Battery diagnosis device and battery diagnosis method using same

Abstract

Provided are a battery diagnosis device and a battery diagnosis method using same, the device being capable of accurately measuring battery faults according to alternating current impedance data of a battery, measured using electrochemical impedance spectroscopy. The battery diagnosis device according to one aspect of the present invention comprises: a diagnosis model formation unit, which forms a first Nyquist plot in which determination points forming the shape of a Nyquist plot are marked using electrochemical impedance spectroscopy and using first alternating current impedance data as reference alternating current impedance data measured for a first battery, which a normal battery, at different frequencies; and a battery fault diagnosis unit which forms a second Nyquist plot in which determination points forming the shape of a Nyquist plot are marked using the electrochemical impedance spectroscopy and using second alternating current impedance data measured for a second battery, which is a battery to be diagnosed for faults, at different frequencies, and which compares the first Nyquist plot and the second Nyquist plot so as to diagnose faults in the second battery.

Description

Battery diagnostic device and battery diagnostic method using the same

[0001] The present invention relates to a battery diagnostic device and a battery diagnostic method using the same, and more particularly, to a battery diagnostic device capable of accurately measuring battery defects using electrochemical impedance spectroscopy (EIS) and a battery diagnostic method using the same.

[0002] Batteries, which are easy to apply to various product groups and have electrical characteristics such as high energy density, are also called accumulators or secondary batteries. In addition to their primary advantage of reducing the use of fossil fuels, they are attracting attention as a new energy source for environmental friendliness and energy efficiency enhancement because they do not generate any byproducts from energy use.

[0003] Therefore, batteries are widely used in portable devices, electric vehicles (EVs) driven by electrical power sources, and energy storage systems (ESSs), and research and development on battery management systems (BMSs), battery balancing circuits, and switching circuits are actively being conducted for more efficient battery management.

[0004] Meanwhile, the increased performance and capacity of these batteries can lead to system malfunctions, such as fires or explosions, which can lead to major accidents. Therefore, it is crucial to not only ensure safety and reliability during battery manufacturing, but also accurately diagnose defective batteries.

[0005] The purpose of the present invention is to provide a battery diagnosis device capable of accurately measuring battery defects based on AC impedance data of the battery measured using electrochemical impedance spectroscopy, and a battery diagnosis method using the same.

[0006] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0007] According to one aspect of the present invention, a battery diagnosis device includes a diagnosis model configuration unit configured to configure a first Nyquist plot in which judgment points constituting a shape of a Nyquist plot are displayed using first AC impedance data, which is reference AC impedance data measured for a first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy (EIS), and a battery failure diagnosis unit configured to configure a second Nyquist plot in which measurement points constituting a shape of a Nyquist plot are displayed using second AC impedance data measured for a second battery, which is a target battery for failure diagnosis, at different frequencies using the electrochemical impedance spectroscopy, and to diagnose a failure of the second battery by comparing the first Nyquist plot and the second Nyquist plot.

[0008] Preferably, the diagnostic model configuration unit may be configured to display the judgment points on the first Nyquist plot as a starting point of a semicircle of the first Nyquist plot, an ending point of a semicircle of the first Nyquist plot, a point where the negative value of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot, a first measurement point of the first AC impedance data, and a last measurement point of the first AC impedance data.

[0009] Preferably, the battery failure diagnosis unit may include a measurement data configuration unit configured to configure the second Nyquist plot and a measurement data reliability verification unit configured to determine the similarity of the graph trends of the first Nyquist plot and the second Nyquist plot.

[0010] Preferably, the measurement data configuration unit may be configured to display the measurement points on the second Nyquist plot as a starting point of a semicircle of the second Nyquist plot, an ending point of a semicircle of the second Nyquist plot, a point where the negative value of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot, a first measurement point of the second AC impedance data, and a last measurement point of the second AC impedance data.

[0011] Preferably, the measurement data reliability verification unit may be configured to perform at least one of: checking whether the imaginary component of the second AC impedance data continuously decreases between a starting point of the semicircle of the second Nyquist plot on the second Nyquist plot and a point where the negative value of the imaginary component of the second AC impedance data in the semicircle of the second Nyquist plot is maximum; checking whether the imaginary component of the second AC impedance data continuously increases between a point where the negative value of the imaginary component of the second AC impedance data in the semicircle of the second Nyquist plot on the second Nyquist plot is maximum and a semicircle ending point of the second Nyquist plot; and checking whether the imaginary component of the second AC impedance data continuously decreases between a semicircle ending point of the second Nyquist plot on the second Nyquist plot and a last measurement point of the second AC impedance data.

[0012] Preferably, the battery failure diagnosis unit may further include a primary failure diagnosis unit configured to primarily diagnose a failure of the second battery by performing at least one of a comparison between a first measurement point of the first AC impedance data on the first Nyquist plot and a first measurement point of the second AC impedance data on the second Nyquist plot and a comparison between a last measurement point of the first AC impedance data on the first Nyquist plot and a last measurement point of the second AC impedance data on the second Nyquist plot.

[0013] Preferably, the battery failure diagnosis unit may further include a secondary failure diagnosis unit configured to secondarily diagnose a failure of the second battery by performing at least one of a comparison between a starting point of a semicircle of the first Nyquist plot and a starting point of a semicircle of the second Nyquist plot, a comparison between a ending point of a semicircle of the first Nyquist plot and a ending point of a semicircle of the second Nyquist plot, and a comparison between a point in the semicircle of the first Nyquist plot where the negative value of the imaginary component of the first AC impedance data is maximum and a point in the semicircle of the second Nyquist plot where the negative value of the imaginary component of the second AC impedance data is maximum.

[0014] Preferably, the secondary failure diagnosis unit may further include a raw data diagnosis unit configured to secondarily diagnose a failure of the second battery based on at least one of a starting point of a semicircle of the first Nyquist plot, an ending point of a semicircle of the first Nyquist plot, and a point where the negative value of the imaginary component of the first AC impedance data in the semicircle of the first Nyquist plot is maximum, and an equivalent circuit model diagnosis unit configured to secondarily diagnose a failure of the second battery by comparing a judgment parameter value derived by constructing an equivalent circuit model based on the first Nyquist plot with a measurement parameter value derived by constructing an equivalent circuit model based on the second Nyquist plot.

[0015] A battery diagnosis method according to one aspect of the present invention includes the steps of constructing a first Nyquist plot in which judgment points constituting the shape of a Nyquist plot are indicated by using first AC impedance data, which is reference AC impedance data measured for a first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy, and the steps of constructing a second Nyquist plot in which measurement points constituting the shape of a Nyquist plot are indicated by using second AC impedance data measured for a second battery, which is a battery to be diagnosed as defective, at different frequencies using the electrochemical impedance spectroscopy, and comparing the first Nyquist plot with the second Nyquist plot to diagnose a defect in the second battery.

[0016] According to the battery diagnosis device of the present invention, a first Nyquist plot in which judgment points constituting the shape of a Nyquist plot are displayed using first AC impedance data measured for a first battery, which is a normal battery, and a second Nyquist plot in which measurement points constituting the shape of a Nyquist plot are displayed using second AC impedance data measured for a second battery, which is a battery to be diagnosed as defective, can be precisely diagnosed through a precise diagnosis using a plurality of comparison methods.

[0017] In addition, various additional effects can be achieved through various embodiments of the present invention. These various effects of the present invention will be described in detail in each embodiment, or descriptions of effects easily understandable to those skilled in the art will be omitted.

[0018] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0019] FIG. 1 is a drawing showing a battery diagnostic device according to one embodiment of the present invention.

[0020] FIG. 2 is a diagram exemplarily showing a first Nyquist plot constructed by a diagnostic model configuration unit equipped in the battery diagnostic device of FIG. 1.

[0021] Figure 3 is a diagram exemplifying the types of decision points that constitute the shape of the first Nyquist plot.

[0022] FIG. 4 is a drawing exemplarily showing the determination of similarity in the graph trends of the first Nyquist plot and the second Nyquist plot by the measurement data reliability verification unit of the battery failure diagnosis unit equipped in the battery diagnosis device of FIG. 1.

[0023] FIG. 5 is a drawing showing an example of a battery failure type diagnosis using a Nyquist plot by a primary failure diagnosis unit and a secondary failure diagnosis unit of a battery failure diagnosis unit equipped in the battery diagnosis device of FIG. 1.

[0024] FIG. 6 is a drawing showing raw values ​​of judgment points on a first Nyquist plot for battery failure diagnosis by a first failure diagnosis unit of a battery failure diagnosis unit equipped in a battery diagnosis device of FIG. 1 and battery failure diagnosis by a raw data diagnosis unit of a second failure diagnosis unit.

[0025] FIG. 7 is a drawing showing, by way of example, judgment parameter values ​​derived by constructing an equivalent circuit model based on the first Nyquist plot for battery failure diagnosis in the equivalent circuit model diagnosis unit of the second failure diagnosis unit of the battery failure diagnosis unit equipped in the battery diagnosis device of FIG. 1.

[0026] Figure 8 is a diagram illustrating an equivalent circuit model constructed by an equivalent circuit model diagnosis unit.

[0027] Figure 9 is a diagram showing battery failure judgment conditions and battery diagnosis results by the first failure diagnosis unit and the second failure diagnosis unit as examples.

[0028] Fig. 10 is a flowchart illustrating a battery diagnosis method according to one embodiment of the present invention.

[0029] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the present invention, and the present invention is defined solely by the scope of the claims.

[0030] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0031] Throughout the specification, the same reference numerals refer to the same elements, and the term "and / or" includes each and every combination of the elements mentioned. Although terms such as "first," "second," etc. are used to describe various elements, these elements are not limited by these terms. These terms are used only to distinguish one element from another. Therefore, it should be understood that a first element mentioned below may also be a second element within the technical scope of the present invention.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0033] Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention, and it should be understood that there may be various equivalents and modified examples that can replace them at the time of this application.

[0034] In describing the present invention, a "battery" may be a capacitor or secondary battery that stores power by charging. Furthermore, the battery may include at least one of a battery pack comprising a plurality of battery modules, at least one battery module within the battery pack, a battery module comprising a plurality of battery cells, at least one battery cell within the battery module, a representative module representing a plurality of battery modules, and a representative cell representing a plurality of battery cells.

[0035] FIG. 1 is a drawing showing a battery diagnosis device (10) according to one embodiment of the present invention, FIG. 2 is a drawing showing an example of a first Nyquist plot configured by a diagnosis model configuration unit (100) equipped in the battery diagnosis device (10) of FIG. 1, and FIG. 3 is a drawing showing an example of the types of judgment points that constitute the shape of the first Nyquist plot.

[0036] Referring to FIGS. 1 to 3, a battery diagnostic device (10) according to one embodiment of the present invention may include a diagnostic model configuration unit (100) and a battery failure diagnostic unit (200).

[0037] The above diagnostic model configuration unit (100) can configure a first Nyquist plot in which judgment points forming the shape of a Nyquist plot are displayed using first AC impedance data, which is reference AC impedance data measured for a first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy (EIS). At this time, the Nyquist plot may include a portion of a semicircular shape.

[0038] As an example, the diagnostic model configuration unit (100) can apply an input signal while modulating the frequency to the first battery, measure the output signal, and calculate a reference AC impedance according to the frequency from the input signal and the output signal. For example, the frequency modulation range of the input signal can be 0.1 Hz to 4000 Hz.

[0039] In addition, the diagnostic model configuration unit (100) can separate the measured first AC impedance data by frequency. In addition, the diagnostic model configuration unit (100) can obtain the real component (Zre) and the imaginary component (Zimg) of the first AC impedance data and configure them into a first Nyquist plot. At this time, the real component of the first AC impedance data represents the resistance value of the first AC impedance data and can configure the horizontal axis of the first Nyquist plot. In addition, the imaginary component of the first AC impedance data represents at least one of the inductance value and the capacitance value of the first AC impedance data, and the negative value (-Zimg) of the imaginary component of the first AC impedance data can configure the vertical axis of the first Nyquist plot.

[0040] Specifically, the diagnostic model configuration unit (100) may be configured to display the judgment points on the first Nyquist plot as, as shown in FIGS. 2 and 3, the starting point (ZO) of the semicircle of the first Nyquist plot, the ending point (Zmin) of the semicircle of the first Nyquist plot, the point (Zmax) where the negative value (-Zimg) of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot, the first measurement point (Zstart) of the first AC impedance data, and the last measurement point (Zend) of the first AC impedance data.

[0041] At this time, the starting point (ZO) of the semicircle of the first Nyquist plot can be set by deriving a point where the imaginary component (Zimg) of the first AC impedance data is 0 through interpolation based on the frequency at which the sign of the imaginary component (Zimg) of the first AC impedance data changes and the frequency immediately before the sign change of the imaginary component (Zimg) of the first AC impedance data.

[0042] In addition, the point (Zmax) at which the negative value (-Zimg) of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot can be set by deriving the point at which the imaginary component (Zimg) of the first AC impedance data starts to decrease and then increase in the frequency range after the starting point (ZO) of the semicircle of the first Nyquist plot.

[0043] In addition, the semicircle end point (Zmin) of the first Nyquist plot can be set by deriving a point where the imaginary component (Zimg) of the first AC impedance data begins to increase and then decrease in the frequency range after the point (Zmax) where the negative value (-Zimg) of the imaginary component of the first AC impedance data in the semicircle of the first Nyquist plot is maximum.

[0044] The purpose of constructing the first Nyquist plot by focusing on the judgment points that form the shape of the Nyquist plot is to precisely verify the defect of the battery by comparing it with the Nyquist plot derived from the battery to be diagnosed as defective by focusing on the judgment points.

[0045] The above battery failure diagnosis unit (200) can construct a second Nyquist plot in which measurement points forming the shape of a Nyquist plot are displayed using second AC impedance data measured at different frequencies for a second battery, which is a battery to be diagnosed as a failure, using electrochemical impedance spectroscopy. As an example, the second battery, which is a battery to be diagnosed as a failure, may have the same specifications as the first battery, which is a normal battery.

[0046] As an example, the battery failure diagnosis unit (200) can apply an input signal to a second battery while modulating the frequency, measure the output signal, and calculate a second AC impedance according to the frequency from the input signal and the output signal. For example, the frequency modulation range of the input signal can be 0.1 Hz to 4000 Hz.

[0047] In addition, the battery failure diagnosis unit (200) can separate the measured second AC impedance data by frequency. In addition, the battery failure diagnosis unit (200) can obtain the real component (Zre) and the imaginary component (Zimg) of the second AC impedance data and configure them into a second Nyquist plot. At this time, the real component of the second AC impedance data represents the resistance value of the second AC impedance data and can configure the horizontal axis of the second Nyquist plot. In addition, the imaginary component of the second AC impedance data represents at least one of the inductance value or the capacitance value of the second AC impedance data, and the negative value (-Zimg) of the imaginary component of the second AC impedance data can configure the vertical axis of the second Nyquist plot.

[0048] Here, the configuration of the second Nyquist plot can be performed by the measurement data configuration unit (210) of the battery failure diagnosis unit (200).

[0049] And, similarly to the judgment point configuration described above, the measurement data configuration unit (210) may be configured to display the measurement points on the second Nyquist plot as a starting point (Z0) of the semicircle of the second Nyquist plot, a ending point (Zmin) of the semicircle of the second Nyquist plot, a point (Zmax) where the negative value (-Zimg) of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot, a first measurement point (Zstart) of the second AC impedance data, and a last measurement point (Zend) of the second AC impedance data.

[0050] In addition, the battery failure diagnosis unit (200) can be configured to diagnose a failure of the second battery by comparing the first Nyquist plot and the second Nyquist plot.

[0051] That is, the battery failure diagnosis unit (200) can be configured to diagnose a failure of the second battery through a comparison of the overall shape, the graph increase / decrease trend of the first Nyquist plot and the second Nyquist plot, etc.

[0052] Meanwhile, the detailed configuration of the battery defect diagnosis unit (200) that diagnoses the defect of the second battery, which is the target battery for defect diagnosis, will be examined in detail in the related description that follows.

[0053] FIG. 4 is a drawing exemplarily showing the judgment of similarity of the graph trends of the first Nyquist plot and the second Nyquist plot by the measurement data reliability verification unit (220) of the battery failure diagnosis unit (200) equipped in the battery diagnosis device (10) of FIG. 1.

[0054] Referring to FIGS. 1 and 4, the battery failure diagnosis unit (200) may further include a measurement data reliability verification unit (220).

[0055] The above measurement data reliability verification unit (220) may be configured to determine the similarity of the graph trends of the first Nyquist plot and the second Nyquist plot. In this case, the dotted line graph in FIG. 4 may be the first Nyquist plot, and the graph in the form of repeated 'X' dots may be the second Nyquist plot.

[0056] Specifically, the measurement data reliability verification unit (220) can perform a verification on whether the imaginary component (Zimg) of the second AC impedance data continuously decreases between the starting point (Z0) of the semicircle of the second Nyquist plot on the second Nyquist plot and the point where the negative value (-Zimg) of the imaginary component of the second AC impedance data in the semicircle of the second Nyquist plot is maximum (first verification).

[0057] In addition, the measurement data reliability verification unit (220) can perform a verification on the second Nyquist plot whether the imaginary component (Zimg) of the second AC impedance data continuously increases between the point where the negative value (-Zimg) of the imaginary component of the second AC impedance data in the semicircle of the second Nyquist plot is maximum and the semicircle termination point (Zmin) of the second Nyquist plot (second verification).

[0058] In addition, the measurement data reliability verification unit (220) can perform a check to see whether the imaginary component (Zimg) of the second AC impedance data continuously decreases between the semicircle end point (Zmin) of the second Nyquist plot and the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot (third verification).

[0059] Here, the first to third verifications may be to determine whether the increase / decrease trend of the graph of the first Nyquist plot and the increase / decrease trend of the graph of the second Nyquist plot are similar based on each judgment point of the first Nyquist plot, as in FIG. 4.

[0060] At this time, the measurement data reliability verification unit (220) can perform at least one of the first to third verifications to determine the similarity of the increase and decrease trends of the graphs of the first Nyquist plot and the second Nyquist plot. By verifying the reliability of the second AC impedance data measured for the second battery, which is the target battery for defect diagnosis, in this way, the accuracy of the precise diagnosis of the defect of the second battery by the first defect diagnosis unit (230) and the second defect diagnosis unit (240) described below can be increased.

[0061] FIG. 5 is a drawing showing an example of a battery failure type diagnosis using a Nyquist plot by the primary failure diagnosis unit (230) and the secondary failure diagnosis unit (240) of the battery failure diagnosis unit (200) equipped in the battery diagnosis device (10) of FIG. 1.

[0062] Referring to FIGS. 1 and 5, the battery failure diagnosis unit (220) may further include a primary failure diagnosis unit (230).

[0063] The above primary failure diagnosis unit (230) may be configured to primarily diagnose a failure of the second battery by performing at least one of a comparison between the first measurement point (Zstart) of the first AC impedance data on the first Nyquist plot and the first measurement point (Zstart) of the second AC impedance data on the second Nyquist plot and a comparison between the last measurement point (Zend) of the first AC impedance data on the first Nyquist plot and the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot.

[0064] That is, the first defect diagnosis unit (230) can perform at least one of the following among the judgment points on the first Nyquist plot: a comparison between the first measurement point (Zstart) of the first AC impedance data on the first Nyquist plot and the first measurement point (Zstart) of the second AC impedance data on the second Nyquist plot, and a comparison between the last measurement point (Zend) of the first AC impedance data on the first Nyquist plot and the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot.

[0065] According to this configuration, the first failure diagnosis unit (230) can determine whether the overall shape of the first Nyquist plot and the overall shape of the second Nyquist plot are similar by performing at least one of a comparison between the start point of the first Nyquist plot (corresponding to the first measurement point (Zstart) of the first AC impedance data) and the start point of the second Nyquist plot (corresponding to the first measurement point (Zstart) of the second AC impedance data) and a comparison between the end point of the first Nyquist plot (the last measurement point (Zend) of the first AC impedance data) and the end point of the second Nyquist plot (the last measurement point (Zend) of the second AC impedance data).

[0066] For example, as in FIG. 5, a second battery failure diagnosis case such as (1) measurement data error, (2) over-discharge, or (3) serious battery damage can be determined by performing at least one of a comparison between the first measurement point (Zstart) of the first AC impedance data on the first Nyquist plot and the first measurement point (Zstart) of the second AC impedance data on the second Nyquist plot by the first failure diagnosis unit (230) and a comparison between the last measurement point (Zend) of the first AC impedance data on the first Nyquist plot and the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot.

[0067] In this way, the primary defect diagnosis unit (230) can primarily diagnose the defect of the second battery by judging the overall shape similarity of the first Nyquist plot and the second Nyquist plot.

[0068] FIG. 6 is a drawing showing raw values ​​of judgment points on a first Nyquist plot for battery failure diagnosis by a first failure diagnosis unit (230) of a battery failure diagnosis unit (200) equipped in a battery diagnosis device (10) of FIG. 1 and for battery failure diagnosis by a raw data diagnosis unit (242) of a second failure diagnosis unit (240).

[0069] At this time, in FIG. 6, the raw values ​​of the judgment points on the first Nyquist plot can be displayed by SOC (state of charge) of the first battery at room temperature (25°C).

[0070] Referring to FIG. 1 and FIG. 6, the battery failure diagnosis unit (200) may further include a secondary failure diagnosis unit (240).

[0071] The secondary failure diagnosis unit (240) may be configured to secondarily diagnose a failure of the second battery by performing at least one of a comparison between a semicircle starting point (ZO) of the first Nyquist plot and a semicircle starting point (ZO) of the second Nyquist plot, a comparison between a semicircle ending point (Zmin) of the first Nyquist plot and a semicircle ending point (Zmin) of the second Nyquist plot, and a comparison between a point (Zmax) in the semicircle of the first Nyquist plot where the negative value (-Zimg) of the imaginary component of the first AC impedance data is maximum and a point (Zmax) in the semicircle of the second Nyquist plot where the negative value (-Zimg) of the imaginary component of the second AC impedance data is maximum.

[0072] That is, the secondary failure diagnosis unit (240) can diagnose the failure of the second battery more precisely in a secondary manner through a detailed comparison of the judgment points in the semicircle area of ​​the first Nyquist plot (the semicircle starting point (ZO) of the first Nyquist plot, the semicircle ending point (Zmin) of the first Nyquist plot, the point (Zmax) where the negative value (-Zimg) of the imaginary component of the first AC impedance data in the semicircle of the first Nyquist plot is maximum) and the judgment points in the semicircle area of ​​the second Nyquist plot (the semicircle starting point (ZO) of the second Nyquist plot, the semicircle ending point (Zmin) of the second Nyquist plot, the point (Zmax) where the negative value (-Zimg) of the imaginary component of the second AC impedance data in the semicircle of the second Nyquist plot is maximum).

[0073] By means of this secondary defect diagnosis unit (240), as shown in Fig. 5, the secondary battery defect diagnosis cases such as (1) measurement data error, (2) over-discharge, (3) serious battery damage, (4) contact resistance abnormality, (5) micro-short circuit inside the battery, and (6) micro-interface abnormality of the battery electrode can be determined. At this time, the defect diagnosis cases of the secondary battery determined by the secondary defect diagnosis unit (240) may be more diverse than the defect diagnosis cases of the secondary battery determined by the primary defect diagnosis unit (230).

[0074] Here, the secondary defect diagnosis unit (240) may include a raw data diagnosis unit (242).

[0075] The above raw data diagnosis unit (242) can secondarily diagnose a defect in the second battery based on at least one of the starting point (ZO) of the semicircle of the first Nyquist plot, the ending point (Zmin) of the semicircle of the first Nyquist plot, and the point (Zmax) where the negative value (-Zimg) of the imaginary component of the first AC impedance data in the semicircle of the first Nyquist plot is maximum.

[0076] That is, the raw data diagnosis unit (242) may be configured to secondarily diagnose a defect in the second battery by performing at least one of a comparison between a semicircle starting point (ZO) of the first Nyquist plot and a semicircle starting point (ZO) of the second Nyquist plot, a comparison between a semicircle ending point (Zmin) of the first Nyquist plot and a semicircle ending point (Zmin) of the second Nyquist plot, and a comparison between a point (Zmax) in the semicircle of the first Nyquist plot where the negative value (-Zimg) of the imaginary component of the first AC impedance data is maximum and a point (Zmax) where the negative value (-Zimg) of the imaginary component of the second AC impedance data is maximum.

[0077] FIG. 7 is a drawing showing an example of judgment parameter values ​​derived by constructing an equivalent circuit model (ECM) based on a first Nyquist plot for battery failure diagnosis by an equivalent circuit model diagnosis unit (244) of a secondary failure diagnosis unit (240) of a battery failure diagnosis unit (200) equipped in a battery diagnosis device (10) of FIG. 1, and FIG. 8 is a drawing showing an example of an equivalent circuit model constructed by an equivalent circuit model diagnosis unit (244). However, the equivalent circuit model is not limited to the example shown in FIG. 8.

[0078] At this time, in Fig. 7, the judgment parameter values ​​derived by constructing an equivalent circuit model based on the first Nyquist plot can be displayed by SOC (state of charge) of the first battery at room temperature (25°C).

[0079] Referring to FIG. 1, FIG. 7 and FIG. 8, the secondary defect diagnosis unit (240) may further include an equivalent circuit model diagnosis unit (244).

[0080] The above equivalent circuit model diagnosis unit (244) can be configured to secondarily diagnose a defect in the second battery by comparing the judgment parameter values ​​derived by constructing an equivalent circuit model based on the first Nyquist plot with the measurement parameter values ​​derived by constructing an equivalent circuit model based on the second Nyquist plot.

[0081] In one embodiment, when constructing an equivalent circuit model based on the first Nyquist plot, the equivalent circuit model diagnosis unit (244) can construct an equivalent circuit model based on inductance (L1), Stray resistance (Rst), electrolyte resistance (Rs), film resistance (Rf), film capacitance (Cf), electric double layer capacitance (Cdl=CPE), charge transfer resistance (Rct), and capacitance (CPE1) considering diffusion phenomenon within the battery active material, as shown in FIG. 8.

[0082] And the equivalent circuit model diagnosis unit (244) can construct an equivalent circuit model according to the CNLS (Complex Nonlinear Least Square) fitting method using the first Nyquist plot as an example and derive judgment parameters (e.g., Rs, Rp, CPE-T, CPE-P).

[0083] At this time, Rs can correspond to the value of the real component (Zre) of the first AC impedance data at the semicircle starting point (ZO) of the first Nyquist plot.

[0084] Additionally, Rp may correspond to the value of the point (Zmax) where the negative value (-Zimg) of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot.

[0085] Additionally, CPE-T is a parameter indicating the size of CPE, and may correspond to the value of the real component (Zre) of the first AC impedance data at the last measurement point (Zend) of the first AC impedance data on the first Nyquist plot.

[0086] Additionally, CPE-P is a parameter indicating whether CPE is closer to a resistor or a capacitor, and may correspond to the value of the imaginary component (Zimg) of the first AC impedance data at the last measurement point (Zend) of the first AC impedance data on the first Nyquist plot.

[0087] In addition, the equivalent circuit model diagnosis unit (244) can construct an equivalent circuit model according to the CNLS fitting method using, for example, the second Nyquist plot to derive measurement parameters (e.g., Rs, Rp, CPE-T, CPE-P).

[0088] At this time, Rs can correspond to the value of the real component (Zre) of the second AC impedance data at the semicircle starting point (ZO) of the second Nyquist plot.

[0089] Additionally, Rp may correspond to the value of the point (Zmax) where the negative value (-Zimg) of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot.

[0090] Additionally, CPE-T is a parameter indicating the size of CPE, and may correspond to the value of the real component (Zre) of the second AC impedance data at the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot.

[0091] Additionally, CPE-P is a parameter indicating whether CPE is closer to a resistor or a capacitor, and may correspond to the value of the imaginary component (Zimg) of the second AC impedance data at the last measurement point (Zend) of the second AC impedance data on the second Nyquist plot.

[0092] And, the equivalent circuit model diagnosis unit (244) can be configured to secondarily diagnose a defect in the second battery by comparing the judgment parameter values ​​derived by constructing an equivalent circuit model based on the first Nyquist plot as described above with the measurement parameter values ​​derived by constructing an equivalent circuit model based on the second Nyquist plot.

[0093] According to this implementation configuration, after constructing an equivalent circuit model for the first battery, which is a normal battery, and the second battery, which is a battery to be diagnosed as defective, the accuracy of diagnosing a battery defect can be further improved by comparing the simplified judgment parameter values ​​with the measurement parameters.

[0094] Figure 9 is a drawing showing battery failure judgment conditions and battery diagnosis results by the first failure diagnosis unit (230) and the second failure diagnosis unit (240) as examples.

[0095] Referring to FIG. 9, the first defect diagnosis unit (230) can diagnose the defect type of the second battery as “serious battery damage” when, for example, it is determined that the value at the first measurement point (Zimg_start) of the imaginary component of the second AC impedance data on the second Nyquist plot is less than 0, or the value at the first measurement point (Zre_start) of the real component of the second AC impedance data on the second Nyquist plot is greater than three times the value at the first measurement point (Zre_start_std) of the real component of the first AC impedance data on the first Nyquist plot.

[0096] In addition, if the first defect diagnosis unit (230) determines that the value at the last measurement point (Zimg_end) of the imaginary component of the second AC impedance data on the second Nyquist plot is greater than three times the value at the last measurement point (Zimg_end_std) of the imaginary component of the first AC impedance data on the first Nyquist plot, the first defect diagnosis unit (230) can diagnose the defect type of the second battery as “over-discharge.”

[0097] In addition, the raw data diagnosis unit (242) may diagnose the failure type of the second battery as “serious battery damage” if, for example, it is determined that the value of the real component (Zre_0) of the second AC impedance data at the starting point of the semicircle of the second Nyquist plot is greater than 2.5 times the value of the real component (Zre_0_std) of the first AC impedance data at the starting point of the semicircle of the first Nyquist plot, or the value of the point (Zimg_max) where the negative value of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot is greater than twice the value of the point (Zimg_max_std) where the negative value of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot.

[0098] In addition, the equivalent circuit model diagnosis unit (244) may diagnose the failure type of the second battery as “serious battery damage” when, for example, the value of Rs, which is one of the measured parameter values ​​derived by constructing the equivalent circuit model based on the second Nyquist plot, is greater than 2.5 times the value of Rs_std, which is one of the judgment parameter values ​​derived by constructing the equivalent circuit model based on the first Nyquist plot, or the value of Rp, which is one of the measured parameter values ​​derived by constructing the equivalent circuit model based on the second Nyquist plot, is greater than twice the value of Rp_std, which is one of the judgment parameter values ​​derived by constructing the equivalent circuit model based on the first Nyquist plot.

[0099] As described above, referring to the configuration and FIG. 9, various defect states of the battery can be diagnosed more precisely through the primary defect diagnosis unit (230) and the secondary defect diagnosis unit (230).

[0100] According to the battery diagnosis device (10) of the present invention, a first Nyquist plot in which judgment points constituting the shape of a Nyquist plot are displayed using first AC impedance data measured for a first battery, which is a normal battery, and a second Nyquist plot in which measurement points constituting the shape of a Nyquist plot are displayed using second AC impedance data measured for a second battery, which is a battery to be diagnosed as defective, are used, thereby accurately measuring the defect of the second battery through a precise diagnosis using a plurality of comparison methods (e.g., comparison according to a measurement data reliability verification unit (220), a first defect diagnosis unit (230), and a second defect diagnosis unit (240).

[0101] Fig. 10 is a flowchart illustrating a battery diagnosis method according to one embodiment of the present invention.

[0102] Referring to FIG. 10, a battery diagnosis method according to one embodiment of the present invention includes the following steps S1 and S2.

[0103] In the above step S1, a first Nyquist plot is constructed using the first AC impedance data, which is the reference AC impedance data measured for the first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy, and the judgment points forming the shape of the Nyquist plot are displayed. At this time, the above step S1 can be performed by the diagnostic model construction unit (100) described above.

[0104] In the above step S2, a second Nyquist plot is constructed by using second AC impedance data measured at different frequencies for the second battery, which is a battery to be diagnosed as defective, using electrochemical impedance spectroscopy, and measurement points forming the shape of the Nyquist plot are displayed, and the first Nyquist plot and the second Nyquist plot are compared to diagnose the defect of the second battery. At this time, the step S2 may be performed by the battery defect diagnosis unit (200) described above.

[0105] As described above, although the present invention has been described by limited embodiments and drawings, the present invention is not limited thereto, and various modifications and variations are possible by a person having ordinary skill in the art to which the present invention pertains within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below.

[0106] Meanwhile, although terms indicating directions such as up, down, left, right, front, and back are used in the present invention, it is obvious to those skilled in the art that these terms are only for convenience of explanation and may vary depending on the location of the target object or the location of the observer.

[0107] [Explanation of symbols]

[0108] 10: Battery diagnostic device

[0109] 100: Diagnostic model component

[0110] 200: Battery failure diagnosis section

[0111] 210: Measurement data composition section

[0112] 220: Measurement Data Reliability Verification Department

[0113] 230: Primary Defect Diagnosis Department

[0114] 240: Secondary Defect Diagnosis Department

[0115] 242: Raw Data Diagnostics Department

[0116] 244: Equivalent circuit model diagnostic section

Claims

1. A diagnostic model component that constructs a first Nyquist plot, in which judgment points forming the shape of a Nyquist plot are displayed, using first AC impedance data, which is reference AC impedance data measured for a first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy (EIS); and A battery diagnosis device characterized by including a battery failure diagnosis unit configured to construct a second Nyquist plot in which measurement points forming the shape of a Nyquist plot are displayed using second AC impedance data measured for a second battery, which is a battery to be diagnosed as a failure, at different frequencies using the electrochemical impedance spectroscopy, and to diagnose a failure of the second battery by comparing the first Nyquist plot and the second Nyquist plot.

2. In paragraph 1, The above diagnostic model component is: The above judgment points on the first Nyquist plot, A battery diagnostic device characterized in that it is configured to display a starting point of the semicircle of the first Nyquist plot, an ending point of the semicircle of the first Nyquist plot, a point where the negative value of the imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot, a first measurement point of the first AC impedance data, and a last measurement point of the first AC impedance data.

3. In paragraph 2, The above battery failure diagnosis unit, a measurement data configuration unit configured to construct the second Nyquist plot; and A battery diagnosis device characterized by including a measurement data reliability verification unit configured to determine the similarity of the graph trends of the first Nyquist plot and the second Nyquist plot.

4. In paragraph 3, The above measurement data configuration section is, The measurement points on the second Nyquist plot, A battery diagnostic device characterized in that it is configured to display a starting point of the semicircle of the second Nyquist plot, an ending point of the semicircle of the second Nyquist plot, a point where the negative value of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot, a first measurement point of the second AC impedance data, and a last measurement point of the second AC impedance data.

5. In paragraph 4, The above measurement data reliability verification unit is, On the second Nyquist plot, between the starting point of the semicircle of the second Nyquist plot and the point where the negative value of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot, checking whether the imaginary component of the second AC impedance data continuously decreases; On the second Nyquist plot, between the point where the negative value of the imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot and the end point of the semicircle of the second Nyquist plot, whether the imaginary component of the second AC impedance data continuously increases and A battery diagnostic device characterized in that it is configured to perform at least one of checking whether the imaginary component of the second AC impedance data continuously decreases between the semicircle end point of the second Nyquist plot and the last measurement point of the second AC impedance data on the second Nyquist plot.

6. In paragraph 4, The above battery failure diagnosis unit, A battery diagnosis device characterized in that it further includes a primary failure diagnosis unit configured to primarily diagnose a failure of the second battery by performing at least one of a comparison between a first measurement point of the first AC impedance data on the first Nyquist plot and a first measurement point of the second AC impedance data on the second Nyquist plot and a comparison between a last measurement point of the first AC impedance data on the first Nyquist plot and a last measurement point of the second AC impedance data on the second Nyquist plot.

7. In paragraph 4, The above battery failure diagnosis unit, A battery diagnosis device further comprising a secondary failure diagnosis unit configured to secondarily diagnose a failure of the second battery by performing at least one of a comparison between a starting point of a semicircle of the first Nyquist plot and a starting point of a semicircle of the second Nyquist plot, a comparison between an ending point of a semicircle of the first Nyquist plot and a ending point of a semicircle of the second Nyquist plot, and a comparison between a point where the negative value of an imaginary component of the first AC impedance data is maximum in the semicircle of the first Nyquist plot and a point where the negative value of an imaginary component of the second AC impedance data is maximum in the semicircle of the second Nyquist plot.

8. In paragraph 7, The above secondary defect diagnosis section, A raw data diagnostic unit configured to secondarily diagnose a defect in the second battery based on at least one of a starting point of the semicircle of the first Nyquist plot, an ending point of the semicircle of the first Nyquist plot, and a point where the negative value of the imaginary component of the first AC impedance data in the semicircle of the first Nyquist plot is maximum; and A battery diagnosis device further comprising an equivalent circuit model diagnosis unit configured to secondarily diagnose a defect in the second battery by comparing the judgment parameter values ​​derived by constructing an equivalent circuit model based on the first Nyquist plot with the measurement parameter values ​​derived by constructing an equivalent circuit model based on the second Nyquist plot.

9. In a battery diagnosis method performed by a battery diagnosis device, A step of constructing a first Nyquist plot, in which decision points forming the shape of the Nyquist plot are indicated using first AC impedance data, which are reference AC impedance data measured for a first battery, which is a normal battery, at different frequencies using electrochemical impedance spectroscopy; and A battery diagnosis method characterized by comprising the step of constructing a second Nyquist plot in which measurement points forming the shape of a Nyquist plot are displayed using second AC impedance data measured for a second battery, which is a battery to be diagnosed as defective, at different frequencies using the electrochemical impedance spectroscopy, and diagnosing a defect in the second battery by comparing the first Nyquist plot and the second Nyquist plot.

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