Battery system

Abstract

In order to mitigate the risk of a short circuit in a battery cell, this battery system comprises: a battery module (11M) in which stacked are battery cells (11) in which the thickness of an electrode fluctuates during charging and discharging; a pressurizing mechanism (18) that pressurizes the battery module (11M) in the stacking direction; a thickness detector (13) that detects the electrode thickness in the battery cells; a temperature detector (12) that detects the temperature of the battery cells; and a controller (17) that controls the pressurizing force of the pressurizing mechanism. The controller controls the pressurizing force of the pressurizing mechanism on the basis of the detected thickness and temperature of the battery cells.

Description

Battery System

[0001] The present invention relates to a battery system.

[0002] One such battery system is known as an all-solid-state battery control system (Patent Document 1), which includes an all-solid-state battery including a solid electrolyte, a housing having a space for accommodating the all-solid-state battery, a fluid filled in the space of the housing, a pressure device that applies pressure to the all-solid-state battery via the fluid, and a control unit that controls the magnitude of the pressure applied to the all-solid-state battery by the pressure device based on the temperature of the all-solid-state battery and the SOC (State of Charge) of the all-solid-state battery. According to this all-solid-state battery control system, the magnitude of the pressure applied to the all-solid-state battery is controlled based on the temperature of the all-solid-state battery and the SOC of the all-solid-state battery, thereby stably maintaining ionic conductivity in the solid electrolyte.

[0003] Japanese Patent Application Laid-Open No. 2022-163356

[0004] However, even if the SOC is the same, the thickness of the electrodes may vary due to individual differences in the design specifications or manufacturing process of the battery. The thicker the electrode, the greater the creep strain displacement of the electrode, and the thinner the electrode, the smaller the creep strain displacement. Therefore, controlling the magnitude of the applied pressure based on the SOC as in the conventional technology described above cannot control the creep strain displacement of the electrode. Furthermore, the problem of increased creep strain displacement of the electrode increases the risk of short-circuiting of the battery cell.

[0005] The problem to be solved by the present invention is to provide a battery system that can reduce the risk of short-circuiting of battery cells.

[0006] The present invention solves the above problem by detecting the electrode thickness and temperature of the battery cells in a battery module in which battery cells whose electrode thickness fluctuates during charging and discharging are stacked, and controlling the pressure applied to the battery cells based on the detected battery cell thickness and temperature.

[0007] According to the present invention, the risk of short-circuiting of battery cells can be reduced.

[0008] Fig. 1 is a block diagram showing one embodiment of a battery system according to the present invention. Fig. 2 is a cross-sectional view showing an example of a battery module and a pressurizing mechanism included in the battery system of Fig. 1. Fig. 3 is a cross-sectional view of a battery cell for explaining one problem to be solved by the present invention. Fig. 4 is a cross-sectional view of a battery cell for explaining another problem to be solved by the present invention. Fig. 5 is a flowchart showing an example of control executed by the controller of Fig. 1. Fig. 6 is a flowchart showing another example of control executed by the controller of Fig. 1. Fig. 7 is a flowchart showing yet another example of control executed by the controller of Fig. 1.

[0009] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram showing one embodiment of a battery system according to the present invention, and Fig. 2 is a cross-sectional view showing an example of a battery module 11M and a pressure mechanism 18 included in the battery system 1 of Fig. 1. The battery system 1 of this embodiment includes a battery module 11M in which battery cells 11 are stacked, a pressure mechanism 18 that presses the battery module 11M in the stacking direction X of the battery cells 11, a thickness detector 13 that detects the thickness of the electrodes of the battery cells 11, a temperature detector 12 that detects the temperature of the battery cells 11, and a controller 17 that controls the pressure force of the pressure mechanism 18. In addition, the battery system 1 of this embodiment includes a current detector 15 that detects the current flowing through the battery cells 11, a voltage detector 16 that detects the voltage of the battery cells 11, and a charger 19 that charges the battery cells 11.

[0010] The battery cells 11 included in the battery system 1 of this embodiment are not particularly limited as long as the thickness of the electrodes changes during charging and discharging. Such battery cells 11 are not particularly limited, but may be, for example, all-solid-state batteries or semi-solid-state batteries. An all-solid-state battery is a rechargeable secondary battery that uses a solid electrolyte as an electrolyte, and also includes a solid electrolyte containing a small amount of liquid material. A semi-solid-state battery is a rechargeable secondary battery that uses a gel electrolyte as an electrolyte.

[0011] The battery cell 11 of this embodiment is not particularly limited, but may be, for example, a battery cell 11 containing metallic lithium or a metallic lithium alloy as the negative electrode active material. The battery cell 11 of this embodiment can be configured by housing a laminated body, in which a positive electrode layer, a negative electrode layer, an electrolyte layer, a positive electrode current collector, and a negative electrode current collector are stacked, in an exterior member such as a laminate film, and by leading out a positive electrode terminal and a negative electrode terminal from the exterior member.

[0012] The battery module 11M of this embodiment is used by connecting multiple battery cells 11 (six in the example shown in Figure 2) in series and / or parallel, and connecting another battery module or a load to the positive terminal on one side of the connected battery cells and the negative terminal on the other side.

[0013] Battery cells 11 used under pressure, such as all-solid-state or semi-solid-state batteries, require a pressure treatment to bond the interfaces between the solid or semi-solid electrolyte layer and the positive and negative electrode layers. Therefore, the pressure mechanism 18 of this embodiment presses the battery module 11M in the stacking direction X of the battery cell 11. As shown in FIG. 2 , the pressure mechanism 18 of this embodiment includes a pair of fixed platens 181 and 182, a movable platen 183, and a pressure actuator 184. The movable platen 183 is moved back and forth relative to the fixed platen 182 by the pressure actuator 184 to apply or remove a desired surface pressure to the battery module 11M placed between the pair of fixed platens 181 and 182. The pressure actuator 184 is composed of a fluid pressure cylinder, a pantograph jack, a feed screw mechanism, or the like, and is driven by a control signal from the controller 17, thereby controlling the surface pressure applied to the main surfaces of the battery cells 11. The illustrated pressure mechanism 18 is an example of a pressure mechanism included in the battery system according to the present invention, and is not intended to be limited to this type of pressure mechanism 18. Any pressure mechanism 18 may be used as long as it can apply a predetermined range of surface pressure to the main surface of the battery cell 11 .

[0014] The pressure mechanism 18 of this embodiment is provided with a pressure detector 14, which detects the pressure applied from the pressure mechanism 18 to the battery cells 11. If necessary, as shown in Figure 2, elastic members 185 may be provided between the battery cells 11 that make up the battery module 11M so that uniform surface pressure is applied to the interfaces between the electrolyte layer and the positive electrode layer and the negative electrode layer of the battery cells 11.

[0015] The temperature detector 12 of this embodiment detects the temperature of each battery cell 11, and the controller 17 reads the temperature and calculates the creep strain rate (described below). The temperature detector 12 of this embodiment is not particularly limited, and either a contact-type temperature sensor or a non-contact-type temperature sensor may be used. Examples of contact-type temperature sensors include thermocouples, platinum resistance thermometers, thermistor thermometers, bimetal thermometers, liquid-filled thermometers, and mercury thermometers. Examples of non-contact-type temperature sensors include radiation thermometers, which measure temperature by measuring infrared rays emitted from an object. In the battery system 1 of this embodiment, the pressure mechanism 18 is controlled primarily based on the temperature of the negative electrode layer. Therefore, it is desirable to position the detection terminal of the temperature detector 12 as close as possible to accurately measure the temperature of the negative electrode layer of the battery cell 11.

[0016] The thickness detector 13 of this embodiment is not particularly limited as long as it can detect the thickness of the electrodes of the battery cells 11. For example, the integrated electrical capacity may be calculated from the current value and time flowing through the electrodes during charging, and the electrode thickness may be estimated from this integrated electrical capacity. However, when estimating the electrode thickness from the integrated electrical capacity, variations in the integrated electrical capacity may occur due to individual differences in the electrode layer during manufacturing. For this reason, it is more desirable to physically measure the electrode thickness using a strain gauge or thickness measuring device. The thickness detector 13 of this embodiment is provided to detect the thickness of the negative electrode layer, but it may also be provided to all battery cells 11 constituting the battery module 11M, or to a specific battery cell 11. When thickness detectors 13 are provided to multiple battery cells 11, the detected thickness may be the average or median of the thicknesses. The thickness detector 13 of this embodiment, for example, detects the thickness of the battery cells 11, and the controller 17 subtracts the thickness of components other than the electrodes from the detected thickness of the battery cells 11 to determine the electrode thickness.

[0017] The current detector 15 of this embodiment detects the current flowing through each battery cell 11 that constitutes the battery module 11M. The voltage detector 16 of this embodiment detects the voltage between the positive and negative terminals of each battery cell 11 that constitutes the battery module 11M.

[0018] The controller 17 of this embodiment is configured by a microcomputer including, for example, a CPU, ROM, RAM, etc., and has a creep strain displacement rate calculator 171 and a pressure force calculator 172, and controls the pressure mechanism 18 and the charger 19. Specifically, the creep strain displacement rate calculator 171 of this embodiment calculates the temperature T of the battery cell 11 detected by the temperature detector 12, the pressure force σ detected by the pressure force detector 14, and the thickness l of the electrode (negative electrode layer) of the battery cell 11 detected by the thickness detector 13. ０ The detected temperature T of the battery cell 11, the detected pressure σ, and the detected thickness l are read out. ０ From this, the creep strain displacement rate dΔl / dt is calculated.

[0019] The pressure calculator 172 of this embodiment determines a pressure that makes the creep strain displacement rate dΔl / dt calculated by the creep strain displacement rate calculator 171 equal to or less than a predetermined threshold value or within a predetermined range centered on the threshold value, and then controls the pressurizing mechanism 18 with the determined pressure.

[0020] FIG. 3 is a cross-sectional view of a battery cell 11 illustrating one problem to be solved by the present invention. The battery cell 11 shown in the figure is an example of an all-solid-state battery in which a solid electrolyte layer 113 is provided between an anode layer 111, a cathode layer 112, and a cathode layer 113, the solid electrolyte layer 113 being composed of lithium metal or the like. In this type of battery cell 11, when surface pressure is applied to the anode layer 111, the cathode layer 112, and the solid electrolyte layer 113 in the direction indicated by the arrows during use, such as charging and discharging, the lithium metal constituting the anode layer 111 undergoes creep deformation, and as shown enlarged in the figure, the lithium metal advances along the pores in the solid electrolyte layer 113. In particular, when the electrode is thick, the creep strain displacement becomes large, increasing the risk of short-circuiting with the cathode layer 112.

[0021] Figure 4 is a cross-sectional view of a battery cell 11 to explain another problem to be solved by the present invention. Like the battery cell 11 shown in Figure 3, the battery cell 11 shown in Figure 4 is an all-solid-state battery having a solid electrolyte layer 113 between an anode layer 111 made of lithium metal or the like and a cathode layer 112. In this type of battery cell 11, when surface pressure is applied to the anode layer 111, cathode layer 112, and solid electrolyte layer 113 in the direction indicated by the arrows during use, such as charging and discharging, or when the battery is at rest, the lithium metal constituting the anode layer 111 undergoes creep deformation, causing the outer periphery of the anode layer 111 to protrude beyond the cathode layer 112, as shown in the right diagram of Figure 4. This protruding portion of the anode layer 111 is less susceptible to electrochemical reactions, resulting in a loss of battery capacity during charging and discharging.

[0022] When a surface pressure is applied to the battery cell 11 having the negative electrode layer 111, the positive electrode layer 112, and the solid electrolyte layer 113 shown in FIGS. 3 and 4, the creep strain displacement Δl [m] of the metal (e.g., lithium metal) constituting the negative electrode layer 111 is calculated by multiplying the thickness of the negative electrode layer 111 by 1. ０ [m], and creep strain is ε. It can be expressed as:

[0023] The creep strain ε can be expressed as ε = (dε / dt) × Δt, where dε / dt is the creep strain rate (the value obtained by differentiating the creep strain ε with respect to time t). Here, the following relational expression holds when dε / dt is the creep strain rate, Ac is the material-specific creep parameter, σ is the stress (here, the surface pressure applied to the battery cell 11), m is the stress exponent, Qc is the activation energy for dislocation movement, T is the temperature, and R is the Avogadro constant.

[0024] Differentiating both sides of the above equation 1 with respect to time t, we get By substituting Equation 2 for dε / dt in Table 3, the creep strain displacement rate dΔl / dt can be expressed by the following Equation 4.

[0025] In the above formula 4, the material-specific creep parameter Ac, stress exponent m, activation energy Qc of dislocation movement, and Avogadro's constant R are constants, so the creep strain displacement rate dΔl / dt is a function of the stress σ (surface pressure applied to the battery cell 11), the temperature T, and the electrode thickness l ０ Here, the creep strain displacement rate dΔl / dt on the left side of Equation 4 is the displacement rate (m / sec) caused by creep strain, and is a variable related to displacement [m] and time [sec]. In the battery system 1 of this embodiment, the variables on the right side, stress σ, temperature T, and electrode thickness l are adjusted so that the creep strain displacement rate dΔl / dt on the left side of Equation 4 is as small as possible. ０ and control.

[0026] Next, the control performed by the controller 17 of this embodiment will be described.

[0027] <First Control Example> Fig. 5 is a flowchart showing an example of control executed by the controller 17 in Fig. 1. In the illustrated control example, the controller 17 controls the pressure (σ in Equation 4) of the pressure mechanism 18 so that the creep strain displacement rate dΔl / dt of the metal constituting the electrodes becomes equal to or less than a predetermined threshold value when the battery module 11M is charged or discharged.

[0028] First, in step S1, the controller 17 determines whether charging has started. The determination of whether charging has started is made by the charge end determiner 173 based on the current and / or voltage detected by the current detector 15 and / or voltage detector 16. If it is determined in step S1 that charging has started, the process proceeds to step S2; otherwise, step S1 is repeated.

[0029] In step S2, the controller 17 compares the temperature T of the battery cell 11 detected by the temperature detector 12 with the thickness l of the electrode (e.g., the negative electrode layer 111) detected by the thickness detector 13. ０ Then, in step S3, the detected temperature T of the battery cell 11, the detected pressure σ, and the detected thickness l are read out. ０ is substituted into Equation 4 to calculate the creep strain displacement rate dΔl / dt.

[0030] In step S4, a threshold value of the applied pressure at which the creep strain displacement rate dΔl / dt becomes a predetermined threshold value is determined, and in the following step S5, it is determined whether the applied pressure detected by the applied pressure detector 14 is equal to or less than the threshold value. If the applied pressure detected by the applied pressure detector 14 is equal to or less than the threshold value, the process proceeds to step S6, where the current applied pressure is maintained. On the other hand, if the applied pressure detected by the applied pressure detector 14 is not equal to or less than the threshold value in step S5, the process proceeds to step S7, where the current applied pressure is reduced by a predetermined amount.

[0031] In step S8, it is determined whether charging has been completed. The determination of whether to start charging is made by charge completion determiner 173 based on the current and / or voltage detected by current detector 15 and / or voltage detector 16. If it is determined in step S8 that charging has been completed, the process ends; otherwise, the process returns to step S2.

[0032] <Second Control Example> Fig. 6 is a flowchart showing another example of control executed by the controller 17 in Fig. 1. In the illustrated control example, the controller 17 controls the pressure (σ in Equation 4) of the pressure mechanism 18 so that the creep strain displacement rate dΔl / dt of the metal constituting the electrodes falls within a predetermined range centered on a predetermined threshold value during charging or discharging of the battery module 11M.

[0033] First, in step S11, the controller 17 determines whether charging has started. The determination of whether charging has started is made by the charge end determiner 173 based on the current and / or voltage detected by the current detector 15 and / or the voltage detector 16. If it is determined in step S11 that charging has started, the process proceeds to step S12; otherwise, step S11 is repeated.

[0034] In step S12, the controller 17 compares the temperature T of the battery cell 11 detected by the temperature detector 12 with the thickness l of the electrode (for example, the negative electrode layer 111) detected by the thickness detector 13. ０ Then, in step S13, the detected temperature T of the battery cell 11, the detected pressure σ, and the detected thickness l are read out. ０is substituted into Equation 4 to calculate the creep strain displacement rate dΔl / dt.

[0035] In step S14, a threshold range (lower and upper thresholds) of the applied pressure within which the creep strain displacement rate dΔl / dt becomes a predetermined threshold is determined, and in the following step S15, it is determined whether the applied pressure detected by the applied pressure detector 14 is within the threshold range. If the applied pressure detected by the applied pressure detector 14 is within the threshold range, the process proceeds to step S17, where the current applied pressure is maintained. On the other hand, if the applied pressure detected by the applied pressure detector 14 is less than the lower threshold in step S15, the process proceeds to step S16, where the current applied pressure is increased by a predetermined amount. If the applied pressure detected by the applied pressure detector 14 exceeds the upper threshold in step S15, the process proceeds to step S18, where the current applied pressure is decreased by a predetermined amount.

[0036] In step S19, it is determined whether charging has been completed. The determination of whether to start charging is made by charge completion determiner 173 based on the current and / or voltage detected by current detector 15 and / or voltage detector 16. If it is determined in step S19 that charging has been completed, the process ends; otherwise, the process returns to step S12.

[0037] <<Third Control Example>> Fig. 7 is a flowchart showing yet another example of control executed by the controller 17 in Fig. 1. In the illustrated control example, the controller 17 controls the pressure (σ in Equation 4) of the pressure mechanism 18 so that the creep strain displacement rate dΔl / dt of the metal constituting the electrodes becomes equal to or less than a predetermined threshold value when the battery module 11M is left stationary (not being charged or discharged).

[0038] First, in step S31, the controller 17 determines whether or not there is no current flowing, i.e., whether or not charging or discharging is being performed. The determination of whether or not there is no current flowing is made by the charge completion determiner 173 based on the current and / or voltage detected by the current detector 15 and / or the voltage detector 16. If it is determined in step S31 that there is no current flowing, the process proceeds to step S32; otherwise, step S31 is repeated.

[0039] In step S32, the controller 17 reads the temperature T of the battery cell 11 detected by the temperature detector 12, the thickness l0 of the electrode (for example, the negative electrode layer 111) detected by the thickness detector 13, and the applied pressure σ detected by the applied pressure detector 14. Then, in step S33, the controller 17 substitutes the detected temperature T of the battery cell 11, the detected applied pressure σ, and the detected thickness l0 into Equation 4 to calculate the creep strain displacement rate dΔl / dt.

[0040] In step S34, a threshold value of the applied pressure at which the creep strain displacement rate dΔl / dt becomes a predetermined threshold value is determined, and in the following step S35, it is determined whether the applied pressure detected by the applied pressure detector 14 is equal to or less than the threshold value. If the applied pressure detected by the applied pressure detector 14 is equal to or less than the threshold value, the process proceeds to step S36, where the current applied pressure is maintained. On the other hand, if the applied pressure detected by the applied pressure detector 14 is not equal to or less than the threshold value in step S35, the process proceeds to step S37, where the current applied pressure is reduced by a predetermined amount.

[0041] In step S38, it is determined whether or not current flow (charging or discharging) has started. That is, it is determined whether or not the non-current flow period has ended. The determination of whether or not current flow has started is made by the charge end determiner 173 based on the current and / or voltage detected by the current detector 15 and / or the voltage detector 16. If it is determined in step S38 that current flow has started, the process ends; otherwise, the process returns to step S32.

[0042] <Fourth Control Example> Fig. 8 is a flowchart showing yet another example of control executed by the controller 17 in Fig. 1. In the illustrated control example, the controller 17 controls the pressure (σ in Equation 4) of the pressure mechanism 18 so that the creep strain displacement rate dΔl / dt of the metal constituting the electrodes falls within a predetermined range centered on a predetermined threshold value when the battery module 11M is left stationary (not being charged or discharged).

[0043] First, in step S41, the controller 17 determines whether charging has started. The determination of whether charging has started is made by the charge end determiner 173 based on the current and / or voltage detected by the current detector 15 and / or voltage detector 16. If it is determined in step S41 that charging has started, the process proceeds to step S42; otherwise, step S41 is repeated.

[0044] In step S42, the controller 17 compares the temperature T of the battery cell 11 detected by the temperature detector 12 with the thickness l of the electrode (for example, the negative electrode layer 111) detected by the thickness detector 13. ０ Then, in step S43, the detected temperature T of the battery cell 11, the detected pressure σ, and the detected thickness l are read out. ０ is substituted into Equation 4 to calculate the creep strain displacement rate dΔl / dt.

[0045] In step S44, a threshold range (lower and upper thresholds) of the applied pressure within which the creep strain displacement rate dΔl / dt becomes a predetermined threshold is determined, and in the following step S45, it is determined whether the applied pressure detected by the applied pressure detector 14 is within the threshold range. If the applied pressure detected by the applied pressure detector 14 is within the threshold range, the process proceeds to step S47, where the current applied pressure is maintained. On the other hand, if the applied pressure detected by the applied pressure detector 14 is less than the lower threshold in step S45, the process proceeds to step S46, where the current applied pressure is increased by a predetermined amount. If the applied pressure detected by the applied pressure detector 14 exceeds the upper threshold in step S45, the process proceeds to step S48, where the current applied pressure is decreased by a predetermined amount.

[0046] In step S49, it is determined whether charging has been completed. The determination of whether charging should be started is made by charge completion determiner 173 based on the current and / or voltage detected by current detector 15 and / or voltage detector 16. If it is determined in step S49 that charging has been completed, the process ends; otherwise, the process returns to step S42.

[0047] In the first to fourth control examples described above, it is desirable to set the predetermined threshold value relatively smaller as the electrode thickness increases and relatively larger as the electrode thickness decreases. Also, when charging the battery module 11M, it is desirable to set the predetermined threshold value relatively smaller as the applied current to the battery cell 11 increases and relatively larger as the applied current to the battery cell decreases.

[0048] As described above, the battery system 1 of this embodiment includes a battery module 11M in which battery cells 11, the electrode thickness of which fluctuates during charging and discharging, are stacked, a pressure mechanism 18 that pressurizes the battery module 11M in the stacking direction X, a thickness detector 13 that detects the thickness of the electrodes of the battery cells 11, a temperature detector 12 that detects the temperature of the battery cells 11, and a controller 17 that controls the pressure applied by the pressure mechanism 18. The controller 17 controls the pressure applied by the pressure mechanism 18 based on the detected thickness and temperature of the battery cells 11, and therefore, the creep strain rate of the electrode constituent material can be controlled, thereby reducing the risk of short-circuiting of the battery cells.

[0049] Furthermore, in the battery system 1 of this embodiment, the thickness detector 13 detects the thickness of the battery cell 11, and the controller 17 subtracts the thickness of components other than the electrodes from the detected thickness of the battery cell 11 to determine the thickness of the electrodes of the battery cell 11, thereby physically determining the actual electrode thickness of each battery cell. As a result, robustness against variations in the capacity of the battery cell 11 is improved compared to a method of estimating the electrode thickness using integrated electrical capacitance.

[0050] Furthermore, in the battery system 1 of this embodiment, the controller 17 controls the pressure of the pressure mechanism 18 so that the creep strain displacement rate of the metal constituting the electrodes is equal to or less than a predetermined threshold during charging or discharging of the battery module 11M, thereby reducing the risk of short-circuiting the battery cells 11. Furthermore, since the electrodes are prevented from protruding outward, the occurrence of capacity loss in the battery cells 11 can be reduced.

[0051] Furthermore, in the battery system 1 of this embodiment, the controller 17 controls the pressure of the pressure mechanism 18 so that the creep strain displacement rate of the metal constituting the electrode falls within a predetermined range centered on the predetermined threshold value when the battery module 11M is being charged or discharged. This not only reduces the risk of short-circuiting the battery cell 11 and the occurrence of capacity loss in the battery cell, but also improves the charging and discharging efficiency by setting a lower threshold value.

[0052] Furthermore, in the battery system 1 of this embodiment, the controller 17 controls the pressure of the pressure mechanism 18 so that the creep strain displacement rate of the metal constituting the electrodes is equal to or less than a predetermined threshold when the battery module 11M is left stationary, thereby reducing the risk of short-circuiting the battery cells 11. Furthermore, since the electrodes are prevented from protruding outward, the occurrence of capacity loss in the battery cells 11 can be reduced.

[0053] Furthermore, in the battery system 1 of this embodiment, when the battery module 11M is left stationary, the controller 17 controls the pressure of the pressure mechanism 18 so that the creep strain displacement rate of the metal constituting the electrodes falls within a predetermined range centered on the predetermined threshold value. This not only reduces the risk of short-circuiting of the battery cells 11 and the occurrence of capacity loss in the battery cells 11, but also increases the recovery force of the contact interface area between the electrodes and the electrolyte by setting a lower threshold value.

[0054] Furthermore, in the battery system 1 of this embodiment, the predetermined threshold is set relatively smaller as the temperature of the battery cell 11 increases, and set relatively larger as the temperature of the battery cell 11 decreases. When the pressure applied by the pressure mechanism 18 is the same, the higher the temperature of the battery cell 11, the greater the creep strain displacement rate of the metal constituting the electrode. Therefore, by setting the predetermined threshold relatively smaller, the risk of short-circuiting of the battery cell 11 and the occurrence of capacity loss of the battery cell 11 can be further reduced.

[0055] Furthermore, in the battery system 1 of this embodiment, the thicker the electrode, the smaller the predetermined threshold is set, and the thinner the electrode, the larger the predetermined threshold is set. When the pressure of the pressure mechanism 18 and the temperature of the battery cell 11 are the same, the thicker the electrode, the greater the creep strain displacement rate of the metal that makes up the electrode. Therefore, by making the predetermined threshold relatively small, the risk of short-circuiting the battery cell 11 and the occurrence of capacity loss in the battery cell 11 can be further reduced.

[0056] Furthermore, in the battery system 1 of this embodiment, when charging the battery module 11M, the predetermined threshold is set relatively smaller as the applied current to the battery cell 11 increases, and set relatively larger as the applied current to the battery cell 11 decreases. When the pressure force of the pressure mechanism 18, the temperature of the battery cell 11, and the electrode thickness are all the same, the greater the applied current during charging, the greater the risk of a short circuit in the battery cell 11. Therefore, by setting the predetermined threshold relatively small, the risk of a short circuit in the battery cell 11 can be further reduced.

[0057] Furthermore, in the battery system of this embodiment, lithium metal or lithium metal alloy is precipitated on the negative electrode of the battery cell during charging, which further reduces the risk of short circuiting of the battery cell 11 and the occurrence of capacity loss in the battery cell 11.

[0058] DESCRIPTION OF SYMBOLS 1...Battery system 11...Battery cell 11M...Battery module 111...Anode layer 112...Cathode layer 113...Solid electrolyte layer X...Stacking direction of battery cell 12...Temperature detector 13...Thickness detector 14...Pressure detector 15...Current detector 16...Voltage detector 17...Controller 171...Creep strain displacement rate calculator 172...Pressure calculator 173...Charging end determiner 18...Pressure mechanism 181, 182...Fixed platen 183...Movable platen 184...Pressure actuator 185...Elastic member 19...Charger

Claims

1. A battery system comprising: a battery module in which battery cells whose electrode thicknesses fluctuate during charging and discharging are stacked; a pressure mechanism that pressurizes the battery module in the stacking direction; a thickness detector that detects the thickness of the electrodes of the battery cells; a temperature detector that detects the temperature of the battery cells; and a controller that controls the pressure force of the pressure mechanism, wherein the controller controls the pressure force of the pressure mechanism based on the detected thickness and temperature of the battery cells.

2. The battery system according to claim 1, wherein the thickness detector detects the thickness of the battery cell, and the controller calculates the thickness of the electrode of the battery cell by subtracting the thickness of components other than the electrode from the detected thickness of the battery cell.

3. A battery system as described in claim 1 or 2, wherein the controller controls the pressure of the pressure mechanism so that the creep strain displacement rate of the metal constituting the electrode is below a predetermined threshold when the battery module is being charged or discharged.

4. A battery system as described in claim 3, wherein the controller controls the pressure of the pressure mechanism so that the creep strain displacement rate of the metal constituting the electrode falls within a predetermined range centered on the predetermined threshold value when the battery module is being charged or discharged.

5. A battery system as described in claim 1 or 2, wherein the controller controls the pressure of the pressure mechanism so that the creep strain displacement rate of the metal constituting the electrodes is below a predetermined threshold when the battery module is left stationary.

6. A battery system as described in claim 5, wherein the controller controls the pressure of the pressure mechanism so that the creep strain displacement rate of the metal constituting the electrodes falls within a predetermined range centered on the predetermined threshold value when the battery module is left stationary.

7. A battery system according to any one of claims 3 to 6, wherein the predetermined threshold is set relatively smaller as the temperature of the battery cell increases, and set relatively larger as the temperature of the battery cell decreases.

8. A battery system according to any one of claims 3 to 6, wherein the predetermined threshold is set relatively smaller as the thickness of the electrode increases, and set relatively larger as the thickness of the electrode decreases.

9. A battery system according to any one of claims 3 to 6, wherein, during charging of the battery module, the predetermined threshold is set relatively smaller as the applied current to the battery cell increases, and set relatively larger as the applied current to the battery cell decreases.

10. A battery system according to any one of claims 1 to 9, wherein the battery cells deposit lithium metal or lithium metal alloy on the negative electrodes during charging.

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