Secondary battery inspection method and secondary battery manufacturing method

Abstract

To provide a method for checking a secondary battery that can appropriately check a capacity to be checked of the secondary battery, and a method for manufacturing the secondary battery using the same.SOLUTION: The method for checking a secondary battery 1 provided with a case 5 and an electrode body 2 includes: an SOC adjustment step S51 of adjusting an SOC of the secondary battery to an SOC at start of checking; a measurement step S52 of capacity to be checked, which measures the capacity CP to be checked by performing constant current charging or constant current discharging on the secondary battery, over an SOC checking range from the SOC at start of checking to an SOC at end of checking; a gas correlation amount acquiring step S53 of acquiring a gas correlation amount SG which has a correlation with a gas amount GSA interposing between a positive electrode plate 2P and a negative electrode plate 2N of the electrode body; a correction step S54 of acquiring a capacity correction value ΔCP corresponding to the acquired gas correlation amount SG, based on a relationship between the gas correlation amount SG and the capacity correction value ΔCP acquired in advance, and acquiring a checked capacity CPp after correction, from the capacity CP to be checked and the capacity correction value ΔCP; and a determination step S55 of determining a quality of the secondary battery, with the use of the checked capacity CPp after the correction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting a secondary battery and a method for manufacturing a secondary battery. [Background technology]

[0002] When manufacturing a secondary battery, a capacity test is sometimes performed to determine whether the secondary battery is good or bad, using the capacity of the secondary battery as an index. For example, Patent Document 1 discloses a method for manufacturing a secondary battery in which a capacity test step is performed after an initial charging step, a high-temperature aging step, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-015745 Summary of the Invention [Problem to be solved by the invention]

[0004] However, during the manufacture of secondary batteries, gas generated during the initial charging process or other processes may accumulate in a layer between the positive and negative electrode plates of the electrode assembly, which face each other via a separator, and may not be able to fully escape to the outside. When a capacity test is performed on a secondary battery containing such a gas layer within the electrode assembly, the test capacity obtained is smaller than the test capacity of a secondary battery that does not contain a gas layer. For this reason, it has been found that the quality of a secondary battery cannot be properly determined based on the test capacity.

[0005] The present invention has been made in consideration of the current situation, and provides a method for inspecting a secondary battery that can appropriately inspect the inspection capacity of a secondary battery, and a method for manufacturing a secondary battery using the same. [Means for solving the problem]

[0006] (1) One aspect of the present invention for solving the above problem is a method for testing a secondary battery having a case and an electrode assembly housed in the case, the method comprising: an SOC adjustment step for adjusting the SOC of the secondary battery to a test start SOC; an test capacity measurement step for measuring a test capacity by performing constant current charging or constant current discharging on the secondary battery over a test SOC range from the test start SOC to the test end SOC, which is a portion of the SOC range of 0% to 100% SOC; a gas correlation quantity acquisition step for acquiring a gas correlation quantity that has a correlation with the amount of gas present between the positive and negative electrode plates of the electrode assembly; a correction step for obtaining a capacity correction value corresponding to the acquired gas correlation quantity based on a relationship between the gas correlation quantity and a capacity correction value that has been obtained in advance, and obtaining a corrected test capacity from the measured test capacity and the capacity correction value; and a determination step for determining whether the secondary battery is good or bad using the corrected test capacity.

[0007] In this secondary battery inspection, in addition to measuring the test capacity of the secondary battery, a gas correlation quantity that correlates with the amount of gas in the electrode body is obtained, and a capacity correction value is obtained based on the relationship between the gas correlation quantity and the capacity correction value. A corrected test capacity is then obtained from the test capacity and the capacity correction value, and the quality of the secondary battery is determined using the corrected test capacity. Thus, for secondary batteries with different amounts of gas in the electrode body, the test capacity can be appropriately corrected for each, and the quality of the secondary battery can be appropriately determined based on the corrected test capacity.

[0008] Examples of secondary batteries include lithium ion secondary batteries, sodium ion secondary batteries, calcium ion secondary batteries, etc. Examples of electrode bodies for secondary batteries include stacked electrode bodies, cylindrical wound electrode bodies, and flat wound electrode bodies.

[0009] The test start SOC, test end SOC, and test SOC range may be selected from an SOC range of 0 to 100%. However, selecting a wider test SOC range increases the amount of electricity charged or discharged by the constant-current charge or constant-current discharge in the test capacity measurement step, and the test time increases. For this reason, the test start SOC and test end SOC should be selected so that the test SOC range is, for example, 50% or less, preferably 20% or less. Furthermore, the larger the test current passed through the secondary battery during constant-current charge or constant-current discharge, the shorter the time required to complete the constant-current charge or constant-current discharge. Therefore, the test current should be, for example, 1 C or more, preferably 5 C or more, but not more than the maximum current that can be passed through the secondary battery.

[0010] As the gas correlation quantity correlated with the amount of gas in the electrode body, any appropriate physical quantity can be used as long as it is a gas correlation quantity that changes depending on the amount of gas in the electrode body. For example, the transmission intensity of ultrasonic waves irradiated from outside and transmitted through the electrode body of a secondary battery can be measured at each predetermined position of the electrode body or over the entire predetermined area of ​​the electrode body, and the obtained transmission intensity values ​​can be integrated or averaged. Furthermore, in a stacked or flat wound electrode body, the elasticity value in the thickness direction at each position of the electrode body can be measured, and the obtained integrated value of the elasticity value can be used.

[0011] (2) In the energy storage device described in (1) above, the gas correlation quantity acquisition process may be an ultrasonic irradiation process for obtaining the gas correlation quantity based on the transmission intensity of ultrasonic waves irradiated to the secondary battery and transmitted through the electrode body.

[0012] When ultrasonic waves are irradiated onto a secondary battery from the outside, the intensity of the transmitted ultrasonic waves that pass through the electrode body is lower in the part of the electrode body where a gas layer is present than in the part where there is no gas layer. This is because a part of the transmitted ultrasonic waves is reflected by the gas layer. Therefore, if a gas correlation quantity that correlates with the gas amount is obtained from the transmitted ultrasonic intensity in the ultrasonic irradiation process, the test capacity can be appropriately corrected according to the gas amount.

[0013] As mentioned above, examples of gas correlation quantities include the integrated value or average value obtained by measuring the transmitted intensity of ultrasound at each predetermined position on the electrode body or over the entire predetermined area of ​​the electrode body and accumulating the obtained intensity values.

[0014] (3) In the method for inspecting a secondary battery described in (1) or (2) above, the inspection capacity measurement step may be a method for inspecting a secondary battery in which the inspection capacity is measured by performing constant current charging or constant current discharging at an inspection current of 5 C or more over the inspection SOC range of 20% or less.

[0015] In the test capacity measurement step of this test method, the test capacity is measured by constant-current charging or constant-current discharging at a test current of 5 C or more over a test SOC range of 20% or less. By measuring the test capacity at a large test current over a narrow test SOC range, the test capacity measurement step can be completed in a short time. However, it has been found that measuring the test capacity at a large test current over such a narrow test SOC range can easily cause the resulting test capacity to vary depending on the amount of gas in the electrode body. Localized battery action is unlikely to occur in areas where a gas layer exists between the positive and negative electrode plates. This is thought to be why the secondary battery is less likely to be charged or discharged at a large test current in a short time, resulting in a small test capacity. In contrast, in the present invention, a capacity correction value corresponding to the gas correlation quantity is obtained in the correction process, and a corrected test capacity is obtained from the measured test capacity and the capacity correction value, so that the decrease in test capacity due to the presence of a gas layer can be corrected, and the quality of the secondary battery can be appropriately determined in the judgment process.

[0016] (4) Another solution is a method for manufacturing a secondary battery, comprising an inspection step of inspecting a secondary battery whose inspection capacity has not been inspected by the secondary battery inspection method described in any one of (1) to (3), and a sorting step of retaining the secondary batteries that have been judged as good in the judgment step.

[0017] In this method of manufacturing a secondary battery, secondary batteries whose test capacity has not yet been inspected are inspected using the inspection method described above, and secondary batteries that are judged to be good in the sorting process are retained, so that the test capacity is inspected appropriately, and secondary batteries with good test capacity can be manufactured. [Brief explanation of the drawings]

[0018] [Figure 1] 3 is a flowchart showing the procedure for inspecting and manufacturing a battery according to an embodiment. [Figure 2] 10A and 10B are explanatory diagrams illustrating how the intensity of ultrasonic waves transmitted through a battery is acquired in an ultrasonic irradiation step according to an embodiment. [Figure 3] 10 is a graph showing the relationship between the integrated value of the intensity of the obtained transmitted ultrasonic waves and the capacitance correction value. [Figure 4] FIG. 10 is an explanatory diagram showing an example of the test capacity and corrected test capacity of each sample battery. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Embodiment) A lithium ion secondary battery (hereinafter simply referred to as battery) 1 according to an embodiment of the present invention will be described below with reference to Figures 1 to 4. Battery 1 is a rectangular, sealed lithium ion secondary battery, and is installed in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars, as well as in various devices.

[0020] The battery 1 (see FIG. 2 ) of this embodiment is composed of a case 5, an electrode assembly 2 housed inside the case 5, a positive electrode terminal 6P and a negative electrode terminal 6N fixed to the case 5, and an insulating member (not shown) that insulates these from the case 5. The case 5 is made of metal (aluminum in this embodiment) and has a rectangular box shape. The electrode assembly 2 is covered in a bag-shaped insulating film (not shown) inside the case 5. The case 5 also contains an electrolyte solution 3, a portion of which is impregnated in the electrode assembly 2 and a portion of which is pooled at the bottom of the case 5. In this embodiment, the vertical direction in FIG. 2 is referred to as a height direction HH, the left-right direction as a thickness direction TH, and the front-rear direction perpendicular to the paper surface as a width direction WH.

[0021] The electrode assembly 2 housed in the case 5 is a so-called flat wound electrode assembly, which is made by winding a strip-shaped positive electrode plate 2P and a strip-shaped negative electrode plate 2N with a pair of strip-shaped separators 2S interposed between them and pressing them flat in the thickness direction TH (left-right direction in the figure) in Fig. 2. This electrode assembly 2 is housed in the case 5 in a horizontal position with its axis 2X coinciding with the width direction WH.

[0022] The positive electrode terminal 6P is made of an aluminum plate, and is connected to a positive electrode current collector (not shown) of the electrode body 2 inside the case 5, and is also drawn out to the outside of the case 5. The negative electrode terminal 6N is made of a copper plate, and is connected to a negative electrode current collector (not shown) of the electrode body 2 inside the case 5, and is also drawn out to the outside of the case 5.

[0023] As described below, after the initial charging step S2, the battery 1 may have a gas layer GS, where gas such as hydrogen accumulates, locally formed between the positive electrode plate 2P and the negative electrode plate 2N via the separator 2S in various locations within the electrode assembly 2. This is thought to be because the gas generated during the initial charging step was unable to escape to the outside of the electrode assembly 2. In this case, it is thought that the battery reaction is locally difficult to occur in the gas interposed portion 2G between the positive electrode plate 2P and the negative electrode plate 2N, where the gas layer GS is present. Therefore, when a battery 1 having a gas interposed portion 2G is charged or discharged for a short period of time, particularly when the battery is charged or discharged for a short period of time with a large charging or discharging current, resulting in a small change in SOC, the gas interposed portion 2G does not contribute to the charging or discharging, and the capacity of the battery 1 appears to be reduced.

[0024] However, even if a gas-interposed portion 2G is formed in the electrode body 2 of the battery 1, when the battery is charged or discharged for a long period of time, for example, when a small charging or discharging current is used for a long period of time, causing a large change in SOC (for example, a change over the entire range of SOC from 0 to 100%), there is not much difference in the amount of electricity charged or discharged compared to a battery 1 that does not have a gas-interposed portion 2G. This is thought to be because the gas-interposed portion 2G also contributes to charging or discharging through the area surrounding the gas-interposed portion 2G due to the diffusion of Li ions in the positive electrode active material layer or negative electrode active material layer.

[0025] Incidentally, when inspecting the capacity of manufactured batteries 1 and selecting only good batteries 1, the test capacity CP of the battery 1 may be measured. In this case, to measure the test capacity CP of the battery 1 in a short time and determine whether the battery 1 is good or bad, a large charge or discharge current Ich is passed as the test current, and the battery 1 is charged or discharged for only a short time, causing a small change in SOC. However, as described above, when measuring this test capacity CP, if the battery 1 contains a gas-containing portion 2G, the obtained test capacity CP is affected by the presence of the gas-containing portion 2G and is measured as an apparently small value. As a result, a battery 1 that should have been determined to be good may be determined to be defective, or a battery 1 that should have been determined to be defective may be determined to be good.

[0026] Therefore, in the manufacturing process of the battery 1 of this embodiment described below and in the inspection process S5 therein, the inspection capacity CP is corrected, and the corrected inspection capacity CPp is used to determine the quality of the battery 1. The manufacturing of the battery 1 according to this embodiment will be described below (see FIGS. 1 and 2).

[0027] First, in the uncharged battery assembly step S1, an uncharged battery 1 is assembled. Specifically, an electrode body 2 is fabricated, and a positive electrode terminal 6P and a negative electrode terminal 6N fixed to the case lid 5L are connected to a positive electrode current collector and a negative electrode current collector (not shown) of the electrode body 2, respectively. The electrode body 2 is covered with a bag-shaped insulating film (not shown) and housed in the case body 5B. The entire periphery of the case lid 5L is laser welded to the case body 5B to form the case 5. Furthermore, an electrolyte 3 is injected into the case 5 through an injection hole (not shown) provided in the case lid 5L, and the electrode body 2 is impregnated with the electrolyte 3.

[0028] Thereafter, in the initial charging step S2, the battery 1 is initially charged. Specifically, CC charging is performed at a constant current value of 10 C until the SOC reaches 80%. As a result, an SEI coating is formed on the surfaces of the negative electrode active material particles (not shown) of the negative electrode plate 2N and the positive electrode active material particles (not shown) of the positive electrode plate 2P, which are generated by decomposition of a portion of the electrolyte 3. Most of the gases generated during this initial charging, such as hydrogen gas, are released to the outside of the electrode body 2 through between the positive electrode plate 2P and the negative electrode plate 2N. However, among the batteries 1, as shown in FIG. 2, there are cases in which gas accumulates between the positive electrode plate 2P and the negative electrode plate 2N in various locations of the electrode body 2, forming a gas layer GS.

[0029] After the initial charging step S2, in the sealing step S3, a filling plug (not shown) is welded to the filling hole to airtightly seal the case 5. Furthermore, in the high-temperature aging step S4, the battery 1 is left in an environment of 60°C for 20 hours.

[0030] Then, in the inspection process S5, the quality of the battery 1 is inspected based on the inspection capacity CP. Specifically, first, in the SOC adjustment process S51, the SOC of the battery 1 is charged to 90% by CCCV charging at 10C (cut off at 1 hour) in a room temperature environment, and the inspection start SOC of each battery 1 is adjusted to 90%.

[0031] Next, in the test capacity measurement step S52, the magnitude of the CC discharge test current Ich is set to 5C or more, specifically 10C. Then, the battery 1 is CC discharged over a range of 20% or less from the test start SOC to the test end SOC, specifically a 10% test SOC range from 90% to 80% SOC. This test capacity measurement step S52 takes a short time, approximately 6 minutes, because discharge is terminated after CC discharge only, and no CV discharge is performed. The amount of electricity discharged from the battery 1 during this time is obtained as the test capacity CP.

[0032] Next, in an ultrasonic irradiation step (a type of gas correlation quantity acquisition step) S53, an integrated value SG of transmitted ultrasonic intensity IG, which correlates with the gas amount GSA in the electrode body 2, is obtained as shown in Figure 2. Specifically, first, the battery 1 is placed on a movable table MT. This movable table MT is a table that can move the placed battery 1 in a height direction HH (up and down in Figure 2) and a width direction WH (direction perpendicular to the paper surface in Figure 2).

[0033] An ultrasonic transmitter UST connected to a controller CTL and directed in the thickness direction TH emits irradiated ultrasonic waves US1 toward a battery 1 placed on a movable table MT. A portion of the irradiated ultrasonic waves US1 irradiated toward the battery 1 passes through the case 5 and the electrode body 2 in the thickness direction TH as passing ultrasonic waves US2 and is emitted from the battery 1 as transmitted ultrasonic waves US3. The transmitted ultrasonic waves US3 are received by an ultrasonic receiver USR, and the magnitude of the transmitted ultrasonic wave intensity IG, which is the intensity of the transmitted ultrasonic waves US3, is acquired by the controller CTL. In this embodiment, the ultrasonic transmitter UST and ultrasonic receiver USR are used at a distance from the battery 1, but they may also be used in contact with the battery 1.

[0034] If a gas layer GS exists within the electrode body 2 and exists on the path of the passing ultrasonic wave US2, the acoustic impedance of the gas layer GS is significantly different from the acoustic impedance of the positive electrode plate 2P, negative electrode plate 2N, separator 2S, and other components impregnated with the electrolyte 3 that make up the electrode body 2. As a result, a portion of the passing ultrasonic wave US2 is reflected at the interface between the gas layer GS and the positive electrode plate 2P. This reduces the transmitted ultrasonic wave intensity IG of the transmitted ultrasonic wave US3 that reaches the ultrasonic receiver USR compared to when no gas layer GS exists on the path of the passing ultrasonic wave US2. It is believed that the greater the number of gas layers GS on the path of the passing ultrasonic wave US2, i.e., the greater the gas volume GSA, the greater the degree of reduction in the transmitted ultrasonic wave intensity IG. In other words, the transmitted ultrasonic wave intensity IG is a value that correlates with the gas volume GSA in the area through which the passing ultrasonic wave US2 passes.

[0035] The gas layer GS is also considered to exist locally within the electrode assembly 2. This is because the gas layer GS is formed when gas generated by the formation of an SEI coating on each positive electrode plate 2P or negative electrode plate 2N accumulates between the positive electrode plate 2P and the negative electrode plate 2N. Therefore, the battery 1 is moved in the height direction HH and the width direction WH using the movable table MT, and the transmitted ultrasonic intensity IG is measured at multiple locations on the battery 1 where flat portions of the electrode assembly 2 exist in the thickness direction TH. For example, the battery 1 is moved using the movable table MT to obtain the transmitted ultrasonic intensity IG at a total of 50 locations, including five levels in the height direction HH and ten levels in the width direction WH. The sum of these values ​​is then used as the integrated value SG of the transmitted ultrasonic intensity IG. This integrated value SG correlates with the gas amount GSA throughout the electrode assembly 2. Using this integrated value SG, the test capacitance CP can be appropriately corrected according to the gas amount GSA, as described below.

[0036] However, as mentioned above, even if a gas-containing portion 2G is present within the electrode body 2 of the battery 1, if charging or discharging is performed over a long period of time with a small charging or discharging current, causing a large change in SOC (for example, the entire range of SOC from 0 to 100%), it has been found that there is not much difference in the amount of electricity charged or discharged compared to a battery 1 that does not have a gas-containing portion 2G.

[0037] Therefore, in this embodiment, the aforementioned test capacity CP and the integrated value SG of the transmitted ultrasonic wave intensity IG were obtained in advance for multiple sample batteries 1. In addition, the discharge capacity of each battery 1 was measured by CCCV discharge (3-hour cutoff) from SOC 100% to 0%, with a discharge current of 1 / 2C during CC discharge. As described above, this discharge capacity value is measured by long-term discharge at a small discharge current (1 / 2C or less in this embodiment) over a wide SOC range from 100% to 0%, and is therefore not easily affected by the presence or absence of a gas-containing portion 2G in the electrode body 2 of the battery 1. Therefore, from the multiple sample batteries 1, multiple batteries 1 (three in this embodiment) with approximately the same measured discharge capacity values ​​were selected. Note that hereinafter, the three selected batteries 1 are referred to as sample batteries SP1 to SP3. The graph in Figure 3 plots the integrated values ​​SG and differences ΔCP of each sample battery SP1 to SP3, with the test capacity CP obtained for sample battery SP1, which had the largest integrated value SG of transmitted ultrasonic wave intensity IG, as the reference value, and the difference in test capacity CP between sample battery SP1 and sample battery SP2, and the difference in test capacity CP between sample battery SP1 and sample battery SP3 as ΔCP.

[0038] Figure 3 shows that, even though the sample batteries SP1 to SP3 have approximately the same discharge capacity, differences in the integrated value SG, which is a gas correlation quantity, result in differences in the test capacity CP. Since the sample batteries SP1 to SP3 have approximately the same discharge capacity, if the gas amounts GSA contained in the electrode assembly 2 were approximately the same, it is presumed that the obtained test capacity CP values ​​would also be approximately the same. Therefore, for sample batteries SP2 and SP3, adding the aforementioned difference ΔCP to the obtained test capacity CP can be corrected to be the same as the test capacity CP of sample battery SP1, which has a smaller gas amount GSA. In other words, Figure 3 shows that the difference ΔCP can be used as a capacity correction value to correct the obtained test capacity CP to be the same as the test capacity CP of sample battery SP1, which has a smaller gas amount GSA, depending on the integrated value SG.

[0039] Therefore, in this embodiment, after obtaining the integrated value SG in the ultrasonic irradiation step S53, in the correction step S54, a capacity correction value ΔCP corresponding to the integrated value SG is obtained using the graph in FIG. 3, and a correction is performed by adding this to the test capacity CP to calculate the corrected test capacity CPp (CPp = CP + ΔCP). For example, FIG. 4 shows the test capacity CP and the corrected test capacity CPp obtained for sample batteries SP1 to SP4. In FIG. 4, the corrected test capacity CPp of sample battery SP1 is equal to the test capacity CP. It can also be seen that the corrected test capacity CPp of sample batteries SP2 and SP3 is approximately equal to the corrected test capacity CPp of sample battery SP1.

[0040] In FIG. 4, CPmin indicates the lower capacity limit, and CPmax indicates the upper capacity limit. That is, the range between CPmin and CPmax, sandwiched between two dashed lines, is the pass range CPG for the test capacity CP (corrected test capacity CPp). Looking at the test capacity CP before correction, both the test capacity CP and the corrected test capacity CPp of sample batteries SP1 and SP2 are within the pass range CPG. However, the test capacity CP of sample battery SP3 is outside the pass range CPG. This is because the amount of gas GSA contained in the electrode assembly 2 is large, resulting in a small test capacity CP. In contrast, the corrected test capacity CPp of sample battery SP3 is found to be within the pass range CPG. Thus, according to this embodiment, calculation of the corrected test capacity CPp can prevent a battery 1 that should be considered a good product from being judged as defective.

[0041] However, as in the case of sample battery SP4, the test capacity CP was within the pass range CPG, but the corrected test capacity CPp was outside the pass range CPG. Thus, according to this embodiment, by calculating the corrected test capacity CPp, it is possible to prevent the problem of determining a battery 1 that should actually be considered defective as a good product.

[0042] Therefore, in the judgment step S55, the calculated corrected test capacity CPp is used to judge the quality of the battery 1. Specifically, as described above, it is determined whether the corrected test capacity CPp falls within the pass range CPG. Thus, in the inspection step S5, the quality of the battery 1 can be appropriately judged based on the corrected test capacity CPp.

[0043] Thereafter, in the sorting step S6, batteries 1 judged as good (OK) in the judgment step S55 are kept, and batteries 1 judged as bad (NG) are excluded as bad. In this way, good batteries 1 whose corrected test capacity CPp falls within the pass range CPG can be manufactured.

[0044] The present invention has been described above in accordance with the embodiments and Examples 1 to 6, etc. However, the present invention is not limited to the embodiments, etc., and can be modified and applied as appropriate within the scope of the gist of the present invention. For example, in the embodiment, in the ultrasonic irradiation step S53, the integrated value SG of the transmitted ultrasonic intensity IG is obtained, but instead, the average value of the transmitted ultrasonic intensity IG may be calculated and used to carry out the subsequent steps. [Explanation of symbols]

[0045] 1,SP1,SP2,SP3 battery (secondary battery) 2 Electrode body 2X (electrode body) central axis 2P positive electrode plate 2N negative electrode plate 2G Gas-containing section GS gas reservoir GSA gas volume US3 transmission ultrasound IG transmitted ultrasound intensity SG (Transmitted ultrasonic intensity) integrated value (gas correlation amount) S4 High temperature aging process S5 Inspection process S51 SOC adjustment process S52 Inspection volume measurement process S53 Ultrasonic irradiation process (gas correlation quantity acquisition process) S54 Correction process S55 Judgment process S6 Sorting process CP Inspection Capacity ΔCP capacitance correction value CPp corrected test volume CPG pass range

Claims

1. A method for inspecting a secondary battery including a case and an electrode assembly housed in the case, comprising: an SOC adjusting step of adjusting the SOC of the secondary battery to an inspection start SOC; a test capacity measurement step of measuring a test capacity by performing constant current charging or constant current discharging on the secondary battery over a test SOC range from the test start SOC to the test end SOC, which is a part of an SOC range from 0% to 100% SOC; a gas correlation quantity acquisition step of acquiring a gas correlation quantity correlated with the amount of gas present between the positive electrode plate and the negative electrode plate of the electrode body; a correction step of obtaining the capacitance correction value corresponding to the acquired gas correlation quantity based on a relationship between the gas correlation quantity and a capacitance correction value obtained in advance, and obtaining a corrected test capacitance from the measured test capacitance and the capacitance correction value; and a determining step of determining whether the secondary battery is good or bad using the corrected inspection capacity. Inspection method for secondary batteries.

2. 2. The method for inspecting a secondary battery according to claim 1, The gas correlation quantity acquisition step includes: an ultrasonic irradiation step of obtaining the gas correlation quantity based on the transmission intensity of ultrasonic waves that are irradiated to the secondary battery and transmitted through the electrode body; Inspection method for secondary batteries.

3. 2. The method for inspecting a secondary battery according to claim 1, The test capacitance measuring step includes: The test capacity is measured by performing a constant current charge or discharge at a test current of 5 C or more over the test SOC range of 20% or less. Inspection method for secondary batteries.

4. an inspection step of inspecting a secondary battery whose inspection capacity has not yet been inspected by the method for inspecting a secondary battery according to any one of claims 1 to 3; a sorting step of retaining the secondary batteries that have been determined to be good in the determination step. A method for manufacturing a secondary battery.

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