Manufacturing method for power storage device

Abstract

To provide a manufacturing method for a power storage device capable of raising the battery voltage (cell voltage) to a sufficient potential to dissolve foreign matter by charging during aging.SOLUTION: The manufacturing method for a power storage device includes forming a laminated body, charging a cell by applying a voltage between a positive electrode active material layer and a negative electrode active material layer via a voltage detection terminal and the current collector while aging the laminated body (S31, S41), measuring a cell voltage during charging of the cell (S31, S41), and measuring the voltage of the cell in a non-energized state while aging is continued after charging of the cell is terminated and a predetermined time has elapsed (S31, S41).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a power storage device.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2015-122160 (Patent Document 1) discloses a technique of aging a battery at a high temperature (for example, 60°C) in order to activate the battery. By performing high-temperature aging, metal foreign matter can be dissolved in the electrolyte, and metal foreign matter can be deposited in advance on the negative electrode. Further, by having an inspection process thereafter, it is possible to suppress the occurrence of an internal short circuit during battery use.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the experiments of the inventor of the present application, it has been found that not only aging the battery at a high temperature but also charging the battery during aging to increase the battery voltage promotes the dissolution of foreign matter (such as unnecessary metals). However, depending on the structure of the battery and the method of applying voltage, it may not be easy to increase the battery voltage by charging during aging. Even if the battery is charged to full charge, the battery voltage may not rise to a sufficient voltage to dissolve foreign matter. In particular, when the wiring resistance is high, the influence of IR drop becomes large, and there is a problem that the actual battery voltage becomes lower than the voltage detected during charging, and the above problems may become prominent.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a method for manufacturing a power storage device capable of raising a battery voltage (cell voltage) to a potential sufficient to dissolve foreign matter by charging during aging.

Means for Solving the Problems

[0006] According to one aspect of the present disclosure, a method for manufacturing a power storage device including a laminate is provided. The laminate includes a plurality of bipolar electrodes and a plurality of separators. Each of the plurality of bipolar electrodes has a current collector to which a voltage detection terminal is connected, a positive electrode active material layer provided on one surface of the current collector, and a negative electrode active material layer provided on the other surface of the current collector. In the laminate, a cell including a positive electrode active material layer, a separator, and a negative electrode active material layer is formed between the stacked plurality of current collectors. The method for manufacturing the power storage device includes forming a laminate, charging the cell by applying a voltage between the positive electrode active material layer and the negative electrode active material layer through the voltage detection terminal and the current collector while aging the laminate, measuring the voltage of the cell during charging of the cell, and measuring the voltage of the non-powered state of the cell while continuing aging after the charging of the cell is completed and a predetermined time has elapsed.

Advantages of the Invention

[0007] According to the present disclosure, it becomes possible to provide a method for manufacturing a power storage device capable of raising a battery voltage (cell voltage) to a potential sufficient to dissolve foreign matter by charging during aging.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated. In each of the drawings used below, among the X-axis, Y-axis, and Z-axis that are orthogonal to each other, the X-axis indicates the in-plane direction of the first surface of the battery (for example, the width direction), the Y-axis indicates the in-plane direction of the second surface of the battery (for example, the length direction), and the Z-axis indicates the thickness direction of the battery. Hereinafter, “+” is attached to the direction indicated by the arrows of the X-axis, Y-axis, and Z-axis, and “-” is attached to the opposite direction.

[0010] FIG. 1 is a diagram for explaining an overview of the method for manufacturing a power storage device according to this embodiment. Referring to FIG. 1, the manufacturing system according to this embodiment includes a control device 100, a temperature adjustment device 200, charging devices 300 and 500, and an assembling device 800. Each of the temperature adjustment device 200, the charging devices 300 and 500, and the assembling device 800 is controlled by the control device 100. The control device 100 includes one or more processors 110 and one or more storage devices 120. The storage device 120 is configured to be able to store the stored information. In addition to the program, information used in the program (for example, maps and various parameters) is stored in the storage device 120. In this embodiment, by the one or more processors 110 executing the program stored in the one or more storage devices 120, each process shown in FIG. 1 and FIG. 4 described later is executed. However, these processes may be executed only by hardware (electronic circuit) without using software.

[0011] The manufacturing method of the power storage device according to this embodiment includes each process shown by a flowchart in FIG. 1. The type of the power storage device to be manufactured is arbitrary, and for example, it may be a lithium ion secondary battery. In the flowchart, "S" means step. The manufacturing system first forms a laminate 10 shown in FIG. 2, for example, in S101.

[0012] FIG. 2 is a cross-sectional view showing the configuration of the laminate 10. Referring to FIG. 2, the laminate 10 includes a power storage portion 10a and a sealing portion 3 that seals the power storage portion 10a. The Z direction corresponds to the lamination direction. The power storage portion 10a includes a plurality of cells C arranged in the Z direction. Each of the plurality of cells C includes a negative electrode active material layer 12A, a positive electrode active material layer 12B, and a separator 13. In this embodiment, the power storage portion 10a includes 10 or more cells C. However, the number of cells C can be arbitrarily set. The number of cells C included in the power storage portion 10a may be 10 or more and less than 50, or may be 50 or more. The sealing portion 3 is formed so as to surround the power storage portion 10a. The space surrounded by the sealing portion 3 (between the cell C and the sealing portion 3) is filled with an electrolytic solution. The electrolytic solution is impregnated into the separator 13. The separator 13 may be a porous sheet.

[0013] The laminate 10 includes a plurality of electrodes (one negative terminal electrode 2A, a plurality of bipolar electrodes 1, and one positive terminal electrode 2B) laminated along the Z direction. A separator 13 is disposed between the electrodes. The laminate 10 includes a plurality of separators 13. The bipolar electrode 1 includes a current collector 11, a negative electrode active material layer 12A provided on one surface (+Z side surface) of the current collector 11, and a positive electrode active material layer 12B provided on the other surface (-Z side surface) of the current collector 11. The negative terminal electrode 2A has a configuration in which the positive electrode active material layer 12B is removed from the bipolar electrode 1. An insulating layer 19A is formed on the -Z side surface of the current collector 11 constituting the negative terminal electrode 2A. The insulating layer 19A covers the peripheral portion of the negative terminal electrode 2A and exposes the central portion of the negative terminal electrode 2A (the current collector 11 located at the -Z side end of the power storage portion 10a). The positive terminal electrode 2B has a configuration in which the negative electrode active material layer 12A is removed from the bipolar electrode 1. An insulating layer 19B is formed on the +Z side surface of the current collector 11 constituting the positive terminal electrode 2B. The insulating layer 19B covers the peripheral portion of the positive terminal electrode 2B and exposes the central portion of the positive terminal electrode 2B (the current collector 11 located at the +Z side end of the power storage portion 10a).

[0014] In this embodiment, a metal foil (for example, aluminum foil) is adopted as the current collector 11 of each electrode. Surface treatment (for example, plating treatment) may be performed on one or both surfaces of the metal foil. A voltage detection terminal 20 is connected to the current collector 11 of each electrode. In this embodiment, the voltage detection terminal 20 includes stainless steel (for example, SUS304). The electrical resistivity of the voltage detection terminal 20 is, for example, 1.0×10 -7 Ωm or more and 1.0×10 -6 Ωm or less. Stainless steel is excellent in corrosion resistance, heat resistance, and workability. However, the material of the voltage detection terminal 20 can be appropriately changed. Another metal (for example, copper) may be adopted instead of stainless steel.

[0015] The negative electrode active material layer 12A contains a negative electrode active material. The positive electrode active material layer 12B contains a positive electrode active material. In one example, the positive electrode active material is olivine-type lithium iron phosphate (LiFePO4), the negative electrode active material is a carbon-based material (e.g., graphite), and the electrolyte is a non-aqueous electrolyte (e.g., an ester-based electrolyte). However, these materials can be changed as appropriate. Another example of the positive electrode active material includes a composite oxide (such as LiCoO2, LiNiMnCoO2, etc.) containing one or more elements selected from the group consisting of manganese, titanium, nickel, cobalt, and aluminum, and lithium. Another example of the negative electrode active material includes silicon and tin. The electrolyte may be an aqueous electrolyte. Also, a gel-like or solid electrolyte may be employed instead of the electrolyte. Examples of the material constituting the separator 13 include polypropylene, polyethylene, polyester, and cellulose. The structure of the separator 13 may be a single-layer structure or a multilayer structure. The separator 13 may include, for example, a base material layer and a pair of adhesive layers, and may be adhered to the negative electrode active material layer 12A and the positive electrode active material layer 12B by the pair of adhesive layers.

[0016] In the laminate 10, cells C are formed between a plurality of stacked current collectors 11. Specifically, a cell C is formed between a certain current collector 11 (the first current collector) and the current collector 11 (the second current collector) adjacent to the first current collector. Further, a cell C is also formed between the second current collector and the current collector 11 (the third current collector) adjacent to the second current collector. In this way, the current collector 11 and the cell C are alternately arranged in the stacking direction of the laminate 10.

[0017] The sealing portion 3 includes seal layers 14, 15 disposed around each of the plurality of cells C included in the laminate 10, and the insulating layers 19A, 19B described above. Any sealing material can be employed as the material constituting the sealing portion 3. Examples of the sealing material include resin materials such as polyethylene, polypropylene, acid-modified polyethylene, or acid-modified polypropylene. The structure of the sealing portion 3 between the current collectors 11 is not limited to a two-layer structure (seal layers 14, 15), and may be a three-layer structure. The sealing portion 3 may include a spacer.

[0018] A connector 30 shown in FIG. 3 is provided for a plurality of voltage detection terminals 20 connected to the laminate 10. FIG. 3 is a diagram for explaining the structures of each of the cell C, the voltage detection terminal 20, and the connector 30. Referring to FIG. 3, the voltage detection terminal 20 is welded, for example, to the end portion on the +X side of the current collector 11. Examples of the welding method include ultrasonic welding or laser welding. In this embodiment, among the voltage detection terminals 20, the dimension (width) of the portion welded to the current collector 11 is larger than the dimension (width) of the tip portion. This makes it easier to increase the bonding area between the current collector 11 and the voltage detection terminal 20. Also, an increase in the electrical resistance near the boundary between the current collector 11 and the voltage detection terminal 20 is suppressed. However, the shape and dimensions of the voltage detection terminal 20 are not limited to those shown in FIG. 3 and can be changed as appropriate.

[0019] The connector 30 includes a resin portion 31 and a housing 32. For example, with the housing 32 for aligning the voltage detection terminals 20 attached to the tips of the voltage detection terminals 20, the resin portion 31 connecting the end face on the +X side of the laminate 10 and the housing 32 is formed by injection molding. Thereby, the connector 30 in a state joined to the laminate 10 is formed. Note that the sealing portion 3 of the laminate 10 may be reinforced by the injection molding. Also, the injection port may be reinforced by performing the injection molding after welding the injection port to the end face of the laminate 10.

[0020] Each of the plurality of cells C included in the laminate 10 functions as a battery. The cell C according to this embodiment is an LFP battery that employs lithium iron phosphate as a positive electrode active material. Lithium iron phosphate corresponds to a positive electrode active material having a normal operating potential of 4 V or less with respect to metallic lithium. The normal operating potential may be represented by a catalog value, an average operating potential, a nominal voltage, or the like of the material. The line L10 indicates the charging characteristics of the cell C. As shown by the line L10, in the LFP battery, dV / dQ (the ratio of the change amount dV of the battery voltage to the change amount dQ of the stored charge amount) rapidly increases in the range where the battery voltage is 3.5 V or more and 4.0 V or less. The voltage of the fully charged state of the cell C is 3.75 V. Note that the horizontal axis SOC (State Of Charge) of the graph represents the ratio of the current stored charge amount to the stored charge amount in the fully charged state as 0 to 100%.

[0021] Hereinafter, from the end on the positive electrode side (+Z side) of the laminate 10, the first, second, third, fourth, fifth,... cells C may be denoted as cell C-1, cell C-2, cell C-3, cell C-4, cell C-5,... respectively. Also, the odd-numbered cells C from the end on the positive electrode side of the laminate 10 are collectively referred to as "odd cells C" A ", and the even-numbered cells C from the end on the positive electrode side of the laminate 10 may be collectively referred to as "even cells C" B ". The odd cell C A corresponds to the (2N - 1)-th cell C, and the even cell C B corresponds to the (2N)-th cell C. N is an integer in the range from 1 to the total number of cells. In the laminate 10, the odd cell C A (the first cell) and the even cell C B (the second cell) are alternately arranged in the Z direction (lamination direction).

[0022] Referring back to FIG. 1, in S101, the assembling device 800 forms the laminate 10 (see FIGS. 2 and 3) to which the voltage detection terminal 20 and the connector 30 are connected through various processes such as coating, pressing, seal welding, separator welding, cutting, terminal (voltage detection terminal) welding, end face welding, injection molding, liquid injection, and temporary sealing in accordance with the control command from the control device 100. The laminate 10 may be sandwiched between a pair of end plates (constraint plates). The pair of end plates may be fastened so as to apply a constraint load from the outside to the inside in the stacking direction to the laminate 10. The assembling device 800 includes devices corresponding to each process.

[0023] In S102, the laminate 10 formed in S101 is attached to the temperature adjustment device 200 and the charging device 300. The temperature adjustment device 200 is configured to be able to adjust the temperature of the laminate 10. The temperature adjustment device 200 may have a thermostatic bath whose temperature can be controlled. The control device 100 adjusts the temperature of the laminate 10 by controlling the temperature adjustment device 200 in accordance with the initial charging conditions. Then, the charging device 300 performs the initial charging of the laminate 10 in accordance with the control command from the control device 100. Specifically, the charging device 300 applies a voltage between the positive terminal (the current collector 11 of the positive terminal electrode 2B shown in FIG. 2) and the negative terminal (the current collector 11 of the negative terminal electrode 2A shown in FIG. 2) of the laminate 10. Thereby, the charging current flows through the entire power storage unit 10a in the Z direction (stacking direction), and the power storage unit 10a is charged. The charging device 300 performs charging until, for example, the average voltage value of the plurality of cells C included in the power storage unit 10a reaches a predetermined target value.

[0024] In one example, the initial charging is constant current charging (CC charging). The conditions for the initial charging are, for example, a temperature of "25°C", a charging rate (C rate) of "0.06C", and a target value of "3.75V". Note that "1C" corresponds to the current value at which the total capacity (Ah) of the battery is charged in 1 hour.

[0025] Subsequently, in S103, the manufacturing system performs high-temperature aging on the laminate 10. FIG. 4 is a flowchart showing each process related to high-temperature aging (S103). High-temperature aging is a process of maintaining a predetermined temperature (high temperature) for a certain period of time. However, prior to the start of the processing flow shown in FIG. 4, the laminate 10 is attached to the charging device 500 (FIG. 1) instead of the charging device 300. Specifically, the charging device 500 includes a connector 510, a charging circuit 520, a power source 530, and a detector 540. The connector 510 is connected to the connector 30 (see FIG. 3) provided on the laminate 10. Thereby, the terminal (voltage detection terminal 20) of the connector 30 and the terminal 510a of the connector 510 are electrically connected.

[0026] Referring to FIG. 4, in S11, the temperature adjustment device 200 raises the temperature of the laminate 10 to the aging temperature in accordance with a control command from the control device 100. Thereafter, the high-temperature aging of the laminate 10 continues until the processing flow shown in FIG. 4 ends. During the high-temperature aging, the temperature of the laminate 10 is maintained between 50°C and 85°C. In this embodiment, the temperature of the laminate 10 is maintained at 65°C.

[0027] Subsequently, in S12, the control device 100 sets the values of the flags F1 and F2 to "0". The flags F1 and F2 are stored, for example, in the storage device 120.

[0028] In the subsequent S31, the charging device 500 charges the odd-numbered cells C A in accordance with a control command from the control device 100. Specifically, the charging circuit 520 performs constant-current charging (CC charging) on the odd-numbered cells C A using the electric power supplied from the power source 530. The charging circuit 520 individually charges each cell (cell C-1, cell C-3, cell C-5, ···) by applying a voltage between the negative electrode active material layer 12A and the positive electrode active material layer 12B via the voltage detection terminal 20 and the current collector 11. For each cell, a voltage is applied between the two current collectors 11 (voltage detection terminals 20) sandwiching the cell. By applying this voltage, the odd-numbered cells C Ais charged. The voltage of each cell increases as the stored power increases. The charging device 500 charges each cell until the cell voltage reaches a predetermined target value (first target voltage).

[0029] The detector 540 detects the state of the cell C via the voltage detection terminal 20 and the current collector 11. The detector 540 detects the voltage of the cell C, for example, based on the potential difference between two current collectors 11 (voltage detection terminals 20) sandwiching the cell C. In this embodiment, the cell voltage is measured by the two-terminal method. The two-terminal method is more susceptible to the influence of voltage drop (IR drop) due to energization than the four-terminal method. Also, metals tend to have a greater electrical resistance as the temperature increases. The detector 540 measures the voltage of each cell A during the charging of the above odd-numbered cells C. The control device 100 individually determines for each cell whether to end the charging based on the voltage of each cell during charging detected by the detector 540. The charging end timing is determined for each cell. Thus, during high-temperature aging, the charging of the odd-numbered cells C A is executed.

[0030] The initial conditions for charging during aging are, for example, a temperature of "65°C", a charging rate (C-rate) of "0.0017C", and a target value of "3.75V". In S31 of the first-time processing routine, the charging of the odd-numbered cells C A is executed under the initial conditions. However, the charging conditions during aging can be changed by the processing of S34 or S44 described later. And after the change of the charging conditions, the processing of S31 can be executed again. In S31 of the processing routine after the second time, the charging of the odd-numbered cells C A is executed under the latest charging conditions.

[0031] The control device 100 controls the odd-numbered cells C AFor each cell belonging to A (cell C-1, cell C-3, cell C-5, ···), the voltage of the non-powered cell is measured during the period from the end of charging until a time of 0.05 seconds or more and 60 seconds or less has elapsed, and the measurement result is stored in the storage device 120. Power is no longer supplied to the cell that has finished charging from the charging circuit 520. As a result, no current flows through the cell. In this embodiment, among the odd cells C A when the charging of any one of the cells is completed, the control device 100 measures the voltage of that cell at the timing when 0.1 second has elapsed since the end of charging. The cell voltages are measured in order from the cell that finished charging earlier. In this way, during high-temperature aging, the voltages of the odd cells C

[0032] after the end of charging are measured. A Subsequently, in S32, the control device 100 determines whether the magnitude of the voltage drop (IR drop) during charging exceeds a predetermined first reference value for each cell belonging to the odd cells C

[0033] The first reference value is set according to, for example, the battery voltage required for foreign matter dissolution. The control device 100 makes the determination in S32 using the cell voltage during charging and the cell voltage after the end of charging measured in S31. Specifically, the value obtained by subtracting the voltage of the non-powered cell measured immediately after the end of charging from the voltage of the powered cell measured immediately before the end of charging (in this embodiment, 3.75 V) corresponds to the voltage drop (IR drop) due to energization via the voltage detection terminal 20. A If the magnitude of the IR drop of all cells belonging to the odd cells C A is equal to or less than the first reference value, it is determined as NO in S32, and the process proceeds to S33. In S33, the control device 100 sets the value of the flag F1 to "1". The fact that the flag F1 indicates "1" means that the voltage of the odd cells C AIf the magnitude of the IR drop of any cell belonging to [the relevant group] exceeds the first reference value, it is determined as YES in S32, and the process proceeds to S34. In S34, the control device 100 changes the charging conditions during aging so that the cell voltage is likely to increase by charging. The control device 100 may reduce the charging current. In this embodiment, the control device 100 reduces the charging rate (C rate) by a predetermined amount (for example, 0.0001C). Since the voltage drop during charging becomes smaller as the charging current becomes smaller, the cell voltage is likely to increase by charging. When the process of S33 or S34 is executed, the process proceeds to S40.

[0034] In S40, the control device 100 determines whether the flag F2 indicates "1". In the first processing routine, since the flag F2 indicates "0" (see S12), it is determined as NO in S40, and the process proceeds to S41.

[0035] In S41, the charging device 500 charges the even cells C B in accordance with the control command from the control device 100. Specifically, the charging circuit 520 performs constant current charging (CC charging) on the even cells C B using the power supplied from the power source 530. The charging circuit 520 individually charges each cell (cell C-2, cell C-4,...) by applying a voltage between the negative electrode active material layer 12A and the positive electrode active material layer 12B via the voltage detection terminal 20 and the current collector 11. As a result, the even cells C B are charged. The charging device 500 charges each cell until the cell voltage reaches a predetermined target value (the second target voltage). Also, the detector 540 measures the voltage of each cell during the charging of the even cells C B . The control device 100 individually determines for each cell whether to end the charging based on the voltage of each cell during charging detected by the detector 540. Thus, the charging of the even cells C B is executed during high-temperature aging. The even cells C BThe charging conditions are the aforementioned initial conditions (refer to S31) if the charging conditions during aging have not been changed. On the other hand, when the charging conditions during aging have been changed by the process of S34 or S44 described later, the charging of the even cells C B is executed with the latest charging conditions.

[0036] The control device 100 measures the voltage of the non-powered cells for each cell (cell C-2, cell C-4, ···) belonging to the even cells C B during the period from 0.05 seconds to 60 seconds after the charging ends, and stores the measurement results in the storage device 120. In this embodiment, when the charging of any one of the even cells C B ends, the control device 100 measures the voltage of that cell (non-powered cell) at the timing when 0.1 second has elapsed since the end of charging. The voltages of the non-powered cells are measured in order from the cells that finished charging earlier. In this way, during high-temperature aging, the voltages of the even cells C B after the end of charging are measured.

[0037] Subsequently, in S42, the control device 100 determines whether or not the magnitude of the voltage drop (IR drop) during charging exceeds a predetermined second reference value for each cell belonging to the even cells C B . The second reference value is set according to, for example, the battery voltage required for foreign matter dissolution. The second reference value may be the same as or different from the aforementioned first reference value. The control device 100 makes the determination in S42 using the cell voltage during charging and the cell voltage after the end of charging measured in S41. Specifically, the value obtained by subtracting the voltage of the non-powered cell measured immediately after the end of charging from the voltage of the powered cell measured immediately before the end of charging (3.75V in this embodiment) corresponds to the voltage drop (IR drop) due to energization via the voltage detection terminal 20.

[0038] Even cells C BWhen the magnitude of the IR drop of all cells belonging to is equal to or less than the second reference value, it is determined as NO in S42, and the process proceeds to S43. In S43, the control device 100 sets the value of the flag F2 to "1". That the flag F2 indicates "1" means that the voltage of the even cells C B has risen to a voltage sufficient to dissolve foreign matter. Thereafter, the process proceeds to S51.

[0039] On the other hand, when the magnitude of the IR drop of any cell belonging to the even cells C B exceeds the second reference value, it is determined as YES in S42, and the process proceeds to S44. In S44, the control device 100 changes the charging conditions during aging. The control device 100 may reduce the charging current. In this embodiment, the control device 100 reduces the charging rate (C rate) by a predetermined amount (for example, 0.0001C). Thereafter, the process proceeds to S52.

[0040] In each of S51 and S52, the control device 100 determines whether the flag F1 indicates "1". When the flag F1 indicates "0" (NO in S51 or S52), the process returns to S31. In S31, the odd cells C A are charged under the latest charging conditions. That is, the odd cells C A are charged again under conditions different from the previous charge. When both the flags F1 and F2 indicate "0" (NO in S52), it is determined as NO in S40 after the odd cells C A are charged again. Then, in the subsequent S41, the control device 100 charges the even cells C B again under conditions different from the previous charge. When the flag F1 indicates "0" but the flag F2 indicates "1" (NO in S51), it is determined as YES in S40 after the odd cells C A are charged again, and the process proceeds to S51. When the flag F1 indicates "1" but the flag F2 indicates "0" (YES in S52), the process returns to S41. In S41, the control device 100 charges the even cells C BRecharge again. If both flags F1 and F2 indicate "1" (YES in S51), the process proceeds to S60. As a result, the charging during high-temperature aging ends.

[0041] As described above, the method for manufacturing a power storage device according to this embodiment does not charge the even cells C B and individually charges each cell (first cell) belonging to the odd cells C A until the cell voltage reaches the first target voltage (S31 in FIG. 4), and individually measures the non-powered cell voltage after charging is completed for each cell (cells C-1, C-3, ···) belonging to the odd cells C A (S31 in FIG. 4), and does not charge the odd cells C A and individually charges each cell (second cell) belonging to the even cells C B until the cell voltage reaches the second target voltage (S41 in FIG. 4), and individually measures the non-powered cell voltage after charging is completed for each cell (cells C-2, C-4, ···) belonging to the even cells C B (S41 in FIG. 4).

[0042] FIG. 5 is a diagram for explaining the charging during high-temperature aging. Referring to FIGS. 4 and 5 together, lines L1, L2, and L3 show the voltage transitions during charging of three cells included in the odd cells C A . Line L1 shows the characteristics of the cell that completes charging the earliest among the odd cells C A . Line L3 shows the characteristics of the cell that completes charging the latest among the odd cells C A . Lines L4, L5, and L6 show the voltage transitions during charging of three cells included in the even cells C B . Line L4 shows the characteristics of the cell that completes charging the earliest among the even cells C B . Line L6 shows the characteristics of the cell that completes charging the latest among the even cells C B . At timing t1, when charging of all cells included in the odd cells C A is completed, charging of the even cells C B is started. Then, at timing t2, the even cells C BCharging of all cells included therein is completed.

[0043] In each of S31 and S41 in FIG. 4, when charging the cell C, a voltage is applied to the cell C via the voltage detection terminal 20. When the charging current flows through the voltage detection terminal 20, a voltage drop (IR drop) due to energization occurs. For this reason, as shown by lines L11 and L12, the cell voltage measured during energization (line L11) is higher than the cell voltage measured in the non-energized state (line L12) by the amount of the IR drop. Lines L21 and L22 respectively show the relationship between the current and voltage of the cell C having the voltage detection terminal 20 with electrical resistances of 0.1 Ω and 0.4 Ω. The higher the electrical resistance of the voltage detection terminal 20, the larger the IR drop.

[0044] Also, in each of S31 and S41 in FIG. 4, the control device 100 measures the cell voltage during charging and the cell voltage after charging is completed. By measuring the cell voltage during charging, the control device 100 can determine whether the cell voltage during charging has reached the target voltage. The control device 100 can grasp the magnitude of the IR drop by comparing the cell voltage during charging (for example, the target voltage) with the cell voltage after charging is completed. If the IR drop is sufficiently small, it is highly likely that the cell voltage has risen sufficiently due to charging during aging. On the other hand, if the IR drop is large, it is highly likely that the cell voltage has not risen sufficiently due to charging during aging. Thus, according to the above method, it becomes possible to confirm whether the battery voltage (cell voltage) has risen sufficiently due to charging during aging.

[0045] Due to variations in the voltages of the plurality of cells C in the laminate 10, even if the voltages of some of the cells C reach the target value, the voltages of other cells C may not reach the target value. Therefore, the control device 100 charges the odd-numbered cells C A and the even-numbered cells C B separately as described above, thereby charging all the cells C included in the laminate 10 individually. As a result, it becomes easier to raise the voltages of all the cells C included in the laminate 10 to a voltage sufficient to dissolve foreign matter.

[0046] As shown by lines L1 to L6, when the charging of cell C is completed, the voltage of cell C tends to decrease with the passage of time. Therefore, in order to obtain the IR drop by comparing the voltage during energization with the voltage during non-energization, it is desirable to measure the voltage of the non-energized cell C at a timing close to the end of charging, that is, immediately after the end of charging. On the other hand, if the measurement timing of the cell voltage is too close to the end of charging, there is a possibility that the cell voltage may be measured erroneously before cell C enters the non-energized state. Therefore, the control device 100 measures the voltage of the non-energized cell C during a period from 0.05 seconds to 60 seconds after the charging of cell C is completed. According to such a method, it becomes easier to appropriately acquire the voltage of the non-energized cell immediately after the end of charging. As shown by line L30, the voltage of cell C hardly changes during the period from the end of charging of cell C until 60 seconds have elapsed.

[0047] Odd-numbered cell C A and even-numbered cell C B Each of them is charged with a constant current during high-temperature aging. When the laminate 10 is aged at a temperature higher than room temperature (50°C or higher), for example, the dissolution of foreign substances (such as unnecessary metals) mixed in when forming the laminate 10 is promoted. Also, according to constant-current charging, fluctuations in the IR drop during charging are suppressed.

[0048] In a battery with a low operating potential of the positive electrode active material, such as an LFP battery for example, there is a high possibility that the battery voltage will not rise to a sufficient voltage to dissolve foreign substances. In particular, when the IR drop is large in a battery where the operating potential of the positive electrode active material is 4V or less, the battery voltage may not rise to a sufficient voltage to dissolve foreign substances even if the battery is charged to full charge. Therefore, the control device 100 confirms whether the battery voltage (cell voltage) has risen sufficiently by charging during aging by the method described above.

[0049] The manufacturing method of the power storage device according to this embodiment includes determining whether the magnitude of the voltage drop during charging exceeds a reference value by using the measured cell voltage during charging and the cell voltage after charging is completed (S32, S42 in FIG. 4), and when it is determined that the magnitude of the voltage drop exceeds the reference value, recharging the cell C under conditions different from the previous charging. When the voltage drop (IR drop) during charging is large, it is highly likely that the cell voltage has not risen sufficiently due to the charging during aging. Therefore, the control device 100 changes the charging conditions and executes recharging under the changed conditions. Specifically, when it is determined that the magnitude of the voltage drop exceeds the reference value, the charging conditions are changed at S34 or S44. In this case, at least one of the flags F1 and F2 is maintained at "0". For this reason, it is determined as NO at S40, S51, or S52, and the charging of the cell C is executed again at S31 or S41. This makes it easier to raise the cell voltage to a sufficient voltage to dissolve foreign substances.

[0050] Referring to FIG. 4 again, even after the charging of the laminate 10 is completed, the temperature adjustment device 200 continues the high-temperature aging of the laminate 10 at S60. The control device 100 causes the temperature adjustment device 200 to continue the high-temperature aging of the laminate 10 until a predetermined time (for example, 10 hours) elapses after the charging of the laminate 10 is stopped (for example, after it is determined as YES at S51). During the high-temperature aging, the temperature of the laminate 10 is maintained at 65°C. Then, when the above-mentioned predetermined time elapses, the processing flow shown in FIG. 4 ends. As a result, the high-temperature aging (S103 in FIG. 1) ends. After that, the laminate 10 is sent to a subsequent process (for example, an inspection process).

[0051] The laminate 10 activated as described above can function as a power storage device alone. However, the laminate 10 may be used as one module, and a plurality of modules may be combined to manufacture a power storage device. For example, a plurality of modules may be stacked such that the plurality of modules are electrically connected in series, and the stacked plurality of modules may be stored in a case together with other components (such as a cooler) to complete a battery pack (power storage device). The manufactured power storage device can be mounted on, for example, a moving body. Examples of the moving body include automobiles (electric vehicles, hybrid vehicles, etc.), vehicles other than automobiles (ships, airplanes, etc.), mobile machines (agricultural machines, construction machines, etc.), and unmanned moving bodies (automated guided vehicles, robots, etc.). However, the application of the manufactured battery is arbitrary, and a stationary battery may be manufactured by the above method.

[0052] The processing flow shown in FIG. 4 can be changed as appropriate. For example, the charging of the odd-numbered cells C B may be executed after the charging of the even-numbered cells C A . Also, in the above embodiment, in each of S34 and S44, the conditions common to the charging of the odd-numbered cells C A and the charging of the even-numbered cells C B are changed. However, the present invention is not limited to this, and the charging conditions for the odd-numbered cells C A and the charging conditions for the even-numbered cells C B may be managed separately. The charging conditions for the odd-numbered cells C A may be changed in S34, and the charging conditions for the even-numbered cells C B may be changed in S44. Further, the control device 100 may end the high-temperature aging in S60 when a predetermined time has elapsed since the start of aging (S11).

[0053] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the description of the above embodiments but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0054] 1 bipolar electrode, 10 laminate, 11 current collector, 12A negative electrode active material layer, 12B positive electrode active material layer, 13 separator, 20 voltage detection terminal, 100 control device, C cell, C A odd cell, C B even cell.

Claims

1. A method for manufacturing an energy storage device including a laminate, comprising: The laminate includes a plurality of bipolar electrodes and a plurality of separators. Each of the plurality of bipolar electrodes has a current collector to which a voltage detection terminal is connected, a positive electrode active material layer provided on one surface of the current collector, and a negative electrode active material layer provided on the other surface of the current collector. In the laminate, a cell including the positive electrode active material layer, the separator, and the negative electrode active material layer is formed between the stacked plurality of current collectors. The method for manufacturing the energy storage device includes: Forming the laminate; Charging the cell by applying a voltage between the positive electrode active material layer and the negative electrode active material layer through the voltage detection terminal and the current collector while aging the laminate; Measuring the voltage of the cell during charging of the cell; Measuring the voltage of the cell in a non-energized state while continuing the aging after the charging of the cell is completed and a predetermined time has elapsed; A method for manufacturing an energy storage device, including the above steps.

2. During the aging, the temperature of the laminate is maintained at 50°C or higher. The charging of the cell is constant current charging and ends when the voltage of the cell reaches a target voltage. The positive electrode active material layer includes a positive electrode active material having an operating potential of 4 V or less with respect to lithium metal. The measurement of the voltage after the charging of the cell is performed during a period from 0.05 seconds to 60 seconds after the charging of the cell is completed. The manufacturing method of the energy storage device according to claim 1.

3. The manufacturing method of the energy storage device according to claim 1, wherein the positive electrode active material layer includes lithium iron phosphate.

4. The laminate includes a plurality of first cells and a plurality of second cells. In the laminate, the first cells and the second cells are alternately arranged in the stacking direction of the laminate. The charging of the cell includes: Individually charging each of the plurality of first cells until the cell voltage reaches a first target voltage without charging the plurality of second cells; Individually charging each of the plurality of second cells until the cell voltage reaches a second target voltage without charging the plurality of first cells; Including; The measurement of the voltage after the charging of the cell includes: Individually measuring the non-energized state cell voltage of each of the plurality of first cells after the charging is completed; Individually measuring the non-energized state cell voltage of each of the plurality of second cells after the charging is completed; The manufacturing method of the energy storage device according to claim 1, including the above steps.

5. During charging of the cell, measure the voltage of the cell via the voltage detection terminal, using the measured cell voltage during charging and the cell voltage after charging is completed, determine whether the magnitude of the voltage drop during charging exceeds a reference value, when it is determined that the magnitude of the voltage drop exceeds the reference value, re-execute charging of the cell under conditions different from the charging, The method for manufacturing a power storage device according to any one of claims 1 to 4, further comprising.

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