Battery diagnosis apparatus and battery diagnosis method

Abstract

A battery diagnosis apparatus and a battery diagnosis method are disclosed. The battery diagnosis method according to the present invention comprises the steps of: detecting a deterioration feature point located within a reference voltage range from a differential capacity profile representing a voltage-differential capacity relationship characteristic of a battery cell in the reference voltage range; updating, on the basis of the deterioration feature point detection result, deterioration history information indicating the change history of position information and / or type information of the deterioration feature point; and diagnosing a deterioration state of the battery cell on the basis of the updated deterioration history information.

Description

Battery diagnostic device and battery diagnostic method

[0001] The present invention relates to a technology for diagnosing the deterioration state of a battery.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0018379, filed on February 6, 2024, and Korean Patent Application No. 10-2025-0009688, filed on January 22, 2025, the entire contents of which are disclosed in the specification and drawings of the above applications are incorporated herein by reference.

[0003] Recently, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has rapidly increased, and the development of electric vehicles, energy storage batteries, robots, and satellites has been in full swing, research into high-performance batteries capable of repeated charging and discharging is actively being conducted.

[0004] Currently commercialized batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium batteries. Among these, lithium batteries are receiving attention for their advantages of being able to charge and discharge freely, having a very low self-discharge rate, and having a high energy density, as they have almost no memory effect compared to nickel-based batteries.

[0005] Various techniques exist for diagnosing battery deterioration. In particular, Differential Capacity Analysis (DQA) is primarily used to identify battery deterioration or internal anomalies based on externally observable parameters (e.g., voltage and current).

[0006] In diagnosing a battery using differential capacity analysis, it is necessary to detect feature points located on the differential capacity profile (which may be referred to as the 'V-dQ / dV curve') as key elements.

[0007] In this regard, the polarization phenomenon, which is deeply related to the charge / discharge characteristics of a battery, is dependent on various resistance components of the battery (e.g., ohmic resistance, charge transfer resistance, diffusion resistance), and the polarization phenomenon tends to worsen as the battery deteriorates. For example, one of the causes of the difference between the open circuit voltage (OCV) and closed circuit voltage (CCV) of a battery during charging or discharging is the overpotential formed by polarization.

[0008] Depending on the magnitude of polarization, the voltage range in which the redox reaction of at least one positive electrode active material and / or at least one negative electrode active material of the battery primarily occurs shifts, or the intensity of the redox reaction in that voltage range changes somewhat. The change in charge-discharge characteristics due to deterioration may change not only the location of at least one characteristic point but also the type of the characteristic point.

[0009] However, the conventional DQA-based diagnosis method has a disadvantage in that the diagnosis accuracy is somewhat limited because it is a method that detects a specific type of feature point (e.g., peak) for each diagnosis round and then is based only on the location information (e.g., voltage value and / or differential capacity value) of the detected feature point.

[0010] The present invention aims to provide a battery diagnosis device and a battery diagnosis method capable of precisely diagnosing the deterioration state of a battery that cannot be directly confirmed from the outside by analyzing the change history of at least one of the location and type of a characteristic point identified from differential information of the charge / discharge characteristics of the battery.

[0011] Other objects and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0012] A battery diagnosis method according to one aspect of the present invention comprises the steps of: detecting a deterioration feature point located within a reference voltage range from a differential capacity profile representing a voltage-differential capacity relationship characteristic of a battery cell within a reference voltage range; updating deterioration history information representing a change history of at least one of location information and type information of the deterioration feature point based on a result of detecting the deterioration feature point; and diagnosing a deterioration state of the battery cell based on the updated deterioration history information.

[0013] The battery diagnosis method may further include a step of curve fitting a voltage-current data set acquired while the voltage of the battery cell varies over the reference voltage range to determine a voltage profile of the battery cell for the reference voltage range; and a step of differentiating the voltage profile to obtain the differential capacity profile.

[0014] The step of diagnosing the deterioration state of the battery cell may include a step of diagnosing that a loss of positive electrode capacity of the battery cell has occurred when a first tendency in which the deterioration characteristic point approaches the baseline from the upper side of the baseline is identified from the updated deterioration history information.

[0015] The step of diagnosing the deterioration state of the battery cell may further include a step of determining a deterioration rate of the battery cell by comparing the current differential capacity value of the deterioration characteristic point with the initial differential capacity value when it is diagnosed that a loss of positive electrode capacity has occurred in the battery cell.

[0016] The step of diagnosing the deterioration state of the battery cell may include a step of diagnosing that additional available lithium loss has occurred along with the loss of positive electrode capacity of the battery cell when a second tendency in which the deterioration characteristic point moves away from the baseline on the lower side of the baseline is identified from the updated deterioration history information.

[0017] The step of diagnosing the deterioration state of the battery cell may further include a step of determining the available lithium loss rate of the battery cell based on the difference between the current differential capacity value of the deterioration characteristic point and the differential capacity value of the reference line, if it is diagnosed that available lithium loss of the battery cell has occurred.

[0018] The above battery diagnosis method may further include, as a step preceding the step of determining a differential capacity profile of the battery cell for the reference voltage range, a step of determining the reference voltage range based on the initial differential capacity profile of the battery cell.

[0019] The step of determining the reference voltage range may include the steps of: detecting a main feature point, which is a peak located within a predetermined voltage range of interest, from the initial differential capacity profile; detecting a first auxiliary feature point located on a lower voltage side than the main feature point and a second auxiliary feature point located on a higher voltage side than the main feature point; and determining the reference voltage range to be the same as the voltage range between the first auxiliary feature point and the second auxiliary feature point.

[0020] The above reference line may be a straight line passing through the first auxiliary feature point and the second auxiliary feature point.

[0021] According to another aspect of the present invention, a battery diagnostic device includes a processor that generates a differential capacity profile representing voltage-differential capacity relationship characteristics of a battery cell in a reference voltage range. The processor is configured to detect, from the differential capacity profile, a deterioration feature point located within the reference voltage range. The processor is configured to update deterioration history information representing a change history of at least one of position information and type information of the deterioration feature point based on a detection result of the deterioration feature point. The processor is configured to diagnose a deterioration state of the battery cell based on the updated deterioration history information.

[0022] The processor may be configured to diagnose that a loss of positive electrode capacity of the battery cell has occurred when a first tendency for the deterioration feature point to approach the baseline from an upper side of the baseline is identified from the updated deterioration history information.

[0023] The processor may be configured to diagnose that additional available lithium loss has occurred in conjunction with a loss of positive electrode capacity of the battery cell when a second tendency of the degradation feature point moving away from the baseline on the lower side of the baseline is identified from the updated degradation history information.

[0024] The processor may determine the reference voltage range based on an initial differential capacity profile of the battery cell prior to the operation of determining the differential capacity profile.

[0025] A battery pack according to another aspect of the present invention includes the battery diagnostic device.

[0026] A battery system according to another aspect of the present invention includes the battery diagnostic device.

[0027] According to at least one of the embodiments of the present invention, by analyzing the change history of at least one of the positions and types of characteristic points identified from differential information of the charge / discharge characteristics of the battery, the deterioration state of the battery can be precisely diagnosed without direct confirmation from the outside.

[0028] Additionally, according to at least one of the embodiments of the present invention, detailed information on the main cause causing deterioration of the battery can be provided.

[0029] Additionally, according to at least one of the embodiments of the present invention, if an indication of accelerated deterioration of the battery (e.g., loss of available lithium) is detected from the diagnostic results of the deterioration state, additional control measures can be taken to control or alleviate the indication of accelerated deterioration of the battery.

[0030] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0031] 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.

[0032] FIG. 1 is a drawing for reference in schematically explaining the configuration of a battery diagnostic device according to the present invention.

[0033] Figure 2 is an exemplary graph used as a reference to explain changes in capacity-voltage relationship characteristics due to battery deterioration.

[0034] Figures 3 and 4 are exemplary graphs used for explaining changes in voltage-differential capacity relationship characteristics due to battery deterioration.

[0035] FIG. 5 is a flowchart for reference in schematically explaining a battery diagnosis method according to another embodiment of the present invention.

[0036] FIG. 6 is a flowchart schematically illustrating sub-steps that can be included in step S500 of FIG. 5.

[0037] Figure 7 is a drawing referenced in explaining the method of Figure 6.

[0038] FIG. 8 is a flowchart schematically illustrating sub-steps that can be included in step S540 of FIG. 5.

[0039] FIG. 9 is a flowchart schematically illustrating sub-steps that may be included in step S550 of FIG. 5.

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that conforms to the technical spirit of the present invention.

[0041] 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. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0042] Terms that include ordinal numbers, such as first, second, etc., are used to distinguish one of the various components from the rest, and are not used to limit the components by such terms.

[0043] Throughout the specification, when a part is said to "include" a component, this does not exclude other components, unless otherwise stated, but rather implies that other components may be included. Furthermore, terms such as "unit" used throughout the specification mean a unit that processes at least one function or operation, and may be implemented using hardware, software, or a combination of hardware and software.

[0044] Additionally, throughout the specification, when we say that a part is "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "indirectly connected" with other elements in between.

[0045] FIG. 1 is a drawing for reference in schematically explaining the configuration of a battery diagnostic device according to the present invention.

[0046] Referring to Fig. 1, a battery system (1) includes a system controller (2), a battery pack (10), an inverter (30), and an electric motor (40). The charge / discharge terminals (P+, P-) of the battery pack (10) can be electrically coupled to a charging station (300) via a charging cable or the like. The battery system (1) is not particularly limited as long as it is an electric system in which a battery (11) is used as a power source, such as an electric vehicle.

[0047] The system controller (2) (e.g., ECU: Electronic Control Unit) is configured to transmit a key-on signal to the battery management system (100) in response to a start button (not shown) provided in the battery system (1) being turned to the ON position by a user. The system controller (2) is configured to transmit a key-off signal to the battery management system (100) in response to a start button being turned to the OFF position by a user. The charging station (300) can communicate with the system controller (2) and supply charging power selected from among constant power, constant current, and constant voltage through the charge / discharge terminals (P+, P-) of the battery pack (10).

[0048] The battery pack (10) includes a battery (11) and a battery management system (100). The battery pack (10) may further include a relay (20).

[0049] The battery (11) includes at least one battery cell (BC). In Fig. 1, the battery (11) includes a plurality of battery cells (BC1 to BC) connected in series. N , N is a natural number greater than or equal to 2) is illustrated as an example. Multiple battery cells (BC1 to BC N ) may be provided to have the same electrochemical specifications. Hereinafter, a plurality of battery cells (BC1 to BC N ), the symbol 'BC' is assigned to the battery cell. The battery cell (BC) can be the subject of diagnosis by a charging station (300) or a cloud server (not shown).

[0050] As long as it is an electrochemical device capable of repeated charging and discharging, including a lithium-ion cell, the type of battery cell (BC) is not particularly limited. The positive active material of the battery cell (BC) is, for example, LiNi. 8 / 10 Co 1 / 10 Mn 1 / 10Lithium metal composite oxides such as O2 can be used. As the negative active material of the battery cell (BC), a carbon-based material (e.g., graphite) can be used, for example.

[0051] The charging station (300) can execute a diagnostic process for a battery cell (BC) through collaboration with an inverter (30) having a discharge function.

[0052] The relay (20) is electrically connected in series to the battery (11) via a power path connecting the battery (11) and the inverter (30). In Fig. 1, the relay (20) is illustrated as being connected between the positive terminal of the battery (11) and the charge / discharge terminal (P+). The relay (20) is turned on and off in response to a switching signal from the battery management system (100). The relay (20) may be a mechanical contactor that is turned on and off by the magnetic force of a coil, or a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect transistor).

[0053] An inverter (30) is provided to convert direct current from a battery (11) included in a battery pack (10) into alternating current in response to a command from at least one of a battery management system (100), a system controller (2), and a battery diagnostic device (302). An electric motor (40) is driven using alternating current power from the inverter (30). For example, a three-phase alternating current motor can be used as the electric motor (40). Components within the battery system (1) that receive discharge power from the battery (11), including the inverter (30) and the electric motor (40), can be collectively referred to as an electric load.

[0054] The battery management system (100) includes a sensing unit (110) and a control circuit (130). The battery management system (100) may further include a communication circuit (150).

[0055] The sensing unit (110) includes a voltage sensor (111). The sensing unit (110) may further include a current sensor (112).

[0056] A voltage sensor (111) is connected to the positive and negative terminals of a battery cell (BC), detects the voltage of the battery cell (BC), and is configured to generate a voltage signal representing a measured value of the detected voltage. The voltage sensor (111) may be implemented as one or a combination of two or more of known voltage detection elements, such as a voltage measurement IC.

[0057] The current sensor (112) is connected in series to the battery (11) through a current path between the battery (11) and the inverter (30). The current sensor (112) is configured to detect a current flowing through the battery (11) (which may be referred to as a 'charge / discharge current') and generate a current signal representing a measured value of the detected current. A plurality of battery cells (BC1 to BC) N ) are connected in series, the current flowing in the battery (11) is the same as the current flowing in the battery cell (BC). The current sensor (112) can be implemented with one or a combination of two or more of known current detection elements such as a shunt resistor, a Hall effect element, etc.

[0058] The communication circuit (150) is configured to support wired or wireless communication between the control circuit (130) and the system controller (2) and / or the charging station (300). The wired communication may be, for example, CAN (controller area network) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. Of course, as long as it supports wired or wireless communication between the control circuit (130) and the system controller (2), the type of communication protocol is not particularly limited. The communication circuit (150) may include an output device (e.g., a display, a speaker) that provides information received from the control circuit (130) and / or the system controller (2) in a form recognizable to a user (driver).

[0059] The control circuit (130) is operably coupled to the relay (20), the sensing unit (110), and the communication circuit (150). In the present specification, the two components being operably coupled means that the two components are directly or indirectly connected so as to be capable of transmitting and receiving signals in one direction or both directions.

[0060] The control circuit (130) can collect a voltage signal from the voltage sensor (111) and a current signal from the current sensor (112). In this specification, the detection signal may refer only to the voltage signal, or may be a term that collectively refers to both the voltage signal and the current signal. That is, the control circuit (130) can convert and record each analog signal collected from the sensors (111, 112) into a digital value using an ADC (Analog to Digital Converter) provided therein. Alternatively, each of the voltage sensor (111) and the current sensor (112) may include an ADC therein and transmit the digital value to the control circuit (130).

[0061] The control circuit (130) may be referred to as a 'battery controller' and may be implemented in hardware using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors, and other electrical units for performing functions.

[0062] The memory (131) may include at least one type of storage medium among, for example, a flash memory type, a hard disk type, an SSD (Solid State Disk type), an SDD (Silicon Disk Drive type), a multimedia card micro type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and a programmable read-only memory (PROM). The memory (131) may store data and a program required for an operation by the control circuit (130). The memory (131) may store data indicating a result of an operation by the control circuit (130).

[0063] When the relay (20) is turned on, the battery (11) enters the charging mode or the discharging mode. When the relay (20) is turned off while the battery (11) is in use in the charging mode or the discharging mode, the battery (11) switches to the idle mode.

[0064] The control circuit (130) can turn on the relay (20) in response to a key-on signal. The control circuit (130) can turn off the relay (20) in response to a key-off signal. The key-on signal is a signal requesting a transition from idle to charging or discharging. The key-off signal is a signal requesting a transition from charging or discharging to idle. Alternatively, the on / off control of the relay (20) may be handled by the system controller (2) instead of the control circuit (130).

[0065] In this specification, measurement data (e.g., time series) of a certain parameter may represent the temporal change history of that parameter. Furthermore, a profile (or curve) representing the correspondence between two parameters over the same period may be a mapping of the measurement data of two parameters so that it can be expressed in the form of a two-dimensional graph, or a polynomial equation obtained by applying a predetermined curve fitting logic to a set of two mapped measurement data. Here, the degree of the highest term of the polynomial equation may be predetermined.

[0066] The battery diagnostic device (302) includes a processor (320). The battery diagnostic device (302) may further include at least one of a communication unit (310) and a memory unit (330).

[0067] The charging station (300) includes a stimulus application device (301) and may further include a battery diagnosis device (302). Alternatively, the battery diagnosis device (302) may be configured independently from the charging station (300). For example, the battery diagnosis device (302) may be provided in a form included in a cloud server (not shown). The cloud server may be located remotely from the charging station (300). In this case, the communication unit (310) of the battery diagnosis device (302) may perform diagnostic procedures on the battery cell (BC) through remote communication with the stimulus application device (301) and / or the battery system (1).

[0068] According to an implementation example, the battery diagnostic device (302) may be included in the battery pack (10). In this case, the battery management system (100) may be omitted from the battery pack (10). That is, the processor (320) may replace all functions of the control circuit (130) of the battery management system (100). For example, the communication unit (310) may be included as a sub-component of the processor (320) and may be responsible for all functions of the communication circuit (150) of the battery management system (100). In addition, the communication unit (310) may collect measurement information including at least one of a voltage measurement signal and a current measurement signal from the sensing unit (110).

[0069] The stimulation application device (301) may include a charger that provides charging power to the battery pack (10). The stimulation application device (301) may further include a discharger that extracts discharge power from the battery pack (10). The stimulation application device (301), either alone or in cooperation with an inverter (30), may apply various electrical stimuli to the battery cell (BC) for diagnosis of the battery cell (BC).

[0070] The communication unit (310) is configured to support wired or wireless communication between the processor (320) and the system controller (2). The communication unit (310) can transmit the results of the diagnosis of the battery cell (BC) performed by the processor (320) to the battery system (1).

[0071] The processor (320) may be implemented in hardware using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors, and other electrical units for performing functions.

[0072] The memory unit (330) may include at least one type of storage medium, for example, a flash memory type, a hard disk type, an SSD (Solid State Disk type), an SDD (Silicon Disk Drive type), a multimedia card micro type, a RAM (random access memory), a SRAM (static random access memory), a ROM (read-only memory), an EEPROM (electrically erasable programmable read-only memory), and a PROM (programmable read-only memory). The memory unit (330) may store data and programs required for diagnostic procedures performed by the processor (320). The memory unit (330) may store data representing the results of an operation performed by the processor (320). The memory unit (330) may store data sets and software used to diagnose the deterioration state of the battery cell (BC). The memory unit (330) may be included as a sub-component of the processor (320).

[0073] The processor (320) can determine the voltage, current, capacity, and SOC (State-Of-Charge) of the battery cell (BC) based on the detection signal. The capacity of the battery cell (BC) represents the amount of charge stored in the battery cell (BC) and may also be referred to as “residual capacity.” The processor (320) can determine the capacity of the battery cell (BC) by accumulating the detected value of the current of the battery cell (BC) at predetermined intervals. The SOC of the battery cell (BC) represents the ratio of the capacity of the battery cell (BC) to the maximum capacity of the battery cell (BC) (which may also be referred to as “full charge capacity”) and is typically expressed as 0 to 1 or 0 to 100%. The maximum capacity of the battery cell (BC) gradually decreases as the battery cell (BC) deteriorates.

[0074] FIG. 2 is an exemplary graph used for explaining changes in capacity-voltage relationship characteristics due to battery deterioration, and FIGS. 3 and 4 are exemplary graphs used for explaining changes in voltage-differential capacity relationship characteristics due to battery deterioration. For convenience of explanation, each of the voltage profiles (VP1, VP2, VP3, and VP4) illustrated in FIG. 2 is obtained from the results of a charge-discharge test that intentionally deteriorates the test cell(s). The charge-discharge test may be, for example, a cyclic repetition of CC (Constant Current)-CV (Constant Voltage) charging for a predetermined allowable voltage range, a first pause, a CC discharge, and a second pause. The test cell(s) may be manufactured to have the same specifications as the electrochemical performance of the battery cell (BC) at the time of shipment, and may also be referred to as a 'sample battery cell'.

[0075] Referring to Fig. 2, the voltage profiles (VP1 to VP4) sequentially illustrate the capacity-voltage relationship characteristics of the test cell as the degree of degradation of the test cell increases.

[0076] In detail, the voltage profile (VP1) represents the capacity-voltage relationship characteristics of the test cell during the CC charge of the initial charge-discharge test. The voltage profile (VP2) represents the capacity-voltage relationship characteristics of the test cell at the beginning of life (BOL) when the charge-discharge test has been repeated a first number of times (e.g., 100 times). The voltage profile (VP3) represents the capacity-voltage relationship characteristics of the test cell at the middle of life (MOL) when the charge-discharge test has been repeated a second number of times (e.g., 300 times) that is greater than the first number of times. The voltage profile (VP4) represents the capacity-voltage relationship characteristics of the test cell at the end of life (EOL) when the charge-discharge test has been repeated a third number of times (e.g., 600 times) that is greater than the second number of times. For reference, the end of life can be said to be a state in which replacement or disposal is required due to excessive deterioration.

[0077] Comparing the voltage profiles (VP1, VP2, VP3, VP4), it can be seen that the voltage profile (VP2) is located above (high voltage side) the voltage profile (VP1) based on the horizontal axis representing the capacity, the voltage profile (VP3) is located above the voltage profile (VP2), and the voltage profile (VP4) is located above the voltage profile (VP3). In addition, it can be seen in Fig. 2 that the capacity value (e.g., full charge capacity) corresponding to the upper limit of the allowable voltage range (e.g., 4.2 [V]) gradually decreases as one moves from the voltage profile (VP1) to the voltage profile (VP4).

[0078] That is, at the same capacity, the voltage of the voltage profile (VP2) is higher than that of the voltage profile (VP1), the voltage of the voltage profile (VP3) is higher than that of the voltage profile (VP2), and the voltage of the voltage profile (VP4) is higher than that of the voltage profile (VP3). The reason for these results is that the maximum capacity is lowered due to deterioration, and the voltage increase rate during charging increases.

[0079] Referring to Fig. 3, differential capacity profiles (DQP1, DQP2, DQP3, DQP4) can be confirmed. Differential capacity profiles (DQP1, DQP2, DQP3, DQP4) may be obtained as a result of applying a differential operation to the voltage profiles (VP1, VP2, VP3, VP4) illustrated in Fig. 2. Specifically, differential capacity profiles (DQP1, DQP2, DQP3, DQP4) individually represent the correspondence between the voltage V of the voltage profiles (VP1, VP2, VP3, VP4) and the differential capacity dQ / dV. The differential capacity (or differential capacity value), which is a parameter indicated by the symbol dQ / dV, refers to the ratio of the capacity change dQ to the voltage change dV. The differential capacitance profiles (DQP1, DQP2, DQP3, DQP4) can be individually referred to as derivatives of the voltage profiles (VP1, VP2, VP3, VP4).

[0080] A differential capacity profile (DQP1, also referred to as an "initial differential capacity profile") can provide differential information about the capacity-voltage characteristics obtained during the initial charge-discharge test of a test cell. Each peak located in a differential capacity profile can be the result of a phase transition reaction occurring in a specific electrode active material(s).

[0081] Meanwhile, the inventors of the present invention have recognized through numerous experiments and verifications that when the degradation difference between active materials becomes excessive, the phase transition reaction of a specific active material may be greatly weakened or eliminated, resulting in a decrease in the total number of peaks located in the differential capacity profile. Referring to Fig. 3, the differential capacity profiles (DQP1, DQP2, DQP3) have a total of four peaks across the allowable voltage range, whereas the differential capacity profile (DQP4) in the most degraded state has only a total of three peaks across the allowable voltage range.

[0082] The sub-voltage ranges (ΔV1, ΔV2, ΔV3, ΔV4) may be individually determined to correspond to peaks of the differential capacitance profile (DQP1). For example, the boundaries of two adjacent sub-voltage ranges may be equal to the average voltage value of two peaks of the two sub-voltage ranges. Each sub-voltage range may be predetermined by a user or determined by the processor (320).

[0083] In particular, the maximum differential capacity difference between the differential capacity profiles (DQP1, DQP4) in a specific sub-voltage range (ΔV2) may be significantly larger than the maximum differential capacity differences between the differential capacity profiles (DQP1, DQP4) in other sub-voltage ranges (ΔV1, ΔV3, ΔV4). The maximum differential capacity difference between the differential capacity profiles (DQP1, DQP4) in any sub-voltage range may represent the difference between the differential capacity value of the deterioration feature point of the differential capacity profile (DQP1) and the differential capacity value of the deterioration feature point of the differential capacity profile (DQP4).

[0084] In this case, a specific sub-voltage range (ΔV 2, It can be said that the capacity-voltage relationship characteristic information in the 'voltage range of interest' of the claim scope is focused on information about the deterioration state of the battery cell (BC).

[0085] The inventor of the present invention has recognized that, based on the results of pre-charge / discharge tests on the test cell(s), it is possible to pre-set a specific sub-voltage range to be analyzed when diagnosing the deterioration state of a battery cell (BC).

[0086] FIG. 4 is an enlarged view of a portion of the differential capacitance profiles (DQP1, DQP2, DQP3, DQP4) corresponding to a specific sub-voltage range (ΔV2) in FIG. 3.

[0087] For each diagnostic round, the type of deterioration feature point can be identified as either a "peak" or a "valley." In this specification, a "peak" may refer to a "local maximum point," and a "valley" may refer to a "local minimum point."

[0088] Referring to Fig. 4, within a specific sub-voltage range (ΔV2), the differential capacitance profiles (DQP1, DQP2, DQP3) have a single peak (C) without a valley. a , C b , C c ) is located, whereas the differential capacity profile (DQP4) has a single valley (C) without a peak. d ) are located. For ease of detection of deterioration feature points, the processor (320) may individually smooth the differential capacity profiles (DQP1, DQP2, DQP3, DQP4) and then execute a detection operation of the deterioration feature points. For smoothing of the differential capacity profiles, one or a combination of two or more of known smoothing techniques such as a moving average filter, an exponential smoothing filter, etc. may be used.

[0089] Peak (C) of differential capacity profile (DQP2) b ) is the peak (C) of the differential capacity profile (DQP1) a ) has a differential capacity value smaller than that of the peak (C) of the differential capacity profile (DQP3). c ) is the peak (C) of the differential capacity profile (DQP2) b ) has a smaller differential capacity value than the valley (C) of the differential capacity profile (DQP4). d ) is the peak (C) of the differential capacity profile (DQP3) c) has a smaller differential capacity value. From this, the inventor of the present invention recognized that as the battery cell (BC) deteriorates, (i) a first deterioration characteristic in which the differential capacity value of a deterioration characteristic point detected within a specific lower voltage range decreases appears first, and (ii) a second deterioration characteristic in which the type of the deterioration characteristic point changes from a peak to a valley appears subsequently.

[0090] FIG. 5 is a flowchart schematically illustrating a battery diagnosis method according to another embodiment of the present invention. The method of FIG. 5 may be repeatedly performed periodically or aperiodically by the battery diagnosis device (302) for at least a portion of the entire life of a battery cell (BC).

[0091] Referring to FIGS. 1 to 5, in step S500, the processor (320) determines whether the battery cell (BC) has an initial differential capacity profile (DQP of FIG. 7). T ), the reference voltage range (ΔV in Fig. 7 R ) can be determined.

[0092] Initial differential capacity profile (DQP) T ) represents the voltage-differential capacity relationship characteristics of the battery cell (BC) at the time of shipment and may be recorded in advance in the memory unit (330). The differential capacity profile (DQP1) shown in FIG. 3 or the differential capacity profile (see FIG. 7) obtained through the first charge / discharge cycle after shipment of the battery cell (BC) may be the initial differential capacity profile (DQP T ) can be used.

[0093] Alternatively, the reference voltage range may be predetermined. In this case, step S500 is not required and can be omitted from the method of FIG. 5.

[0094] In step S510, the processor (320) obtains a differential capacity profile representing the current voltage-differential capacity relationship characteristics of the battery cell (BC) in the reference voltage range.

[0095] In step S520, the processor (320) detects a deterioration feature point located within the reference voltage range from the differential capacity profile determined in step S510.

[0096] In step S530, the processor (320) updates deterioration history information indicating a change history of at least one of the location information and type information of the deterioration feature point based on the detection result of the deterioration feature point. The location information of the deterioration feature point for each diagnostic round includes a differential capacity value of the deterioration feature point and may further include a voltage value of the deterioration feature point. The type information of the deterioration feature point for each diagnostic round may indicate whether the deterioration feature point is identified as a peak or a valley.

[0097] Deterioration history information can indicate how and to what extent the location of a deterioration feature point has changed over a period of time, from a specific point in the past (e.g., the time of shipment) to the present of a battery cell (BC). Furthermore, deterioration history information can indicate whether the type of deterioration feature point remains at a peak or transitions from a peak to a valley.

[0098] In step S540, the processor (320) diagnoses the deterioration status of the battery cell (BC) based on the deterioration history information updated by step S530.

[0099] In step S550, the processor (320) adjusts the allowable charging and discharging conditions for the battery cell (BC) based on the results of the diagnosis of the deterioration state of the battery cell (BC). Step S550 is not essential and may be omitted from the method of FIG. 5 as needed.

[0100] FIG. 6 is a flowchart schematically illustrating sub-steps that can be included in step S500 of FIG. 5, and FIG. 7 is a drawing referenced in explaining the method of FIG. 6.

[0101] Referring to FIGS. 6 and 7, in step S610, the processor (320) determines the initial differential capacity profile (DQP) of the battery cell (BC). T ), a main feature point, which is a peak located within a voltage range of interest, is detected. The voltage range of interest may be a voltage range in which a single peak is previously confirmed.

[0102] Initial differential capacity profile (DQP) T ) is obtained from the capacity-voltage information of the test cell, the main feature point (MC) of Fig. 7 is the peak (C) of Fig. 4 a ) can be directed. In comparison, the initial differential capacity profile (DQP) T ) is obtained from the initial capacity-voltage information of the battery cell (BC), the main feature point (MC) of Fig. 7 is the peak (C) of Fig. 4 a ) may be different.

[0103] At step S620, the processor (320) generates an initial differential capacity profile (DQP) T ), a first auxiliary feature point (SC1) located on a lower voltage side than the main feature point (MC) and a second auxiliary feature point (SC2) located on a higher voltage side than the main feature point are determined (detected).

[0104] At least one of the first auxiliary feature point (SC1) and the second auxiliary feature point (SC2) may be an inflection point. An inflection point of a differential capacity profile is a point where the sign of the slope of the differential capacity profile changes from negative to positive or from positive to negative, and the rate of change of dQ / dV at the inflection point may be 0.

[0105] If two or more inflection points are located on the lower voltage side than the main feature point (MC), the inflection point with the smallest voltage difference from the main feature point (MC) may be determined as the first auxiliary feature point (SC1). Similarly, if two or more inflection points are located on the higher voltage side than the main feature point (MC), the inflection point with the smallest voltage difference from the main feature point (MC) may be determined as the second auxiliary feature point (SC2).

[0106] In step S630, the reference voltage range (ΔV) is the same as the voltage range between the first auxiliary feature point (SC1) and the second auxiliary feature point (SC2). R ) is determined.

[0107] According to the present invention, instead of the entire voltage range, a reference voltage range (ΔV R ) is analyzed, thereby providing a technical advantage of reducing the complexity of the operation while shortening the time required to derive the diagnosis result. The baseline (L) shown in Fig. 7 R ) is a straight line connecting the first auxiliary feature point (SC1) and the second auxiliary feature point (SC2), and is used to identify the tendency of the deterioration feature point, which will be described later with reference to Fig. 8. The reference line (L R ) may be determined by the method according to FIG. 7 or may be pre-recorded in the memory unit (330).

[0108] When the first auxiliary feature point (SC1) and the second auxiliary feature point (SC2) are determined according to the above-described method, a single closed region having a single peak as the main feature point (MC) is formed as the reference line (L). R ) and initial differential capacity profile (DQP) T ) is defined by. Therefore, the baseline (L R ) can be utilized as a clear and efficient diagnostic criterion based on information of deterioration characteristics (i.e., differential capacity value and / or type) that change along with deterioration of a battery cell (BC).

[0109] FIG. 8 is a flowchart schematically illustrating sub-steps that can be included in step S540 of FIG. 5.

[0110] Referring to FIG. 8, in step S810, the processor (320) determines whether the deterioration feature point is a reference line (L R ) is identified from the deterioration history information updated by step S530. For example, referring back to FIG. 4, C a From C b The change in the direction represents the first tendency.

[0111] If the value of step S810 is "Yes", the process proceeds to step S820. If the value of step S810 is "No", the process may proceed to step S830.

[0112] In step S820, the processor (320) diagnoses that a loss of positive electrode capacity of the battery cell (BC) has occurred. In other words, it can be diagnosed that the loss of positive electrode capacity is the main cause of deterioration, and that deterioration due to loss of available lithium has not yet occurred or is at a very minimal level. For reference, the loss of available lithium may also be referred to as 'LLI (Loss of Lithium Inventory)'.

[0113] In step S822, the processor (320) may determine the positive electrode capacity loss rate of the battery cell (BC) based on the difference between the current differential capacity value of the deterioration feature point and the initial differential capacity value. The initial differential capacity value may be the same as the differential capacity value of the main feature point (MC). The processor (320) may determine the positive electrode capacity loss rate of the battery cell (BC) using first relationship data (indicating a correspondence between the differential capacity difference and the positive electrode capacity loss rate) pre-recorded in the memory unit (330) so as to be associated with the first tendency.

[0114] In step S830, the processor (320) determines whether the deterioration feature point is a reference line (L R ) at the lower side of the reference line (LR ) is identified from the deterioration history information updated by step S530. The identification condition of the second tendency is that (i) the deterioration feature point is located at the reference line (L R ) may include at least one of (i) shifting from the upper side to the lower side and (ii) switching the type of the deterioration feature point from a peak to a valley. For example, referring back to FIG. 4, C c From C d Change to and / or C b From C c A change in the value indicates a second tendency. If the value of step S830 is "Yes", the process proceeds to step S840. If the value of step S830 is "No", the method according to FIG. 8 may be terminated.

[0115] In step S840, the processor (320) determines that additional available lithium loss of the battery cell (BC) has occurred. That is, it can be determined that, in addition to the positive electrode capacity loss, degradation due to the available lithium loss has significantly progressed or is showing signs of worsening. The available lithium loss may be a type of degradation that occurs subsequent to the positive electrode capacity loss. A second tendency indicating that the degradation is already accelerating or is showing signs of accelerating can be identified from the degradation history information by additionally generating the available lithium loss on top of the positive electrode capacity loss that is already occurring.

[0116] According to the results of the disassembly and analysis of a number of test cells by the inventor of the present invention, when the first tendency was identified, the loss of available lithium was not confirmed or was very minimal, but when the second tendency was identified, the loss of available lithium was definitely confirmed.

[0117] In step S842, the processor (320) calculates the current differential capacity value of the deterioration feature point and the reference line (L R) can be used to determine the available lithium loss rate of the battery cell (BC). The current differential capacity value of the degradation feature point and the baseline (L R ) can be referred to as the differential capacity difference.

[0118] The baseline (L) is compared with the current differential capacity value of the deterioration feature point. R ) is the differential capacity value, which is the vertical line having the voltage value of the deterioration feature point and the reference line (L R ) may be the differential capacity value at the intersection between them.

[0119] Baseline (L R ) can be determined depending on the deterioration feature point. Specifically, the reference line (L R ) may be a differential capacity value mapped to the same voltage value as the voltage value of the deterioration feature point. Therefore, the deterioration feature point may be mapped to the reference line (L R ) refers to the reference line (L) at the same voltage value as the deterioration characteristic point. R ) may mean that the differential capacity value of the deterioration feature point is smaller than the differential capacity value of the deterioration feature point. Similarly, the deterioration feature point may be smaller than the reference line (L R ) is the reference line (L) at the same voltage value as the deterioration feature point. R ) may mean that the differential capacity value is greater than the differential capacity value of the deterioration feature point.

[0120] The processor (320) can determine the available lithium loss rate of the battery cell (BC) by using second relationship data (indicating a correspondence between the differential capacity difference and the available lithium loss rate) pre-recorded in the memory unit (330) to be associated with the second tendency.

[0121] Steps S832 and S842 are not essential, and at least one of them can be omitted from the method of FIG. 8.

[0122] FIG. 9 is a flowchart schematically illustrating sub-steps that may be included in step S550 of FIG. 5.

[0123] Referring to FIG. 9, in step S910, the processor (320) determines whether only positive electrode capacity loss has occurred among positive electrode capacity loss and available lithium loss based on the results of the diagnosis executed in step S540. If the value of step S910 is “Yes,” the process may proceed to step S920. If the value of step S910 is “No,” it means that both positive electrode capacity loss and available lithium loss have been diagnosed to have occurred. If the value of step S910 is “No,” the process may proceed to step S930.

[0124] In step S920, the processor (320) adjusts the allowable charge / discharge conditions for the battery cell (BC) according to the first protection logic. The allowable charge / discharge conditions may be data defining an allowable value for at least one of the upper charge voltage limit, the lower discharge voltage limit, the maximum charge current, the maximum discharge current, the maximum charge depth (the maximum chargeable SOC), the maximum discharge depth (the minimum dischargeable SOC), and the maximum temperature of the battery cell (BC).

[0125] The first protection logic may include an operation that reduces at least one item of the previous allowable charge / discharge conditions by a first predetermined percentage or a first predetermined value. For example, each time the first protection logic is executed, the upper charge limit voltage may be reduced by 1%.

[0126] In step S930, the processor (320) adjusts the allowable charge / discharge conditions for the battery cell (BC) according to the second protection logic.

[0127] The second protection logic may include an operation to lower at least one item of the previous allowable charge / discharge condition by a second predetermined percentage (greater than the first predetermined percentage) or by a second predetermined value (greater than the first predetermined value). For example, each time the second protection logic is executed, the upper charge limit voltage may be reduced by 2%.

[0128] The second protection logic may include additional downgrade operations for items other than those downgraded by the first protection logic. For example, each time the second protection logic is executed, the first protection logic, which reduces the upper charge limit voltage by 1%, may be executed by default, and in addition, an operation may be executed to lower the maximum charge current and maximum discharge current by 3% each.

[0129] The embodiments of the present invention described above are not implemented only through devices and methods, but may also be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded, and such implementation can be easily implemented by an expert in the technical field to which the present invention belongs based on the description of the embodiments described above.

[0130] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0131] In addition, the present invention described above is not limited to the above-described embodiments and the attached drawings, and all or part of each embodiment may be selectively combined and configured so that various modifications can be made, as those skilled in the art can make various substitutions, modifications, and changes within the scope of the technical idea of ​​the present invention.

Claims

1. A step of detecting a deterioration feature point located within a reference voltage range from a differential capacity profile representing the voltage-differential capacity relationship characteristics of a battery cell in a reference voltage range; A step of updating deterioration history information indicating a change history of at least one of the location information and type information of the deterioration feature point based on the detection result of the deterioration feature point; and A step of diagnosing the deterioration status of the battery cell based on the updated deterioration history information; A battery diagnostic method comprising:

2. In paragraph 1, A step of curve fitting a set of voltage-current data acquired while the voltage of the battery cell varies over the reference voltage range to determine a voltage profile of the battery cell for the reference voltage range; and A step of differentiating the voltage profile to obtain the differential capacity profile; A battery diagnostic method further comprising:

3. In paragraph 1, The step of diagnosing the deterioration status of the above battery cell is: A step of diagnosing that a loss of positive electrode capacity of the battery cell has occurred when a first tendency of the above deterioration feature point approaching the baseline from the upper side of the baseline is identified from the updated deterioration history information; A battery diagnostic method comprising:

4. In paragraph 3, The step of diagnosing the deterioration status of the above battery cell is: When it is diagnosed that a positive electrode capacity loss has occurred in the battery cell, a step of comparing the current differential capacity value of the deterioration feature point with the initial differential capacity value to determine a positive electrode capacity loss rate of the battery cell; A battery diagnostic method further comprising:

5. In paragraph 1, The step of diagnosing the deterioration status of the above battery cell is: A step of diagnosing that additional available lithium loss has occurred along with a loss of anode capacity of the battery cell, when a second tendency of the deterioration feature point moving away from the baseline on the lower side of the baseline is identified from the updated deterioration history information; A battery diagnostic method comprising:

6. In paragraph 5, The step of diagnosing the deterioration status of the above battery cell is: When it is diagnosed that the available lithium loss of the battery cell has occurred, a step of determining the available lithium loss rate of the battery cell based on the difference between the current differential capacity value of the deterioration feature point and the differential capacity value of the reference line; A battery diagnostic method further comprising:

7. In any one of paragraphs 3 to 6, A step preceding the step of determining a differential capacity profile of a battery cell for the above reference voltage range, the step of determining the reference voltage range based on the initial differential capacity profile of the battery cell; A battery diagnostic method further comprising:

8. In paragraph 7, The step of determining the above reference voltage range is: A step of detecting a main feature point, which is a peak located within a predetermined voltage range of interest, from the above initial differential capacity profile; A step of detecting a first auxiliary feature point located on a lower voltage side than the main feature point and a second auxiliary feature point located on a higher voltage side than the main feature point; and A step of determining the reference voltage range to be the same as the voltage range between the first auxiliary feature point and the second auxiliary feature point; A battery diagnostic method comprising:

9. In paragraph 8, The above baseline is, A battery diagnosis method, wherein the straight line passes through the first auxiliary feature point and the second auxiliary feature point.

10. A processor for generating a differential capacity profile representing the voltage-differential capacity relationship characteristics of a battery cell over a reference voltage range, The above processor, From the above differential capacity profile, a deterioration feature point located within the reference voltage range is detected, Based on the detection result of the above deterioration feature point, deterioration history information indicating the change history of at least one of the location information and type information of the above deterioration feature point is updated, A battery diagnostic device that diagnoses the deterioration status of the battery cell based on the updated deterioration history information.

11. In paragraph 10, The above processor, A battery diagnostic device that diagnoses that a loss of positive electrode capacity of the battery cell has occurred when a first tendency of the above-mentioned deterioration characteristic point approaching the reference line from the upper side of the reference line is identified from the updated deterioration history information.

12. In paragraph 10, The above processor, A battery diagnostic device that diagnoses that additional available lithium loss has occurred along with a loss of anode capacity of the battery cell when a second tendency of the deterioration characteristic point moving away from the baseline on the lower side of the baseline is identified from the updated deterioration history information.

13. In paragraph 11, The above processor, A battery diagnostic device, which determines the reference voltage range based on the initial differential capacity profile of the battery cell prior to the operation of determining the differential capacity profile.

14. A battery pack comprising a battery diagnostic device according to any one of claims 10 to 13.

15. A battery system comprising a battery diagnostic device according to any one of claims 10 to 13.

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