Secondary battery state determining method, secondary battery state determining device, and secondary battery

Abstract

An objective of the present invention is to provide a secondary battery state determining method, a secondary battery state determining device and a secondary battery, with which it is possible to analyze the state of an electrode inside the battery and determine whether an unresolvable distribution such as a deterioration distribution has formed on the electrode, or whether a resolvable distribution such as an SOC distribution has formed on the electrode.　A secondary battery state determining method according to the present invention is for determining the internal state of a secondary battery, and is characterized by including: a calculation step for calculating a relaxation spectrum in a two-axis coordinate system in which one axis is relaxation time and the other axis is intensity; a processing step for refreshing non-uniformity of the internal state for the secondary battery; and a comparison step for comparing shape information of the relaxation spectrum before and after application of the refresh processing.

Description

Method for determining state of secondary battery, state determination device for secondary battery, and secondary battery

[0001] The present invention relates to a method for determining the state of a secondary battery, a state determination device for a secondary battery, and a secondary battery.

[0002] Lithium-ion secondary batteries (hereinafter referred to as secondary batteries) are expected to be applied to a variety of product groups ranging from electric mobility applications such as electric vehicles to stationary power sources, and their demand is steadily increasing. Generally, it is known that the life of a secondary battery is closely related to its usage conditions, and if a secondary battery is continuously used under high-load conditions such as a large current, the battery performance will rapidly deteriorate. Therefore, in order to stably use a secondary battery until the end of its product life, it is important to appropriately determine the deterioration state of the secondary battery.

[0003] In recent years, attempts have also been made to reuse used batteries that have reached the end of their life in electric vehicles as stationary power sources. In order to ensure the reliability and safety of reuse, a method for determining the risk of rapid performance deterioration in used batteries is required.

[0004] Examples of deterioration events that cause rapid performance deterioration of a secondary battery include a phenomenon in which the electrodes inside the battery deteriorate unevenly (hereinafter referred to as uneven deterioration). It is known that when uneven deterioration progresses, the capacity and resistance of the secondary battery rapidly deteriorate, and ultimately lead to malfunction or failure of the secondary battery product.

[0005] In FIG. 1, the process in which uneven deterioration occurs and the state in which uneven deterioration progresses inside the battery are shown schematically. When a secondary battery is used under high load, a temperature distribution is formed inside the battery due to the difference in heat dissipation rate between the central part and the end part of the electrode, and the reaction rate on the electrode changes due to the generated temperature distribution, forming a distribution of the state of charge (hereinafter referred to as SOC) on the electrode.

[0006] While these temperature and SOC distributions can be resolved by applying appropriate thermal and electrical treatments to the secondary battery, if the secondary battery is used without resolving these distributions, a degradation distribution (non-uniform degradation) will form inside the battery according to the temperature and SOC distribution. The reason for this degradation distribution is that the degradation of the secondary battery depends on temperature and SOC. If the secondary battery continues to be used in a state of non-uniform degradation, the degradation in locally degraded areas will progress further, ultimately leading to a rapid decrease in secondary battery capacity or failure or malfunction of the battery product.

[0007] A characteristic of non-uniform degradation is that the initial symptoms of degradation include the appearance of SOC (State of Charge) distributions on the electrodes. At this stage, the distribution can be eliminated through electrical treatment, thereby preventing the occurrence of non-uniform degradation. On the other hand, once the SOC distribution progresses to a degradation distribution, it becomes difficult to eliminate the distribution, and it becomes necessary to reconsider high-load operation, such as reducing the current value when using secondary batteries.

[0008] From the above, it can be seen that there are two main ways to prevent defects and failures in battery products caused by uneven degradation. One is to detect the occurrence of uneven degradation early and prevent its progression by replacing the battery or reducing the current load during use. This method cannot prevent the occurrence of uneven degradation itself, but it can slow down the progression of degradation, so it can be expected to extend the battery life.

[0009] Another method involves detecting and eliminating the formation of temperature and SOC distributions within the battery, thereby preventing the occurrence of non-uniform degradation. This method fundamentally eliminates the risk of battery product defects and failures caused by non-uniform degradation, and is expected to improve product safety and reliability in addition to extending battery life.

[0010] To achieve early detection and prevention of non-uniform degradation, a method for accurately detecting the degradation state inside a battery is required. For example, Patent Document 1 describes a method for accurately evaluating the non-uniformity (uneven degradation) of the degradation state formed within the electrodes of a secondary battery.

[0011] Japanese Patent Publication No. 2022-185511

[0012] As mentioned above, in order to suppress the progression of non-uniform degradation and extend the lifespan of batteries, it is necessary to change the treatment applied to the battery product depending on whether an unresolved distribution such as non-uniform degradation occurs or a resolvable distribution such as SOC distribution occurs. For example, if an unresolvable distribution occurs, battery replacement or a change in operating method will be necessary. On the other hand, if a resolvable distribution occurs, the battery can be used continuously with the same operating method as before by applying a treatment to eliminate that distribution.

[0013] The method described in Patent Document 1 can determine whether or not the electrode state inside the battery is non-uniform, and is therefore considered effective for detecting the distribution of degradation (non-uniform degradation) and the SOC distribution that occur inside the battery. On the other hand, it is difficult to identify the cause of the non-uniform electrode state using this method alone, and it is not possible to distinguish whether the cause of the non-uniformity is due to the formation of an irresolvable distribution, such as the degradation distribution, or to the formation of an irresolvable distribution, such as the SOC distribution. For this reason, it is difficult to appropriately apply measures that are effective in suppressing the progression of non-uniform degradation to battery products using the method described in Patent Document 1.

[0014] The object of the present invention is to provide a method for determining the state of a secondary battery, a device for determining the state of a secondary battery, and a secondary battery that can analyze the electrode state inside the battery and determine whether an irresolvable distribution such as a degradation distribution is formed on the electrodes, or whether an irresolvable distribution such as a state of charge (SOC) distribution is formed.

[0015] The present invention provides a method for determining the state of a secondary battery, which is a method for determining the internal state of a secondary battery, and is characterized by including a calculation step of calculating a relaxation spectrum in a biaxial coordinate system in which one axis represents relaxation time and the other axis represents intensity; a processing step of refreshing the non-uniformity of the internal state of the secondary battery; and a comparison step of comparing the shape information of the relaxation spectrum before and after applying the refresh processing.

[0016] Alternatively, the secondary battery state determination device of the present invention is a secondary battery state determination device for determining the internal state of a secondary battery, and is characterized by comprising: a calculation unit that calculates a relaxation spectrum in a biaxial coordinate system in which one axis is the relaxation time and the other axis is the intensity; a processing unit that applies a process to refresh the non-uniformity of the internal state of the secondary battery; and a comparison unit that compares the shape information of the relaxation spectrum before and after the application of the refresh process.

[0017] Alternatively, the present invention relates to a secondary battery having a state determination device for determining the internal state of the secondary battery, wherein the state determination device comprises a calculation unit for calculating a relaxation spectrum in a biaxial coordinate system where one axis represents relaxation time and the other axis represents intensity, a processing unit for applying a process to refresh the non-uniformity of the internal state of the secondary battery, and a comparison unit for comparing the shape information of the relaxation spectrum before and after the application of the refresh process.

[0018] According to the present invention, it is possible to provide a method for determining the state of a secondary battery, a device for determining the state of a secondary battery, and a secondary battery that can analyze the electrode state inside the battery and determine whether an irresolvable distribution such as a degradation distribution is formed on the electrodes or an irresolvable distribution such as a state of charge (SOC) distribution is formed.

[0019] This is a conceptual diagram illustrating the process of non-uniform degradation and the conditions under which non-uniform degradation progresses. This is a block diagram of the secondary battery state determination system in this embodiment. This is a diagram showing the shape information of the relaxation spectrum. This is a diagram showing the relaxation spectrum before and after the electrode state becomes non-uniform. This is a diagram showing the processing flow in the state determination system shown in Figure 2.

[0020] The following describes embodiments (examples) for carrying out the present invention with reference to the drawings. Within the description of the following embodiments, other embodiments applicable to the embodiments will also be described as appropriate. The present invention is not limited to the following embodiments, and different embodiments can be combined or modified as needed without significantly impairing the effects of the present invention. Furthermore, the same reference numerals will be used for the same components, and redundant explanations will be omitted. Additionally, components with the same function will be given the same name. The illustrations are purely schematic, and for illustrative purposes, the actual configuration may be modified or some components may be omitted or modified between drawings without significantly impairing the effects of the present invention. Also, the same embodiment does not necessarily need to include all components.

[0021] Figure 2 is a block diagram of the secondary battery state determination system in this embodiment. Hereinafter, this state determination system 100 (state determination device), the secondary battery 210, and its control device 220 will be collectively referred to as the battery system 300. Therefore, the battery system 300 comprises the state determination system 100, the secondary battery 210, and its control device 220.

[0022] The state determination system 100 determines the electrode state inside the secondary battery 210, and if the electrode state is non-uniform, it determines whether the cause is due to an unresolved factor or a resolvable factor. Unresolved factors include, for example, events that cause the degradation state of the electrodes to become non-uniform, such as degradation distribution (non-uniform degradation), and resolvable factors include, for example, events that cause the charge state of the electrodes to become non-uniform, such as SOC distribution. However, the method of this embodiment is not necessarily limited to these events.

[0023] The state determination system 100 comprises a measurement unit 11, a calculation unit 12, a recording unit 13, a processing unit 14, a comparison unit 15, a determination unit 16, a display unit 17 which is a presentation unit, and a control unit 18. These may all be configured as a single unit, or at least some may be configured separately. When all of these are configured as a single unit, the state determination system 100 can be called a determination device. On the other hand, when at least some are configured separately, for example, that part may be stored on a server located in a remote location via a network. In this embodiment, the control device 220 of the secondary battery 210 and the control unit 18 of the state determination system 100 are described as being configured separately, but they may be integrated.

[0024] The measurement unit 11 measures at least one of the time-series data of DC current value and DC voltage value during charging or discharging of the secondary battery 210. The measurement timing is performed during use, including during charging or discharging of the secondary battery 210, or during standby when charging or discharging is not performed. In addition, the time-series data measured at this time may also include time-series data of the temperature of the secondary battery 210.

[0025] The measurement unit 11 extracts time-series data from the measured time-series data during a period (timing) in which the relaxation spectrum can be calculated. The relaxation spectrum is a continuous function of relaxation time, and is a spectrum (hereinafter referred to as the relaxation spectrum) in a biaxial coordinate system where one axis (e.g., the horizontal axis) is relaxation time and the other axis (e.g., the vertical axis) is intensity (spectral intensity). For example, it is preferable to extract time-series data for at least one period, such as during constant voltage charging, after charging, or after discharge. After charging, it may be after constant voltage charging or after constant current charging. After discharge, it may be after constant voltage discharge or after constant current discharge.

[0026] When extracting time-series data during constant-voltage charging, the measurement unit 11 extracts time-series data of the voltage, current, and temperature of the secondary battery 210 from the time t1 when constant-voltage charging starts until the time t2 when constant-voltage charging ends. Constant-voltage charging is a charging method in which the secondary battery 210 is charged while maintaining a constant voltage value. Furthermore, the measurement unit 11 also extracts the voltage value of the secondary battery 210 before (preferably immediately before) the start of charging. There is no limit to the time from time t1 to time t2, but it is preferably 1 minute or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less.

[0027] When extracting time-series data after charging (after charging is complete) or after discharging (after discharging is complete), the measurement unit 11 extracts time-series data of the voltage, current, and temperature of the secondary battery 210 from the end time of charging or discharging t3 to a predetermined time t4. Furthermore, the measurement unit 11 also acquires the current value immediately before the end of charging or discharging of the secondary battery 210. There is no limit to the time from time t3 to time t4, but it is preferably 1 minute or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less.

[0028] There are no restrictions on how the measurement unit 11 acquires measurement data (including the above-mentioned time-series data, voltage value before charging starts, current value immediately before charging / discharging, etc.) from the secondary battery 210. For example, the measurement unit 11 can measure data related to the secondary battery 210 (e.g., measurement data) at a location different from where the secondary battery 210 is installed. This allows, for example, when the secondary battery 210 is installed in a vehicle, ship, aircraft, etc., the measurement data of the secondary battery 210 to be centrally managed on a server located remotely. This improves convenience.

[0029] Specifically, for example, the measurement unit 11 may acquire measurement data from the secondary battery 210 via an electrical circuit, a communication circuit such as a wired LAN, or from a secondary battery 210 located in a remote location via a network such as a wireless LAN, or it may acquire measurement data using a combination of these methods. Furthermore, in the process of the measurement unit 11 acquiring measurement data from the secondary battery 210, it may acquire the measurement data via some other device. For example, the measurement unit 11 may acquire measurement data from the secondary battery 210 via an external device (not shown), such as a charge / discharge device. Alternatively, the measurement unit 11 may store the measurement data acquired from the secondary battery 210 on a server and then retrieve that measurement data.

[0030] Next, the calculation unit 12 calculates the relaxation spectrum from the measurement data of the measurement unit 11. The specific method for calculating the relaxation spectrum is as follows, but the calculation method is not limited to the following example.

[0031] <Calculation Method 1: Calculating the relaxation spectrum from measurement data during constant voltage charging> In this case, the relaxation spectrum ρ(τ) can be calculated using the measurement data from (Equation 1).

[0032]

[0033] ρ(τ) represents the relaxation spectrum, ΔV is the difference between the battery voltage value before charging starts (preferably immediately before) and the voltage value during constant voltage charging, and I(t) represents the time series data of the current value during constant voltage charging. Also, the symbol L －１ This shows the inverse Laplace transform for I(t) / ΔV.

[0034] <Calculation Method 2: Calculating the relaxation spectrum from measurement data after charging or discharging> In this case, the relaxation spectrum ρ(τ) can be calculated using the measurement data from (Equation 2).

[0035]

[0036] ρ(τ) shows the relaxation spectrum, I ０ V(t) represents the current value immediately before the end of charging or discharging, and V(t) represents the time-series data of the voltage value after charging or discharging. Also, the symbol L －１ is V(t) / I ０We show the inverse Laplace transform for .

[0037] The recording unit 13 stores the relaxation spectrum calculated by the calculation unit 12. Figure 3 shows the relaxation spectrum calculated using (Equation 1).

[0038] The processing unit 14 applies a charge / discharge process (hereinafter referred to as a refresh process) to the secondary battery 210 that is effective in eliminating the SOC distribution formed on the electrodes. Examples of refresh processes include a charge refresh process that fully charges, intermittently charges, or charges the secondary battery 210 at a constant voltage, and a discharge refresh process that completely discharges, intermittently discharges, or discharges the secondary battery 210 at a constant voltage. Here, full charge (complete discharge) refers to a process of charging (discharging) the secondary battery 210 until its charge rate reaches 100% (0%), or a process of charging (discharging) the secondary battery 210 until its voltage reaches a voltage value corresponding to a charge rate of 100% (0%). In other words, by performing a process that includes at least one of full charge, intermittent charge, constant voltage charge, complete discharge, intermittent discharge, and constant voltage discharge in the processing unit 14, it is possible to eliminate the SOC distribution.

[0039] Furthermore, intermittent charging (intermittent discharging) refers to a process in which the battery is charged (discharged) while repeatedly charging (discharging) for short periods and pausing until a predetermined charge level is reached, while constant voltage charging (constant voltage discharging) refers to a process in which the secondary battery 210 is charged (discharged) while maintaining its voltage at a predetermined voltage.

[0040] The processing unit 14 applies at least one of the aforementioned charge refresh process or discharge refresh process to the secondary battery 210. It is preferable that the charge refresh process or discharge refresh process be applied to the secondary battery 210 multiple times, but since the processing time required for the processing unit 14 increases with the number of applications, it is sufficient to apply it to the secondary battery 210 at least once.

[0041] Furthermore, when applying the charge refresh process or discharge refresh process multiple times, it is preferable to alternate between the charge refresh process and the discharge refresh process. For example, the refresh process can be efficiently performed by alternately performing full charge and complete discharge.

[0042] In addition to the refresh process by charge and discharge, the processing unit 14 may also apply a refresh process by controlling the temperature of the secondary battery 210. The refresh process by temperature control refers to a process of allowing the secondary battery 210 to stand in a constant temperature environment to equalize the temperature inside the secondary battery 210. During this period, it is preferable not to perform any charge or discharge process on the secondary battery, and it is preferable to provide such a standing time of at least one hour or more.

[0043] Before and after applying the refresh process of the processing unit 14, the measurement unit 11 measures the charge and discharge data of the secondary battery 210 respectively, the calculation unit 12 calculates the relaxation spectrum from each charge and discharge data, and the calculation result needs to be recorded in the recording unit 13. The processing flow of such a state determination system 100 will be described later.

[0044] The comparison unit 15 acquires the relaxation spectra at the time points before and after applying the refresh process from the recording unit 13, and compares the shape information of the relaxation spectra before and after the refresh process. Examples of the shape information of the relaxation spectrum used for comparison include, for example, the total area of the relaxation spectrum, the number of peaks, the peak area, the peak position, the peak half-width, etc. That is, by including at least one of the number of peaks, the position of the peaks, the area of the peaks, the peak half-width, and the skewness of the peaks in the relaxation spectrum, necessary and appropriate comparison can be made.

[0045] Fig. 3 shows the relationship between the peak areas (S1, S2), the peak positions (τ1, τ2), and the half-widths (w1, w2) as the shape information of the relaxation spectrum. Regarding the method of comparing the areas, the area may be compared for each peak of the relaxation spectrum, the sum of each peak area may be compared, or the difference in the areas of the two relaxation spectra may be evaluated using the following formula.

[0046]

[0047] Here, ρ(τ) and ρ’(τ) represent the relaxation spectra before and after the refresh process respectively, and X represents the difference in the areas of these relaxation spectra.

[0048] The determination unit 16 first determines whether the electrode state of the secondary battery 210 is non-uniform, and if it is, it determines whether the cause is an irresolvable one resulting from the occurrence of non-uniform degradation, or an irresolvable one resulting from the formation of an SOC distribution, etc.

[0049] To determine whether the electrode state is non-uniform, the determination unit 16 uses information obtained by comparing, for example, the relaxation spectrum acquired before the refresh process was applied with the relaxation spectrum acquired when the secondary battery 210 was new. If the difference in shape information between these relaxation spectra is greater than a pre-set threshold, it is determined that the electrode state is non-uniform. Examples of pre-set thresholds include "a change of one or more peaks in the relaxation spectrum", "a change of X% or more in the area of ​​the relaxation spectrum", and "a change of Y% or more in the peak position of the relaxation spectrum".

[0050] Figure 4 shows the relaxation spectra before and after the electrode state becomes non-uniform. This shows a comparison of the relaxation spectra of a lithium-ion secondary battery composed of a lithium iron phosphate positive electrode and a graphite negative electrode. The dark solid line shows the relaxation spectrum when the battery is new (uniform), and the light solid line shows the relaxation spectrum measured when the electrode state becomes non-uniform (battery degradation). From the figure, it can be seen that the number of peaks in the relaxation spectrum increases from two to three during degradation, suggesting that the electrode state has become non-uniform.

[0051] If it is determined that the electrode state is non-uniform, the determination unit 16 refers to the comparison unit 15 and checks the amount of change in the shape information of the relaxation spectrum before and after the refresh process. If the amount of change before and after the refresh process is greater than a pre-set threshold, it is considered that the relaxation spectrum has changed significantly due to the refresh process, and the non-uniform state formed on the electrode is determined to be resolvable, like the SOC distribution. Conversely, if no significant difference is confirmed in the shape information of the relaxation spectrum before and after the refresh process, it is determined that the non-uniform state formed on the electrode is irresolvable, like non-uniform degradation.

[0052] The threshold value in the determination unit 16 may be changed during the operation of the secondary battery 210. For example, the threshold value may be temporarily set at the time of factory shipment of the product equipped with the secondary battery 210, and after investigating the operating status of the product after shipment, the temporarily set threshold value may be changed at a time such as during maintenance.

[0053] The display unit 17 displays whether the electrode state of the secondary battery 210 is non-uniform, and if so, whether it can be resolved, based on the determination result of the determination unit 16. If it is determined that the electrode state is non-uniform, the severity of the non-uniformity may also be displayed as a barometer. For example, when determining the non-uniformity of the electrode state using the difference in the area of ​​the relaxation spectrum (see Equation 3), the display unit 17 may display the severity as low if the difference in area is less than or equal to threshold A, medium if it is between threshold A and B, and high if it is between threshold B and C (however, A < B < C).

[0054] As described above, the battery includes a calculation unit 12 that calculates a relaxation spectrum in a biaxial coordinate system with one axis representing relaxation time and the other axis representing intensity, a processing unit 14 that applies a process to refresh the non-uniformity of the internal state of the secondary battery, and a comparison unit 15 that compares the shape information of the relaxation spectrum before and after the refresh process. This makes it possible to analyze the electrode state inside the battery and determine whether an irresolvable distribution, such as a degradation distribution, is formed on the electrodes, or whether an irresolvable distribution, such as a state-of-charge (SOC) distribution, is formed. Furthermore, by including a determination unit 16 that determines whether the non-uniformity of the electrode state is due to the formation of a charge rate distribution and is therefore resolvable, appropriate refresh processing can be performed.

[0055] The method of metering according to the present invention is not necessarily limited to the method described above. Severity may also be quantified as a percentage, or displayed using color information such as a color bar.

[0056] The display unit converts the comparison results of shape information into at least one of numerical information, color information, sound information, and string characters, and displays the progress of the non-uniformity of the electrode state of the secondary battery, thereby allowing the user to understand the state of the secondary battery. For example, in the display unit 17, which is an example of the display unit, the comparison results of shape information are converted into at least one of numerical information, color information, and string characters, and the progress of the non-uniformity of the electrode state of the secondary battery is displayed, allowing the user to understand the state of the secondary battery.

[0057] The control unit 18 changes the operation method and control method of the secondary battery 210 based on the determination result of the determination unit 16. The following shows the determination result of the determination unit 16 and an example of how the operation method and control method of the secondary battery 210 are changed based on it.

[0058] If it is determined that the electrode state is not non-uniform, no changes will be made to the operation method of the secondary battery 210.

[0059] Furthermore, if it is determined that the electrode state has become non-uniform and that this non-uniformity can be resolved, an additional refresh process is performed on the secondary battery 210. In addition, it is checked whether the shape information of the relaxation spectrum has changed before and after the additional refresh process, and if a change is observed in the shape information, the refresh process is performed again. This operation is repeated until the shape information of the relaxation spectrum no longer changes before and after the refresh process, thereby completely eliminating any resolvable distributions such as the SOC distribution.

[0060] Next, if it is determined that the electrode state has become non-uniform and that this non-uniformity cannot be resolved, the current load when operating the secondary battery 210 is reduced, or the secondary battery 210 is replaced with a new battery.

[0061] Figure 5 shows the processing flow of the state determination system 100. In the state determination system 100, at the timing of determining the state of the secondary battery, charge and discharge data necessary for calculating the relaxation spectrum is acquired in the measurement step S11. Then, the relaxation spectrum is calculated from the acquired charge and discharge data in the calculation step S12. In other words, in the calculation step S12, the relaxation spectrum in a biaxial coordinate system, where one axis is relaxation time and the other axis is intensity, is calculated. The calculation result is then saved in the recording step S13.

[0062] Next, in processing step S14, a refresh process is applied to the secondary battery 210. In other words, in processing step S14, the non-uniformity of the internal state of the secondary battery is refreshed. After the refresh process is completed, charge and discharge data of the secondary battery 210 is acquired again in metering step S11-2, and the relaxation spectrum is calculated using this data in calculation step S12-2.

[0063] Subsequently, the calculation results are saved in recording step S13-2, and the relaxation spectra before and after the refresh process, saved in recording steps S13 and S13-2, are compared in comparison step S15. In other words, in comparison step S15, the shape information of the relaxation spectra before and after the refresh process is compared. A necessary and appropriate comparison can be made by using at least one of the following in the relaxation spectrum: the number of peaks, the position of the peaks, the area of ​​the peaks, the full width at half maximum of the peaks, and the skewness of the peaks.

[0064] Based on the comparison, in the determination step S16, if there is a significant difference in the shape information of the relaxation spectrum before and after the refresh process, it is determined that the non-uniformity of the electrode state can be resolved; if there is no significant difference, it is determined that it cannot be resolved. The determination result is then displayed in the display step S17. If the electrode state is not non-uniform, these processes are terminated. If the electrode state is non-uniform, the process proceeds to the control step S18 based on the determination result. This information may also be displayed in the display step S17. Furthermore, in the display step S17, the comparison result of the shape information is converted into at least one of numerical information, color information, and strings, and the progress of the non-uniformity of the electrode state of the secondary battery is displayed, allowing the state of the secondary battery to be understood.

[0065] Thus, by including a calculation step of calculating a relaxation spectrum in a biaxial coordinate system where one axis represents relaxation time and the other axis represents intensity, a processing step of refreshing the non-uniformity of the internal state of the secondary battery, and a comparison step of comparing the shape information of the relaxation spectrum before and after the refresh process, it becomes possible to analyze the electrode state inside the battery and determine whether an irresolvable distribution such as a degradation distribution is formed on the electrodes, or whether an irresolvable distribution such as a state-of-coolation (SOC) distribution is formed. Furthermore, based on the comparison results of the shape information, it is determined whether or not additional refresh processing is necessary for the secondary battery. This determination makes it possible to further improve the SOC distribution.

[0066] In control step S18, if the non-uniformity can be eliminated, an additional refresh process is applied to the secondary battery 210 to completely eliminate the SOC distribution and other issues. If the non-uniformity cannot be eliminated, a decision is made regarding whether to change the operation method of the secondary battery 210 or replace the secondary battery, and a suggestion is made.

[0067] The secondary battery 210 to which this embodiment can be applied includes any form such as a secondary battery cell, secondary battery module, secondary battery pack, or secondary battery system. Furthermore, the secondary battery 210 to which this embodiment can be applied may be installed in electric mobility such as ships, aircraft, or vehicles (battery-powered trains, electric vehicles, etc.), or it may be installed in a stationary battery storage system, and its use may be changed during use. For example, it can also be applied when a secondary battery 210 used in electric mobility is reused as a stationary battery storage system.

[0068] Furthermore, this embodiment can be applied regardless of the degradation state of the secondary battery 210. For example, the secondary battery 210 may be a new battery (in an undegraded state), or it may be a battery that has become degraded (e.g., used, secondhand) due to use in some application. Alternatively, it may be a secondary battery 210 that has deteriorated over time as a result of being unused for a long period of time.

[0069] Furthermore, this embodiment can be applied not only to detecting non-uniformity of the electrode state in the secondary battery 210 and determining whether it can be resolved, but also to control the secondary battery 210 during use to extend its lifespan and suppress its degradation.

[0070] 11...Measurement unit, 12...Calculation unit, 13...Recording unit, 14...Processing unit, 15...Comparison unit, 16...Determination unit, 17...Display unit, 18...Control unit, 100...Status determination system, 210...Secondary battery, 220...Control device, 300...Battery system.

Claims

1. A method for determining the internal state of a secondary battery, comprising: a calculation step of calculating a relaxation spectrum in a biaxial coordinate system where one axis represents relaxation time and the other axis represents intensity; a processing step of refreshing the non-uniformity of the internal state of the secondary battery; and a comparison step of comparing the shape information of the relaxation spectrum before and after the refresh processing.

2. A method for determining the state of a secondary battery according to claim 1, wherein the processing step includes at least one of the following for the secondary battery: full charge, intermittent charge, constant voltage charge, complete discharge, intermittent discharge, and constant voltage discharge.

3. A method for determining the state of a secondary battery according to claim 1, wherein the shape information includes at least one of the number of peaks in the relaxation spectrum, the position of the peaks, the area of ​​the peaks, the full width at half maximum of the peaks, and the skewness of the peaks.

4. A method for determining the state of a secondary battery according to any one of claims 1 to 3, characterized in that it determines whether or not to apply an additional refresh process to the secondary battery based on the comparison result of the shape information.

5. A method for determining the state of a secondary battery according to any one of claims 1 to 3, characterized in that it determines whether or not to change the operating method of the secondary battery or to replace the secondary battery based on the comparison result of the shape information.

6. A method for determining the state of a secondary battery according to any one of claims 1 to 3, characterized in that it includes the step of converting the comparison result of the shape information into at least one of numerical information, color information, sound information, and string of characters, and presenting the progress of the non-uniformity of the electrode state of the secondary battery.

7. A secondary battery state determination device for determining the internal state of a secondary battery, comprising: a calculation unit that calculates a relaxation spectrum in a biaxial coordinate system where one axis represents relaxation time and the other axis represents intensity; a processing unit that applies a process to refresh the non-uniformity of the internal state of the secondary battery; and a comparison unit that compares the shape information of the relaxation spectrum before and after the application of the refresh process.

8. A secondary battery state determination device according to claim 7, characterized in that it comprises a determination unit that determines, based on the comparison result of the comparison unit, whether the unevenness of the electrode state is resolvable due to the formation of a charge rate distribution.

9. A secondary battery having a state determination device for determining the internal state of the secondary battery, wherein the state determination device comprises: a calculation unit for calculating a relaxation spectrum in a biaxial coordinate system where one axis represents relaxation time and the other axis represents intensity; a processing unit for applying a process to refresh the non-uniformity of the internal state of the secondary battery; and a comparison unit for comparing the shape information of the relaxation spectrum before and after the application of the refresh process.

10. A secondary battery according to claim 9, wherein the state determination device comprises a determination unit that determines, based on the comparison result of the comparison unit, whether the unevenness of the electrode state is resolvable due to the formation of a charge rate distribution.

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