KR101952565B1 - Method for testing performance of cell - Google Patents

Abstract

The present invention relates to a method for measuring the performance of a cell. The present invention relates to a method for controlling a charge / discharge sub-cycle in which a normal charge / discharge sub-cycle for charging and discharging under normal conditions and an acceleration charge / discharge sub-cycle for charging and discharging under acceleration conditions are one main- A process; And a second step of evaluating the cycle life of the cell in which the first process is performed. According to the present invention, it is possible to accurately measure the cycle life of a cell, for example, the cycle life of a cell such as a hybrid capacitor in a short time.

Description

{METHOD FOR TESTING PERFORMANCE OF CELL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring the performance of a cell, and more particularly to a method of measuring a performance of a cell capable of accurately evaluating a cycle life of a cell such as a hybrid capacitor, .

Generally, the performance of a cell such as a battery or a transistor is measured after completion of development or manufacture. For example, performance such as electrical characteristics or cycle life is measured. In particular, electrochemical devices as energy storage devices, such as secondary batteries such as capacitors and lithium ion (Li ⁺ ) batteries, are used to develop new products or to control the quality of existing products. It is necessary to measure the satisfaction.

The performance of the cell is evaluated by evaluating the electrical characteristics such as operating voltage, current, and capacity, and it is also important to select the cell by performance (grade), but it is very important for the reliability with the consumer. If the cell does not meet the required characteristics or the cycle life is short, it may damage the related electric / electronic product. As a result, most of the cells are measured for performance such as electrical characteristics and cycle life as a part of reliability before being commercialized.

For example, an electrochemical device such as a capacitor may be electrically and thermally operated such as Self-Discharge (SD), Leakage Current (LC), Equivalent Series Resistance (ESR) Properties are measured. The measurement of such electrical characteristics is mainly performed by a related measuring instrument.

In addition, the cycle life is evaluated (predicted) by reducing the capacity of the cell due to repeated charge and discharge. For example, in the case of a capacitor or a lithium ion battery, a criterion is required such that after repeated charging and discharging several times, it should be 80% or more of the initial capacity. These standards may be required differently depending on the manufacturer's own standards or customer's standards.

Conventionally, the cycle life of a cell is measured (predicted) by repeatedly performing charging and discharging in an actual use environment condition (normal condition) and then evaluating the remaining capacity in most cases. However, in this case, it takes a long time to measure the life of the cell.

Therefore, in order to shorten the life evaluation time, a method of repeatedly conducting charge and discharge in a severe condition (acceleration condition) than the actual use environment condition (normal condition) of the cell has been attempted. For example, Korean Patent No. 10-0903489, Korean Patent Laid-open No. 10-2013-0073802, and Japanese Patent Laid-Open No. 2009-281916 disclose techniques related to this.

However, conventional measurement methods including the aforementioned patent documents are not accurate or take a long time. For example, when the charging and discharging are continuously repeated under the acceleration condition, deterioration of the cell is serious and has abnormal characteristics. Further, in the case of a capacitor having a long life characteristic, for example, a hybrid capacitor having a life of about 500,000 cycles or an electric double layer capacitor (EDLC) having a life of about 1 million cycles, it takes a long time. In addition, the methods disclosed in the above prior art documents are limited to the measurement of cycle life.

Korean Patent No. 10-0903489 Korean Patent Publication No. 10-2013-0073802 Japanese Patent Application Laid-Open No. 2009-281916

Accordingly, it is an object of the present invention to provide a cell performance measurement method capable of accurately measuring a cycle life or the like for a cell such as a hybrid capacitor in a short time.

It is another object of the present invention to provide a cell performance measurement method capable of measuring electrical performance such as leakage current, resistance and / or capacity in the process of measuring cycle life.

According to an aspect of the present invention,

A first step of repeating the main-cycle by forming a normal charge / discharge sub-cycle for charging and discharging under normal conditions and an acceleration charge / discharge sub-cycle for charging and discharging under acceleration conditions as one main-cycle;

And a second step of evaluating the cycle life of the cell in which the first process is performed.

At this time, the normal charge / discharge sub-

A normal charging step of charging a constant voltage (CV) after being charged with a constant current (CC); And

And a constant discharge step of discharging the constant current (CC).

Also, the acceleration charge / discharge sub-

An accelerating charging step of charging a constant current (CC) and then charging a constant voltage (CV); And

And discharging a constant current (CC).

In addition, according to an exemplary embodiment, the main-cycle comprises: a first idle period following a normal charge / discharge sub-cycle; And a second rest period that proceeds after the accelerating charge / discharge sub-cycle.

In addition, the first step may be performed after the main-cycle is repeated several times. The first step may further include a normal charge / discharge stability-cycle for charging / discharging under normal conditions. In addition, the normal charge / - a complete discharge cycle for discharging the cell, which proceeds after the cycle has progressed.

Further, in the second step,

A first step of measuring an initial capacity of the cell;

A second step of measuring a holding capacity after repeating the first step; And

And a third step of comparing the initial capacity with the storage capacity to determine the cycle life of the cell.

According to the present invention, it is possible to accurately measure the cycle life of a cell, for example, the cycle life of a cell such as a hybrid capacitor in a short time. In addition, electrical characteristics such as leakage current, resistance and / or capacity can be measured in the process of measuring the cycle life.

1 is a conceptual diagram for explaining a first step of a measurement method according to an exemplary embodiment of the present invention.
FIG. 2 and FIG. 3 are graphs illustrating voltage characteristics with time of a cell for explaining a measurement method according to an exemplary embodiment of the present invention.
Figure 4 shows an overall flow diagram of a measurement method according to an exemplary aspect of the present invention.

Hereinafter, the present invention will be described in detail.

A method for measuring the performance of a cell according to the present invention (hereinafter referred to as a "measurement method") includes a normal charge / discharge sub-cycle for charging and discharging under normal conditions, Repeating the main-cycle with the acceleration charge / discharge sub-cycle as one main-cycle; And a second step of evaluating the cycle life of the cell.

Specifically, in the first step, the charging / discharging under the normal condition and the charging / discharging under the acceleration condition are set as one cycle, and this is repeated N times. In the second step, at least the cycle life of the cell in which the first step is performed is evaluated.

In the present invention, terms such as "sub", "main", "first", and "second" are used to distinguish only one component from another, And the like.

In the present invention, the terms used are as follows unless otherwise specified.

- Category temperature range: The ambient temperature range (minimum operating temperature to maximum operating temperature) designed for continuous operation of the cell.

- rated temperature: the maximum value of the ambient temperature at which the rated voltage (V _R or U _R ) can be applied continuously

- Rated voltage (V _R or U _R ): The maximum value of the direct current (DC) voltage that can be continuously applied to the cell at any temperature between the minimum operating temperature and the rated temperature or the peak value of the pulse voltage

- Rated current (I _R ): DC current at rated voltage (V _R )

- Rated capacitance (C _R ): The actual capacitance of the cell

- constant current (CC): constant current

- constant voltage (CV): constant voltage

In the present invention, the terms "normal condition" and "acceleration condition" are not particularly limited, and they may vary depending on the type of cell and the like. The normal conditions are the same as usual. That is, the normal condition is the actual use condition of the cell. The normal conditions may be selected, for example, from temperature, current, and / or voltage. In the present invention, a normal condition may be an actual use standard of each cell unless otherwise specified. For example, the temperature may be the operating temperature range defined above, and the current and voltage may be the rated current I _R and the rated voltage V _R or U _{R defined} above. The acceleration condition is more severe than the normal condition (the actual use environment condition of the cell). Even in the case of the acceleration condition, it can be selected from the temperature, the current and / or the voltage, and they are more severe than the normal condition so long as the cell can be deteriorated. In the present invention, " charge / discharge " means " charge and discharge ".

In the present invention, a cell to be measured is not particularly limited and may be any type as long as charge / discharge is possible. The cell may be selected from an electrochemical device or the like as an energy storage device. The cell may be, for example, a general secondary battery such as a lithium ion (Li ⁺ ) battery, a lithium polymer battery, a nickel-hydrogen (Ni-H) battery, a lead acid battery and an electrolytic capacitor; General capacitors such as ceramic capacitors, Al electrolytic capacitors, and Ta capacitors; And super capacitors such as electric double layer capacitors (EDLC), pseudo capacitors and hybrid capacitors, and the like. In addition, the shape, size and the like of the cell are not limited. The shape of the cell includes, for example, a square shape, a cylindrical shape, a coin shape, a pouch shape, and the like.

In the present invention, the cell to be measured may be selected from a concrete example, for example, a supercapacitor, more specifically, for example, a hybrid capacitor. The hybrid capacitor includes a positive electrode and a negative electrode. The hybrid capacitor includes, for example, a positive electrode type hybrid capacitor using a metal oxide material for the positive electrode and an activated carbon for the negative electrode, and a negative electrode type hybrid capacitor using metal oxide for the negative electrode and activated carbon for the positive electrode . The metal oxide as the electrode material may be one selected from the group consisting of lithium (Li), titanium (Ti), ruthenium (Ru), manganese (Mn), tantalum (Ta), aluminum Or more of the metal element.

Further, the performance of the cell measured according to the present invention includes at least the cycle life characteristics. The performance of the cell measured according to the present invention optionally includes the electrical characteristics of the cell and the like. That is, the present invention can evaluate (predict) at least the cycle life characteristic of the cell, and can further evaluate the electrical characteristics and the like. The electrical characteristics may vary depending on the type of the cell, and may be one or more selected from, for example, leakage current, resistance, capacity, and the like. At this time, the resistor is selected from a DC resistance and / or an AC resistance, and may be selected from a more specific example, a DC equivalent series resistance (DC, ESR), or the like.

Hereinafter, exemplary embodiments of the present invention will be described. Fig. 1 is a conceptual diagram of a first step for explaining the present invention. The first step is a step of repeating the main-cycle (M-C) several times as described above.

Referring to FIG. 1, the measurement method according to the present invention includes a normal charge / discharge sub-cycle S-C1 and an acceleration charge / discharge sub-cycle S-C2 as one main-cycle M-C. And the main-cycle (M-C) is repeated several times. More specifically, the first step is a first step of charging / discharging under normal conditions according to the present invention; And a second step of charging / discharging under acceleration conditions after the first step is performed, wherein the first step and the second step are one 'deterioration cycle process', and the deterioration cycle process is repeated several times.

The number of times of the main-cycle (M-C) is not limited. Referring to FIG. 1, the number of times of the main-cycle (M-C) is N times, where N is an integer of 1 or more, and the upper limit value is not limited. The number of times N of the main-cycle (M-C) may vary depending on the type of the cell and / or the acceleration condition.

Also, the main-cycle M-C includes at least one normal charge / discharge sub-cycle S-C1 and at least one acceleration charge / discharge sub-cycle S-C2. That is, the number of times of each sub-cycle (S-C1) (S-C2) in one main-cycle (M-C) is not limited. 1, in a main-cycle MC, the normal charge / discharge sub-cycle S-C1 may be n times and the acceleration charge / discharge sub-cycle S- Can be m times. And n and m are an integer of 1 or more.

Further, according to an exemplary embodiment of the present invention, the number of times n of the normal charge / discharge sub-cycle (S-C1) and the number m of acceleration charge / discharge sub- 100: 1 to 100: 1. That is, n / m = 0.01-100. More specifically, for example, in any one main-cycle MC, the number n of normal charge / discharge sub-cycles S-C1 may be 1 to 100, and the acceleration charge / discharge sub- The number m of times S-C2 may be 1 to 100.

Therefore, one cycle of normal charge / discharge and one cycle of acceleration charge / discharge cycle are repeated continuously. (At least one normal charging / discharging sub-cycle S (at least once) between the acceleration charging / discharging, that is, between the acceleration charging / discharging sub-cycle (S-C2) and the acceleration charging / discharging sub- -C1). Referring to FIG. 1, for example, when n and m are 1 and N is 3, the first step is S-C1 → S-C2 → S-C1 → S-C2 → S-C1 proceeds between any one of the S-C2 and the adjacent S-C2, including the steps of S-C1 - > S-C2.

According to the present invention, the cycle life of a cell can be evaluated accurately in a short period of time by periodic repetition of a normal charge / discharge sub-cycle (S-C1) and an acceleration charge / discharge sub-cycle (S-C2). That is, the life evaluation time is shortened by the acceleration charge / discharge sub-cycle (S-C2). The normal charge / discharge sub-cycle (S-C1) proceeds between the accelerating charge / discharge sub-cycle (S-C2) and the cycle life of the cell can be accurately evaluated.

In evaluating the cycle life of the cell, the larger the number m of acceleration charge / discharge sub-cycles (S-C2), the more advantageous it is to shorten the life evaluation time. However, when only the acceleration charge / discharge sub-cycle (S-C2) is continuously repeated, that is, during the acceleration charge / discharge sub-cycle (S-C2) The deterioration of the cell becomes serious, and the cell has abnormal characteristics. Specifically, deterioration in deterioration is added to the cell, which makes it difficult for the cell to be driven normally, which degrades the accuracy of life evaluation. At this time, although it is possible to consider a method of determining the continuous repetition frequency (acceleration coefficient) of only accelerating charge / discharge which enables normal driving, it is difficult to determine the acceleration coefficient and takes a long time. Also, the determined acceleration coefficient is not accurate.

The present invention improves this. That is, according to the present invention, the acceleration charge / discharge sub-cycle (S-C2) and the acceleration charge / discharge sub-cycle , The deterioration due to acceleration is recovered by the normal charge / discharge sub-cycle (S-C1), and the cell has a normal characteristic . Accordingly, the accuracy of the life evaluation is high.

Further, according to an exemplary embodiment of the present invention, the main-cycle MC may include one or two or more intervals. The two or more intervals means that there are two or more intervals of different sub-cycles (S-C1) and (S-C2) belonging to the main-cycle (MC). For example, the main-cycle MC includes P ₁ ,..., P _M intervals (M is an integer of 1 or more), and at least one of the intervals includes a normal charge / discharge sub- The conditions and the number of cycles (S-C1) and acceleration charge / discharge sub-cycle (S-C2) may be different. More specifically, the values of n, m, and n / m may be different. For example, the main-cycle (MC), the said M is a case where 3, P _1, P ₂ and being of the P ₃ region, from a dual P ₂ interval is accelerated charge than P ₁ and P ₃ sections / The number of repetition of the discharge sub-sub cycle (S-C2) may be increased. For example, n / m of P ₂ section is 0.01 to 1, and n / m of P ₁ and P ₃ section may be 1 to 100.

According to another exemplary embodiment of the present invention, it is preferable that the normal charge / discharge sub-cycle (S-C1) and the acceleration charge / discharge sub-cycle (S-C2) proceed as follows. The preferred embodiments described below are usefully applied to, for example, supercapacitors, and more specifically, hybrid capacitors, for example. This will be described with reference to Figs. 2 to 4. Fig.

FIG. 2 and FIG. 3 illustrate the first step of the present invention, which is a graph showing voltage characteristics with time. FIG. 2 shows an initial one main-cycle MC. More specifically, FIG. 2 shows an example of an initial acceleration / discharge sub-cycle S- And a main-cycle MC including a charge / discharge sub-cycle S-C2. And FIG. 3 schematically shows N main-cycles (M-C). Figure 4 also shows the entire flow chart of a measurement method according to an exemplary aspect of the present invention. The numerical values in Fig. 4 are merely illustrative for convenience of explanation.

First, the normal charge / discharge sub-cycle S-C1 is a constant charge / discharge sub-cycle S-C1 after the cell is charged at a constant current under normal conditions according to an exemplary embodiment of the present invention, A normal charging step of charging the battery with the battery; And a constant discharge step of discharging to a constant current (CC). At this time, the normal charge / discharge sub-cycle S-C1 may further include a rest step prior to charging the constant current (CC) in the initial one time (n = 1). The resting step may be carried out for, for example, 10 seconds to 5 minutes. By this dormant step, the cell can be self-discharged and / or charged, and can have a voltage of, for example, zero to 0.5V.

In the present invention, " idle " is included here as long as it does not proceed with charging and discharging. The pause may proceed, for example, through the power off. Further, in the present invention, the constant current (CV) and the constant voltage (CV) mean a current and a voltage which are kept constant as defined above, and their actual values are not limited.

A first voltage at a constant current (CC) of the constant current (CC) charging, and constant voltage (CV), but the continuous progress of charging, the constant current (CC) a first current (I ₁₎ in the charge in normal conditions, the normal charging step (V ₁ ). At this time, the first current I ₁ and the first voltage V ₁ are current and voltage under normal conditions, respectively, and they are in accordance with the type and size of the cell. The first current I ₁ is the rated current I _R of the corresponding cell, which can be determined, for example, according to the rated capacitance C _R of the cell. The first current I ₁ may be, for example, 1 mA / F to 100 A / F, and more specifically, 5 mA / F to 75 mA / F, for example. And the first voltage (V ₁ ) is the rated voltage (V _R ) of the corresponding cell. After the constant current (CC) is charged, the constant voltage (CV) is charged at the first voltage (V ₁ ), that is, at the rated voltage (V _R ).

In the normal charging step, the constant current (CC) charging time (T ₁ -T ₂ period in FIG. 2) may be a time to reach the first voltage V ₁ , that is, a time to reach the rated voltage V _R . The constant current (CC) charging time (T ₁ -T ₂ ) may be, for example, 1 minute to 10 minutes, and may be 5 minutes for a more specific example. The constant-voltage (CV) charge time (in the range of T _{2 to} T ₃ in FIG. 2) may be, for example, 10 minutes to 60 minutes, and more specifically 30 minutes.

In the steady-state discharge step, the constant current (CC) of the first current (I ₁ ) is discharged to the second voltage (V ₂ ). The first current (I ₁ ) in this steady-state discharge step is the same as the normal charge step. That is, the first current I ₁ may be 1 mA / F to 100 A / F as illustrated above, and more specifically, 5 mA / F to 75 mA / F, for example. It is preferable that the second voltage (V ₂ ) satisfies the following formula (1).

[Equation 1]

_{0 ≤ V 2 / V 1 ≤} 0.9

In Equation (1), V ₁ is the first voltage (V ₁ ) of the normal charging step, that is, the rated voltage (V _R ) of the corresponding cell. The second voltage V ₂ may be, for example, 0.1 V ₁ (V _R ) to 0.9 V ₁ (V _R ), and more specifically 0.4 V ₁ (V _R ) to 0.6 V ₁ (V _R ).

In the steady-state discharge step, a constant current (CC) discharge time (T ₃ -T ₄ period in FIG. ₂ ) may be a time to reach a second voltage (V ₂ ) satisfying the formula (1). The constant current (CC) discharge time (T ₃ -T ₄ section) can be, for example, 1 minute to 10 minutes, and more specifically 5 minutes.

Further, according to an exemplary embodiment, the steady-state discharge step may be divided into two steps. Specifically, the steady-state discharge step includes a first discharging step (a) of discharging the first current (I ₁ ) to the drop voltage with a constant current (CC) of the first current (I ₁ ) V < ₂ >). The primary discharge step a) can be carried out for, for example, 1 second to 10 seconds, more specifically, for 2 seconds, and the secondary discharge step b) is performed for 2 to 8 minutes, 4 minutes and 58 seconds.

The acceleration charging / discharging sub-cycle (S-C2) includes an acceleration charging step of charging a cell with a constant current (CC) under acceleration conditions and then charging it with a constant voltage (CV) according to an exemplary embodiment of the present invention; And an accelerated discharge (CC) discharge step.

In the acceleration charging / discharging sub-cycle (S-C2), the acceleration condition is included here as long as it is a severe charging / discharging condition than the normal condition as described above. Specifically, for example, a temperature, a current, And the like. More specifically, in the case of temperature, it may be selected from temperature conditions lower or higher than the actual operating temperature range of the cell. And in the case of current and voltage, it can be selected from the current and voltage higher than the used standard of the corresponding cell. More specifically, in the case of a current, a voltage higher than the first current I ₁ of the normal charge / discharge sub-cycle S-C1 and a voltage higher than the rated voltage V _{R in} the case of voltage . Accelerating condition, and preferably may be selected from the current, more specifically, may be selected as illustrated in the following from the first current (I ₁₎ higher than the second current (acceleration current, I _2).

A constant current (CC) of the constant current (CC) charging, and constant voltage (CV), but the continuous progress of charging, the constant current (CC) charging the second current (I ₂₎ in an acceleration condition, the accelerated-charge phase in accordance with the exemplary form And charges up to the first voltage V ₁ . At this time, the second current I ₂ is an acceleration current, and is not particularly limited as long as it is higher than the first current I _{1 in} the normal charge / discharge sub-cycle S-C1. The second current I ₂ may be 1.2 times or more, for example 1.2 times to 40 times as much as the first current I ₁ , and preferably satisfies the following formula (2) good.

&Quot; (2) "

1.5? I ₂ / I ₁ ? 20

When the second current I ₂ satisfies the above formula (2), it is useful for an acceleration condition such as a super capacitor or the like, more specifically, an acceleration condition such as a hybrid capacitor. That is, it is very advantageous in shortening the life evaluation time of the hybrid capacitor or the like. More specifically, the second current I ₂ may be 2 to 15 times the first current I ₁ . If the first of the second current (I _2), as a example, 10 times the first current (I ₁₎ of an example, the first current (I ₁₎ 25mA / F, which may be an acceleration current of 250mA / F .

In the acceleration charging step, the constant current (CC) charging time (T ₆ -T ₇ period in FIG. 2) is the time to reach the first voltage (V ₁ ) by charging the second current (I ₂ ) It may be a time to reach the rated voltage V _R. This constant current (CC) charging time (T ₆ -T ₇ ) may be, for example, 1 second to 10 seconds, and may be 5 seconds for a more specific example. And constant voltage (CV) charging time (in FIG. 2, T ₇ -T ₈ sections), the first example can be minutes, 1 minute to 5 in the first voltage (V _1), and may contain three minutes, a more specific example have.

In the acceleration discharge step, the second current (I ₂ ) is discharged to the second voltage (V ₂ ) by the constant current (CC). At this time, the second current (I ₂ ) and the second voltage (V ₂ ) in the acceleration discharge step are as described above. That is, the second current I ₂ is the current of the acceleration charging step, which preferably satisfies the above-mentioned expression (2). The second voltage (V ₂ ) in the accelerating and discharging step is a voltage in the steady-state discharging step, which preferably satisfies the above-mentioned formula (1).

In addition, in the accelerated discharge step, the constant current (CC) discharge time (T ₈ -T ₉ period in FIG. 2) is the time to reach the second voltage V ₂ by the discharge of the second current I ₂ It may be a time to reach a voltage satisfying the above-mentioned formula (1). This constant current (CC) discharge time (T ₈ -T ₉ ) may be, for example, 1 second to 10 seconds, and may be 5 seconds, for example.

Also, in the present invention, the main-cycle MC includes a normal charge / discharge sub-cycle S-C1 and an acceleration charge / discharge sub-cycle S-C2 as described above, . At this time, the stoppage is a first idle period (R1) running after the normal charge / discharge sub-cycle (S-C1); And a second idle period R2 running after the acceleration charge / discharge sub-cycle (S-C2). More specifically, the main-cycle MC includes a first idle period R1 implemented after one or more normal charge / discharge sub-cycles S-C1 and / or one or more accelerated charge / discharge sub- - a second idle period R1 that is performed after the cycle (S-C2) is performed. The hibernation may proceed, for example, through power off as described above.

At this time, the first idle period R1 proceeds after the steady-state discharge period of the normal charge / discharge sub-cycle S-C1, and may be performed for, for example, 1 minute to 10 minutes. In addition, the first pause R1 may include a first pause step R11 and a second pause step R12. And during a first rest stage (R11) is for 10 seconds to two minutes (in FIG. 2, T ₄ -T ₅ sections) may proceed, the secondary rest stage (R12) is 2 minutes to 8 minutes of ( In Fig. 2, T ₅ -T ₆ section). More specifically, for example, the first resting step R11 may be performed for one minute, and the second resting step R12 may be performed for four minutes.

Also, the second pause R2 proceeds after the accelerated discharge phase of the acceleration charge / discharge sub-cycle S-C2, and may proceed for example for 1 to 10 minutes. In the case of the second rest period R2, the first rest period R21 and the second rest period R22 may be included. And the first rest stage (R21) is for 10 seconds to two minutes may be carried out (in FIG. 2, T ₉ -T ₁₀ intervals), while the second rest stage (R22) is 2 minutes to 8 minutes of ( in Figure 2, it can be carried out T ₁₀ -T ₁₁ intervals). More specifically, for example, the first dormant step R21 may be performed for one minute and the second dormant step R22 may proceed for four minutes.

Meanwhile, the first step of the present invention may further include a normal charge / discharge stability-cycle (C3) which proceeds after repeating the main-cycle (M-C) as described above several times. That is, it may further include a normal charge / discharge stability-cycle (C3) which follows the acceleration charge / discharge sub-cycle (S-C2). Specifically, the normal charge / discharge stability-cycle C3 is performed after the acceleration charge / discharge sub-cycle S-C2 of the N times of the main-cycle MC, more specifically, After the second pausing period (R2).

The normal charge / discharge stability-cycle C3 is for stabilizing the cell deteriorated by the acceleration charge / discharge sub-cycle (S-C2), and it proceeds under normal conditions. This normal charging / discharging stable-cycle (C3) turns charging and discharging (charging / discharging) into one cycle under normal conditions, and performs one charge / discharge cycle at least once. For example, proceed one to three times. At this time, the charging / discharging condition of the normal charging / discharging stable-cycle (C3) is the same as the condition (normal condition) of the normal charging / discharging sub-cycle (S-C1).

Specifically, the normal charge / discharge stability-cycle (C3) includes a normal charge step in which the cell is charged with a constant current (CC) under a normal condition and then charged with a constant voltage (CV); And a constant discharge step of discharging to a constant current (CC). In this normal charging / discharging stable-cycle (C3), the specific embodiments of the normal charging stage and the normal discharging stage are as described in the normal charging / discharging sub-cycle (S-C1) Is omitted. In FIG. 3, the normal charge / discharge stability-cycle (C3) is a period of time T ₁₁ -T ₁₂ .

3 and 4, in the present invention, the first process is a full discharge cycle (hereinafter referred to as a full discharge cycle) which is followed by the normal charge / discharge stability- C4). ≪ / RTI > That is, through the full discharge cycle C4, the corresponding cell is discharged to the discharge voltage. In Fig. 3, the full discharge cycle C4 is a period of time T ₁₂ -T ₁₅ .

The complete discharge cycle (C4) is a specific example, the normal charge / discharge stability-discharged to then proceed with the cycle (C3), a first current-constant current (CC) to a third voltage (V ₃₎ of (I ₁₎ and constant current (CC) discharging method comprising, the first may include a constant voltage (CV) a holding step of holding for a predetermined time, the third voltage (V _3). At this time, the first current I ₁ is as described above. The third voltage V ₃ is a total discharge voltage (minimum voltage) of the corresponding cell, which may vary depending on the type of the cell. The third voltage V ₃ may be, for example, from zero to 1.15V. The third voltage V ₃ may be an intrinsic OCV (open circuit voltage) of the cell and may vary from cell to cell, for example from 0 to 1V.

Further, in the full discharge cycle (C4), a constant current (CC) discharging time (in Fig. 3, the time interval T ₁₂ -T ₁₃₎ is if the time taken to reach a third voltage (V ₃₎ is not particularly limited. For example, from 1 minute to 10 minutes. And the constant voltage (CV) holding time (in the period of time T ₁₃ -T ₁₅ in FIG. 3) may be, for example, 5 minutes to 60 minutes. At this time, in some cases, the cell may experience a slight voltage rise in the step of holding the constant voltage (CV). For example, in FIG. 3, the voltage may slightly rise at time T ₁₄ of the period of time T ₁₃ -T ₁₅ .

Meanwhile, in the present invention, the second step evaluates at least the cycle life of the cell. At this time, the lifetime of the cell can be evaluated through at least one selected from the rate of change in capacitance and the rate of change in resistance after the first step.

To this end, the second step comprises a first step of measuring an initial capacity of the cell, according to a first embodiment; A second step of measuring a holding capacity after repeating the first step; And a third step of determining the cycle life of the cell by comparing the initial capacity and the storage capacity.

In the first step, the initial capacity before the normal charge / discharge sub-cycle (S-C1) is measured. At this time, the initial capacitance may be, for example, the rated capacitance C _R of the corresponding cell. Then, in the process of repeating the first process N times, the holding capacity held by each cell is measured. That is, the storage capacity of the second stage is the cell capacity at N times. Then, the initial capacity is compared with the retention capacity at N times to evaluate the cycle life of the cell. (Third Step) At this time, in the third step, for example, the cell according to the following formula (3) (Predicted) the cycle life of the battery.

&Quot; (3) "

C _N / C _o ≤ C _s

In Equation (3), C _O is the initial capacity, and C _N is the holding capacity after N times the first process. And C _s is a reference capacity, which may vary depending on the type of cell but is 0.5 to 0.8.

For example, when the reference capacitance C _s is 0.8, the first process is repeated until the holding capacitance C _N reaches 80% of the initial capacitance. In this case, 5 to 1000 times of the N times may be evaluated (predicted) by the actual cycle life of the corresponding cell, but this may vary depending on acceleration conditions and the like.

The holding capacity C _N may be a discharge capacity value of the normal charge / discharge sub-cycle S-C1 constituting the main-cycle MC, for example. More specifically, the holding capacity C _N may use the measured capacity after progressing the constant current (CC) discharge in the Nth normal charge / discharge sub-cycle (S-C1). At this time, measurement of the holding capacity C _N is not particularly limited, and it can be calculated, for example, according to the following equation (4).

&Quot; (4) "

C _N =? T * I ₁ * C _R / (V _N - V _R )

In Equation (4), V _N is the voltage at the time of measurement, and V _R is the first voltage (V ₁ ) as described above. And T is a constant current (CC) discharge time (in FIG. 2, a period of time T ₃ -T ₄ , unit is sec), I ₁ is the first current as described above, and C _R is the rated capacitance to be.

In the present invention, the holding capacity C _N used for evaluating the lifetime of the cell may be the discharge capacity after repeating the main-cycle MC several times (N times) The discharge capacity in the sub-cycle (S-C1), or the discharge capacity measured after proceeding the normal charge / discharge stability-cycle (C3).

In addition to the first and second processes, the present invention may further include a step of measuring electrical characteristics of the cell. A third step of measuring a leakage current (LC), for example; A fourth step of measuring resistance; And a fifth step of measuring the self-discharge.

At this time, the third process (leakage current measurement) may be performed, for example, in the charging step of the normal charge / discharge sub-cycle (S-C1). This third step is for examining the leakage current (LC) at the time of charging the constant voltage (CV) under the normal condition, and this may be performed 30 seconds before the end of the charging of the constant voltage (CV) as a specific example. This measurement of the leakage current (LC) can be used as a measure to evaluate the initial basic characteristics of the cell, which can also be used as a cycle life evaluation of the cell.

Also, the fourth step (resistance measurement) may proceed in the process of discharging and / or after discharging. At this time, the resistance measured through the fourth step is at least one selected from a DC resistance and an AC resistance.

According to an exemplary embodiment, the fourth step includes a first resistance measuring step that proceeds in the course of a constant current (CC) discharge of the normal charge / discharge sub-cycle (S-C1); And a second resistance measuring step that proceeds after proceeding a constant current (CC) discharge of the normal charge / discharge sub-cycle (S-C1).

The normal charge / discharge sub-cycle in the (C1-S), a constant current (CC), the initial voltage drop has occurred during the discharge (2, the time T _3), and, whereby the resistance decreases. That is, an internal resistance drop (IR drop) occurs. The internal resistance drop (IR Drop) is measured in the first resistance measuring step. The first resistance measuring step may measure a DC equivalent series resistance (primary DC, ESR), for example. In addition, the normal charge / discharge sub-cycle in the (C1-S), then proceed to the constant current (CC) discharging, the more specifically a first resting period (R1) the voltage rises (Fig. 2, the time T ₄ -T ₅ Thereby increasing the resistance. That is, an internal resistance increase (IR Raise) occurs. At this time, the second resistance measuring step measures the IR resistance. The second resistance measuring step can measure a DC equivalent serial resistance (secondary DC. ESR), for example.

The resistance measuring method in the fourth step is not particularly limited. For example, when the first resistance measuring step is DC, the following Equation 5 and Graph 1 can be followed.

&Quot; (5) "

R _d =? V / I

[Graph 1]

In the above equation (5) and the graph 1, R _d is a direct-current internal resistance (DC. IR), △ V is the voltage drop generated at the time of constant current (CC) discharging (△ V _3). And I is the discharge current, which is the above-mentioned first current (I ₁ ). At this time, the discharge current may be in accordance with the following a) to c). In addition, the voltage drop does not indicate an instantaneous voltage △ V ₄ falls to the time the discharge begins, may indicate a voltage △ V ₃ drops obtained from the intersection of the time starting at the time of extending the linear portion of the secondary line and the discharge start have.

a) If ΔV ₃ exceeds 20% (0.20 × V _R ) of the charging voltage, the current value can be reduced to 1/2, 1/5 or 1/10.

b) The discharge current value of 10 A or less can have one significant digit, and the second digit of the calculated value can be truncated.

c) The discharge current value over 10 A has two significant digits, and the third digit of the calculated value can be truncated.

On the other hand, the resistance measured in the fourth step can be used, for example, to evaluate the initial basic characteristics of the cell or to evaluate the cycle life of the cell. That is, it is possible to estimate (predict) the cycle level of the cell through the rate of change of the measured resistance.

More specifically, in the present invention, the second step includes: a) measuring the initial resistance of the cell according to the second embodiment; B) measuring the holding resistance after repeating the first step; And c) comparing the initial resistance with the holding resistance to evaluate the cycle life of the cell. At this time, the step c) can evaluate (predict) the cycle life of the cell based on, for example, the following formula (6).

&Quot; (6) "

R _N / R _o ≤ R _s

In Equation (6), R _O is an initial resistance, and R _N is a holding resistance after N times the first process. And R _s is a reference resistance, which is may be different depending on the type of cell, but 2 to 5.

For example, when the reference resistance R _s is 2, the first step is repeated until the holding resistance R _N becomes twice the initial resistance. And, 5 to 1000 times of N times can be evaluated (predicted) by the actual cycle life of the corresponding cell, but it may be different depending on the acceleration condition and the like.

Further, the self-discharge of the fifth step can be measured according to the following [Graph 2] and the conditions a) to d).

[Graph 2]

a) Before the measurement, the cell shall be fully discharged and the discharge time shall be from 1 h to 24 h and shall be specified in the relevant standard.

b) Directly apply the rated voltage ( V _R ) to the cell terminals without a charge protection resistor. At this time, the charging time is set to 8h including the maximum charging rise time 30 min at which the applied voltage reaches 95%.

c) Open the terminal of the cell at the voltage source. At this time, the cell is kept at the standard state for 16 h or 24 h.

d) Use a DC voltmeter with an internal resistance value of 1 MΩ or more.

As described above, according to the present invention described above, it is possible to accurately measure the cycle life of the cell, for example, the cycle life of the cell such as the hybrid capacitor in a short period of time. In addition, electrical characteristics such as leakage current, resistance and / or capacitance can be measured in the course of measuring the cycle life of the cell.

Claims (15)

A first step of repeating the main-cycle by forming a normal charge / discharge sub-cycle for charging and discharging under normal conditions and an acceleration charge / discharge sub-cycle for charging and discharging under acceleration conditions as one main-cycle;
And a second step of evaluating a cycle life of the cell in which the first process is performed,
Wherein the main-cycle comprises: a first idle period following a normal charge / discharge sub-cycle; And a second rest period that proceeds after the accelerating charge / discharge sub-cycle,
In the first step, the main-cycle is repeated several times,
Normal charge / discharge stable cycle of charging / discharging under normal conditions; And
And a full discharge cycle for completely discharging the cell,
In the second step,
A first step of measuring an initial capacity of the cell;
A second step of measuring a holding capacity after repeating the first step; And
And a third step of comparing the initial capacity with the storage capacity to determine the cycle life of the cell.
The method according to claim 1,
The normal charge / discharge sub-
A normal charging step of charging a constant voltage (CV) after being charged with a constant current (CC); And
And discharging a constant current (CC).
3. The method of claim 2,
Charging the constant current (CC) of the normal charge stage to a first voltage,
The normal discharge step discharges to a second voltage,
Wherein the second voltage satisfies the following equation.

[Mathematical Expression]
_{0 ≤ V 2 / V 1 ≤} 0.9
(Where V ₁ is the first voltage and V ₂ is the second voltage as the rated voltage (V _R ) of the cell).
The method according to claim 1,
The acceleration charge / discharge sub-
An accelerating charging step of charging a constant current (CC) and then charging a constant voltage (CV); And
And discharging a constant current (CC).
5. The method of claim 4,
The constant current (CC) charging of the accelerating and charging step is charged with the constant current (CC) of the second current,
Wherein the second current satisfies the following equation.

[Mathematical Expression]
1.5? I ₂ / I ₁ ? 20
(Where I ₁ is the rated current of the cell (I _R ) and I ₂ is the second current).
The method according to claim 1,
Wherein the full discharge cycle includes a constant current (CC) discharge step of discharging to a full discharge voltage, and a constant voltage (CV) holding step of maintaining the full discharge voltage.
The method according to claim 1,
Wherein the second step evaluates the cycle life of the cell through at least one selected from a capacitance change rate and a resistance change rate.
The method according to claim 1,
Wherein the third step determines the cycle life of the cell based on the following formula.

[Mathematical Expression]
C _N / C _o ≤ C _s
(C _O is the initial capacity, C _N is the holding capacity after repeating the first process, and C _s is 0.5 to 0.8 as the reference capacity).
The method according to claim 1,
In the second step,
A) measuring the initial resistance of the cell;
B) measuring the holding resistance after repeating the first step; And
And comparing the initial resistance with the holding resistance to determine the cycle life of the cell.
The method according to claim 1,
Further comprising the step of measuring an electrical characteristic of the cell.
11. The method of claim 10,
Wherein the electrical characteristic is at least one selected from the group consisting of leakage current, resistance, and capacitance.
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