JP2014192015A - Method for inspecting lithium ion secondary battery and method for manufacturing lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting a lithium ion secondary battery capable of accurately selecting a defective lithium ion secondary battery in an aging process, and a method for manufacturing the lithium ion secondary battery.SOLUTION: In this method for inspecting a lithium ion secondary battery, determination is made that a lithium ion secondary battery whose voltage difference ΔV2 which is a reduction amount of battery voltage in second aging is equal to or greater than a threshold for the voltage difference ΔV2 is defective. As the threshold for the voltage difference ΔV2, a lower value is used in correspondence to an increase in a voltage difference ΔV1 which is a reduction amount of battery voltage in first aging prior to the second aging.

Description

  The present invention relates to an inspection method and a manufacturing method for a lithium ion secondary battery. More specifically, the present invention relates to an inspection method and a manufacturing method of a lithium ion secondary battery that performs selection between a non-defective product and a defective product during an aging process.

  In the manufacturing process of the lithium ion secondary battery, an aging process or the like is performed in order to bring the assembled lithium ion secondary battery into a state in which good battery performance is stably exhibited. The aging process is performed by leaving the lithium ion secondary battery in a predetermined temperature environment.

  In the aging process, the battery voltage of the lithium ion secondary battery is reduced by self-discharge. The amount of decrease in the battery voltage is different between a non-defective product and a defective product. For this reason, conventionally, there is known a method for determining whether or not a lithium ion secondary battery is a non-defective product based on the amount of decrease in battery voltage in the aging process.

  For example, Patent Document 1 discloses a battery that performs first aging and second aging, measures the battery voltage before and after the second aging, and determines the quality of the battery from the amount of decrease in the battery voltage in the second aging. An inspection method is disclosed. In the battery inspection method disclosed in Patent Document 1, a battery in which the amount of decrease in battery voltage in the second aging is lower than a predetermined threshold is determined as a defective product.

JP 2009-4389 A

  By the way, even in the case of the same good or defective lithium ion secondary battery, the amount of decrease in battery voltage in the subsequent second aging may be different depending on the conditions of the first aging. Therefore, depending on the conventional inspection method that does not take this into account, there is a risk that a non-defective product and a defective product are erroneously determined.

  The present invention has been made for the purpose of solving the problems of the prior art described above. That is, the problem is to provide a method for inspecting a lithium ion secondary battery and a method for manufacturing a lithium ion secondary battery that can accurately select defective lithium ion secondary batteries in the aging process. is there.

  The inspection method for a lithium ion secondary battery of the present invention, which has been made for the purpose of solving this problem, performs the first aging on the aging treatment by leaving the lithium ion secondary battery under a predetermined condition, The battery voltage is measured after aging 1 and the measured value is set as the first battery voltage, the second aging is performed after the first battery voltage is measured, and the battery voltage is measured after the second aging. The measured value is the second battery voltage, and a lithium ion secondary battery in which the voltage difference between the first battery voltage and the second battery voltage is equal to or greater than a predetermined voltage difference threshold is determined to be a defective product. In this method, the battery voltage before the first aging is used as a reference voltage, and the voltage difference threshold value is lower as the voltage difference between the reference voltage and the first battery voltage is higher. The It is a test method of a lithium ion secondary battery, characterized in that there.

  In the method for inspecting a lithium ion secondary battery of the present invention, a lithium ion secondary battery in which the voltage difference between the first battery voltage and the second battery voltage is equal to or greater than the voltage difference threshold is determined as a defective product. Here, the voltage difference between the first battery voltage and the second battery voltage is the same as the lithium ion secondary battery in which there is no pause in the first aging. It becomes a lower value than. Also, the longer the pause time in the first aging and the greater the number of pauses, the lower the voltage difference between the first battery voltage and the second battery voltage. For this reason, even if it is a defective lithium ion secondary battery, depending on the resting conditions in the first aging, the voltage between the first battery voltage and the second battery voltage is higher than that of a good lithium ion secondary battery. The difference may be low.

  However, when there is a pause in the first aging, the voltage difference between the reference voltage and the first battery voltage is higher than when there is no pause in the first aging. Furthermore, the longer the pause time in the first aging and the greater the number of pauses, the higher the voltage difference between the reference voltage and the first battery voltage. This is because the amount of self-discharge increases as the amount of heat given to the lithium ion secondary battery in the first aging increases, and thereby the value of the first battery voltage decreases. Therefore, by using a lower value as the voltage difference between the reference voltage and the first battery voltage is higher as the voltage difference threshold, based on the voltage difference between the first battery voltage and the second battery voltage, A defective lithium ion secondary battery can be selected.

  The present invention also provides a lithium ion secondary battery comprising: a positive and negative electrode plate, an electrode body formed by winding or flat stacking with a separator interposed therebetween, and an electrolyte solution enclosed in a battery container. In the battery manufacturing method, after the electrode body and the electrolyte solution are sealed in the battery container, the lithium ion secondary battery inspection method described above is performed to eliminate the lithium ion secondary battery determined to be defective. The present invention also extends to a method for manufacturing a lithium ion secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection method of a lithium ion secondary battery and the manufacturing method of a lithium ion secondary battery which can select correctly a defective lithium ion secondary battery in an aging process are provided.

It is sectional drawing which shows the secondary battery which concerns on this form. It is a perspective view of the electrode body which concerns on this form. It is a figure which shows the positive electrode plate which comprises the same electrode body. It is a figure which shows the negative electrode plate which comprises the same electrode body. It is a figure explaining the overlapping state of the positive / negative electrode plate etc. in the same electrode body. It is the figure which showed transition of the temperature of a secondary battery when there existed a stop in 1st aging. It is the figure which showed the fall amount of the battery voltage in the 2nd aging of the secondary battery which is all inferior goods for every power failure number in the 1st aging. It is a flowchart which shows the procedure of the quality determination of the secondary battery in an aging process. It is a figure for performing a comparison with this form and a conventional example about a threshold used for quality determination of a rechargeable battery in an aging process.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the drawings.

  First, the secondary battery 10 (refer FIG. 1) manufactured by the manufacturing method of the lithium ion secondary battery of this form is demonstrated. FIG. 1 is a cross-sectional view of a secondary battery 10 according to this embodiment. The secondary battery 10 is a lithium ion secondary battery in which an electrode body 20 and an electrolytic solution 30 are accommodated in a battery case 40 as shown in a cross section in FIG. The electrolytic solution 30 is obtained by dissolving a lithium salt in an organic solvent. The battery case 40 includes a battery case main body 41 and a sealing plate 42. In addition, the sealing plate 42 includes an insulating member 43.

  FIG. 2 is a perspective view of the electrode body 20 before being assembled as the secondary battery 10. The electrode body 20 is a flat electrode body obtained by winding a positive electrode plate 70, a negative electrode plate 80, and a separator 90 into a flat shape (see FIGS. 2 to 5).

  As shown in FIG. 3, the positive electrode plate 70 has a strip shape that is long in the longitudinal direction DA. The positive electrode plate 70 includes a positive electrode current collector foil 75 made of an aluminum foil and a positive electrode mixture layer 76 formed on a part of the positive electrode current collector foil 75. The positive electrode mixture layer 76 contains a positive electrode active material that can occlude and release lithium ions. In addition, a portion of the positive electrode current collector foil 75 where the positive electrode mixture layer 76 is not formed is referred to as a positive electrode mixture layer non-forming portion 71. On the other hand, a portion where the positive electrode mixture layer 76 is formed is referred to as a positive electrode mixture layer forming portion 72.

  As shown in FIG. 3, the positive electrode mixture layer non-forming portion 71 is located at the left end of the positive electrode plate 70 in the width direction DB (left and right direction in FIG. 3). The positive electrode mixture layer forming portion 72 is located at the right end of the positive electrode plate 70 in the width direction DB. Each of the positive electrode mixture layer non-forming portion 71 and the positive electrode mixture layer forming portion 72 extends in a band shape along the one long side of the positive electrode plate 70 in the longitudinal direction DA (vertical direction in FIG. 3) of the positive electrode plate 70. Yes.

  As shown in FIG. 4, the negative electrode plate 80 has a strip shape that is long in the longitudinal direction DA. The negative electrode plate 80 includes a negative electrode current collector foil 85 made of a copper foil, and a negative electrode mixture layer 86 formed on a part of the negative electrode current collector foil 85. The negative electrode mixture layer 86 contains a negative electrode active material that can occlude and release lithium ions. In addition, a portion of the negative electrode current collector foil 85 where the negative electrode mixture layer 86 is not formed is referred to as a negative electrode mixture layer non-forming portion 81. On the other hand, a portion where the negative electrode mixture layer 86 is formed is referred to as a negative electrode mixture layer forming portion 82. The positive electrode mixture layer 76 and the negative electrode mixture layer 86 are suitably used for fixing a conductive additive for enhancing the conductivity in the electrode mixture layer, an electrode active material, etc. on the current collector foil. It is preferable that a binder or the like is included.

  As shown in FIG. 4, the negative electrode mixture layer non-forming portion 81 is located at the left end of the negative electrode plate 80 in the width direction DB (left and right direction in FIG. 4). The negative electrode mixture layer forming portion 82 is located at the right end of the negative electrode plate 80 in the width direction DB. Each of the negative electrode mixture layer non-forming portion 81 and the negative electrode mixture layer forming portion 82 extends in a band shape along the one long side of the negative electrode plate 80 in the longitudinal direction DA (vertical direction in FIG. 4) of the negative electrode plate 80. Yes.

  The electrode body 20 shown in FIG. 2 is obtained by winding a positive electrode plate 70, a negative electrode plate 80, and a separator 90 while overlapping each other as shown in FIG. In the superposition shown in FIG. 5, the positive electrode plate 70, the negative electrode plate 80, and the two separators 90 are superposed.

  The separator 90 is a porous member that can transmit lithium ions. As the separator 90, a porous film made of polypropylene (PP), polyethylene (PE) or the like can be used alone, or a composite material obtained by laminating a plurality of these in the thickness direction can be used. The width of the separator 90 is substantially the same as the width of the positive electrode mixture layer forming portion 72 and the negative electrode mixture layer forming portion 82.

  As shown in FIG. 5, the positive electrode mixture layer non-forming portion 71 of the positive electrode plate 70 and the negative electrode mixture layer non-forming portion 81 of the negative electrode plate 80 are projected in opposite directions in the left-right direction of FIG. Has been placed. Therefore, in FIG. 2 showing the wound state, the positive electrode mixture layer non-forming portion 71 located at the left end is formed by superposing a plurality of positive electrode current collector foils 75. Further, the negative electrode mixture layer non-forming portion 81 located at the right end portion is obtained by superposing a plurality of negative electrode current collector foils 85.

  The power storage unit 21 located at the center in the left-right direction of the electrode body 20 in FIG. 2 has a positive electrode mixture layer forming unit 72, a negative electrode mixture layer forming unit 82, and a separator 90, as shown in FIG. It is the part that is wound around. For this reason, the electrical storage part 21 is a part which contributes to charging / discharging.

  In the secondary battery 10 shown in FIG. 1, a positive electrode terminal 50 is connected to the positive electrode mixture layer non-forming portion 71 of the electrode body 20. A negative electrode terminal 60 is connected to the negative electrode mixture layer non-forming portion 81 of the electrode body 20. In the positive electrode terminal 50 and the negative electrode terminal 60, ends 51 and 61 on the side not connected to the electrode body 20 are protruded to the outside of the battery case 40 through an insulating member 43 provided on the sealing plate 42. The secondary battery 10 performs charging and discharging in the power storage unit 21 of the electrode body 20 via the positive electrode terminal 50 and the negative electrode terminal 60.

  In such a manufacturing process of the secondary battery 10, after the assembling process constituting the secondary battery 10, the charge / discharge reaction of the secondary battery 10 is activated and a state in which good battery performance can be stably exhibited is obtained. Therefore, conditioning and aging processing are performed.

  In the assembly process of the secondary battery 10, first, a paste containing a positive electrode active material or the like is applied to a portion to be the positive electrode mixture layer forming portion 72 of the positive electrode current collector foil 75, and this is dried to obtain a positive electrode mixture layer. The positive electrode plate 70 is manufactured by forming 76. The negative electrode plate 80 can also be manufactured by the same method as the positive electrode plate 70. Next, the electrode body 20 is manufactured by winding the manufactured positive electrode plate 70 and the negative electrode plate 80 together with the separator 90. Subsequently, after the positive electrode terminal 50 and the negative electrode terminal 60 are connected to the manufactured electrode body 20, the battery body 40 is sealed together with the electrolytic solution 30. The secondary battery 10 is configured as described above.

  Conditioning is to charge and discharge the assembled secondary battery 10 at a relatively low current value. The aging process is performed by leaving the secondary battery 10 in a predetermined temperature environment. In the present embodiment, in the aging process of the secondary battery 10, the first aging and the second aging after the first aging are performed. Further, in the aging process, an inspection for selecting a non-defective secondary battery 10 and a defective secondary battery 10 is performed. This is because the defective secondary battery 10 is reliably removed at the stage of the manufacturing process.

  Specifically, the inspection of the secondary battery 10 in the aging process is performed by pass / fail determination based on the amount of decrease in the battery voltage due to the self-discharge of the secondary battery 10 in the second aging. The amount of decrease in the battery voltage of the secondary battery 10 in the second aging includes the voltage V1 of the secondary battery 10 after the first aging and before the second aging, and the voltage V2 of the secondary battery 10 after the second aging. And the voltage difference ΔV2 can be calculated by subtracting the voltage V2 from the voltage V1.

  In the defective secondary battery 10 in which an internal short circuit or the like has occurred, the amount of self-discharge in the second aging increases compared to the non-defective secondary battery 10. The greater the amount of self-discharge in the second aging, the greater the voltage difference ΔV2 between them. That is, the voltage difference ΔV2 in the second aging is larger in the defective secondary battery 10 than in the non-defective secondary battery 10. Therefore, in the pass / fail determination, the secondary battery 10 in which the calculated voltage difference ΔV2 is equal to or greater than the threshold value for the voltage difference ΔV2 can be determined as a defective product. The threshold value for the voltage difference ΔV2 can be calculated in advance by an experiment using a non-defective secondary battery 10 and a defective secondary battery 10.

  Here, the value of the voltage difference ΔV2 in the second aging becomes a different value depending on the condition of the first aging even in the same secondary battery 10. Specifically, when the voltage difference ΔV2 is paused during the first aging, the voltage difference ΔV2 is different from the normal value when there is no pause in the first aging. When the first aging is suspended, for example, when the first aging starts before the long vacation and ends after the long vacation, or during the first aging. For example, when a power failure occurs.

  FIG. 6 shows the transition of the temperature of the secondary battery 10 when there is a pause in the first aging. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates the temperature of the secondary battery 10. The horizontal axis of FIG. 6 shows the first aging start time as t0 and the end time as t3. On the vertical axis, the temperature of the first aging is shown as T1.

  In FIG. 6, the time when the first aging is suspended is indicated by t1. Furthermore, after the first aging is suspended, the time when the secondary aging 10 is resumed and the temperature of the secondary battery 10 becomes T1 again is indicated by t2. That is, the time obtained by subtracting the pause time from time t1 to time t2 from the time from time t0 to time t3 is the normal first aging time without pause. The amount of heat given to the secondary battery 10 during the downtime from the time t1 to the time t2 is an excessive amount of heat compared to the normal first aging.

  Here, in general, the greater the amount of heat applied, the greater the amount of self-discharge of the secondary battery 10. That is, the self-discharge amount of the secondary battery 10 is not 0 and the self-discharge continues during the downtime from the time t1 to the time t2.

  For this reason, the amount of self-discharge of the secondary battery 10 when there is a pause in the first aging is greater than during a normal time when there is no pause. Furthermore, the self-discharge amount of the secondary battery 10 in the first aging tends to increase as the pause time increases and the pause frequency increases. In addition, the value of the voltage V1 measured after the first aging and before the second aging becomes lower as the self-discharge amount in the first aging increases. That is, as the amount of heat given to the secondary battery 10 in the first aging increases, the value of the voltage difference ΔV1 that is the amount of decrease in the battery voltage in the first aging increases. The voltage difference ΔV1 can be calculated by subtracting the voltage V1 from the voltage V0 of the secondary battery 10 before the first aging.

  As the voltage difference ΔV1 is higher, the voltage difference ΔV2 is lower. When the value of the voltage difference ΔV1 is high, that is, when the value of the voltage V1 is low, the voltage difference ΔV2 is the difference between the voltage V1 and the voltage V2 measured after the second aging. For this reason, the value of the voltage difference ΔV2 of the secondary battery 10 when there is a pause in the first aging is a value lower than the value of the voltage difference ΔV2 of the secondary battery when there is no pause. Furthermore, the value of the voltage difference ΔV2 tends to be lower as the pause time in the first aging is longer and the pause frequency is larger.

  Therefore, in this embodiment, in the pass / fail determination of the secondary battery 10 in the aging process, the threshold value for the voltage difference ΔV2 is determined to be lower as the voltage difference ΔV1 is higher.

  FIG. 7 is a diagram showing the voltage difference ΔV <b> 2 of the secondary battery 10, which is a defective product, for each power failure during the first aging. As shown in FIG. 7, the voltage difference ΔV2 becomes lower as the number of power outages increases. This is because, as described above with reference to FIG. 6, the voltage difference ΔV2 in the second aging becomes lower as the number of pauses in the first aging increases.

  In FIG. 7, the threshold for the voltage difference ΔV2 is indicated by a solid line. As described above with reference to FIG. 6, in this embodiment, the threshold value for the voltage difference ΔV2 is determined to be lower as the value of the voltage difference ΔV1 is higher. Further, the value of the voltage difference ΔV1 becomes higher as the amount of heat given to the secondary battery 10 in the first aging increases. The amount of heat given to the secondary battery 10 in the first aging increases as the self-discharge amount increases as the number of pauses in the first aging increases. Therefore, as shown in FIG. 7, the threshold value for the voltage difference ΔV2 is determined to be lower as the number of power outages increases.

  The voltage difference ΔV2 of the defective secondary battery 10 shown in FIG. 7 is a value equal to or greater than the threshold value. Therefore, in this embodiment, the quality determination of the secondary battery 10 can be accurately performed based on the voltage difference ΔV2 even when there is a pause in the first aging.

  Next, the procedure for determining the quality of the secondary battery 10 in the aging process of this embodiment will be described with reference to the flowchart shown in FIG. In the aging process, first, the secondary battery 10 is charged in order to adjust the SOC expressed by the ratio of the remaining battery capacity of the secondary battery 10 to the battery capacity in the fully charged state to a predetermined SOC (S101). The SOC of the secondary battery 10 after charging can be set to 90%, for example. Further, the voltage V0 of the secondary battery 10 after charging is measured (S102).

  Next, the first aging is performed on the secondary battery 10 (S103), and the voltage V1 after the first aging is measured (S104). Further, the second aging is performed (S105), and the voltage V2 after the second aging is measured (S106). In addition, conditions, such as temperature and time of 1st aging and 2nd aging, can be performed by the conditions currently performed about these.

  Subsequently, by subtracting the voltage V1 measured in step S104 from the voltage V0 measured in step S102, a voltage difference ΔV1 that is a voltage decrease amount of the secondary battery 10 in the first aging is calculated (S107). Further, a threshold for the voltage difference ΔV2 is set from the calculated voltage difference ΔV1 (S108). The threshold value set in step S108 is set to a lower value as the voltage difference ΔV1 is higher.

  Note that the threshold for the voltage difference ΔV2 can be determined in advance by performing an experiment for each voltage difference ΔV1. Thereby, the threshold value can be set based on the voltage difference ΔV1 calculated in step S107. The threshold value for the voltage difference ΔV2 is determined as a reference threshold value at the normal voltage difference ΔV1 when there is no pause in the first aging, and the normal voltage difference ΔV1 and the voltage difference ΔV1 calculated in step S107. It is also possible to calculate by multiplying the reference threshold by a correction coefficient according to the difference. The correction coefficient may be determined based on experiments conducted in advance.

  Next, by subtracting the voltage V2 measured in step S106 from the voltage V1 measured in step S104, a voltage difference ΔV2 that is a voltage decrease amount of the secondary battery 10 in the second aging is calculated (S109). If the calculated voltage difference ΔV2 is less than the threshold value for the voltage difference ΔV2 set in step S108 (S110: YES), the secondary battery 10 is determined as a good product (S111). On the other hand, when the calculated voltage difference ΔV2 is equal to or larger than the threshold value set in step S108 (S110: NO), the secondary battery 10 is determined as a defective product (S112). The secondary battery 10 determined to be defective is excluded from the normal manufacturing process and is not shipped as defective.

  Note that the voltage V0 of the secondary battery 10 before the first aging may be determined according to the charging condition in step S101 without being measured. That is, for example, when the battery voltage of the secondary battery 10 after charging is charged at 4V in step S101, the value of the voltage V0 may be set to 4V. In this case, the threshold for the voltage difference ΔV2 may be set by the voltage V1 without calculating the voltage difference ΔV1. This is because the value of the voltage difference ΔV1 is determined by the value of the voltage V1. The threshold set by the voltage V1 may be set to a lower value as the value of the voltage V1 is lower. That is, even when the threshold value is set by the voltage V1, the threshold value is set to a lower value as the voltage difference ΔV1 is higher.

Moreover, the present inventors confirmed the effect of this invention by performing the following experiment. That is, first, the following materials were used for the positive electrode mixture layer 76 and the negative electrode mixture layer 86, respectively, and secondary batteries A to G having the same configuration as the secondary battery 10 were produced.
Positive electrode mixture layer 76
Positive electrode active material: ternary system (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ )
Conductive aid: Acetylene black (AB)
Binder: Polyvinylidene fluoride (PVDF)
Negative electrode composite material layer 86
Negative electrode active material: Graphite Binder: Styrene butadiene rubber (SBR)
Thickener: Carboxymethylcellulose (CMC)

  In addition, the secondary batteries A to G were all defective secondary batteries having the same internal short-circuit locations. Further, in each of the defective secondary batteries A to G, after the voltage V0 after charging for adjusting the SOC was measured, the first aging was performed under the conditions shown in Table 1 below.

  As shown in Table 1, the secondary battery G was subjected to normal first aging without a pause. For the secondary batteries A, B, and C, the first aging was performed so that the pause time from the time t1 to the time t2 described above with reference to FIG.

  In addition, a single power failure condition for the secondary batteries D, E, and F is that the power failure time is 96 hours, the room temperature is 25 ° C., and the temperature of the secondary battery is changed from the power failure state to the first aging temperature again. The startup time was 10 hours. That is, for the secondary batteries D, E, and F, the suspension time from time t1 to time t2 described above with reference to FIG.

  Subsequently, for the secondary batteries A to G, the voltage V1 after the first aging was measured. Further, the secondary batteries A to G were subjected to the second aging under the same conditions, and then the voltage V2 was measured.

  FIG. 9 shows the relationship between the voltage difference ΔV1 and the voltage difference ΔV2 calculated for the secondary batteries A to G, respectively. From FIG. 9, it is understood that the value of the voltage difference ΔV1 shown on the horizontal axis tends to be higher in the secondary battery having a larger amount of heat given in the first aging. Further, it can be seen that the secondary battery having a larger amount of heat given in the first aging tends to have a lower voltage difference ΔV2 shown on the vertical axis. This is because a secondary battery having a larger amount of heat given in the first aging has a larger amount of self-discharge in the first aging and a lower value of the voltage V1. Furthermore, it can be seen that the value of the voltage difference ΔV2 tends to be lower as the voltage difference ΔV1 is higher.

  In FIG. 9, an example of a threshold value for the voltage difference ΔV that has been conventionally used in the determination of the quality of the secondary battery in the aging process is shown by a one-dot chain line. In addition, the threshold for the voltage difference ΔV2 of the present embodiment is indicated by a solid line.

  The threshold value for the voltage difference ΔV in the conventional example is determined for the secondary battery G that has been subjected to the normal first aging without the pause in the first aging. For this reason, the threshold value for the voltage difference ΔV2 in the conventional example shown by the alternate long and short dash line in FIG. 9 is a constant value regardless of the voltage difference ΔV1.

  The voltage difference ΔV2 between the secondary batteries A, D, and G is higher than the threshold value for the voltage difference ΔV2 in the conventional example. Therefore, it can be seen that the secondary batteries A, D, and G can be selected as defective products in the determination of the quality of the secondary battery using the threshold for the voltage difference ΔV2 in the conventional example.

  However, since the voltage difference ΔV2 between the secondary batteries B, C, E, and F is too lower than the voltage difference ΔV2 of the normal secondary battery G, it shows a value lower than the threshold value for the voltage difference ΔV2 of the conventional example. ing. Therefore, these secondary batteries B, C, E, and F are mistakenly determined to be non-defective products even though they are defective in the determination of the quality of the secondary battery using the threshold value for the voltage difference ΔV2 in the conventional example. It will be judged.

  On the other hand, as shown in FIG. 9, all the voltage differences ΔV2 of the secondary batteries A to G are higher than the threshold value for the voltage difference ΔV2 of the present embodiment indicated by the solid line. Therefore, in the pass / fail judgment using the threshold for the voltage difference ΔV2 of this embodiment, it can be seen that all the secondary batteries A to G can be accurately selected as defective products. This is because the threshold value for the voltage difference ΔV2 in this embodiment is set to be a lower value as the secondary battery has a higher voltage difference ΔV1.

  As described above in detail, in the quality determination in the aging process according to the present embodiment, the voltage difference ΔV2 between the voltage V1 and the voltage V2 that is the amount of decrease in the battery voltage in the second aging is greater than or equal to the threshold for the voltage difference ΔV2. The secondary battery 10 is determined as a defective product. The threshold for the voltage difference ΔV2 is set to a lower value as the voltage difference ΔV1 between the voltage V0 and the voltage V1, which is the amount of decrease in battery voltage in the first aging, is higher. As a result, a method for inspecting a lithium ion secondary battery and a method for manufacturing a lithium ion secondary battery that can accurately select defective lithium ion secondary batteries in the aging process are realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Accordingly, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. That is, the configuration of the lithium ion secondary battery described in the above embodiment is merely an example. For example, a lithium ion secondary battery having a cylindrical battery case, a positive electrode plate, a negative electrode plate, and a separator are stacked in a stacked manner. The present invention can also be applied to a lithium ion secondary battery having an electrode body. Further, in the manufacturing process of the lithium ion secondary battery, in addition to the pass / fail judgment in the aging process, other inspections may be performed. In that case, a final good quality lithium ion secondary battery to be shipped may be selected from a group of lithium ion secondary batteries determined as good in the quality determination in the aging process.

DESCRIPTION OF SYMBOLS 10 Secondary battery 20 Electrode body 30 Electrolytic solution 40 Battery case 50 Positive electrode terminal 60 Negative electrode terminal 70 Positive electrode plate 80 Negative electrode plate 90 Separator

Claims (2)

About aging treatment by leaving a lithium ion secondary battery under predetermined conditions,
Perform the first aging,
The battery voltage is measured after the first aging, and the measured value is defined as the first battery voltage.
Performing a second aging after measuring the first battery voltage;
The battery voltage is measured after the second aging, and the measured value is set as the second battery voltage.
In a method for inspecting a lithium ion secondary battery in which a lithium ion secondary battery in which a voltage difference between the first battery voltage and the second battery voltage is equal to or greater than a predetermined voltage difference threshold is determined to be defective. ,
The battery voltage before the first aging is a reference voltage,
The inspection method for a lithium ion secondary battery, wherein a lower value is used as the voltage difference threshold value as the voltage difference between the reference voltage and the first battery voltage is higher. In a method of manufacturing a lithium ion secondary battery, an electrode body formed by laminating positive and negative electrode plates by winding or flat stacking with a separator sandwiched therebetween and an electrolyte solution are enclosed in a battery container. ,
After enclosing the electrode body and the electrolyte in the battery container,
An inspection method for a lithium ion secondary battery according to claim 1 is performed,
A method for producing a lithium ion secondary battery, characterized in that a lithium ion secondary battery determined to be defective is excluded.

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