applying pressure to the battery module at a predetermined surface pressure equal to or lower than a predetermined upper pressure limit; a micro-short circuit detection unit that detects a micro-short circuit in a cell of the battery module; A control device that controls charging and discharging of the battery module, when the micro-short circuit is detected, the control device controls the discharging of the battery module for a predetermined time, and controls the pressurizing mechanism to apply a surface pressure to the battery module lower than the predetermined surface pressure during the discharging. All-solid-state battery system.

2. the micro-short circuit detection unit determines whether or not the micro-short circuit has been detected during the charging of the battery module; The control device stops the charging and performs the discharging when the micro-short circuit is detected. The all-solid-state battery system according to claim 1 .

3. the micro-short circuit detection unit determines that the micro-short circuit has been detected when a rise in a voltage value of the battery module per unit time is equal to or less than a predetermined reference value during the charging of the battery module with a current of a predetermined charging current value. The all-solid-state battery system according to claim 2 .

4. the micro short circuit detection unit determines that the micro short circuit has been detected when an impedance measured for the battery module is equal to or less than a predetermined reference value. The all-solid-state battery system according to claim 2 .

5. the control device controls the discharging of the battery module so that a current of a maximum allowable current value defined by design flows through the battery module; The all-solid-state battery system according to claim 2 .

6. the control device controls the pressurizing mechanism such that the surface pressure becomes lower as the SOC of the battery module at the time of starting the discharge becomes higher. The all-solid-state battery system according to claim 2 .

7. the control device controls the pressurizing mechanism to apply pressure at a first surface pressure lower than the predetermined surface pressure when the SOC of the battery module at the time when the discharge is started is equal to or higher than a first threshold value. The all-solid-state battery system according to claim 6 .

8. the control device controls the pressurizing mechanism to apply pressure at a second surface pressure lower than the predetermined surface pressure and higher than the first surface pressure when the SOC of the battery module is not equal to or higher than the first threshold value. The all-solid-state battery system according to claim 7 .

9. The control device lowers the predetermined upper limit pressurization value after the predetermined time has elapsed. The all-solid-state battery system according to claim 2 .

10. The battery module further includes a temperature control device for controlling a temperature of the battery module. When the micro-short circuit is detected, the control device controls the discharging of the battery module for a predetermined time, and controls the temperature adjustment device during the discharging so that the temperature of the battery module becomes lower than a currently set temperature. The all-solid-state battery system according to claim 2 .

11. The negative electrode is made of a metal compound containing at least lithium, The all-solid-state battery system according to claim 2 .

12. An all-solid-state battery system including a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode, a micro-short circuit detection unit that detects a micro-short circuit in a cell of the battery module; a temperature control device for controlling the temperature of the battery module to a predetermined set temperature; A control device that controls charging and discharging of the battery module, When the micro-short circuit is detected, the control device controls the discharging of the battery module for a predetermined time, and controls the temperature adjustment device during the discharging so that the temperature of the battery module becomes lower than a currently set temperature. All-solid-state battery system.

13. A method for controlling a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode, comprising: controlling a pressure mechanism to apply pressure to the battery module at a predetermined surface pressure equal to or lower than a predetermined upper pressure limit; detecting a micro-short circuit in a cell of the battery module based on a measurement signal output from a sensor while the battery module is being charged; When the micro-short circuit is detected, the charging of the battery module is stopped and the battery module is discharged. The discharging step includes: controlling the pressurizing mechanism so as to pressurize the battery module with a surface pressure lower than the predetermined surface pressure; A method for controlling a battery module.

14. A method for controlling a battery module composed of a plurality of cells using a solid electrolyte layer between a positive electrode and a negative electrode, comprising: Controlling a temperature regulator to set the temperature of the battery module to a predetermined set temperature; detecting a micro-short circuit in a cell of the battery module based on a measurement signal output from a sensor while the battery module is being charged; When the micro-short circuit is detected, the charging of the battery module is stopped and the battery module is discharged. The discharging step includes: controlling the temperature adjustment device to set the temperature of the battery module to a temperature lower than the current predetermined set temperature; A method for controlling a battery module.

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