Battery diagnosis device, battery diagnosis method, and battery diagnosis system

Abstract

A battery diagnosis device according to an embodiment of the present disclosure includes an ohmic resistance determination unit configured to determine an ohmic resistance of a battery cell in each of a plurality of impedance distributions generated at different points in time with respect to the battery cell; a resistance change rate calculation unit configured to calculate a resistance change rate between the determined plurality of ohmic resistances; a gas generation degree determination unit configured to determine an internal gas generation degree of the battery cell based on the calculated resistance change rate; and a state diagnosis unit configured to diagnose a state of the battery cell in accordance with the determined internal gas generation degree.

Description

TECHNICAL FIELD

[0001] This application claims priority to Korean Patent Application No. 10-2020-0127289, filed on September 29, 2020, in the Republic of Korea, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The disclosure relates to a battery diagnostic apparatus, method, and system, and more particularly, to a battery diagnostic apparatus, method, and system capable of diagnosing a state of a battery cell. BACKGROUND

[0003] Recently, the demand for portable electronic products such as notebook computers, camcorders, and portable phones has sharply increased, and electric vehicles, energy storage batteries, robots, satellites, etc. are earnestly developed. Accordingly, high-performance batteries that allow repeated charging and discharging are being actively researched.

[0004] Currently marketed batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium batteries, etc. Among them, lithium batteries are of great interest because they have almost no memory effect compared to nickel-based batteries and also have a very low self-discharge rate and high energy density.

[0005] As the battery deteriorates, a side reaction accompanied by internal gas generation occurs. If the side reaction continues and the amount of internal gas exceeds the allowable value, the joint portion of the battery is disconnected, and the battery reaches the EOL (End of Life) state.

[0006] Therefore, in order to diagnose the state of the battery, it is necessary to measure the amount of internal gas, but in the related art, it is difficult to measure the amount of internal gas of the battery in a non-destructive manner. SUMMARY

[0007] TECHNICAL PROBLEM

[0008] The disclosure is designed to solve the problems of the related art, and thus the disclosure relates to providing a battery diagnostic apparatus, method, and system that can determine the internal gas generation level of a battery based on the ohmic resistance of the battery in a non-destructive manner and diagnose the state of the battery according to the determined internal gas generation level.

[0009] These and other objects and advantages of the disclosure can be understood from the following detailed description, and will be more fully apparent from the exemplary embodiments of the disclosure. Furthermore, it will be readily understood that the objects and advantages of the disclosure can be achieved by the devices shown in the claims and combinations thereof.

[0010] TECHNICAL SCHEME

[0011] In an aspect of the disclosure, there is provided a battery diagnostic device including: an ohmic resistance determination unit configured to determine an ohmic resistance of a battery cell in each of a plurality of impedance distributions generated at different points in time with respect to the battery cell; a resistance change rate calculation unit configured to calculate a resistance change rate between the determined plurality of ohmic resistances; a gas generation level determination unit configured to determine an internal gas generation level of the battery cell based on the calculated resistance change rate; and a state diagnosis unit configured to diagnose a state of the battery cell according to the determined internal gas generation level.

[0012] The gas generation level determination unit can be configured to determine the internal gas generation level of the battery cell based on a region to which the calculated resistance change rate belongs among preset reference change rate regions.

[0013] The reference change rate regions can be preset as a first region less than a first reference resistance change rate, a second region equal to or greater than the first reference resistance change rate and less than a second reference resistance change rate, and a third region equal to or greater than the second reference resistance change rate according to the internal gas generation level.

[0014] The gas generation level determination unit can be configured to determine the internal gas generation level as normal when the calculated resistance change rate belongs to the first region, determine the internal gas generation level as warning when the calculated resistance change rate belongs to the second region, and determine the internal gas generation level as dangerous when the calculated resistance change rate belongs to the third region.

[0015] The state diagnosis unit can be configured to diagnose the state of the battery cell as a normal state when the internal gas generation level is determined as normal.

[0016] The state diagnosis unit can be configured to diagnose the state of the battery cell as a warning state when the internal gas generation level is determined as warning, and reduce at least one of a maximum allowable temperature and a maximum allowable SOC.

[0017] The state diagnosis unit can be configured to diagnose the state of the battery cell as an unusable state when the internal gas generation level is determined as dangerous.

[0018] The battery diagnostic device according to still another aspect of the present disclosure can further include a measurement unit configured to measure at least one of a temperature, a voltage, and a current of the battery cell; and an SOC estimation unit configured to estimate an SOC of the battery cell based on at least one of the measured voltage and current.

[0019] The ohmic resistance determination unit can be configured to select at least one impedance distribution satisfying a predetermined condition among the plurality of impedance distributions based on the temperature of the battery cell measured by the measurement unit and the SOC of the battery cell estimated by the SOC estimation unit.

[0020] The resistance change rate calculation unit can be configured to calculate the resistance change rate based on the impedance distribution selected by the ohmic resistance determination unit.

[0021] The ohmic resistance determination unit can be configured to select, among the plurality of impedance distributions, an impedance distribution in which a temperature of a corresponding battery cell is equal to or higher than a reference temperature and an SOC of the corresponding battery cell is equal to or greater than a reference SOC.

[0022] The battery diagnostic device according to still another aspect of the present disclosure can further include a charge transfer resistance determination unit configured to determine a charge transfer resistance in each of the plurality of impedance distributions.

[0023] The resistance change rate calculation unit can be configured to further calculate a charge transfer resistance change rate between the determined plurality of charge transfer resistances.

[0024] The state diagnosis unit can be configured to further diagnose a state of the battery cell based on a comparison result of the calculated charge transfer resistance change rate with a reference resistance value.

[0025] The state diagnosis unit can be configured to diagnose the state of the battery cell as a normal state when the calculated charge transfer resistance change rate is less than the reference resistance value.

[0026] The state diagnosis unit can be configured to diagnose the state of the battery cell as a warning state when the calculated charge transfer resistance change rate is equal to or greater than the reference resistance value, and to reduce a maximum allowable C-rate of charging and discharging of the battery cell.

[0027] A battery diagnosis system according to still another aspect of the present disclosure can include the battery diagnosis apparatus according to an aspect of the present disclosure; an EIS unit configured to output an AC current to the battery cell, generate an impedance distribution representing an impedance of the battery cell as a correspondence between a real part and an imaginary part according to an output result of the AC current, and output the generated impedance distribution to the battery diagnosis apparatus.

[0028] The battery diagnosis system according to still another aspect of the present disclosure can further include a heating unit configured to raise a temperature of the battery cell such that the temperature of the battery cell becomes equal to or higher than a reference temperature; and a charging unit configured to charge the battery cell such that an SOC of the battery cell becomes equal to or greater than a reference SOC.

[0029] A battery pack according to still another aspect of the present disclosure can include the battery diagnosis apparatus according to an aspect of the present disclosure.

[0030] A battery diagnosis method according to still another aspect of the present disclosure can include an ohmic resistance determination step of determining an ohmic resistance of a battery cell in each of a plurality of impedance distributions generated at different time points with respect to the battery cell; an electrical resistance change rate calculation step of calculating an electrical resistance change rate between the determined plurality of ohmic resistances; a gas generation level determination step of determining an internal gas generation level of the battery cell based on the calculated electrical resistance change rate; and a state diagnosis step of diagnosing a state of the battery cell according to the determined internal gas generation level.

[0031] Advantageous Effects

[0032] According to an aspect of the present disclosure, based on a correlation between an ohmic resistance of a battery cell and an internal gas generation level of the battery cell, there is an advantage that the internal gas generation level and the state of the battery cell can be diagnosed in a non-destructive manner with an electrical resistance change rate of the ohmic resistance of the battery cell.

[0033] Effects of the present disclosure are not limited to the above-mentioned effects, and one of ordinary skill in the art can clearly understand other effects not mentioned by the description of the claims. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings illustrate preferred embodiments of the present disclosure and together with the above disclosure, provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the accompanying drawings.

[0035] Figure 1FIG. 1 is a diagram schematically illustrating a battery diagnostic apparatus according to an embodiment of the present disclosure.

[0036] Figure 2 FIG. 2 is a diagram schematically illustrating an impedance distribution according to an embodiment of the present disclosure.

[0037] Figure 3 FIG. 3 is a diagram schematically illustrating a plurality of impedance distributions according to an embodiment of the present disclosure.

[0038] Figure 4 FIG. 4 is a diagram schematically illustrating a plurality of other impedance distributions according to an embodiment of the present disclosure.

[0039] Figure 5 FIG. 5 is a diagram schematically illustrating a battery diagnostic system according to another embodiment of the present disclosure.

[0040] Figure 6 FIG. 6 is a diagram schematically illustrating an exemplary configuration of a battery pack according to another embodiment of the present disclosure.

[0041] Figure 7 FIG. 7 is a diagram schematically illustrating a battery diagnostic method according to still another embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] It should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings and should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define appropriate terms in the best way for the purpose of describing the disclosure.

[0043] Accordingly, the description set forth herein is merely illustrative in nature and is in no way intended to limit the scope of the disclosure as defined by the appended claims and the embodiments specifically recited therein.

[0044] In addition, in describing the present disclosure, when it is considered that a detailed description of related known elements or functions makes the key subject of the present disclosure unclear, the detailed description is omitted herein.

[0045] The terms including ordinal numbers such as "first," "second," and the like can be used to distinguish one element from another element in various elements, but are not intended to limit the elements by the terms.

[0046] Throughout the specification, when a part is referred to as "comprising" or "including" any element, it means that the part can further include other elements, not excluding the other elements, unless otherwise specifically stated.

[0047] Also, throughout the specification, when a part is referred to as being "connected" to another part, it not only is "directly connected" but also is "indirectly connected" with another element interposed therebetween.

[0048] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0049] Figure 1 FIG. 1 is a diagram schematically illustrating a battery diagnostic apparatus 100 according to an embodiment of the present disclosure.

[0050] Referring to Figure 1 , the battery diagnostic apparatus 100 can include an ohmic resistance determination unit 110, a resistance change rate calculation unit 120, a gas generation level determination unit 130, and a state diagnosis unit 140.

[0051] The ohmic resistance determination unit 110 can be configured to determine an ohmic resistance (Ro) of the battery cell in each of a plurality of impedance distributions generated at different time points with respect to the battery cell.

[0052] Here, the battery cell refers to one independent cell having a negative terminal and a positive terminal and being physically separable. For example, one pouch-type lithium polymer battery can be regarded as a battery cell.

[0053] In addition, the impedance distribution can be a distribution in which the impedance of the battery cell is represented as a correspondence relation between a real part (Zre) and an imaginary part (-Zim). The impedance distribution will be described in detail with reference to Figure 2 and Figure 3 .

[0054] Figure 2 FIG. 2 is a diagram schematically illustrating an impedance distribution according to an embodiment of the present disclosure. Specifically, Figure 2 FIG. 3 is a diagram schematically illustrating an example of an impedance distribution.

[0055] Referring to Figure 2 , when X is set as the real part (Zre) and Y is set as the imaginary part (-Zim), the impedance distribution can be represented as an X-Y plane graph. In Figure 2 an embodiment, the ohmic resistance of the battery cell can be a starting resistance value of the impedance distribution. Specifically, in the impedance distribution, the resistance value of the real part (Zre) at which the value of the imaginary part (-Zim) is 0 can be the ohmic resistance of the battery cell. Since the ohmic resistance is a well-known factor, it should be noted that the description of the ohmic resistance will be omitted.

[0056] Figure 3 FIG. 4 is a diagram schematically illustrating a plurality of impedance distributions according to an embodiment of the present disclosure. Specifically, Figure 3is a graph showing a plurality of impedance distributions obtained by the ohmic resistance determination unit 110.

[0057] In Figure 3 an embodiment of the present application, the ohmic resistance determination unit 110 can obtain the first impedance distribution P1 to the ninth impedance distribution P9. Preferably, the first impedance distribution P1 to the ninth impedance distribution P9 can be impedance distributions of impedances measured for one battery cell at intervals of 24 hours under the condition that the temperature and the SOC (State of Charge) are included in a predetermined range. Here, preferably, the first impedance distribution P1 can be generated first, and the ninth impedance distribution P9 can be generated most recently.

[0058] In addition, in Figure 3 an embodiment of the present application, the ohmic resistance determination unit 110 can determine the ohmic resistance in each of the first impedance distribution P1 to the ninth impedance distribution P9. Specifically, the ohmic resistance determination unit 110 can determine the resistance value of the real part (Zre) when the value of the imaginary part (-Zim) in each of the first impedance distribution P1 to the ninth impedance distribution P9 is 0 as the ohmic resistance of the corresponding impedance distribution. Preferably, in Figure 3 an embodiment of the present application, the ohmic resistance of the first impedance distribution P1 can be the smallest, and the ohmic resistance of the ninth impedance distribution P9 can be the largest.

[0059] The resistance change rate calculation unit 120 can be configured to calculate the resistance change rate between the plurality of ohmic resistances determined.

[0060] Specifically, the resistance change rate calculation unit 120 can calculate the resistance change rate between the plurality of ohmic resistances determined by the ohmic resistance determination unit 110. Preferably, the resistance change rate calculation unit 120 can calculate the resistance change rate between the plurality of ohmic resistances in consideration of the time points at which the plurality of impedance distributions are generated.

[0061] For example, in Figure 3 an embodiment of the present application, the resistance change rate calculation unit 120 can set the ohmic resistance of the first impedance distribution P1 as a standard and calculate the resistance change rate between the ohmic resistances of the first impedance distribution P1 to the ninth impedance distribution P9.

[0062] For example, assuming that the ohmic resistance determination unit 110 determines the ohmic resistance of each of the first impedance distribution to the n-th impedance distribution as Ro_1 to Ro_n. The resistance change rate calculation unit 120 can calculate the ratio of Ro_n to Ro_1 as the resistance change rate. In this case, the resistance change rate calculation unit 120 can calculate the resistance change rate by the calculation formula "Ro_n ÷ Ro_1".

[0063] As another example, the resistance change rate calculation unit can calculate a ratio of a difference between Ro_n and Ro_1 with respect to Ro_1 as the resistance change rate. In this case, the resistance change rate calculation unit 120 can calculate the resistance change rate by a calculation formula of "(Ro_n - Ro_1) ÷ Ro_1".

[0064] The gas generation level determination unit 130 can be configured to determine the internal gas generation level of the battery cell based on the calculated resistance change rate. That is, the gas generation level determination unit 130 can determine the internal gas generation level of the battery cell based on the resistance change rate calculated by the resistance change rate calculation unit 120.

[0065] Specifically, the gas generation level determination unit 130 can be configured to determine the internal gas generation level of the battery cell based on a region to which the calculated resistance change rate belongs among preset reference change rate regions.

[0066] For example, the reference change rate regions can be preset as a first region, a second region, and a third region. Hereinafter, it will be described that the reference change rate regions are set as the first to third regions, but it should be noted that the reference change rate regions can be set to be subdivided.

[0067] Preferably, the reference change rate regions can be configured to be preset as a first region less than a first reference resistance change rate, a second region equal to or greater than the first reference resistance change rate and less than a second reference resistance change rate, and a third region equal to or greater than the second reference resistance change rate according to the internal gas generation level.

[0068] The gas generation level determination unit 130 can determine a region to which the calculated resistance change rate belongs by substituting the calculated resistance change rate into the reference change rate regions. That is, the gas generation level determination unit 130 can determine a region to which the calculated resistance change rate belongs among the reference change rate regions.

[0069] For example, the gas generation level determination unit 130 can be configured to determine the internal gas generation level as normal when the calculated resistance change rate belongs to the first region, and to determine the internal gas generation level as warning when the calculated resistance change rate belongs to the second region, and to determine the internal gas generation level as dangerous when the calculated resistance change rate belongs to the third region.

[0070] The state diagnosis unit 140 can be configured to diagnose the state of the battery cell according to the determined internal gas generation level. That is, the state diagnosis unit 140 can diagnose the state of the battery cell according to the internal gas generation level determined by the gas generation level determination unit 130.

[0071] For example, in the previous embodiment, the gas generation level determination unit 130 can determine the internal gas generation level as normal, warning, or dangerous based on the calculated resistance change rate. In correspondence thereto, the state diagnosis unit 140 can diagnose the state of the battery cell as a normal state, a warning state, or an unusable state.

[0072] Specifically, the state diagnosis unit 140 can be configured to diagnose the state of the battery cell as the normal state when the internal gas generation level is determined as normal.

[0073] In addition, the state diagnosis unit 140 can be configured to diagnose the state of the battery cell as the warning state when the internal gas generation level is determined as warning. Preferably, the state diagnosis unit 140 can be configured to reduce at least one of the maximum allowable temperature and the maximum allowable SOC of the battery cell in order to suppress the generation of internal gas of the battery cell. That is, at least one of the maximum allowable temperature and the maximum allowable SOC can be set to be reduced for the corresponding battery cell.

[0074] In addition, the state diagnosis unit 140 can be configured to diagnose the state of the battery cell as the unusable state when the internal gas generation level is determined as dangerous.

[0075] That is, the battery diagnosis apparatus 100 according to the embodiment of the disclosure has the following advantages: based on the correlation between the ohmic resistance of the battery cell and the internal gas generation level of the battery cell, the internal gas generation level and the state of the battery cell are diagnosed in a non-destructive manner using the resistance change rate of the ohmic resistance of the battery cell. For example, if the amount of internal gas generated by the battery cell increases, the electron transport capacity inside the electrode decreases due to the internal gas, and the ohmic resistance of the battery cell can be perceptibly increased due to the decrease in the ionic conductivity of the electrolyte. Therefore, the battery diagnosis apparatus 100 can diagnose the gas generation level and the state of the battery cell based on the resistance change rate of the ohmic resistance by taking into account the relationship between the ohmic resistance and the amount of generated internal gas.

[0076] For example, when diagnosing the state of a plurality of battery cells collected for reuse, the battery diagnostic apparatus 100 according to an embodiment of the disclosure can be used. The battery diagnostic apparatus 100 can obtain a plurality of impedance distributions of each of the plurality of battery cells, and non-destructively diagnose an internal gas generation level and a state of each of the plurality of battery cells based on the obtained plurality of impedance distributions. The battery cell diagnosed as a normal state can be reused without an additional setting change, but the battery cell diagnosed as a warning state can be reused after being set to reduce at least one of a maximum allowable temperature and a maximum allowable SOC. In addition, the battery cell diagnosed as an unusable state cannot be reused. According to an embodiment of the disclosure, since the internal gas generation level and the state of the battery cell can be quickly and easily diagnosed using the ohmic resistance of the battery cell as described above, there is an advantage that the efficiency of diagnosing the state of the battery cell can be improved.

[0077] Further, the battery diagnostic apparatus 100 can further include a storage unit (not shown). The storage unit can store programs, data, etc. required for operating the battery diagnostic apparatus 100. That is, the storage unit can store data necessary for the operation and functions of each component of the battery diagnostic apparatus 100, data generated in the process of performing the operation or function, etc. The kind of the storage unit is not particularly limited as long as it is a known information storage device that can record, erase, update, and read data. As an example, the information storage device can include a RAM, a flash memory, a ROM, an EEPROM, a register, etc. In addition, the storage unit can store a program code in which processes executable by each component of the battery diagnostic apparatus 100 are defined.

[0078] Referring to Figure 1 , the battery diagnostic apparatus 100 can further include a measurement unit 150 and an SOC estimation unit 160.

[0079] The measurement unit 150 can be configured to measure at least one of a temperature, a voltage, and a current of the battery cell.

[0080] Preferably, the measurement unit 150 can measure the temperature of the battery cell. In addition, the measurement unit 150 can measure at least one of the voltage and the current of the battery cell.

[0081] More preferably, the measurement unit 150 can measure all of the temperature, the voltage, and the current of the battery cell.

[0082] The SOC estimation unit 160 can be configured to estimate the SOC of the battery cell based on at least one of the measured voltage and current.

[0083] For example, the SOC estimation unit 160 can estimate the SOC of the battery cell using an extended Kalman filter (EKF). As another example, the SOC estimation unit 160 can estimate the SOC of the battery cell using a current counting method (coulomb counting, ampere counting) for counting the current of the battery cell measured by the measurement unit 150. Since the SOC estimation unit 160 estimates the SOC of the battery cell using a well-known method, a detailed description thereof will be omitted.

[0084] The ohmic resistance determination unit 110 can be configured to select at least one impedance distribution satisfying a predetermined condition among the plurality of impedance distributions based on the temperature of the battery cell measured by the measurement unit 150 and the SOC of the battery cell estimated by the SOC estimation unit 160.

[0085] Specifically, the ohmic resistance determination unit 110 can select only an impedance distribution in which the temperature and the SOC of the battery cell satisfy a predetermined condition among the plurality of impedance distributions. For example, even if the ohmic resistance determination unit 110 obtains 100 impedance distributions, if 10 impedance distributions satisfy the predetermined condition of the temperature and the SOC of the battery cell, the ohmic resistance determination unit 110 can select only the corresponding 10 impedance distributions.

[0086] In addition, the resistance change rate calculation unit 120 can be configured to calculate the resistance change rate based on the impedance distribution selected by the ohmic resistance determination unit 110.

[0087] For example, in the previous embodiment, when the ohmic resistance determination unit 110 selects only 10 impedance distributions among 100 impedance distributions, the ohmic resistance determination unit 110 can determine the ohmic resistance of the battery cell in each of the 10 impedance distributions. In addition, the resistance change rate calculation unit 120 can calculate the resistance change rate between the 10 determined ohmic resistances.

[0088] Hereinafter, the SOC estimation unit 160, the ohmic resistance determination unit 110, and the resistance change rate calculation unit 120 will be described in more detail. Figure 3 and Figure 4 The condition in which the ohmic resistance determination unit 110 selects the impedance distribution will be described in more detail.

[0089] Figure 4 is a graph schematically showing a plurality of other impedance distributions according to an embodiment of the disclosure.

[0090] The ohmic resistance determination unit 110 can be configured to select an impedance distribution in which the temperature of the corresponding battery cell is equal to or higher than a reference temperature and the SOC of the corresponding battery cell is equal to or greater than a reference SOC among the plurality of impedance distributions.

[0091] Generally, when the SOC of the battery cell is equal to or greater than a certain level, the amount of internal gas generated by the battery cell can increase as the temperature of the battery cell increases. That is, when the SOC of the battery cell is less than a certain level, the amount of internal gas generated by the battery cell itself is small, and thus the amount of internal gas generated by the battery cell does not increase even if the battery cell has a high temperature. Accordingly, when both the temperature and the SOC of the battery cell satisfy predetermined conditions, the ohmic resistance of the battery cell related to the amount of internal gas generated by the battery cell can increase.

[0092] Specifically, Figure 3 The plurality of impedance distributions shown in FIG. 1A are impedance distributions generated when the temperature of the battery cell is equal to or higher than a reference temperature and the SOC of the battery cell is equal to or greater than a reference SOC.

[0093] For example, in an embodiment of the battery 100 of FIG. 1A, the reference temperature can be 40°C, the temperature of the battery cell can be 55°C, the reference SOC can be 90%, and the SOC of the battery cell can be 100%. That is, Figure 3 The plurality of impedance distributions shown in FIG. 1A are impedance distributions generated when the temperature of the battery cell is equal to or higher than a reference temperature and the SOC of the battery cell is equal to or greater than a reference SOC. Figure 3 For example, in an embodiment of the battery 100 of FIG. 1A, the reference temperature can be 40°C, the temperature of the battery cell can be 55°C, the reference SOC can be 90%, and the SOC of the battery cell can be 100%. That is,

[0094] The plurality of impedance distributions shown in FIG. 1A are impedance distributions generated when the temperature of the battery cell is equal to or higher than a reference temperature and the SOC of the battery cell is equal to or greater than a reference SOC. Figure 4 For example, in an embodiment of the battery 100 of FIG. 1A, the reference temperature can be 40°C, the temperature of the battery cell can be 55°C, the reference SOC can be 90%, and the SOC of the battery cell can be 100%. That is,

[0095] The plurality of impedance distributions shown in FIG. 1A are impedance distributions generated when the temperature of the battery cell is equal to or higher than a reference temperature and the SOC of the battery cell is equal to or greater than a reference SOC. Figure 4 Figure 4 For example, in an embodiment of the battery 100 of FIG. 1A, the reference temperature can be 40°C, the temperature of the battery cell can be 55°C, the reference SOC can be 90%, and the SOC of the battery cell can be 100%. That is, The plurality of impedance distributions shown in FIG. 1A are impedance distributions generated when the temperature of the battery cell is equal to or higher than a reference temperature and the SOC of the battery cell is equal to or greater than a reference SOC.

[0096] Figure 3 In addition, Figure 4 The plurality of impedance distributions of the battery 100 of FIG. 1A are distributions of impedances measured by outputting the same current to the battery cell. That is, Figure 3 The difference between the impedance distributions of the battery 100 of FIG. 1A is the SOC of the battery cell at the time of measurement. Figure 4 Referring to FIG. 1A,

[0097] It can be clearly seen that the ohmic resistance of the battery cell increases as time elapses (for example, as the process progresses from the first impedance distribution P1 to the ninth impedance distribution P9). Figure 3 On the other hand, referring to FIG. 1B,

[0098] Figure 4 ​​It can be confirmed that the ohmic resistance of the battery cell remains in the approximate range even as time elapses. That is, in the case of Figure 4 , since the SOC of the battery cell is 0%, the battery cell itself does not generate gas or generates a small amount of gas. Therefore, even if the temperature of the battery cell is high, the ohmic resistance of the battery cell can remain in the approximate range.

[0099] That is, in order to diagnose the state of the battery cell considering the correlation between the internal gas generation level of the battery cell and the resistance change rate of the ohmic resistance of the battery cell, the temperature of the battery cell must be equal to or higher than the reference temperature at the time of measuring the impedance, and the SOC of the battery cell must also be equal to or greater than the reference SOC.

[0100] For example, according to the embodiment of Figure 4 , even when the battery cell is severely deteriorated and is in an unusable state, since the resistance change rate of the ohmic resistance is very small, there is a problem in that the internal gas generation level can be falsely diagnosed as normal and the state of the battery cell can be falsely diagnosed as a normal state. Specifically, according to the embodiment of Figure 4 , since the battery cell itself does not generate internal gas or a small amount thereof, the calculated resistance change rate of the ohmic resistance is low, and according to the calculated low resistance change rate, the battery cell can be falsely diagnosed as being in a normal state.

[0101] Therefore, the battery diagnosis apparatus 100 according to the embodiment of the disclosure has the advantage of more accurately diagnosing the internal gas generation level and the state of the battery cell by considering both the temperature and the SOC of the battery cell at the time of measuring the impedance.

[0102] Referring to Figure 1 , the battery diagnosis apparatus 100 can further include a charge transfer resistance determination unit 170.

[0103] The charge transfer resistance determination unit 170 can be configured to determine a charge transfer resistance (Rct) in each of the plurality of impedance distributions.

[0104] Here, the charge transfer resistance refers to a resistance generated in an oxidation reaction or a reduction reaction of lithium ions at an electrode material interface. It should be noted that since the charge transfer resistance is a well-known factor, a description of the charge transfer resistance itself will be omitted.

[0105] As described above, when the value of the imaginary part (-Zim) in the impedance distribution is 0, the resistance value of the real part (Zre) is the ohmic resistance (Ro) of the battery cell that can be determined by the ohmic resistance determination unit 110.

[0106] Alternatively, the ohmic resistance (Ro) of the battery cell in the impedance distribution and the resistance value (RTP) of the target peak TP can be used to determine the charge transfer resistance (Rct).TP The difference between the two values ​​determines the charge transfer resistance (Rct). Due to the characteristics of the impedance distribution, the resistance value (Rc) of the target peak TP is determined. TP The resistance (R) is always greater than the ohmic resistance (Ro), so it can be calculated using the formula "the resistance value of the target peak TP (R)". TP The charge transfer resistance is determined by the ohmic resistance (Ro).

[0107] That is, the charge transfer resistance determination unit 170 can determine the target peak value TP in each of the multiple impedance distributions, and based on the determined target peak value TP, the resistance value (R) is determined. TP The charge transfer resistance of each impedance distribution is determined by the difference between the resistance (Ro) and the resistance (Ro) determined by the ohmic resistance determination unit 110.

[0108] For example, in Figure 2 In this implementation, the impedance distribution may include a target peak value TP. Specifically, the target peak value TP may be a peak value in the impedance distribution where the instantaneous rate of change of the imaginary part (-Zim) relative to the real part (Zre) is 0 and has a downwardly convex open shape. That is, based on the target peak value TP, as the resistance value of the real part (Zre) increases, the instantaneous rate of change of the imaginary part (-Zim) relative to the real part (Zre) can change from negative to positive.

[0109] For example, in Figure 3 In this embodiment, the charge transfer resistance determining unit 170 can determine the charge transfer resistance of each of the first impedance distribution P1 to the ninth resistance distribution P9. Here, the charge transfer resistance of the first impedance distribution P1 can be the smallest, and the charge transfer resistance of the ninth impedance distribution P9 can be the largest. That is, the magnitudes of the charge transfer resistances of the first impedance distribution P1 to the ninth resistance distribution P9 can increase sequentially.

[0110] The resistance change rate calculation unit 120 can be configured to also calculate the charge transfer resistance change rate among the determined multiple charge transfer resistors.

[0111] That is, the resistance change rate calculation unit 120 can calculate the resistance change rate of multiple ohmic resistors determined by the ohmic resistance determination unit 110, and calculate the charge transfer resistance change rate of multiple charge transfer resistors determined by the charge transfer resistance determination unit 170.

[0112] The condition diagnostic unit 140 can be configured to further diagnose the condition of the battery cell based on a comparison of the calculated charge transfer resistance change rate with a reference resistance value.

[0113] Specifically, the state diagnosis unit 140 can be configured to diagnose the state of the battery cell as normal when the calculated rate of change of charge transfer resistance is less than a reference resistance value.

[0114] In addition, the state diagnosis unit 140 can be configured to diagnose the state of the battery cell as a warning state when the calculated charge transfer resistance change rate is equal to or greater than the reference resistance value. In addition, the state diagnosis unit 140 can be configured to reduce the maximum allowable C-rate for charging and discharging of the battery cell. Here, the C-rate (current rate) means the charging / discharging rate of the battery cell.

[0115] That is, when the state of the battery cell is diagnosed as a warning state, the state diagnosis unit 140 can reduce the maximum allowable C-rate of the battery cell in order to reduce the charge transfer resistance. Accordingly, the maximum allowable value of the charging C-rate and the discharging C-rate of the battery cell can be reduced.

[0116] For example, when diagnosing the states of a plurality of battery cells collected for reuse, the battery diagnosis apparatus 100 according to the embodiment of the disclosure can consider the charge transfer resistance in addition to the ohmic resistance. The battery cell diagnosed as a normal state based on the charge transfer resistance can be reused without an additional setting change, but the battery cell diagnosed as a warning state can be reused after the maximum allowable C-rate is set to be reduced.

[0117] As such, the battery diagnosis apparatus 100 according to the embodiment of the disclosure can diagnose the state of the battery cell based on the ohmic resistance of the battery cell determined with the impedance distribution, and can also diagnose the state of the battery cell based on the charge transfer resistance of the battery cell determined with the impedance distribution. That is, since the battery diagnosis apparatus 100 can diagnose the state of the battery cell in two ways, there is an advantage that the state of the battery cell can be more accurately diagnosed.

[0118] Figure 5 FIG. 1 is a diagram schematically illustrating a battery diagnosis system 10 according to an embodiment of the disclosure.

[0119] Referring to Figure 5 , the battery diagnosis system 10 can include a battery diagnosis apparatus 100 and an EIS unit 200.

[0120] The EIS unit 200 can be configured to output an AC current to a battery cell and generate an impedance distribution representing the impedance of the battery cell as a correspondence between a real part (Zre) and an imaginary part (-Zim) according to an output result of the AC current.

[0121] Specifically, the EIS unit 200 can be configured to perform EIS (Electrochemical Impedance Spectroscopy). Accordingly, the EIS unit 200 can apply a small AC current to the battery cell to measure the impedance of the battery cell and generate an impedance distribution representing the impedance as a correspondence between a real part (Zre) and an imaginary part (-Zim).

[0122] The EIS unit 200 can be configured to output the generated impedance distribution to the battery diagnosis device 100.

[0123] For example, the EIS unit 200 can transmit the generated impedance distribution to the ohmic resistance determination unit 110 and the charge transfer resistance determination unit 170 of the battery diagnosis device 100.

[0124] As another example, the EIS unit 200 can transmit the generated impedance distribution to a storage unit of the battery diagnosis device 100. In this case, the ohmic resistance determination unit 110 and the charge transfer resistance determination unit 170 can access the storage unit to acquire the impedance distribution generated by the EIS unit 200.

[0125] In addition, referring to Figure 5 , the battery diagnosis system 10 can further include a heating unit 300 and a charging unit 400.

[0126] The heating unit 300 can be configured to raise the temperature of the battery cell such that the temperature of the battery cell is equal to or higher than a reference temperature.

[0127] The charging unit 400 can be configured to charge the battery cell such that the SOC of the battery cell is equal to or greater than a reference SOC.

[0128] Preferably, the operations of the heating unit 300 and the charging unit 400 can be controlled by the battery management system. For example, the operations of the heating unit 300 and the charging unit 400 can be controlled by the state diagnosis unit 140.

[0129] As described above, referring to Figure 3 , when the temperature of the battery cell is equal to or higher than the reference temperature and the SOC of the battery cell is equal to or greater than the reference SOC, the ohmic resistance of the battery cell can gradually increase among the plurality of impedance distributions.

[0130] Therefore, since the temperature of the battery cell becomes equal to or higher than the reference temperature due to the heating unit 300 and the SOC of the battery cell becomes equal to or greater than the reference SOC due to the charging unit 400, the impedance distribution generated by the EIS unit 200 under this condition can be selected as an impedance distribution for diagnosing the state of the battery cell. That is, based on the impedance distribution generated under this condition, the state of the battery cell can be diagnosed.

[0131] Therefore, only when the temperature and the SOC of the battery cell satisfy the predetermined condition, the battery diagnosis system 10 can diagnose the state of the battery cell based on the corresponding impedance distribution, and thus the accuracy and reliability of the state diagnosis of the battery cell can be high.

[0132] The battery diagnostic device 100 according to the present disclosure can be applied to a BMS (Battery Management System). That is, the BMS according to the present disclosure can include the above-described battery diagnostic device 100. In this configuration, at least some components of the battery diagnostic device 100 can be implemented by supplementing or adding functions of configurations included in a conventional BMS.

[0133] In addition, the battery diagnostic device 100 according to the present disclosure can be provided for a battery pack 1. That is, the battery pack 1 according to the present disclosure can include the above-described battery diagnostic device 100 and at least one battery cell. In addition, the battery pack 1 can further include electrical devices (relays, fuses, etc.) and a housing.

[0134] Figure 6 FIG. 1 is a diagram schematically showing an exemplary configuration of a battery pack 1 according to another embodiment of the present disclosure. Referring to FIG. 1, the battery pack 1 can include a battery diagnostic device 100, an EIS unit 200, a heating unit 300, and a charging unit 400. Figure 6

[0135] For example, in the embodiment of FIG. 1, the battery diagnostic device 100 can be connected to first to fourth sensing lines SL1 to SL4. Preferably, the first to fourth sensing lines SL1 to SL4 can be connected to a measurement unit 150 of the battery diagnostic device 100. Figure 6

[0136] The measurement unit 150 can measure the temperature of the battery cell B through the first sensing line SL1.

[0137] In addition, the measurement unit 150 can measure the positive voltage of the battery cell B through the second sensing line SL2 and the negative voltage of the battery cell B through the third sensing line SL3. In addition, the measurement unit 150 can measure the voltage of the battery cell B by calculating the difference between the measured positive voltage and the negative voltage of the battery cell B.

[0138] In addition, the measurement unit 150 can be connected to a current measuring element A through the fourth sensing line SL4. Here, the current measuring element A can be a current system or a shunt resistor. Accordingly, the measurement unit 150 can measure the current of the battery cell B through the fourth sensing line SL4. Figure 6 An embodiment in which the current measuring element A, which is a preferred embodiment, is disposed between the negative electrode of the battery cell B and the negative terminal P- of the battery pack 1 is shown, but the current measuring element A can also be disposed between the positive electrode of the battery cell B and the positive terminal P+ of the battery pack 1.

[0139] ​​One end of the EIS unit 200 can be connected between the positive terminal P+ of the battery pack 1 and the positive electrode of the battery cell B, and the other end can be connected between the negative terminal P- of the battery pack 1 and the negative electrode of the battery cell B. Also, the EIS unit 200 can measure the impedance of the battery cell B after outputting a small AC current. Thereafter, the EIS unit 200 can generate and transmit the impedance distribution of the battery cell B to the battery diagnosis apparatus 100.

[0140] One end of the heating unit 300 can be connected to the positive electrode of the battery cell B, and the other end can be connected to the negative electrode of the battery cell B. Also, the operation of the heating unit 300 is controlled by the battery diagnosis apparatus 100 (particularly, the state diagnosis unit 140), and when the heating unit 300 operates, the temperature of the battery cell B can increase.

[0141] One end of the charging unit 400 can be connected to the positive terminal P+ of the battery pack 1, and the other end can be connected to the negative terminal P- of the battery pack 1. In another embodiment, one end of the charging unit 400 can be directly connected to the positive electrode of the battery cell B, and the other end can be directly connected to the negative electrode of the battery cell B, similar to the heating unit 300. The operation of the charging unit 400 can be controlled by the battery diagnosis apparatus 100 (particularly, the state diagnosis unit 140), and when the charging unit 400 operates, the battery cell B can be charged.

[0142] Figure 7 FIG. 4 is a diagram schematically illustrating a battery diagnosis method according to yet another embodiment of the disclosure.

[0143] Here, each step of the battery diagnosis method can be performed by the battery diagnosis apparatus 100. Hereinafter, for convenience of explanation, overlapping content with the previously described content will be briefly described or omitted.

[0144] The battery diagnosis method can include an ohmic resistance determination step (S100), a resistance change rate calculation step (S200), a gas generation level determination step (S300), and a state diagnosis step (S400).

[0145] The ohmic resistance determination step (S100) is a step of determining the ohmic resistance of the battery cell B in each of a plurality of impedance distributions generated at different time points with respect to the battery cell B, and can be performed by the ohmic resistance determination unit 110.

[0146] For example, in an embodiment of FIG. 1, Figure 4 In an embodiment of FIG. 1, the ohmic resistance determination unit 110 can obtain the first impedance distribution P1 to the ninth impedance distribution P9. Also, the ohmic resistance determination unit 110 can determine the ohmic resistance of the battery cell B in each of the first impedance distribution P1 to the ninth impedance distribution P9.

[0147] The resistance change rate calculation step (S200) is a step of calculating a resistance change rate between the determined plurality of ohmic resistances, and can be performed by the resistance change rate calculation unit 120.

[0148] For example, in an embodiment of the present disclosure, when the ohmic resistances are determined by the ohmic resistance determination unit 110 in each of the first to ninth impedance distributions P1 to P9, the resistance change rate calculation unit 120 can calculate the resistance change rates of the 9 ohmic resistances. Figure 4

[0149] The gas generation level determination step (S300) is a step of determining the internal gas generation level of the battery cell B based on the calculated resistance change rates, and can be performed by the gas generation level determination unit 130.

[0150] The gas generation level determination unit 130 can determine the internal gas generation level corresponding to the region to which the calculated resistance change rate belongs by substituting the resistance change rate calculated by the resistance change rate calculation unit 120 into the preset reference change rate region.

[0151] The state diagnosis step (S400) is a step of diagnosing the state of the battery cell B according to the determined internal gas generation level, and can be performed by the state diagnosis unit 140.

[0152] The state diagnosis unit 140 can diagnose the state of the battery cell B corresponding to the internal gas generation level of the battery cell B determined by the gas generation level determination unit 130.

[0153] For example, if the internal gas generation level is normal, the state diagnosis unit 140 can diagnose that the state of the battery cell B is a normal state. If the internal gas generation level is warning, the state diagnosis unit 140 can diagnose that the state of the battery cell B is a warning state. If the internal gas generation level is danger, the state diagnosis unit 140 can diagnose that the state of the battery cell B is an unusable state.

[0154] The above-described embodiments of the present disclosure can be implemented not only by devices, methods, and systems but also by programs implementing functions corresponding to the configurations of the embodiments of the present disclosure or recording media having the programs recorded thereon. The programs or recording media can be easily implemented by those skilled in the art from the above description of the embodiments.

[0155] The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present disclosure, are given by way of illustration only, since various changes and modifications within the scope of the present disclosure will become apparent to those skilled in the art from this detailed description.

[0156] ​In addition, those skilled in the art can make many substitutions, modifications and changes to the present disclosure described above without departing from the technical aspects of the present disclosure, and the present disclosure is not limited to the above-described embodiments and drawings, and each embodiment can be selectively combined in part or in whole to allow various modifications.

[0157] (Reference Signs)

[0158] 1: battery pack

[0159] 10: battery diagnosis system

[0160] 100: battery diagnosis device

[0161] 110: ohmic resistance determination unit

[0162] 120: resistance change rate calculation unit

[0163] 130: gas generation level determination unit

[0164] 140: state diagnosis unit

[0165] 150: measurement unit

[0166] 160: SOC estimation unit

[0167] 170: charge transfer resistance determination unit

[0168] 200: EIS unit

[0169] 300: heating unit

[0170] 400: charging unit

[0171] B: battery cell

Claims

1. A battery diagnostic device, the battery diagnostic device comprising: An ohmic resistance determination unit is configured to determine the ohmic resistance of the battery cell in each of a plurality of impedance distributions generated for the battery cell at different time points. A resistance change rate calculation unit is configured to calculate the resistance change rate among a plurality of determined ohmic resistors; A gas generation level determination unit is configured to determine the internal gas generation level of the battery cell based on a calculated rate of change of resistance. as well as A status diagnostic unit is configured to diagnose the status of the battery cell based on a determined level of internal gas generation.

2. The battery diagnostic device according to claim 1, in, The gas generation level determination unit is configured to determine the internal gas generation level of the battery cell based on the region to which the calculated resistance change rate belongs within a preset reference change rate region.

3. The battery diagnostic device according to claim 2, in, The reference rate of change region is preset according to the level of internal gas generation as a first region less than the first reference resistance rate of change, a second region equal to or greater than the first reference resistance rate of change and less than the second reference resistance rate of change, and a third region equal to or greater than the second reference resistance rate of change.

4. The battery diagnostic device according to claim 3, in, The gas generation level determination unit is configured to determine the internal gas generation level as normal when the calculated resistance change rate belongs to the first region, to determine the internal gas generation level as a warning when the calculated resistance change rate belongs to the second region, and to determine the internal gas generation level as dangerous when the calculated resistance change rate belongs to the third region.

5. The battery diagnostic device according to claim 4, in, The status diagnostic unit is configured as follows: When the level of internal gas generation is determined to be normal, the state of the battery cell is diagnosed as normal. When the internal gas generation level is determined to be a warning level, the state of the battery cell is diagnosed as a warning state, and at least one of the maximum allowable temperature and the maximum allowable state of charge (SOC) is reduced. When the level of internal gas generation is determined to be dangerous, the state of the battery cell is diagnosed as unusable.

6. The battery diagnostic device according to claim 1, further comprising: A measuring unit configured to measure at least one of the temperature, voltage, and current of the battery cell; as well as A State of Charge (SOC) estimation unit is configured to estimate the SOC of the battery cell based on at least one of a measured voltage and current.

7. The battery diagnostic device according to claim 6, in, The ohmic resistance determination unit is configured to select at least one impedance distribution that satisfies predetermined conditions from the plurality of impedance distributions based on the temperature of the battery cell measured by the measurement unit and the SOC of the battery cell estimated by the SOC estimation unit. The resistance change rate calculation unit is configured to calculate the resistance change rate based on the impedance distribution selected by the ohmic resistance determination unit.

8. The battery diagnostic device according to claim 7, in, The ohmic resistance determination unit is configured to select, from the plurality of impedance distributions, the impedance distribution corresponding to the battery cell whose temperature is equal to or higher than the reference temperature and whose state of charge (SOC) is equal to or greater than the reference SOC.

9. The battery diagnostic device according to claim 1, further comprising: A charge transfer resistance determination unit is configured to determine the charge transfer resistance in each of the plurality of impedance distributions. The resistance change rate calculation unit is configured to further calculate the charge transfer resistance change rate among the determined plurality of charge transfer resistors, and The state diagnosis unit is configured to further diagnose the state of the battery cell based on a comparison between the calculated charge transfer resistance change rate and a reference resistance value.

10. The battery diagnostic device according to claim 9, in, The status diagnostic unit is configured as follows: When the calculated rate of change of charge transfer resistance is less than the reference resistance value, the state of the battery cell is diagnosed as normal, and When the calculated rate of change of charge transfer resistance is equal to or greater than the reference resistance value, the state of the battery cell is diagnosed as a warning state, and the maximum permissible C rate of charging and discharging of the battery cell is reduced.

11. A battery diagnostic system, the battery diagnostic system comprising: Battery diagnostic device according to any one of claims 1 to 10; as well as An electrochemical impedance spectroscopy (EIS) unit is configured to output an AC current to the battery cell, generate an impedance distribution that represents the impedance of the battery cell as a correspondence between the real and imaginary parts based on the output of the AC current, and output the generated impedance distribution to the battery diagnostic device.

12. The battery diagnostic system according to claim 11, further comprising: A heating unit configured to raise the temperature of the battery cell, such that the temperature of the battery cell becomes equal to or higher than a reference temperature; as well as A charging unit configured to charge the battery cell such that the state of charge (SOC) of the battery cell becomes equal to or greater than a reference SOC.

13. A battery pack comprising a battery diagnostic device according to any one of claims 1 to 10.

14. A battery diagnostic method, the battery diagnostic method comprising: The ohmic resistance determination step determines the ohmic resistance of the battery cell in each of a plurality of impedance distributions generated for the battery cell at different time points. The resistance change rate calculation step calculates the resistance change rate among the determined multiple ohmic resistors. A gas generation level determination step, wherein the gas generation level determination step determines the internal gas generation level of the battery cell based on a calculated rate of change of resistance; as well as A condition diagnosis step, wherein the condition diagnosis step diagnoses the condition of the battery cell based on a determined level of internal gas generation.

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