KR101769182B1 - Method for detecting a secondary battery whose electrolyte is defectively impregnated - Google Patents

Abstract

The present invention relates to a method for detecting failure of electrolyte impregnation of a secondary battery using charge amount measurement.
A method for detecting impurities in an electrolyte solution of a secondary battery according to the present invention includes the steps of injecting and impregnating an electrolyte into a bare cell, a first full charge step of applying power to the impregnated bare cell to fully charge the charged bare cell, And a determining step of determining the bare cell as a faulty impregnated cell when the charged amount by the first charged amount measuring step is less than the minimum value of the reference charging range.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for detecting impregnation failure of an electrolyte in a secondary battery,

TECHNICAL FIELD The present invention relates to a method of detecting failure of electrolyte impregnation of a secondary battery, and more particularly, to a method of detecting failure of electrolyte impregnation of a secondary battery using charge amount measurement.

Recently, interest in energy storage technology is increasing. Among them, the development of a secondary battery which can be easily charged and discharged has become a focus of attention. Among the secondary batteries currently in widespread use, the lithium ion battery has an advantage in that the operating voltage is higher and the energy density is much higher than that of a conventional secondary battery such as a Ni-MH, Ni-Cd or sulfuric acid-lead battery using an aqueous electrolyte It is getting popular in various fields.

A general lithium ion battery is assembled by inserting porous positive electrodes and negative electrodes and a separator alternately with each other, inserting them into a case of a shape of a certain size and shape, a pouch, etc., and then injecting an electrolyte . At this time, the electrolyte injected later is impregnated between the positive electrode, the negative electrode and the separator by a capillary force, which is referred to as impregnation, or wetting.

On the other hand, in the production process of the secondary battery, there exists a step of selecting defects that may occur in each process. When the impregnation is delayed, the defective performance is not only a structural defect but a delay in time, There is a possibility of being selected as defective in the selection step. Particularly, since the secondary cell (the bare cell of the secondary cell) which is selected as the defective cell is discarded, there is a problem that effort and cost for assembling the bare cell are lost.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in view of the above circumstances, and provides a method of preventing a battery cell from delaying the impregnation of a battery after the cell is fully charged.

It is to be understood that the present invention is not limited to the above-mentioned technical problems and other technical objects which are not mentioned can be clearly understood by those skilled in the art from the following description It will be possible.

A method of detecting failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention includes a step of injecting and impregnating an electrolyte into a bare cell, a first full charge step of supplying power to the impregnated bare cell, A first charging amount measuring step of measuring a charged amount of the bare cell; and a determining step of determining the bare cell as a faulty impregnated cell when the charged amount by the first charged amount measuring step is less than the minimum value of the reference charging range.

The method for detecting the electrolyte impregnation failure of the secondary battery according to another embodiment of the present invention may include a storing step of storing the bare cell for a predetermined period after the first charged amount measuring step, The method may further include an open-circuit voltage measuring step of measuring an open-circuit voltage of the bare cell, and the determining step determines that the bare cell is a faulty impregnated cell if the measured open- .

The method for detecting the electrolyte impregnation failure of the secondary battery according to still another embodiment of the present invention may further include a second full charge step of applying the power to the bare cell and performing full charge after the open- And a second charge amount measuring step of measuring a charge amount of the bare cell when the amount of charge by the second charge amount measuring step exceeds a predetermined charge amount, .

The method for detecting the electrolyte impregnation failure of the secondary battery according to various embodiments of the present invention may further include a step of treating the bare cell determined to be the impregnating defective cell as a good cell in the determining step .

Further, in the method for detecting failure of electrolyte impregnation in a secondary battery according to various embodiments of the present invention, the determining step may include determining whether the charged amount by the first charged amount measuring step is within the reference charging range, And if the open-circuit voltage is lower than a predetermined voltage drop, the cell is determined to be a low-voltage defective cell.

Further, in the method for detecting failure of electrolyte impregnation in a secondary battery according to various embodiments of the present invention, the determining step may include determining whether the charged amount by the first charged amount measuring step is within the reference charging range, And if the open-circuit voltage is higher than a predetermined voltage drop, and the charge amount by the second charge-amount measurement process exceeds a predetermined charge amount, the bare cell is determined to be a low-voltage defective cell.

According to various embodiments of the present invention, when the measured charge amount is less than the minimum value of the reference charge range, the bare cell can be determined as a faulty impregnated cell. Therefore, the impregnated faulty cell is mistaken for a capacity- . ≪ / RTI > As a result, it is possible to prevent the effort and cost involved in assembling the bare cell from being lost, and to improve the productivity of the bare cell of the secondary cell.

FIG. 1 conceptually illustrates the effect of the electrolyte impregnation delay on the charge amount and voltage of the secondary cell bare cell.
FIG. 2 shows a method of detecting failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention.
FIG. 3 shows a distribution of the charged amount of a bare cell obtained by performing a method of detecting a failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention.
4 illustrates a method of detecting failure of electrolyte impregnation in a secondary battery according to another embodiment of the present invention.
FIG. 5 illustrates a method of detecting failure of electrolyte impregnation in a secondary battery according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, defects that may occur in the manufacturing process of the bare cell of the secondary battery including impregnation delay (defective) will be described.

FIG. 1 conceptually illustrates the effect of the electrolyte impregnation delay on the charge amount and voltage of the secondary cell bare cell.

The bare cell of a secondary battery to which the present invention can be applied may include an electrode assembly and a case for accommodating the electrode assembly. The case may have a pouch or can shape, and the electrode assembly may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The positive electrode and the negative electrode may include a positive electrode active material and a negative electrode active material, respectively.

On the other hand, the impregnation or wetting of the electrolyte in the secondary battery indicates that the non-aqueous liquid electrolyte permeates between the positive electrode, the negative electrode and the separator by the capillary force. Specifically, it means that the electrolyte penetrates into the electrode active material on the surface of the electrode.

However, the positive electrode, the negative electrode (particularly, the positive electrode and the negative electrode active material) and the separator are all hydrophobic substances, while the electrolytic solution is a hydrophilic material, so that impregnation of the electrolyte solution is often not performed rapidly Delay or poor impregnation). In particular, if the impregnation property of the electrolyte is decreased due to the impregnation delay or the like, the electrolyte solution does not reach the active material particles of the electrode, so that the lithium ion migration is not smooth and the performance of the normal secondary battery is delayed.

For example, referring to FIG. 1 (A), the secondary battery 100 in which the impregnation is delayed can be divided into the activated part (a) impregnated with the electrolyte and the inactivated part (b) after the impregnation is delayed. At this time, the height of the secondary battery 100 conceptually represents the voltage (V), the charging amount (mAh) as the base, and the electric energy (J) as the volume.

When the secondary battery 100 is subjected to the charging process, the secondary battery 100 can be charged up to 4.2V, which is a preset voltage, to store the electric energy, which can be represented by the activated part (a). On the other hand, the portion (b) inactivated due to the delay of impregnation can not be activated and can not store electric energy.

However, if the impregnation of the electrolyte proceeds with time and the impregnation is completed as shown in FIG. 1 (B), the inactivated portion (b) of the secondary battery 100 may disappear. However, since the energy stored in the secondary battery 100 is the same as the energy stored in FIG. 1 (A) (the natural energy loss during the impregnation process is not considered), the voltage drops and the deactivated (Part (c)) is almost equal to the energy of the part (b).

That is, when the impregnation is delayed, a space (activated portion (a)) for storing the charged electric energy is not sufficiently formed, and a voltage drop may occur when the impregnation is completed after the charging process. That is, if the impregnation is delayed, the performance of the secondary battery is deteriorated. On the other hand, in the case of the portion (c), the electric energy can be stored again if the charging process is performed again later. This is distinguished from the capacity failure described later.

As described above, since the impregnation delay hinders the performance of the secondary battery, the impregnation process generally has a severe process condition for increasing the impregnation speed, such as maintaining the pressure at the impregnation point high or setting the specific temperature . Accordingly, when the difficult process conditions are not satisfied, impregnation failure may occur in a large amount.

On the other hand, there is a so-called capacity defect as a deficiency compared with the impregnation delay (defective). The defective capacity occurs mainly when the amount of application of various materials, materials, and the applied amount in the bare cell of the secondary battery is more or less than that in the normal case. For example, in the case where an electrode active material is insufficiently applied to an electrode, an electrolyte is injected into a bare cell in a small amount, and the area of the bare cell is reduced by excessive cutting during electrode cutting, And the case of covering a large area.

Such a capacity defect can usually be detected for each bare cell (or electrode assembly) in each process. For example, when an electrode active material is insufficiently applied to an electrode, a weight can be measured or a defect can be detected using a vision. If the electrolyte injection amount is insufficient, the weight can be measured and a defective cell can be removed.

Such a capacity defect can occur in each process for each bare cell, and it is difficult to generate a large quantity at a time, the probability of occurrence of a capacity defect is usually within 1%, the error of a charge amount or a voltage due to a capacity defect is also insignificant , It is distinguished from impregnation delay (or failure).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of detecting failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a method of detecting failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention.

Referring to FIG. 2, a method of detecting failure of electrolyte impregnation in a secondary battery according to an embodiment of the present invention includes a step of impregnating and impregnating an electrolyte into a bare cell (step S201) (Step S202) for measuring the amount of charge applied to the bare cell by the power source (step S203), and a first charge amount measurement step (step S203) for measuring the charge amount by the first charge amount measurement step And judging the bare cell to be a faulty impregnated cell if the measured bare cell is less than the minimum value of the reference charging range (step S204).

In step S201, the electrolytic solution can be injected into the bare cell and impregnated. In the bare cell, the electrolytic solution spreads by the capillary phenomenon to activate the bare cell.

In step S202, power can be applied to the impregnated bare cell to charge the battery. As a method of filling the impregnated bare cell, for example, there is a method of continuously performing a constant current (CC) section and a constant voltage (CV) section during charging. The secondary battery is charged with electrical energy by constantly applying current in the CC section. In the CC section, the voltage of the secondary battery rises as the charging progresses. When the voltage of the secondary battery reaches a predetermined voltage value (for example, 4.2V), the operation proceeds to the CV section to continue charging. In the CV section, charging is performed while maintaining the preset voltage value (4.2 V). In such a CV section, the current is constantly decreased while maintaining the voltage value (4.2 V), and when the current value reaches a predetermined value (for example, 100 mA obtained by multiplying 2000 by 1/20 in the case of the battery having a capacity of 2000 mAh) And can stop charging.

In step S203, the charged amount applied to the bare cell can be measured. As a method of measuring the charged amount Q, for example, there is a method of integrating the current (i) applied by the power source in step S202 according to the time (t) as shown in equation (1).

In step S204, if the charged amount measured in step S203 is less than the minimum value of the reference charging range, the bare cell can be determined as a faulty impregnated cell. Contrary. If the charged amount determined in step S204 is within the reference charging range or exceeds the maximum value of the reference charging range, the normal secondary battery manufacturing process can be continuously performed. For example, when the reference charging capacity is 2200 mAh and the reference charging range is 2200 +/- 20 mAh, the bare cell of less than 2180 mAh can be judged as a faulty impregnated cell.

On the other hand, according to the embodiment, following the step S204, a step of treating the bare cell judged as a faulty impregnated cell as a good cell may be further carried out. That is, even if the bare cell is determined to be a faulty impregnated cell, it can function as a normal bare cell by performing the subsequent manufacturing process without discarding it.

This is possible because the impregnation delay (or failure) is not due to structural defects of the secondary cell bare cell but because the impregnation speed is due to the nature of the material. In other words, the impregnation of the electrolytic solution can be completed after a predetermined time, and it can function as a normal bare cell by another full charge process according to a conventional secondary cell manufacturing process.

3 shows a distribution of the charged amount of the bare cell (for example, the distribution of the charged amount for each bare cell measured in step S203) obtained by performing the method of detecting the electrolyte impregnation failure of the secondary battery according to the embodiment of the present invention .

Referring to FIG. 3, box and whisker plots indicate that the charged amount of the secondary battery bare cell manufactured by production date is normalized. Each of the boxes can be composed of about 30000 ~ 100000 (200000 in many cases) bare cells manufactured by day. On the other hand, in the bare cell of Fig. 3, for example, the reference charging capacity is 2200 mAh and the reference charging range is 2200 +/- 20 mAh.

For example, in the leftmost box (a) of FIG. 3, 2199.00 mAh is the median, 2194.00 mAh is the first quartile (1Q), 2204.00 mAh is the third quartile (3Q), 2219.00 mAh Maximum value, and 2179.00 mAh represents the minimum value. The range indicated by box between the first quartile (1Q) and the third quartile (3Q) based on the median represents the range of the charged amount stored by the bare cells of 50% of the bare cells produced on the production date . The maximum value and the minimum value represent a maximum value and a minimum value of the charged amount of the bare cell manufactured on the production date.

Referring to FIG. 3, in the box diagrams (a) and most of the boxes, boxes indicating the charged amount of the bare cells of 50% between the first quartile (1Q) and the third quartile (3Q) 20 mAh. ≪ / RTI > However, the box (2161.00mA ~ 2172.00mA) showing the charge amount of 50% of the bare cells in the second box picture (b) on the right side has a charge amount lower than the lower limit (2180mAh) Almost all tens of thousands of bare cells are charged at less than the reference charge (2200 mAh). Therefore, it can be seen that an abnormality occurred in the manufacturing process on the day when the bare cells of the box figure (b) were produced.

However, in a case where a general mass production system for a secondary battery is provided, it is considered that the generation rate of capacity defects in each process is usually 1% or less, and that defective cells are selected and steps are provided for each process , It is difficult to consider all of the bare cells of the box (b), which is measured to have a large amount of charge, to be defective.

In addition, in the case of a low-voltage defective cell which is one of the capacity defects, the discharge is continuously generated even during the first full-charge process by the step S202 of FIG. When referring to the box of FIG. 1, a bare cell in which an undervoltage failure occurs does not have a portion (b) delayed impregnation but a hole exists in the box. That is, since the battery needs to supply as much of the leaking electrical energy as possible for full charge, the charging amount is necessarily larger than that of the impregnated defective cell and the defective bare cell. Therefore, it is difficult to see the bare cells of the box figure (b) as under-voltage defects.

Therefore, under the mass production process, impregnation delay (defective) can occur in a large amount if the process conditions for performing the electrolyte solution impregnation process are not met for some reason, the process conditions of the impregnation process such as pressure are very difficult, (B) can not be charged as much as the amount of the deactivated portion (b) when the impregnation delay occurs as shown in Fig. 1 (A) it can be judged that tens of thousands of bare cells of (b) are impregnated defective cells due to impregnation defects.

According to the method for detecting the electrolyte impregnation failure of the secondary battery according to the embodiment of the present invention, when the measured charged amount is less than the minimum value of the reference charging range, the bare cell can be determined as a faulty impregnated cell, It is possible to switch to a normal bare cell after completing the impregnation without separately obliterating it as a defective cell. As a result, it is possible to prevent the effort and cost involved in assembling the bare cell from being lost, and to improve the productivity of the bare cell of the secondary cell.

4 illustrates a method of detecting failure of electrolyte impregnation in a secondary battery according to another embodiment of the present invention.

Referring to FIG. 4, a method of detecting impregnation failure of an electrolyte in a secondary battery according to another embodiment of the present invention includes a step of impregnating an electrolyte into a bare cell and impregnating the bare cell (step S401) (Step S402) for measuring the amount of charge applied to the bare cell by the power source (step S403), storing the bare cell for storage for a preset period of time (Step S404), and an open-circuit voltage measuring step (step S405) of measuring an open-circuit voltage of the bare cell over a predetermined period of time, and a step of measuring an open- If the open-circuit voltage is higher than the predetermined voltage drop, the determining step may determine that the bare cell is a faulty impregnated cell (step S406).

Steps S401 to S403 are substantially the same as steps S201 to S203 in Fig. 2, respectively, and therefore, a detailed description thereof will be omitted.

In step S404, the fully charged bare cell is stored for a preset period of time by steps S401 to S403. More specifically, the bare cell charged in step S401 to step S403 is stored at room temperature for 3 to 5 days, so that a voltage drop occurs naturally.

In step S405, the open-circuit voltage of the bare cell is measured after the predetermined period has elapsed. As a result, it is possible to confirm the open-circuit voltage which is natural.

If it is determined in step S406 that the charge amount measured in step S403 is less than the minimum value of the reference charge range and the open-circuit voltage measured in step S405 is greater than the preset voltage drop amount, the bare cell may be determined as a faulty impregnated cell. For example, when the reference charge capacity is 2200 mAh, the reference charge range is 2200 +/- 20 mAh, and the predetermined voltage drop amount is 60 mV, the charge amount measured in step S403 is 2166 mAh, and in step S404, If the open-circuit voltage has dropped from 4.2 V to 4.12 V in step S405, the bare cell may be determined as a faulty impregnated cell

On the other hand, the fact that the measured open-circuit voltage is higher than the predetermined voltage drop can be understood as a result of statistical analysis of the voltage drop of many bare cells and dropping out of a predetermined range on the normal distribution.

The reason why the determination is the same as in the step S406 is that, in the case of the impregnation failure cell, the impregnation is completed when the impregnation failure cell is stored for a preset period of time, And a voltage drop occurs (see Fig. 1 (B)). However, even in the low voltage defective cell which is one of the capacity fault cells, the voltage drop due to the self discharge is added in addition to the natural voltage drop during the predetermined period of time in step S404. However, the voltage drop of the defective cell is about the same as or slightly larger than the voltage drop of the good cell, and the size is generally smaller than the voltage drop of the defective cell.

On the other hand, according to the embodiment, a step of treating the bare cell determined to be a faulty impregnated cell as a good cell may be further performed following the step S406, as in the embodiment. That is, even if the bare cell is determined to be a faulty impregnated cell, it can function as a normal bare cell by performing the subsequent manufacturing process without discarding it.

Further, in another embodiment, the determining step of step S406 may be such that the charging amount by the first charging amount measuring step of step S403 is within the reference charging range or is not less than the maximum value of the reference charging range, Is determined to be lower than the predetermined voltage drop amount, the bare cell may be determined to be a low voltage defective cell.

In the case of the above embodiment, the impurity defect cell can be distinguished from the impurity defect cell in that the first charge amount measurement value of the low voltage fault cell is higher than the impregnation failure cell and the voltage drop amount measured in step S405 is smaller than that of the impregnation failure cell. Thus, even if the low-voltage defective cell is not detected as defective in each manufacturing process of the secondary cell bare cell, for example, the low-defective cell and the defective-defective cell can be selected and treated differently.

According to the method for detecting the electrolyte impregnation failure of the secondary battery according to another embodiment of the present invention, in addition to the advantages of the method according to the embodiment, the voltage drop of the impregnated defective cell can be more accurately detected, It is possible to detect the cell, thereby further improving the productivity of the bare cell of the secondary battery.

FIG. 5 illustrates a method of detecting failure of electrolyte impregnation in a secondary battery according to another embodiment of the present invention.

Referring to FIG. 5, a method of detecting failure in electrolyte impregnation of a secondary battery according to another embodiment of the present invention includes a step of impregnating and impregnating an electrolyte into a bare cell (step S501) (Step S502) for measuring the amount of charge applied to the bare cell by the power source (step S503), storing the bare cell for a preset period of time (Step S504), and an open-circuit voltage measuring step (step S505) for measuring an open-circuit voltage of the bare cell over a predetermined period of time, a second full-charge step (Step S506), and a second charge level measurement step (step S507) for measuring the charge level applied to the bare cell by the power source, and the second charge level measurement step (Step S508), and if the open-circuit voltage is lower than the predetermined voltage drop, and the charge amount by the second charge-amount measurement process exceeds a predetermined charge amount, . ≪ / RTI >

Steps S501 to S505 are substantially the same as the steps S401 to S205 in Fig. 4, respectively, and thus a detailed description thereof will be omitted.

In step S506, the bare cell can be fully charged with a predetermined voltage (for example, 4.2 V) by applying power to the bare cell (second full charge step). By this process, the bare cell is compensated for the amount of charge lost during the predetermined period of step S504.

In step S507, the amount of charge applied to the bare cell by the power source can be measured, for example, in the same manner as in step S203 of FIG. 2 (second charging amount measuring step).

In step S508, it is determined in step S502 that the charged amount by the first charged amount measuring step is less than the minimum value of the reference charging range, the open-circuit voltage measured in step S505 is stronger than the predetermined voltage drop amount, When the charged amount exceeds the predetermined charged amount, the bare cell can be determined as a faulty impregnated cell. At this time, the predetermined charging amount refers to the amount of charge required to fully charge the bare cell from the charging amount at a predetermined time period according to the predetermined period of time in the step S504. In the case of the good cell, The charged amount becomes the lost amount.

If the impregnation failure cell is stored for a preset period of time at step S504 and the impregnation is completed, a void portion as shown in part (c) of FIG. 1 (B) occurs. In step S506, the bare cell is charged with electrical energy from the power source. As a result, the charged amount in the second full-blown step of the impregnated defective cell is such that the filling amount for the recovered portion (for example, the portion (b) in FIG. 1 (A)) is added to the naturally- So that the value of the good cell is larger than that of the second full-blown process. This supports the judgment of step S508 together with the part related to the charge amount of one embodiment and the part related to the voltage drop of the other embodiment.

However, the charged amount by the second full-charge step of the low-voltage faulty cell is added to the amount of charge lost by the self discharge in addition to the amount of charge that naturally disappears during the predetermined period of time in step S504. However, the charging amount of the low-voltage defective cell by the second full-blown step is equal to or slightly larger than the charging amount by the second full-blown step of the good cell and is smaller than the charging amount by the second full- Less common.

On the other hand, according to the embodiment, similarly to the first and second embodiments, the step S508 may be followed by the step S509 to further treat the bare cell judged as the impregnating fault cell as a good cell. Particularly, in the case of another embodiment, impregnation is completed, the entire portion of the bare cell is activated, and the amount of the charged bare cell is almost the same as that of the good cell, so that the following conventional manufacturing process can be performed.

If it is determined in step S508 that the charged amount by the first charged amount measuring step in step S503 is within the reference charging range or is not less than the maximum value of the reference charging range, It is possible to determine the bare cell as a capacity-defective cell when the amount of charge due to the second charging-amount measuring step in step S507 exceeds the predetermined charging amount.

In the case of the above embodiment, the first charge amount measurement value of the low voltage faulty cell is higher than that of the impregnated failure cell, the voltage drop amount measured in step S505 is less than that of the impregnated failure cell, the second charge amount measurement value of step S507 is the impregnation failure It can be distinguished from the impregnated cell at a point less than that of the cell. Thus, even if the low-voltage defective cell is not detected as defective in each manufacturing process of the secondary cell bare cell, for example, the low-defective cell and the defective-defective cell can be selected and treated differently.

According to the method for detecting the electrolyte impregnation failure of the secondary battery according to still another embodiment of the present invention, in addition to the advantages of the method according to the first embodiment and the second embodiment, the charging amount of the second full- It is possible to detect the impregnated and defective cell with higher accuracy using the larger one, so that the productivity of the bare cell of the secondary battery can be further improved.

The embodiments described herein are not intended to limit the scope of the invention in any way. Also, unless explicitly mentioned, such as " essential ", " importantly ", etc., it may not be a necessary component for application of the present invention.

The use of the terms " above " and similar indication words in the specification of the present invention (particularly in the claims) may refer to both singular and plural. In addition, in the present invention, when a range is described, it includes the invention to which the individual values belonging to the above range are applied (unless there is contradiction thereto), and each individual value constituting the above range is described in the detailed description of the invention The same. Finally, the steps may be performed in any suitable order, unless explicitly stated or contrary to the description of the steps constituting the method according to the invention. The present invention is not necessarily limited to the order of description of the above steps. The use of all examples or exemplary language (e.g., etc.) in this invention is for the purpose of describing the present invention only in detail and is not to be limited by the scope of the claims, It is not. It will also be appreciated by those skilled in the art that various modifications, combinations, and alterations may be made depending on design criteria and factors within the scope of the appended claims or equivalents thereof.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. The present invention is not limited to the drawings.

Claims (6)

A first full charge step of applying power to a plurality of bare cells impregnated in the electrolyte solution to perform first full charge;
A first charge amount measurement step of measuring a charge amount of the bare cells;
A second full charge state in which bare cells whose charge amount by the first charge amount measurement step is smaller than the minimum value of the reference charge range are selected and the selected bare cells are charged again after a predetermined period has elapsed, Whole process; And
And judging whether or not the charged amount of the secondary full charge display exceeds a preset charging amount. The method according to claim 1,
Further comprising an open-circuit voltage measuring step of measuring an open-circuit voltage of the selected bare cell before the second full charge when the predetermined period has elapsed. delete delete The method of claim 2,
If the charge amount by the first charge amount measurement step is within the reference charge range or is greater than or equal to a maximum value of the reference charge range and the open-circuit voltage is lower than the predetermined voltage drop amount, the bare cell is determined to be a low- Wherein the secondary battery is a lithium secondary battery. The method of claim 2,
Wherein the charging amount by the first charging amount measuring step is within the reference charging range or is greater than or equal to a maximum value of the reference charging range and the open circuit voltage is higher than the predetermined voltage drop amount, And determining that the bare cell is a low voltage defective cell when the charged amount is exceeded.

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