KR20240006307A - Battery cell degradation diabnosis method and battery system using the same - Google Patents

Abstract

The battery system generates an actual potential-capacity profile according to a cell current flowing in a first battery cell among a plurality of battery cells and a cell voltage of the first battery cell, and an initial anode profile and an initial cathode profile corresponding to the cell current. A simulated potential-capacity profile is generated based on the target battery according to the anode offset and cathode offset for each of the initial anode profile and the initial cathode profile so that the actual potential-capacity profile and the simulated potential-capacity profile match. It may include a main control unit that determines the degree of cell deterioration. The initial anode profile and the initial cathode profile may be determined according to a first actual potential-capacity profile generated initially of the first battery cell.

Description

Battery cell deterioration diagnosis method and battery system using the same {BATTERY CELL DEGRADATION DIABNOSIS METHOD AND BATTERY SYSTEM USING THE SAME}

This specification relates to a method for diagnosing battery cell deterioration and a battery system using the same.

Secondary batteries (hereinafter referred to as batteries) are commonly applied to portable devices, electric vehicles (EVs) or energy storage systems (ESS) driven by electrical power sources, and provide more efficient battery management. To this end, research and development on battery management systems (BMS), battery balancing circuits, and relay circuits are actively underway.

In particular, safety and long life characteristics are required for lithium secondary batteries (hereinafter referred to as lithium batteries) applied to automobile batteries. However, during a lithium battery cycle, battery sudden drops may occur, such as gas generation, lithium plating, and instantaneous voltage drop when electrolyte is decomposed. Therefore, a method is needed to distinguish whether a lithium battery is deteriorating before a sharp decline occurs during the lithium battery cycle.

The object of the present invention is to provide a battery cell deterioration diagnosis method that can determine the degree of battery deterioration and a battery system using the same.

A battery system according to one aspect of the invention includes a battery pack including a plurality of battery cells, a cell monitoring IC that measures a plurality of cell voltages of the plurality of battery cells, a current sensor that detects a battery current flowing in the battery pack, and generating an actual potential-capacity profile according to the cell current flowing in a first battery cell among the plurality of battery cells and the cell voltage of the first battery cell, based on the initial anode profile and the initial cathode profile corresponding to the cell current. A simulated potential-capacity profile is generated, and the target battery cell is adjusted according to the anode offset and cathode offset for each of the initial anode profile and the initial cathode profile so that the actual potential-capacity profile and the simulated potential-capacity profile match. It may include a main control unit that determines the degree of deterioration. The initial anode profile and the initial cathode profile may be determined according to a first actual potential-capacity profile generated initially of the first battery cell.

The main control unit derives a first simulation potential-capacity profile from a first reference anode profile and a first reference cathode profile corresponding to the first cell current flowing in the first battery cell at the beginning of the first battery cell, , generate the first measured potential-capacity profile based on the first cell current and the cell voltage of the first battery cell, and generate the first measured potential-capacity profile based on the first simulated potential-capacity profile and the first measured potential-capacity profile. The initial anode profile and the initial cathode profile may be derived by correcting the first reference anode profile and the first reference cathode profile.

The main control unit is based on a first actual measured capacity-potential differential profile showing a voltage change (dV/dQ) in response to a change in capacity based on the first actual measured potential-capacitance profile and the first simulated potential-capacitance profile. Generate a first simulated capacity-potential differential profile showing the voltage change (dV/dQ) for the capacity change according to the capacity, and generate the capacity change (dQ/dV) for the voltage change based on the first actual measured potential-capacitance profile. Generating a first actual potential-capacitance differential profile shown according to voltage and a first simulated potential-capacitance profile showing the change in capacity (dQ/dV) with respect to voltage change based on the first simulated potential-capacitance profile according to voltage, The first measured capacitance-potential differential profile, the first simulated capacitance-potential differential profile, the first measured potential-capacitance differential profile, and the first simulated potential-capacitance profile are used to determine the first reference anode profile. An anode offset can be derived, and a cathode offset with respect to the first reference cathode profile can be derived.

The main control unit matches the first measured capacitance-potential differential profile and the first simulated capacitance-potential differential profile, and matches the first measured capacitance-capacitance differential profile with the first simulated potential-capacitance profile, An increase/decrease operation to increase or decrease the first reference anode profile and the first reference cathode profile and a left/right movement operation to move it to the left or right may be repeated, and the anode offset and the cathode offset may be derived according to the repetition results. there is.

The main control unit displays a voltage change (dV/dQ) for a capacity change based on the measured potential-capacitance profile according to the capacity, and a measured capacity-potential differential profile and a voltage change for the capacity change based on the simulated potential-capacitance profile. Generate a simulated capacitance-potential differential profile showing (dV/dQ) according to capacitance, and an actual potential-capacitance differential profile showing the change in capacity (dQ/dV) according to voltage in response to a voltage change based on the actual potential-capacitance profile. and generate a simulated potential-capacitance profile showing the change in capacity (dQ/dV) according to voltage based on the simulated potential-capacitance profile, the measured capacity-potential differential profile, the simulated capacity-potential differential profile, Using the measured potential-capacitance differential profile and the simulated potential-capacitance profile, an anode offset for the initial anode profile can be derived, and a cathode offset for the initial cathode profile can be derived.

The main control unit is configured to match the measured capacitance-potential differential profile and the simulated capacitance-potential differential profile, and to match the measured potential-capacitance differential profile and the simulated potential-capacitance profile, so that the initial anode profile and the initial cathode are matched. The increase/decrease operation to increase or decrease the profile and the left/right movement movement to move it to the left or right are repeated, and the anode offset and the cathode offset can be derived according to the repetition results.

The main control unit is configured to control an anode degradation degree based on a reduction rate according to an increase/decrease amount of the anode offset, a cathode degradation degree based on a decrease rate according to an increase/decrease amount of the cathode offset, and a left/right movement amount of the anode offset and a left/right movement amount of the cathode offset. The degree of cell degradation can be determined based on loss of lithium inventory (LLI).

The main control unit may calculate the cell degradation degree by adding the LLI to a larger value of the anode degradation degree and the cathode degradation degree.

The main control unit may calculate the LLI based on the degree of discrepancy between the left and right movement amount of the anode offset and the left and right movement amount of the cathode profile.

A method for diagnosing battery cell deterioration according to another feature of the invention includes generating a first actual measured potential-capacity profile for an initial cell according to a first cell current flowing in the initial cell and a cell voltage of the initial cell, the first Deriving a first simulated potential-capacitance profile by combining a reference anode profile and a reference cathode profile corresponding to a cell current, the reference anode such that the first actual measured potential-capacitance profile and the first simulated potential-capacitance profile match. generating an initial anode profile and an initial cathode profile by correcting the profile and the reference cathode profile, generating an actual potential-capacity profile according to a cell current flowing in a battery cell and a cell voltage of the battery cell, generating a simulated potential-capacitance profile based on the corresponding initial anode profile and the initial cathode profile; It may include deriving an anode offset and a cathode offset, and determining a degree of degradation of the battery cell according to the anode offset and the cathode offset.

The step of generating the initial anode profile and the initial cathode profile includes generating a first measured capacity-potential differential profile showing the voltage change (dV/dQ) in response to the change in capacity based on the first measured potential-capacitance profile according to the capacity. generating a first measured potential-capacitance differential profile showing the change in capacity (dQ/dV) with respect to voltage change based on the first measured potential-capacitance profile according to voltage, the first simulated potential-capacitance profile; Generating a first simulated capacity-potential differential profile showing a voltage change (dV/dQ) for a change in capacity based on the capacity, a change in capacity (dQ/ generating a first simulated potential-capacitance profile representing dV) as a function of voltage, and the first measured capacitance-potential differential profile, the first simulated capacitance-potential differential profile, the first measured potential-capacitance differential profile, and deriving an anode offset with respect to the reference anode profile using the first simulated potential-capacitance profile and deriving a cathode offset with respect to the reference cathode profile.

In the step of deriving the anode offset and the cathode offset, the first measured capacitance-potential differential profile and the first simulated capacitance-potential differential profile are matched, and the first measured potential-capacitance differential profile and the first simulated capacitance differential profile are matched. Repeating an increase/decrease operation to increase or decrease the reference anode profile and the reference cathode profile and a left/right movement to move the reference anode profile and the reference cathode profile to the left or right so that the potential-capacitance profile matches, and the anode offset and the cathode according to the results of the repetition. It may include the step of deriving an offset.

The step of deriving the anode offset and the cathode offset includes generating a measured capacitance-potential differential profile showing a voltage change (dV/dQ) for a capacitance change based on the measured potential-capacitance profile according to the capacitance, the measured potential-capacitance profile comprising: Generating an actual potential-capacitance differential profile representing the capacity change (dQ/dV) for a voltage change based on the potential-capacitance profile according to voltage, the voltage change (dV/ Generating a simulated capacity-potential differential profile showing dQ) according to capacity, generating a simulated potential-capacitance profile showing the change in capacity (dQ/dV) according to voltage based on the simulated potential-capacitance profile. Step, and deriving the anode offset with respect to the initial anode profile using the measured capacitance-potential differential profile, the simulated capacitance-potential differential profile, the measured potential-capacitance differential profile, and the simulated potential-capacitance profile, and deriving the cathode offset with respect to the initial cathode profile.

Deriving the anode offset with respect to the initial anode profile and deriving the cathode offset with respect to the initial cathode profile includes matching the measured capacitance-potential differential profile with the simulated capacitance-potential differential profile, and - repeating an increase/decrease operation to increase or decrease the initial anode profile and the initial cathode profile and a left/right movement to move the initial anode profile and the initial cathode profile to the left or right so that the capacity differential profile and the simulated potential-capacitance profile match, and the repetition result and deriving the anode offset and the cathode offset accordingly.

Determining the degree of degradation of the battery cell includes determining a degree of anode degradation based on a reduction rate according to an increase or decrease in the anode offset, determining a degree of cathode degradation based on a decrease rate according to an increase or decrease in the cathode offset, Calculating loss of lithium inventory (LLI) based on the left-right movement amount of the anode offset and the left-right movement amount of the cathode offset, and calculating the cell degradation degree based on the anode degradation degree, the cathode degradation degree, and the LLI. It may include steps.

Calculating the cell degradation degree may include calculating the cell degradation degree by adding the LLI to a larger value of the anode degradation degree and the cathode degradation degree.

Calculating the cell deterioration degree may further include calculating the LLI based on a degree of discrepancy between the left and right movement amount of the anode offset and the left and right movement amount of the cathode profile.

The present invention provides a battery cell deterioration diagnosis method that can determine the degree of battery deterioration and obtain information about electrodes that cause deterioration, and a battery system using the same.

1 is a diagram schematically showing a battery system according to an embodiment.
FIG. 2 is a graph showing a reference anode profile, a reference cathode profile, an actual measured potential-capacitance profile, and a simulated potential-capacitance profile for explaining an embodiment.
FIG. 3 is a diagram showing the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 2.
FIG. 4 is a graph showing a profile showing the voltage change (dV/dQ) for capacity change based on each of the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 3 according to capacity.
FIG. 5 is a graph showing a profile showing capacity conversion (dQ/dV) for voltage change based on each of the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 3 according to voltage.
FIG. 6 is a graph showing a correction reference anode profile, a correction reference cathode profile, an actual measured potential-capacitance profile, and a correction simulation potential-capacitance profile to explain an embodiment.
FIG. 7 is a diagram showing the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 6.
FIG. 8 is a graph showing a profile showing the voltage change (dV/dQ) for capacity change based on each of the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 7 according to capacity.
FIG. 9 is a graph showing a profile showing capacity conversion (dQ/dV) for voltage change based on the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 7, respectively, according to voltage.
Figure 10 is a flowchart showing a method for determining the degree of deterioration of a target battery cell according to an embodiment.
Figure 11 is a graph showing a first measured potential-capacitance profile and cell current according to an embodiment.

The suffixes “module” and/or “part” for components used in the following description are given or used interchangeably only for the ease of preparing the specification, and do not have distinct meanings or roles in themselves. In addition, terms such as "... unit", "... unit", and "module" used in the specification refer to a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. there is.

Additionally, in describing the embodiments disclosed in this specification, if it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in this specification, the detailed descriptions will be omitted. In addition, the attached drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the attached drawings, and all changes included in the spirit and technical scope of the present invention are not limited. , should be understood to include equivalents or substitutes.

Terms containing ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

1 is a diagram schematically showing a battery system according to an embodiment.

In Figure 1, an external device (2) is connected between both output terminals (P+, P-) of the battery system (1), and when the relays (21, 22) are closed, the battery pack (10) and the external device (2) can be electrically connected. In FIG. 1, the external device 2 is shown connected to the battery system 1, but this is an example to aid understanding of the battery system 1 and the invention is not limited thereto.

When the external device 2 is an electrical load, the battery system 1 operates as a power source that supplies energy to the electrical load 2 and can be discharged. The electronic load may be a vehicle or an energy storage system (ESS), and the vehicle may be, for example, an electric vehicle, a hybrid vehicle, or smart mobility. When the external device 2 is a charger, the battery system 1 can be charged by receiving energy from the power system through the charger 2.

The battery system 1 includes a battery pack 10, two relays 21 and 22, a current sensor 23, and a battery management system (BMS) 100. The BMS 20 includes a cell monitoring IC 110, a main control unit (MCU) 120, and a memory 130.

The battery pack 10 includes a plurality of battery cells 10_1-10_4 connected in series. In Figure 1, the battery pack 10 is shown as including four battery cells (10_1-10_4) connected in series, but this is an example and the invention is not limited thereto. For example, five or more battery cells may be connected in series, or two or more battery cells connected in parallel may be connected in series.

The relay 21 is connected between the positive electrode and the output terminal (P+) of the battery pack 10, and the relay 22 is connected between the negative electrode and the output terminal (P-) of the battery pack 10, and the BMS (100 ) The opening and closing of the relays 21 and 22 can be controlled according to the control of the MCU 120. For example, the MCU 120 generates the enable level relay control signals SR1 and SR2 and transmits them to the relays 21 and 22, and the relays 21 and 22 generate the enable level relay control signals SR1. , can be closed by SR2). Alternatively, the MCU 120 generates disable level relay control signals SR1 and SR2 and transmits them to the relays 21 and 22, and the relays 21 and 22 generate disable level relay control signals SR1 and SR2. ) can be opened by. During charging or discharging of the battery pack 10, the relays 21 and 22 are closed to form a charging current path or a discharging current path.

The current sensor 23 may detect the current flowing in the battery pack 10 and transmit a current detection signal (IS) indicating the detected current to the MCU 120.

The BMS 20 is connected to a plurality of battery cells 10_1-10_4, and is based on information such as the cell voltage of each of the plurality of battery cells 10_1-10_4 and the battery current of the battery pack 10. 10) The charging and discharging current can be controlled. Although not shown in FIG. 1, the battery system 1 may further include a cell balancing circuit connected to a plurality of battery cells 10_1-10_4. The BMS 20 may control a cell balancing operation for the plurality of battery cells 10_1-10_4 based on the cell voltages of the plurality of battery cells 10_1-10_4.

The cell monitoring IC 110 measures the cell voltage of each of the plurality of battery cells 10_1-10_4 at each measurement cycle and transmits a cell voltage detection signal (CVS) indicating the measured plurality of cell voltages to the MCU 120. You can. The MCU 120 estimates the state of charge (SOC) for each of the plurality of battery cells 10_1-10_4 based on the plurality of battery cell voltages and the current flowing through the plurality of battery cells (hereinafter referred to as cell current). And, charging and discharging of the battery pack 10 can be controlled according to the estimated SOC. In the following specification, cell current refers to the charging current or discharging current flowing in any battery cell constituting the battery pack 10. In Figure 1, a plurality of battery cells (10_1-10_4) constituting the battery pack 10 are connected in series, so that the current flowing in the battery pack 10 and the current flowing in the plurality of battery cells (10_1-10_4) are the same. You can. However, the battery pack 10 may be implemented by connecting a plurality of two or more battery cells connected in parallel in series, or by connecting a plurality of battery cells connected in series in parallel, so that the current flowing in the battery pack 10 and each battery cell The cell current flowing through may be different.

The BMS 20 according to some embodiments may store a reference anode profile and a reference cathode profile for each of a plurality of charge currents and a plurality of discharge currents. A plurality of charging currents may have different C-rates, and a plurality of discharging currents may also have different C-rates. C-rate refers to the charging or discharging speed when charging or discharging a battery. The unit of C-rate is [C], and C-rate can be calculated by dividing the charging current or discharging current by the battery's rated capacity value (Ah). In the specification, the plurality of reference anode profiles and the plurality of reference cathode profiles stored by the BMS 20 are referred to as “a plurality of reference anode profiles” and “a plurality of reference cathode profiles.” The memory 130 of the BMS 100 may store a plurality of reference anode profiles and a plurality of reference cathode profiles. The MCU 120 may be installed with software implemented as a set of a plurality of control commands that implement a method for diagnosing battery cell deterioration. In this specification, operations performed by the MCU 120 according to installed software may be a plurality of steps that constitute a method for diagnosing the degree of battery cell deterioration. In other words, the description of the operation of the MCU 120 may be a description of a method for diagnosing battery cell deterioration.

The MCU 120 corrects each of the reference anode profile and reference cathode profile according to a certain cell current so that the actual potential-capacitance profile and the simulated potential-capacitance profile for the initial full cell according to a certain cell current match. You can. In this specification, “initial” means a state in which the charging cycle and discharging cycle for the battery pack 10 have not progressed. Therefore, an initial full cell may mean a full cell with a charge/discharge cycle of 0. In order to generate an actual potential-capacity profile for the initial complete cell, the MCU 120 calculates the capacity for the initial complete cell by integrating the cell current, and combines the cell voltage information transmitted from the cell monitoring IC 110 with the calculated capacity. It is possible to generate a measured potential-capacitance profile for the initial complete cell using . The degree to which the reference anode profile changes due to correction of the MCU 120 is called an anode offset, and the degree to which the reference cathode profile changes is called a cathode offset. For convenience of explanation, “cell” hereinafter may mean “complete cell.” In this specification, matching between two profiles means that the difference between the two profiles is less than or equal to a corresponding predetermined threshold in the entire range of the two profiles, and “anode offset” refers to an increase/decrease with respect to the corresponding one of a plurality of reference anode profiles. It includes a degree (hereinafter referred to as an increase/decrease amount) and a left/right movement amount, and the “cathode offset” may include an increase/decrease amount and a left/right movement amount for a corresponding one of a plurality of reference cathode profiles.

FIG. 2 is a graph showing a reference anode profile, a reference cathode profile, an actual measured potential-capacitance profile, and a simulated potential-capacitance profile for explaining an embodiment.

The actual potential-capacity profile (OP) shown in FIG. 2 is the voltage when charging a battery cell with a predetermined cell current (hereinafter, first cell current, for example, 1/3C) for the initial cell used for the first time. It shows the change in voltage (voltage at both ends of the cell) according to the change in capacity. The reference anode profile (CP) is a reference anode profile for a charging current equal to the first cell current among a plurality of reference anode profiles, and the reference cathode profile (AP) is a reference anode profile for a charging current equal to the first cell current among a plurality of reference cathode profiles. This is the reference cathode profile, and the simulation potential-capacitance profile (SP) can be derived by combining the reference anode profile (CP) and the reference cathode profile (AP). For example, in a simulated potential-capacity profile, the difference between the voltage of a reference anode profile (CP) for a capacity and the voltage of a reference cathode profile (AP) for the same capacity may be the potential for that capacity.

As shown in FIG. 2, a difference occurs between the measured potential-capacitance profile (CP) and the simulated potential-capacitance profile (SP). Such differences may occur due to differences in characteristics between multiple initial cells produced on the same process line. The MCU 120 may correct each of the reference anode profile (CP) and the reference cathode profile (AP) so that the measured potential-capacitance profile (CP) and the simulated potential-capacitance profile (SP) for the initial cell match. The MCU 120 may derive an anode offset and a cathode offset that match the measured potential-capacitance profile (CP) and the simulated potential-capacitance profile (SP) for the initial cell.

FIG. 3 is a diagram showing the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 2.

FIG. 4 is a graph showing a profile showing the voltage change (dV/dQ) for capacity change based on each of the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 3 according to capacity.

In Figure 4, the profile (CV1) showing the voltage change (dV/dQ) for capacity change based on the actual measured potential-capacitance profile (OP) according to the capacity is called the actual measured capacity-potential differential profile (CV1), and the simulated potential-capacitance profile (OP) is called the measured capacity-potential differential profile (CV1). The profile (CV2) showing the voltage change (dV/dQ) for the capacity change based on the capacity profile (SP) according to the capacity is called the simulation capacity-potential differential profile (CV2).

FIG. 5 is a graph showing a profile showing capacity conversion (dQ/dV) for voltage change based on each of the measured potential-capacitance profile and the simulated potential-capacitance profile shown in FIG. 3 according to voltage.

In Figure 5, the profile (VC1) showing the capacity change (dQ/dV) according to the voltage change based on the measured potential-capacitance profile (OP) is called the measured potential-capacitance differential profile (VC1), and the simulated potential-capacitance profile (OP) is called the measured potential-capacitance differential profile (VC1). The profile (VC2) showing the capacity change (dQ/dV) according to the voltage change based on the capacity profile (SP) is called the simulation potential-capacitance profile (VC2).

As shown in Figure 3, there is a difference between the measured potential-capacitance profile (CP) and the simulated potential-capacitance profile (SP). Due to this difference, as shown in Figure 4, there is a difference between the measured capacitance-potential differential profile (CV1) and the simulated capacitance-potential differential profile (CV2), and as shown in Figure 5, the measured potential-capacitance differential profile A difference arises between (VC1) and the simulated potential-capacitance differential profile (VC2).

The MCU 120 performs an increase/decrease operation to increase or decrease each of the reference anode profile (CP) and reference cathode profile (SP) shown in FIG. 2, and a left/right movement operation to move the reference anode profile (CP) and the reference cathode profile (SP) to the left or right, respectively, as shown in FIGS. 4 and 5. This can be repeated until the two corresponding profiles are matched. That is, when the difference in the entire range (e.g., approximately 0 to 60 Ah capacity) between the actual measured capacity-potential profile and the simulated capacity-potential profile is less than or equal to the corresponding predetermined threshold, the measured capacity-potential profile and the simulated capacity-potential profile This can be seen as matching. When the difference in the entire range (e.g., approximately 3.4V to 4.2V) between the measured potential-capacitance profile and the simulated potential-capacitance profile is less than or equal to a corresponding predetermined threshold, the measured potential-capacitance profile and the simulated potential-capacitance profile This can be seen as matching.

The MCU 120 matches the measured capacitance-potential differential profile (CV1) and the simulated capacitance-potential differential profile (CV2) and matches the measured potential-capacitance differential profile (VC1) and the simulated potential-capacitance differential profile (VC2). The increase/decrease operation and the left/right movement for the reference anode profile (CP) and the reference cathode profile (SP) are repeated. The MCU 120 may derive an anode offset according to the increase/decrease amount and left/right movement amount of the reference anode profile (CP) and a cathode offset depending on the increase/decrease amount and left/right movement amount of the reference cathode profile (SP) according to the repetition results. The MCU 120 may derive an anode offset and a cathode offset for each of the plurality of reference anode profiles and the plurality of reference cathode profiles to remove the initial error of the plurality of reference anode profiles and the plurality of reference cathode profiles for the initial cell. .

For example, through repetition of an increase/decrease operation and a left/right movement operation, the MCU 120 may derive an anode offset that increases the reference anode profile (CP) by 0.5% and shifts it to the left by 0.3%. At this time, 100% means 58Ah, the maximum capacity of the standard anode profile (CP). According to the anode offset, the MCU (120) increases the range (0Ah to 58Ah) of the reference anode profile (CP) by 0.29Ah from the original range (0Ah to 58.29Ah) and moves 0.174Ah to the left (-0.174Ah). It can be calibrated with the reference anode profile (CP1) having ~58.116Ah). Additionally, through repetition of the increase/decrease operation and the left/right movement operation, the MCU 120 can derive a cathode offset that shifts the reference cathode profile (AP) to the right by 2.3% without increasing it. At this time, 100% means 58Ah, the maximum capacity of the standard cathode profile (AP). The MCU 120 is calibrated to the reference cathode profile (AP1) having a range (1.134Ah to 59.134Ah) shifted by 1.134Ah to the right without an increase in the range (0Ah to 58Ah) of the reference cathode profile (AP) according to the anode offset. can do. The MCU 120 may derive a simulation potential-capacitance profile (SP1) based on the difference between the corrected reference anode profile (CP1) and the corrected reference cathode profile (AP1).

FIG. 6 is a graph showing a correction reference anode profile, a correction reference cathode profile, an actual measured potential-capacitance profile, and a correction simulation potential-capacitance profile to explain an embodiment.

FIG. 7 is a diagram showing the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 6.

As shown in FIGS. 6 and 7, it can be seen that the correction simulation potential-capacitance profile (SP1) and the actual measured potential-capacitance profile (OP) are matched almost identically.

FIG. 8 is a graph showing a profile showing the voltage change (dV/dQ) for capacity change based on each of the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 7 according to capacity.

As shown in Figure 8, the corrected simulated capacitance-potential showing the voltage change (dV/dQ) for the capacitance change based on the measured capacitance-potential differential profile (CV1) and the corrected simulation potential-capacitance profile (SP1) according to the capacitance. It can be seen that the deviation between the differential profiles (CV3) is smaller than the deviation between the two profiles (CV1 and CV2) shown in FIG. 4.

FIG. 9 is a graph showing a profile showing capacity conversion (dQ/dV) for voltage change based on the measured potential-capacitance profile and the corrected simulation potential-capacitance profile shown in FIG. 7, respectively, according to voltage.

As shown in Figure 9, between the measured potential-capacitance differential profile (VC1) and the profile (VC3) showing the capacity change (dQ/dV) according to voltage based on the corrected simulation potential-capacitance profile (SP1). It can be seen that the deviation is smaller than the deviation between the two profiles (VC1 and VC2) shown in FIG. 5.

In this way, after the anode offset and cathode offset for the initial cell are determined, the MCU 120 uses the correction reference anode profile (CP1) and the correction reference cathode profile (AP1) as reference profiles for determining the degree of degradation for the corresponding initial cell. You can set it. Hereinafter, the correction reference anode profile (CP1) is referred to as the initial anode profile (CP1), and the correction reference cathode profile (AP1) is referred to as the initial cathode profile (AP1). The corrected simulated potential-capacitance profile (SP1) based on the initial anode profile (CP1) and the initial cathode profile (AP1) is called the simulated potential-capacitance profile (SP1). The simulated potential-capacity profile may be a profile corresponding to 100% SOH at the BOL (Beginning of Life) of the battery cell. The MCU 120 may transfer the initial anode profile (CP1), the initial cathode profile (AP1), and the simulated potential-capacitance profile (SP1) to the memory 130, and the memory 130 may store them. The MCU 120 may generate a plurality of initial anode profiles and a plurality of cathode initial profiles by performing correction on the initial cell for the plurality of reference anode profiles and the plurality of reference cathode profiles.

As the cycle using the battery pack 10 progresses, the MCU 120 derives the actual potential-capacitance profile at some point, and the initial anode required to match the derived actual potential-capacitance profile with the simulated potential-capacitance profile. The degree of deterioration can be determined based on the increase/decrease amount and the left/right movement amount for each of the profile (CP1) and the initial cathode profile (CP2). A certain point in time may be a point in time that is repeated at regular intervals, or may be a point in time that is synchronized with a control command received from the outside to the BMS 100. The MCU 120 may determine the degree of degradation for a certain battery cell (hereinafter, a target battery cell or a first battery cell) among the plurality of battery cells of the battery pack 10 at regular intervals or by an external control command.

Figure 10 is a flowchart showing a method for determining the degree of deterioration of a target battery cell according to an embodiment.

First, the MCU 120 may generate a measured potential-capacity profile for the target battery cell. The MCU 120 calculates the capacity of the target battery cell by accumulating the cell current of the target battery cell, and uses the cell voltage information of the target battery cell transmitted from the cell monitoring IC 110 and the calculated capacity to determine the target battery cell. The actual potential-capacitance profile (OP2) for can be generated (S1). The actual measured potential-capacitance profile generated in step S1 is called the first measured potential-capacitance profile.

Figure 11 is a graph showing a first measured potential-capacitance profile and cell current according to an embodiment.

In FIG. 11, the cell current is shown as a charging current, but the invention is not limited thereto. The actual potential-capacitance profile can be derived through discharge current instead of charge current. As shown in FIG. 11, the cell current (CI) is a constant current, and the first measured potential-capacity profile (OP2) shows the change in capacity of the target battery cell and the change in battery cell voltage according to the cell current.

The MCU 120 derives an initial anode profile and an initial cathode profile corresponding to the cell current (CI) among the plurality of initial anode profiles and the plurality of initial cathode profiles (S2). The initial anode profile and the initial cathode profile derived in step S2 are referred to as the first initial anode profile and the second initial cathode profile.

The MCU 120 generates a simulation potential-capacitance profile (SP2) by combining the first initial anode profile and the second initial cathode profile (S3). The simulation potential-capacitance profile (SP2) derived in step S3 is called the first simulation potential-capacitance profile.

The MCU 120 performs a correction operation on the first initial anode profile and the first initial cathode profile so that the first simulated potential-capacitance profile (SP2) matches the first actual potential-capacitance profile (OP2) (S4) .

For example, the MCU 120 may be configured to include a first actual capacity-potential differential profile based on the first actual potential-capacitance profile (OP2) and a first actual-measurement potential-capacitance differential profile and a first simulated potential-capacitance profile (SP2). A first simulated capacitance-potential differential profile and a first simulated potential-capacitance profile are generated (S41).

The MCU 120 performs an increase/decrease operation to increase or decrease each of the first initial anode profile and the second initial cathode profile, and a left/right movement to move the first initial anode profile and the second initial cathode profile to the left or right (S42).

The MCU 120 calculates the difference d1 between the first measured capacitance-potential differential profile and the first simulated capacitance-potential differential profile (S43) and determines whether the difference d1 is less than or equal to the corresponding predetermined threshold dth1. Do it (S44).

The MCU 120 calculates the difference d2 between the first actual measured potential-capacitance differential profile and the first simulated potential-capacitance differential profile (S45), and determines whether the difference d2 is less than or equal to the corresponding predetermined threshold dth2. Do it (S46).

As a result of the determination in steps S44 and S46, if the difference d1 is greater than the threshold dth1 or the difference d2 is greater than the threshold dth2, step S42 is repeated again.

As a result of determining steps S44 and S46, if the difference d1 is less than or equal to the threshold dth1 and the difference d2 is less than or equal to the threshold dth2, the MCU 120 sets the anode offset for the first initial anode profile in step S42 and The cathode offset with respect to the first initial cathode profile is finally determined, and the deterioration degree of the target battery cell is determined based on the increase/decrease amount and the left and right movement amount of the anode offset with respect to the first initial cathode profile and the cathode offset with respect to the first initial cathode profile, respectively. Decide (S5). The MCU 120 determines the anode reduction rate according to the increase/decrease amount of the anode offset with respect to the first initial anode profile in step S42 as the anode degradation degree, and determines the anode reduction rate according to the increase/decrease amount of the cathode offset with respect to the first initial cathode profile in step S42. The cathode reduction rate can be determined by the cathode degradation degree. The MCU 120 determines the loss of lithium (LLI) for the target battery cell based on the degree of discrepancy between the left and right movement amount of the anode offset with respect to the first initial anode profile and the left and right movement amount of the cathode offset with respect to the first initial cathode profile in step S42. Calculate inventory. For example, the MCU 120 may calculate the LLI by adding the leftward movement amount of the anode offset with respect to the first initial anode profile and the rightward movement amount of the cathode offset with respect to the first initial cathode profile. If the left and right movement amounts of the anode offset with respect to the first initial anode profile and the left and right movement amounts of the cathode offset with respect to the first initial cathode profile are in the same direction, the MCU 120 may calculate the difference between the left and right movement amounts of the two profiles as LLI. The MCU 120 may calculate the deterioration degree by adding the maximum value of the anode degradation degree and the cathode degradation degree and LLI.

According to the present invention, the lithium loss of the positive and negative electrodes constituting the battery cell can be determined using the measured cell current and cell voltage profiles. Additionally, degradation degree comparison between a plurality of battery cells in a battery pack, a degradation degree comparison between a plurality of anodes of a plurality of battery cells, and a degradation degree comparison between a plurality of cathodes of a plurality of battery cells may be performed. Through the above comparison, the relative deterioration advantage and degree of deterioration of the battery pack based on deterioration information can be confirmed.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. It falls within the scope of rights.

1: Battery system
10: Battery pack
100: Battery management system
110: Cell monitoring IC
120: main control unit
130: memory

Claims (17)

A battery pack including a plurality of battery cells;
a cell monitoring IC that measures a plurality of cell voltages of the plurality of battery cells;
a current sensor that detects battery current flowing through the battery pack; and
An actual potential-capacity profile is generated according to the cell current flowing in a first battery cell among the plurality of battery cells and the cell voltage of the first battery cell, based on the initial anode profile and the initial cathode profile corresponding to the cell current. Generate a simulated potential-capacity profile, and degrade the target battery cell according to the anode offset and cathode offset for each of the initial anode profile and the initial cathode profile so that the actual potential-capacity profile and the simulated potential-capacity profile match. It includes a main control unit that determines the degree,
The battery system, wherein the initial anode profile and the initial cathode profile are determined according to a first measured potential-capacity profile initially generated of the first battery cell. According to paragraph 1,
The main control unit,
At the beginning of the first battery cell, a first simulated potential-capacity profile is derived from a first reference anode profile and a first reference cathode profile corresponding to a first cell current flowing in the first battery cell, and Generating the first actual potential-capacity profile based on the current and the cell voltage of the first battery cell, and generating the first reference anode based on the first simulated potential-capacity profile and the first actual potential-capacity profile. A battery system that corrects the profile and the first reference cathode profile to derive the initial anode profile and the initial cathode profile. According to paragraph 2,
The main control unit,
A first measured capacity-potential differential profile showing a voltage change (dV/dQ) for a capacity change based on the first measured potential-capacitance profile according to capacity, and a voltage for a capacity change based on the first simulated potential-capacitance profile. Generate a first simulated capacity-potential differential profile showing the change (dV/dQ) according to capacity,
A first measured potential-capacitance differential profile showing the change in capacity (dQ/dV) with respect to voltage change based on the first measured potential-capacitance profile and the capacity with respect to voltage change based on the first simulated potential-capacitance profile. Generating a first simulated potential-capacitance profile showing the change (dQ/dV) as a function of voltage,
The first measured capacitance-potential differential profile, the first simulated capacitance-potential differential profile, the first measured potential-capacitance differential profile, and the first simulated potential-capacitance profile are used to determine the first reference anode profile. Deriving an anode offset and deriving a cathode offset relative to the first reference cathode profile. According to paragraph 3,
The main control unit,
The first reference anode is such that the first measured capacitance-potential differential profile matches the first simulated capacitance-potential differential profile, and the first measured potential-capacitance differential profile matches the first simulated potential-capacitance profile. A battery system that repeats an increase/decrease operation to increase or decrease the profile and the first reference cathode profile, and a left/right movement operation to move it to the left or right, and derives the anode offset and the cathode offset according to the repetition results. According to paragraph 1,
The main control unit,
The measured capacity-potential differential profile showing the voltage change (dV/dQ) for the capacity change based on the measured potential-capacitance profile according to the capacity, and the voltage change (dV/dQ) for the capacity change based on the simulated potential-capacitance profile. Generate a simulated capacity-potential differential profile expressed according to capacity,
The actual potential-capacitance differential profile showing the capacity change (dQ/dV) in response to voltage change based on the actual potential-capacitance profile and the capacity change (dQ/dV) in response to voltage change based on the simulated potential-capacitance profile. Generates a simulated potential-capacitance profile expressed according to voltage,
An anode offset for the initial anode profile is derived using the measured capacitance-potential differential profile, the simulated capacitance-potential differential profile, the measured potential-capacitance differential profile, and the simulated potential-capacitance profile, and the initial cathode profile Deriving the cathode offset for the battery system. According to clause 5,
The main control unit,
Increase or decrease the initial anode profile and the initial cathode profile so that the measured capacitance-potential differential profile and the simulated capacitance differential profile match, and the measured potential-capacitance differential profile and the simulated potential-capacitance profile match. A battery system that repeats an increase/decrease operation and a left/right movement to move to the left or right, and derives the anode offset and the cathode offset according to the repetition results. According to clause 6,
The main control unit,
An anode degradation degree based on a reduction rate according to the increase/decrease amount of the anode offset, a cathode degradation degree based on a decrease rate according to the increase/decrease amount of the cathode offset, and LLI (Loss of A battery system that determines cell degradation based on lithium inventory. In clause 7,
The main control unit,
A battery system wherein the cell degradation degree is calculated by adding the LLI to a larger value of the anode degradation degree and the cathode degradation degree. In clause 7,
The main control unit,
A battery system that calculates the LLI based on a degree of discrepancy between the left-right movement amount of the anode offset and the left-right movement amount of the negative electrode profile. generating a first measured potential-capacitance profile for an initial cell according to a first cell current flowing in the initial cell and a cell voltage of the initial cell;
deriving a first simulation potential-capacitance profile by combining a reference anode profile and a reference cathode profile corresponding to the first cell current;
generating an initial anode profile and an initial cathode profile by correcting the reference anode profile and the reference cathode profile so that the first measured potential-capacitance profile matches the first simulated potential-capacitance profile;
generating an actual potential-capacity profile according to a cell current flowing in a battery cell and a cell voltage of the battery cell;
generating a simulated potential-capacitance profile based on an initial anode profile and an initial cathode profile corresponding to the cell current;
Deriving an anode offset and a cathode offset for each of the initial anode profile and the initial cathode profile so that the measured potential-capacitance profile and the simulated potential-capacitance profile match; and
A method for diagnosing the degree of battery cell degradation, comprising determining the degree of degradation of the battery cell according to the anode offset and the cathode offset. According to clause 10,
The step of generating the initial anode profile and the initial cathode profile,
generating a first measured capacity-potential differential profile showing a voltage change (dV/dQ) for a change in capacity based on the first measured potential-capacitance profile according to the capacity;
generating a first measured potential-capacitance differential profile showing a change in capacity (dQ/dV) according to voltage based on the first measured potential-capacitance profile;
generating a first simulated capacitance-potential differential profile representing a voltage change (dV/dQ) for a capacitance change based on the first simulated potential-capacitance profile according to capacitance;
generating a first simulated potential-capacitance profile showing a change in capacity (dQ/dV) according to voltage with respect to a change in voltage based on the first simulated potential-capacitance profile; and
Anode offset relative to the reference anode profile using the first measured capacitance-potential differential profile, the first simulated capacitance-potential differential profile, the first measured potential-capacitance differential profile, and the first simulated potential-capacitance profile. A method for diagnosing battery cell deterioration, including deriving a cathode offset with respect to the reference cathode profile. According to clause 11,
The step of deriving the anode offset and the cathode offset is,
The reference anode profile and the first measured capacitance-potential differential profile and the first simulated capacitance differential profile are matched, and the first measured potential-capacitance differential profile is matched with the first simulated potential-capacitance profile, and Repeating an increase/decrease operation to increase or decrease the reference cathode profile and a left/right movement to move the reference cathode profile to the left or right; and
A method for diagnosing battery cell deterioration, comprising deriving the anode offset and the cathode offset according to the repetition result. According to clause 10,
The step of deriving the anode offset and the cathode offset is,
Generating a measured capacity-potential differential profile showing a voltage change (dV/dQ) for a change in capacity based on the measured potential-capacitance profile according to the capacity;
Generating a measured potential-capacitance differential profile showing a change in capacity (dQ/dV) according to voltage based on the measured potential-capacitance profile;
Generating a simulated capacitance-potential differential profile showing voltage change (dV/dQ) for capacitance change based on the simulated potential-capacitance profile according to capacitance;
Generating a simulated potential-capacitance profile showing a change in capacity (dQ/dV) according to voltage based on the simulated potential-capacitance profile; and
The anode offset with respect to the initial anode profile is derived using the measured capacitance-potential differential profile, the simulated capacitance-potential differential profile, the measured potential-capacitance differential profile, and the simulated potential-capacitance profile, and the initial cathode A method for diagnosing battery cell deterioration, comprising deriving the cathode offset relative to a profile. According to clause 13,
Deriving the anode offset with respect to the initial anode profile and deriving the cathode offset with respect to the initial cathode profile comprises:
Increase or decrease the initial anode profile and the initial cathode profile so that the measured capacitance-potential differential profile and the simulated capacitance differential profile match, and the measured potential-capacitance differential profile and the simulated potential-capacitance profile match. repeating the increase/decrease movement and the left/right movement to move to the left or right; and
A method for diagnosing battery cell deterioration, comprising deriving the anode offset and the cathode offset according to the repetition result. According to clause 14,
The step of determining the degree of degradation of the battery cell is,
determining a degree of anode degradation based on a reduction rate according to an increase or decrease in the anode offset;
determining a degree of cathode degradation based on a reduction rate according to an increase or decrease in the cathode offset;
calculating loss of lithium inventory (LLI) based on the left-right movement amount of the anode offset and the left-right movement amount of the cathode offset; and
A method for diagnosing battery cell degradation, comprising calculating the cell degradation based on the anode degradation, the cathode degradation, and the LLI. According to clause 15,
The step of calculating the cell degeneration degree is,
A method for diagnosing battery cell degradation, comprising calculating the cell degradation by adding the LLI to a larger value of the anode degradation and the cathode degradation. According to clause 15,
The step of calculating the cell degeneration degree is,
A method for diagnosing the degree of battery cell deterioration, further comprising calculating the LLI based on a degree of discrepancy between the left and right movement amount of the anode offset and the left and right movement amount of the cathode profile.