Manufacturing method of secondary battery

Abstract

To solve a problem where a conventional manufacturing method of a secondary battery cannot sufficiently reduce a defective fraction.SOLUTION: A manufacturing method of a secondary battery of the present invention performs: a first aging step S2 of performing an aging treatment of a battery cell while maintaining a first temperature and a first output voltage for a preset first time; a second aging step S3 of performing an aging treatment of the battery cell while maintaining a second temperature that is higher than the first temperature and a preset second output voltage for a preset second time; a self discharge step S4 of determining a magnitude of a self discharge amount of the battery cell; a defective fraction confirmation step S6 of determining whether or not the battery cell has a good quality on the basis of the self discharge amount, and confirming the defective fraction caused by a self discharge amount failure at the time; and an aging condition update step S7 of performing an aging condition update for increasing and reducing the first temperature and the first output voltage on the basis of a defective factor of the battery cell that is determined as a defective fraction in the case where the defective fraction exceeds a preset reference defective fraction.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for producing a non-aqueous electrolyte secondary battery, such as a lithium ion secondary battery. [Background technology]

[0002] In non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, metallic foreign matter mixed into the positive electrode active material layer and the negative electrode active material layer may dissolve into the electrolyte during charging and discharging of the battery cell, and the dissolved metallic foreign matter may precipitate on the active material layer on the opposite side, causing the precipitated metallic foreign matter to grow in a spike shape. When the metallic foreign matter that has grown in a spike shape reaches the active material layer on the opposite side, a micro-short circuit occurs between the positive and negative electrodes, causing a problem of an increase in the self-discharge amount of the battery cell. Thus, methods for preventing such micro-short circuits caused by the precipitation of metallic foreign matter are disclosed in Patent Documents 1 and 2.

[0003] In the method for manufacturing a secondary battery described in Patent Document 1, the battery body is subjected to a low-temperature aging treatment at a temperature of 10°C for 2 hours, for example, and then a first room-temperature aging treatment at a temperature of 20°C for 8 hours. After that, the battery body is subjected to a partial charging treatment, and then a high-temperature aging treatment at a temperature of 50°C for 12 days, for example. After that, the battery body is subjected to an activation treatment for 4.5 hours, for example, and then left for a predetermined time. After that, the battery body is subjected to a second room-temperature aging treatment at a temperature of 23°C for 28 days, for example, and then the current capacity during charging and discharging is inspected. After that, the battery body is left for a predetermined time, and then the battery body is subjected to, for example, a printing treatment, an OCV measurement, and a tubing treatment to make it into a product, and then these batteries are ranked based on the cell information and shipped by rank.

[0004] The method for producing a non-aqueous electrolyte secondary battery described in Patent Document 2 includes the steps of: constructing a battery assembly using a positive electrode, a negative electrode, and a non-aqueous electrolyte; initially charging the battery assembly; a low-temperature aging step of leaving the battery assembly after the initial charging at a temperature of 15°C or higher and 30°C or lower for 6 hours or more; a high-temperature aging step of leaving the battery assembly after the low-temperature aging step at 60°C for at least 20 hours; and allowing the battery assembly after the high-temperature aging step to self-discharge. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-289729 [Patent Document 2] JP 2017-22067 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the foreign metals mixed into the battery cell contain multiple metal species with different dissolution rates, performing aging treatments multiple times under conditions suited to one of the metal species causes spikes due to the foreign metals of the other metal species to grow, resulting in a micro-short circuit between the positive electrode active material layer and the negative electrode active material layer. In other words, in the documents 1 and 2, there is a problem in that the defect rate cannot be sufficiently reduced when the foreign metals contain multiple metal species with different dissolution rates.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to efficiently reduce the defect rate even when metal foreign matter contains multiple metal types with different dissolution rates. [Means for solving the problem]

[0008] One aspect of a manufacturing method for a secondary battery according to the present invention includes a charging step of charging a battery cell to a predetermined specified charging rate, a first aging step of maintaining the battery cell charged in the charging step at a first temperature and a first output voltage and performing an aging process for a predetermined first time, a second aging step of maintaining the battery cell after the first aging step at a second temperature higher than the first temperature and at a predetermined second output voltage and performing an aging process for a predetermined second time, a self-discharge step of determining the magnitude of a self-discharge amount of the battery cell after the second aging step, a defect rate confirmation step of determining whether the battery cell is a pass / fail product based on the self-discharge amount and confirming a defect rate due to a self-discharge amount defect at that time, and an aging condition update step of updating an aging condition by increasing or decreasing the first temperature and the first output voltage based on a cause of defect of the battery cell determined to be defective if the defect rate exceeds a predetermined standard defect rate.

[0009] Another aspect of the method for manufacturing a secondary battery according to the present invention includes a charging step of charging a battery cell to a predetermined specified charging rate, a first aging step of maintaining the battery cell charged in the charging step at a first temperature and a first output voltage and performing an aging treatment for a predetermined first time, and a second aging step of maintaining the battery cell after the first aging step at a second temperature higher than the first temperature and a predetermined second output voltage and performing an aging treatment for a predetermined second time, wherein the first aging step includes a first sub-aging step of performing aging at a temperature and output voltage that promote dissolution of a first metallic foreign matter among metallic foreign matter mixed in an active material layer of the battery cell, and a second sub-aging step of performing aging to promote dissolution of a second metallic foreign matter among the metallic foreign matter by maintaining at least one of the temperature and the output voltage at a value higher than that of the first sub-aging step. Effect of the Invention

[0010] According to the method for producing a secondary battery of the present invention, the defect rate can be reduced even when the foreign metal matter contains a plurality of metal species with different dissolution rates. [Brief description of the drawings]

[0011] [Figure 1] 1 is a graph illustrating differences in dissolution rate depending on metal type. [Diagram 2] FIG. 2 is a diagram illustrating a first aspect of dissolution and precipitation of metallic foreign matter during aging treatment. [Diagram 3] FIG. 11 is a diagram illustrating a second aspect of dissolution and precipitation of metallic foreign matter during aging treatment. [Figure 4] FIG. 11 is a diagram illustrating a third aspect of dissolution and precipitation of metallic foreign matter during aging treatment. [Diagram 5] 11 is a graph illustrating a difference in dissolution current due to differences in temperature and output voltage conditions during aging. [Figure 6] 4 is a table for explaining differences in aging conditions and defect rates in the manufacturing method for the secondary battery according to the first embodiment. [Figure 7] 5 is a diagram for explaining the defect rate in the manufacturing method for the secondary battery according to the first embodiment and the conditions under which an aging condition change process is performed. FIG. [Figure 8] 4 is a flowchart illustrating a flow of a method for manufacturing a secondary battery according to the first embodiment. [Figure 9] 1 is a flowchart illustrating a flow of an aging condition updating process according to the first embodiment. [Figure 10] 10 is a flowchart illustrating a flow of a method for manufacturing a secondary battery according to a second embodiment. [Figure 11] 13 is a flowchart illustrating a flow of an aging condition updating process according to the second embodiment. [Figure 12] 11 is a flowchart illustrating a flow of a method for manufacturing a secondary battery according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In order to clarify the description, the following description and drawings are omitted and simplified as appropriate. In addition, each element shown in the drawings as a functional block performing various processes can be configured in hardware with a CPU (Central Processing Unit), memory, and other circuits, and in software, can be realized by a program loaded into memory. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware alone, software alone, or a combination thereof, and are not limited to any one of them. In addition, the same elements are given the same symbols in each drawing, and duplicated explanations are omitted as necessary.

[0013] Moreover, the above-mentioned program includes a set of instructions (or software code) for making the computer perform one or more functions described in the embodiment when the program is read into the computer. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or the tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, the transitory computer-readable medium or the communication medium includes electrical, optical, acoustic, or other forms of propagating signals.

[0014] In addition, the battery utilization method according to the first embodiment described below is performed by an automatic process in which multiple programs executed on separate computers are prepared for each process in the flow of battery utilization in cooperation with each other.

[0015] First embodiment The manufacturing method of the secondary battery according to the first embodiment described below aims to prevent spikes caused by foreign metal particles having different dissolution rates in the electrolyte and to improve the reliability of the battery cell. Here, the problems caused by the dissolution rates of foreign metal particles will be described in detail.

[0016] Figure 1 shows a graph that explains the difference in dissolution rate depending on the type of metal. In the example shown in Figure 1, the difference in the potential difference between the positive and negative electrodes and the dissolution rate in the electrolyte for copper (Cu), iron (Fe), and stainless steel (SUS) as metal types of foreign metal that may be mixed into a cell is shown. As shown in Figure 1, it can be seen that for all metal types, the dissolution rate changes exponentially as the potential difference between the positive and negative electrodes increases. However, the dissolution rates of copper and iron are faster with a steeper slope relative to the potential difference between the positive and negative electrodes than the dissolution rate of stainless steel.

[0017] Here, the relationship between the dissolution rate of the metallic foreign matter and the growth of the spikes formed by the precipitated metal will be described with reference to Figures 2 to 4. Figures 2 to 4 show a schematic diagram of how the metallic foreign matter OBJ attached to the positive electrode active material layer 11 applied to the positive electrode foil 10 becomes a metal ion derived from the metallic foreign matter OBJ dissolved in the electrolyte soaked into the separator between the positive electrode active material layer 11 and the negative electrode active material layer 13, and precipitates as a spike caused by the metallic foreign matter OBJ on the negative electrode active material layer 13 applied to the negative electrode foil 12.

[0018] FIG. 2 is a diagram illustrating a first mode of dissolution and precipitation of metallic foreign matter in an aging treatment. This first mode is an example in which metallic foreign matter OBJ is dissolved at a high dissolution rate in order to completely dissolve the metallic foreign matter OBJ within a limited time. As shown in FIG. 2, in the first mode, the area over which the metallic ions diffuse into the negative electrode active material layer 13 is small, and the metallic ions are rapidly precipitated on the negative electrode active material layer 13 side, so that the height of the spike becomes large and reaches the positive electrode active material layer 11. Then, this spike short-circuits the positive electrode active material layer 11 and the negative electrode active material layer 13. This short-circuit increases the self-discharge amount of the battery cell.

[0019] FIG. 3 is a diagram illustrating a second aspect of dissolution and precipitation of metallic foreign matter in an aging treatment. This second aspect is an example in which metallic foreign matter OBJ is completely dissolved by two aging treatments (for example, a first aging treatment and a second aging treatment) with different dissolution rates. As shown in FIG. 3, in the second aspect, metallic foreign matter OBJ is dissolved at a slow dissolution rate in the first aging treatment, so that metal ions reach the negative electrode active material layer 13 in a state of being widely diffused in the negative electrode active material layer 13. Therefore, the height of spikes caused by metal ions precipitated on the negative electrode active material layer 13 is reduced. Then, in the second aspect, aging is performed at a fast dissolution rate in the second aging treatment to completely dissolve metallic foreign matter OBJ. In this second aging treatment, since there is little metallic foreign matter OBJ remaining in the first aging treatment, the growth of the spikes in the height direction is suppressed, and no short circuit caused by the spikes occurs.

[0020] FIG. 4 is a diagram illustrating a third aspect of dissolution and precipitation of metallic foreign matter in an aging treatment. In the third aspect, the dissolution rate of metallic foreign matter OBJ in the first aging treatment of the second aspect is further slowed. As shown in FIG. 4, even if a multi-stage aging treatment is performed, if the dissolution rate in the first aging treatment is set too slow, the amount of metallic foreign matter OBJ remaining attached to the positive electrode active material layer 11 at the completion of the first aging treatment increases even if the growth of the spike originating from the metallic foreign matter OBJ precipitated in the negative electrode active material layer 13 in the first aging treatment is suppressed. Therefore, in the third aspect, the growth amount of the spike in the second aging treatment, which is set under conditions to achieve a fast dissolution rate, becomes large, and a short circuit occurs between the positive electrode active material layer 11 and the negative electrode active material layer 13.

[0021] Thus, in order to prevent short circuits between plates caused by metallic foreign objects OBJ during the aging process, it is important to determine the dissolution rate at which the metallic foreign objects OBJ are dissolved during the aging process. In addition to the output voltage of the battery cell during the aging process, the temperature at which the battery cell is controlled is also important for this dissolution rate. Figure 5 shows a graph that explains the difference in dissolution current due to differences in temperature and output voltage conditions during aging.

[0022] The graph shown in FIG. 5 is a graph in which the horizontal axis indicates temperature (1000 / T [K], T is temperature in Kelvin) and the vertical axis indicates a dissolution current that is correlated with the dissolution rate of the metallic foreign body OBJ. The graph shown in FIG. 5 is related to stainless steel, which is assumed to be one type of metallic foreign body OBJ. As shown in FIG. 5, the dissolution rate of the metallic foreign body OBJ increases as the temperature increases. It can also be seen that the dissolution rate increases as the output voltage of the battery cell increases. In other words, it can be seen that the dissolution rate of the metallic foreign body OBJ increases as the temperature and output voltage are increased. It can also be seen from the graph shown in FIG. 5 that, for example, a rough range of the dissolution rate is set by the output voltage of the battery cell, and the dissolution rate can be controlled more finely within the range of the dissolution rate by the temperature.

[0023] Here, we will explain the change in the defect rate when the aging conditions of the first aging process performed first in the process of performing two aging processes are changed. Fig. 6 shows a table explaining the difference between the aging conditions and the defect rate in the manufacturing method of the secondary battery according to the first embodiment. Fig. 6 is a table comparing the difference in the defect rate caused by the difference in the first aging conditions performed in the first half for each metal type of the metallic foreign matter OBJ, with copper (Cu), iron (Fe) and stainless steel (SUS) mixed into the battery cell as metallic foreign matter OBJ, and with the second aging conditions in the latter half set to a temperature of 60 and an output voltage of 3.9V.

[0024] As shown in Figure 6, for copper and iron, which melt easily even at low temperatures and output voltages, the defect rate is OK when aging at a temperature of 15°C and an output voltage of 3.7V, but when aging at higher temperatures and output voltages of 40°C and 3.8V, the defect rate is high and the result is NG. On the other hand, for stainless steel, which does not melt easily at low temperatures and output voltages, the defect rate is high and the result is NG when aging at a temperature of 15°C and an output voltage of 3.7V, but when aging at higher temperatures and output voltages of 40°C and 3.8V, the defect rate is low and the result is OK.

[0025] In other words, for copper and iron, spikes with the shape shown in Figure 2 are formed under aging conditions of low temperature and output voltage, while for stainless steel, spikes with the shape shown in Figure 2 are not formed unless the aging conditions are low temperature and output voltage.

[0026] Here, the table in Figure 6 shows the result of the judgment of OK or NG for the defect rate. The average value of the occurrence rate of defects (defect rate) caused by the self-discharge amount not conforming to the standard due to the deposition of metallic foreign matter OBJ is set as Ave, and the judgment criterion (defect rate) is whether the defect rate at the time of inspection is maintained at less than 1σ below the average defect rate Ave. <Ave+1σ)としたものである。

[0027] Here, a relationship between the defect rate and whether or not to perform an aging condition update process in the manufacturing method for a secondary battery according to the embodiment 1 will be described below. Fig. 7 shows a diagram for explaining the defect rate and the conditions for performing the aging condition change process in the manufacturing method for a secondary battery according to the embodiment 1.

[0028] 7, when the average value of the occurrence rate of defects (defective rate) caused by deviation from the standard of the self-discharge amount due to the precipitation of metallic foreign matter OBJ is taken as Ave, the occurrence frequency of each defective rate value is approximately normal distribution. In the manufacturing method of the secondary battery according to the first embodiment, when a defective rate higher than the average defective rate Ave by 1σ or more appears, the aging conditions of the first aging step (change of the control conditions of the dissolution rate) are implemented.

[0029] A manufacturing method of a secondary battery according to the first embodiment will be described in detail. FIG. 8 shows a flowchart for explaining the flow of the manufacturing method of a secondary battery according to the first embodiment. The manufacturing method of a secondary battery according to the first embodiment includes many steps such as battery assembly, aging, and others, but the flowchart shown in FIG. 8 only illustrates the aging step among these manufacturing steps. As shown in FIG. 8, the aging step according to the first embodiment includes a charging step (for example, an initial charging step S1, a first aging step S2, a second aging step S3, a self-discharge determination step S4, a battery characteristics inspection step S5, a defect rate confirmation step S6, and an aging condition update step S7.

[0030] In the initial charging step S1, the battery cell is charged to a predetermined specified charging rate. In the first aging step S2, the battery cell charged in the initial charging step S1 is maintained at a first temperature and a first output voltage, and aging is performed for a predetermined first time. In the second aging step S3, the battery cell after the first aging step S2 is maintained at a second temperature higher than the first temperature and at a predetermined second output voltage, and aging is performed for a predetermined second time. In the self-discharge determination step S4, the amount of self-discharge of the battery cell after the second aging step S3 is determined. In this self-discharge determination step S4, if the amount of self-discharge is greater than a predetermined reference value, the battery cell is determined to be defective, and the battery cell determined to be defective is excluded from the aging step as a defective product. In the battery characteristic inspection step S5, the characteristics of the battery cell, such as the battery capacity and battery resistance, of the battery determined to be a pass product in the self-discharge determination step S4 are inspected and recorded.

[0031] In the aging process according to the first embodiment, a defect rate confirmation step S6 and an aging condition update step S7 are performed. In the defect rate confirmation step S6, the defect rate caused by defective self-discharge amount at that time is confirmed based on the number of battery cells determined to be defective in the self-discharge determination step S4. Specifically, it is determined whether the defect rate is maintained at less than the average defect rate Ave +1σ. Then, in the aging condition update step S7, if the defect rate exceeds a previously prepared reference defect rate (average defect rate Ave +1σ), the aging conditions of the first aging process S2, that is, the first temperature and the first output voltage, are updated based on the cause of the defect of the battery cells determined to be defective.

[0032] Here, the aging condition update process S7 will be described in more detail. Fig. 9 shows a flow chart for explaining the flow of the aging condition update process S7 according to the first embodiment. In the aging condition update process S7, the direction of increase or decrease of the first temperature and the first output voltage is determined according to the type of metallic foreign matter that has caused a short circuit between at least the positive electrode active material layer and the negative electrode active material layer in the battery cell as a cause of the battery cell failure. More specifically, in the aging condition update process S7, if the metallic foreign matter is a first metal type that is easily dissolved (e.g., copper or iron), the first temperature and the first output voltage set in the first aging process S2 are updated so as to slow down the speed at which the metallic foreign matter dissolves, and if the metallic foreign matter is a second metal type that is less easily dissolved (e.g., stainless steel), the first temperature and the first output voltage set in the first aging process S2 are updated so as to speed up the speed at which the metallic foreign matter dissolves.

[0033] As shown in FIG. 9, in the aging condition update step S7 according to the first embodiment, a defect rate determination step S10, a metallic foreign matter determination step S11, a first condition update step S12, and a second condition update step S13 are performed. In the defect rate determination step S10, it is determined whether or not the current defect rate calculated in the defect rate confirmation step S6 is equal to or greater than the average defect rate Ave+1σ. If it is determined in the defect rate determination step S10 that the current defect rate is less than the average defect rate Ave+1σ, the process ends without updating the aging conditions. On the other hand, if it is determined in the defect rate determination step S10 that the current defect rate is equal to or greater than the average defect rate Ave+1σ, the metallic foreign matter determination step S11 is performed. In the metallic foreign matter determination step S11, for example, an inspection is performed on the battery cells determined to be defective, and it is determined whether or not the metal type constituting the spike is copper or iron. This inspection may be a destructive inspection or a non-destructive inspection.

[0034] If the metallic foreign matter determining step S11 determines that the metallic foreign matter causing the defect is copper or iron, a first condition updating step S11 is performed in which at least one of the first temperature and the first output voltage set in the first aging step S2 is increased to change the aging conditions so as to slow down the dissolution rate of the metallic foreign matter. On the other hand, if the metallic foreign matter determining step S11 determines that the metallic foreign matter causing the defect is stainless steel, a second condition updating step S12 is performed in which at least one of the first temperature and the first output voltage set in the first aging step S2 is decreased to change the aging conditions so as to speed up the dissolution rate of the metallic foreign matter.

[0035] As described above, in the method for producing a secondary battery according to the first embodiment, after the first aging step S2 in which the metallic foreign matter is dissolved is performed, the second aging step S3 in which the dissolution rate is set faster than that of the first aging step S2 is performed. Then, in the method for producing a secondary battery according to the first embodiment, the aging conditions of the first aging step S2 are updated to adjust the dissolution rate according to the cause of the defect and the metal type of the metallic foreign matter. As a result, in the method for producing a secondary battery according to the first embodiment, even if metallic foreign matter with a different dissolution rate is mixed in, the defective rate can be reduced and the production efficiency of secondary batteries can be improved.

[0036] Embodiment 2 In the embodiment 2, a description will be given of another embodiment of the method for manufacturing a secondary battery according to the embodiment 1. In the description of the embodiment 2, the parts described in the embodiment 1 will be denoted by the same reference numerals as in the embodiment 1, and the description thereof will be omitted.

[0037] Fig. 10 shows a flowchart for explaining the flow of the manufacturing method (aging step) of the secondary battery according to the second embodiment. As shown in Fig. 10, in the aging step according to the second embodiment, a first sub-aging step S21 and a second sub-aging step S22 are performed as the first aging step S2. Also, corresponding to the first sub-aging step S21 and the second sub-aging step S22, an aging condition updating step S27 is performed instead of the aging condition updating step S7.

[0038] The first sub-aging process S21 performs aging while maintaining a temperature and output voltage that promote dissolution of a first foreign metal substance (e.g., copper or iron) among the foreign metal substances that caused the defects. The second sub-aging process S22 performs aging while maintaining at least one of the temperature and output voltage at a higher value than the first sub-aging process S21, promoting dissolution of a second foreign metal substance (e.g., stainless steel) that is less likely to dissolve than the first foreign metal substance among the foreign metal substances that caused the defects.

[0039] In the aging condition updating process S27, if the metallic foreign object is a first metallic foreign object, the temperature and output voltage set in the first sub-aging process S21 are updated so as to slow down the dissolution of the first metallic foreign object, and in the aging condition updating process S27, if the metallic foreign object is a second metallic foreign object, the temperature and output voltage set in the second sub-aging process are updated so as to slow down the dissolution of the second metallic foreign object.

[0040] Here, the aging condition updating step S27 will be described in detail. Fig. 11 shows a flowchart explaining the flow of the aging condition updating step S27 according to the second embodiment. As shown in Fig. 11, in the aging condition updating step S27, a first condition updating step S32 and a second condition updating step S33 are performed instead of the first condition updating step S12 and the second condition updating step S13 of the aging condition updating step S7 shown in Fig. 9.

[0041] The first condition update process S32 is performed when the metal type of the foreign metal that caused the defect is determined to be copper or iron in the foreign metal determination process S11, and changes the aging conditions by lowering at least one of the temperature and output voltage set in the first sub-aging process S21 so as to slow down the dissolution rate of the first foreign metal (e.g., copper or iron).

[0042] The second condition update process S32 is performed when the metal type of the metallic foreign matter causing the defect is determined to be stainless steel in the metallic foreign matter determination process S11, and changes the aging conditions by lowering at least one of the temperature and output voltage set in the second sub-aging process S22 so that the dissolution rate of the second metallic foreign matter (e.g., stainless steel) is slowed or accelerated.

[0043] From the above description, in the method for producing a secondary battery according to the second embodiment, two aging processes are carried out in the first aging step S2: a first sub-aging step S21 for the easily soluble first foreign metal and a second sub-aging step S22 for the less soluble second foreign metal. This makes it possible to deal with each of the foreign metals that caused the defects, and therefore makes it possible to reduce the defect rate more efficiently than in the method for producing a secondary battery according to the first embodiment.

[0044] Third embodiment In the embodiment 3, a description will be given of another embodiment of the method for manufacturing a secondary battery according to the embodiment 2. In the description of the embodiment 3, the parts described in the embodiments 1 and 2 will be denoted by the same reference numerals as in the embodiment 1, and the description thereof will be omitted.

[0045] FIG. 12 shows a flow chart for explaining the flow of the manufacturing method (aging step) of the secondary battery according to the third embodiment. As shown in FIG. 12, the aging step according to the third embodiment is obtained by omitting the defective rate confirmation step S6 and the aging condition update step S27 of the aging step according to the second embodiment shown in FIG. 10. If the aging conditions that can sufficiently reduce the defective rate are clear in the three aging steps of the first aging step S2 including the first sub-aging step S21 and the second sub-aging step S22 and the second aging step S3, the defective rate can be sufficiently reduced even if the pass rate confirmation step S6 and the aging condition update step S27 are omitted. Furthermore, by not performing the pass rate confirmation step S6 and the aging condition update step S27, it is possible to simplify the process.

[0046] In the first aging step S2, it is preferable that the sub-aging step corresponding to the more soluble metal species is carried out earlier in the process.

[0047] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.

[0048] (Appendix 1) a charging step of charging the battery cell to a preset specified charging rate; a first aging step of performing an aging process on the battery cell charged in the charging step for a preset first time while maintaining the battery cell at a first temperature and a first output voltage; a second aging process in which the battery cell after the first aging process is maintained at a second temperature higher than the first temperature and at a preset second output voltage, and an aging process is performed for a preset second time, The first aging step includes: a first sub-aging step of performing aging while maintaining a temperature and an output voltage that promote dissolution of a first metallic foreign matter among the metallic foreign matter mixed in the active material layer of the battery cell; a second sub-aging step of performing aging to promote dissolution of a second metallic foreign matter among the metallic foreign matter by maintaining at least one of a temperature and an output voltage at a higher value than in the first sub-aging step; A method for manufacturing a secondary battery having the above structure. [Explanation of symbols]

[0049] 10 Positive electrode foil 11 Cathode active material layer 12 Negative electrode foil 13 Negative electrode active material layer OBJ Metal foreign object

Claims

1. a charging step of charging the battery cell to a preset specified charging rate; a first aging step of performing an aging process on the battery cell charged in the charging step for a preset first time while maintaining the battery cell at a first temperature and a first output voltage; a second aging process in which the battery cell after the first aging process is maintained at a second temperature higher than the first temperature and at a second output voltage set in advance, and an aging process is performed for a second time set in advance; a self-discharge step of determining a magnitude of a self-discharge amount of the battery cell after the second aging step; a defect rate confirmation step of determining whether the battery cell is a non-defective product based on the self-discharge amount and confirming a defect rate caused by a self-discharge amount defect at that time; an aging condition updating step of updating an aging condition by increasing or decreasing the first temperature and the first output voltage based on a cause of the defect of the battery cell determined to be defective when the defect rate exceeds a predetermined reference defect rate; A method for manufacturing a secondary battery comprising the steps of:

2. 2. The method for manufacturing a secondary battery according to claim 1, wherein in the aging condition updating process, a direction of increase or decrease of the first temperature and the first output voltage is determined according to a type of metallic foreign matter that has caused a short circuit between at least a positive electrode active material layer and a negative electrode active material layer in the battery cell as the cause of the defect of the battery cell.

3. 3. The method for manufacturing a secondary battery according to claim 2, wherein in the aging condition updating step, if the metallic foreign object is copper or iron, the first temperature and the first output voltage are updated so as to slow down a rate at which the metallic foreign object dissolves, and if the metallic foreign object is stainless steel, the first temperature and the first output voltage are updated so as to increase a rate at which the metallic foreign object dissolves.

4. The first aging step includes: a first sub-aging step of performing aging while maintaining a temperature and an output voltage that promote dissolution of a first metallic foreign matter among the metallic foreign matters that caused the defect; a second sub-aging step in which at least one of a temperature and an output voltage is maintained at a higher value than in the first sub-aging step, thereby performing aging to promote dissolution of second metallic foreign matter, which is less likely to dissolve than the first metallic foreign matter, among the metallic foreign matter causing the defect; The method for producing a secondary battery according to claim 1 , comprising:

5. In the aging condition updating step, If the metallic foreign matter is the first metallic foreign matter, updating the temperature and the output voltage set in the first sub-aging step so as to slow down the dissolution of the first metallic foreign matter; 5. The method for producing a secondary battery according to claim 4, wherein, when the metallic foreign matter is the second metallic foreign matter, the temperature and the output voltage set in the second sub-aging step are updated so as to slow down the dissolution of the second metallic foreign matter.

6. 6. The method for manufacturing a secondary battery according to claim 5, wherein the first foreign metal matter is copper or iron, and the second foreign metal matter is stainless steel.

7. a charging step of charging the battery cell to a preset specified charging rate; a first aging step of performing an aging process on the battery cell charged in the charging step for a preset first time while maintaining the battery cell at a first temperature and a first output voltage; a second aging process in which the battery cell after the first aging process is maintained at a second temperature higher than the first temperature and at a second output voltage set in advance, and an aging process is performed for a second time set in advance; The first aging step includes: a first sub-aging step of performing aging while maintaining a temperature and an output voltage that promote dissolution of a first metallic foreign matter among the metallic foreign matter mixed in the active material layer of the battery cell; a second sub-aging step of performing aging to promote dissolution of second metallic foreign matter among the metallic foreign matter by maintaining at least one of a temperature and an output voltage at a value higher than that in the first sub-aging step; A method for manufacturing a secondary battery having the above structure.

Images