Method for manufacturing bipolar battery

Abstract

A method for manufacturing a bipolar secondary battery includes: an initial charging step in which a first battery cell group having a plurality of battery cells adjacent to each other in a stacking direction and a second battery cell group having a plurality of battery cells adjacent to the battery cells included in the first battery cell group are charged to a predetermined voltage; a high-temperature aging step in which aging is performed at a temperature higher than normal temperature; and an aging-time charging step for alternately charging the first battery cell group and the second battery cell group until a predetermined voltage is reached in the high-temperature aging step. In the aging-time charging step, the completion condition of charging of at least one of the first battery cell group and the second battery cell group is determined on the basis of the dissolution rate calculated from the type of metal foreign matter and the positive electrode potential, and the voltage and aging time of each battery cell in the aging-time charging step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bipolar battery. Background Art

[0002] In the past, for the manufacturing method of secondary batteries such as lithium-ion secondary batteries, there is a known technology including a high-temperature aging process, which makes the quality of the battery cells uniform by keeping the assembled battery cells at high temperatures for a long time, so that the electrolyte can penetrate into the electrode layer and irreversible side reactions other than the battery reaction can be easily carried out. Japanese Patent Publication No. 2015-122160 discloses a technology in which, when the temperature or time deviates from the standard range during high-temperature aging, the subsequent aging conditions can be adjusted to ensure the quality while ensuring the battery capacity. Summary of the invention

[0003] On the other hand, in a bipolar battery having a bipolar structure, since the battery cells adjacent to each other in the loading direction of each battery cell are charged using a common terminal, it is necessary to charge the battery cells stacked with even numbers and the battery cells stacked with odd numbers separately in the stacking direction. Therefore, the time required for the high temperature aging process for charging in order to smoothly dissolve foreign matter may be prolonged.

[0004] In view of the above facts, an object of the present invention is to provide a method for manufacturing a bipolar secondary battery, which method can shorten the high-temperature aging time in the high-temperature aging process.

[0005] The manufacturing method of a bipolar secondary battery of the first embodiment of the present invention is a manufacturing method of a bipolar secondary battery, in which a plurality of battery cells including a positive electrode, a negative electrode and an electrolyte layer are stacked, and the manufacturing method of the bipolar secondary battery includes: an initial charging process of charging a first battery cell group having a plurality of battery cells adjacent to each other in the stacking direction and a second battery cell group having a plurality of battery cells adjacent to the battery cells included in the first battery cell group to a specified voltage; a high-temperature aging process of aging at a high temperature higher than normal temperature; and an aging charging process of alternately charging the first battery cell group and the second battery cell group until a specified voltage is reached in the high-temperature aging process, in which the completion condition of charging of at least one of the first battery cell group and the second battery cell group is determined based on the dissolution rate calculated according to the type of metal foreign matter and the positive electrode potential, and the voltage and aging time of each of the battery cells in the aging charging process.

[0006] In the manufacturing method of the bipolar secondary battery of the first embodiment of the present invention, there is an aging charging step in which a first battery cell group having a plurality of battery cells adjacent to each other in the stacking direction and a second battery cell group having a plurality of battery cells adjacent to the battery cells included in the first battery cell group are alternately charged until a predetermined voltage is reached in the high temperature aging step. Moreover, in the aging charging step, the completion condition of charging of at least one of the first battery cell group and the second battery cell group is determined based on the dissolution rate calculated according to the type of metal foreign matter and the positive electrode potential, and the voltage and aging time of each battery cell in the aging charging step. As described above, the completion condition of charging is determined based on the dissolution rate calculated according to the type of metal foreign matter and the positive electrode potential, and the voltage and aging time of each battery cell in the aging charging step. Therefore, in the high temperature aging step, compared with the case where charging is completed under the completion condition set in the battery cell with the lowest voltage without considering the dissolution rate of foreign matter as in the prior art, the time required until charging is completed can be shortened, thereby shortening the high temperature aging time.

[0007] In addition, the manufacturing method of the bipolar secondary battery of the second embodiment of the present invention is that, in the configuration of the first embodiment, in the above-mentioned aging charging process, a switching charging capacity or a switching charging time is set as a switching judgment condition for switching the charging of the above-mentioned battery cell that is the charging object, and the above-mentioned switching charging capacity is a value smaller than the charging capacity at the last charging, and the above-mentioned switching charging time is a time shorter than the charging time at the last charging.

[0008] As an example, after the first charge of the first battery cell group is completed, the electricity charged in each battery cell of the first battery cell group may disappear during the first charge of the second battery cell group. Therefore, when the first battery cell group is charged for the second and subsequent times, the electricity lost during the charging waiting period is replenished, and thus the charging capacity gradually decreases compared to the first charge. That is, the more times the charging is performed, the closer the battery cell is to full charge, and therefore the charging capacity decreases.

[0009] Therefore, in the manufacturing method of the bipolar secondary battery of the second embodiment of the present invention, as the switching judgment condition for charging the battery cell to be charged, the switching charging capacity is set to a value less than the charging capacity at the last charge, and the switching charging time is set to a time shorter than the charging time at the last charge. Therefore, in the aging charging process, the battery cell to be charged is charged with the charging capacity or charging time corresponding to the number of charging times. Thereby, useless charging can be prevented, and the time required for charging to be completed can be shortened.

[0010] In addition, the manufacturing method of the bipolar secondary battery of the third scheme of the present invention is that, in the configuration of the first scheme or the second scheme, in the above-mentioned aging charging process, the abnormal judgment condition for judging the above-mentioned battery cell that is the charging object as abnormal is set to a situation where the change in at least one of the voltage change relative to time and the battery capacity change relative to voltage deviates from a predetermined error range of the change.

[0011] As an example, when there is an extreme change in charging conditions, the change in voltage or the change in battery capacity will deviate from the normal range. For example, in the case of a short circuit in a battery cell, the voltage does not rise, so the change in voltage becomes smaller. Therefore, in the manufacturing method of a bipolar secondary battery of the third scheme of the present invention, in the aging charging process, the abnormal judgment condition for judging the battery cell to be charged as abnormal is set to the case where the change in at least one of the change in voltage relative to time and the change in battery capacity relative to voltage deviates from the predetermined error range of the change. Thus, when the change in voltage or the change in battery capacity deviates from the predetermined error range of the change, it will be judged as abnormal, so even if the inspection process is not performed, defective products can be detected in the aging charging process.

[0012] In addition, the manufacturing method of the bipolar secondary battery of the fourth embodiment of the present invention is that in the configuration of any one of the first to third embodiments, in the above-mentioned aging charging process, the abnormality judgment condition during the charging stop period of the above-mentioned battery cell to be charged is set to a situation where the voltage after a predetermined specified time from the charging stop is less than a specified value of the voltage pre-set for each charging number.

[0013] As an example, since the battery cell approaches full charge every time the number of charging times increases, there is a tendency for the voltage drop during the charging pause period to converge. Therefore, in the manufacturing method of the bipolar secondary battery of the fourth aspect of the present invention, the abnormality determination condition during the charging pause period of the battery cell to be charged is set to the case where the voltage after a predetermined time has passed since the charging pause is less than the predetermined value of the voltage set in advance for each charging number. Thus, when the voltage during the charging pause period is less than the predetermined value of the voltage set in advance for each charging number, it will be determined as abnormal, so that even if the inspection process is not entered, defective products can be detected in the charging process during aging.

[0014] Furthermore, a fifth aspect of the present invention provides a method for manufacturing a bipolar secondary battery, wherein in the configuration of any one of the first to fourth aspects, the positive electrode uses lithium iron phosphate as a positive electrode active material.

[0015] In the method for manufacturing a bipolar secondary battery according to the fifth aspect of the present invention, since lithium iron phosphate is used as the positive electrode active material in the positive electrode, the voltage drop near the dissolution potential of foreign matter is steeper, and therefore the effects of the present invention are more easily obtained.

[0016] As described above, the method for manufacturing a bipolar secondary battery of the present invention has an excellent effect of being able to shorten the high-temperature aging time in the high-temperature aging step. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0018] Figure 1 This is a cross-sectional view of an electrode body according to one embodiment of the present invention.

[0019] Figure 2 This is a cross-sectional view schematically showing the general structure of a two-dimensional battery according to one embodiment of the present invention.

[0020] Figure 3 This is a graph showing the dissolution rate of SUS foreign matter according to the electric potential.

[0021] Figure 4 This is a diagram showing the relationship between the voltage in the odd-numbered battery cells and the dissolved size of the SUS foreign matter with respect to the passage of time according to the first embodiment of the present invention.

[0022] Figure 5 This is a diagram showing the relationship between the voltage in the odd-numbered battery cells and the dissolved size of the SUS foreign matter with respect to the passage of time according to the second embodiment of the present invention.

[0023] Figure 6 This is a diagram showing the relationship between the voltage in the odd-numbered battery cells and the dissolved size of the SUS foreign matter with respect to the passage of time according to the third embodiment of the present invention.

[0024] Figure 7 1 is a diagram showing the switching determination condition of the charging capacity with respect to the number of charging times in odd-numbered battery cells.

[0025] Figure 8 The diagram shows the switching determination conditions of the charging time with respect to the number of charging times in odd-numbered battery cells.

[0026] Fig. 9 is a charging graph showing the relationship between voltage and charging time;

[0027] Fig. 10A It is a graph showing the amount of change in voltage with respect to time.

[0028] Fig. 10B It is a graph showing the amount of change in voltage relative to the voltage.

[0029] Fig.11 It is a graph showing the amount of change in battery capacity with respect to voltage.

[0030] Fig.12 This is a graph showing the relationship between the charging rest elapsed time and the voltage for each number of charging times.

[0031] Fig.13 This is a graph showing the relationship between the number of charge times and the voltage 2 hours after the charge is stopped.

[0032] Fig.14 This is a graph showing the relationship between the number of charge times and the voltage 10 hours after the charge is stopped. DETAILED DESCRIPTION

[0033] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described with reference to the accompanying drawings. The secondary battery 100 according to the present embodiment is used, for example, in a lithium-ion secondary battery or a nickel-hydrogen secondary battery as an example of a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery is used, for example, as a battery for various vehicles such as a forklift, a hybrid vehicle, and an electric vehicle. The non-aqueous electrolyte secondary battery is, for example, a flat laminated battery, and is specifically composed of a plurality of bipolar electrodes 10 described later stacked.

[0034] like Figure 1 As shown, the bipolar electrode 10 includes: a current collector 12 including one surface 12a and another surface 12b provided on the opposite side of the one surface 12a, a positive electrode mixture layer 14 as a positive electrode provided on the one surface 12a, and a negative electrode mixture layer 16 as a negative electrode provided on the other surface 12b. The bipolar electrode 10 can be easily obtained by applying one of the negative electrode mixture or the positive electrode mixture on the current collector 12 and drying it, and then applying and drying the other in the same manner. The bipolar electrode 10 can be pressed and cut as needed.

[0035] The current collector 12 is formed of a rectangular metal plate formed of a metal such as aluminum, stainless steel, nickel, copper, etc. Alternatively, it may be a foil formed by covering a metal surface with aluminum or copper, etc. In addition, the edge portion 12c of the current collector 12 is formed in a rectangular frame shape and is an uncoated area where the positive electrode mixture layer 14 and the negative electrode mixture layer 16 are not coated. In addition, the metal member constituting the current collector 12 can be appropriately selected from one or more metal members according to the purpose.

[0036] The positive electrode mixture layer 14 includes a positive electrode active material, a conductive agent, and a binder. Examples of the positive electrode active material include lithium composite oxides. Examples of the lithium composite oxides include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate (LFP), and LiNi1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc. The lithium composite oxide may contain at least one selected from F, Cl, N, S, Br and I. The shape of the positive electrode active material is not particularly limited. For example, it may be spherical (for example, true spherical, ellipsoidal, etc.), fibrous, etc.

[0037] Examples of the conductive agent include carbon materials such as acetylene black, Ketjen black, vapor grown carbon fiber (VGCF (registered trademark)), and carbon nanotubes (CNTs). The content of the conductive agent is, for example, 3 to 5 mass % relative to the negative electrode active material.

[0038] Examples of the binder include polyvinylidene fluoride (PVDF) / NMP, styrene butadiene rubber (SBR) / water, polytetrafluoroethylene (PTFE) / water, etc. The content of the binder is, for example, 3% to 5% by mass relative to the negative electrode active material.

[0039] The negative electrode mixture layer 16 includes a negative electrode active material, a conductive agent, and a binder. Examples of the negative electrode active material include Li-based active materials such as metallic lithium, carbon-based active materials such as graphite, lithium titanate (e.g., Li4Ti5O 12 ) and other oxide-based active materials and Si-based active materials such as Si monomers. The shape of the negative electrode active material is not particularly limited. For example, it can be spherical (for example, a perfect sphere, an ellipsoid, etc.), fibrous, etc.

[0040] As with the positive electrode mixture layer 14, examples of the conductive agent include carbon materials such as acetylene black, Ketjen black, vapor grown carbon fiber (VGCF (registered trademark)), and carbon nanotubes (CNT). The content of the conductive agent is, for example, 3 to 5 mass % relative to the negative electrode active material.

[0041] As for the binder, similar to the positive electrode mixture layer 14, for example, polyvinylidene fluoride (PVDF) / NMP, styrene butadiene rubber (SBR) / water, polytetrafluoroethylene (PTFE) / water binders can be cited. The content of the binder is, for example, 3% to 5% by mass relative to the negative electrode active material.

[0042] like Figure 1 As shown in FIG. 1 , bipolar electrodes 10 constructed as described above are alternately stacked with electrolyte layers 18 interposed therebetween, thereby constituting a bipolar secondary battery 100 .

[0043] In the present embodiment, the electrolyte layer 18 may include a solid electrolyte layer, or may include a separator and an electrolytic solution.

[0044] When the electrolyte layer 18 is a solid electrolyte layer, examples of the solid electrolyte include lithium lanthanum zirconate, LiPON, Li1+X Al X Ge 2-X (PO4)3, Li-SiO glass, Li-Al-SO glass and other oxide solid electrolytes; Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5-GeS2 and other sulfide solid electrolytes. The solid electrolyte layer can be obtained by pressing the above solid electrolytes.

[0045] When the electrolyte layer 18 is a separator and an electrolyte, the separator may be, for example, a resin sheet such as polyethylene (PE) or polypropylene (PP). In addition, the electrolyte contains a predetermined electrolyte and a solvent, and the predetermined electrolyte may be LiPF6, LiBF4, LiAsF6, Li(CF3SO2)2N, Li(C2F5SO2)2N, LiTaF6, LiClO4, LiCF3SO3, etc.

[0046] Examples of the solvent include cyclic carbonate solvents such as ethylene carbonate (EC) and propylene carbonate (PC); chain carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The concentration of the electrolyte solution is, for example, 0.1 to 1 mol / L.

[0047] In the manufacturing method of the secondary battery 100 of the present embodiment, after the manufacturing of the secondary battery 100 is completed, the initial charging process and the high-temperature aging process of the secondary battery 100 are performed. The initial charging process is performed at a relatively low charging rate to suppress the temperature rise of the secondary battery 100. In the present embodiment, CCCV charging is adopted as an example. CCCV charging is a charging method as follows. First, charging is performed with a constant current (Constant Current, CC). When the battery voltage reaches a specified value, the control is switched to a constant voltage (Constant Voltage, CV) and charging is continued. While avoiding an overvoltage charging state, charging is performed until it is fully charged. In the charging process, a full charge with a state of charge (State Of Charge, SOC) of 100% is performed, but it can also be, for example, SOC 90%. In the present embodiment, the charging process is performed at a room temperature of about 20°C, for example.

[0048] Here, the secondary battery 100 of the present embodiment is a bipolar secondary battery in which a plurality of bipolar electrodes 10 are stacked with an electrolyte layer 18 interposed therebetween. Figure 1As shown, in this embodiment, the positive electrode mixture layer 14, the electrolyte layer 18, and the negative electrode mixture layer 16 disposed between the current collectors 12 adjacent to each other in the stacking direction D are regarded as one battery cell 20. In the bipolar secondary battery 100, when each battery cell 20 is charged, the terminal 32 connected to the current collector 12 located between the adjacent battery cells 20 is used, so that the adjacent battery cells 20 cannot be charged at the same time.

[0049] Therefore, in this embodiment, every other adjacent battery cell is charged alternately in the stacking direction D. Figure 2 As shown, every other adjacent battery cell from the upper side to the lower side in the stacking direction D is an odd-numbered battery cell 20A, and the battery cell adjacent to the odd-numbered battery cell 20A in the stacking direction D is an even-numbered battery cell 20B. In addition, a plurality of odd-numbered battery cells 20A are aggregated into an odd-numbered battery cell group 30A as a first battery cell group, and a plurality of even-numbered battery cells 20B are aggregated into an even-numbered battery cell group 30B as a second battery cell group. In this embodiment, the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B are charged alternately. In addition, Figure 2 In the figure, the colored battery cells 20 indicate the battery cells 20 that are in the charging period.

[0050] After the charging process is completed, the high-temperature aging process is then carried out. The high-temperature aging process is a process in which the secondary battery 100 charged in the charging process is stored in a high-temperature environment. In the high-temperature aging process, the secondary battery 100 is chemically stabilized and activated. That is, in the presence of a micro short circuit caused by metal foreign matter mixed into the battery cell 20 due to the manufacturing process or materials, the high temperature will accelerate the dissolution and precipitation (chemical reaction) of the metal foreign matter, thereby detecting the short circuit. Therefore, the high-temperature aging process is carried out by maintaining the temperature at a temperature higher than room temperature, for example, a high temperature of about 60°C in the present embodiment.

[0051] However, for example, in the case where the secondary battery 100 is a lithium-ion secondary battery, when the initial charging is stopped, the voltage (positive electrode potential) immediately decreases. As described above, in the present embodiment, since the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B are charged alternately, it is difficult to maintain all the battery cells 20 at a specified voltage during the series charging. In addition, in the case where it can be assumed that the mixed metal foreign matter is, for example, SUS304, in order to dissolve SUS304, 62.5°C or more and 3.60V or more become necessary conditions, so charging is required in the high temperature aging process.

[0052] Therefore, in the present embodiment, an aging charging step is included in which the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B are alternately charged in the high-temperature aging step. In the aging charging step, the completion condition of charging of at least one of the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B is determined based on the dissolution rate calculated based on the type of the metal foreign matter and the positive electrode potential, and the voltage and aging time of each battery cell 20 in the aging charging step.

[0053] For example, in the case where the foreign matter that can be assumed is a SUS foreign matter, Figure 3 As shown in FIG. 1 , the dissolution rate varies depending on the positive electrode potential. Specifically, the higher the positive electrode potential, the faster the dissolution rate. As an example, it can be assumed that the outer diameter of the SUS foreign body (hereinafter referred to as the dissolution size) is to be dissolved to less than 200 μm. In this case, based on the dissolution rate of the SUS foreign body corresponding to the positive electrode potential (refer to FIG. 1 ), the dissolution rate of the SUS foreign body corresponding to the positive electrode potential (refer to FIG. 1 ) is 200 μm. Figure 3 ), the voltage and time conditions required to dissolve the SUS foreign matter in each battery cell 20 to a size of less than 200 μm are pre-set, and charging is determined to be complete when the set conditions are met. Specifically, as an example, the time t is calculated in a manner that satisfies the following formula (1). Where t represents time (h) and x represents the dissolution rate (μm / h).

[0054] Table 1

[0055] Electrode potential Battery voltage Dissolution rate x Time t V relative to Li V μm / h h 3.83 3.75 6.592 Calculated by formula (1) 3.75 3.67 4.531 Calculated by formula (1) 3.7 3.62 3.919 Calculated by formula (1) 3.6 3.52 3.219 Calculated by formula (1)

[0056] 200≤x 3.67～3.75 ×t 3.67～3.75 +x 3.62～3.67 ×t 3.62～3.67 +x 3.53～3.62 ×t 3.53～3.62 …(1)

[0057] Figure 4 2 is a graph showing the relationship between the voltage in the odd-numbered battery cell 20A and the dissolved size of the SUS foreign matter with respect to the passage of time t according to the first embodiment of the present invention. Figure 4 In FIG. 1 , the solid line is a curve diagram of the odd-numbered battery cell 20A, and the dotted line is a curve diagram of the even-numbered battery cell 20B. Figure 4As shown, in the first embodiment, as an example, the odd-numbered battery cell 20A is charged, and the voltage of the odd-numbered battery cell 20A is maintained at 3.75 (v). After the time t when the dissolved size of the SUS foreign matter reaches 200 μm, that is, 28 to 29 hours have passed, the charging of the odd-numbered battery cell 20A is completed. And when the charging of the odd-numbered battery cell 20A is completed, the charging of the even-numbered battery cell 20B is started next. Specifically, in the above Table 1, the dissolution rate x when the battery voltage is 3.75 (v) is 6.592 (μm / h), so the time t is calculated by applying this value to the above formula (1).

[0058] Then, similarly to the odd-numbered battery cell 20A, the charging of the even-numbered battery cell 20B is started, and the voltage of the even-numbered battery cell 20B is maintained at 3.75 (v). After the time t at which the dissolved size of the SUS foreign matter reaches 200 μm, that is, 58 hours have passed, the charging of the even-numbered battery cell 20B is completed. That is, in the odd-numbered battery cell 20A and the even-numbered battery cell 20B (the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B), it takes 58 hours for the SUS foreign matter to dissolve.

[0059] Figure 5 2 is a graph showing the relationship between the voltage in the odd-numbered battery cell 20A and the dissolved size of the SUS foreign matter with respect to the passage of time t according to the second embodiment of the present invention. Figure 5 As shown, in the second embodiment, as an example, the odd-numbered battery cell 20A is charged, and the voltage of the odd-numbered battery cell 20A is maintained at 3.75 (v), and the charging of the odd-numbered battery cell 20A is completed after the time t, that is, 24 hours, when the dissolution size of the SUS foreign matter can naturally reach 200 μm. And when the charging of the odd-numbered battery cell 20A is completed, the charging of the even-numbered battery cell 20B is started next.

[0060] That is, in each battery cell 20, the dissolution of the SUS foreign matter proceeds not only during the charging period (while the voltage is maintained at a predetermined voltage), but also during the rest period after charging (while the voltage drops from a predetermined voltage). Therefore, by obtaining the voltage value relative to the elapsed time in advance, the time when the dissolution size of the SUS foreign matter can naturally reach 200 μm is obtained based on the above formula (1).

[0061] like Figure 5 As shown, in the odd-numbered battery cell 20A, the dissolved size of the SUS foreign matter reached 200 μm after 33 hours from the start of charging. That is, the foreign matter dissolved naturally in 9 hours after the completion of charging.

[0062] Moreover, similarly to the odd-numbered battery cell 20A, the charging of the even-numbered battery cell 20B is started, and the voltage of the even-numbered battery cell 20B is maintained at 3.75 (v), and after the time t, that is, 48 ​​hours have passed, when the dissolved size of the SUS foreign matter can naturally reach 200μm, the charging of the even-numbered battery cell 20B is completed. Moreover, after the charging of the even-numbered battery cell 20B is completed, it takes 9 hours to dissolve naturally. That is, in the odd-numbered battery cell 20A and the even-numbered battery cell 20B (odd-numbered battery cell group 30A and even-numbered battery cell group 30B), it takes 57 hours to dissolve the SUS foreign matter, and the time required for dissolving the SUS foreign matter is shortened by 1 hour compared with the first embodiment described above.

[0063] Figure 6 2 is a graph showing the relationship between the voltage in the odd-numbered battery cell 20A and the dissolved size of the SUS foreign matter with respect to the passage of time t according to the third embodiment of the present invention. Figure 6 As shown, in the third embodiment, as an example, the odd-numbered battery cell 20A is charged and the voltage of the odd-numbered battery cell 20A is maintained at 3.75 (V) for 10 hours, and then the first charge is completed. And when the first charge of the odd-numbered battery cell 20A is completed, the first charge of the even-numbered battery cell 20B is started next. In the odd-numbered battery cell 20A, dissolution is also carried out naturally after the first charge is completed.

[0064] The even-numbered battery cell 20B is also charged similarly to the odd-numbered battery cell 20A. After the voltage of the even-numbered battery cell 20B is maintained at 3.75 (V) for 10 hours, the first charge is completed. When the first charge of the even-numbered battery cell 20B is completed, the second charge of the odd-numbered battery cell 20A is started. In the even-numbered battery cell 20B, dissolution also proceeds naturally after the first charge is completed.

[0065] After the second charge of the odd-numbered battery cell 20A is started and the voltage of the odd-numbered battery cell 20A is maintained at 3.75 (V) for 2.5 hours, the second charge is completed. When the second charge of the odd-numbered battery cell 20A is completed, the second charge of the even-numbered battery cell 20B is started. In the odd-numbered battery cell 20A, dissolution also proceeds naturally after the second charge is completed.

[0066] The even-numbered battery cell 20B also starts the second charge similarly to the odd-numbered battery cell 20A, and the voltage of the even-numbered battery cell 20B is maintained at 3.75 (V) for 2.5 hours before the second charge is completed. Moreover, in the even-numbered battery cell 20B, dissolution also proceeds naturally after the second charge is completed.

[0067] The third embodiment is different from the first and second embodiments described above. In the odd-numbered battery cells 20A and the even-numbered battery cells 20B of the third embodiment, charging is divided into two times. That is, the time for dissolution to proceed naturally is increased. As a result, in the odd-numbered battery cells 20A and the even-numbered battery cells 20B (odd-numbered battery cell group 30A and even-numbered battery cell group 30B), it takes 50 hours to dissolve the SUS foreign matter, and the time required for dissolving the SUS foreign matter is shortened by 8 hours compared to the first embodiment described above, and the time required for dissolving the SUS foreign matter is shortened by 7 hours compared to the second embodiment described above.

[0068] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the first to third embodiments described above will be described.

[0069] The manufacturing method of the bipolar secondary battery 100 of the first to third embodiments includes an aging charging process, in which an odd-numbered battery cell group 30A having a plurality of odd-numbered battery cells 20A adjacent to each other in the stacking direction and an even-numbered battery cell group 30B having a plurality of even-numbered battery cells 20B adjacent to the odd-numbered battery cells 20A included in the odd-numbered battery cell group 30A are alternately charged until a predetermined voltage is reached in the high-temperature aging process. In addition, in the aging charging process, the completion conditions of charging the odd-numbered battery cell group 30A and the even-numbered battery cell group 30B are determined based on the dissolution rate x calculated based on the type of the metal foreign matter and the positive electrode potential, the voltage V of each battery cell 20 in the aging charging process, and the aging time t.

[0070] As described above, the completion condition of charging is determined based on the dissolution rate x calculated according to the type of metal foreign matter and the positive electrode potential, the voltage V of each battery cell 20 in the charging process during aging, and the aging time t. Therefore, in the high-temperature aging process, compared with the prior art in which charging is completed under the completion conditions set in the battery cell 20 with the lowest voltage without considering the dissolution rate x of the foreign matter, the time required for charging to be completed can be shortened, thereby shortening the high-temperature aging time.

[0071] Furthermore, by taking into account the naturally progressing dissolution as in the second embodiment of the method for manufacturing the bipolar secondary battery 100 , the time required to complete charging can be further shortened compared to the first embodiment in which this is not taken into account, thereby further shortening the high temperature aging time.

[0072] Furthermore, by performing charging in multiple times as in the method for manufacturing the bipolar secondary battery 100 in the third embodiment, the time required to complete charging can be further shortened compared to the first and second embodiments in which charging is performed once, thereby further shortening the high temperature aging time.

[0073] Next, a method for manufacturing a bipolar secondary battery 100 according to a fourth embodiment is described below. In this embodiment, in the above-mentioned aging charging process, the battery cell 20 to be charged is charged multiple times. In this case, as a switching determination condition for switching charging, a switching charging capacity is set, and the switching charging capacity is a value smaller than the charging capacity at the last charge. Figure 7 1 is a diagram showing the switching determination condition of the charging capacity (mAh) with respect to the number of charging times in the odd-numbered battery unit 20A. The value of the charging capacity is set each time during charging, and is set to a value corresponding to the number of charging times.

[0074] Here, as an example, the positive electrode mixture layer 14 of the battery cell 20 is LFP, and the negative electrode mixture layer 16 is graphite. In addition, the initial charging conditions in the initial charging process are set to 25°C, 3.75V-CC charging, and a charging rate of 0.06C. In addition, the charging conditions in the aging charging process are set to 65°C, 3.75V-CC charging (SOC100%), and a charging rate of 0.0017C, and the charging rest conditions are set to 65°C, 10 hours, and the number of repeated charging is set to 20 times.

[0075] like Figure 7 As shown, as an example, in the odd-numbered battery cell 20A, if the switching judgment condition during the first charge is when the charging capacity of the battery cell becomes 0.5 (mAh), the switching judgment condition during the second charge is set to when the charging capacity of the battery cell becomes 0.1 (mAh) less than the charging capacity during the first charge. That is, during the second charge, when the charging is carried out until the charging capacity reaches 0.1 mAh, the charging is switched from the odd-numbered battery cell 20A to the even-numbered battery cell 20B. Similarly, after the third charge, a value smaller than the charging capacity during the previous charge will also be used as the switching judgment condition. That is, as Figure 7 As shown in FIG. 1 , the greater the number of times of charging, the smaller the value of the charging capacity that becomes the switching determination condition is set. Figure 7 In FIG. 1 , when the value of the charge capacity is greater than the value indicated by the solid line, the charge is switched from the odd-numbered battery cell 20A to the even-numbered battery cell 20B, or from the even-numbered battery cell 20B to the odd-numbered battery cell 20A. In other words, in Figure 7 In the figure, when the value of the charge capacity is smaller than the value indicated by the solid line, charging is continued until the value of the charge capacity exceeds the value indicated by the solid line.

[0076] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the fourth embodiment will be described.

[0077] In the bipolar secondary battery 100, during the charging of the battery cell 20 to be charged, the charging of the battery cells 20 that are not to be charged is suspended, and the electricity charged during the charging suspension period may disappear. Therefore, during the second and subsequent charging, the amount of electricity that disappeared during the charging waiting period is supplemented, so the charging capacity gradually decreases compared to the first charging. That is, the more times the charging is repeated, the closer it is to full charge, and therefore the charging capacity decreases.

[0078] In the manufacturing method of the bipolar secondary battery 100 in the fourth embodiment, a switching charge capacity is set as a switching judgment condition for switching the charging of the battery cell 20 to be charged, and the switching charge capacity is a value smaller than the charge capacity at the last charge. Therefore, in the aging charging process, the battery cell 20 to be charged is charged with a charge capacity corresponding to the number of times charged. This can prevent useless charging and shorten the time required to complete charging.

[0079] In addition, in the fourth embodiment, if Figure 7 As shown in FIG. 1 , the value of the charging capacity is set based on the number of charging times, but the present invention is not limited thereto. Instead of the charging capacity, the value of ΔSOC (%) may be set. Here, ΔSOC (%) is a set value represented by charging capacity (Ah) / battery cell capacity (Ah).

[0080] Next, a method for manufacturing a bipolar secondary battery 100 according to a fifth embodiment is described below. In the fourth embodiment, a switching charge capacity is set as a switching determination condition for switching charging, and the switching charge capacity is a value smaller than the charge capacity at the last charge. In contrast, in the present embodiment, a switching charge time is set as a switching determination condition for switching charging, and the switching charge time is a time shorter than the charge time at the last charge. Figure 8 1 is a diagram showing the switching judgment condition of the charging time (hr) to reach 3.75V in the odd-numbered battery cell 20A relative to the number of charging times. In addition, the value of the charging time is set each time during charging, and is set to a value corresponding to the number of charging times. In addition, the battery cell 20 of this embodiment adopts the same structure as the battery cell 20 of the fourth embodiment described above.

[0081] like Figure 8As shown, as an example, in the odd-numbered battery cell 20A, if the switching judgment condition during the first charge is that the charging time of the battery cell has reached 3.75V after 5 hours, the switching judgment condition during the second charge is set to the charging time of the battery cell being shorter than the charging time during the first charge by 3 hours. That is, during the second charge, when the charging time reaches 3 hours, the charging is switched from the odd-numbered battery cell 20A to the even-numbered battery cell 20B. Similarly, after the third charge, the charging time shorter than the charging time during the previous charge will also be used as the switching judgment condition. That is, if Figure 8 As shown in FIG. 1 , the greater the number of times of charging, the smaller the value of the charging time, which becomes the switching determination condition, is set. Figure 8 In FIG. 1 , when the charging time becomes longer than the value indicated by the solid line, charging is switched from the odd-numbered battery cell 20A to the even-numbered battery cell 20B, or from the even-numbered battery cell 20B to the odd-numbered battery cell 20A. In other words, Figure 7 In the case where the charging time is shorter than the value indicated by the solid line, charging is continued until the charging time becomes longer than the value indicated by the solid line.

[0082] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the fifth embodiment will be described.

[0083] In the bipolar secondary battery 100, during the charging of the battery cell 20 to be charged, the charging of the battery cells 20 that are not to be charged is suspended, and the electricity charged during the charging suspension period may disappear. Therefore, during the second and subsequent charging, the charge lost during the charging waiting period is supplemented, so the charging capacity gradually decreases compared to the first charging, and the charging time also gradually shortens. That is, the more times the charging is repeated, the closer to full charge, and therefore the charging time becomes shorter.

[0084] In the manufacturing method of the bipolar secondary battery 100 in the fifth embodiment, a switching charging time is set as a switching determination condition for switching the charging of the battery cell 20 to be charged, and the switching charging time is a time shorter than the charging time at the last charging. Therefore, in the aging charging process, the battery cell 20 to be charged is charged for a charging time corresponding to the number of charging times. This can prevent useless charging and shorten the time required to complete charging.

[0085] In addition, in the fifth embodiment, if Figure 8As shown in FIG. 1 , the value of the charging time to reach 3.75V is set according to the number of charging times, but the present invention is not limited to this. Instead of the charging time, the value of the charging time (h) at a 1C rate may be set. Here, the charging time (h) at a 1C rate is a set value represented by the charging time to reach 3.75V (hr) × 0.0017.

[0086] Next, the manufacturing method of the bipolar secondary battery 100 of the sixth embodiment is described below. In this embodiment, in the above-mentioned aging charging process, an abnormality determination condition is set to determine that the battery cell 20 to be charged is abnormal. The abnormality determination condition is a situation where the change in voltage relative to time deviates from a predetermined error range of the change. Here, the "error range" represents a value that can be used as a range from the lower limit to the upper limit of the error for the value of the change in voltage relative to time. Fig. 9 is a graph showing a charging curve of the relationship between voltage and charging time, Fig. 10A is a graph showing the amount of change in voltage with respect to time, Fig. 10B It is a graph showing the amount of change in voltage relative to the voltage. The battery cell 20 of the present embodiment has the same configuration as the battery cell 20 of the fourth embodiment described above.

[0087] Generally, when charging the battery cell 20, Fig. 9 As shown, the voltage value increases with a substantially constant change amount over time. However, as an example, when there is an extreme change in charging conditions, the change amount of the voltage may deviate from the normal range. For example, when a short circuit occurs in the battery cell 20, the voltage does not rise, so the change amount of the voltage becomes small.

[0088] Therefore, in this embodiment, in the aging charging process, the abnormality judgment condition of the battery cell 20 to be charged is set to a situation where at least one of the change in voltage relative to time or the change in voltage relative to voltage deviates from a predetermined error range of the change.

[0089] For example, in the case of the first charge at 0.0017C, Fig. 10A As shown, charging is performed with the voltage change amount indicated by the dotted line with respect to time. At this time, in this embodiment, when the voltage change amount is outside the error range of the value indicated by the dotted line, that is, outside the periphery of the dotted line, it is determined to be abnormal.

[0090] In addition, for example, when the first charge is performed at 0.0017C, Fig. 10BAs shown, charging is performed with respect to the voltage change amount indicated by the dotted line. At this time, in this embodiment, when the voltage change amount is outside the error range of the value indicated by the dotted line, that is, outside the periphery of the dotted line, it is determined to be abnormal.

[0091] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the sixth embodiment will be described.

[0092] In the manufacturing method of the bipolar secondary battery 100 in the sixth embodiment, in the aged charging process, the abnormality determination condition of the battery cell 20 to be charged is set to the case where at least one of the change amount of voltage relative to time or the change amount of voltage relative to voltage deviates from the predetermined error range of the change amount. Therefore, when the change amount of voltage deviates from the predetermined error range of the change amount, it is determined to be abnormal, so even if the inspection process is not performed, it is possible to detect defective products in the aged charging process.

[0093] In addition, in the sixth embodiment, if Fig. 10A as well as Fig. 10B As shown in FIG. 1 , the value of the voltage change is set relative to time or voltage, but the present invention is not limited thereto. Instead of the value of the voltage change, the value of the voltage change at the 1C rate may be set. Here, the voltage change at the 1C rate is a set value represented by the voltage change (V / sec) ÷ 0.0017.

[0094] Next, the manufacturing method of the bipolar secondary battery 100 of the seventh embodiment is described below. In the sixth embodiment, the abnormality determination condition is the case where the change amount of voltage relative to time and the change amount of voltage relative to voltage deviate from the predetermined error range of the change amount. In contrast, in the present embodiment, the abnormality determination condition is the case where the change amount of battery capacity relative to voltage deviates from the predetermined error range of the change amount. Fig.11 It is a graph showing the amount of change in battery capacity relative to voltage. The battery cell 20 of the present embodiment has the same configuration as the battery cell 20 of the fourth embodiment.

[0095] Generally, when charging the battery cell 20, Fig. 9 As shown, the voltage value increases with a substantially constant change amount over time. However, as an example, when there is an extreme change in charging conditions, the change amount of the voltage may deviate from the normal range, and thus the change amount of the battery capacity may also deviate from the normal range.

[0096] Therefore, in the present embodiment, in the deterioration charging step, the abnormality determination condition of the battery cell 20 to be charged is set as a case where the amount of change in battery capacity relative to voltage deviates from a predetermined error range of the amount of change.

[0097] For example, in the case of the first charge at 0.0017C, Fig.11 As shown, the battery capacity is charged with respect to the voltage represented by the solid line. At this time, in this embodiment, when the battery capacity change is outside the error range of the value represented by the solid line, that is, outside the periphery of the solid line, it is determined to be abnormal.

[0098] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the seventh embodiment will be described.

[0099] In the manufacturing method of the bipolar secondary battery 100 in the seventh embodiment, in the aged charging step, the abnormality determination condition of the battery cell 20 to be charged is set to the case where the amount of change in battery capacity relative to voltage deviates from the predetermined error range of the amount of change. Thus, when the amount of change in battery capacity deviates from the predetermined error range of the amount of change, it is determined to be abnormal, so that even if the inspection step is not performed, defective products can be detected in the aged charging step.

[0100] In addition, in the seventh embodiment, if Fig.11 As shown, the value of the change in battery capacity is set relative to the voltage, but the present invention is not limited to this. Instead of the value of the change in battery capacity, the value of the change in battery capacity of a battery capacity of 1Ah may be set. Here, the change in battery capacity of a battery capacity of 1Ah is a set value represented by the change in battery capacity of a battery capacity of 1mAh (mAh / V) ÷ 56. In addition, instead of the value of the change in battery capacity of a battery capacity of 1Ah, the value of the change in SOC may be set. Here, the change in SOC (%) is a set value obtained by converting the battery capacity (Ah) of a battery capacity of 1Ah into SOC (%).

[0101] Next, a method for manufacturing the bipolar secondary battery 100 according to the eighth embodiment will be described below. Fig.12 is a graph showing the relationship between the charging rest time and the voltage for each charging number. Fig.13 is a graph showing the relationship between the number of charge times and the voltage 2 hours after the charge is stopped. Fig.14 It is a graph showing the relationship between the number of times of charging and the voltage 10 hours after the charging is stopped. The battery cell 20 of this embodiment has the same structure as the battery cell 20 of the fourth embodiment.

[0102] like Fig.12 As shown in the figure, as an example, when the odd-numbered battery cell 20A is in a charging pause period during the charging of the even-numbered battery cell 20B, the voltage of the odd-numbered battery cell 20A decreases as the charging pause period of the odd-numbered battery cell 20A passes. At this time, the odd-numbered battery cell 20A charged 10 times is closer to full charge than the odd-numbered battery cell 20A charged only once, so the voltage decrease converges.

[0103] Therefore, in this embodiment, in the aged charging process, the abnormality determination condition during the charging suspension period of the battery cell 20 to be charged is set to be that the voltage after a predetermined time from the charging suspension is less than a predetermined voltage value set in advance for each charging number.

[0104] That is, as an example, Fig.13 The solid line in the middle shows the voltage after 2 hours of each charge number. Fig.14 The solid line in the middle indicates the voltage after 10 hours of each charge number. In addition, the specified value is set in consideration of the deviation. Moreover, at each charge, as an example, the voltage after at least one of 2 hours and 10 hours is measured. If the voltage is below the specified value of the voltage set for each charge number, it is determined to be abnormal because the voltage drops too much.

[0105] Next, the effects of the method for manufacturing the bipolar secondary battery 100 in the eighth embodiment will be described.

[0106] In the manufacturing method of the bipolar secondary battery 100 of the eighth embodiment, the abnormality determination condition during the charging suspension period of the battery cell 20 to be charged is set to the case where the voltage after a predetermined time period set in advance from the charging suspension is less than a predetermined value of the voltage set in advance for each number of charging times. Thus, when the voltage during the charging suspension period is less than the predetermined value of the voltage set in advance for each number of charging times, it is determined to be abnormal, so that even if the inspection process is not entered, defective products can be detected in the aging charging process.

[0107] [Remark]

[0108] In addition, in the above-mentioned embodiment, the charging completion condition is determined in both the odd-numbered battery cell 20A (i.e., the odd-numbered battery cell group 30A) and the even-numbered battery cell 20B (i.e., the even-numbered battery cell group 30B), but the present invention is not limited to this, and the effect of the present invention can also be obtained by only determining the completion condition of one of them.

[0109] In the present invention, the positive active material used in the positive electrode mixture layer 14 as the positive electrode is not limited, but lithium iron phosphate ions are preferably used. Lithium iron phosphate has a steeper voltage drop near the dissolution potential of foreign matter, so the effect of the present invention is more easily obtained.

[0110] In the above embodiment, SUS such as SUS304 is used as an example of a foreign matter that can be assumed, but the present invention is not limited thereto. For example, copper or the like contained in the current collector 12 can also be assumed as a foreign matter.

[0111] In addition, the configuration of the present disclosure is not limited to the above-described embodiment, and the configuration can be appropriately changed as long as the problem can be solved.

Claims

1. A method for manufacturing a bipolar secondary battery, wherein a plurality of battery cells including a positive electrode, a negative electrode and an electrolyte layer are stacked, the method for manufacturing a bipolar secondary battery comprising: an initial charging step of charging a first battery cell group including a plurality of battery cells adjacent to each other in a stacking direction and a second battery cell group including a plurality of battery cells adjacent to the battery cells included in the first battery cell group to a predetermined voltage; A high temperature aging process in which aging is performed at a temperature higher than normal temperature; as well as In the high temperature aging step, the first battery cell group and the second battery cell group are alternately charged until a predetermined voltage is reached, In the aging charging process, the completion condition of charging of at least one of the first battery cell group and the second battery cell group is determined based on the dissolution rate calculated according to the type of metal foreign matter and the positive electrode potential, and the voltage and aging time of each of the battery cells in the aging charging process.

2. The method for manufacturing a bipolar secondary battery according to claim 1, characterized in that: In the aging charging step, a switching charging capacity or a switching charging time is set as a switching determination condition for switching charging of the battery cell to be charged. The switching charging capacity is a value smaller than the charging capacity at the last charging. The switching charging time is a time shorter than the charging time in the previous charging.

3. The method for manufacturing a bipolar secondary battery according to claim 1, characterized in that: In the aging charging process, the abnormal judgment condition for judging the battery cell to be charged as abnormal is set to a situation where at least one of the change in voltage relative to time and the change in battery capacity relative to voltage deviates from a predetermined error range of the change.

4. The method for manufacturing a bipolar secondary battery according to claim 1, characterized in that: In the aged charging process, the abnormality determination condition during the charging suspension period of the battery cell to be charged is that the voltage after a predetermined time period set in advance from the charging suspension is equal to or less than a predetermined voltage value set in advance for each charging number.

5. The method for manufacturing a bipolar secondary battery according to claim 1, characterized in that: The positive electrode uses lithium iron phosphate as a positive electrode active material.

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