Battery diagnosis device and method and battery pack

Abstract

To present a mechanism for diagnosing, in advance, an abnormality of a battery cell, such as an internal short circuit of the cell caused by lithium salt precipitation that may occur in a lithium-ion battery.SOLUTION: A battery diagnosis device and method are disclosed. A battery diagnosis device includes a configuration for diagnosing an abnormality of a battery cell in a manner of analyzing a change in behavior of a cell voltage change rate that appears when the battery cell is discharged in a state in which a SOC (state of charge) of the battery cell has been formed as a predefined reference SOC.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a technique for diagnosing an abnormality in a battery. [Background technology]

[0002] Unlike primary batteries, which cannot be recharged, secondary batteries are batteries that can be charged and discharged. Low-capacity secondary batteries are used in small, portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and video cameras, while high-capacity secondary batteries are widely used as motor drive power sources and energy storage batteries for hybrid and electric vehicles. Such secondary batteries (i.e., battery cells) include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, a case that houses the electrode assembly, and electrode terminals that are electrically connected to the electrode assembly. Charging and discharging of the battery cell are performed by injecting an electrolyte into the battery cell case, which causes an electrochemical reaction between the positive electrode, negative electrode, and electrolyte solution. Battery cell cases can be embodied in various shapes, such as cylindrical or rectangular, depending on the application of the battery cell.

[0003] In battery cells, internal short circuits can occur when the separator loses its function, causing a short circuit between the positive and negative electrodes inside the battery cell. Internal short circuits in battery cells can occur due to deformation caused by external impact, metallic foreign matter introduced during the manufacturing process, or the formation of lithium or copper dendrites due to electrochemical reactions. Such internal short circuits in battery cells can lead to safety issues such as thermal runaway.

[0004] Furthermore, secondary batteries applied to large-capacity systems such as electric vehicles or energy storage systems (ESS) are required to have long life, high output characteristics, and safety due to the characteristics of the large-capacity systems. In particular, in the case of a battery into which abnormal metal foreign matter or scrap-type foreign matter including substrate has entered, lithium salt may grow around the foreign matter entry area, and may penetrate the separator under pressurized conditions where cell swelling is restricted by the external partition, which may result in a risk of thermal runaway due to an internal short circuit in the battery cell.

[0005] The above information disclosed in the background of the invention is intended to enhance understanding of the background of the invention only, and may therefore include information that does not constitute prior art. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a battery diagnostic device and method, and a battery pack, capable of diagnosing battery cell abnormalities, such as an internal short circuit caused by lithium salt deposition, in advance, which may occur in a lithium ion battery.

[0007] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description of the invention. [Means for solving the problem]

[0008] To solve the above technical problems, a battery diagnostic device according to one embodiment of the present invention includes a processor configured to diagnose an abnormality in a battery cell; and a memory that stores one or more instructions executed by the processor, wherein the processor diagnoses an abnormality in the battery cell by analyzing a behavior of a cell voltage change rate that occurs when the battery cell is discharged in a state where the SOC (State Of Charge) of the battery cell is formed at a predetermined reference SOC. [Effects of the Invention]

[0009] According to the present invention, by diagnosing abnormalities in a battery cell by analyzing the behavior of the cell voltage change rate (i.e., the inflection point of the cell voltage with respect to time) that appears when a battery cell having a predetermined SOC is discharged, it is possible to pre-diagnose abnormalities in the battery cell, such as an internal short circuit in the cell caused by lithium salt or metal dendrites that grow as the charge / discharge cycle progresses, and to effectively eliminate the risk of thermal runaway and fire in the battery cell by performing a discharge operation and cutting off additional charge for the battery cell that is predicted to have an abnormality.

[0010] In addition, according to the present invention, the accuracy of abnormality diagnosis can be improved by diagnosing abnormalities in a battery cell by comprehensively considering the maximum value of the cell voltage change rate over time and the open circuit voltage, along with the inflection point of the cell voltage over time.

[0011] In addition, according to the present invention, abnormalities in battery cells are diagnosed in a stepwise manner through stepwise monitoring of a first parameter defined by the behavior of the cell voltage change rate that appears when the battery cell is discharged and a second parameter defined by the open circuit voltage that appears when the battery cell is discharged, and a discharge operation and a further charge cut-off operation are performed only on battery cells that are finally classified as having an abnormality, thereby making it possible to pre-diagnose abnormalities in battery cells within a range that ensures normal operation of the battery system and eliminate the risk of thermal runaway and fire.

[0012] However, the effects obtained through the present invention are not limited to the above-mentioned effects, and other technical effects not mentioned herein will be clearly understood by those skilled in the art from the following description of the invention. [Brief explanation of the drawings]

[0013] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention to be given later, serve to further understand the technical concept of the present invention. Therefore, the present invention should not be interpreted as being limited to the matters shown in these drawings. [Figure 1] 1 illustrates a prismatic battery according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a prismatic battery according to an embodiment of the present invention; [Figure 3] 1 illustrates a battery module according to an embodiment of the present invention. [Figure 4A] 1 illustrates a battery pack according to an embodiment of the present invention. [Figure 4B] 1 illustrates a battery pack according to an embodiment of the present invention. [Figure 5] 1 is a block diagram illustrating a battery diagnostic device according to an embodiment of the present invention. [Figure 6] 10 illustrates an example of a process of analyzing a behavior of a cell voltage change rate of a battery cell in a battery diagnostic device according to an embodiment of the present invention. [Figure 7] 10 illustrates an example of a process of analyzing a behavior of a cell voltage change rate of a battery cell in a battery diagnostic device according to an embodiment of the present invention. [Figure 8] 1 illustrates a flowchart of a battery diagnostic method according to an embodiment of the present invention. [Figure 9] 1 illustrates a flowchart of a battery diagnostic method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Prior to this, the terms and phrases used in the specification and claims should not be construed as being limited to their ordinary or dictionary meanings. Instead, they should be interpreted as meanings and concepts consistent with the technical concept of the present invention, based on the principle that the inventor can appropriately define the concepts of terms to best describe his or her invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely some of the most preferred embodiments of the present invention and do not fully represent the technical concept of the present invention. Therefore, it should be understood that various equivalents and modifications may exist as of the time of filing this application. Furthermore, as used in this specification, the words "comprise," "include," and / or "comprising," "including," specify the presence of stated shapes, numbers, steps, operations, members, elements, and / or groups thereof, but do not exclude the presence or addition of one or more other shapes, numbers, operations, members, elements, and / or groups. Furthermore, when describing each embodiment of the present invention, the word "may" can include "one or more embodiments of the present invention."

[0015] In order to facilitate understanding of the invention, the accompanying drawings may not be drawn to scale, and the dimensions of some components may be exaggerated. In addition, the same reference numerals may be used to refer to the same components in different embodiments.

[0016] A statement that two comparison objects are "identical" means that they are "substantially identical." Therefore, "substantially identical" can include cases where there is a deviation that is considered to be a low level in the art, for example, a deviation within 5%. Furthermore, uniformity of any parameter in a given region can mean uniformity on average.

[0017] Although terms such as "first" and "second" are used to describe various components, it is understood that these components are not limited by these terms. These terms are merely used to distinguish one component from another, and it is understood that a first component may also be a second component unless otherwise specified.

[0018] Throughout the specification, unless otherwise specified, each element may be singular or plural.

[0019] The placement of an arbitrary structure on the "top (or bottom)" of a component or "above (or below)" a component can mean not only that the arbitrary structure is placed in contact with the upper surface (or lower surface) of the component, but also that other structures may be interposed between the component and the arbitrary structure placed above (or below) the component.

[0020] Furthermore, when a description is made that one component is "coupled," "coupled," or "connected" to another component, it should be understood that the components may be directly coupled, coupled, or connected to each other, but it should also be understood that there may be other components "intervening" between the components, or that the components may be "coupled," "coupled," or "connected" via other components. Furthermore, when it is said that one part is electrically coupled to another part, this includes not only the case where they are directly coupled, but also the case where they are coupled via another element in between.

[0021] Throughout the specification, "A and / or B" means A, or B, or A and B, unless specifically stated to the contrary. That is, "and / or" includes all or any combination of the listed items. "C through D" means at least C and at most D, unless specifically stated to the contrary.

[0022] 1. Battery structure Before describing this embodiment in detail, the structure of the battery that is the target of the abnormality diagnosis in this embodiment will be generally described.

[0023] [Rectangular battery] FIG. 1 is a perspective view illustrating a secondary battery applied to this embodiment, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 (although the same symbols as in other drawings may be used in FIGS. 1 and 2, it is understood that the symbols used in FIGS. 1 and 2 are used interchangeably within FIGS. 1 and 2).

[0024] Referring to Figures 1 and 2, the secondary battery C (secondary battery cell) according to this embodiment may include at least one electrode assembly 10 wound between a positive electrode 11 and a negative electrode 12 with a separator 13, which is an insulator, interposed therebetween, a case 23 in which the electrode assembly 10 is housed, and a cap assembly 30 coupled to the opening of the case 23.

[0025] The secondary battery C according to this embodiment is a lithium ion secondary battery having a rectangular shape, but is not limited thereto and may be applied to various types of batteries such as a lithium polymer battery or a cylindrical battery.

[0026] The positive electrode 11 and the negative electrode 12 may include a coated portion, which is an area where an active material is applied to a current collector formed of a thin metal foil, and a plain portion 11a, 12a, which is an area where the active material is not coated.

[0027] The positive electrode 11 and the negative electrode 12 are wound up with an insulating separator 13 interposed therebetween. However, this embodiment is not limited to this, and the electrode assembly 10 may have a structure in which positive electrodes and negative electrodes made of multiple sheets are alternately stacked with separators sandwiched between them.

[0028] The case 23 forms the overall appearance of the secondary battery C and may be made of a conductive metal such as aluminum, an aluminum alloy, or nickel-plated steel. The case 23 may also provide a space in which the electrode assembly 10 is housed.

[0029] The cap assembly 30 may include a cap plate 31 that covers the opening of the case 23, and the case 23 and the cap plate 31 may be made of a conductive material. Here, the positive and negative electrode terminals 21 and 22 electrically connected to the positive electrode 11 or the negative electrode 12 may be installed to penetrate the cap plate 31 and protrude outward.

[0030] In addition, the outer circumferential surfaces of the upper posts of the positive and negative terminals 21, 22 protruding outward from the cap plate 31 may be threaded and fixed to the cap plate 31 with nuts.

[0031] However, this embodiment is not limited thereto, and the positive and negative terminals 21 and 22 may be riveted together using a rivet structure, or may be welded to the cap plate 31 .

[0032] In addition, the cap plate 31 may be made of a thin plate and may be coupled to the opening of the case 23. The cap plate 31 may be formed with an electrolyte injection port 32 in which a sealing plug 33 may be installed, and may be provided with a vent portion 34 having a notch 34a.

[0033] The positive and negative electrode terminals 21, 22 may be electrically connected to current collectors including first and second current collectors 40, 50 (hereinafter referred to as positive and negative electrode current collectors) joined by welding to the positive electrode uncoated region 11a or the negative electrode uncoated region 12a. For example, the positive and negative electrode terminals 21, 22 may be connected to the positive and negative electrode current collectors 40, 50 by welding. However, this embodiment is not limited thereto, and the positive and negative electrode terminals 21, 22 and the positive and negative electrode current collectors 40, 50 may be integrally connected to each other.

[0034] An insulating member may be installed between the electrode assembly 10 and the cap plate 31. Here, the insulating member may include first and second lower insulating members 60 and 70, and the first and second lower insulating members 60 and 70 may be installed between the electrode assembly 10 and the cap plate 31, respectively.

[0035] Furthermore, according to this embodiment, one end of a separating member that can be installed to face one side of the electrode assembly 10 may be installed between the insulating member and the positive or negative terminal 21 or 22 .

[0036] Here, the separating members may include first and second separating members 80,90.

[0037] Therefore, one ends of first and second separators 80 and 90 that can be installed to face one side of the electrode assembly 10 can be installed between the first and second lower insulating members 60 and 70 and the positive and negative terminals 21 and 22.

[0038] Finally, the positive and negative electrode terminals 21, 22 welded to the positive and negative electrode current collectors 40, 50 can be coupled to one end of the first and second lower insulating members 60, 70 and the first and second separating members 80, 90.

[0039] [Battery module] FIG. 3 is a perspective view showing a battery module according to one embodiment of the present invention (although FIG. 3 may show the same symbols as other drawings, it is clear that the symbols shown in FIG. 3 are used exclusively within FIG. 3).

[0040] 3, a battery module M according to this embodiment includes a plurality of battery cells C having electrodes 11 and 12 and arranged in one direction, a connection tab 20 connecting a battery cell 10a to an adjacent battery cell 10b, and a protection circuit module 30 having one end connected to the connection tab 20. The protection circuit module 30 may be a battery management system (BMS). The connection tab 20 includes a body portion 22 that contacts the electrodes 11 and 12 between the adjacent battery cells 10a and 10b, and an extension portion that extends from the body portion 22 and is connected to the protection circuit module 30. The connection tab 20 may be a bus bar.

[0041] First, a battery cell C may include a battery case and an electrode assembly and electrolyte housed within the battery case. The electrode assembly and electrolyte react electrochemically to generate energy. One side of the battery cell C may include terminals 11 and 12 electrically connected to a connection tab 20 and a vent 13 serving as a passage for discharging gas generated therein. The terminals 11 and 12 of the battery cell C may be a positive terminal 11 and a negative terminal 12 having opposite polarities, and the terminals 11 and 12 of adjacent battery cells 10a and 10b may be electrically connected in series or parallel by a connection tab 20, which will be described below. While the above description exemplifies a series connection, this is not intended to be limiting, and various connection structures may be employed as needed. Furthermore, the number and arrangement of the battery cells are not limited to the structure shown in FIG. 3 and may be modified as needed.

[0042] A plurality of battery cells C may be arranged in one direction such that wide surfaces of the battery cells C face each other, and the arranged plurality of battery cells C may be fixed by housings 61, 62, 63, and 64. The housings 61, 62, 63, and 64 may include a pair of end plates 61 and 62 facing the wide surfaces of the battery cells C, and a side plate 63 and a bottom plate 64 connecting the pair of end plates 61 and 62. The side plate 63 may support the side surfaces of the battery cells C, and the bottom plate 64 may support the bottom surfaces of the battery cells C. In addition, the pair of end plates 61 and 62 may be connected to the side plate 63 and the bottom plate 64 by members such as bolts 65.

[0043] The protection circuit module 30 includes electronic components and protection circuits and may be electrically connected to the connection tabs 20 described below. The protection circuit module 30 includes a first protection circuit module 30a and a second protection circuit module 30b extending at different positions along the direction in which the plurality of battery cells C are arranged. The first protection circuit module 30a and the second protection circuit module 30b may be positioned parallel to each other while being spaced apart by a predetermined distance, and may be electrically connected to the adjacent connection tabs 20. For example, the first protection circuit module 30a may be formed extending from one side of the upper portions of the plurality of battery cells C along the direction in which the plurality of battery cells C are arranged, and the second protection circuit module 30b may be formed extending from the other side of the upper portions of the plurality of battery cells C along the direction in which the plurality of battery cells C are arranged. The second protection circuit module 30b may be positioned parallel to the first protection circuit module 30a while being spaced apart by a predetermined distance across the vent 13. In this way, the two protection circuit modules are arranged side by side and spaced apart in the direction in which the battery cells are arranged, thereby minimizing the area of ​​the PCB (Printed Circuit Board) that constitutes the protection circuit module. By configuring the protection circuit module as two separate protection circuit modules, unnecessary PCM area is minimized. The first protection circuit module 30a and the second protection circuit module 30b may be connected by a conductive connecting member 50. In this case, one side of the connecting member 50 is connected to the first protection circuit module 30a, and the other side is connected to the second protection circuit module 30b, thereby establishing an electrical connection between the two protection circuit modules.

[0044] The connection can be performed by any one of soldering, resistance welding, laser welding, and projection welding.

[0045] The connecting member 50 may be, for example, an electric wire. The connecting member 50 may also be made of an elastic or flexible material. The connecting member 50 may be used to check and manage whether the voltage, temperature, and current of the plurality of battery cells C are normal. That is, information on the voltage, current, temperature, etc. transmitted from the connecting tab adjacent to the first protection circuit module and information on the voltage, current, and temperature transmitted from the connecting tab adjacent to the second protection circuit module may be integrated and managed by the protection circuit module through the connecting member.

[0046] Furthermore, when the battery cell C expands, the elasticity or flexibility of the connecting member 50 absorbs the impact, thereby preventing damage to the first and second protection circuit modules 30a and 30b.

[0047] Furthermore, the shape and structure of the connecting member 50 are not limited to the shape shown in FIG.

[0048] As described above, since the protection circuit module 30 is provided with the first and second protection circuit modules 30a and 30b, the area of ​​the PCB constituting the protection circuit module can be minimized, thereby securing space inside the battery module. This not only simplifies the fastening operation of connecting the connection tab 20 and the protection circuit module 30, but also facilitates repairs when an abnormality is detected in the battery module, thereby improving work efficiency.

[0049] [Battery pack] 4A and 4B are illustrative views showing a battery pack according to a preferred embodiment of the present invention (although the same reference numerals as those in other drawings may be used in FIGS. 4A and 4B, it is clear that the reference numerals used in FIGS. 4A and 4B are used interchangeably within FIGS. 4A and 4B).

[0050] The battery pack P may include a number of battery modules M and a housing H for accommodating the number of battery modules M. For example, the housing H may include first and second housings H1 and H2 coupled in opposing directions with the number of battery modules M interposed therebetween. The number of battery modules M may be electrically connected using bus bars 51, and the number of battery modules M may be electrically connected to each other in a series / parallel or series-parallel mixed mode to obtain a required electrical output.

[0051] 2. Battery diagnostic device Based on the above battery structure, a method for diagnosing abnormalities in battery cells in this embodiment will be described in detail below.

[0052] FIG. 5 is a block diagram of a battery diagnostic device according to an embodiment of the present invention, and FIGS. 6 and 7 are diagrams illustrating a process of analyzing the behavior of the cell voltage change rate of a battery cell in the battery diagnostic device according to an embodiment of the present invention.

[0053] Referring to FIG. 5, the battery diagnostic device of this embodiment may include a memory 100 and a processor 200, and each of the components 100 and 200 may constitute a battery pack together with a battery cell (and a plurality of battery modules each consisting of a plurality of battery cells) that is the target of abnormality diagnosis in this embodiment.

[0054] The memory 100 may store at least one instruction to be executed by the processor 200, which will be described later. The memory 100 may be embodied in a volatile storage medium and / or a non-volatile storage medium, such as a read only memory (ROM) and / or a random access memory (RAM).

[0055] Furthermore, memory 100 may store a plurality of critical data required in the process of diagnosing battery cell abnormalities by processor 200, and the plurality of critical data may include a reference SOC, a reference voltage change rate, a reference OCV change rate, and first to third counting values. As will be described later, the plurality of critical data stored in memory 100 may be used in the process of identifying a group of candidate abnormal cells or finally classifying the abnormal cells. The value of each critical data may be predefined based on the specifications of the battery system and the experimental results of the designer.

[0056] The processor 200, which diagnoses abnormalities in battery cells, may be embodied as a central processing unit (CPU) or a system on chip (SoC), and may run an operation system or application to control multiple hardware or software components connected to the processor 200 and perform various data processing and calculations. The processor 200 may be configured to execute at least one instruction stored in the memory 100 and store the execution result data in the memory 100. Meanwhile, the processor 200 may be embodied as a battery management system (BMS) provided in a battery pack or an MCU (microcontroller unit) within the BMS, and may be configured to sense the current, voltage, open circuit voltage (OCV), and temperature of the battery cells, as is well known. The sensing function of the BMS may support sensing operations for parameters (cell voltage and OCV) that are considered when diagnosing abnormalities in battery cells.

[0057] In this embodiment, the abnormality of the battery cell to be diagnosed may refer to an internal short circuit in the cell due to lithium salt deposition occurring on the surface of the negative electrode of the battery cell. Two embodiments of a method for diagnosing such an abnormality in the battery cell may be presented, and each embodiment will be described below.

[0058] (1) First Example The first embodiment focuses on a configuration that improves the reliability of battery cell abnormality diagnosis by using the behavioral change of the cell voltage change rate of the battery cell as a basic analysis factor and the maximum value of the cell voltage change rate and the change rate of the open circuit voltage of the battery cell as additional analysis factors.

[0059] First, the processor 200 can determine whether the SOC (State Of Charge) of the battery cell is formed at a reference SOC predefined in the memory 100. This embodiment is configured to diagnose an abnormality in the battery cell based on a behavioral change in the cell voltage change rate that occurs when the battery cell self-discharges due to an internal short circuit, and is premised on a state in which the SOC of the battery cell is formed at a predefined reference SOC as a precondition for the battery cell self-discharge.

[0060] If the SOC of the battery cell is set to a reference SOC or lower, the processor 200 may operate to set the SOC of the battery cell to the reference SOC through a predetermined charging method (e.g., CC-CV charging method). In this case, considering that fluctuations in the cell voltage of the battery cell may occur for a predetermined time after charging of the battery cell is completed, the processor 200 may be configured to wait a predefined reference time for the cell voltage of the battery cell to stabilize and then start an abnormality diagnosis operation. The state in which the cell voltage is stabilized may be a state in which the cell voltage fluctuation range of the battery cell falls within a predefined tolerance range, and the reference time required to enter such a cell voltage stabilization state may be a specific value selected according to the specifications of the battery system and predefined in the memory 100 (e.g., 5 hours).

[0061] When the SOC of the battery cell is formed at a reference SOC and the cell voltage enters a stabilized state after a reference time has elapsed, the cause of the change in the cell voltage formed in the battery cell may be identified as an abnormality of the battery cell itself, such as an internal short circuit, and accordingly, the processor 200 may start an abnormality diagnosis operation for the battery cell. In this embodiment, a change in the behavior of the cell voltage change rate of the battery cell is adopted as a basic factor considered for diagnosing an abnormality in the battery cell.

[0062] The cell voltage change rate is the rate of change of the cell voltage of a battery cell with respect to time, i.e., may correspond to the first derivative of the battery cell voltage with respect to time (hereinafter referred to as the first derivative). Also, the behavioral change of the cell voltage change rate may correspond to the second derivative of the battery cell voltage with respect to time. When a battery cell is normal, the cell voltage will exhibit a tendency to decrease due to self-discharge, and assuming the above-described stable state, the decrease rate of the cell voltage (i.e., the cell voltage decrease rate with respect to time) will gradually decrease (i.e., the first derivative will gradually decrease).

[0063] When a short circuit occurs inside such a normal battery cell, the amount of self-discharge due to the internal short circuit may increase rapidly, and accordingly, the rate of decrease in the cell voltage increases (i.e., the first derivative value increases).

[0064] That is, in the case of an abnormal battery cell in which a short circuit has occurred, the first derivative value changes from a decreasing trend to an increasing trend, and the processor 200 of this embodiment is configured to diagnose an abnormality in the battery cell based on such a change in the behavior of the first derivative value (i.e., a change in the behavior of the cell voltage change rate).

[0065] Specifically, processor 200 can identify a group of candidate abnormal cells, consisting of one or more battery cells predicted to have an abnormality, by determining whether the sign of the slope of the rate of change of cell voltage with respect to time has changed. That is, a change in the sign of the slope of the rate of change of cell voltage with respect to time means that the first-order derivative value changes from a decreasing trend (negative sign) to an increasing trend (positive sign), which indicates the possibility of an internal short circuit occurring in the battery cell. Therefore, when the sign of the slope of the rate of change of cell voltage with respect to time has changed, processor 200 can classify the corresponding battery cell as a group of candidate abnormal cells. This has the same meaning as classifying a battery cell in which an inflection point of the cell voltage with respect to time has formed (i.e., the second-order derivative value has a value of 0) as a group of candidate abnormal cells. FIG. 6 shows experimental data of the cell voltage curve with respect to time of a normal battery cell and the cell voltage curve with respect to time of four abnormal battery cells.

[0066] When a group of candidate abnormal cells is identified, the processor 200 may discharge the battery cells classified as the group of candidate abnormal cells and then block subsequent charging of the discharged battery cells, thereby eliminating the risk of thermal runaway and fire caused by the continuous use of a battery cell suspected of having an internal short circuit.

[0067] In order to more accurately diagnose abnormalities in the battery cells, the processor 200 may further consider the maximum value of the cell voltage change rate and the rate of change of the open circuit voltage, along with whether or not the slope of the cell voltage change rate has changed, to diagnose abnormalities in the battery cells.

[0068] Specifically, when the sign of the slope (i.e., second-order differential value) of the cell voltage change rate of the battery cell with respect to time changes (i.e., when an inflection point is formed), and the maximum value of the cell voltage change rate (i.e., first-order differential value) with respect to time of the battery cell is equal to or greater than a reference voltage change rate predefined in memory 100, processor 200 may classify the battery cell as a candidate abnormal cell.

[0069] That is, if the maximum value of the first-order differential value is equal to or greater than the reference voltage change rate, it means that the self-discharge rate of the corresponding battery cell is high, and such a phenomenon may be caused by an internal short circuit of the battery cell. Therefore, the processor 200 can diagnose the abnormality of the battery cell more accurately by additionally considering the maximum value of the first-order differential value along with whether or not the sign of the second-order differential value has changed. Figure 7 shows experimental data of the first-order differential value of a normal battery cell and the first-order differential value of four abnormal battery cells.

[0070] In addition, the processor 200 may classify a battery cell as a candidate abnormal cell when the sign of the slope of the cell voltage change rate with respect to time of the battery cell changes and the change rate of the open circuit voltage of the battery cell (the rate of decrease in the open circuit voltage with respect to time) is equal to or greater than a predefined reference OCV change rate.

[0071] That is, even if the decrease rate of the open circuit voltage of the battery cell is equal to or greater than the reference OCV change rate, it can be regarded as a state in which the self-discharge rate has increased due to an internal short circuit of the battery cell. Therefore, the processor 200 can diagnose the abnormality of the battery cell more precisely by additionally considering the decrease rate of the open circuit voltage as well as whether or not the sign of the second derivative value has changed.

[0072] Furthermore, an embodiment may be provided in which, if the sign of the slope of the cell voltage change rate of a battery cell with respect to time is changed, the maximum value of the cell voltage change rate of the battery cell with respect to time is equal to or greater than a reference voltage change rate, and the change rate of the open circuit voltage of the battery cell is equal to or greater than a reference OCV change rate, the corresponding battery cell is classified as a candidate abnormal cell group.

[0073] To improve the accuracy of the abnormality diagnosis of the battery cell, the processor 200 may determine whether a state in which an inflection point where the second derivative of the battery cell has a value of 0 has been formed has occurred a plurality of times equal to a first counting value defined in the memory 100, whether a state in which the maximum value of the first derivative is equal to or greater than a reference voltage change rate has occurred a plurality of times equal to a second counting value defined in the memory 100, and whether a state in which the change rate of the open circuit voltage is equal to or greater than a reference OCV change rate has occurred a plurality of times equal to a third counting value defined in the memory 100. The processor 200 may be configured to classify the corresponding battery cell as a candidate abnormal cell only when each of the above states has occurred a plurality of times equal to the counting value.

[0074] Table 1 below shows experimental data comparing the presence and frequency of inflection points, the maximum first derivative value, and the rate of change of open circuit voltage for four abnormal battery cells with normal battery cells.

[0075] [Table 1]

[0076] Based on the experimental data such as Table 1, the reference SOC, reference voltage change rate, reference OCV change rate, and first to third counting values ​​presented as critical data in this embodiment may be selected as specific numerical values ​​and predefined in memory 100. For example, the reference SOC may be predefined as a value of 80[%], the reference voltage change rate as a value of 4[mV / 5 hours], the reference OCV change rate as a value of 0.7[mV / hour], and the first to third counting values ​​as values ​​of 2, 3, and 2, respectively.

[0077] (2) Second Example The second embodiment focuses on a configuration that precisely diagnoses battery cell abnormalities within a range where normal operation of the battery system is ensured by performing a discharge operation and a further charge cut-off operation only on battery cells that are finally classified as having an abnormality through a stepwise monitoring and classification operation in which the “second order differential value” and the “maximum value of the first order differential value” of the plurality of battery cells are monitored to perform an initial classification of abnormal cell candidate groups, and then monitoring the “open circuit voltage” of the initially classified abnormal cell candidate groups to finally classify the abnormal cells.

[0078] The terms used in the second embodiment will be defined first. The first parameter described below may be defined as the behavior of the cell voltage change rate that occurs when the battery cell is discharged, and may include the behavior change of the cell voltage change rate (i.e., the second derivative value) and the maximum value of the cell voltage change rate (i.e., the maximum value of the first derivative value) described in the first embodiment. The second parameter may be defined as the rate of change of the open circuit voltage that occurs when the battery cell is discharged.

[0079] The processor 200 can diagnose abnormalities in battery cells in a stepwise manner through stepwise monitoring of the first and second parameters. That is, the processor 200 can operate by first monitoring the first parameter of the first and second parameters to determine one or more battery cells predicted (suspected) to have an abnormality among the plurality of battery cells, thereby identifying a group of candidate abnormal cells, and then subsequently monitoring the second parameter for the identified group of candidate abnormal cells to finally classify the battery cells in which an abnormality has occurred. In this case, the operation of determining whether the SOC of the battery cell is formed at a reference SOC and the operation of waiting for a reference time, as in the first embodiment, can also be applied to the second embodiment.

[0080] The operation of the processor 200 will now be described in detail.

[0081] First, the processor 200 may monitor the first parameter by determining whether the sign of the slope of the rate of change of the cell voltage of the battery cell with respect to time changes and whether the maximum value of the rate of change of the cell voltage of the battery cell with respect to time is equal to or greater than a predetermined reference voltage change rate. That is, the processor 200 may monitor the first parameter by determining whether the first derivative has changed from a decreasing trend (negative sign) to an increasing trend (positive sign) (whether an inflection point of the cell voltage with respect to time is formed) and whether the maximum value of the first derivative is equal to or greater than a reference voltage change rate.

[0082] In the above process, if the sign of the slope of the cell voltage change rate with respect to time of the battery cell changes and it is determined that the maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than the reference voltage change rate (i.e., if an inflection point of the cell voltage with respect to time is formed and it is determined that the maximum value of the first derivative is equal to or greater than the reference voltage change rate), the processor 200 can primarily classify the corresponding battery cell as a defective cell candidate group. Unlike the first embodiment, the second embodiment excludes the discharge operation and the additional charge cut-off operation for the battery cell classified as a defective cell candidate group.

[0083] When the abnormal cell candidate group is primarily classified, the processor 200 may monitor a second parameter for the primarily classified abnormal cell candidate group, and if a rate of change in the open circuit voltage of a battery cell included in the abnormal cell candidate group is equal to or greater than a predetermined reference OCV change rate, the processor 200 may finally classify the corresponding battery cell as an abnormal cell. Thereafter, the processor 200 may operate to discharge the battery cell corresponding to the finally classified abnormal cell and then cut off subsequent charging of the battery cell.

[0084] In the second embodiment, the first parameter corresponding to the “cell voltage change rate behavior” is used as a parameter for detecting the “signs” of an abnormality, such as an internal short circuit in the battery, and the second parameter corresponding to the “open circuit voltage change rate” is used as a parameter for detecting the “results” of the abnormality. If a sign of an abnormality in a battery cell is detected by monitoring the first parameter, the corresponding battery cell is classified into a group of candidate abnormal cells, but normal operation of the battery cell is maintained. If a result of an abnormality in a battery cell is detected by monitoring the second parameter of a battery cell belonging to the group of candidate abnormal cells, the corresponding battery cell is finally classified as an abnormal battery cell, and a discharge operation and a further charge cut-off operation are performed on the corresponding battery cell. As a result, even if a sign of an abnormality is detected, normal operation of the battery system is maintained until the battery cell is finally identified as an abnormal battery cell, and therefore unnecessary discharge operations and further charge cut-off operations can be prevented from being performed on the battery cell.

[0085] 3. Battery diagnostic method 8 is a flowchart of the battery diagnostic method according to the first embodiment. The battery diagnostic method according to the first embodiment will be described with reference to FIG. 8, and a detailed description of the components that overlap with the above content will be omitted, and the chronological configuration will be mainly described.

[0086] First, the processor 200 determines whether the SOC of the battery cell is set to a reference SOC predefined in the memory 100 (S810). If it is determined in step S810 that the SOC of the battery cell is set to a value equal to or lower than the reference SOC, the processor 200 sets the SOC of the battery cell to the reference SOC through a predetermined charging method (e.g., CC-CV charging method) (S820).

[0087] If it is determined in step S810 that the SOC of the battery cell is formed at the reference SOC, or if the SOC of the battery cell is formed at the reference SOC through step S820, the processor 200 waits for a reference time for the cell voltage of the battery cell to stabilize (S830).

[0088] When the reference time has elapsed, the processor 200 diagnoses an abnormality in the battery cell by analyzing a behavioral change in the cell voltage change rate that occurs when the battery cell is discharged (S840).

[0089] In step S840, the processor 200 determines whether the sign of the slope of the cell voltage change rate with respect to time has changed, and can identify a group of candidate abnormal cells consisting of one or more battery cells that are predicted to have an abnormality. Specifically, if the sign of the slope of the cell voltage change rate with respect to time of a battery cell has changed, the battery cell can be classified as a group of candidate abnormal cells.

[0090] Meanwhile, in step S840, the processor 200 may classify the battery cell as a candidate abnormal cell if i) the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed and the maximum value of the cell voltage change rate of the battery cell with respect to time is equal to or greater than the reference voltage change rate, or ii) the sign of the slope of the cell voltage change rate of the battery cell with respect to time has changed and the rate of change of the open circuit voltage of the battery cell is equal to or greater than the reference OCV change rate.

[0091] When the abnormal cell candidate group is identified in step S840, the processor 200 discharges the battery cells classified into the abnormal cell candidate group (S850), and blocks subsequent charging of the discharged battery cells (S860).

[0092] 9 is a flowchart of the battery diagnostic method according to the second embodiment, which will be described with reference to FIG.

[0093] First, the processor 200 determines whether the SOC of the battery cell is set to a reference SOC predefined in the memory 100 (S910). If it is determined in step S910 that the SOC of the battery cell is set to a value equal to or lower than the reference SOC, the processor 200 sets the SOC of the battery cell to the reference SOC through a predetermined charging method (e.g., CC-CV charging method) (S920).

[0094] If it is determined in step S910 that the SOC of the battery cell is formed at the reference SOC, or if the SOC of the battery cell is formed at the reference SOC through step S920, the processor 200 waits for a reference time for the cell voltage of the battery cell to stabilize (S930).

[0095] When the reference time has elapsed, the processor 200 diagnoses an abnormality in the battery cell through stepwise monitoring of a first parameter defined by the behavior of the cell voltage change rate occurring when the battery cell is discharged and a second parameter defined by the change rate of the open circuit voltage occurring when the battery cell is discharged (S940).

[0096] In step S940, the processor 200 may monitor the first parameter in a manner of determining whether the sign of the slope of the cell voltage change rate with respect to time of the battery cell has changed and whether the maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than a predetermined reference voltage change rate. In this case, if the sign of the slope of the cell voltage change rate with respect to time of the battery cell has changed and the maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than the reference voltage change rate, the processor 200 may primarily classify the battery cell as a candidate abnormal cell.

[0097] Thereafter, the processor 200 can monitor the second parameter for the group of initially classified abnormal cell candidates, and specifically, if the rate of change in the open circuit voltage of a battery cell included in the group of abnormal cell candidates is equal to or greater than the reference OCV change rate, the processor 200 can finally classify the battery cell as an abnormal cell.

[0098] When the abnormal cell is finally classified in step S940, the processor 200 may discharge the battery cell corresponding to the finally classified abnormal cell (S950) and cut off subsequent charging of the battery cell (S960).

[0099] As described above, according to the present invention, by diagnosing abnormalities in a battery cell by analyzing the behavior of the cell voltage change rate (i.e., the inflection point of the cell voltage with respect to time) that appears when a battery cell having a predetermined SOC is discharged, it is possible to diagnose abnormalities in the battery cell in advance, such as an internal short circuit in the cell due to the precipitation of lithium salt, and to effectively eliminate the risk of thermal runaway and fire in the battery cell by performing a discharge operation and a further charge cut-off operation for the battery cell that is predicted to have an abnormality.

[0100] In addition, according to the present invention, the accuracy of abnormality diagnosis can be improved by diagnosing abnormalities in a battery cell by comprehensively considering the maximum value of the cell voltage change rate over time and the open circuit voltage, along with the inflection point of the cell voltage over time.

[0101] In addition, according to the present invention, abnormalities in battery cells are diagnosed in a stepwise manner through stepwise monitoring of a first parameter defined by the behavior of the cell voltage change rate that appears when the battery cell is discharged and a second parameter defined by the open circuit voltage that appears when the battery cell is discharged, and a discharge operation and a further charge cut-off operation are performed only on battery cells that are finally classified as having an abnormality, thereby making it possible to pre-diagnose abnormalities in battery cells within a range that ensures normal operation of the battery system and eliminate the risk of thermal runaway and fire.

[0102] The implementations described herein may be embodied as, for example, a method or process, an apparatus, a software program, a data stream, or a signal. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the discussed features may also be embodied in other forms (e.g., an apparatus or a program). An apparatus may be embodied in appropriate hardware, software, firmware, etc. A method may be embodied in an apparatus, such as, for example, a processor, which generally refers to a processing device including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as computers, mobile phones, portable / personal digital assistants (“PDAs”), and other devices that facilitate communication of information between end users.

[0103] Although the present invention has been described with reference to the embodiments shown in the drawings, it is understood that these are merely illustrative and that those skilled in the art will recognize that various modifications and equivalent alternative embodiments are possible. Therefore, the technical scope of the present invention should be determined by the following claims. [Explanation of symbols]

[0104] 100:Memory 200: Processor

Claims

1. a processor configured to diagnose abnormalities in the battery cells; and a memory that stores one or more instructions that are executed by the processor; The processor: The battery diagnostic device diagnoses an abnormality in the battery cell by analyzing a behavior change in a cell voltage change rate that occurs when the battery cell is discharged in a state where the SOC (State of Charge) of the battery cell is formed at a predetermined reference SOC.

2. 2. The battery diagnostic device according to claim 1, wherein the processor starts an abnormality diagnosis operation for the battery cell when a predetermined reference time for stabilizing a cell voltage of the battery cell has elapsed after the SOC of the battery cell is formed at the reference SOC.

3. 2. The battery diagnostic device according to claim 1, wherein the processor determines whether a sign of a slope of a cell voltage change rate with respect to time changes when analyzing a behavior change of the cell voltage change rate of the battery cell, and identifies a group of candidate abnormal cells consisting of one or more battery cells predicted to have an abnormality.

4. The battery diagnostic device according to claim 3 , wherein the processor classifies the battery cell as a candidate abnormal cell when a sign of a slope of a rate of change of a cell voltage with respect to time of the battery cell changes.

5. 4. The battery diagnostic device according to claim 3, wherein the processor classifies the battery cell as a candidate abnormal cell when a sign of a slope of a cell voltage change rate with respect to time of the battery cell changes and a maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than a predetermined reference voltage change rate.

6. 4. The battery diagnostic device of claim 3, wherein the processor classifies the battery cell as a candidate abnormal cell when a sign of a slope of a cell voltage change rate with respect to time of the battery cell changes and a change rate of an open circuit voltage (OCV) of the battery cell is equal to or greater than a predefined reference OCV change rate.

7. The battery diagnostic device according to claim 3 , wherein the processor discharges the battery cells classified into the abnormal cell candidate group, and then blocks subsequent charging of the discharged battery cells.

8. a processor configured to diagnose abnormalities in the battery cells; and a memory that stores one or more instructions that are executed by the processor; The processor: The battery diagnostic device diagnoses an abnormality in the battery cell by stepwise monitoring a first parameter defined by a behavior of a cell voltage change rate occurring when the battery cell is discharged, and a second parameter defined by a change rate of an open circuit voltage (OCV) occurring when the battery cell is discharged.

9. 9. The battery diagnostic device of claim 8, wherein the processor, when monitoring the first parameter, determines whether a sign of a slope of a rate of change in cell voltage of the battery cell with respect to time changes, and whether a maximum value of the rate of change in cell voltage of the battery cell with respect to time is equal to or greater than a predetermined reference rate of change in voltage.

10. 10. The battery diagnostic device of claim 9, wherein the processor is configured to first monitor the first parameter among the first and second parameters, and when a sign of a slope of a cell voltage change rate with respect to time of the battery cell changes and a maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than the reference voltage change rate, the processor primarily classifies the battery cell as a candidate abnormal cell.

11. 11. The battery diagnostic device of claim 10, wherein the processor is configured to monitor the second parameter for the group of initially classified abnormal cell candidates, and when a rate of change in open circuit voltage of the battery cell included in the group of abnormal cell candidates is equal to or greater than a predefined reference OCV change rate, the processor finally classifies the battery cell as an abnormal cell.

12. The battery diagnostic device according to claim 11, wherein the processor discharges the battery cell corresponding to the finally classified abnormal cell, and then blocks subsequent charging of the battery cell.

13. 9. The battery diagnostic device of claim 8, wherein the processor monitors the first and second parameters that appear during a discharge process of the battery cell after the SOC (State of Charge) of the battery cell is formed at a predetermined reference SOC.

14. A processor determines whether the SOC (State Of Charge) of the battery cell is formed at a predefined reference SOC; and the processor diagnosing an abnormality in the battery cell by analyzing a behavior change in a cell voltage change rate that occurs when the battery cell is discharged when the SOC of the battery cell is formed at the reference SOC.

15. After the determining step, The processor further includes determining whether a predetermined reference time for stabilizing the cell voltage of the battery cell has elapsed; The battery diagnostic method according to claim 14, wherein the diagnosing step is performed when the reference time has elapsed.

16. In the diagnosing step, the processor 15. The battery diagnosis method of claim 14, wherein, when analyzing a behavior change in the cell voltage change rate of the battery cell, it is determined whether a sign of a slope of the cell voltage change rate with respect to time changes, and a group of candidate abnormal cells consisting of one or more battery cells predicted to have an abnormality is identified.

17. In the diagnosing step, the processor The battery diagnosis method according to claim 16, wherein the battery cell is classified as a candidate abnormal cell when a sign of a gradient of a rate of change of a cell voltage with respect to time of the battery cell is changed.

18. In the diagnosing step, the processor 17. The battery diagnosis method of claim 16, wherein, when a sign of a gradient of a cell voltage change rate with respect to time of the battery cell is changed and a maximum value of the cell voltage change rate with respect to time of the battery cell is equal to or greater than a predefined reference voltage change rate, the battery cell is classified as a candidate abnormal cell.

19. In the diagnosing step, the processor 17. The battery diagnosis method of claim 16, wherein, when a sign of a gradient of a cell voltage change rate with respect to time of the battery cell changes and a change rate of an open circuit voltage (OCV) of the battery cell is equal to or greater than a predefined reference OCV change rate, the battery cell is classified as a candidate abnormal cell.

20. The processor discharges the battery cells classified into the abnormal cell candidate group; and 17. The battery diagnostic method of claim 16, further comprising: the processor cutting off subsequent charging of the discharged battery cell.

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