High-speed battery defect inspection method

Abstract

The present invention relates to a high-speed battery defect inspection method, and specifically, to a high-speed battery defect inspection method for determining whether a battery formed by stacking a plurality of single cells is defective in a short time by predicting degradation characteristics of the battery.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0140870 filed on October 28, 2022, the entire disclosure of which is incorporated as a part of this specification.

[0002] The present disclosure relates to a high-speed battery defect inspection method, and more particularly to a high-speed battery defect inspection method for determining a battery defect in a short time by predicting degradation characteristics of a battery formed by stacking a plurality of single cells. Background Art

[0003] In the case of a medium or large-sized battery in which a plurality of single cells are stacked, there are problems in that some of the internal single cells exhibit a low voltage defect phenomenon (a phenomenon in which the potential of a specific single cell decreases) the cause of which is unknown, and a defect phenomenon in which the capacity of all cells deteriorates.

[0004] Products such as ESS and vehicle batteries equipped with shipped low-voltage defective cells exhibit significant performance instability over long periods of time and may reduce product reliability.

[0005] Conventionally, battery voltage tracking is performed to detect low voltage defective batteries in the battery shipping stage. In the case of battery voltage tracking, it generally takes a long time of 2 weeks or more. In addition, there is a high pressure current detection (HPCD) inspection method that considers the main cause of low voltage defects as a folding phenomenon of spacers, but there are limitations on detection by the HPCD inspection method.

[0006] Therefore, there is a need for an inspection method that can detect low voltage defective cells using existing inspection methods and inspect all cells simultaneously in a short time. Summary of the invention

[0007] Technical goals

[0008] The present disclosure relates to a high-speed battery defect inspection method, and particularly to a high-speed battery defect inspection method by predicting degradation characteristics of a battery formed by stacking a plurality of single cells and determining a battery defect in a short time.

[0009] The technical objectives to be achieved by the present disclosure are not limited to the above-mentioned technical objectives, and those skilled in the art will clearly understand other technical objectives not mentioned from the following description.

[0010] Technical Solution

[0011] The high-speed battery defect inspection method disclosed herein may include:

[0012] an analysis target impedance measuring step (s30) of obtaining an analysis target impedance as the impedance of the analysis target battery by applying an alternating current of a set frequency to the analysis target battery;

[0013] a real resistance extraction step ( S40 ) of extracting a real part value from the analysis target impedance as the real resistance; and

[0014] a defect determination step (s50) of determining a defect of the analysis target battery based on the real resistance,

[0015] Here, the set frequency is selected from frequencies when the imaginary resistance as the imaginary part value of the analysis target impedance is greater than 0.

[0016] Beneficial Effects

[0017] The high-speed battery defect inspection method disclosed herein can detect low-voltage defective batteries in a short time and can inspect thousands to tens of thousands of batteries per second.

[0018] The high-speed battery defect inspection method of the present disclosure is capable of performing non-destructive inspection on finished batteries and can be applied to batteries in a large-scale production line as well as batteries that have already been produced.

[0019] The high-speed battery defect inspection method of the present disclosure significantly reduces inspection time compared to conventional methods, and is capable of determining defects even in batteries that have not yet been inspected. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a block diagram illustrating a high-speed battery defect inspection method of the present disclosure.

[0021] Figure 2 is a graph illustrating a general Nyquist plot.

[0022] Figure 3 It is a graph comparing the impedance values ​​of normal batteries and defective batteries.

[0023] Figure 4 is a block diagram illustrating another embodiment of the high-speed battery defect inspection method of the present disclosure.

[0024] Figure 5 is a block diagram illustrating the steps of setting the frequency. DETAILED DESCRIPTION

[0025] The high-speed battery defect inspection method disclosed herein may include:

[0026] an analysis target impedance measuring step (s30) of obtaining the impedance of the analysis target battery as measured by applying an alternating current of a set frequency to the analysis target battery;

[0027] a real resistance extraction step ( S40 ) of extracting a real part value from the analysis target impedance as the real resistance; and

[0028] a defect determination step (s50) of determining a defect of the analysis target battery based on the real resistance,

[0029] Here, the set frequency is selected from frequencies where the imaginary part value of the analysis target impedance is greater than 0.

[0030] In the high-speed battery defect inspection method disclosed in the present invention, the setting frequency can be from 10 -2 kHz to 7 MHz.

[0031] In the high-speed battery defect inspection method of the present disclosure, the analysis target battery may include a plurality of single cells.

[0032] High-speed battery defect inspection method disclosed herein

[0033] Before the target impedance measurement step (s30), the following steps may also be included:

[0034] a reference impedance measuring step (s10) of obtaining a plurality of reference impedances for a plurality of frequencies by applying an alternating current to a reference battery while changing the frequency; and

[0035] A set frequency calculation step (s20) is to calculate a set frequency based on a plurality of reference impedances.

[0036] In the high-speed battery defect inspection method of the present disclosure, the reference battery may have a dOCV of 300 mV or more or 3 sigma or more.

[0037] In the high-speed battery defect inspection method of the present disclosure, the setting frequency calculation step (s20) may include separating the plurality of reference impedances into real part values ​​Z SR and the imaginary value Z SI The variable separation step (s21), fitting function f to Z SR With Z SI A function fitting step (s22) of the correlation, and a set frequency acquisition step (s23) of acquiring a set frequency based on the function.

[0038] In the function fitting step (s22) of the high-speed battery defect inspection method of the present disclosure, the function f can be fitted by the following equation of Formula 1:

[0039] [Formula 1]

[0040] .

[0041] In the setting frequency acquisition step (s23) of the high-speed battery defect inspection method disclosed in the present invention, for ZSI In the section where the value of is greater than 0, the set frequency can be selected from the frequencies that satisfy the equation of the following formula 2.

[0042] [Formula 2]

[0043]

[0044] Where ε is from 0.0 to 0.2.

[0045] In the setting frequency acquisition step of the high-speed battery defect inspection method disclosed in the present invention, ε may be 0.

[0046] In the defect determination step (s50) of the high-speed battery defect inspection method disclosed in the present invention, when the real resistance is relative to Z satisfying Formula 2 SI When the value is at least 30% greater, the analysis target battery can be determined to be a defective battery.

[0047] The battery activation method of the present disclosure may include:

[0048] An activated battery preparation step, which assembles an activated target battery;

[0049] A charge / discharge step, which charges or discharges the activated target battery;

[0050] a stabilization step of stabilizing the activated target battery by storing the activated target battery at a set temperature and a set humidity for a predetermined period of time; and

[0051] A defect screening step of finally screening out defective batteries by performing a high-speed battery defect inspection method using the activated target battery as the analysis target battery.

[0052] The battery activation method disclosed herein,

[0053] Between the activation battery preparation step and the charge / discharge step, the following may also be included:

[0054] A pre-inspection step of pre-inspecting the activation target battery by performing a high-speed battery defect inspection method using the activation target battery as the analysis target battery.

[0055] Mode for carrying out the invention

[0056] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In the process, the size or shape of the components shown in the accompanying drawings may be exaggerated for clarity and ease of description. In addition, the terms specifically defined in consideration of the configuration and operation of the present disclosure may vary according to the intention or habits of the user and operator. The definitions of these terms should be made based on the content throughout this specification.

[0057] Figure 1is a block diagram illustrating a high-speed battery defect inspection method of the present disclosure. Figure 2 is a graph illustrating a general Nyquist plot. Figure 3 It is a graph comparing the impedance values ​​of normal batteries and defective batteries. Figure 4 is a block diagram illustrating another embodiment of the high-speed battery defect inspection method of the present disclosure. Figure 5 is a block diagram illustrating the steps of setting the frequency.

[0058] In the following, reference Figures 1 to 5 , the high-speed battery defect inspection method disclosed in the present invention will be described in detail.

[0059] like Figure 1 As shown in , the high-speed battery defect inspection method disclosed in the present invention may include:

[0060] an analysis target impedance measuring step (s30) of obtaining an analysis target impedance as the impedance of the analysis target battery by applying an alternating current of a set frequency to the analysis target battery;

[0061] a real resistance extraction step ( S40 ) of extracting a real part value from the analysis target impedance as the real resistance; and

[0062] a defect determination step (s50) of determining a defect of the analysis target battery based on the real resistance,

[0063] The set frequency is selected from the frequencies when the imaginary part value of the analysis target impedance is greater than 0.

[0064] In the high-speed battery defect inspection method of the present disclosure, the analysis target battery may include a plurality of single cells.

[0065] When one or more cathodes and one or more anodes are stacked with a spacer between them to form an electrode assembly, a unit cell may be a unit cell having electrodes of different types located on both sides of the outermost surface. For example, a unit cell may be a unit cell having the following electrode assembly, the electrode assembly having a structure in which cathode-spacer-anode is stacked in this order. For another example, a unit cell may be a unit cell having the following electrode assembly, the electrode assembly having a structure in which cathode-spacer-anode-spacer-cathode-spacer-anode is stacked in this order.

[0066] The cathode may be a cathode current collector coated with a cathode active material.

[0067] The anode may be an anode current collector coated with an anode active material.

[0068] The spacer may be an insulator through which ions pass.

[0069] In the step of analyzing the target impedance measurement (s30), the set frequency may be 10 -2 In the case of a low voltage defective battery, it has an impedance value different from that of a normal battery at a high frequency, and specifically shows a difference in a real component among the impedance values.

[0070] When performing impedance spectroscopy (EIS) on a battery, one can obtain Figure 2 Specifically, in the impedance value corresponding to each frequency, the value obtained by multiplying the imaginary part by (-) and the value of the real part can be displayed as a coordinate to obtain the value as shown in FIG. Figure 2 The high-speed battery defect inspection method disclosed in the present invention can be based on Figure 2 The real part value in the second quadrant of the curve graph is used to quickly identify low-voltage defects of the battery.

[0071] Figure 3 is a graph showing the impedance spectroscopy measurement results of 15 batteries. Figure 3 , five graphs of A_1, A_2, A_3, A_4 and A_5 are graphs of normal batteries, five graphs of E_1, E_2, E_3, E_4 and E_5 are graphs of grade E defective batteries, and five graphs of L_1, L_2, L_3, L_4 and L_5 are graphs of grade L defective batteries. Grade E defective batteries may be defective batteries showing a decrease in absolute open circuit voltage (OCV). Grade L defective batteries may be defective batteries showing a decrease in relative OCV. Figure 3 , it can be seen that the graphs of the EIS measurement values ​​of the low voltage defective batteries (the grade E defective battery and the grade L defective battery) overlap each other regardless of the defect grade, but the graph of the normal battery exhibits a different behavior from the graph of the defective battery. Specifically, at a measured impedance value of about 10 kHz, the normal battery appears in region A, and the grade E defective battery and the grade L defective battery appear in region B. In the case of the grade E defective battery and the grade L defective battery, it can be seen that they have the maximum value of the real part value in region B. Therefore, in the analysis target impedance measurement step (s30), the setting frequency may be from 10 -2 More preferably, the set frequency can be selected from 10 -1 kHz to 10 2 kHz. -2 The low voltage defective battery has an abnormal increase in the real resistance value within the frequency range of kHz to 7 MHz, and using this abnormal increase, it can be determined whether the battery is a low voltage defective battery.

[0072] like Figure 4As shown in , the high-speed battery defect inspection method disclosed in the present invention may further include, before the target impedance measurement step (s30),

[0073] a reference impedance measuring step (s10) of obtaining a plurality of reference impedances for a plurality of frequencies by applying an alternating current to a reference battery while changing the frequency; and

[0074] A set frequency calculation step (s20) is to calculate a set frequency based on a plurality of reference impedances.

[0075] The high-speed battery defect inspection method of the present disclosure can obtain an optimal set frequency capable of accurately detecting low-voltage defective batteries by performing a reference impedance measurement step (s10) and a set frequency calculation step (s20) before an analysis target impedance measurement step (s30).

[0076] In the reference impedance measurement step (s10), as a low voltage defective battery, the reference battery may have a delta open circuit voltage (dOCV) of 300 mV or more or 3 sigma or more. The reference battery as a low voltage defective battery may be obtained as a battery that has been inspected as a defective battery in a mass production process or a battery that has suffered a defect condition such as electrode folding and active material application area defects.

[0077] The reference impedance measuring step (s10) may be performed by impedance spectroscopy (EIS). Thus, a reference impedance value corresponding to each of a plurality of frequency values ​​may be obtained.

[0078] like Figure 5 As shown in FIG. 1 , the setting frequency calculation step (s20) may include separating the plurality of reference impedances into real part values ​​Z SR and the imaginary value Z SI The variable separation step (s21), fitting function f to Z SR With Z SI A function fitting step (s22) of the correlation, and a set frequency acquisition step (s23) of acquiring the set frequency based on the function.

[0079] In the function fitting step (s22) of the high-speed battery defect inspection method disclosed in the present invention, the function f can be fitted by the following formula 1:

[0080] [Formula 1]

[0081] .

[0082] In other words, in the function fitting step (s22), the real part value Z SR is the dependent variable and the imaginary value Z SI The function f is obtained as a function of the independent variable.

[0083] In the setting frequency acquisition step (s23), for Z SI For segments where the value of is greater than 0, a set frequency can be selected from frequencies that satisfy the following formula 2.

[0084] [Formula 2]

[0085] .

[0086] Wherein ε is a real number ranging from 0.0 to 0.2. For example, ε may be determined by considering the specification and capacity tolerance of the reference battery, the material and structure of the electrode material, etc. For another example, ε may be determined by considering the deviation value of the reference impedance values ​​obtained for a plurality of reference batteries.

[0087] In the set frequency step, ε can be zero. In other words, it can be obtained when the function f is replaced by Z SI The frequency when the value obtained by differentiation is 0 is used as the set frequency. More specifically, the frequency value when the function f has a maximum value can be obtained as the set frequency.

[0088] In the defect determination step (s50), when the real resistance is relative to Z satisfying Formula 2 SI When the value is at least 30% greater, the analysis target battery can be determined as a defective battery. As described above for the low voltage defective battery, the function f can have a maximum value relative to the set frequency, and the real resistance value can have an abnormally large value. According to the experimental example to be described later, it can be seen that at the set frequency, the real resistance value of the low voltage defective battery is more than twice the real resistance value of the normal defective battery. Therefore, when the real resistance is relative to Z satisfying the above formula 2, SI When the value is greater by at least 30% or more or 50% or more, the analysis target battery can be determined to be a low-voltage defective battery.

[0089] A battery activation method using the high-speed battery defect inspection method disclosed herein may include:

[0090] An activated battery preparation step, which prepares an activated target battery through an assembly process;

[0091] A charge / discharge step, which charges or discharges the activated target battery;

[0092] a stabilization step of stabilizing the activated target battery by storing the activated target battery at a set temperature and a set humidity for a predetermined period of time; and

[0093] A defect screening step of finally screening out defective batteries by performing a high-speed battery defect inspection method using the activated target battery as the analysis target battery.

[0094] The activation target battery prepared in the activated battery preparation step may be a battery that has completed a packaging process.

[0095] By applying the high-speed battery defect inspection method of the present disclosure to the battery activation process, the time required for battery defect inspection before shipment can be significantly reduced.

[0096] The battery activation method of the present disclosure may further include a pre-inspection step between the activation battery preparation step and the charge / discharge step, which pre-inspects the activation target battery by performing the high-speed battery defect inspection method of the present disclosure using the activation target battery as the analysis target battery.

[0097] The battery activation method disclosed herein can prevent the charge / discharge process and the aging process from being performed on defective batteries by preliminarily screening out defective batteries before the charge / discharge process and the aging process, and can remove defective batteries that may appear during the SEI layer formation process again by secondarily screening out defective batteries after the aging process.

[0098] Experimental Example

[0099] Fifteen 100Ah batteries were prepared after the activation process was completed, of which five were normal batteries, five were grade E defective batteries, and five were grade L defective batteries.

[0100] EIS was performed on 15 cells and the Figure 3 The results shown in .

[0101] In 5 normal batteries, the real resistance values ​​at a frequency of 10 kHz corresponding to the set frequency were measured as 500 μΩ, 480 μΩ, 470 μΩ, 490 μΩ and 520 μΩ, respectively, in 5 grade E defective batteries, the real resistance values ​​at a frequency of 10 kHz corresponding to the set frequency were measured as 1160 μΩ, 1140 μΩ, 1110 μΩ, 1130 μΩ and 1110 μΩ, respectively, and in 5 grade L defective batteries, the real resistance values ​​at a frequency of 10 kHz corresponding to the set frequency were measured as 1120 μΩ, 1070 μΩ, 1150 μΩ, 1140 μΩ and 1170 μΩ, respectively.

[0102] In other words, it can be seen that, in the low-voltage defective battery, a real resistance value twice or more larger than that of the normal battery at the set frequency is measured.

[0103] Although the embodiments according to the present disclosure have been described above, they are only illustrative, and those skilled in the art will appreciate that various modifications and embodiments of equivalent scope can be made therefrom. Therefore, the true technical protection scope of the present disclosure should be defined by the appended claims.

[0104] Industrial Applicability

[0105] The high-speed battery defect inspection method disclosed herein can detect low-voltage defective batteries in a short time and can inspect thousands to tens of thousands of batteries per second.

[0106] The high-speed battery defect inspection method of the present disclosure is capable of performing non-destructive inspection on finished batteries and can be applied to batteries in a large-scale production line as well as batteries that have already been produced.

[0107] The high-speed battery defect inspection method of the present disclosure significantly reduces inspection time compared to conventional methods, and is capable of determining defects even in batteries that have not yet been inspected.

Claims

1. A high-speed battery defect inspection method, comprising: an analysis target impedance measuring step (s30) of obtaining an analysis target impedance as an impedance of the analysis target battery measured by applying an alternating current of a set frequency to the analysis target battery; a real resistance extraction step (s40), wherein the real resistance extraction step extracts a real value from the analysis target impedance as a real resistance; as well as a defect determination step (s50) of determining a defect of the analysis target battery based on the real resistance, The set frequency is selected from frequencies when the imaginary part value of the analysis target impedance is greater than 0.

2. The method according to claim 1, wherein the set frequency is 10 -2 kHz to 7 MHz. The method according to claim 1 , wherein the analysis target battery includes a plurality of single cells.

4. The method according to claim 1, Before the target impedance analysis measurement step (s30), the method further includes: a reference impedance measuring step (s10) of obtaining a plurality of reference impedances for a plurality of frequencies by applying an alternating current to a reference battery while varying the frequency; as well as A set frequency calculation step (s20) is performed to calculate the set frequency based on the plurality of reference impedances. The method of claim 4 , wherein the reference cell has a dOCV of 300 mV or more or 3 sigma or more.

6. The method according to claim 4, wherein the setting frequency calculation step (s20) comprises: A variable separation step (s21), wherein the variable separation step separates the plurality of reference impedances into real part values ​​Z SR and the imaginary value Z SI ; Function fitting step (s22), the function fitting step fitting function f to convert the Z SR With the Z SI association; as well as A set frequency acquisition step (s23), wherein the set frequency acquisition step acquires the set frequency based on the function.

7. The method according to claim 6, wherein: In the function fitting step (s22), The function f is fitted by the following equation of Formula 1: [Formula 1] 。 8. The method according to claim 7, wherein: In the setting frequency acquisition step (s23), For the Z SI In the section where the value of is greater than 0, the set frequency is selected from the frequencies satisfying the equation of the following formula 2: [Formula 2] Among them, ε is between 0.0 and 0.

2.

9. The method according to claim 8, wherein in the setting frequency acquisition step, ε is 0.

10. The method according to claim 9, wherein: In the defect determination step (s50), When the real resistance is relative to the Z that satisfies the equation of Formula 2 SI When the value is greater than or equal to 30%, the analysis target battery is determined to be a defective battery.

11. A battery activation method comprising: An activated battery preparation step, wherein the activated battery preparation step assembles an activated target battery; A charging / discharging step, wherein the charging / discharging step charges or discharges the activated target battery; a stabilization step of stabilizing the activation target battery by storing the activation target battery at a set temperature and a set humidity for a predetermined period of time; as well as A defect screening step of finally screening out defective batteries by performing the high-speed battery defect inspection method according to claim 1 using the activation target battery as the analysis target battery.

12. The method according to claim 11, Between the activation battery preparation step and the charging / discharging step, the method further comprises: a preliminary inspection step of performing preliminary inspection on the activation target cell by performing the high-speed battery defect inspection method according to claim 1 using the activation target cell as the analysis target cell.

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