Battery control system and battery control method

Abstract

A battery control system 1 that controls a solid-state battery including a battery cell 21 having a solid electrolyte and a negative electrode containing lithium includes: a measurement means for measuring a surface pressure distribution on a main surface of the battery cell 21 from an actual measured value or an estimated value of the surface pressure distribution; and a control means for controlling a charge / discharge current, which is a charge current and / or a discharge current of the solid battery. The control means determines the charge / discharge current according to an upper limit surface pressure difference, which is a difference between the measured value of the surface pressure distribution measured by the measurement means and an upper limit surface pressure of the battery cell 21, and a lower limit surface pressure difference, which is a difference between the measured value of the surface pressure distribution measured by the measurement means and a lower limit surface pressure of the battery cell 21.

Description

[Technical Field]

[0001] The present invention relates to a battery control system and a battery control method. [Background technology]

[0002] A battery system is known that determines whether high-rate deterioration due to charging or discharging of a lithium secondary battery may occur based on the surface pressure at the center and end of an electrode body housed in the lithium secondary battery (see Patent Document 1). The battery system described in Patent Document 1 limits the input or output current to the secondary battery when it is determined that an increase in resistance due to charging and / or discharging of the secondary battery is occurring based on a first pressure at the center of the electrode body and a second pressure at the end of the electrode body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-122907 Summary of the Invention [Problem to be solved by the invention]

[0004] In a solid-state battery using a negative electrode containing lithium, it is necessary to control the charge / discharge current of the solid-state battery so that the surface pressure of the battery cell included in the solid-state battery does not fall below a lower limit. However, the above-mentioned conventional system does not limit the current so that the pressure of the electrode body does not fall below a lower limit, so it cannot be applied to a system for controlling the charge / discharge current of a solid-state battery. say There is a problem.

[0005] The problem to be solved by the present invention is to provide a battery control system and a battery control method that can control the charge / discharge current of a solid-state battery so that the surface pressure of the battery cells included in the solid-state battery does not fall below a lower limit value. [Means for solving the problem]

[0006] The present invention is directed to the distribution of surface pressure on the main surface of a battery cell. an upper limit surface pressure difference, which is the difference between the maximum surface pressure and the upper limit surface pressure of the battery cell, is kept equal to or less than a difference threshold, or a lower limit surface pressure difference, which is the difference between the minimum surface pressure of the surface pressure distribution and the lower limit surface pressure of the battery cell, is kept equal to or less than the difference threshold, Solid-state battery charging current and discharge current at least The above problem is solved by determining either one of the currents. [Effects of the Invention]

[0007] According to the present invention, the charge / discharge current of the solid-state battery can be controlled so that the surface pressure of the battery cells included in the solid-state battery does not fall below a lower limit value. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a battery control system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the battery cell. [Figure 3] FIG. 3 is a graph showing the characteristics of the amount of lithium creep and the cell resistance with respect to the surface pressure of the battery cell. [Figure 4] FIG. 4 is a graph showing the SOC characteristics, surface pressure characteristics, and charging current characteristics of a battery cell. [Figure 5] FIG. 5 is a graph showing the temperature distribution characteristics, charging current characteristics, thickness difference / lithium transfer amount characteristics, and surface pressure characteristics of the battery cell. [Figure 6] FIG. 6 is a flowchart showing the steps of a battery control method according to an embodiment of the present invention. [Figure 7] FIG. 7 is a graph showing the characteristics of the upper and lower limit surface pressures relative to the SOC of the battery cell, and the characteristics of the upper and lower limit surface pressures relative to the cell temperature. [Figure 8] FIG. 8 is a flowchart showing the procedure of a battery control method according to a modified embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart showing the procedure of a battery control method according to a modified embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1, the battery control system 1 includes a controller 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, a DC-DC converter 14, a surface pressure distribution measuring instrument 15, a pressure application mechanism 16, and a bus bar 17. The controller 10 in this embodiment corresponds to an example of the "control means" in the present invention, the surface pressure distribution measuring instrument 15 corresponds to an example of the "measurement means" in the present invention, and the pressure application mechanism 16 corresponds to an example of the "pressure application means" in the present invention.

[0010] The controller 10 is a battery control unit (BCU). The controller 10 is configured with a memory such as a ROM or RAM, and a processor such as a CPU. The controller 10 manages the state of the battery module 2 based on the detected voltage detected by the voltage sensor 11, the detected current detected by the current sensor 12, the detected temperature detected by the temperature sensor 13, and the measured values ​​measured by the surface pressure distribution measuring instrument 15. The controller 10 also controls the charge / discharge current for charging or discharging the battery module 2. The charge / discharge current is the charging current of the battery module 2. and at least one of the discharge current is.

[0011] The voltage sensor 11 is a sensor for detecting the voltage between the terminals of the battery module 2. The voltage sensor 11 is connected between the wiring connected to the positive and negative electrodes of the battery module 2. The current sensor 12 is a sensor for detecting the input / output current of the battery module 2. The current sensor 12 is connected to the wiring connected to the positive or negative electrode of the battery module 2. The temperature sensor 13 is provided in the battery module 2. The temperature sensor 13 is a sensor for detecting the temperature of the battery module 2.

[0012] The DCDC converter 14 is a power conversion device that converts the voltage input from the battery module 2 to a predetermined voltage and outputs power to a load such as a motor. The DCDC converter 14 is also a power conversion device that converts the voltage input from a charging device to a predetermined voltage and outputs power to the battery module 2. This DCDC converter 14 is controlled by the controller 10. The battery module 2 is connected to the input side of the DCDC converter 14, and a load is connected to the output side of the DCDC converter 14. The load is, for example, a power grid including a motor inverter. A charging device may be connected to the output side of the DCDC converter 14.

[0013] The surface pressure distribution measuring instrument 15 measures the surface pressure distribution on the main surfaces of the battery cells 21 included in the battery module 2. The measurements of the surface pressure distribution measuring instrument 15 are actual measurements of the surface pressure distribution. The surface pressure distribution measuring instrument 15 is provided along the main surfaces of the battery cells 21. The surface pressure distribution measuring instrument 15 may include a pressure sensor or the like. The surface pressure distribution measuring instrument 15 may measure the maximum surface pressure value, which is the highest pressure, and the minimum surface pressure value, which is the lowest pressure, among the pressures on the main surfaces of the battery cells 21. The surface pressure distribution measuring instrument 15 may measure the pressure over the entire surface of the main surface of the battery cell 21, or may measure the pressure at at least one measurement point on the main surface of the battery cell 21. The maximum surface pressure and minimum surface pressure values ​​of the surface pressure distribution may be calculated by arithmetic processing in the controller 10 from the measured values ​​of the surface pressure distribution measuring instrument 15. For example, if the surface pressure distribution on the main surface of the battery cell 21 is modeled using a mathematical formula, the controller 10 may acquire the measured values ​​at the measurement points from the surface pressure distribution measuring instrument 15 and calculate the maximum surface pressure and minimum surface pressure values ​​of the surface pressure distribution using the mathematical formula for the modeled surface pressure distribution.

[0014] The pressure application mechanism 16 applies pressure to the battery module 2 by pressing the battery module 2 in the stacking direction of the battery cells 21 included in the battery module 2. 16The battery module 2 has multiple cell pressure plates. The cell pressure plates are provided on the top and bottom surfaces of the battery module 2, and are also provided inside the battery module 2. The cell pressure plates provided on the top and bottom surfaces of the battery module 2 are end plates that sandwich the stack of battery cells 21 from the stacking direction of the battery cells 21 and apply pressure to the battery cells 21. The cell pressure plates provided inside the battery module 2 are installed between the multiple battery cells 21 and are members that can absorb displacement due to charging and discharging of the battery module 2, and are made of, for example, an elastic material. The pressure application mechanism 16 has cell fixing plates that fix the multiple battery cells 21 in a pack structure. The pressure application mechanism 16 also has a mechanism that changes the distance between the cell fixing plates and the pressure plates. The pressure application mechanism 16 changes the distance between the cell fixing plates and the pressure plates based on control commands from the controller 10, thereby changing the pressure applied to the battery cells 21.

[0015] The battery module 2 is a solid-state battery and is electrically connected to a charging device. The charging device connected to the battery cells 21 is a device for charging the battery module 2 mounted on, for example, an electric vehicle or a hybrid vehicle. Charging the mounted battery module 2 is performed by removing the charging cable from the charging device, attaching the charging gun at the end of the charging cable to the connector of the vehicle's charging port, and then operating the charging start switch. The controller 10 manages the state of charge (SOC) of the battery cells 21 included in the battery module 2, and controls the DC-DC converter 14 and the charging device so that the state of charge of the battery module 2 reaches a target state of charge.

[0016] As described above, the battery module 2 is electrically connected to a load such as a motor. The load is a device that operates using the power of the battery module 2, such as a motor that serves as a driving source for the vehicle, or auxiliary devices such as an air conditioner or lights. The battery module 2 is discharged under the control of the controller 10 in response to a system request or an external power request. The system request is of, corresponds to a command from an on-board computer such as an ECU. Regarding an external power request, for example, when an external device such as a mobile terminal commands an air conditioner to operate by timer setting before the vehicle starts to run so that the interior temperature of the vehicle is appropriate when the vehicle starts to run, the command from the external device corresponds to an external power request.

[0017] The battery module 2 installed in an electric vehicle or a hybrid vehicle may also be used for Vehicle Grid Integration (VGI). VGI is a technology in which an electric vehicle or a hybrid vehicle equipped with a battery module 2 is connected to a power grid, and the power stored in the battery module 2 is supplied to the power grid (load) via the power grid.

[0018] The battery cells 21 included in the battery module 2 have at least a positive electrode, a solid electrolyte, and a negative electrode. The positive electrode contains at least a positive electrode active material capable of absorbing and releasing alkali metals such as lithium (Li), sodium (Na), or potassium (K), and contains a positive electrode active material containing sulfur, although this is not particularly limited. As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used. The negative electrode may contain lithium, for example, lithium metal or a lithium alloy. The battery cells 21 are sealed with an exterior member in a state where a tab is connected to a laminated body having a positive electrode, a solid electrolyte, and a negative electrode. The battery cells 21 are formed in a flat shape. In addition, the stacked plurality of battery cells 21 teeth , and are connected to each other by bus bars 17. FIG. 2 is a plan view of a battery cell 21. Multiple battery cells 21 are stacked in the y direction, and the surface along the xz plane is the main surface of the battery cell 21 and corresponds to the stacking surface. In the battery cell 21 shown in FIG. 2, tabs protrude from both sides, but a structure in which they protrude from only one side is also acceptable. Furthermore, the tabs may protrude from the short sides of the main surface of the battery cell 21 as shown in FIG. 2, or may protrude from the long sides.

[0019] Next, the surface pressure of the battery cells 21 will be described with reference to Fig. 3. Fig. 3 is a graph (graph a) showing the characteristics of the amount of lithium creep versus surface pressure, and a graph (graph b) showing the characteristics of cell resistance versus surface pressure, with the thickness of the battery cells 21 kept constant. As shown in graph a, the higher the surface pressure, the greater the amount of creep. For example, if the surface pressure of the battery cells 21 increases during charging of the battery module 2 and the amount of creep increases too much, dendrites may form. to This increases the possibility of short circuiting. th_H , Lower limit surface pressure: P th_L The standard value (criteria: C) for specifying the above is determined in advance, and the characteristics of the surface pressure - creep amount (graph A) and the standard value (C) are of The surface pressure corresponding to the intersection is the upper limit surface pressure (P th_H ) is preset. If the surface pressure of the battery cell 21 exceeds the upper limit surface pressure, the possibility of a short circuit increases. th_H ) is the upper limit of the surface pressure that is allowed for the battery cell 21. th_H ) is a threshold value that sets the possibility of a short circuit, which changes depending on the surface pressure, to a predetermined value or less, and is set depending on the performance of the battery cell 21.

[0020] Furthermore, in solid-state batteries that use lithium for the negative electrode, it is necessary to observe not only the upper limit of surface pressure but also the lower limit of surface pressure. As shown in graph b, the lower the surface pressure, the higher the cell resistance (DCR: direct current resistance). For example, if the surface pressure of the battery cell 21 decreases and the cell resistance increases while the battery module 2 is being charged, the charging current will be lower relative to the charging voltage applied to the battery cell 21, resulting in a longer charging time. Furthermore, if the cell resistance increases while the battery module 2 is being discharged, the current supplied to the load will decrease, and it may not be possible to ensure the current required to operate the load. Therefore, the surface pressure corresponding to the intersection of the surface pressure - cell resistance (DCR) characteristic (graph b) and the reference value (C) is the lower limit of surface pressure (P th_L ) is set in advance. In other words, the lower limit surface pressure (P th_L ) is the lower limit of the surface pressure that is allowed for the battery cell 21. th_L ) is the cell resistance that changes depending on the surface pressure. valueThis is a threshold value that is determined based on external factors of the battery cell 21, such as the charging time allowed for charging the battery module 2 and the operating current of the connected load.

[0021] Next, we will explain the current control during charging and discharging by the controller 10. In the following explanation, we will mainly explain the control during charging of the battery module 2, but the discharge control of the battery module 2 is similar to the charge control, and the controller 10 determines the discharge current of the battery module 2 and controls the discharge of the battery module 2 in the same way as the method for determining the charge current.

[0022] When the controller 10 receives a command to start charging the battery module 2, it acquires the measured value of the surface pressure distribution measured by the surface pressure distribution measuring instrument 15. The surface pressure distribution measuring instrument 15 measures the measured value (actual measured value) of the surface pressure distribution of the battery module 2 at a predetermined cycle, and the controller 10 acquires the measured value of the surface pressure distribution from the surface pressure distribution measuring instrument 15 while the battery module 2 is being charged.

[0023] The controller 10 receives the measured value of the surface pressure distribution and the battery cell 21 Upper limit surface pressure (P th_H The controller 10 calculates the upper limit surface pressure difference by taking the difference between the measured surface pressure distribution and the lower limit surface pressure (P th_L ) to calculate the lower limit surface pressure difference.

[0024] Furthermore, when the maximum and minimum surface pressure values ​​of the surface pressure distribution are measured, the controller 10 calculates the maximum surface pressure value of the surface pressure distribution and the upper limit surface pressure (P th_H ) and calculate the upper limit surface pressure difference, and the minimum surface pressure value of the surface pressure distribution. battery cell 21 Lower limit surface pressure (P th_L ) to calculate the lower limit surface pressure difference.

[0025] The controller 10 then determines the charge / discharge current according to the upper limit surface pressure difference and the lower limit surface pressure difference. Specifically, the controller 10 determines the charge / discharge current so that the upper limit surface pressure difference and the lower limit surface pressure difference are kept below the difference threshold. As described above, the battery module 2 in this embodiment must maintain the upper limit surface pressure and the lower limit surface pressure during charging. For example, if the measured value of the surface pressure distribution of the battery cell 21 reaches the upper limit surface pressure while the battery module 2 is being charged, the controller 10 reduces the charge current. If charging continues with the charge current reduced and the pressure difference in the surface pressure distribution is alleviated, the maximum surface pressure value decreases, and the upper limit surface pressure difference becomes larger than the difference threshold. The controller 10 increases the charge current when the upper limit surface pressure difference exceeds the difference threshold. When the charge current increases, the charging reaction in the battery cell 21 is promoted, the surface pressure on the main surface of the battery cell 21 increases, and the upper limit surface pressure difference becomes equal to or smaller than the difference threshold. The controller 10 repeatedly increases the current according to the upper limit surface pressure difference while the battery module 2 is being charged, thereby determining the charging current so as to keep the upper limit surface pressure difference equal to or less than the difference threshold value.

[0026] When the measured value of the surface pressure distribution of the battery cells 21 is smaller than the lower limit surface pressure while the battery module 2 is being charged, the controller 10 reduces the charging current, and increases the charging current at the timing when the lower limit surface pressure difference becomes larger than the difference threshold. Also, when the upper limit surface pressure difference and the lower limit surface pressure difference differ due to the surface pressure distribution of the battery cells 21 while the battery module 2 is being charged, the controller 10 reduces the charging current when the smaller surface pressure difference between the upper limit surface pressure difference and the lower limit surface pressure difference reaches the difference threshold. Then, after reducing the charging current, the controller 10 increases the charging / discharging current when the smaller surface pressure difference becomes larger than the difference threshold. Note that the difference threshold may be a value equal to or greater than 0. For example, when the difference threshold is set to zero or a value close to zero, the controller 10 determines whether the surface pressure distribution of the battery cells 21 is at the surface pressure limit (upper limit surface pressure: P th_H , Lower limit surface pressure: P th_L ), the maximum surface pressure of the battery cell 21 is set to a high state (upper limit surface pressure P th_H When the minimum surface pressure is low (lower limit surface pressure P th_LDetermine the charging current that will keep the battery at a constant temperature (close to 1000 saturation).

[0027] Here, the relationship between the surface pressure distribution of the battery cells 21 and the charging current will be described with reference to Fig. 4. In Fig. 4, (a) shows the SOC characteristics, (b) shows the surface pressure characteristics, and (c) shows the charging current (C rate) characteristics. The horizontal axis of each graph represents time. Graph (a) shows the characteristics when the battery module 2 is charged using the charging control of this embodiment, and graph (b) shows the characteristics when the battery module 2 is charged using the charging control of the comparative example. In the charging control of the comparative example, when the measured surface pressure of the battery cells 21 reaches the upper limit surface pressure, the charging current is reduced, and thereafter, the battery module 2 is charged while maintaining the reduced charging current.

[0028] The battery module 2 has a structure in which multiple battery cells 21 are stacked. The central portion of each battery cell 21 is insulated by the other battery cells 21 adjacent to it on the top and bottom. On the other hand, heat escapes more easily from the tabs of the battery cells 21 than from the central portion. Therefore, when the battery cells 21 are being charged, high-temperature and low-temperature areas are generated on the main surfaces of the battery cells 21. In the high-temperature areas, the charging reaction is promoted, the amount of lithium deposition increases, and the surface pressure increases. Furthermore, as shown in graph b of Figure 3, when the surface pressure increases, the cell resistance decreases, which further promotes the charging reaction and further increases the surface pressure. In this way, differences in temperature on the main surfaces of the battery cells 21 cause differences in surface pressure (the difference between the maximum surface pressure and the minimum surface pressure) in the surface pressure distribution.

[0029] When the battery module 2 is charged and the measured value of the surface pressure distribution of the battery cells 21 reaches the upper limit surface pressure, the controller 10 reduces the charging current. aAt this point, the measured value of the surface pressure distribution of the battery cell 21 reaches the upper limit surface pressure, so the controller 10 reduces the charging current. If charging control is continued with the charging current reduced, as in the comparative example, the difference in surface pressure between the high surface pressure area and the low surface pressure area gradually decreases and converges to a constant surface pressure (see graph b in Figure 4(b)). Also, in the comparative example, charging control is continued with the current reduced, so it takes a long time for the SOC of the battery module 2 to reach the target SOC. In other words, as shown in graph b in Figure 4(a), the charging time is longer in the comparative example.

[0030] In this embodiment, time t a At this point, when the measured value of the surface pressure distribution of the battery cells 21 reaches the upper limit surface pressure, the controller 10 temporarily reduces the charging current and performs charging control. If charging of the battery module 2 continues with the charging current reduced, the deposited lithium becomes thicker as charging progresses. As described above, differences in temperature (temperature distribution) on the main surfaces of the battery cells 21 cause differences in surface pressure in the surface pressure distribution. Pressure applied to areas with high surface pressure causes lithium to wet and spread in a direction along the main surfaces. In other words, lithium moves from areas with high surface pressure to areas with low surface pressure. In this way, the amount of lithium moving in the surface direction increases, which alleviates the surface pressure distribution.

[0031] Then, when the surface pressure distribution is alleviated and at least one difference between the upper limit surface pressure difference and the lower limit surface pressure difference becomes equal to or less than the difference threshold, the controller 10 increases the charging current. In other words, when the surface pressure distribution portion is alleviated and the measured value of the surface pressure distribution of the battery cell 21 becomes smaller than the upper limit surface pressure, the controller 10 increases the charging current. Then, charging control continues with the charging current increased, and when the measured value of the surface pressure distribution of the battery cell 21 reaches the upper limit surface pressure, the controller 10 reduces the charging current once to alleviate the surface pressure distribution, and then increases the charging current again (hereinafter, this type of control is also referred to as high current control). As shown in graph a in Figure 4(c), at time t а From time t bDuring this time, the controller 10 performs high current control. When the maximum surface pressure value in the surface pressure distribution of the battery cells 21 reaches the upper limit surface pressure during charging of the battery module 2, the controller 10 performs high current control, and when the minimum surface pressure value in the surface pressure distribution of the battery cells 21 reaches the lower limit surface pressure, the controller 10 performs high current control. The more the lithium thickness increases with charging, the greater the amount of lithium movement. Therefore, as charging continues and the SOC increases, the surface pressure distribution becomes more easily alleviated, allowing the battery module 2 to be charged with a higher charging current.

[0032] Due to the high current control by the controller 10, the surface pressure on the main surface of the battery cell 21 exhibits the characteristics shown in graph a in FIG. 4(b), and the maximum surface pressure in the surface pressure distribution of the battery cell 21 is maintained at a high value within a range that does not exceed the upper limit surface pressure, and the minimum surface pressure in the surface pressure distribution of the battery cell 21 is maintained at a low value within a range that does not fall below the lower limit surface pressure. In addition, the charging current exhibits the characteristics shown in graph a in FIG. 4(c), and the charging current gradually increases. Then, at time t b At this point, when the voltage of the battery module 2 reaches the upper limit voltage, the controller 10 gradually reduces the current while maintaining the charging voltage of the battery module 2 at the upper limit voltage (CV current control). In this embodiment, the battery module 2 is charged using high current control, so the charging time is shorter than in the comparative example (see graph a in FIG. 4(a)). Note that FIG. 4 shows the characteristics during charging and explains the effect of shortening the charging time, but by applying the same control logic as high current control to the discharging side, it is possible to increase the discharge current.

[0033] Next, with reference to FIGS. 2 and 5, the temperature distribution, charging current, thickness difference, lithium migration amount, and surface pressure distribution in the battery cell 21 will be described. In the following description, the center of the main surface of the battery cell 21 will be referred to as A1, and the end portion will be referred to as A2. During charging of the battery module 2, the temperature of the center portion A1 of the battery cell 21 is more likely to rise than the temperature of the end portion A2. Therefore, as shown in FIG. 5(a), the temperature distribution of the battery cell 21 widens and the temperature difference increases over the course of charging. The center portion (A1) of the main surface of the battery cell 21 has a higher temperature and a larger charging current than the end portion (A2). As shown in FIG. 5(b), the charging current at the center portion (A1) follows the characteristics of graph a, while the charging current at the end portion (A2) follows the characteristics of graph b. Because the charging current is higher in the center portion (A1) and the charging reaction is promoted, the thickness due to lithium deposition is greater than that at the end portion (A2). Furthermore, the difference in thickness due to lithium deposition between the center portion (A1) and the end portion (A2) increases over the course of charging (see graph a in FIG. 5(c)). Furthermore, the amount of creep increases in the thicker portion of the battery cell 21 (center portion (A1)), and lithium migrates from the center portion (A1) toward the end portion (A2) due to lithium deformation. As shown in graph b in FIG. 5(c), the amount of lithium migration increases over the course of charging. Furthermore, the surface pressure at the center portion (A1) follows the characteristics shown in graph a in FIG. 5(d), while the surface pressure at the end portion (A2) follows the characteristics shown in graph b in FIG. 5(d).

[0034] In this way, while the battery module 2 is being charged, a temperature distribution occurs within the surface of the battery cell 21, forming high-temperature and low-temperature areas. This temperature distribution then forms a surface pressure distribution on the main surface of the battery cell 21, forming thicker and thinner areas. In the thicker areas, more pressure is applied, so the lithium spreads in the direction along the main surface of the battery cell 21. As the charging of the battery cell 21 progresses, the amount of lithium movement increases, and therefore the higher the SOC, the greater the amount of lithium movement, and the more relaxed the surface pressure distribution. Furthermore, in this embodiment, when the surface pressure distribution is relaxed, the charging current is increased by the amount of relaxation. As a result, when the battery module 2 is being charged, the upper and lower limit surface pressures (P th_H , P th_L ) while shortening charging time.

[0035] The following describes a battery control method for the battery module 2. Fig. 6 is a flowchart showing the steps of the battery control method of this embodiment. The battery control method of this embodiment is repeatedly executed at predetermined intervals when the battery module 2 is being charged.

[0036] First, in step S1, the controller 10 receives the surface pressure distribution from the surface pressure distribution measuring device 15 on the main surface of the battery cell 21. Okeru A measured value of the surface pressure distribution is acquired. In step S2, the controller 10 acquires the SOC of the battery cell 21, the temperature of the battery cell 21, and the deterioration state (degree of deterioration) of the battery cell 21. The SOC of the battery cell 21 may be calculated, for example, by integrating the current of the battery cell 21. The temperature of the battery cell 21 may be acquired from the temperature sensor 13. The controller 10 may calculate the temperature distribution on the main surface of the battery cell 21 from the temperature detected by the temperature sensor 13 using a calculation model of the temperature distribution of the battery cell 21. The deterioration state of the battery cell 21 may be calculated, for example, from the ratio of the current battery capacity to the initial battery capacity of the battery cell 21. Note that the above calculation method of the SOC and deterioration state of the battery cell 21 is merely an example, and other methods may be used.

[0037] In step S3, the controller 10 compares the measured surface pressure distribution and the battery cell 21 Upper limit surface pressure (P th_H ) and the difference (Upper limit pressure (P th_H )" - "Measured surface pressure distribution") to calculate the upper limit surface pressure difference, and compare the measured surface pressure distribution with the battery cell 21 Lower limit surface pressure (P th_L ) (Measured surface pressure distribution value) - Lower limit surface pressure (P th_L When the maximum and minimum values ​​of the surface pressure distribution are measured as the measured values, the controller 10 calculates the lower limit surface pressure difference by taking the maximum and minimum values ​​of the surface pressure (P th_H ) and the difference (Upper limit pressure (P th_H )" - "Maximum surface pressure"), calculate the upper limit surface pressure difference, and calculate the minimum surface pressure and lower limit surface pressure (P th_L ) ("Minimum surface pressure value" - "Lower limit surface pressure (P th_LThe controller 10 may calculate the lower limit surface pressure difference from the upper limit surface pressure difference and the lower limit surface pressure difference. E Specifically, the difference ("Upper limit surface pressure (P th_H )" - "Measured surface pressure distribution") and the difference ("Measured surface pressure distribution" - "Lower limit surface pressure (P th_L If the surface pressure required current value (I E On the other hand, the difference (Upper limit pressure (P th_H )" - "Measured surface pressure distribution" is less than 0, or the difference ("Measured surface pressure distribution" - "Lower limit surface pressure (P th_L If the surface pressure required current value (I E ) to reduce the surface pressure required current value (I E ) is the maximum current required by the surface pressure, and is the current value determined by high current control.

[0038] The controller 10 determines the upper limit surface pressure (P th_H ) and lower limit surface pressure (P th_L 7(a) and (b) show the upper and lower limit surface pressures (P th_H , P th_L ) characteristics of the battery cell 21, and FIG. 7(c) shows the upper and lower limit surface pressures (P th_H , P th_L 7(a) to 7(c), the solid line indicates the characteristic before deterioration, and the dotted line indicates the characteristic after deterioration. th_H , P th_L ) characteristics and upper and lower limit surface pressure (P th_H , P th_L The characteristics of the battery cell 21 change depending on the battery material, etc. The controller 10 determines the upper and lower limit surface pressures (P th_H , P th_LFor example, when the battery cell 21 has characteristics such that when the SOC is high or the temperature of the battery cell 21 is high, the amount of lithium migration in the direction along the main surface of the battery cell 21 increases, increasing the possibility of a short circuit. In this case, the upper limit surface pressure (P th_H The controller 10 adjusts the upper limit surface pressure (P) according to the SOC or temperature so that the upper limit surface pressure (P th_H ) is corrected (see FIGS. 7(a) and 7(c)). For example, when the battery cell 21 has characteristics such that the cell resistance increases due to contraction of the positive electrode active material when the SOC is high, the lower limit surface pressure (P th_L The controller 10 adjusts the lower limit surface pressure (P th_L ) (see FIG. 7(a)). When the degree of deterioration of the battery cell 21 is high, the controller 10 corrects the upper limit surface pressure (P th_H ) and the lower limit surface pressure (P th_L ) is increased, the upper and lower limit surface pressure (P th_H , P th_L ) is corrected.

[0039] The correction direction may be changed as appropriate depending on the battery materials (positive and negative electrode active materials, etc.) used in the battery cells 21 and the battery structures of the battery cells 21 and the battery module 2. For example, as shown in FIG. 7(b), the higher the SOC, the lower the upper limit surface pressure (P th_H ) is large, and the lower limit surface pressure (P th_L The controller 10 sets the upper and lower limit surface pressures (P th_H , P th_L ) may be corrected by combining the SOC, temperature, and deterioration state of the battery cell 21. th_H , P th_L ) may be corrected, and all elements may be used to calculate the upper and lower limit surface pressures (P th_H , P th_L ) may be corrected.

[0040] In step S4, the controller 10 acquires other control request currents determined by factors other than the surface pressure of the battery cell 21. The other control request currents include the system request current (I F ), and the protection requirement current (I G , I H ) are included. The system required current is the maximum current of the system that charges or discharges the battery module 2. The required current of the charging system corresponds to the maximum current that can be output from the charging device. The required current of the discharging system corresponds to the maximum current value determined by the operating state of the load, such as a motor, connected to the battery module 2. The protection required current (I G ) is the maximum current (I G ) and the protection requirement current (I H ) is to prevent the battery cell 21 from being overcharged or overdischarged. 21 The maximum current (I H ) When the charging voltage of the battery module 2 reaches the upper limit voltage, the controller 10 switches from high current control to CV current control, but the current value in the CV current control is the maximum current (I H ) can be adjusted.

[0041] In step S5, the controller 10 determines the surface pressure required current value (I E ),system request Current (I F ), and protection demand current (I G , I H ), the lowest current is determined as the actual current for charging and discharging the battery module 2, and is determined as the command current for making the charging current of the battery module 2 the actual current. E ),system request Current (I F ), and protection demand current (I G , I H ) to determine the command current.

[0042] In step S6, if the command current is zero and the measured value of the surface pressure distribution is less than the predetermined surface pressure distribution value, the controller 10 terminates the charging control. On the other hand, if the command current is not zero or if the measured value of the surface pressure distribution is equal to or greater than the predetermined value, the controller 10 transmits a control command for the command current (actual current command value) to the charging device and executes charging control from step S1. The predetermined value of the surface pressure distribution used to determine the termination of charging control may be set according to the variation in the measured value of the surface pressure distribution. In the control flow of the above-described battery control method, even if the command current is zero, if the measured value of the surface pressure distribution is equal to or greater than the predetermined surface pressure distribution value, charging control is continued to reduce the variation in the surface pressure and prepare for the next charge / discharge event. The condition of the surface pressure distribution may be omitted from the control flow of step S6.

[0043] As described above, the battery control system and the battery control method of this embodiment measure the surface pressure distribution from the actual measurement value of the surface pressure distribution on the main surface of the battery cell 21, and calculate the upper limit surface pressure difference, which is the difference between the measured surface pressure distribution and the upper limit surface pressure of the battery cell 21, and the lower limit surface pressure, which is the difference between the measured surface pressure distribution and the lower limit surface pressure of the battery cell 21. Lower limit surface pressure difference The charging current of the battery module 2 (solid-state battery) is and at least one of the discharge current This determines the charge / discharge current such that the surface pressure of the battery cell 21 is lower than the lower limit surface pressure (P th_L ) during charging of the battery module 2, the upper and lower limit surface pressures (P th_H , P th_L ) while shortening charging time.

[0044] The battery control system of this embodiment also determines the upper limit surface pressure (P th_H ) and the lower limit surface pressure (P th_L ) is corrected. This allows the upper and lower limit surface pressures (P th_H , P th_L ) while shortening charging time.

[0045] In addition, the battery control system of this embodiment is Lower limit surface pressure difference The charge / discharge current (required surface pressure current value I E (corresponding to the system requirement), the system requirement current and the battery cell 21 The lowest current among the protection requirement currents determined by the protection requirements is set as the actual current for charging and discharging the battery module 2. This satisfies the current conditions determined by requirements other than the surface pressure, and the upper and lower limit surface pressures (P th_H , P th_L ) can be shortened as long as the charging time does not exceed this limit.

[0046] In addition, the battery control system of this embodiment reduces the charge / discharge current when the smaller of the upper limit surface pressure difference and the lower limit surface pressure difference reaches the difference threshold, and after reducing the charge / discharge current, increases the charge / discharge current when the surface pressure difference becomes larger than the difference threshold. As a result, when charging the battery module 2, the upper and lower limit surface pressures (P th_H , P th_L ) while shortening charging time.

[0047] Furthermore, the battery control system of this embodiment determines the charge / discharge current so that the upper limit surface pressure difference, which is the difference between the maximum surface pressure value and the upper limit surface pressure in the surface pressure distribution, is kept below the difference threshold value during charging / discharging of the battery module 2, or so that the lower limit surface pressure difference, which is the difference between the minimum surface pressure value and the lower limit surface pressure in the surface pressure distribution, is kept below the difference threshold value. As a result, when charging the battery module 2, the upper and lower limit surface pressures (P th_H , P th_L ) while shortening charging time.

[0048] In this embodiment, the surface pressure distribution measuring instrument 15 may not be provided, and the controller 10 may measure the surface pressure distribution from an estimated value of the surface pressure distribution on the main surface of the battery cell 21. In other words, the controller 10 may estimate the surface pressure distribution using calculation processing such as a calculation model, and use the estimated value that is the calculation result as the measured surface pressure distribution, rather than using the actual measurement value of the surface pressure distribution measuring instrument 15 as the measured surface pressure distribution. A method for estimating the surface pressure distribution will be described below.

[0049] The controller 10 calculates an estimated value of the surface pressure distribution from the measured value of the current distribution on the main surface of the battery cell 21, the measured value of the temperature distribution on the main surface of the battery cell 21, and the SOC of the battery cell 21. The current distribution may be calculated from the resistance distribution within the battery cell 21. The resistance distribution may be measured using a resistance distribution resistor device such as a shunt resistor. The resistance distribution resistor device is provided on the outermost layer of the stacked multiple battery cells 21. During charging and discharging, the controller 10 obtains the detected value of the input voltage or output voltage of the battery module 2 from the voltage sensor 11, and calculates the current distribution on the main surface of the battery cell 21 from the voltage of the battery module 2 and the resistance distribution measured by the resistance distribution resistor device. The current distribution corresponds to the distribution of lithium deposition amount.

[0050] The controller 10 is Sa 1 The controller 10 acquires the detected temperature of the battery cell 21 from the temperature sensor 13 and calculates the temperature distribution of the battery cell 21 from a calculation model that models the temperature distribution of the battery cell 21 and the detected temperature. Note that the controller 10 may measure the temperature distribution using a temperature distribution measuring device that measures the temperature distribution instead of the temperature sensor 13. The controller 10 calculates the SOC of the battery cell 21 from the detected voltage of the voltage sensor 11 or the integrated value of the charge / discharge current. The controller 10 can estimate the surface pressure distribution by calculating the amount of lithium migration in the direction along the main surface of the battery cell 21 from the current distribution, temperature distribution, and SOC. As shown in FIG. 5, the amount of lithium migration is correlated with the temperature distribution and current distribution on the main surface of the battery cell 21, and the higher the SOC, the greater the amount of lithium migration. Furthermore, the surface pressure distribution on the main surface of the battery cell 21 can be determined from the amount of lithium migration. Therefore, for example, a calculation formula for calculating the amount of lithium migration (or surface pressure distribution) can be modeled for the temperature distribution, current distribution, and SOC, and the controller 10 can estimate the surface pressure distribution from the modeled formula. This allows the controller 10 to measure the surface pressure distribution from the estimated value of the surface pressure distribution, eliminating the need for the surface pressure distribution measuring device 15 and achieving cost reduction.

[0051] The controller 10 may estimate the surface pressure distribution using the following estimation method. The controller 10 may calculate the current distribution on the main surface of the battery cell 21 from the measured value of the temperature distribution on the main surface of the battery cell 21 and the battery resistance characteristics of the battery cell 21, and calculate the estimated value of the surface pressure distribution from the calculated value of the current distribution, the measured value of the temperature distribution, and the SOC of the battery cell 21. The battery resistance characteristics of the battery cell 21 are indicated by a map (DCR map) that indicates the correlation between battery temperature and resistance. The controller 10 has the DCR map and may calculate the resistance distribution characteristics relative to the measured value of the temperature distribution by referring to the DCR map. The controller 10 then calculates the current distribution on the main surface of the battery cell 21 from the measured value of the temperature distribution of the battery cell 21 and the battery resistance characteristics of the battery cell 21. Furthermore, the controller 10 can estimate the surface pressure distribution by calculating the amount of lithium migration along the main surface of the battery cell 21 from the current distribution, temperature distribution, and SOC. The method of estimating the surface pressure distribution is the same as described above. This allows the controller 10 to measure the surface pressure distribution from the estimated value of the surface pressure distribution. This eliminates the need for a resistance distribution measuring device, thereby achieving cost reduction. The controller 10 in this embodiment corresponds to an example of the "measuring means" in the present invention.

[0052] The controller 10 may estimate the surface pressure distribution by the following estimation method: The controller 10 calculates the amount of heat generated and / or the amount of heat dissipated from the battery cell 21 from the battery resistance characteristics of the battery cell 21, various battery characteristics determined by the shape and / or material of the battery cell 21, the internal temperature of the battery cell 21, and the environmental temperature, and compares the calculated amount of heat generated and / or the amount of heat dissipated from the battery cell 21 with the 21The estimated value of the surface pressure distribution may be calculated from the SOC. The battery characteristics are characteristics indicating the thermal conductivity of the battery cell 21, which depends on the active material and tab material contained in the battery cell 21, the shape of the battery cell 21, etc. The internal temperature of the battery cell 21 corresponds to the temperature detected by the temperature sensor 13. The ambient temperature is the temperature around the battery module 2 and may be detected by a sensor. Formulas for calculating the amount of heat generated and / or the amount of heat dissipation are modeled for the battery resistance characteristics, the battery characteristics, the internal temperature of the battery cell 21, and the ambient temperature, and the controller 10 calculates the amount of heat generated and / or the amount of heat dissipation from the modeled formula. The controller 10 then calculates the temperature distribution on the main surface of the battery cell 21 from the calculated amount of heat generated and / or the amount of heat dissipation, and calculates the estimated value of the surface pressure distribution from the current distribution and SOC. This allows the controller 10 to measure the surface pressure distribution from the estimated value of the surface pressure distribution. This eliminates the need for a temperature distribution measurement device, thereby achieving cost reduction.

[0053] As a modification of this embodiment, the battery control system 1 may perform high current control by adjusting the pressure applied to the battery cells 21 based on the magnitude relationship between the upper limit surface pressure difference and the lower limit surface pressure difference during charging and discharging of the battery module 2. FIG. 8 is a flowchart showing the steps of a battery control method according to a modification of this embodiment. The battery control method of the modification is repeatedly executed at predetermined intervals during charging of the battery module 2. The following describes control during charging of the battery module 2, but the control flow during charging can also be applied to discharge control of the battery module 2 as appropriate.

[0054] The control flow from steps S11 to S15 is the same as the control flow from steps S1 to S5 described above, and therefore a description thereof will be omitted. In step S16, the controller 10 calculates the upper limit surface pressure difference and the lower limit surface pressure difference, and determines whether or not the current can be increased by adjusting the pressure depending on the magnitude of the difference between the upper limit surface pressure difference and the lower limit surface pressure difference. If the upper limit surface pressure difference and the lower limit surface pressure difference are different, the charging current is determined according to the smaller difference. In a modified example, if there is a difference between the upper limit surface pressure difference and the lower limit surface pressure difference, the pressure is adjusted to reduce the difference between the upper limit surface pressure difference and the lower limit surface pressure difference. On the other hand, if the difference between the upper limit surface pressure difference and the lower limit surface pressure difference is small, i.e., if the upper limit surface pressure difference and the lower limit surface pressure difference are approximately the same, the current increase due to pressure adjustment is small. Therefore, for example, if the difference between the upper limit surface pressure difference and the lower limit surface pressure difference is equal to or greater than a predetermined value, the controller 10 determines that it is possible to increase the current by adjusting the pressure, and if the difference between the upper limit surface pressure difference and the lower limit surface pressure difference is less than the predetermined value, the controller 10 determines that it is not possible to increase the current by adjusting the pressure.

[0055] If it is determined that the current can be increased by adjusting the pressure, then in step S17 the controller 10 determines whether the upper limit surface pressure difference is greater than the lower limit surface pressure difference. If the upper limit surface pressure difference is greater than the lower limit surface pressure difference, then in step S18 the controller 10 outputs a command to the pressure application mechanism 16 to increase the pressure applied to the battery cell 21. On the other hand, if the upper limit surface pressure difference is smaller than the lower limit surface pressure difference, then in step S19 the controller 10 outputs a command to the pressure application mechanism 16 to decrease the pressure applied to the battery cell 21. After adjusting the pressure, the controller 10 executes charge control from step S11. Then, after adjusting the pressure, the controller 10 executes the control flow of step S13, thereby further increasing the charge / discharge current of the battery cell 21.

[0056] If it is determined in the determination process of step S16 that the current cannot be increased by adjusting the pressure, the controller 10 executes the control flow of step S20. The control flow of step S20 has the same content as the control flow of step S6 described above, and therefore a description thereof will be omitted.

[0057] That is, the battery control system 1 according to the modified example of this embodiment increases the pressure applied to the battery cells 21 when the upper limit surface pressure difference is greater than the lower limit surface pressure difference, and decreases the pressure applied to the battery cells 21 when the upper limit surface pressure difference is smaller than the lower limit surface pressure difference. This relaxes the restrictions on charging and discharging required by the upper and lower limit surface pressures, and shortens the charging time.

[0058] As a modification of this embodiment, the battery control system 1 may perform high current control by adjusting the temperature of the battery cells 21 based on the temperature distribution on the main surfaces of the battery cells 21 during charging and discharging of the battery module 2. FIG. 9 is a flowchart showing the steps of a battery control method according to a modification of this embodiment. The battery control method according to the modification is repeatedly executed at predetermined intervals during charging of the battery module 2. The battery control system 1 also includes a temperature regulator for cooling the battery cells 21. The temperature regulator can individually cool the inside of the battery cells 21 and the tabs of the battery cells 21. For example, when the internal temperature of the battery cells 21 is high, the amount of cooling of the inside of the battery cells 21 (particularly the center) can be increased and the amount of cooling of the tabs of the battery cells 21 can be decreased. On the other hand, when the temperature near the tabs of the battery cells 21 is high, the amount of cooling of the inside of the battery cells 21 (particularly the center) can be decreased and the amount of cooling of the tabs of the battery cells 21 can be increased. The temperature regulator corresponds to a "temperature adjusting means" that adjusts the temperature of the battery cells 21.

[0059] 9 is a flowchart showing the steps of a battery control method according to a modified example of this embodiment. The modified battery control method is repeatedly executed at predetermined intervals during charging of the battery module 2. In the following explanation, control during charging of the battery module 2 will be described, but the control flow during charging can also be applied to discharge control of the battery module 2 as appropriate.

[0060] The control flow from steps S21 to S25 is the same as the control flow from steps S1 to S5 described above, and therefore the description thereof will be omitted. 21 The upper limit temperature protection current is determined by the upper limit temperature, and the upper limit surface pressure difference is Lower limit surface pressure differenceThe upper limit temperature protection current is the maximum current (protection required current: I G ) corresponds to the upper limit surface pressure difference and Lower limit surface pressure difference The charge / discharge current determined by the surface pressure required current value (I E The upper limit temperature protection current determined by the upper limit temperature of the battery cell 21 corresponds to the upper limit surface pressure difference. Lower limit surface pressure difference If the charge / discharge current is higher than the charge / discharge current determined according to the temperature of the battery cell, the controller 10 determines that the current can be increased by adjusting the temperature. 21 The upper limit temperature protection current is determined by the upper limit surface pressure difference. Lower limit surface pressure difference If the charge / discharge current is equal to or less than the charge / discharge current determined according to the temperature regulation, the controller 10 determines that the current cannot be increased by temperature regulation.

[0061] If it is determined that the current can be increased by adjusting the pressure, then in step S27, the controller 10 outputs a command to the temperature regulator to adjust the temperature of the battery cell 21. 21 When the temperature at the center of the battery cell 21 is the highest, the controller 10 outputs a control command to the temperature regulator so that the amount of cooling inside the battery cell 21 increases. 21 If the temperature near the tab is the highest, the controller 10 outputs a control command to the temperature regulator to increase the amount of cooling near the tab of the battery cell 21. After adjusting the temperature, the controller 10 executes charge control from step S21. By adjusting the temperature of the battery cell 21, the upper limit temperature protection current determined by the upper limit temperature of the battery cell 21 increases.

[0062] If it is determined in the determination process of step S26 that the current cannot be increased by temperature adjustment, the controller 10 executes the control flow of step S28. The control flow of step S28 has the same content as the control flow of step S6 described above, and therefore a description thereof will be omitted.

[0063] That is, the battery control system 1 according to the modified example of this embodiment controls the temperature regulator to reduce the temperature difference in the temperature distribution on the main surface of the battery cell 21 when the upper limit temperature protection current determined by the upper limit temperature of the battery cell 21 is higher than the charge / discharge current determined according to the upper limit surface pressure difference and the lower limit surface pressure difference. This reduces the charging time. [Explanation of symbols]

[0064] 1. Battery control system 10...Controller 11...Voltage sensor 12...Current sensor 13...Temperature sensor 14...DCDC converter 15…Surface pressure distribution measuring device 16...Pressure application mechanism 2...Battery module 21...Battery cell

Claims

1. A battery control system for controlling a solid-state battery including a battery cell having a solid electrolyte and a negative electrode containing lithium, a measuring means for measuring the surface pressure distribution on the main surface of the battery cell from actual measured values ​​or estimated values ​​of the surface pressure distribution; a control means for controlling a charge / discharge current, which is at least one of a charge current and a discharge current of the solid-state battery; The control means a battery control system that determines the charge / discharge current so that an upper limit surface pressure difference, which is the difference between the maximum surface pressure value of the surface pressure distribution measured by the measurement means and the upper limit surface pressure of the battery cell, is kept equal to or less than a difference threshold, or so that a lower limit surface pressure difference, which is the difference between the minimum surface pressure value of the surface pressure distribution measured by the measurement means and the lower limit surface pressure of the battery cell, is kept equal to or less than the difference threshold.

2. 2. The battery control system according to claim 1, The measuring means a battery control system that calculates the estimated value from a measurement value of a current distribution on the main surface of the battery cell, a measurement value of a temperature distribution on the main surface of the battery cell, and an SOC of the battery cell;

3. 3. The battery control system according to claim 1 or 2, The measuring means calculating a current distribution on the main surface of the battery cell from a measured value of a temperature distribution on the main surface of the battery cell and a battery resistance characteristic of the battery cell; A battery control system that calculates the estimated value from the calculated value of the current distribution, the measured value of the temperature distribution, and the SOC of the battery cell.

4. 3. The battery control system according to claim 1 or 2, The measuring means calculating the amount of heat generated and / or the amount of heat dissipated from the battery cell from the battery resistance characteristics of the battery cell, battery characteristics determined by the shape and / or material of the battery cell, the internal temperature of the battery cell, and the environmental temperature; A battery control system that calculates the estimated value from the calculated heat generation amount and / or heat dissipation amount and an SOC of the battery cell.

5. 3. The battery control system according to claim 1 or 2, The control means corrects the upper limit surface pressure and the lower limit surface pressure in accordance with at least one element of the SOC of the battery cell, the temperature of the battery cell, and the degree of deterioration of the battery cell.

6. 3. The battery control system according to claim 1 or 2, The control means a battery control system that sets the actual current for charging and discharging the solid-state battery to the lowest current among the charging and discharging current determined according to the upper limit surface pressure difference and the lower limit surface pressure difference, the system required current determined by system requirements, and the protection required current determined by protection requirements for the battery cell.

7. 3. The battery control system according to claim 1, a pressure applying means for applying pressure to the solid-state battery; the measuring means measures a maximum surface pressure value and a minimum surface pressure value of the surface pressure distribution, The control means When the upper limit surface pressure difference, which is the difference between the maximum surface pressure value of the surface pressure distribution and the upper limit surface pressure, is larger than the lower limit surface pressure difference, which is the difference between the minimum surface pressure value of the surface pressure distribution and the lower limit surface pressure, increasing the pressure applied to the battery cell; When the upper limit surface pressure difference is smaller than the lower limit surface pressure difference, the battery control system reduces the pressure applied to the battery cell.

8. 3. The battery control system according to claim 1, a temperature adjusting means for adjusting the temperature of the battery cell; The control means a battery control system that controls the temperature adjustment means so that a temperature difference in a temperature distribution on the main surface of the battery cell is reduced when an upper limit temperature protection current determined by an upper limit temperature of the battery cell is higher than the charge / discharge current determined according to the upper limit surface pressure difference and the lower limit surface pressure difference.

9. 3. The battery control system according to claim 1 or 2, The control means When the smaller of the upper limit surface pressure difference and the lower limit surface pressure difference reaches a difference threshold, the charge / discharge current is reduced; a battery control system that increases the charge / discharge current when the surface pressure difference becomes greater than the difference threshold after the charge / discharge current is reduced;

10. A battery control method for controlling a solid-state battery including a battery cell having a solid electrolyte and a negative electrode containing lithium, comprising: measuring the surface pressure distribution on the main surface of the battery cell from actual measured values ​​or estimated values ​​of the surface pressure distribution; a battery control method for determining a charge / discharge current, which is at least one of a charge current and a discharge current, of the solid-state battery, so that an upper limit surface pressure difference, which is the difference between the maximum surface pressure value of the measured surface pressure distribution and the upper limit surface pressure of the battery cell, is kept equal to or less than a difference threshold, or so that a lower limit surface pressure difference, which is the difference between the minimum surface pressure value of the measured surface pressure distribution and the lower limit surface pressure of the battery cell, is kept equal to or less than the difference threshold.

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