Apparatus and method for estimating impedance spectrum of battery, and system including same

Abstract

Regarding the battery impedance spectrum estimation device and method, and the system including the same, according to the embodiments and experimental examples of the present invention, the battery impedance spectrum estimation device and method, and the system including the same obtains measurement values ​​from an electrochemical impedance spectroscopy (EIS) device that measures the impedance spectrum value of a battery assembly in a pack or module unit, and a battery charge / discharge measurement device that applies a pulse current to the battery assembly in a pack or module unit to measure specific parameter values ​​due to charging or discharging, and estimates a battery impedance spectrum value on a cell-by-cell basis, thereby enabling non-destructive measurement without disassembling the battery on a cell-by-cell basis, and thus facilitating reassembly and reducing costs. This makes it possible to provide a highly efficient, low-cost battery impedance spectrum estimation device and method, and a system including the same.

Description

[Technical field]

[0001] This application claims the benefit of the filing dates of Korean Patent Application No. 10-2021-0149820 filed with the Korean Intellectual Property Office on November 3, 2021, and Korean Patent Application No. 10-2022-0145075 filed with the Korean Intellectual Property Office on November 3, 2022, and all of the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to an apparatus and method for estimating an impedance spectrum of a battery, and a system including the same, and more specifically, to an apparatus and method for estimating an impedance spectrum value of a battery on a cell-by-cell basis from a battery impedance spectrum measurement value on a pack or module-by-pack basis, and a system including the same. [Background technology]

[0003] It is of paramount importance to diagnose the condition of a battery that is in service or being reused.

[0004] Generally, in order to diagnose the state of a battery, the state of charge (SoC) and state of health (SoH) of the battery are checked.

[0005] In order to confirm the state of charge (SoC) and state of health (SoH) of a battery, the impedance spectrum of a battery cell has been measured by electrochemical impedance spectroscopy (EIS) in the past.

[0006] In order to measure the impedance spectrum of a battery cell using a conventional EIS device, a battery provided in a pack or module form is disassembled into cells as shown in Figure 1, and an EIS measurement device is connected to the positive (+) and negative (-) leads of each disassembled cell.

[0007] Generally, when disassembling a battery pack into modules, non-destructive disassembly is possible by removing bus bars used for connecting battery modules. However, when disassembling a battery module into cells, disassembly is required by breaking the welds of the cell leads using a laser or ultrasonic waves, which makes it difficult to reassemble the battery module unless the cell leads are replaced. In order to replace the cell leads, the battery cells must be disassembled into components and then reassembled. Summary of the Invention [Problem to be solved by the invention]

[0008] In order to solve the above problems, an object of the present invention is to provide a highly efficient, low-cost battery impedance spectrum estimation device that estimates a battery impedance spectrum value on a cell-by-cell basis from an impedance spectrum measurement value of a battery assembly on a pack or module basis.

[0009] Another object of the present invention to solve the above problems is to provide a highly efficient and low-cost method for estimating an impedance spectrum of a battery, which estimates an impedance spectrum value of a battery on a cell-by-cell basis from an impedance spectrum measurement value of a battery assembly on a pack or module basis.

[0010] Another object of the present invention to solve the above problems is to provide a highly efficient and low-cost battery impedance spectrum estimation system that estimates a battery impedance spectrum value on a cell-by-cell basis from an impedance spectrum measurement value of a battery assembly on a pack or module basis. [Means for solving the problem]

[0011] In order to achieve the above object, an impedance spectrum estimation device for a battery cell according to one embodiment of the present invention includes a memory and a processor that executes at least one instruction stored in the memory, the at least one instruction including: instructions for obtaining EIS (Electrical Impedance Spectroscopy) measurements of a battery assembly; instructions for modeling an equivalent circuit model (ECM) of the battery assembly based on the EIS measurements and determining initial parameter values ​​for the equivalent circuit; instructions for converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value and calculating a first cell voltage value based on the first parameter value; instructions for obtaining a second cell voltage value measured by charging or discharging the battery cell; instructions for comparing the first cell voltage value and the second cell voltage value and correcting the conversion constant based on a comparison result; instructions for calculating a final parameter value based on the corrected conversion constant; and instructions for applying the final parameter value to the equivalent circuit to obtain an EIS estimate for the battery cell.

[0012] Here, the initial parameter values ​​of the equivalent circuit may include parameter values ​​for at least one of a resistor, a capacitor, an inductor, and a CPE (Constant Phase Element).

[0013] Moreover, the conversion constant may be a constant for converting an equivalent circuit of a battery assembly into an equivalent circuit of a battery cell.

[0014] Meanwhile, the instruction for calculating the first cell voltage value may include an instruction for converting the equivalent circuit into an impedance function over time and applying initial parameter values ​​to the impedance function to obtain the internal impedance, and an instruction for multiplying the internal impedance by a current value to calculate the first cell voltage value.

[0015] In this case, the impedance function may be a function obtained by converting an equivalent circuit into a function related to time using a predetermined differential equation.

[0016] On the other hand, the second cell voltage value may be a cell voltage value measured by a discharge pulse current of the battery cell.

[0017] Additionally, the instructions to correct the conversion constant may include instructions to correct the conversion constant such that a difference between the first cell voltage value and the second cell voltage value is minimized.

[0018] To achieve the above object, a method for estimating an impedance spectrum of a battery cell according to another embodiment of the present invention includes the steps of: acquiring EIS (Electrical Impedance Spectroscopy) measurements of a battery assembly; modeling an equivalent circuit model (ECM) of the battery assembly based on the EIS measurements and determining initial parameter values ​​for the equivalent circuit; converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value and calculating a first cell voltage value based on the first parameter value; acquiring a second cell voltage value measured by charging or discharging the battery cell; comparing the first cell voltage value with the second cell voltage value and correcting the conversion constant based on the comparison result; calculating a final parameter value based on the corrected conversion constant; and applying the final parameter value to the equivalent circuit to acquire an EIS estimation value for the battery cell.

[0019] Here, the at least one initial parameter value of the equivalent circuit may include a parameter value for at least one of a resistor, a capacitor, an inductor, and a CPE (Constant Phase Element).

[0020] Moreover, the conversion constant may be a constant for converting an equivalent circuit of a battery assembly into an equivalent circuit of a battery cell.

[0021] Meanwhile, the step of calculating the first cell voltage value may include a step of converting the equivalent circuit into an impedance function with respect to time and applying initial parameter values ​​to the impedance function to obtain the internal impedance, and a step of multiplying the internal impedance by a current value to calculate the first cell voltage value.

[0022] In this case, the impedance function may be a function obtained by converting an equivalent circuit into a function related to time using a predetermined differential equation.

[0023] On the other hand, the second cell voltage value may be a cell voltage value measured by a discharge pulse current of the battery cell.

[0024] Also, correcting the conversion constant may include correcting the conversion constant such that a difference between the first cell voltage value and the second cell voltage value is minimized.

[0025] According to another embodiment of the present invention, a system for estimating an impedance spectrum of a battery cell includes an electrochemical impedance spectroscopy (EIS) device for measuring an impedance spectrum value of a battery assembly, a battery cell impedance estimation device for calculating a first cell voltage for the battery cell to obtain an EIS estimated value of the battery cell, and a battery charge / discharge measurement device for measuring a second cell voltage due to charging or discharging the battery cell. The battery cell impedance estimation device models an equivalent circuit model (hereinafter, referred to as ECM) of the battery assembly based on the measurement value of the EIS device, determines at least one initial parameter value of the equivalent circuit, converts at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value, calculates a first cell voltage based on the first parameter value, compares the calculated first cell voltage value with a second cell voltage value measured by the battery charge / discharge measurement device, corrects the conversion constant, calculates a final parameter value based on the corrected conversion constant, and applies the final parameter value to the equivalent circuit to obtain an EIS estimated value of the battery cell. Effect of the Invention

[0026] The battery impedance spectrum estimation device and method, and system including the same, according to the embodiments and experimental examples of the present invention obtain measurement values ​​from an electrochemical impedance spectroscopy (EIS) device that measures the impedance spectrum value of a battery assembly in a pack or module unit, and a battery charge / discharge measurement device that applies a pulse current to the battery assembly in a pack or module unit to measure specific parameter values ​​due to charging or discharging, and estimate a battery impedance spectrum value on a cell-by-cell basis, thereby enabling non-destructive measurement without disassembling the battery on a cell-by-cell basis, and thus facilitating reassembly and reducing costs. As a result, it is possible to provide a highly efficient, low-cost battery impedance spectrum estimation device and method, and system including the same. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram of an electrochemical impedance spectroscopy (EIS) apparatus connected to a conventional battery cell. [Diagram 2] FIG. 1 is a block diagram of a battery cell impedance spectrum estimation system according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram of an electrochemical impedance spectroscopy (EIS) apparatus according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram of a battery charge / discharge measuring device according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a block diagram of an impedance spectrum estimation device according to an embodiment of the present invention. [Figure 6] FIG. 2 is a flow diagram for explaining a method for estimating an impedance spectrum of a battery cell according to an embodiment of the present invention. [Figure 7] 1 is a Nyquist plot graph showing impedance measurement results for a battery assembly in pack or module units according to frequency using an electrochemical impedance spectroscopy apparatus according to an embodiment of the present invention. [Figure 8] FIG. 8 is an equivalent circuit diagram of a battery assembly obtained based on the impedance measurement results in FIG. 7. [Figure 9] 1 is a graph comparing a first cell voltage value calculated using an impedance function to which a first parameter is applied with a second cell voltage value measured by applying a discharge pulse current to a battery assembly, for explaining a method for estimating impedance of a battery cell according to an experimental example of the present invention. [Figure 10] 10 is a graph comparing a third cell voltage value calculated using an equivalent circuit model to which final parameter values ​​are applied with a second cell voltage value measured by applying a discharge pulse current to a battery assembly, for explaining a method for estimating impedance of a battery cell according to an experimental example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention can be modified in various ways and can have various embodiments. Here, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to the specific embodiments, and it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention. Similar reference numerals are used for similar components while describing each drawing.

[0029] Terms such as first, second, A, B, etc. may be used to describe various components, but the components are not limited by these terms. The terms are used only to distinguish one component from another. For example, a first component may be named a second component, and similarly, a second component may be named a first component, without departing from the scope of the present invention. The term "and / or" includes a combination of multiple associated listed items or any of multiple associated listed items.

[0030] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that there may be other components in between. In contrast, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0031] The terms used in this application are merely used to describe certain embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In this application, the terms "include" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and are not intended to preclude the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0032] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted as having an ideal or overly formal meaning unless expressly defined in this application.

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0034] FIG. 2 is a block diagram of a battery cell impedance spectrum estimation system according to an embodiment of the present invention.

[0035] 2, the battery cell impedance spectrum estimation system S according to an embodiment of the present invention can estimate an impedance spectrum value of each battery cell by measuring an impedance spectrum of a battery assembly and charge or discharge data by applying a pulse current. Here, the battery assembly can include batteries provided in a pack or module form.

[0036] More specifically, in the embodiment, the battery cell impedance spectrum estimation system S may include an electrochemical impedance spectroscopy (EIS) device 1000, a charge / discharge measurement device 3000, and an impedance spectrum estimation device 5000.

[0037] In this case, the electrochemical impedance spectroscopy (EIS) device 1000 measures the impedance of the battery assembly, the charge / discharge measurement device 3000 measures the cell voltage of the battery assembly, and the impedance spectrum estimation device 5000 can estimate the impedance spectrum value of each battery cell based on the measurement values ​​measured by the electrochemical impedance spectroscopy (EIS) device 1000 and the charge / discharge measurement device 3000.

[0038] In the following, the features of each component of the battery cell impedance spectrum estimation system S will be described in more detail with reference to the drawings.

[0039] FIG. 3 is a diagram of an electrochemical impedance spectroscopy (EIS) apparatus according to an embodiment of the present invention.

[0040] Referring to FIG. 3, an electrochemical impedance spectroscopy (EIS) device 1000 can be connected to a battery assembly provided in a pack or module unit to measure the impedance spectrum of the battery assembly.

[0041] According to an embodiment, an electrochemical impedance spectroscopy (EIS) device 1000 can be connected to the positive (+) and negative (-) leads of a battery pack or module to measure the impedance spectrum of the battery pack or module.

[0042] The electrochemical impedance spectroscopy (EIS) device 1000 can then transmit the impedance spectrum measurements of the battery pack or module to an impedance spectrum estimation device 5000 described below.

[0043] Conventional electrochemical impedance spectroscopy (EIS) devices measure the impedance spectrum of battery cells by connecting a battery assembly provided in a pack or module unit to a battery cell that has been disassembled into cells. However, this has the disadvantage that the welds of the cell leads must be destroyed when disassembling the battery into cells, making it difficult to reassemble after measurement.

[0044] However, the battery cell impedance spectrum estimation system S according to an embodiment of the present invention measures the impedance spectrum of a battery assembly in a pack or module unit using an electrochemical impedance spectroscopy (EIS) device 1000, corrects the impedance spectrum, and estimates the impedance spectrum value of each battery cell, thereby providing a highly efficient, low-cost battery cell impedance spectrum estimation system S that is easy to reassemble and reduces costs through non-destructive measurement.

[0045] FIG. 4 is a diagram of a battery charge / discharge measuring device according to an embodiment of the present invention.

[0046] Referring to FIG. 4, a battery charge / discharge measurement device 3000 can be connected to a battery assembly provided in a pack or module unit.

[0047] Thereafter, the battery charge / discharge measurement device 3000 applies a pulse current to the battery to charge or discharge the battery, thereby measuring the cell voltage of the battery.

[0048] According to an embodiment, the battery charge / discharge measurement device 3000 is connected to the positive (+) and negative (-) leads of a battery assembly, and can measure the cell voltage due to battery charging or discharging by applying a pulse current to the battery assembly in a pack or module form.

[0049] Thereafter, the battery charge / discharge measurement device 3000 can transmit the cell voltage measurement value due to battery charge or discharge to the impedance spectrum estimation device 5000 described below.

[0050] FIG. 5 is a block diagram of an impedance spectrum estimation device according to an embodiment of the present invention.

[0051] Referring to FIG. 5, an impedance spectrum estimation apparatus 5000 according to an embodiment of the present invention can receive impedance spectrum measurement values ​​and cell voltage measurement values ​​for a battery assembly in the form of a pack or module measured from an electrochemical impedance spectroscopy (EIS) apparatus 1000 and a charge / discharge measurement apparatus 3000, and estimate a battery impedance spectrum on a cell-by-cell basis.

[0052] Describing the battery cell impedance spectrum estimation apparatus 5000 in more detail by hardware configuration, the impedance spectrum estimation apparatus 5000 may include a memory 100, a processor 200, a transceiver device 300, an input interface device 400, an output interface device 500 and a storage device 600.

[0053] According to the embodiment, the components 100, 200, 300, 400, 500, and 600 included in the impedance spectrum estimation apparatus 5000 are connected by a bus 700 and can communicate with each other.

[0054] The memory 100 and the storage device 600 in the above configurations 100, 200, 300, 400, 500, and 600 of the impedance spectrum estimation device 5000 may be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 100 and the storage device 600 may be composed of at least one of a read only memory (ROM) and a random access memory (RAM).

[0055] Among other things, memory 100 may contain at least one instruction that is executed by processor 200 .

[0056] According to an embodiment, the at least one instruction may include instructions for obtaining Electrical Impedance Spectroscopy (EIS) measurements of the battery assembly, instructions for modeling an equivalent circuit model (ECM) of the battery assembly based on the EIS measurements and determining initial parameter values ​​for the equivalent circuit, instructions for converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value and calculating a first cell voltage value based on the first parameter value, instructions for obtaining a second cell voltage value measured by charging or discharging the battery cell, instructions for comparing the first cell voltage value and the second cell voltage value and correcting the conversion constant based on the comparison result, instructions for calculating a final parameter value based on the corrected conversion constant, and instructions for applying the final parameter value to the equivalent circuit to obtain an EIS estimate for the battery cell.

[0057] The processor 200 may represent a central processing unit (CPU), a graphics processing unit (GPU), or a special purpose processor on which methods according to embodiments of the present invention are performed.

[0058] The processor 200 is capable of executing at least one program command stored in the memory 100, as described above.

[0059] The battery impedance spectrum estimation system according to the embodiment of the present invention has been described above. In the following, a battery cell impedance spectrum estimation method using a processing operation of an impedance spectrum estimation device, which is one of the battery impedance spectrum estimation systems, will be described in more detail.

[0060] FIG. 6 is a flow diagram for explaining a method for estimating an impedance spectrum of a battery cell according to an embodiment of the present invention.

[0061] Referring to FIG. 6, the processor 200 in the battery cell impedance spectrum estimation device 5000 can obtain impedance spectrum measurement values ​​for a battery assembly in pack or module units (S1000).

[0062] According to an embodiment, the processor 200 can receive impedance spectrum values ​​(EIS measurements) measured from a pack or modular battery assembly from an electrochemical impedance spectroscopy (EIS) device 1000.

[0063] FIG. 7 is a Nyquist plot graph showing impedance measurement results for a battery assembly in a pack or module unit according to frequency using an electrochemical impedance spectroscopy apparatus according to an embodiment of the present invention.

[0064] 7, the impedance spectrum measurements of a battery assembly (pack or module) obtained by the processor 200 can be expressed as impedance output values ​​by frequency, where Z' is the real value of the impedance (Z_re) and Z'' is the imaginary value of the impedance (Z_im).

[0065] The processor 200 can then model an equivalent circuit of the battery assembly, which is a pack or module, based on the acquired EIS measurements (Equivalent Circuit Model, ECM, S2000) and determine at least one initial parameter value of the modeled equivalent circuit (S3000). A method of modeling an equivalent circuit of a battery and determining an initial parameter value of the modeled equivalent circuit will be described in more detail below with reference to FIG. 8.

[0066] FIG. 8 is an equivalent circuit diagram of the battery assembly obtained based on the impedance measurement results in FIG.

[0067] Referring to FIG. 8, the processor 200 can model an equivalent circuit of a battery to have the same impedance as the impedance spectrum measurement of the battery assembly in a pack or module.

[0068] According to the embodiment, the amplitude and phase components indicating the output characteristics of the impedance spectrum can be expressed by a combination of at least one of resistors, capacitors, and inductors. In other words, the battery equivalent circuit model of the pack or module may be expressed by at least one parameter of resistors R0, R1, R2, R3, and R4, capacitors C1, C2, C3, and C4, inductor L1, and CPE (Constant Phase Element). Here, CPE may be an impedance parameter that creates an impedance characteristic value intermediate between that of a capacitor and a resistor. For example, the battery equivalent circuit model (ECM) may be expressed by the sum of an impedance due to the electrolyte (P1), an impedance of an electrochemical impedance spectroscopy (EIS) device (P2), an impedance due to an SEI layer (P3), an impedance due to charge transfer between the interface between the electrode and the electrolyte (P4), and a Warburg (diffusion) impedance coefficient (P5). Here, the impedance of the electrochemical impedance spectroscopy (EIS) device (P2) may include a resistance generated by a cable of a measuring device.

[0069] The processor 200 may then determine initial parameter values ​​for the modeled equivalent circuit.

[0070] More specifically, the processor 200 can determine initial parameter values ​​of at least one of resistors, capacitors, inductors, and CPEs in an equivalent circuit model of the battery, as shown in Table 1 below, based on the impedance spectrum measurement value of the battery in pack or module units.

[0071] According to the embodiment, the processor 200 can infer the value of a variable based on the impedance measurement result graph by frequency in Fig. 7 and the equivalent circuit model in Fig. 8 based on the impedance measurement result graph by frequency for the inferred variable value, and can determine the variable value showing a pattern similar to the graph in Fig. 7 as the initial parameter value by comparing the impedance measurement result graph by frequency in Fig. 7 with the impedance measurement result graph by frequency in Fig. 7.

[0072] [Table 1] R0: Electrolyte Resistance L1: Line Inductance of the EIS device R1: Resistance of the EIS device R2: Resistance of the SEI layer (Solid Electrolyte Interphase Layer) C2: Capacitance of the SEI layer (Solid Electrolyte Interphase Layer) R3: Charge Transfer Resistance (Rct) C3: Capacitance at the interface (Double Layer) CPE1, R4, C4: Warburg (diffusion) impedance coefficients

[0073] Referring again to FIG. 6, the processor 200 may obtain a first parameter value in battery cell units by dividing the initial parameter value by a conversion constant (n-Factor) as shown in Table 2 below (S4000).

[0074] Here, the conversion constant (n-factor) may be a constant for converting initial parameter values ​​acquired based on a battery assembly in pack or module units into battery cell units. According to an embodiment, the initial value of the conversion constant (n-factor) may be defined based on the number of battery cells included in the battery assembly (pack or module). For example, as shown in Table 2 below, some initial values ​​(R1, R2, R3) of the conversion constant (n-factor) may be defined based on the number (20) of battery cells included in a module.

[0075] On the other hand, as shown in Table 2 below, the inductor L1 and the capacitors C1, C2, C3, and C4 have a negligible effect on the change in the value of the impedance (R) below (see Equation 1 below), so the conversion constant (n-factor) does not need to be defined.

[0076] [Table 2] The conversion constant may be corrected based on the result of comparing the first cell voltage value with the second cell voltage value in step S8000 described later. As a result, the initial value of the conversion constant does not need to be defined as an accurate value. However, it is preferable to define the conversion constant as an approximate value for converting the parameters in the assembly unit to the parameters in the battery cell unit, as shown in Table 2 above.

[0077] In an embodiment, the initial value of the conversion constant may be input by an administrator or may be defined as a pre-stored value corresponding to the number of battery cells.

[0078] Thereafter, the processor 200 can calculate the internal impedance function of the battery over time (S5000).

[0079] More specifically, the processor 200 can use differential equations to arrange the equivalent circuit (ECM, see FIG. 8) of the battery assembly (pack or module) as a function of time.

[0080] For example, to more fully explain how the processor 200 arranges the RC parallel components (P2, P3, P4) in the equivalent circuit as a function of time, the processor 200 can arrange the RC parallel components in terms of current (I) using Ohm's law (V=IR) as Equation 1.

[0081]

number

[0082]

number

[0083]

number

[0084]

number

[0085]

number

[0086]

number

[0087] Then, the processor 200 can multiply the internal impedance of the battery by the current value to calculate the first cell voltage value (S6000). In other words, the internal impedance of the battery can act as the internal resistance value of the battery.

[0088] The processor 200 may also obtain a second cell voltage value measured by a pulse current of the battery (S7000). Here, the second cell voltage value may be a cell voltage value measured by applying a discharge pulse current from the charge / discharge measurement device 3000 to a battery assembly, which is a pack or module unit.

[0089] FIG. 9 is a graph comparing a first cell voltage value calculated using an impedance function to which a first parameter is applied with a second cell voltage value measured by applying a discharge pulse current to a battery assembly, for illustrating a method for estimating impedance of a battery cell according to an experimental example of the present invention.

[0090] Referring to FIG. 9, by comparing the first cell voltage value with the second cell voltage value, it can be confirmed that since the first cell voltage value is calculated using a conversion constant defined based on the number of cells generally contained inside a battery assembly (pack or module), there is a slight difference between the first cell voltage value and the second voltage value actually measured by applying a discharge pulse current.

[0091] Therefore, the processor 200 can correct the conversion constant (n-factor) so that the difference between the first cell voltage value and the second cell voltage value for each cell is minimized for more accurate calculation of the impedance of the battery cell (S8000).

[0092] Here, the conversion constant (n-factor) may be a value by which at least one initial parameter constituting an equivalent circuit of a battery assembly in a pack or module unit is divided to estimate a value in a cell unit, as described above. In other words, the processor 200 can obtain a more accurate final parameter value in a battery cell unit by correcting the conversion constant applied to the initial parameter of the equivalent circuit model to a value that minimizes the difference between the first cell voltage value and the second cell voltage value (S9000).

[0093] For example, when a battery assembly (pack or module) is composed of 20 cells, the processor 200 can correct the equivalent circuit parameter values ​​for each battery cell as shown in Table 3 below.

[0094] [Table 3] FIG. 10 is a graph comparing a third cell voltage value calculated using an equivalent circuit model to which final parameter values ​​are applied with a second cell voltage value measured by applying a discharge pulse current to a battery assembly, in order to explain a method for estimating impedance of a battery cell according to an experimental example of the present invention.

[0095] Referring to FIG. 10, the third cell voltage may be a value calculated by multiplying the internal impedance, to which the final parameter is applied to the impedance function, by the current value according to an embodiment of the present invention.

[0096] According to the embodiment, by comparing the third cell voltage with the second cell voltage value measured by actually inputting a discharge pulse current, it can be confirmed that the third cell voltage value calculated using the final parameter value in which the conversion constant is corrected is similar to the second cell voltage value measured by actually applying a discharge pulse current.

[0097] Referring again to FIG. 6, the processor 200 may estimate an impedance spectrum for each battery cell by individually applying the corrected final parameter value for each battery cell to an equivalent circuit model (S10000).

[0098] According to the embodiment, the processor 200 may obtain an impedance spectrum estimate value for each battery cell by substituting an impedance spectrum measurement value acquired from a battery assembly in a pack or module unit into a corrected equivalent circuit model to which the corrected final parameter value is applied. In this case, the corrected final parameter value may be converted (Zre, Zim) into an impedance spectrum value for use.

[0099] The battery impedance spectrum estimation device and method, and the system including the same, according to the embodiments and experimental examples of the present invention have been described above.

[0100] The battery impedance spectrum estimation device and method, and system including the same, according to the embodiments and experimental examples of the present invention obtain measurement values ​​from an electrochemical impedance spectroscopy (EIS) device that measures the impedance spectrum value of a battery assembly in a pack or module unit, and a battery charge / discharge measurement device that applies a pulse current to the battery assembly in a pack or module unit to measure specific parameter values ​​due to charging or discharging, and estimate a battery impedance spectrum value on a cell-by-cell basis, thereby enabling non-destructive measurement without disassembling the battery on a cell-by-cell basis, and thus facilitating reassembly and reducing costs. As a result, it is possible to provide a highly efficient, low-cost battery impedance spectrum estimation device and method, and system including the same.

[0101] The operation of the method according to the embodiment and the experimental example of the present invention can be embodied as a computer readable program or code in a computer readable recording medium. The computer readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. In addition, the computer readable recording medium can be distributed to computer systems connected via a network, and the computer readable program or code can be stored and executed in a distributed manner.

[0102] Additionally, the computer readable recording medium may include a hardware device specially configured to store and execute program instructions, such as a ROM, a RAM, a flash memory, etc. The program instructions may include not only machine code, such as produced by a compiler, but also high-level language code that can be executed by a computer using an interpreter, etc.

[0103] Some aspects of the invention have been described in the context of an apparatus, but it may also be presented in terms of a corresponding method, where a block or apparatus corresponds to a method step or a feature of a method step. Similarly, aspects described in the context of a method may be presented in terms of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be performed by (or using) a hardware apparatus, such as, for example, a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, one or more of the most important method steps may be performed by such an apparatus.

[0104] Although the present invention has been described with reference to preferred embodiments thereof, those skilled in the art will understand that various modifications and variations of the present invention can be made without departing from the spirit and scope of the present invention as set forth in the following claims. [Explanation of symbols]

[0105] 1000: Electrochemical impedance spectroscopy (EIS) instrument 3000:Battery charge / discharge measuring device 5000: Battery cell impedance spectrum estimator S: Battery cell impedance spectrum estimation system 100:Memory 200: Processor 300: Transmitting and receiving device 400: Input interface device 500: Output interface device 600: Storage device 700: Bus

Claims

1. An impedance spectrum estimation device for a battery cell, comprising: Memory, a processor for executing at least one instruction stored in the memory; The at least one instruction: instructions for obtaining Electrical Impedance Spectroscopy (EIS) measurements of a battery assembly, which may be a battery pack or a battery module, the battery assembly including a plurality of battery cells; instructions for modeling an equivalent circuit model (ECM) of the battery assembly based on the EIS measurements and determining initial parameter values ​​for the equivalent circuit; instructions for converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value, and calculating a first cell voltage value based on the first parameter value, the conversion constant being a constant for converting an equivalent circuit of the battery assembly into an equivalent circuit of the battery cell; instructions for obtaining a second cell voltage value measured by charging or discharging the battery cell; instructions for comparing the first cell voltage value and the second cell voltage value and correcting the conversion constant based on a comparison result; instructions for calculating final parameter values ​​based on the corrected conversion constants; instructions for applying the final parameter values ​​to the equivalent circuit to obtain an EIS estimate for the battery cell; An apparatus for estimating an impedance spectrum of a battery cell, comprising:

2. The initial parameter values ​​of the equivalent circuit are The battery cell impedance spectrum estimating device of claim 1 , further comprising parameter values ​​for at least one of a resistor, a capacitor, an inductor, and a constant phase element (CPE).

3. The instructions to calculate the first cell voltage value include: instructions for converting the equivalent circuit into an impedance function with respect to time and applying the initial parameter values ​​to the impedance function to obtain an internal impedance; and an instruction for multiplying the internal impedance by a current value to calculate the first cell voltage value.

4. The impedance function is 4. The battery cell impedance spectrum estimation device according to claim 3, wherein the function is obtained by converting the equivalent circuit into a function related to time using a predetermined differential equation.

5. The second cell voltage value is The battery cell impedance spectrum estimation device according to claim 1 , wherein the cell voltage value is measured by a discharge pulse current of the battery cell.

6. The instruction to correct the conversion constant is The battery cell impedance spectrum estimator of claim 1 , further comprising instructions for correcting the conversion constant such that a difference between the first cell voltage value and the second cell voltage value is minimized.

7. A method for estimating an impedance spectrum of a battery cell, comprising: obtaining an Electrical Impedance Spectroscopy (EIS) measurement of a battery assembly, which may be a battery pack or a battery module, the battery assembly including a plurality of battery cells; modeling an equivalent circuit model (ECM) of the battery assembly based on the EIS measurements and determining initial parameter values ​​for the equivalent circuit; converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value, and calculating a first cell voltage value based on the first parameter value, the conversion constant being a constant for converting an equivalent circuit of the battery assembly into an equivalent circuit of the battery cell; obtaining a second cell voltage value measured by charging or discharging the battery cell; comparing the first cell voltage value with the second cell voltage value, and correcting the conversion constant based on a comparison result; calculating final parameter values ​​based on the corrected conversion constants; and applying the final parameter values ​​to the equivalent circuit to obtain an EIS estimate for the battery cell; A method for estimating an impedance spectrum of a battery cell, comprising:

8. At least one initial parameter value of the equivalent circuit is The method of claim 7 , further comprising parameter values ​​for at least one of a resistor, a capacitor, an inductor, and a constant phase element (CPE).

9. The step of calculating the first cell voltage value includes: converting the equivalent circuit into an impedance function with respect to time, and applying the initial parameter values ​​to the impedance function to obtain an internal impedance; and multiplying the internal impedance by a current value to calculate the first cell voltage value.

10. The impedance function is The method for estimating an impedance spectrum of a battery cell according to claim 9 , wherein the function is obtained by converting the equivalent circuit into a function related to time using a predetermined differential equation.

11. The second cell voltage value is The method for estimating an impedance spectrum of a battery cell according to claim 7 , wherein the cell voltage value is measured by a discharge pulse current of the battery cell.

12. The step of correcting the conversion constant includes: The method for estimating an impedance spectrum of a battery cell according to claim 7 , further comprising the step of correcting the conversion constant so that a difference between the first cell voltage value and the second cell voltage value is minimized.

13. An electrochemical impedance spectroscopy (EIS) device for measuring an impedance spectrum value of a battery assembly, which is a battery pack or a battery module, the battery assembly including a plurality of battery cells; a battery cell impedance estimating device configured to calculate a first cell voltage value for a battery cell to obtain an EIS estimate for the battery cell; a battery charge / discharge measurement device that measures a second cell voltage due to charging or discharging the battery cell; The battery cell impedance estimation device comprises: modeling an equivalent circuit model (hereinafter, referred to as ECM) of the battery assembly based on the measurement values ​​of the EIS device, and determining at least one initial parameter value of the equivalent circuit; converting at least one of the initial parameter values ​​using a predetermined conversion constant to derive a first parameter value, and calculating the first cell voltage value based on the first parameter value, the conversion constant being a constant for converting an equivalent circuit of the battery assembly into an equivalent circuit of the battery cell; comparing the calculated first cell voltage value with a second cell voltage value measured by the battery charge / discharge measuring device to correct the conversion constant; calculating final parameter values ​​based on the corrected conversion constants; applying the final parameter values ​​to the equivalent circuit to obtain the EIS estimate for the battery cell; A battery cell impedance spectrum estimation system.

14. A computer program comprising instructions for causing a computer to carry out the method for estimating an impedance spectrum of a battery cell according to any one of claims 7 to 12.

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