Inspection method for lithium ion storage devices and manufacturing method for device group

Abstract

To provide a method for inspecting a lithium-ion power storage device that makes it possible to predict the progress of deterioration, and a method for manufacturing a group of devices that are less susceptible to deterioration using this inspection method.SOLUTION: A method for inspecting a lithium-ion power storage device 1, including an electrode body 2 that includes an electrolyte 6, a positive electrode plate 3 having a positive electrode active material layer 3A, a negative electrode plate 4 having a coated negative electrode active material layer 4A on which a Li-containing SEI coating 4AC containing lithium is formed, and a separator 5, and is permeated with the electrolyte 6, and a case 7 accommodating the electrode body 2 and the electrolyte 6, includes a negative electrode plate removal step S4 of dismantling the lithium-ion power storage device 1 and removing the negative electrode plate 4, a removal step S5 of washing and removing the electrolyte 6 adhering to the removed negative electrode plate 4, and a Li amount distribution acquisition step S6 of examining the distribution of Li amount AL contained in the Li-containing SEI coating 4AC of the coated negative electrode active material layer 4A.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting a lithium ion electricity storage device and a method for manufacturing a group of devices using the same. [Background technology]

[0002] When manufacturing an electricity storage device such as a lithium ion secondary battery, it is preferable to be able to predict deterioration. Patent Document 1 discloses a battery deterioration prediction system that can improve the accuracy of prediction of deterioration of a secondary battery through which a large current flows. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-007946 Summary of the Invention [Problem to be solved by the invention]

[0004] As adopted in Patent Document 1, secondary batteries are evaluated based on the magnitude of battery capacity and battery resistance. However, it has been found that even batteries with good battery capacity and resistance values ​​may experience significant deterioration with subsequent use (repeated charging and discharging) compared to other batteries. The reason for this is that batteries with localized performance unevenness in the electrode body will experience more localized deterioration with use than batteries with almost no localized performance unevenness in the electrode body, which is thought to result in more deterioration across the entire battery. However, localized performance unevenness in the electrode body cannot be detected by measuring the average characteristics of the entire battery, such as battery capacity and battery resistance.

[0005] Therefore, the present inventors conducted an investigation to find a new method for evaluating batteries and found that one of the causes of localized performance unevenness in an electrode assembly is that the amount (thickness) of the SEI coating formed on the negative electrode active material particles varies depending on the location of the negative electrode active material layer in the negative electrode plate used in the electrode assembly. Specifically, it was found that if the negative electrode active material layer contains locations where the amount of SEI coating is locally greater (thicker) or less (thinner) than locations where the SEI coating is average, then with subsequent use of the battery, deterioration will progress in the locations where the SEI coating is greater and less than the location where the SEI coating is average, and deterioration will also progress when viewed from the perspective of the battery as a whole.

[0006] The present invention has been made in light of this knowledge, and provides a method for inspecting lithium ion storage devices that makes it possible to predict the degree of deterioration, and a method for manufacturing a group of devices that are less likely to deteriorate using this inspection method. [Means for solving the problem]

[0007] (1) One aspect of the present invention to solve the above problem is: Contains lithium An inspection method for a lithium ion electricity storage device comprising: an electrolyte; a positive electrode plate having a positive electrode active material layer; a negative electrode plate having a coated negative electrode active material layer on which a Li-containing SEI coating containing lithium is formed; and an electrode assembly having a separator interposed between the positive electrode active material layer and the coated negative electrode active material layer, the electrode assembly being permeated with the electrolyte; and a case accommodating the electrode assembly and the electrolyte, a degradation step of subjecting the lithium ion storage device to a degradation test in which the Li-containing SEI coating of the coating-coated negative electrode active material layer is thickened; a negative electrode plate removal step of disassembling the lithium ion storage device and removing the negative electrode plate; a removal step of washing and removing the electrolyte solution adhering to the removed negative electrode plate; and a step of determining the amount of Li contained in the Li-containing SEI coating of the coated negative electrode active material layer. Linear distribution in the width direction or length direction or surface distribution and a Li amount distribution acquisition step of examining the distribution.

[0008] In this method for inspecting a lithium-ion storage device (hereinafter simply referred to as a device), the device is disassembled, the negative electrode plate is removed, the negative electrode plate is washed to remove any adhering electrolyte, and the distribution of the amount of Li contained in the Li-containing SEI coating formed on the coated negative electrode active material layer is investigated. From this distribution of Li, the amount of the SEI coating formed on the negative electrode active material particles in the coated negative electrode active material layer of the negative electrode plate of the device's electrode body can be determined. Thus, the presence or absence and degree of localized uneven distribution of the SEI coating can be used to predict the degree of degradation, such as whether the device will deteriorate quickly or slowly if used.

[0009] Examples of lithium ion storage devices include lithium ion secondary batteries and capacitors such as lithium ion capacitors. The electrode body housed in the device may be a laminated electrode body or a wound electrode body. Examples of wound electrode bodies include cylindrical wound electrode bodies and flat wound electrode bodies.

[0010] The electrolyte may be a non-aqueous electrolyte obtained by dissolving a supporting salt in an organic solvent. Examples of the organic solvent used for the electrolyte include cyclic carbonates such as propylene carbonate and ethylene carbonate (EC), and chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate, and ethyl methyl carbonate (EMC).

[0011] Examples of supporting salts to be dissolved in the electrolytic solution include lithium salts that serve as electrolytes, such as LiBF, LiAsF, LiPF, LiCFSO, LiN(SOCF), LiN(SOCF) and LiN(SOCF)(SOCF), etc. These salts may be used alone or in mixtures of two or more thereof, but are not limited to these.

[0012] In the Li amount distribution acquisition step, methods for examining the Li amount distribution include ICP-MS, ICP-OES, XPS, AES, and EDS.

[0013] The Li amount distribution data to be acquired may be any data on the distribution of the Li amount in a predetermined range to be investigated, and examples thereof include linear distribution data obtained in a linear range extending in a desired direction such as the width direction or length direction of the negative electrode active material layer, and planar distribution data in a desired circular or rectangular range.

[0014] (2) The method for inspecting a lithium ion storage device according to (1) above, wherein the electrolyte is a P-containing electrolyte containing a supporting salt containing phosphorus, the coated negative electrode active material layer of the negative electrode plate has a LiP-containing SEI coating that also contains phosphorus, the Li-containing SEI coating being formed on the negative electrode active material layer that does not contain phosphorus, and a method for inspecting the P amount contained in the LiP-containing SEI coating of the coated negative electrode active material layer, which is performed instead of the Li amount distribution acquisition step or together with the Li amount distribution acquisition step, Linear distribution or planar distribution in the width direction or the length direction The method for inspecting a lithium ion electricity storage device may preferably include a P amount distribution acquisition step for examining the distribution.

[0015] In this device inspection method, the device's electrolyte is a phosphorus-containing electrolyte, and the coated negative electrode active material layer does not contain phosphorus, but has a LiP-containing SEI coating that contains phosphorus in addition to lithium. In addition, the method includes a phosphorus amount distribution acquisition step performed instead of or together with the Li amount distribution acquisition step. Therefore, the distribution of the amount of the SEI coating formed on the negative electrode active material particles in the coated negative electrode active material layer in the negative electrode plate of the device's electrode body can be determined from the phosphorus amount distribution or the distribution of the phosphorus and Li amounts. Even in this way, the degree of degradation of the device when used can be predicted from the presence or absence and degree of localized uneven distribution of the SEI coating. Furthermore, by measuring the distribution of the Li amount and the distribution of the P amount in the same region, it is possible to more reliably detect the presence or absence and degree of local uneven distribution of the SEI film and predict the progress of degradation of the device.

[0016] An example of a phosphorus-containing supporting salt is LiPF6. Methods for examining the distribution of P content include ICP-MS, ICP-OES, XPS, AES, and EDS.

[0017] The P content distribution data to be acquired may be any data on the P content distribution in a predetermined range to be investigated, such as linear distribution data obtained in a range extending linearly in a desired direction, such as the width direction or length direction of the negative electrode active material layer, or planar distribution data in a desired circular or rectangular range. When obtaining the Li content distribution in addition to the P content distribution, it is preferable to obtain the P content and the Li content at the same position. This makes it easier to compare the distributions of the two elements.

[0018] (3) Another aspect is a method for producing a device group consisting of a plurality of lithium ion electricity storage devices, the device group including: an electrolyte; a positive electrode plate having a positive electrode active material layer; a negative electrode plate having a coated negative electrode active material layer in which a Li-containing SEI coating containing lithium is formed on negative electrode active material particles; an electrode body having a separator interposed between the positive electrode active material layer and the coated negative electrode active material layer and permeated with the electrolyte; and a case accommodating the electrode body and the electrolyte, the method comprising the steps of: selecting a sample device from an undetermined device group consisting of a plurality of the lithium ion electricity storage devices; a degradation step of subjecting the sample device to a degradation test in which the Li-containing SEI coating of the coated negative electrode active material layer of the sample device is thickened; a negative electrode plate removal step of disassembling the deteriorated sample device and removing the negative electrode plate; a removal step of washing and removing the electrolyte adhering to the removed negative electrode plate; Linear distribution in the width direction or length direction or surface distribution The method for manufacturing a device group includes a Li amount distribution acquisition process for examining the distribution, and a determination process for selecting sample devices from the device group and determining whether the devices are good or bad based on the obtained Li amount distribution.

[0019] In this device group manufacturing method, a sample device is selected from the device group, subjected to a degradation test, and then the sample device is disassembled to remove the negative electrode plate. The negative electrode plate is washed to remove any adhering electrolyte, and the distribution of Li contained in the Li-containing SEI coating formed on the coated negative electrode active material layer is investigated. From this Li distribution, the distribution of the amount of SEI coating formed on the negative electrode active material particles in the coated negative electrode active material layer of the negative electrode plate of the electrode body of the sample device can be determined. In addition, the presence or absence and degree of localized uneven distribution of the SEI coating on the sample device can be used to predict and select the degree of degradation progression of the untested device group from which the sample device was obtained. In this way, a good device group with slow degradation progression characteristics can be manufactured.

[0020] The selection method for the sample device from the device group in the selection process includes randomly selecting one or more sample devices from the multiple devices that make up the device group. Alternatively, the first, last, or intermediate device manufactured in a production lot may be selected. Alternatively, the sample device may be selected based on device characteristics, such as a battery capacity that has been previously inspected and is average in size among the device group.

[0021] (4) Further, in the method for producing the device group of (3), the electrolyte is a P-containing electrolyte containing a phosphorus-containing supporting salt, and the coated negative electrode active material layer of the negative electrode plate is formed by forming the Li-containing SEI film, which is a LiP-containing SEI film that also contains phosphorus, on a phosphorus-free negative electrode active material layer, and a method for measuring the amount of P contained in the LiP-containing SEI film of the coated negative electrode active material layer, which is performed instead of the Li amount distribution obtaining step or together with the Li amount distribution obtaining step. Linear distribution or planar distribution in the width direction or the length direction The method for manufacturing a device group may further include a P amount distribution acquisition step for examining the distribution, and the judgment step may use the P amount distribution instead of or in addition to the Li amount distribution to judge the quality of the unjudged device group from which the sample devices have been obtained.

[0022] In this device group manufacturing method, the electrolyte of each device is a phosphorus-containing electrolyte, and the coated negative electrode active material layer does not contain phosphorus, but has a LiP-containing SEI coating that contains phosphorus in addition to lithium. Additionally, a phosphorus amount distribution acquisition step is performed on the sample device instead of the Li amount distribution acquisition step or in addition to the Li amount distribution acquisition step. Therefore, the distribution of the amount of the SEI coating formed on the negative electrode active material particles in the coated negative electrode active material layer of the negative electrode plate of the device electrode body can be determined from the phosphorus amount distribution or the distribution of the phosphorus amount and the Li amount distribution. In this way, the presence or absence and degree of localized SEI coating unevenness can be used to predict and select the degree of degradation when using the untested device group from which the sample device was obtained, thereby enabling the production of a good device group with slow degradation characteristics.

[0023] (5) In the method for manufacturing a device group according to (3), the judgment step may be a method for manufacturing a device group in which the pass / fail judgment of the unjudged device group is performed using the minimum and maximum Li amounts in the obtained distribution of Li amounts.

[0024] In this method of manufacturing a group of devices, the minimum and maximum values ​​of the amount of Li are used in the judgment step, so that the pass / fail judgment of the group of unjudged devices can be easily performed.

[0025] In the method for manufacturing a device group according to (6) or (4), the judgment step may be a method for manufacturing a device group in which the pass / fail judgment of the undetermined device group is performed using the minimum and maximum P amounts in the obtained P amount distribution, or using the minimum and maximum P amounts and the minimum and maximum Li amounts in the obtained Li amount distribution.

[0026] In this method for manufacturing a device group, the pass / fail judgment of an unjudged device group can be performed simply by using the minimum and maximum P amounts in the judgment process, or more reliably by using the minimum and maximum P amounts, and the minimum and maximum Li amounts.

[0027] (7) Furthermore, in the method for manufacturing a device group described in any one of (3) to (6), the degradation process may be a process for reducing the capacity of the sample device until the capacity retention rate becomes smaller than a predetermined value.

[0028] In this method for manufacturing a group of devices, the capacity of the sample devices is reduced in the degradation step until the capacity retention rate becomes smaller than a predetermined value. This makes it possible to appropriately determine the quality of the sample devices, and ultimately the quality of the group of undetermined devices, using the Li amount distribution obtained in the Li amount distribution acquisition step or the P amount distribution obtained in the P amount distribution acquisition step.

[0029] The forced degradation test for reducing the capacity of the sample device may be a charge-discharge cycle test in which charging and discharging are repeated over a predetermined SOC range. In this sample device, the amount of the SEI coating formed on the negative electrode active material particles in the coated negative electrode active material layer can be increased quickly, allowing for early determination of the quality of the device group. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a partially cutaway perspective view of a battery according to an embodiment and first and second modified embodiments. [Figure 2] FIG. 1 is a perspective view of a flat wound electrode body according to an embodiment and modified embodiments 1 and 2. [Figure 3] 1 is an explanatory view showing the positive electrode plate, the negative electrode, and the separator in a flat wound electrode assembly developed according to the embodiment and the first and second modified embodiments. FIG. [Figure 4] 10 is an explanatory view showing a state in which a negative electrode SEI coating is formed on a negative electrode active material particle of a coated negative electrode active material layer according to the embodiment and modified examples 1 and 2. FIG. [Figure 5] 3 is a flowchart showing a manufacturing process of a battery pack according to an embodiment. [Figure 6]1 is a graph showing an example of the distribution of the amount of Li contained in a strip-shaped coated negative electrode active material layer obtained from degraded good batteries from a good lot and defective batteries from a defective lot. [Figure 7] 10 is a graph showing the relationship between the capacity maintenance rate of good batteries from a degraded good product lot and defective batteries from a defective product lot and the Li fluctuation rate obtained from the distribution of Li amounts. [Figure 8] 10 is a flowchart showing a manufacturing process of a battery pack according to a first modified embodiment. [Figure 9] 1 is a graph showing an example of the distribution of P amounts contained in strip-shaped coated negative electrode active material layers obtained from degraded good batteries from a good lot and defective batteries from a defective lot. [Figure 10] 10 is a graph showing the relationship between the capacity maintenance rate of good batteries from a degraded good product lot and defective batteries from a defective product lot and the P fluctuation rate obtained from the P amount distribution. [Figure 11] 10 is a flowchart showing a manufacturing process of a battery pack according to a second modified embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] (Embodiment) Hereinafter, a battery group GB (an example of a device group) including a plurality of batteries 1 (an example of a lithium ion power storage device) that are lithium ion secondary batteries according to an embodiment of the present invention, and the manufacture thereof will be described with reference to Figures 1 to 7. The plurality of batteries 1 belonging to this battery group GB are each a rectangular, sealed lithium ion secondary battery, and are installed in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars, as well as in various devices.

[0032] The battery 1 of this embodiment includes a rectangular parallelepiped case 7 and an electrode assembly 2 and electrolyte 6 housed inside the case 7. The rectangular parallelepiped box-shaped case 7 is made of metal (aluminum in this embodiment). It consists of a bottomed, square-tubular case body 7H and a lid 7L located at the upper BH1 in the height direction BH. A positive electrode terminal 8P and a negative electrode terminal 8N are fixed to the lid 7L via an insulating member 9. A liquid filling hole 7LH for pouring the electrolyte 6 is drilled in the lid 7L, and the hole is sealed with a liquid filling plug 7LP after pouring. The electrode assembly 2 is covered in a bag-shaped insulating film (not shown) inside the case 7. The electrolyte 6 housed in the case 7 is partially impregnated into the electrode assembly 2, with the remainder pooling at the bottom of the case 7.

[0033] The electrode assembly 2 (see FIGS. 2 and 3) is a so-called flat wound electrode assembly, in which a strip-shaped positive electrode plate 3 and a strip-shaped negative electrode plate 4 are wound with a pair of strip-shaped separators 5 interposed therebetween, pressed flat in the thickness direction CH, and housed in a case 7. The electrode assembly 2 is housed in the case 7 in a horizontal position with the winding axis AX coinciding with the width direction AH (the left-right direction in FIG. 1).

[0034] In the flat wound electrode body 2, a positive current collecting portion 2P, on which a current collecting portion 3S of a positive electrode plate 3 is wound, is provided on one side XH1 in the axial direction XH along the winding axis AX (in this embodiment, this corresponds to one side AH1 in the width direction AH of the battery 1; upper side in FIG. 2). Conversely, a negative current collecting portion 2N, on which a current collecting portion 4S of a negative electrode plate 4 is wound, is provided on the other side XH2 in the axial direction XH (in this embodiment, this corresponds to the other side AH2 in the width direction AH of the battery 1; lower side in FIG. 2). The portion between the positive current collecting portion 2P and the negative current collecting portion 2N is a main body 2H, on which the positive electrode plate 3 and the negative electrode plate 4 are wound with a separator 5 interposed therebetween.

[0035] The positive electrode terminal 8P is made of an aluminum plate bent into a predetermined shape. An inner connection portion 8PI forming one end of the positive electrode terminal 8P is connected to a positive electrode current collector 2P arranged on one side AH1 in the width direction AH of the electrode assembly 2. Meanwhile, the other end of the positive electrode terminal 8P is drawn out of the case 7 (specifically, onto the lid 7L) to form an external terminal portion 8PO. The negative electrode terminal 8N is made of a copper plate bent into a predetermined shape. An inner connection portion 8NI forming one end of this negative electrode terminal 8N is connected to a negative electrode current collector 2N arranged on the other side AH2 in the width direction AH of the electrode assembly 2. Meanwhile, the other end of the negative electrode terminal 8N is drawn out of the case 7 (specifically, onto the lid 7L) to form an external terminal portion 8NO.

[0036] The electrolyte 6 is a non-aqueous electrolyte containing an organic solvent 6V and a supporting salt 6S. In this embodiment, the organic solvent 6V is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a weight ratio of 3:4:3. LiPF6 is used as the supporting salt 6S containing P. The concentration of LiPF6 in the electrolyte 6 is 1.1 mol / L.

[0037] As shown in FIG. 3 , the strip-shaped positive electrode plate 3 of the electrode assembly 2 includes a positive electrode foil 3F made of aluminum foil and a positive electrode active material layer 3A laminated on both surfaces of the positive electrode foil 3F. The positive electrode active material layer 3A is composed of positive electrode active material particles, conductive particles, and a binder (not shown). In this embodiment, the positive electrode active material particles are lithium transition metal composite oxide particles, specifically, for example, lithium nickel cobalt manganese composite oxide particles. The conductive particles are, for example, acetylene black (AB). The binder is, for example, polyvinylidene fluoride (PVDF). At the end of one side WH1 (upper side in FIG. 3 ) in the width direction WH of the strip-shaped positive electrode plate 3, the positive electrode active material layer 3A is not present on the positive electrode foil 3F, forming a current collecting portion 3S where the positive electrode foil 3F is exposed. Meanwhile, the remaining portion of the positive electrode plate 3 is a positive electrode portion 3P in which the positive electrode active material layer 3A is laminated on both surfaces of the positive electrode foil 3F. As can be seen from FIGS. 2 and 3, the width direction WH (the vertical direction in FIG. 3) of the positive electrode plate 3 etc. coincides with the axial direction XH, and one side WH1 coincides with one side XH1.

[0038] On the other hand, the strip-shaped negative electrode plate 4 of the electrode body 2 includes a negative electrode foil 4F made of copper foil and a coated negative electrode active material layer 4A laminated on both surfaces of the negative electrode foil 4F. The coated negative electrode active material layer 4A includes a negative electrode active material layer 4AB made of negative electrode active material particles 4AP and a binder (not shown) that does not contain P, and a negative electrode SEI coating 4AC formed in a coating state around the negative electrode active material particles 4AP during an initial charging process described below. In this embodiment, graphite particles are used as the negative electrode active material particles 4AP. Furthermore, carboxymethyl cellulose (CMC), for example, is used as the binder. At the end of the other side WH2 (lower in FIG. 3 ) in the width direction WH of the strip-shaped negative electrode plate 4, the coated negative electrode active material layer 4A is not present on the negative electrode foil 4F, forming a current collecting portion 4S where the negative electrode foil 4F is exposed. On the other hand, the remaining portion of the negative electrode plate 4 is a negative electrode portion 4N in which a negative electrode active material layer 4A with a coating is laminated on both surfaces of a negative electrode foil 4F.

[0039] In addition, a pair of strip-shaped separators 5 in the electrode assembly 2 are made of porous resin. As shown in FIG. 3, the separator 5 is wound and stacked between the negative electrode plate 4 and the positive electrode plate 3. The negative electrode plate 4 and the negative electrode portion 4N are slightly wider in the width direction WH than the positive electrode plate 3 and the positive electrode portion 3P. Furthermore, the negative electrode portion 4N is arranged so as to cover the entire positive electrode portion 3P in the width direction WH, i.e., so that the coated negative electrode active material layer 4A faces the positive electrode active material layer 3A at any portion of the positive electrode active material layer 3A. The separator 5 is also slightly wider in the width direction WH than the negative electrode portion 4N and the positive electrode portion 3P. Moreover, the separator 5 is arranged so as to cover the entire negative electrode portion 4N and the positive electrode portion 3P in the width direction WH, that is, so that the separator 5 covering the positive electrode active material layer 3A and the coated negative electrode active material layer 4A is present at every position of the positive electrode active material layer 3A and the coated negative electrode active material layer 4A.

[0040] 4, a negative electrode SEI coating 4AC containing Li and P is formed around the negative electrode active material particles 4AP constituting the coated negative electrode active material layer 4A formed on the negative electrode foil 4F of the negative electrode plate 4. The negative electrode SEI coating 4AC is derived from the organic solvent 6V and the supporting salt 6S containing P (phosphorus) contained in the electrolyte 6. The formation of this negative electrode SEI coating 4AC enables stable charging and discharging of the battery 1 with low resistance, compared to when the negative electrode SEI coating 4AC is not formed or is insufficiently formed.

[0041] In manufacturing the battery 1, the electrode assembly 2 is connected to the positive electrode terminal 8P and the negative electrode terminal 8N and housed in the case 7. When the electrolyte 6 is poured into the case 7, the electrolyte 6 permeates from the outside XHO to the inside XHI in the axial direction XH of the electrode assembly 2, i.e., from one side XH1 and the other side XH2, toward the inside of the electrode assembly 2. Specifically, the electrolyte 6 permeates along the positive electrode plate 3, the negative electrode plate 4, and the separator 5 from one side WH1 and the other side WH2 in the width direction WH (upper and lower in FIG. 3 ) that coincide with the axial direction XH, respectively, toward the center line ML of the width direction WH of the negative electrode active material layer 4AB, i.e., toward the inside WHI in the width direction WH.

[0042] After a predetermined waiting time TT has elapsed since the start of the liquid injection, a power source (not shown) is connected to the positive electrode terminal 8P and the negative electrode terminal 8N, and a voltage is applied to the electrode body 2 of the battery 1 via the positive electrode terminal 8P and the negative electrode terminal 8N to perform initial charging. That is, a voltage is applied between the positive electrode plate 3 and the negative electrode plate 4 of the electrode body 2 according to a predetermined initial charging pattern, and a negative electrode SEI coating 4AC of the electrolyte 6 is formed on the negative electrode active material particles 4AP of the negative electrode active material layer 4AB of the negative electrode plate 4, thereby forming a coated negative electrode active material layer 4A (see FIG. 4). In this embodiment, initial charging was performed according to an initial charging pattern of 0.5 C-CCCV charging (SOC 85%). Thereafter, the liquid injection hole 7LH is sealed with the liquid injection plug 7LP.

[0043] Next, the sealed batteries 1 are subjected to high-temperature aging by being left in an environment of 60°C for 25 hours. Furthermore, various tests are performed on the batteries 1 to complete the batteries 1. By this unassessed battery group manufacturing process S1, an unassessed battery group GBB is manufactured, which is made up of a large number of batteries 1 and is managed by a single manufacturing lot number, etc., and whose deterioration prediction, described below, has not yet been judged (see FIG. 5).

[0044] However, depending on the battery 1, the negative electrode SEI coating 4AC formed on the negative electrode active material layer 4AB by the electrolyte solution 6 during initial charging may not be formed uniformly over the entire negative electrode active material layer 4A with the coating, and the amount and composition of the formed negative electrode SEI coating 4AC may vary (uneven) from place to place.

[0045] Thus, even in a battery 1 in which unevenness occurs in the negative electrode SEI coating 4AC formed on the coating-coated negative electrode active material layer 4A, various characteristics such as battery capacity and battery resistance are good at the initial stage of use. However, it has been found that a battery 1 in which unevenness occurs in the negative electrode SEI coating 4AC deteriorates significantly as it is repeatedly charged and discharged with subsequent use, compared to the deterioration state of a battery 1 in which unevenness occurs in the negative electrode SEI coating 4AC. It was thought that in a battery 1 in which unevenness occurs in the negative electrode SEI coating 4AC and localized uneven performance exists in the electrode body 2, deterioration progresses locally as the battery 1 is used, and therefore deterioration is likely to progress even when viewed as a whole.

[0046] (Li distribution survey) Therefore, we prepared a defective battery 1N, which had undergone similar use but exhibited significant deterioration in its characteristics, and a good battery 1G, which exhibited relatively slow deterioration and maintained good characteristics. Each battery 1G and 1N was discharged to 0% SOC and disassembled in a glove box under an inert atmosphere to remove the electrode assembly 2. The electrode assembly 2 was then unwound (see Figure 3) to remove the strip-shaped negative electrode plate 4. A negative electrode sample (not shown) including a region for measuring the Li content distribution was obtained from this negative electrode plate 4. For example, the flattened portion of the negative electrode plate 4 was cut in the width direction WH (the vertical direction in Figure 3) to obtain a tape-shaped negative electrode sample extending in the width direction WH.

[0047] The negative electrode sample was then washed with EMC to remove the electrolyte 6. This removed Li, LiPF6, and other components contained in the electrolyte 6. Next, ICP-MS was used to obtain the distribution of the amount of Li contained in the negative electrode SEI coating 4AC formed on the coated negative electrode active material layer 4A in a desired measurement region of the negative electrode sample. Specifically, the ICP-MS was used to measure the amount of Li at each width direction position WP in a linear measurement region extending in the width direction WH.

[0048] The results of measuring the distribution of the Li amount AL for the good battery 1G and the defective battery 1N are shown in Figure 6. The horizontal axis of the graph in Figure 6 represents the widthwise position WP, which is shown in mm as measured from the edge 4AE1 on one side WH1 in the widthwise direction WH of the negative electrode plate 4 shown in Figure 3 toward the other side WH2 in the widthwise direction WH. On the other hand, the vertical axis of the graph in Figure 6 represents a relative value indicating the relative magnitude of the Li amount AL.

[0049] 6, the distribution of the Li content AL of the good battery 1G, indicated by the solid line, was almost constant regardless of the widthwise position WP. That is, it can be seen that the Li content AL in the coated negative electrode active material layer 4A had very little variation (unevenness) in the widthwise direction WH. From this result, it can be seen that the amount (thickness) of the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A in the good battery 1G was also almost constant regardless of the widthwise position WP, with only slight variation (unevenness).

[0050] On the other hand, the distribution of the Li content AL of the defective battery 1N, shown by the dashed line in Figure 6, contained localized areas, specifically, areas near the widthwise position WP of 28 to 37 mm and 42 to 49 mm, where the Li content AL was significantly larger than in other areas. That is, it can be seen that in the defective battery 1N, the Li content AL contained in the negative electrode SEI coating 4AC exhibited large variations (unevenness) at the widthwise position WP. From this, it can be seen that in the defective battery 1N, the amount (thickness) of the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A also existed locally in areas where it was significantly larger, resulting in large variations (unevenness) at the widthwise position WP. Furthermore, these areas with an abnormally large amount of the negative electrode SEI coating 4AC caused localized abnormal degradation of the battery characteristics, specifically, localized decreases in battery capacity and localized increases in battery resistance. This is thought to have resulted in significant deterioration of the overall battery characteristics of the defective battery 1N compared to those of the non-defective battery 1G. It is presumed that the above-mentioned local abnormal increase in the amount (thickness) of the negative electrode SEI coating 4AC gradually accumulated with use of the battery.

[0051] (Li fluctuation ratio investigation) Therefore, a plurality of unused good batteries 1G from the same lot (good lot) as the good battery 1G used in the investigation shown in Fig. 6, and a plurality of unused defective batteries 1N from the same lot (defective lot) as the defective battery 1N used in the investigation shown in Fig. 6, are prepared. These good batteries 1G and the defective batteries 1N are each subjected to a predetermined charge-discharge cycle test, specifically, a forced deterioration test using a charge-discharge cycle test in which 1C CCCV charging and 1C CCCV discharging are repeated in the range of SOC 20 to 80%, causing the negative electrode SEI coating 4AC to thicken over time and causing deterioration in each of the batteries 1G and 1N.

[0052] In this embodiment, a forced degradation test was conducted on a plurality of good-quality batteries 1G and defective batteries 1N, with seven levels of capacity retention, including a case where the forced degradation test was not conducted (test time 0 hours). That is, the forced degradation test was conducted until the time when the good-quality batteries 1G or defective batteries 1N were estimated to reach a predetermined capacity retention, and the battery capacities of the removed good-quality batteries 1G and defective batteries 1N were measured. The capacity retention rates CC of the batteries 1G and 1N were calculated from the pre-test battery capacities obtained before the forced degradation test. Note that the number of cycles and test time of the charge-discharge cycle tests conducted on good-quality batteries 1G and defective batteries 1N that had approximately the same capacity retention rates CC were different from each other.

[0053] Then, similar to the Li content AL distribution investigation described above, the good battery 1G and the defective battery 1N were disassembled, and the negative electrode sample of the negative electrode plate 4 was used to obtain the Li content AL distribution similar to that shown in Figure 6. Next, as shown in Figure 6, the minimum Li content LI and maximum Li content LX were obtained from the Li content AL distribution, and the Li fluctuation ratio RL was calculated using RL = LX / LI. Specifically, the minimum Li content GLI and maximum Li content GLX were obtained from the Li content AL distribution of the good battery 1G. The Li fluctuation ratio RL of the good battery 1G was calculated using RL = GLX / GLI. Similarly, the minimum Li content NLI and maximum Li content NLX were obtained from the Li content AL distribution of the defective battery 1N, and the Li fluctuation ratio RL of the defective battery 1N was calculated using RL = NLX / NLI.

[0054] Figure 7 shows the changes in the capacity retention rate CC and the Li fluctuation ratio RL obtained from multiple good batteries 1G and multiple bad batteries 1N. Figure 7 shows that, for the good batteries 1G indicated by the solid line, the Li fluctuation ratio RL is maintained at approximately the same value, even though the capacity retention rate CC gradually decreases as the forced degradation test described above is performed over a long period of time. That is, for the good batteries 1G, the amount (thickness) of the negative electrode SEI coating 4AC is maintained in an approximately uniform state in the width direction WH, and no unevenness occurs, even as the batteries deteriorate.

[0055] In contrast, the defective battery 1N had a Li fluctuation ratio RL roughly equivalent to that of the good battery 1G at the beginning of the forced degradation test, i.e., until the capacity retention ratio CC reached approximately 97%. However, unlike the good battery 1G, as the forced degradation test continued for a longer period and the capacity retention ratio CC decreased beyond 97%, the Li fluctuation ratio RL increased as the capacity retention ratio CC decreased. By performing the forced degradation test, the negative electrode SEI film 4AC was abnormally formed in a specific region of the coated negative electrode active material layer 4A, and the abnormally formed region expanded to the surrounding area. Furthermore, in the abnormally formed region, the abnormally formed negative electrode SEI film 4AC made it difficult for the battery reaction to occur, resulting in a local decrease in battery capacity and an increase in battery resistance. This is thought to have resulted in a decrease in battery capacity and other problems throughout the electrode body 2 of the defective battery 1N.

[0056] According to these results, for a certain battery 1, before the aforementioned forced deterioration test is conducted, or after a short period of forced deterioration test is conducted to cause slight deterioration, and at the stage when the capacity retention rate CC is maintained at approximately 97% or more, even if this battery 1 is disassembled and the aforementioned Li amount distribution investigation is conducted to obtain the distribution of Li amount AL (see Figure 6), it is not possible to properly determine whether this battery 1 is a good battery 1G or a defective battery 1N.

[0057] However, if the Li amount distribution investigation is performed after the forced degradation test described above is performed until the capacity retention rate CC reaches 95% or less, it is possible to determine whether the battery 1 is a good-quality battery 1G or a bad-quality battery 1N. Specifically, for example, as shown by the dashed-dotted line in Fig. 7, a threshold value RLT (RLT = 2.0 in Fig. 7) is set for the Li fluctuation ratio RL, and if the obtained Li fluctuation ratio RL is smaller than the threshold value RLT, the battery is determined to be a good-quality battery 1G, and if it is larger than the threshold value RLT, the battery is determined to be a bad-quality battery 1N. This also makes it possible to determine whether the undetermined battery group GBB to which the battery 1 belongs is a good-quality battery group GBG consisting of good-quality batteries 1G or a bad-quality battery group GBN consisting of bad batteries 1N (see Fig. 5).

[0058] (Battery pack manufacturing) Therefore, in this embodiment, a battery group GB that comprises a single production lot and includes a large number of batteries 1 is manufactured as follows: First, in an unassessed battery group manufacturing step S1, an unassessed battery group GBB that comprises a single production lot and includes a large number of batteries 1 (see FIG. 1, for example) is manufactured using a known method. Note that each battery 1 is assumed to have already undergone high-temperature aging and initial charging.

[0059] Next, in a selection step S2, one or a small number of sample batteries 1S are selected from the many batteries 1 belonging to the undetermined battery group GBB. In the subsequent degradation step S3, the selected sample battery 1S is subjected to the aforementioned forced degradation test. Specifically, the aforementioned forced degradation test is performed to reduce the capacity of the sample battery 1S until the capacity retention rate CC of the sample battery 1S falls to a predetermined value of 95% or less, specifically, to approximately 95 to 93%. By performing this forced degradation test (charge-discharge cycle test), the amount of negative electrode SEI coating 4AC formed on the negative electrode active material particles 4AP of the coated negative electrode active material layer 4A in the sample battery 1S can be increased quickly, allowing for early determination of the quality of the undetermined battery group GBB.

[0060] After the forced degradation test is completed, in the negative electrode plate removal step S4, the sample battery 1S is discharged to an SOC of 0% and disassembled in a glove box under an inert atmosphere to remove the electrode assembly 2. The electrode assembly 2 is then unwound to remove the strip-shaped negative electrode plate 4. A negative electrode sample (not shown) including a region for measuring the Li content distribution is obtained from this negative electrode plate 4. For example, the flattened portion of the negative electrode plate 4 is cut in the width direction WH (the vertical direction in FIG. 3) to obtain a tape-shaped negative electrode sample extending in the width direction WH.

[0061] In the removal step S5, the removed negative electrode sample of the negative electrode plate 4 is washed with EMC to remove the adhering electrolyte 6. As a result, Li, LiPF6, and the like contained in the electrolyte 6 are removed from the negative electrode sample of the negative electrode plate 4.

[0062] In the Li amount distribution acquisition step S6, for the negative electrode sample, as described above, using IPC-MS, for a desired measurement region, the distribution of the Li amount AL contained in the negative electrode SEI film 4AC formed on the coated negative electrode active material layer 4A is obtained (see FIG. 6).

[0063] Thereafter, in the determination step S7, based on the obtained distribution of the Li amount AL, the quality of the undetermined battery group GBB from which the sample battery 1S was obtained is determined. Specifically, for example, as described above, the minimum Li amount LI and the maximum Li amount LX are obtained from the distribution of the Li amount AL, and the Li variation ratio RL is calculated. The obtained Li variation ratio RL is compared with a predetermined threshold value RLT. When the Li variation ratio RL is greater than the threshold value RLT (RL>RLT), it is determined that the sample battery 1S is a defective battery 1N. At the same time, the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a defective battery group GBN (NG in the determination step S7). Thereafter, processing such as disposal is performed.

[0064] Conversely, for example, when the Li variation ratio RL is less than the threshold value RLT (RL<RLT), it is determined that the sample battery 1S is a non-defective battery 1G (GOOD in the determination step S7). At the same time, the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a non-defective battery group GBG. Thus, a good battery group GB (non-defective battery group GBG) having characteristics with slow progress of deterioration can be manufactured.

[0065] As described above, in this embodiment, in the determination step S7, since the minimum Li amount LI and the maximum Li amount LX are used, the quality of the undetermined battery group GBB can be easily determined.

[0066] (Variant 1) In the above-described embodiment, in manufacturing the battery group GB, the distribution of the Li amount AL was obtained from the negative electrode sample of the negative electrode plate 4 of the sample battery 1S, and the quality of the sample battery 1S and the undetermined battery group GBB to which this sample battery 1S belongs was determined using this Li amount distribution (see FIG. 5). However, the electrolyte 6 of the battery 1 described above is a phosphorus-containing supporting electrolyte 6S, specifically a P-containing electrolyte containing LiPF. Therefore, during initial charging, the negative electrode SEI coating 4AC formed on the negative electrode active material particles 4AP contains P in addition to Li.

[0067] (Distribution survey of P content) Therefore, in this modified embodiment 1, instead of obtaining the Li amount distribution (see FIG. 6), the distribution of the P amount AP in the negative electrode sample obtained from the negative electrode plate 4 is obtained. That is, as in the embodiment, an ICP-MS is used to obtain the distribution of the P amount AP contained in the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A for a desired measurement region in the negative electrode sample obtained for the aforementioned good battery 1G and defective battery 1N (see FIG. 9). The horizontal axis of the graph in FIG. 9 also represents the widthwise position WP, which is indicated by the dimension (mm) measured from the edge 4AE1 on one side WH1 in the widthwise direction WH to the other side WH2 in the widthwise direction WH, in the negative electrode plate 4 shown in FIG. 3. Meanwhile, the vertical axis of the graph in FIG. 9 represents a relative value indicating the relative magnitude of the P amount AP.

[0068] 9 and 6, in the good battery 1G shown by the solid line in FIG. 9, the distribution of the P amount AP is almost constant regardless of the width direction position WP, just like the distribution of the Li amount AL. That is, it can be seen that the variation (unevenness) in the width direction WH of the P amount AP contained in the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A of the good battery 1G is also very slight, just like the variation in the Li amount AL. From these results, it can also be seen that the amount (thickness) of the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A of the good battery 1G is also almost constant regardless of the width direction position WP, and the variation (unevenness) is very slight.

[0069] On the other hand, the distribution of the P amount AP of the defective battery 1N shown by the dashed line in Figure 9 is similar to the distribution of the Li amount AL of the defective battery 1N shown by the dashed line in Figure 6. Specifically, there were localized areas, specifically near the widthwise positions WP of 28 to 37 mm and 42 to 49 mm, where the P amount AP was significantly larger than other areas. That is, it can be seen that in the defective battery 1N, the P amount AP contained in the negative electrode SEI coating 4AC also exhibited significant variations (unevenness) with respect to the widthwise position WP. The distribution of the P amount AP also reveals that in the defective battery 1N, the amount (thickness) of the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A also exhibited significant variations (unevenness) with respect to the widthwise position WP. This likely resulted in significant deterioration of the overall battery characteristics of the defective battery 1N compared to those of the non-defective battery 1G.

[0070] (Survey of P fluctuation ratio) In this first modified example, the P fluctuation ratio RP was investigated (see FIG. 10 ) in the same manner as in the embodiment, using negative electrode samples of the negative electrode plates 4 of multiple good batteries 1G and multiple bad batteries 1N used in the investigation of the Li fluctuation ratio RL (see FIG. 7 ). As shown in FIG. 9 , the minimum P amount PI and maximum P amount PX were obtained from the P amount AP values, and the P fluctuation ratio RP was calculated by RP = PX / PI. Specifically, the minimum P amount GPI and maximum P amount GPX were obtained from the distribution of the P amount AP of the good battery 1G. The P fluctuation ratio RP of the good battery 1G was calculated by RP = GPX / GPI. Similarly, the minimum P amount NPI and maximum P amount NPX were obtained from the distribution of the P amount AP of the bad battery 1N, and the P fluctuation ratio RP of the bad battery 1N was calculated by RL = NLX / NLI.

[0071] Figure 10 shows the changes in the capacity retention rate CC and the P fluctuation ratio RP of the good-quality battery 1G and the bad-quality battery 1N over time. As in the embodiment (see Figure 7), in Figure 10, the P fluctuation ratio RP of the good-quality battery 1G remains approximately the same even when the capacity retention rate CC decreases due to the forced degradation test described above. That is, the changes in the P fluctuation ratio RP in Figure 10 also show that the amount (thickness) of the negative electrode SEI coating 4AC remains approximately uniform in the width direction WH of the good-quality battery 1G, even when it deteriorates, and no unevenness occurs.

[0072] In contrast, as in the embodiment (see FIG. 7), the defective battery 1N has a P variation ratio RP that is generally similar to that of the non-defective battery 1G until the capacity retention rate CC reaches approximately 97%. However, once the capacity retention rate CC decreases beyond 97%, the P variation ratio RP increases as the capacity retention rate CC decreases. By performing the forced degradation test, a negative electrode SEI coating 4AC is abnormally formed in a specific portion of the coated negative electrode active material layer 4A. In this abnormally formed portion, the abnormally formed negative electrode SEI coating 4AC makes it difficult for a battery reaction to occur, and it is believed that the electrode body 2 of the defective battery 1N as a whole experienced a significant decrease in battery capacity, etc.

[0073] From these results, as in the embodiment, if the forced degradation test described above is performed until the capacity retention rate CC becomes 95% or less, and then a distribution survey of the P amount AP is performed, it is possible to determine whether the battery 1 is a good battery 1G or a bad battery 1N. Specifically, for example, as shown by the dashed-dotted line in Fig. 10, a threshold value RPT (RPT = 2.0 in Fig. 10) is set for the P fluctuation ratio RP, and if the obtained P fluctuation ratio RP is smaller than the threshold value RPT, the battery 1 is determined to be a good battery 1G. Furthermore, it is also possible to determine whether the undetermined battery group GBB to which the battery 1 belongs is a good battery group GBG consisting of good batteries 1G, or a bad battery group GBN consisting of bad batteries 1N (see Fig. 8).

[0074] (Battery pack manufacturing) Therefore, in this modified embodiment 1, a battery group GB is manufactured that comprises a single manufacturing lot and includes a large number of batteries 1. Specifically, in the manufacturing method of the battery group GB shown in Fig. 8, the undetermined battery group manufacturing step S1 to the removal step S5 are the same as the manufacturing method of the battery group GB shown in the embodiment (see Fig. 5).

[0075] However, in the P amount distribution acquisition step S16 of the present modified embodiment 1, which replaces the Li amount distribution acquisition step S6 of the embodiment, the distribution of the P amount AP contained in the negative electrode SEI coating 4AC formed on the coating-coated negative electrode active material layer 4A is obtained for a desired measurement region of the negative electrode sample using ICP-MS (see FIG. 9).

[0076] Thereafter, different from the determination step S7 of the embodiment, in the determination step S17, based on the distribution of the obtained P amount AP, the quality of the undetermined battery group GBB from which the sample battery 1S was obtained is determined. Specifically, for example, as described above, from the distribution of the P amount AP, the minimum P amount PI and the maximum P amount PX are obtained, and the P variation ratio RP is calculated. Then, the obtained P variation ratio RP is compared with a predetermined threshold value RPT. When the P variation ratio RP is greater than the threshold value RPT (RP > RPT), it is determined that the sample battery 1S is a defective battery 1N, and the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a defective battery group GBN (NG in the determination step S17).

[0077] [[ID=~]]<00002~0>Conversely, for example, when the P variation ratio RP is smaller than the threshold value RPT (RP < RPT), it is determined that the sample battery 1S is a non-defective battery 1G (GOOD in the determination step S17), and the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a non-defective battery group GBG. Thus, even in this modified form 1, a good battery group GB (non-defective battery group GBG) having a characteristic of slow progress of deterioration can be manufactured.

[0078] Note that in this way, in this modified form 1, in the determination step S17, since the minimum P amount PI and the maximum P amount PX are used, the quality of the undetermined battery group GBB can be easily determined.

[0079] (Modified Form 2) In the above-described embodiment and modified form 1, in manufacturing the battery group GB, the Li amount distribution or the P amount distribution is obtained from the negative electrode sample of the negative electrode plate 4 of the sample battery 1S, and only one of the obtained Li amount distribution or P amount distribution is used to determine the quality of the sample battery 1S and the undetermined battery group GBB to which this sample battery 1S belongs (see FIGS. 5 and 8).

[0080] In contrast, in this modified form 2, both the Li amount distribution (see FIG. 6) and the P amount distribution (see FIG. 9) are obtained from the negative electrode sample of the negative electrode plate 4 of the sample battery 1S, and both the obtained Li amount distribution and P amount distribution are used to determine the quality of the sample battery 1S and the undetermined battery group GBB to which this sample battery 1S belongs.

[0081] (Battery pack manufacturing) That is, in this modified embodiment 2, a battery group GB is manufactured that constitutes a single manufacturing lot and includes a large number of batteries 1. Specifically, in the manufacturing method of the battery group GB shown in Fig. 11, the undetermined battery group manufacturing step S1 to the removal step S5 are the same as the manufacturing method of the battery group GB in the embodiment and modified embodiment 1 shown in Figs.

[0082] However, in the LiP amount distribution acquisition step S26 of the present modified embodiment 2, the distribution of the Li amount AL and the distribution of the P amount AP contained in the negative electrode SEI coating 4AC formed in the coated negative electrode active material layer 4A are obtained for a desired measurement region of the negative electrode sample using ICP-MS (see FIGS. 6 and 9). That is, the LiP amount distribution acquisition step S26 is a step that combines the Li amount distribution acquisition step S6 in the embodiment and the P amount distribution acquisition step S16 in the modified embodiment.

[0083] Then, in the determination step S27 of this second modified embodiment, the quality of the undetermined battery group GBB from which the sample battery 1S was obtained is determined based on the obtained distributions of Li amount AL and P amount AP. Specifically, as described above, the minimum Li amount LI and maximum Li amount LX are obtained from the distribution of Li amount AL to calculate the Li fluctuation ratio RL. The minimum P amount PI and maximum P amount PX are obtained from the distribution of P amount to calculate the P fluctuation ratio RP. The obtained Li fluctuation ratio RL is compared with a predetermined threshold value RLT, and the P fluctuation ratio RP is compared with a predetermined threshold value RPT. If at least one of the Li fluctuation ratio RL is greater than the threshold value RLT (RL>RLT) and the P fluctuation ratio RP is greater than the threshold value RPT (RP>RPT), the sample battery 1S is determined to be a defective battery 1N. At the same time, the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a defective battery group GBN (NG in the determination step S27).

[0084] Conversely, for example, when the Li variation ratio RL is smaller than the threshold value RLT (RL < RLT) and the P variation ratio RP is smaller than the threshold value RPT (RP < RPT), the sample battery 1S is determined to be a good battery 1G (GOOD in the determination step S27). At the same time, the undetermined battery group GBB to which the sample battery 1S belongs is determined to be a good battery group GBG. Thus, even in this second modified embodiment, a good battery group GB (good battery group GBG) having the characteristic of slow progress of deterioration can be manufactured.

[0085] Note that as described above, in this second modified embodiment, in the determination step S27, in addition to the minimum Li value LI and the maximum Li value LX, the minimum P value PI and the maximum P value PX are also used for determination, so that the quality determination of the undetermined battery group GBB can be performed more reliably.

[0086] As described above, the present invention has been described in accordance with the embodiments and the first and second modified embodiments. However, the present invention is not limited to the embodiments and the like, and it is needless to say that it can be appropriately modified and applied without departing from the gist thereof. For example, in the embodiments and the first and second modified embodiments, in the defective battery 1N in which deterioration has occurred, an example is shown in which in the Li amount distribution and the P amount distribution, a portion where the Li amount AL and the P amount AP are larger than other portions locally exists (see FIGS. 6 and 9). However, conversely, there may be a defective battery 1N in which a portion where the Li amount AL and the P amount AP are smaller than other portions locally exists. In this case as well, the quality determination of the undetermined battery group GBB can be performed by obtaining the minimum Li value LI and the maximum Li value LX from the Li amount distribution and calculating the Li variation ratio RL, or by obtaining the minimum P value PI and the maximum P value PX from the P amount distribution and calculating the P variation ratio RP.

Explanation of Reference Numerals

[0087] 1 Battery (Lithium Ion Storage Device) 1G Good Battery 1N Defective Battery 1S Sample Battery (Sample Device) GB Battery Group (Device Group) GBB Undetermined Battery Group (Undetermined Device Group) GBG Good Battery Group GBN Bad Battery Group 2 Electrode Body 3 Positive Electrode Plate 3A Positive Electrode Active Material Layer 4 Negative Electrode Plate 4A Negative Electrode Active Material Layer (Coated Negative Electrode Active Material Layer) 4AB Negative Electrode Active Material Layer ML Center Line WP Width Direction Position (of Negative Electrode Active Material Layer) 4AE1 Edge (on One Side in Width Direction) 4AP Negative Electrode Active Material Particles 4AC Negative Electrode SEI Film (Li-Containing SEI Film, LiP-Containing SEI Film) AL Li Content AP P Content LX, GLX, NLX Maximum Value of Li Content LI, GLI, NLI Minimum Value of Li Content PX, GPX, NPX Maximum Value of P Content LI, GPI, NPI Minimum Value of P Content RL Li Variation Ratio RLT Threshold Value RP P Variation Ratio RPT Threshold Value 6 Electrolyte 6V Organic Solvent 6S Supporting Salt (Supporting Salt Containing P) 7 Case XH Axial Direction XHI Inside XHO Outside WH Width Direction S1 Undetermined Battery Group Manufacturing Process S2 Selection Process S3 Degradation Process S4 Negative Electrode Plate Extraction Process S5 Removal Process S6 Li Content Distribution Acquisition Process S16 P Content Distribution Acquisition Process S26 LiP Content Distribution Acquisition Process (Li Content Distribution Acquisition Process, P Content Distribution Acquisition Process) S7 Li Content Distribution Judgment Process S17 P Content Distribution Judgment Process S27 LiP amount distribution determination project

Claims

1. An electrolyte containing lithium; an electrode body having a positive electrode plate having a positive electrode active material layer, a negative electrode plate having a coated negative electrode active material layer on which a Li-containing SEI coating containing lithium is formed, and a separator interposed between the positive electrode active material layer and the coated negative electrode active material layer, and permeated with the electrolyte; a case that accommodates the electrode body and the electrolyte; A method for inspecting a lithium ion storage device, comprising: a degradation step of subjecting the lithium ion storage device to a degradation test in which the Li-containing SEI coating of the coating-coated negative electrode active material layer is thickened; a negative electrode plate removal step of dismantling the deteriorated lithium ion storage device and removing the negative electrode plate; a removing step of washing and removing the electrolyte adhering to the removed negative electrode plate; and a Li amount distribution acquisition step of examining a linear distribution or a planar distribution of the Li amount contained in the Li-containing SEI coating of the coating-coated negative electrode active material layer in the width direction or the length direction. A method for inspecting a lithium-ion storage device.

2. 2. A method for inspecting a lithium ion storage device according to claim 1, comprising: the electrolyte is a P-containing electrolyte containing a supporting salt containing phosphorus, The coated negative electrode active material layer of the negative electrode plate is the Li-containing SEI coating, which is a LiP-containing SEI coating that also contains phosphorus, is formed on a negative electrode active material layer that does not contain phosphorus, a P amount distribution acquisition step, which is performed instead of the Li amount distribution acquisition step or together with the Li amount distribution acquisition step, of examining a linear distribution or a planar distribution of the P amount contained in the LiP-containing SEI coating of the coated negative electrode active material layer in the width direction or the length direction; A method for inspecting a lithium-ion storage device.

3. An electrolyte solution containing lithium; an electrode body having a positive electrode plate having a positive electrode active material layer, a negative electrode plate having a coated negative electrode active material layer on which a Li-containing SEI coating containing lithium is formed, and a separator interposed between the positive electrode active material layer and the coated negative electrode active material layer, and permeated with the electrolyte; a case that accommodates the electrode body and the electrolyte; A method for manufacturing a group of devices consisting of a plurality of lithium ion storage devices, comprising: a selection step of selecting a sample device from an undetermined device group consisting of a plurality of the lithium ion electricity storage devices; a degradation step of subjecting the sample device to a degradation test in which the Li-containing SEI coating of the coating-coated negative electrode active material layer of the sample device is thickened; a negative electrode plate removal step of dismantling the deteriorated sample device and removing the negative electrode plate; a removing step of washing and removing the electrolyte adhering to the removed negative electrode plate; a Li amount distribution acquisition step of examining a linear distribution or a planar distribution of the Li amount contained in the Li-containing SEI coating of the coating-coated negative electrode active material layer in a width direction or a length direction; and a determining step of determining whether the sample device is good or bad from the undetermined device group based on the obtained distribution of the amount of Li. A method for manufacturing a group of devices.

4. 4. A method for manufacturing a group of devices according to claim 3, comprising the steps of: the electrolyte is a P-containing electrolyte containing a supporting salt containing phosphorus, The coated negative electrode active material layer of the negative electrode plate is the Li-containing SEI coating, which is a LiP-containing SEI coating that also contains phosphorus, is formed on a negative electrode active material layer that does not contain phosphorus, a P amount distribution acquisition step, which is performed instead of the Li amount distribution acquisition step or together with the Li amount distribution acquisition step, of examining a linear distribution or a planar distribution of the P amount contained in the LiP-containing SEI coating of the coated negative electrode active material layer in the width direction or the longitudinal direction; The determination step includes: The pass / fail judgment of the undetermined device group from which the sample device was obtained is performed using the P content distribution instead of or in addition to the Li content distribution. A method for manufacturing a group of devices.

5. 4. A method for manufacturing a group of devices according to claim 3, comprising the steps of: The determination step includes: The minimum and maximum values ​​of the Li amount in the obtained distribution of the Li amount are used to determine the quality of the undetermined devices. A method for manufacturing a group of devices.

6. 5. A method for manufacturing a group of devices according to claim 4, comprising the steps of: The determination step includes: Using the minimum and maximum P amounts in the obtained P amount distribution, or Using the minimum value of the P amount, the maximum value of the P amount, and the minimum value of the Li amount and the maximum value of the Li amount in the obtained distribution of the Li amount, The pass / fail judgment of the unjudged devices is performed. A method for manufacturing a group of devices.

7. A method for manufacturing a device group according to any one of claims 3 to 6, comprising: The degradation step includes: reducing the capacity of the sample device until the capacity retention rate is less than a predetermined value. A method for manufacturing a group of devices.

Images