Patent Publication Number: US-2023141623-A1

Title: Battery Diagnosing Apparatus And Method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2021/014051 filed Oct. 12, 2021, which claims priority from Korean Patent Application No. 10-2020-0131450 filed Oct. 12, 2020, all of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a battery diagnosing apparatus and method, and more particularly, to a battery diagnosing apparatus and method capable of diagnosing an internal gas generation level and an internal gas generation cause of a battery. 
     BACKGROUND ART 
     Recently, the demand for portable electronic products such as notebook computers, video cameras and portable telephones has increased sharply, and electric vehicles, energy storage batteries, robots, satellites and the like have been developed in earnest. Accordingly, high-performance batteries allowing repeated charging and discharging are being actively studied. 
     Batteries commercially available at present include nickel-cadmium batteries, nickel hydrogen batteries, nickel-zinc batteries, lithium batteries and the like. Among them, the lithium batteries are in the limelight since they have almost no memory effect compared to nickel-based batteries and also have very low self-charging rate and high energy density. 
     As the battery is degraded, various side reactions accompanied by generation of internal gas occur. If the side reaction continues and the amount of internal gas exceeds an allowable value, the junction portion of the battery is opened, and the battery reaches an EOL (End Of Life) state. 
     Therefore, in order to diagnose the state of the battery, it is required to measure the internal gas amount, but in the prior art, it is difficult to measure the internal gas amount of the battery in a non-destructive manner. 
     SUMMARY 
     Technical Problem 
     The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery diagnosing apparatus and method for diagnosing an internal gas generation level and an internal gas generation cause of a battery in a non-destructive manner based on an impedance profile of the battery. 
     These and other objects and advantages of the present disclosure may be understood from the following detailed description and will become more fully apparent from the exemplary embodiments of the present disclosure. Also, it will be easily understood that the objects and advantages of the present disclosure may be realized by the means shown in the appended claims and combinations thereof. 
     Technical Solution 
     A battery diagnosing apparatus according to one aspect of the present disclosure may comprise: a voltage sensor configured to measure a voltage of a battery; a temperature sensor configured to measure a temperature of the battery; a controller; and memory having programmed thereon instructions that, when executed by the controller, cause the controller to: calculate a voltage change amount by comparing the voltage of the battery with a reference voltage; calculate a resistance change rate by comparing an ohmic resistance determined based on an impedance profile generated for the battery with a reference resistance; determine an internal gas generation level of the battery by comparing magnitudes of the calculated resistance change rate and a threshold resistance change rate; and determine an internal gas generation cause of the battery by comparing magnitudes of the calculated voltage change amount and a threshold voltage change amount. 
     The ohmic resistance may be determined based on the impedance profile generated for the battery in response to the temperature of the battery being equal to or greater than a threshold temperature of the battery for a predetermined duration of time. 
     The instructions may be configured to cause the controller to determine that an internal gas of the battery equal to or greater than a threshold amount is generated in response to the calculated resistance change rate being equal to or greater than the threshold resistance change rate. 
     The instructions may be configured to cause the controller to determine that an internal gas of the battery less than the threshold amount is generated, in response to the calculated resistance change rate being less than the threshold resistance change rate. 
     The instructions may be configured to cause the controller to determine that the internal gas generation cause is a side reaction of a positive electrode of the battery in response to the calculated voltage change amount being equal to or greater than the threshold voltage change amount. 
     The instructions may be configured to cause the controller to determine that the internal gas generation cause is a cause other than the side reaction of the positive electrode in response to the calculated voltage change amount being less than the threshold voltage change amount. 
     The instructions may be configured to cause the controller to diagnose a state of the battery based on the internal gas generation level and the internal gas generation cause. 
     The instructions may be configured to cause the controller to diagnose that the state of the battery is a normal state in response to the internal gas generation level being less than the threshold amount and being generated due to the cause other than the side reaction of the positive electrode. 
     The instructions may be configured to cause the controller to diagnose that the state of the battery is a first warning state in response to the internal gas generation level being equal to or greater than the threshold amount is generated and being generated due to the cause other than the side reaction of the positive electrode and reduce an upper limit temperature for the battery in response to the state of the battery being the first warning state. 
     The instructions may be configured to cause the controller to diagnose that the state of the battery is a second warning state in response to the internal gas generation level being equal to or greater than the threshold amount and being generated due to the side reaction of the positive electrode and reduce at least one of an upper limit temperature and an upper limit SOC for the battery in response to the state of the battery being the second warning state. 
     The instructions may be configured to cause the controller to determine an occurrence of an internal short in the battery in response to the internal gas generation level being less than the threshold amount and being generated due to the side reaction of the positive electrode and diagnose that the state of the battery is an unusable state. 
     A battery diagnosing system according to another aspect of the present disclosure may comprise: the battery diagnosing apparatus according to an aspect of any of the embodiments of the present disclosure; and electrochemical impedance spectroscopy (EIS) instrument configured to output an AC current to the battery, generate the impedance profile according to an output result of the AC current as a corresponding relationship between a real part and an imaginary part, and output the generated impedance profile to the battery diagnosing apparatus. 
     A battery diagnosing system according to another aspect of the present disclosure may further comprise a heater configured to raise the temperature of the battery to a raised temperature that is equal to or greater than a threshold temperature. 
     A battery pack according to still another aspect of the present disclosure may comprise the battery diagnosing apparatus according to an aspect of any of the embodiments of the present disclosure. 
     A battery diagnosing method according to still another aspect of the present disclosure may comprise: measuring, by each of a voltage sensor and a temperature sensor, a voltage and a temperature of a battery, respectively; calculating, by a controller, a voltage change amount by comparing the measured voltage of the battery with a reference voltage; calculating, by the controller, a resistance change rate by comparing, by the controller, an ohmic resistance of the battery determined based on an impedance profile generated for the battery with a reference resistance; determining, by the controller, an internal gas generation level of the battery by comparing magnitudes of the calculated resistance change rate and a threshold resistance change rate; and determining, by the controller, an internal gas generation cause of the battery by comparing magnitudes of the calculated voltage change amount and a threshold voltage change amount. 
     Advantageous Effects 
     According to one aspect of the present disclosure, an internal gas generation level and an internal gas generation cause of a battery may be diagnosed in a non-destructive manner. 
     The effects of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate a preferred embodiment of the present disclosure and together with the foregoing disclosure, serve to provide further understanding of the technical features of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawing. 
         FIG.  1    is a diagram schematically showing a battery diagnosing apparatus according to an embodiment of the present disclosure. 
         FIG.  2    is a diagram schematically showing an impedance profile according to an embodiment of the present disclosure. 
         FIG.  3    is a diagram showing an example of a voltage change amount calculated by the battery diagnosing apparatus according to an embodiment of the present disclosure. 
         FIG.  4    is a diagram showing an example of a resistance change rate calculated by the battery diagnosing apparatus according to an embodiment of the present disclosure. 
         FIG.  5    is a diagram schematically showing a state of a battery diagnosed by the battery diagnosing apparatus according to an embodiment of the present disclosure. 
         FIG.  6    is a diagram schematically showing a battery diagnosing system according to another embodiment of the present disclosure. 
         FIG.  7    is a diagram showing an exemplary configuration of a battery pack including the battery diagnosing apparatus according to an embodiment of the present disclosure. 
         FIG.  8    is a diagram showing a battery diagnosing method according to still another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. 
     Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the disclosure, so it should be understood that other equivalents and modifications could be made thereto without departing from the scope of the disclosure. 
     Additionally, in describing the present disclosure, when it is deemed that a detailed description of relevant known elements or functions renders the key subject matter of the present disclosure ambiguous, the detailed description is omitted herein. 
     The terms including the ordinal number such as “first”, “second” and the like, may be used to distinguish one element from another among various elements, but not intended to limit the elements by the terms. 
     Throughout the specification, when a portion is referred to as “comprising” or “including” any element, it means that the portion may include other elements further, without excluding other elements, unless specifically stated otherwise. 
     In addition, terms such as a control unit described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. 
     In addition, throughout the specification, when a portion is referred to as being “connected” to another portion, it is not limited to the case that they are “directly connected”, but it also includes the case where they are “indirectly connected” with another element being interposed between them. 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a diagram schematically showing a battery diagnosing apparatus  100  according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , the battery diagnosing apparatus  100  according to an embodiment of the present disclosure may include a measuring unit  110 , an ohmic resistance determining unit  120 , and a control unit  130 . 
     The measuring unit  110  may be configured to measure voltage and temperature of a battery. 
     Here, the battery means a single independent cell that has a negative electrode terminal and a positive electrode terminal and is physically separable. For example, one pouch-type lithium polymer cell may be regarded as a battery. Also, the battery may be a battery module in which one or more batteries are connected in series and/or in parallel. However, hereinafter, for convenience of explanation, a battery will be described as meaning an independent cell. 
     For example, the measuring unit  110  may be electrically connected to the positive electrode terminal and the negative electrode terminal of the battery to measure the voltage of the battery. In addition, the measuring unit  110  may measure the voltage of the battery by measuring a positive electrode voltage and a negative electrode voltage of the battery, and calculate a difference between the measured positive electrode voltage and the measured negative electrode voltage. Preferably, the measuring unit  110  may measure an OCV (Open Circuit Voltage) of the battery. 
     In addition, the measuring unit  110  may be connected to the battery to measure a current temperature of the battery. 
     The ohmic resistance determining unit  120  may be configured to determine an ohmic resistance of the battery based on an impedance profile generated for the battery. 
       FIG.  2    is a diagram schematically showing an impedance profile according to an embodiment of the present disclosure. 
     Referring to  FIG.  2   , the impedance profile may be expressed as an X-Y plane graph when X is set as a real part (Zre) and Y is set as an imaginary part (-Zim). In the embodiment of  FIG.  2   , the ohmic resistance (Ro) of the battery may be a starting resistance value of the impedance profile. Specifically, in the impedance profile, the resistance value of the real part (Zre) when the value of the imaginary part (-Zim) is 0 may be the ohmic resistance (Ro) of the battery. Since the ohmic resistance (Ro) is a widely known factor, it should be noted that a description of the ohmic resistance (Ro) will be omitted. 
     For example, the impedance profile of the battery may be generated outside the battery diagnosing apparatus  100 . In addition, the ohmic resistance determining unit  120  may directly receive the impedance profile of the battery generated in the outside or may acquire the impedance profile by accessing a memory in which the impedance profile of the battery is stored. 
     Then, the ohmic resistance determining unit  120  may determine a starting resistance value from the received impedance profile, and determine the determined starting resistance value as the ohmic resistance of the battery. 
     The control unit  130  may be configured to calculate a voltage change amount by comparing the voltage of the battery measured by the measuring unit  110  with a reference voltage. 
     Here, the reference voltage may be a voltage value measured in advance with respect to a battery in a BOL (Beginning Of Life) state. More preferably, the reference voltage may be an OCV value measured when a SOC (State Of Charge) of the battery in the BOL state is 100%. 
     Specifically, the control unit  130  may calculate a difference between the reference voltage and the measured voltage of the battery to calculate a voltage change amount for the battery. For example, the control unit  130  may calculate a voltage change amount for the battery by calculating the formula “reference voltage−measured voltage of the battery”. 
       FIG.  3    is a diagram showing an example of the voltage change amount calculated by the battery diagnosing apparatus  100  according to an embodiment of the present disclosure. 
     For example, in the embodiment of  FIG.  3   , the control unit  130  may calculate a voltage change amount for first to sixth batteries B 1  to B 6 . Here, the reference voltage may be preset for each of the first to sixth batteries B 1  to B 6 . That is, a first reference voltage for the first battery B 1  and a second reference voltage for the second battery B 2  may be preset. In addition, a third reference voltage for the third battery B 3  and a fourth reference voltage for the fourth battery B 4  may be preset. Also, a fifth reference voltage for the fifth battery B 5  and a sixth reference voltage for the sixth battery B 6  may be preset. 
     That is, the control unit  130  does not calculate the voltage change amount of the first to sixth batteries B 1  to B 6  by using one preset reference voltage, but may calculate the voltage change amount for each of the first to sixth batteries B 1  to B 6  by calculating the difference between the corresponding reference voltage and the measured voltage of the battery. Accordingly, the degree of degradation of each battery may be reflected in the voltage change amount of the battery calculated by the control unit  130 . 
     For example, in the embodiment of  FIG.  3   , the voltage change amount of the first battery B 1  may be 86.9 mV, and the voltage change amount of the second battery B 2  may be 148.1 mV. Also, the voltage change amount of the third battery B 3  may be 97.3 mV, and the voltage change amount of the fourth battery B 4  may be 83.8 mV. Also, the voltage change amount of the fifth battery B 5  may be 119.8 mV, and the voltage change amount of the sixth battery B 6  may be 87.3 mV. 
     The control unit  130  may be configured to calculate a resistance change rate by comparing the ohmic resistance determined by the ohmic resistance determining unit  120  with a reference resistance. 
     Here, the reference resistance may be a resistance value measured in advance for the battery in the BOL state. More preferably, the reference resistance may be an ohmic resistance value measured when the SOC (State Of Charge) of the battery in the BOL state is 100%. 
     Specifically, the control unit  130  may calculate a resistance change rate for the battery by calculating a ratio of a difference between the reference resistance and the measured ohmic resistance of the battery for the reference resistance. For example, the control unit  130  may calculate the resistance change rate for the battery by calculating the formula “(measured ohmic resistance of the battery−reference resistance)÷reference resistance×100”. 
       FIG.  4    is a diagram showing an example of the resistance change rate calculated by the battery diagnosing apparatus  100  according to an embodiment of the present disclosure. 
     For example, in the embodiment of  FIG.  4   , the control unit  130  may calculate a resistance change rate of the first to sixth batteries B 1  to B 6 . Like the reference voltage, the reference resistance may also be preset for each of the first to sixth batteries B 1  to B 6 . That is, a first reference resistance for the first battery B 1  and a second reference resistance for the second battery B 2  may be preset. In addition, a third reference resistance for the third battery B 3  and a fourth reference resistance for the fourth battery B 4  may be preset. In addition, a fifth reference resistance for the fifth battery B 5  and a sixth reference resistance for the sixth battery B 6  may be preset. In addition, the control unit  130  may calculate a resistance change rate of each of the first to sixth batteries B 1  to B 6  based on the corresponding reference resistance and the ohmic resistance of the battery. 
     For example, in the embodiment of  FIG.  4   , the resistance change rate of the first battery B 1  may be 16.4%, and the resistance change rate of the second battery B 2  may be 13.8%. In addition, the resistance change rate of the third battery B 3  may be 17.1%, and the resistance change rate of the fourth battery B 4  may be 16.1%. In addition, the resistance change rate of the fifth battery B 5  may be 24.2%, and the resistance change rate of the sixth battery B 6  may be 25.2%. 
     The control unit  130  may be configured to judge an internal gas generation level of the battery by comparing magnitudes of the calculated resistance change rate and a criterion resistance change rate. 
     Specifically, the control unit  130  may be configured to judge that an internal gas of the battery equal to or greater than a criterion amount is generated, when the calculated resistance change rate is equal to or greater than the criterion resistance change rate. In addition, the control unit  130  may be configured to judge that an internal gas of the battery less than the criterion amount is generated, when the calculated resistance change rate is less than the criterion resistance change rate. Here, the case where the internal gas of the battery less than the criterion amount is generated may include both the case where the internal gas of the battery less than the criterion amount is generated and the case where the internal gas is not generated. 
     For example, in the embodiment of  FIG.  4   , it is assumed that the criterion resistance change rate is preset to 20%. Since the resistance change rates of the first to fourth batteries B 1  to B 4  are smaller than the criterion resistance change rate, the control unit  130  may judge that the internal gas of the first to fourth batteries B 1  to B 4  less than the criterion amount is generated. In addition, since the resistance change rates of the fifth and sixth batteries B 5 , B 6  are greater than the criterion resistance change rate, the control unit  130  may judge that the internal gas of the fifth and sixth batteries B 5 , B 6  greater than the criterion amount is generated. 
     The control unit  130  may be configured to judge an internal gas generation cause of the battery by comparing magnitudes of the calculated voltage change amount and a criterion voltage change amount. 
     Specifically, the control unit  130  may be configured to judge that the internal gas generation cause is a side reaction of the positive electrode of the battery, when the calculated voltage change amount is greater than or equal to the criterion voltage change amount. More preferably, the control unit  130  may be configured to judge that the internal gas generation cause is a side reaction of the positive electrode and an electrolyte of the battery, when the calculated voltage change amount is greater than or equal to the criterion voltage change amount. 
     In addition, the control unit  130  may be configured to judge that the internal gas generation cause is another cause other than the side reaction of the positive electrode, when the calculated voltage change amount is less than the criterion voltage change amount. For example, another cause may include a side reaction of the negative electrode of the battery. 
     For example, in the embodiment of  FIG.  3   , it is assumed that the criterion voltage change amount is preset to 110 mV. Since the voltage change amounts of the first battery B 1 , the third battery B 3 , the fourth battery B 4 , and the sixth battery B 6  are smaller than the criterion voltage change amount, the control unit  130  may judge that the internal gases of the first battery B 1 , the third battery B 3 , the fourth battery B 4 , and the sixth battery B 6  are caused by another cause. In addition, since the voltage change amounts of the second and fifth batteries B 2 , B 5  are greater than the criterion voltage change amount, the control unit  130  may judge that the internal gases of the second and fifth batteries B 2 , B 5  are generated by the side reaction of the positive electrode of the corresponding battery. 
     That is, the battery diagnosing apparatus  100  according to an embodiment of the present disclosure may judge whether the internal gas of the battery equal to or greater than the criterion amount is generated and whether the internal gas of the battery is generated due to any side reaction. In particular, the battery diagnosing apparatus  100  has an advantage of diagnosing in a non-destructive manner whether the internal gas of the battery is generated due to the side reaction of the positive electrode of the battery. 
     For example, when diagnosing the state of one or more batteries collected for reuse, the battery diagnosing apparatus  100  according to an embodiment of the present disclosure may be used. The battery diagnosing apparatus  100  may diagnose the internal gas generation level and the internal gas generation cause for each of one or more batteries in a non-destructive manner Therefore, according to an embodiment of the present disclosure, because the internal gas generation level and the internal gas generation cause of the battery may be quickly and easily diagnosed based on the ohmic resistance and the voltage of the battery, it may be judged quickly and accurately whether the collected batteries are reusable. 
     Meanwhile, the control unit  130  provided to the battery diagnosing apparatus  100  may optionally include a processor, an application-specific integrated circuit (ASIC), another chipset, a logic circuit, a register, a communication modem, and a data processing device, and the like, known in the art to execute various control logics performed in the present disclosure. In addition, when the control logic is implemented in software, the control unit  130  may be implemented as a set of program modules. At this time, the program module may be stored in a memory and executed by the control unit  130 . The memory may be provided in or out of the control unit  130 , and may be connected to the control unit  130  by various well-known means. 
     In addition, referring to  FIG.  1   , the battery diagnosing apparatus  100  may further include a storage unit  140 . The storage unit  140  may store data or programs necessary for operation and function of each component of the battery diagnosing apparatus  100 , data generated in the process of performing the operation or function, or the like. The storage unit  140  is not particularly limited in its kind as long as it is a known information storage means that can record, erase, update and read data. As an example, the information storage means may include random-access memory (RAM), flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), registers, and the like. In addition, the storage unit  140  may store program codes in which processes executable by the control unit  130  are defined. 
     For example, the storage unit  140  may store a reference voltage and a reference resistance for each battery. In addition, the storage unit  140  may store the impedance profile of the battery. In this case, the ohmic resistance determining unit  120  may access the storage unit  140  to obtain the impedance profile of the battery. 
     Preferably, the ohmic resistance determining unit  120  may be configured to determine the ohmic resistance based on the impedance profile generated for the battery, when a temperature of the battery measured by the measuring unit  110  is equal to or greater than a criterion temperature during a predetermined period. 
     Here, the predetermined period may be a minimum period in which the temperature of the battery must be maintained at the criterion temperature or above so that the change in the ohmic resistance of the battery may be related to the generation of internal gas of the battery. That is, if the temperature of the battery is maintained at the criterion temperature or above only during too short a period, the generated internal gas of the battery may not be significantly related to the change in the ohmic resistance of the battery. Therefore, in the present disclosure, by maintaining the temperature of the battery at the criterion temperature or above during a predetermined period, it is possible to make judgment by correlating the change in the ohmic resistance of the battery and the internal gas generation level of the battery. 
     For example, the criterion temperature may be set to any one of 40° C. to 60° C. Preferably, the criterion temperature may be set to 40° C. In addition, the predetermined period may be set to any one of 3 days to 8 days. Preferably, the predetermined period may be set to 3 days. 
     As a specific example, it is assumed that the criterion temperature is set to 40° C. and the predetermined period is set to 3 days. When the temperature of the battery measured by the measuring unit  110  is maintained at 40° C. or above for 3 days, the ohmic resistance determining unit  120  may determine the ohmic resistance for the corresponding battery by acquiring the impedance profile for the corresponding battery. 
     In addition, the measuring unit  110  may measure a voltage only with respect to the corresponding battery, and the control unit  130  may diagnose the internal gas generation level and the internal gas generation cause only for the corresponding battery. 
     In general, as the SOC and temperature of the battery are higher, the internal gas generation amount of the battery may be increased. That is, in order to diagnose the internal gas generation level and the internal gas generation cause for the purpose of judging whether the battery is reusable, the battery diagnosing apparatus  100  according to an embodiment of the present disclosure may perform diagnosis for a battery that is maintained at the criterion temperature or above during a predetermined period. 
     Also, preferably, the battery may be initially fully charged to the SOC 100% state. In addition, the fully charged battery may be maintained at the criterion temperature or above for a predetermined period. That is, during the predetermined period, the fully charged battery may be gradually discharged naturally, but the temperature of the battery may be configured to be maintained at the criterion temperature or above. 
     That is, the battery diagnosing apparatus  100  may judge whether the internal gas of the battery is generated, and, if generated, due to which cause the internal gas of the battery is generated, only when the fully charged battery is maintained at the criterion temperature or above for a predetermined period, in order to create a test environment in which the internal gas of the battery may be generated. 
     Hereinafter, an embodiment in which the battery diagnosing apparatus  100  diagnoses the state of the battery according to the diagnosed internal gas generation level and the internal gas generation cause of the battery will be described in detail. 
     The control unit  130  may be configured to diagnose the state of the battery based on the internal gas generation level and the internal gas generation cause. 
     Hereinafter, for convenience of explanation, the state of the battery that may be judged by the control unit  130  is divided into a normal state, a first warning state, a second warning state, or an unusable state. However, the state of the battery that may be judged by the control unit  130  may be further subdivided according to the internal gas generation level and the internal gas generation cause of the battery. For example, the control unit  130  may specifically subdivide and diagnose the internal gas generation level of the battery by comparing the calculated resistance change rate of the battery with a criterion resistance range divided into a plurality of sections. In addition, the control unit  130  may compare the calculated voltage change amount of the battery with a criterion voltage range divided into a plurality of voltage sections to subdivide and diagnose the internal gas generation cause of the battery in more detail. Also, it should be noted that the state of the battery may be specifically diagnosed in more various aspects by the internal gas generation level and the internal gas generation cause that are subdivided and diagnosed. 
       FIG.  5    is a diagram schematically showing a state of a battery diagnosed by the battery diagnosing apparatus  100  according to an embodiment of the present disclosure. 
     Referring to  FIG.  5   , the control unit  130  may be configured to diagnose that the state of the battery is a normal state, when it is judged that the internal gas less than the criterion amount is generated by another cause. 
     That is, even if a fully charged battery is placed in a situation of the criterion temperature or above for a predetermined period, if the internal gas less than the criterion amount is generated and the generated internal gas is not caused by the side reaction of the positive electrode, the control unit  130  may diagnose that the state of the battery is a normal state. In addition, the control unit  130  may classify the battery as a reusable battery. 
     In addition, referring to  FIG.  5   , the control unit  130  may be configured to diagnose that the state of the battery is a first warning state, when it is judged that the internal gas equal to or greater than the criterion amount is generated due to another cause. In addition, the control unit  130  may classify the battery as a reusable battery. 
     Thereafter, the control unit  130  may be configured to decrease an upper limit temperature of the battery in order to reduce the internal gas generation amount of the battery diagnosed as the first warning state. That is, the battery diagnosed as the first warning state may be set by the control unit  130  so that the allowable upper limit temperature is reduced. That is, when the battery diagnosed as the first warning state is reused, the allowable upper limit temperature for the battery may be limited to the temperature set by the control unit  130 . 
     In addition, referring to  FIG.  5   , the control unit  130  may be configured to diagnose that the state of the battery is a second warning state, when it is judged that the internal gas equal to or greater than the criterion amount is generated by the side reaction of the positive electrode. In addition, the control unit  130  may classify the battery as a reusable battery. 
     Thereafter, the control unit  130  may be configured to decrease at least one of an upper limit temperature and an upper limit SOC for the battery in order to decrease the internal gas generation amount of the battery diagnosed as the second warning state. That is, the battery diagnosed as the second warning state may be set by the control unit  130  such that at least one of the allowable upper limit temperature and the allowable upper limit SOC is reduced. Preferably, the control unit  130  may reduce both the upper limit temperature and the upper limit SOC of the battery in order to effectively reduce the internal gas generation amount of the battery diagnosed as the second warning state. That is, when the battery diagnosed as the second warning state is reused, at least one of the upper limit temperature and the upper limit SOC allowable for the corresponding battery may be limited to a value set by the control unit  130 . 
     Specifically, the control unit  130  may diagnose that the state of the battery having the internal gas generation level equal to or greater than the criterion amount is a warning state, and decrease the upper limit temperature and/or the upper limit SOC in order to reduce the internal gas generation amount. 
     In addition, referring to  FIG.  5   , when it is judged that the internal gas less than the criterion amount is generated by the side reaction of the positive electrode, the control unit  130  may be configured to judge that an internal short occurs in the battery and diagnose that the state of the battery is an unusable state. In addition, the control unit  130  may classify the battery as a non-reusable battery. 
     That is, when the internal gas of the battery is generated less than the criterion amount but it is judged that a side reaction of the positive electrode has occurred, the control unit  130  may judge that an internal short has occurred in the battery. In addition, the control unit  130  may diagnose that the state of the battery is an unusable state in order to prevent the battery from being reused. 
     In summary, the control unit  130  may classify a battery diagnosed as the normal state, the first warning state or the second warning state as a reusable battery, and classify a battery diagnosed as an unusable state as a non-reusable battery. In addition, the control unit  130  may reduce the internal gas generation amount of the battery when the battery is reused by appropriately restricting the operation of the battery diagnosed as the first warning state or the second warning state. 
     As such, the battery diagnosing apparatus  100  according to an embodiment of the present disclosure may diagnose the state of the battery by focusing on whether the battery is reusable based on the internal gas generation level and the internal gas generation cause of the battery. In addition, in order to reduce generation of internal gas during reuse, the operation of each battery may be limited based on the diagnosed state. Therefore, the battery diagnosing apparatus  100  has an advantage of not only judging whether to the battery is reusable, but also setting appropriate control conditions so that the battery may be used for a longer period. 
       FIG.  6    is a diagram schematically showing a battery diagnosing system  10  according to another embodiment of the present disclosure. 
     Referring to  FIG.  6   , the battery diagnosing system  10  may include a battery diagnosing apparatus  100  according to an embodiment of the present disclosure and an electrochemical impedance spectroscopy (EIS) unit  200 . 
     The EIS unit  200  may be configured to output an alternating current (AC) to the battery and generate an impedance profile representing the impedance of the battery as a corresponding relationship between the real part (Zre) and the imaginary part (-Zim) according to the output result of the AC current. 
     Specifically, the EIS unit  200  may be configured to perform EIS (Electrochemical Impedance Spectroscopy). Therefore, the EIS unit  200  may apply a minute AC current to the battery to measure the impedance of the battery, and generate an impedance profile representing the impedance as a corresponding relationship between the real part (Zre) and the imaginary part (-Zim). 
     For example, when the temperature of the battery is equal to or higher than the criterion temperature, the impedance of the battery measured by the EIS unit  200  may be inaccurate due to the influence of temperature. Therefore, the EIS unit  200  may measure the impedance of the battery when the temperature of the battery becomes close to room temperature. 
     The EIS unit  200  may be configured to output the generated impedance profile to the battery diagnosing apparatus  100 . 
     For example, the EIS unit  200  may transmit the generated impedance profile to the ohmic resistance determining unit  120  of the battery diagnosing apparatus  100 . 
     As another example, the EIS unit  200  may transmit the generated impedance profile to the storage unit  140  of the battery diagnosing apparatus  100 . In this case, the ohmic resistance determining unit  120  may access the storage unit  140  to acquire the impedance profile generated by the EIS unit  200 . 
     Also, referring to  FIG.  6   , the battery diagnosing system  10  may further include a heating unit  300 . 
     The heating unit  300  may be configured to increase the temperature of the battery so that the temperature of the battery is equal to or higher than a criterion temperature. That is, the heating unit  300  may raise and maintain the temperature of the battery so that the temperature of the battery may be maintained at the criterion temperature or above for a predetermined period. 
     Therefore, the battery diagnosing system  10  has an advantage of diagnosing whether the battery is reusable by satisfying the test conditions in which the internal gas of the battery may be generated. 
     Also, referring to  FIG.  6   , the battery diagnosing system  10  may further include a charging and discharging unit  400 . 
     The charging and discharging unit  400  may be configured to be connected to a battery to charge or discharge the battery. 
     For example, the battery may be fully charged by the charging and discharging unit  400 . In addition, the temperature of the battery may be maintained at the criterion temperature or above by the heating unit  300  for a predetermined period. In this case, the battery diagnosing apparatus  100  may diagnose the internal gas generation level, the internal gas generation cause and the state of the battery. 
     On the other hand, when the cause of the internal gas generation of the battery is diagnosed as another cause other than the side reaction of the positive electrode, the battery diagnosing system  10  may perform additional diagnosis in order to specifically diagnose the internal gas generation cause of the battery. 
     The charging and discharging unit  400  may be configured to fully discharge the battery after fully charging the battery again. 
     For example, a battery maintained at a temperature equal to or greater than the criterion temperature for a predetermined period may be discharged naturally to reduce its capacity. Therefore, the charging and discharging unit  400  may fully charge the battery again at a first time point after a predetermined period has elapsed. That is, the SOC of the battery at the first time point may be 100%. In addition, at the second time point later than the first time point, the charging and discharging unit  400  may fully discharge the battery. That is, the SOC of the battery at the second time point may be 0%. The measuring unit  110  may measure the discharge capacity of the battery from the first time point to the second time point. 
     The control unit  130  may calculate a capacity change rate by comparing the discharge capacity of the battery calculated by the measuring unit  110  with a criterion capacity. Here, the criterion capacity may be a discharge capacity of the battery in the BOL state. That is, the criterion capacity may be a discharge capacity when the battery in the BOL state is discharged from 100% SOC to 0% SOC. 
     Specifically, the control unit  130  may calculate a capacity change rate by calculating a difference between the calculated discharge capacity and the criterion capacity. For example, the control unit  130  may calculate the capacity change rate of the battery by calculating the formula “(criterion capacity−calculated discharge capacity)÷criterion capacity×100”. 
     In addition, if the calculated capacity change rate is greater than or equal to the criterion capacity change rate, the control unit  130  may be configured to judge that the internal gas generation cause of the battery is a side reaction of the negative electrode. 
     In addition, the control unit  130  may be configured to diagnose that the state of the battery is a third warning state, when it is judged that the internal gas of the battery equal to or greater than the criterion amount is generated by the side reaction of the negative electrode. In addition, the control unit  130  may classify the battery as a reusable battery. 
     Thereafter, the control unit  130  may be configured to reduce at least one of the upper limit temperature and the upper limit C-rate for the battery in order to reduce the internal gas generation amount of the battery diagnosed as the third warning state. That is, the battery diagnosed as the third warning state may be set by the control unit  130  such that at least one of the allowable upper limit temperature and the upper limit C-rate is reduced. That is, when a battery diagnosed as the third warning state is reused, the allowable upper limit temperature and/or the upper limit C-rate for the battery may be limited to a value set by the control unit  130 . 
     The battery diagnosing apparatus  100  according to the present disclosure may be applied to a BMS (Battery Management System). That is, the BMS according to the present disclosure may include the battery diagnosing apparatus  100  described above. In this configuration, at least some components of the battery diagnosing apparatus  100  may be implemented by supplementing or adding functions of the configuration included in the conventional BMS. 
     In addition, the battery diagnosing apparatus  100  according to the present disclosure may be provided to a battery pack. That is, the battery pack according to the present disclosure may include the above-described battery diagnosing apparatus  100  and at least one battery. In addition, the battery pack may further include electrical equipment (a relay, a fuse, etc.) and a case. 
       FIG.  7    is a diagram schematically showing an exemplary configuration of a battery pack  1  according to still another embodiment of the present disclosure. Referring to  FIG.  7   , the battery pack  1  may include a battery diagnosing apparatus  100 , an EIS unit  200 , a heating unit  300 , and a charging and discharging unit  400 . That is, the battery pack  1  may include the battery diagnosing system  10 . 
     For example, in the embodiment of  FIG.  7   , the battery diagnosing apparatus  100  may be connected to first to fourth sensing lines SL 1  to SL 4 . Preferably, the first to fourth sensing lines SL 1  to SL 4  may be connected to the measuring unit  110  of the battery diagnosing apparatus  100 . 
     The measuring unit  110  may measure the temperature of the battery B through the first sensing line SL 1 . 
     In addition, the measuring unit  110  may measure a positive electrode voltage of the battery B through the second sensing line SL 2  and measure a negative electrode voltage of the battery B through the third sensing line SL 3 . In addition, the measuring unit  110  may measure the voltage of the battery B by calculating a difference between the measured positive electrode voltage and negative electrode voltage of the battery B. 
     Also, the measuring unit  110  may be connected to a current measuring element A through the fourth sensing line SL 4 . Here, the current measuring element A may be a current system or a shunt resistor. Therefore, the measuring unit  110  may measure the current of the battery B through the fourth sensing line SL 4 .  FIG.  7    shows an embodiment in which the current measuring element A is provided between a negative electrode of the battery B and a negative electrode terminal P− of the battery pack  1  as a preferred embodiment, but the current measuring element A may also be provided between a positive electrode of the battery B and a positive electrode terminal P+ of the battery pack  1 . 
     One end of the EIS unit  200  may be connected between the positive electrode terminal P+ of the battery pack  1  and the positive electrode of the battery B, and the other end may be connected between the negative electrode terminal P− of the battery pack  1  and the negative electrode of the battery B. In addition, the EIS unit  200  may measure the impedance of the battery B after outputting a minute AC current. Thereafter, the EIS unit  200  may generate an impedance profile of the battery B and transmit it to the battery diagnosing apparatus  100 . 
     One end of the heating unit  300  may be connected to the positive electrode of the battery B, and the other end may be connected to the negative electrode of the battery cell B. In addition, the operation of the heating unit  300  is controlled by the battery diagnosing apparatus  100  (particularly, the control unit  130 ), and when the heating unit  300  is operated, the temperature of the battery B may increase. 
     One end of the charging and discharging unit  400  may be connected to the positive electrode terminal P+ of the battery pack  1 , and the other end may be connected to the negative electrode terminal P− of the battery pack  1 . In another embodiment, one end of the charging and discharging unit  400  may be directly connected to the positive electrode of the battery B, and the other end may be directly connected to the negative electrode of the battery B, similarly to the heating unit  300 . The operation of the charging and discharging unit  400  may be controlled by the battery diagnosing apparatus  100  (particularly, the control unit  130 ), and when the charging and discharging unit  400  is operated, the battery B may be charged or discharged. 
     For example, the battery B may be fully charged by the charging and discharging unit  400 . In addition, by the heating unit  300 , the temperature of the battery B may be maintained at the criterion temperature or above for a predetermined period. Thereafter, the internal gas generation level, the internal gas generation cause and the state of the battery B may be diagnosed by the battery diagnosing apparatus  100 . 
       FIG.  8    is a diagram showing a battery diagnosing method according to still another embodiment of the present disclosure. 
     Here, each step of the battery diagnosing method may be performed by the battery diagnosing apparatus  100 . Hereinafter, for convenience of explanation, content overlapping with the previously described content will be briefly described or omitted. 
     Referring to  FIG.  8   , the battery diagnosing method according to an embodiment of the present disclosure may include a measuring step (S 100 ), an ohmic resistance determining step (S 200 ), a voltage change amount calculating step (S 300 ), a resistance change rate calculating step (S 400 ), an internal gas generation level judging step (S 500 ), and an internal gas generation cause judging step (S 600 ). 
     The measuring step (S 100 ) is a step of measuring the voltage and temperature of the battery, and may be performed by the measuring unit  110 . 
     For example, referring to  FIGS.  1  and  7   , the measuring unit  110  may be connected to a battery through first to third sensing lines SL 1  to SL 3 . In addition, the measuring unit  110  may measure the temperature of the battery through the first sensing line SL 1 , and measure the voltage of the battery through the second and third sensing lines SL 2 , SL 3 . 
     The ohmic resistance determining step (S 200 ) is a step of determining the ohmic resistance of the battery based on the impedance profile generated for the battery, and may be performed by the ohmic resistance determining unit  120 . 
     For example, the ohmic resistance determining unit  120  may directly receive the impedance profile generated for the battery from the outside, or may access the storage unit  140  to obtain the impedance profile stored in the storage unit  140 . In addition, the ohmic resistance determining unit  120  may determine the ohmic resistance of the battery from the impedance profile. 
     Preferably, the ohmic resistance determining unit  120  may determine the ohmic resistance only for a battery in which the temperature of the battery measured by the measuring unit  110  is equal to or greater than the criterion temperature and this state is maintained for a predetermined period. 
     The voltage change amount calculating step (S 300 ) is a step of calculating a voltage change amount by comparing the voltage of the battery measured in the measuring step (S 100 ) with a reference voltage, and may be performed by the control unit  130 . 
     For example, the control unit  130  may calculate the voltage change amount of the battery by calculating the formula “reference voltage−measured voltage of the battery”. 
     The resistance change rate calculating step (S 400 ) is a step of calculating a resistance change rate by comparing the ohmic resistance determined in the ohmic resistance determining step (S 200 ) with a reference resistance, and may be performed by the control unit  130 . 
     For example, the control unit  130  may calculate the resistance change rate of the battery by calculating the formula “(determined ohmic resistance−reference resistance)÷reference resistance×100”. 
     The internal gas generation level judging step (S 500 ) is a step of judging an internal gas generation level of the battery by comparing magnitudes of the calculated resistance change rate and a criterion resistance change rate, and may be performed by the control unit  130 . 
     For example, if the calculated resistance change rate is greater than or equal to the criterion resistance change rate, the control unit  130  may judge that the internal gas of the battery equal to or greater than the criterion amount is generated. Conversely, if the calculated resistance change rate is less than the criterion resistance change rate, the control unit  130  may judge that the internal gas of the battery less than the criterion amount is generated. 
     The internal gas generation cause judging step (S 600 ) is a step of judging the internal gas generation cause of the battery by comparing the magnitudes of the calculated voltage change amount and the criterion voltage change amount, and may be performed by the control unit  130 . 
     For example, if the calculated voltage change amount is greater than or equal to the criterion voltage change amount, the control unit  130  may judge that the internal gas of the battery is generated by a side reaction of the positive electrode of the battery. Conversely, if the calculated voltage change amount is less than the criterion voltage change amount, the control unit  130  may judge that the internal gas of the battery is caused by another cause other than the side reaction of the positive electrode of the battery. 
     Furthermore, although not shown in  FIG.  8   , the battery diagnosing method may further include a battery state diagnosing step after the internal gas generation cause judging step (S 600 ). 
     The battery state diagnosing step is a step of diagnosing the state of the battery based on the internal gas generation level and the internal gas generation cause, and may be performed by the control unit  130 . 
     Referring to  FIG.  5   , the control unit  130  may diagnose the state of the battery as a normal state, a first warning state, a second warning state, or an unusable state based on the internal gas generation level and the internal gas generation cause. 
     For example, the control unit  130  may classify a battery diagnosed as the normal state, the first warning state or the second warning state as a reusable battery, and classify a battery diagnosed as an unusable state as a non-reusable battery. In addition, the control unit  130  may reduce the internal gas generation amount of the battery when the battery is reused by appropriately restricting the operation of the battery diagnosed as the first warning state or the second warning state. 
     In addition, after the battery state diagnosing step, only when the battery is judged as the first warning state, an additional diagnosing step may be performed to more specifically confirm the internal gas generation cause of the battery. 
     The additional diagnosing step is a step of diagnosing whether the internal gas generation cause of the battery is the side reaction of the negative electrode, and may be performed by the control unit  130 . 
     The embodiments of the present disclosure described above may not be implemented only through an apparatus and a method, but may be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present disclosure or a recording medium on which the program is recorded. The program or recording medium may be easily implemented by those skilled in the art from the above description of the embodiments. 
     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 disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
     Additionally, many substitutions, modifications and changes may be made to the present disclosure described hereinabove by those skilled in the art without departing from the technical aspects of the present disclosure, and the present disclosure is not limited to the above-described embodiments and the accompanying drawings, and each embodiment may be selectively combined in part or in whole to allow various modifications. 
     REFERENCE SIGNS 
     
         
         
           
               1 : battery pack 
               10 : battery diagnosing system 
               100 : battery diagnosing apparatus 
               110 : measuring unit 
               120 : ohmic resistance determining unit 
               130 : control unit 
               140 : storage unit 
               200 : EIS unit 
               300 : heating unit 
               400 : charging and discharging unit