Detection device, management device and detection method

Abstract

The present invention relates to a detection device, a management device, and a detection method. The detection device disclosed herein is a detection device for detecting the state of a lithium-ion secondary battery, and includes a control unit that obtains the real part of the AC impedance at a frequency that is 10 times greater than the real part of the AC impedance at 1 kHz due to the skin effect, and uses the obtained real part of the AC impedance to detect lithium precipitation and / or the presence of foreign metal within the lithium-ion secondary battery.

Description

Technical Field

[0001] This specification discloses a detection device, a management device, and a detection method. Background Art

[0002] In the past, as a method for determining the deterioration of lithium secondary batteries, a method has been proposed in which the battery is discharged to a SOC of less than 10% and the battery state is detected based on the measured value of the battery impedance (for example, see Patent Document 1). In this detection method, the state of the lithium secondary battery can be detected simply and with high precision. In addition, a method has been proposed in which the tilt angle when the complex impedance at at least two different frequencies within the diffusion region of the secondary battery is linearly approximated is calculated. If the tilt angle is above a threshold, the battery is determined to have a normal capacity balance. If the tilt angle is less than the threshold, the battery is determined to have an abnormal capacity balance in which the capacity balance is destroyed (for example, see Patent Document 2). In this detection method, the battery state, in particular, the normality / abnormality of the battery and the degree of battery degradation can be detected with high precision by analyzing the complex impedance of the battery. In addition, a method has been proposed in which, on the Nyquist plot obtained based on the measurement results of the AC impedance, the change in the state of the battery components is detected based on the change in the peak value of the relaxation time of the arc-shaped frequency band (for example, see Patent Document 3). In this detection method, the internal state or state change of the battery can be analyzed.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-212513

[0004] Patent Document 2: International Publication No. 2013 / 115038 Pamphlet

[0005] Patent Document 3: International Publication No. 2017 / 179266 Pamphlet

[0006] However, the aforementioned Patent Documents 1 to 3 aim to detect the degradation state of lithium-ion secondary batteries. However, battery degradation states include degradation with and without lithium metal deposition, and are unable to detect such detailed conditions. For example, Patent Document 1 estimates the amount of lithium deposition based on the reaction resistance value. However, the reaction resistance value is a parameter that affects not only the amount of lithium deposition but also the amount of film formation, making it difficult to accurately diagnose lithium deposition. Furthermore, Patent Document 2 determines the normality or abnormality of capacity balance based on the frequency differentials of two or more complex impedances, but does not consider, for example, the detection of lithium metal deposition. Furthermore, Patent Document 3 estimates the amount of film formation on the electrode by calculating the peak relaxation time from the Quest plot of the AC impedance. However, the frequency band used is low, such as 10 mHz to 10 kHz, making it difficult to separate the amount of lithium deposition from the amount of film formation. Thus, there is a need for technology that can detect the degradation state of lithium-ion secondary batteries in detail. Summary of the Invention

[0007] The present disclosure has been made in view of such problems, and an object of the present disclosure is to provide a novel detection device, a management device, and a detection method capable of detecting the state of a lithium-ion secondary battery in more detail.

[0008] In order to achieve the above-mentioned purpose, the inventors conducted in-depth research and found that based on the AC impedance characteristics of lithium-ion secondary batteries in a specific high-frequency band, the existence of lithium metal, foreign metal, film formation, etc. inside the battery can be obtained in more detail, thereby completing the invention disclosed in this specification.

[0009] That is, the detection device disclosed in this specification is a detection device for detecting the state of a lithium-ion secondary battery, wherein:

[0010] The detection device includes a control unit that obtains the real part of the AC impedance at a frequency that is 10 times or more higher than the real part of the AC impedance at 1 kHz due to the skin effect, and uses the obtained real part of the AC impedance to detect lithium precipitation and / or the presence of foreign metal inside the lithium ion secondary battery.

[0011] The management device disclosed in this specification is a management device for managing the lithium-ion secondary battery based on the information obtained from the above-mentioned detection device, wherein:

[0012] The management device includes a management unit configured to set a recycling purpose for the lithium ion secondary battery using the detection result of lithium deposition in the lithium ion secondary battery output from the control unit.

[0013] Alternatively, the management device disclosed in this specification is a management device that manages the lithium-ion secondary battery based on information obtained from the above-mentioned detection device, wherein:

[0014] The management device includes a management unit configured to determine whether the lithium ion secondary battery can be shipped, using the detection result of the presence of foreign metal inside the lithium ion secondary battery output from the control unit.

[0015] The detection method disclosed in this specification is a detection method for detecting the state of a lithium-ion secondary battery, wherein:

[0016] The detection method includes the steps of detecting lithium deposition and / or the presence of foreign metal in the lithium ion secondary battery using the real part of the AC impedance at a frequency 10 times or higher than the real part of the AC impedance at 1 kHz due to the skin effect.

[0017] Effects of the Invention

[0018] In the present disclosure, a novel detection device, management device and detection method that can detect the state of a lithium-ion secondary battery in more detail can be provided. The reason why the present disclosure achieves such an effect is speculated as follows. For example, this is because the diffusion, reaction, movement, etc. of the components of the lithium-ion secondary battery, i.e., lithium ions, cannot follow such a high frequency and can be measured in a frequency band (for example, a frequency band above 100 kHz), and the resistance reduction caused by lithium precipitation can be captured. In addition, it is speculated that this is because in this high frequency band, it is not affected by the deterioration of diffusion, reaction, and movement other than lithium ions, and is only sensitive to metal precipitation. In addition, in patent documents 1 to 3, the frequency of the AC impedance actually studied is in the range of less than 10 kHz, which is less than 1 / 1000 compared to the frequency of more than 10 times shown by the skin effect in the present disclosure, and the information obtained is different. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is an explanatory diagram showing an example of the battery management system 10 .

[0020] Figure 2A 、 Figure 2B 1 is a graph showing an example of the relationship between the real part Z of AC impedance and frequency.

[0021] Figures 3A to 3D It is an explanatory diagram showing an example of an equivalent circuit model.

[0022] Figure 4 This is a graph showing the relationship between the frequency and the real part of the impedance during degradation.

[0023] Figure 5A 、 Figure 5B This is a flowchart showing an outline of a calculation process for detecting the state of a battery cell.

[0024] Figure 6 This is a flowchart showing an example of a status detection processing routine.

[0025] Figure 7 This is a flowchart showing an example of a pre-shipment inspection processing routine.

[0026] Figure 8 This is a flowchart showing an example of a recovery determination processing routine.

[0027] Figure 9 This is an explanatory diagram showing an example of a data memory for lending out battery cells.

[0028] Figure 10 This is an explanatory diagram showing an example of a data memory for selling battery cells.

[0029] Figure 11 This is a graph showing the relationship between the remaining capacity and the change in the real part of the impedance at 100 kHz.

[0030] Figure 12 This is a graph showing the relationship between the remaining capacity ratio and the change in the real part of the impedance at 1.5 MHz.

[0031] Figure 13 This is a graph showing the relationship between the remaining capacity ratio and the change in the real part of the impedance at 20 MHz.

[0032] Figure 14 This is a graph showing the relationship between the remaining capacity rate and the estimated capacity rate. DETAILED DESCRIPTION

[0033] (Battery Management System 10)

[0034] Hereinafter, embodiments of the detection device disclosed in this specification will be described with reference to the accompanying drawings. Figure 1 1 is a schematic diagram illustrating an example of a battery management system 10. The battery management system 10 is a system for managing the sale and use of manufactured lithium-ion secondary batteries (battery cells 30). The battery management system 10 includes a detection device 11 and a management device 20.

[0035] First, the battery cell 30 to be measured is described. The battery cell 30 is configured as a lithium-ion secondary battery. The battery cell 30 may include, for example, a positive electrode, a negative electrode, and an ion-conducting medium disposed between the positive electrode and the negative electrode and conducting carrier ions. The positive electrode may include a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like as a positive electrode active material. The positive electrode active material may be, for example, a lithium-ion secondary battery having a basic composition formula of Li (1-x) MnO2 (0<x<1, etc., the same below), Li (1-x) Lithium manganese composite oxides such as Mn2O4, with the basic composition formula being Li (1-x) Lithium cobalt composite oxides such as CoO2, with the basic composition formula being Li (1-x) Lithium nickel composite oxides such as NiO2, with the basic composition formula being Li (1-x) Ni a Co b Mn cO2 (a + b + c = 1) and other lithium nickel cobalt manganese composite oxides. In addition, "basic composition formula" means that other elements may also be contained. The negative electrode may also contain carbon materials, composite oxides containing lithium, etc. as negative electrode active materials. Examples of negative electrode active materials include inorganic compounds such as lithium, lithium alloys, and tin compounds, carbon materials capable of absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of carbon materials include coke, glassy carbon, graphite, non-graphitizable carbon, pyrolytic carbon, and carbon fibers. Among them, graphites such as artificial graphite and natural graphite are preferred. Examples of composite oxides include lithium titanium composite oxides and lithium vanadium composite oxides. The ion conductive medium may be, for example, an electrolyte in which a supporting salt is dissolved. Examples of supporting salts include lithium salts such as LiPF6 and LiBF4. Examples of electrolyte solvents include carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, which can be used alone or in combination. Specifically, carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, and chloroethylene carbonate; and chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl n-butyl carbonate, methyl tert-butyl carbonate, diisopropyl carbonate, and tert-butyl isopropyl carbonate. Furthermore, the ion-conducting medium can utilize a solid ion-conducting polymer, an inorganic solid electrolyte, a hybrid material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bonded by an organic binder. The solid electrolyte and the battery cell 30 may also include a separator between the positive and negative electrodes.

[0036] The detection device 11 is a device that detects the deterioration state of the lithium-ion secondary battery, such as whether there are inactive lithium metal precipitates, foreign metal, the formation state of the coating, etc. inside the battery cell 30. The detection device 11 includes a control unit 12, a storage unit 13, a signal generator 14, a measuring unit 15, and a communication unit 16. The control unit 12 is configured as a microprocessor centered around a CPU, for example, and controls the entire device. The control unit 12 outputs signals to the storage unit 13, the signal generator 14, and the communication unit 16, and inputs signals from the storage unit 13, the measuring unit 15, and the communication unit 16. The control unit 12 uses the information of the real part of the AC impedance obtained from the measuring unit 15 to detect at least one of the precipitation state of solid metal lithium and the presence of foreign metal inside the battery cell 30. The storage unit 13 is configured as a large-capacity storage device such as an HDD, for example, and stores information on measurement results and various programs for inspecting the battery cell 30. The signal generator 14 is a device that generates a signal in a predetermined frequency band that is 10 times or more higher than the real part of the AC impedance at 1 kHz due to the skin effect, and applies the generated frequency signal to the battery cell 30. The predetermined frequency band for detecting the real part of the AC impedance may be, for example, a range exceeding 10 kHz or a range exceeding 100 kHz. Figure 2A 、 Figure 2B This is a relationship diagram showing an example of the real part Z of the AC impedance with respect to frequencies from low to high frequencies. Figure 2A This is a relationship diagram from 1Hz to 100kHz. Figure 2BThis is a relationship diagram from 100kHz to 100MHz. The AC impedance measured near 1kHz represents the ohmic resistance component. In the detection device 11, the real part of the AC impedance is detected at a frequency higher than the ohmic resistance, for example, 2 times, 5 times, 10 times, etc., that is, a high-frequency band. The signal generator 14 can also apply a signal of a high frequency band to the battery cell 30 that cannot track the diffusion, reaction, migration, etc. of lithium ions, etc., which are components of the lithium-ion secondary battery. For example, the signal generator 14 can output a signal in a frequency band above 100kHz, more preferably above 200kHz, and even more preferably above 250kHz. The signal generator 14 can also output a signal in the range of 0.5MHz to 5MHz, or a signal in the range of 10MHz to 100MHz. For example, based on the real part of the AC impedance in the range of 0.5MHz to 5MHz, it is possible to determine deterioration caused by the precipitation of inactive solid metal lithium inside the battery cell 30, the presence of foreign metal, etc. Furthermore, degradation due to film formation can be determined based on the real part of the AC impedance in the range of 10 MHz to 100 MHz. The measuring unit 15 measures at least one of the voltage and current responses from the battery cell 30 corresponding to the signal output from the signal generator 14 to the battery cell 30. The control unit 12 obtains the response from the measuring unit 15 and can determine the real and imaginary parts of the AC impedance. The communication unit 16 is an interface for communicating with external devices. The communication unit 16 communicates with external devices or a locally connected management device 20, etc., via an external network 17 such as the Internet, a LAN, etc.

[0037] The management device 20 manages battery cells 30 based on information detected by the detection device 11. The management device 20, through the management unit 21, executes processing to set the details of recycling, replacement, and maintenance for used battery cells 30. The management unit 21, for example, is configured as a microprocessor centered around a CPU, and controls the entire device. For example, the management device 20 can use the detection results of the solid metal lithium deposition state within the battery cells 30, output by the detection device 11, to limit the recycling purposes of the battery cells 30 based on the remaining active lithium capacity. Examples of recycling purposes include reuse for predetermined general uses such as automotive batteries and mobile batteries, reuse for deterioration that does not require high output, such as fixed-point power supplies, and disassembly and recycling. Furthermore, the management device 20 can use the detection results of the solid metal lithium deposition state within the battery cells 30, output by the detection device 11, to quantify the residual value of the lithium-ion secondary battery, including the remaining useful life, based on the remaining active lithium capacity. Alternatively, the management device 20 may calculate the circulation value using the detection result of the deposition state of solid metal lithium inside the battery cell 30 outputted from the detection device 11 , and output the calculated circulation value.

[0038] Here, the operating principle of the detection device 11 will be described. Figures 3A to 3D is an explanatory diagram showing an example of an equivalent circuit model of a lithium-ion secondary battery. Figure 3A It is a mechanical structure model. Figure 3B is the full model of the equivalent circuit, Figure 3C is a simplified equivalent circuit model, Figure 3D It is the equivalent circuit model under high frequency function. Figure 3D This model is created by excluding parameters that allow impedance to be roughly considered zero at high frequencies. Figure 4 This is a graph showing the relationship between the frequency and the real part of the impedance during degradation. Table 1 summarizes the notes related to each factor. Figure 4 Indicates use Figures 3A to 3D The equivalent circuit model and the impedance characteristic results calculated by formula (1). As one of the degradation modes of lithium-ion secondary batteries, there is the precipitation of lithium metal inside the battery. The more metal precipitation, the more likely the battery will become unsafe. Here, as the states of lithium-ion secondary batteries, three types are studied: initial battery, lithium precipitation deterioration battery, and SEI (film) precipitation deterioration battery. Figure 4As shown in region A1, in the range above 0.5 MHz and the range below 5 MHz, especially around 1 MHz, a decrease in the real part of the AC impedance can be confirmed according to the amount of lithium precipitation. On the other hand, in the SEI precipitation-degraded battery, it can be confirmed that there is almost no change in the real part of the AC impedance compared to the initial battery in this frequency region. That is, based on the amount of change in the real part such as the decrease in the real part of the AC impedance, it is possible to clearly distinguish whether the battery degradation is lithium precipitation or coating formation. In addition, in the range above 10 MHz and the range below 100 MHz, especially in region A2 around 20 MHz, an increase in impedance corresponding to the amount of SEI precipitation can be confirmed. That is, it can be inferred that in this frequency region, the influence of SEI precipitation degradation is more apparent than that of lithium precipitation degradation. In addition, Figure 4 The calculation results of formula (1) are also consistent with the results of the measurement using 18650 lithium-ion secondary batteries. Figures 3A to 3D The same trend as the waveform shown. Figure 4 The calculation result is correct.

[0039]

Table 1

[0040]

[0041] according to Figure 3D The real part of the high-frequency AC impedance can be expressed by the following formula (1). Li To explicitly show the frequency dependence, let R Li (ω), in order to adjust the R SEI To explicitly show the frequency dependence, let R SEI (ω)(ω is the angular frequency). Since R Li (2πf), R SEI (ω), R Li (ω) and the parallel resistance R S There is almost no impedance change due to degradation of the parameters other than R etc , then formula (1) can be used R Li (ω), R SEI (ω), R S and R etc Rewritten as the following formula (2): Here, the amount of metal lithium deposited is Q Li , the amount of SEI precipitation is set as Q SEI When α is α, the relationship between the impedance and the amount of precipitation is as follows (3). Li represents the coefficient for converting Li impedance into Li deposition amount, α SEI R represents the coefficient for converting SEI impedance into precipitation amount. initSEI (ω) represents the impedance corresponding to the initial SEI, R degr SEI (ω) represents the impedance corresponding to the degraded SEI. The difference is shown in the SEI formula because SEI has already formed in the initial battery and is observed as impedance. In the initial battery, metallic lithium has not been deposited, and Q Li =0, so R init SEI (ω)=∞(R init Li (ω) is the initial lithium impedance). In addition, at a frequency of about 1 MHz, SEI hardly experiences dielectric saturation loss, so R SEI (ω)=0. At this time, the initial impedance Z around 1MHz init (ω) and the degraded impedance Z degr (ω) can be expressed by the following equations (4) and (5). Here, Q can be obtained from the following equation (6) based on the impedance change before and after degradation: Li . Z init (ω) and Z degr (ω) is a value that can be obtained by measurement, α Li 、R S Since it has a value inherent to the material and shape of the battery, the amount of lithium deposition can be estimated. Next, the initial and post-degradation impedances around 20 MHz can be expressed by the following equations (7) and (8). Similarly, based on the impedance changes before and after degradation, Q can be obtained from the following equation (9): SEI Here, k is a constant that depends on the frequency ratio due to the skin effect of lithium metal. When 1 MHz (= ω1) is compared with 20 MHz (= ω2), it becomes k = √(ω2 / ω1). When the capacity degradation of the battery is ΔCap, the deactivated lithium is generated as metallic lithium and SEI, so the following formula (10) is established. Here, if the impedance of 1 MHz and the impedance of 20 MHz in formula (10) are obtained, Q is obtained. Li+ Q SEI , thus the amount of capacity degradation can be calculated. Similarly, by obtaining ΔCap and the impedance at 20 MHz, the amount of metallic lithium deposition can be estimated. Therefore, for example, using the impedance measurement results of these two frequency bands, the proportion of metal deposition in the degraded state can be estimated.

[0042]

Mathematical formula 1

[0043]

[0044] Z init (ω))=R S +R etc …Formula (4)

[0045]

[0046]

[0047]

[0048] ΔCap=Q Li +Q SEI …Formula (10)

[0049] (Detection Method)

[0050] Next, the operation of the detection device 11 of the present embodiment constructed in this manner, in particular, the detection method performed by the detection device 11 to detect the state of the lithium-ion secondary battery will be described. The detection method may also include the following detection step: using the real part of the AC impedance at a frequency that is 10 times or more than the real part of the AC impedance at 1kHz due to the skin effect to detect the precipitation of lithium and / or the presence of foreign metal inside the lithium-ion secondary battery. In addition, in the detection method, before the detection step, the following acquisition step may also be included: applying the real part of the AC impedance at a frequency that is 10 times or more than the real part of the AC impedance at 1kHz due to the skin effect to the lithium-ion secondary battery to acquire the real part of the AC impedance. Here, in the detection step, for the sake of convenience, the detection of the precipitation of inactive solid metal lithium and the detection of battery deterioration will be mainly described.

[0051] Figure 5A 、 Figure 5B 1 is a flowchart showing an outline of a calculation process for detecting the state of a battery cell mounted on the control unit 12. Figure 5A is the calculation processing in frequency area A1, Figure 5B This is a calculation process that includes the frequency region A2. The control unit 12 calculates the degradation amount of the battery cell 30 and the amount of metal lithium precipitation based on the real part of the AC impedance in the high frequency band. In addition, if the principle related to the precipitation of metal lithium is used, the resistance change caused by the mixing of foreign metal into the battery can be detected, and this information can be used for pre-shipment inspection to improve product quality in the production process. Figure 5A As shown, the control unit 12 measures the real part of the AC impedance of the battery cell 30 in the frequency region A1, calculates the change in the real part from the initial value, and uses the MAP (map) obtained in advance to perform a process (S10) to obtain the amount of lithium metal precipitation from the change in the real part of the AC impedance. The MAP can set the relationship between the change in the real part of the AC impedance and the amount of lithium metal precipitation based on data obtained empirically in advance through experiments, etc. Then, the control unit 12 prompts the safety rate of the corresponding battery cell 30, etc. based on the obtained amount of lithium metal precipitation. Or, as Figure 5BAs shown, after the calculation in S10, the control unit 12 measures the AC impedance of the battery cell 30 in frequency range A2 and uses a previously acquired MAP to calculate the remaining capacity (SOC) from the real part of the AC impedance (S20). The MAP can be set based on, for example, the relationship between the change in the real part of the AC impedance and the remaining capacity (SOC) obtained through prior experiments. The control unit 12 then displays information such as the safety factor and remaining capacity (SOC) of the corresponding battery cell 30.

[0052] Next, the processing of the detection device 11 will be described in more detail. Figure 6 This is a flowchart showing an example of a status detection processing routine executed by the control unit 12 of the detection device 11. The routine is executed at a timing when the degradation state of the battery cell 30 is detected. The timing can be, for example, when the operator inputs the start instruction of the routine, or after a prescribed period in which degradation can be identified (for example, after 1 week or after 1 month, etc.). The control unit 12 uses the signal generator 14 and the measuring unit 15 to execute the routine. When the routine is started, the control unit 12 causes the signal generator 14 to generate a signal of a specific frequency (S100) and causes the measuring unit 15 to measure the voltage and / or current input / output / reflected relative to the battery cell 30 (S110). The specific frequency can also be a frequency that is 10 times or more of the real part of the AC impedance of 1 kHz mentioned above due to the skin effect, a high frequency that cannot be followed by the diffusion, reaction, movement, etc. of lithium ions, etc., which are components of the lithium ion secondary battery, or a frequency of 100 kHz or more.

[0053] Next, the control unit 12 calculates the AC impedance based on the obtained voltage and / or current (S120) and compares it with the reference data (S130). The control unit calculates the real part of the AC impedance and then calculates the difference between the calculated real part and the real part of the battery cell 30 in the initial state as the change amount. The reference data can be, for example, a predetermined range (e.g., a predetermined range) that is defined as the amount of solid metal lithium that can be safely discharged in the degraded battery cell 30. Figure 5A 1 range, etc.). Next, the control unit 12 determines whether the change in the real part of the AC impedance determined is within a specified range (S140). If it is within the specified range, the control unit 12 stores the battery cell 30 in the storage unit 13 as a battery with a small amount of solid metal lithium precipitation (S150), and the routine ends. On the other hand, if the change in the real part of the AC impedance determined in S140 is outside the specified range, the control unit 12 stores the battery cell 30 in the storage unit 13 as a battery with a large amount of solid metal lithium precipitation (S160), and the routine ends. Here, the control unit 12 may also output the determination result in S140 to a display unit (not shown).

[0054] Next, the evaluation process of the battery cell 30 executed using the detection result of the battery cell 30 in the state detection process routine will be described. Figure 7 This is a flowchart showing an example of a pre-shipment inspection processing routine executed by the control unit 12 of the detection device 11. This routine is stored in the storage unit 13 and is executed during the pre-shipment inspection of the battery cell 30 after manufacture. Alternatively, this routine can be executed by the management unit 21 of the management device 20. When the routine begins, the control unit 12 performs the aforementioned state detection processing (S200) and determines whether the change in the real part of the AC impedance is within a specified range (S210). If the change in the real part of the AC impedance is within the specified range, the battery cell 30 is deemed to contain no foreign metal and a message indicating that the battery cell 30 is ready for shipment is output (S220), terminating the routine. On the other hand, if the change in the real part of the AC impedance is outside the specified range, the battery cell 30 is deemed to contain foreign metal and a message indicating that the battery cell 30 is to be dismantled and recycled is output (S230), terminating the routine. The control unit 12 may output this information for storage in the storage unit 13 or for display on the display unit. Since there is no solid metallic lithium generated by charging and discharging inside a battery cell 30 immediately after manufacture, if the change in the real part of the AC impedance is outside the specified range, it can be determined that foreign metal is present inside the battery cell 30. Since such battery cells 30 cannot be shipped, they can be disassembled and recycled, for example, to achieve resource utilization.

[0055] Next, a description will be given of a process for selecting a reuse purpose of the battery cell 30 executed using the detection result of the battery cell 30 in the state detection process routine. Figure 8 This is a flowchart illustrating an example of a recycling determination processing routine executed by the control unit 12 of the detection device 11. This routine is stored in the storage unit 13 and is executed after the battery cell 30 has been used and recycled. Alternatively, this routine may be executed by the management unit 21 of the management device 20. When this routine is initiated, the control unit 12 performs the aforementioned state detection processing (S200) and obtains the degree of degradation based on the real part of the AC impedance (S300). The degree of degradation can be determined, for example, by empirically determining the relationship between the remaining capacity (SOC) and the degree of degradation obtained in S20 above.

[0056] Next, the control unit 12 determines whether the degree of degradation is within a predetermined allowable range (S310). The predetermined allowable range may be determined based on experience (e.g., the amount of solid metal lithium precipitated in the degraded battery cell 30, which is a limit that makes charging and discharging impossible if the allowable range is exceeded). Figure 5AThe range of S2, etc.). When the degree of degradation is outside the allowable range, the control unit 12 outputs information to dismantle and recycle the corresponding battery cell 30 (S320). The control unit 12 can store the information in the storage unit 13 for storage output, or display the information on the display unit for display output. On the other hand, when the degree of degradation is within the allowable range in S310, the control unit 12 determines whether the amount of solid metal lithium precipitated is within the prescribed range (S330). The amount of precipitation can be obtained by the above-mentioned processing of S10. In addition, the prescribed range may also be, for example, a prescribed range prescribed as the amount of solid metal lithium precipitated that can safely perform charge and discharge in a degraded battery cell 30 (for example Figure 5A 's S1 range, etc.). When the precipitation amount is within the prescribed range, the control unit 12 outputs information on reuse in normal use of the battery cell 30 (S340), and ends the routine. On the other hand, when the precipitation amount is outside the prescribed range, the control unit 12 outputs information on reuse in use corresponding to the deterioration of the battery cell 30 (S350), and ends the routine. Uses corresponding to deterioration include, for example, reusing a vehicle-mounted battery that requires high output in a short period of time in a fixed power source such as a residence where a high ratio is difficult to require. In this way, when using the detection device 11, the degree of degradation of the battery cell 30 can be grasped, and more detailed degradation states such as whether the degradation is caused by the formation of a film on the electrode or the precipitation of inactive solid metal lithium on the electrode can be grasped.

[0057] Here, the correspondence between the components of this embodiment and the components of the present disclosure is clarified. The battery cell 30 of this embodiment corresponds to the lithium-ion secondary battery of the present disclosure, the detection device 11 corresponds to the detection device, the management device 20 corresponds to the management device, and the control unit 12 corresponds to the control unit. Furthermore, by describing the operation of the detection device 11 in this embodiment, an example of the detection method of the present disclosure becomes clear.

[0058] In the present embodiment described above, a novel detection device 11, a management device 20, and a detection method that can detect the state of a lithium-ion secondary battery in more detail can be provided. It is speculated that the reason why the present disclosure achieves such an effect is as follows. This is because, for example, the diffusion, reaction, movement, etc. of lithium ions, which are components of a lithium-ion secondary battery, cannot follow such a high frequency, and in a frequency band that can be measured (for example, a frequency band above 100kHz), the resistance reduction caused by lithium precipitation can be captured. In addition, it is speculated that this is because in the high frequency band, it is not affected by the deterioration of diffusion, reaction, and movement other than lithium ions, and is only sensitive to metal precipitation.

[0059] In addition, the detection device 11 uses the real part of the AC impedance in a frequency band above 100kHz to detect the precipitation of lithium and / or the presence of foreign metal inside the lithium-ion secondary battery. In particular, the precipitation of inactive solid metal lithium and / or the presence of foreign metal inside the lithium-ion secondary battery is detected based on the decrease in the real part of the AC impedance obtained in a frequency range of 0.5MHz to 5MHz. In addition, the detection device 11 estimates the amount of film precipitation on the electrode based on the increase in the real part of the AC impedance obtained in a frequency range of 10MHz and above, and detects degradation based on film formation. In this way, in the detection device 11, by using multiple different frequency bands, it is possible to more clearly distinguish between the degradation state based on the precipitation of solid metal lithium and the degradation state based on film formation. Using the information thus obtained, the detection device 11 can more appropriately select the reuse purpose of the battery cell 30.

[0060] In addition, the present disclosure is not limited to the above-mentioned embodiments, and can of course be implemented in various forms within the technical scope of the present disclosure.

[0061] In the above embodiment, the battery management system 10 including one battery cell 30 is described, but the present invention is not particularly limited thereto. The detection device 11 may be a battery management system 10 directly connected to the battery cell 30 or a battery management system 10 connected in parallel to the battery cells 30 .

[0062] Figure 9 This is an explanatory diagram showing an example of a data memory for lending out battery cells. Figure 9 、 10 This is an example of a service that a manager can provide. For example, if the battery management system 10 is used as a management algorithm for rental battery management, a loan service that can manage safe use can be provided. Figure 9 As shown, the battery rental system 500 obtains information from customers, including the customer ID, purpose of use, date of use, service points, and location of use. Furthermore, the battery rental system 500 obtains information about the battery module being used, including the battery ID, remaining capacity (SOC), stored capacity, lithium deposition status, degradation status, and location of use. The battery rental system 500 then manages pricing, customer matching, maintenance, and usage safety of the loaned battery modules, enabling it to loan appropriate battery modules to customers.

[0063] Figure 10 This is an explanatory diagram showing an example of a data storage device for selling battery cells. For example, if the battery management system 10 is set as an algorithm for managing degradation safety rate, a resale service for reuse can be constructed. Figure 10As shown, the battery recycling system 510 obtains information from customers, including the customer ID, purpose of use, date of use, service points, and location of use. Furthermore, the battery recycling system 510 obtains information about the used battery module, including the battery ID, remaining capacity (SOC), stored capacity, lithium deposition status, degradation status, and location of use. The battery recycling system 510 then manages pricing, customer matching, maintenance, and usage safety for the loaned battery modules, enabling appropriate reuse and sales of battery modules to customers.

[0064] In the above embodiment, the pre-shipment inspection process routine is executed by the detection device 11, that is, the detection device 11 has the function of the management device of the present disclosure. However, this is not particularly limited, and the pre-shipment inspection process routine may also be executed by the management device 20. In this way, the results of the detection of the presence of foreign metal can also be appropriately utilized.

[0065] In the above embodiment, the recovery determination processing routine is executed by the detection device 11, that is, the detection device 11 has the function of the management device of the present disclosure. However, this is not particularly limited, and the recovery determination processing routine can also be executed by the management device 20. In this way, information related to the precipitation of solid metallic lithium can also be appropriately used for the reuse and recovery of the battery cells 30.

[0066] [Example]

[0067] Hereinafter, an example of specifically studying the detection device and detection method of the present disclosure will be described as an experimental example.

[0068] (Experimental Example 1)

[0069] The positive electrode active material is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3Two degradation methods were used for commercially available 18650 cylindrical lithium-ion secondary batteries with O2 and graphite as the negative electrode active material, and various degraded batteries with two degradation states were prepared. The first is a degradation condition in which the precipitation of inactive solid metal lithium is extremely small. A plurality of batteries were prepared that were repeatedly cycled at 60°C and 0.5C with a degradation degree of about 92% to 84% relative to the initial capacity. The second is a degradation condition in which inactive solid metal lithium is easily precipitated. A plurality of batteries were prepared that were repeatedly cycled at 20°C and 2C with a degradation degree of about 92% to 87% relative to the initial capacity. For each battery, the AC impedance was measured under the same frequency range and the same remaining capacity SOC as the initial condition. First, the impedance of the initial battery was measured at 100kHz to 100MHz using a network analyzer (E5061B manufactured by Keysight), and the impedance of the degraded battery prepared above was also measured in the same manner. The measurement conditions are SOC 40% and a measurement temperature of 20°C. The difference between the measured initial real part and the real part after degradation is calculated and defined as the change in the real part of the AC impedance ΔZ. re (mΩ).

[0070] (Calculation of Capacity Degradation)

[0071] The estimated capacity ratios of the above-mentioned degraded batteries were calculated from the measured values of the AC impedance using the above-mentioned equations (9) and (10). The parameters used are summarized in Table 2.

[0072]

Table 2

[0073] symbol value <![CDATA[α Li ]]> 2 <![CDATA[α SEI ]]> 20 <![CDATA[R S (@1MHz)]]> 0.39 <![CDATA[R S (@20MHz)]]> 0.3

[0074] (Results and Investigation)

[0075] Figure 11 This is a graph showing the relationship between the remaining capacity ratio and the change in the real part of the impedance at 100 kHz in Experimental Example 1. Figure 12 This is a graph showing the relationship between the capacity remaining rate and the change in the real part of the impedance at 1.5 MHz in Experimental Example 1. Figure 12 Attached are photographs of disassembled electrodes of a battery with a large amount of metallic lithium deposition and a battery with no deposition. Figure 13 This is a graph showing the relationship between the capacity remaining rate and the change in the real part of the impedance at 20 MHz in Experimental Example 1. Figures 11-14 In the figure, the deteriorated battery without metal lithium precipitation is marked with "○", and the deteriorated battery with metal lithium precipitation is marked with "□". Figure 11 As shown, it can be seen that the change in the real part of the AC impedance at a frequency of 100kHz depends on whether there is precipitation of metallic lithium, but there is no difference in resistance, and the resistance change cannot be observed. Figure 12As shown in the figure, the real part of the AC impedance decreases only in the degraded battery where metallic lithium is deposited at a frequency of 1.5 MHz. In order to confirm the presence or absence of deposition, a representative battery of each degraded battery was disassembled and the amount of lithium deposition was confirmed. It was confirmed that lithium was not deposited in the degraded battery under the condition of no metallic lithium deposition, and metallic lithium was deposited in the degraded battery under the condition of metallic lithium deposition. Figure 11 、 Figure 4 As shown, for example, the degradation state caused by the precipitation of metallic lithium can be detected separately from the degradation state caused by SEI formation in the variation of the real part of the AC impedance in the frequency band of 0.5 MHz to 5 MHz. Figure 13 As shown in FIG, it can be seen that the amount of change in the real part of the AC impedance at 20 MHz varies with the amount of film (SEI) formed on the electrode. Figure 13 、 Figure 4 As shown, for example, it can be seen that the degradation caused by the formation of SEI can be evaluated based on the initial change in the real part of the AC impedance in a frequency band ranging from 10 MHz to 100 MHz.

[0076] Figure 14 This is a graph showing the relationship between the actual remaining capacity (%) of a deteriorated battery and the estimated capacity (%) calculated from the AC impedance. The estimated capacity is the value of the degree of deterioration calculated using the real part of the impedance at 1 MHz and 20 MHz. Figure 14 As shown, the error between the measured remaining capacity ratio (%) and the estimated capacity ratio (%) as a calculation result is within ±3%, and it can be seen that a highly reliable degradation degree can be obtained by calculation.

[0077] This application claims priority based on Japanese Patent Application No. 2021-003692, filed on January 13, 2021, the entire contents of which are incorporated herein by reference.

[0078] Industrial Applicability

[0079] The detection device, management device, and detection method disclosed in this specification can be used in the technical field of detecting the state of a lithium-ion secondary battery.

Claims

1. A detection device for detecting the state of a lithium-ion secondary battery, wherein: The detection device includes a control unit that obtains the real part of the AC impedance at a frequency that is 10 times or more higher than the real part of the AC impedance at 1 kHz due to the skin effect, and uses the obtained real part of the AC impedance to detect lithium precipitation and / or the presence of foreign metal inside the lithium ion secondary battery.

2. The detection device according to claim 1, wherein The control unit detects lithium deposition and / or the presence of foreign metal in the lithium ion secondary battery using a real part of AC impedance in a frequency band of 100 kHz or higher.

3. The detection device according to claim 1 or 2, wherein: The control unit detects lithium deposition and / or the presence of foreign metal in the lithium ion secondary battery based on a decrease in the real part of the AC impedance obtained within a frequency range of 0.5 MHz or more.

4. The detection device according to claim 1 or 2, wherein: The control unit estimates the amount of the deposited lithium that is deposited as inactive solid metal lithium.

5. The detection device according to claim 1 or 2, wherein: The control unit detects degradation caused by formation of a film on the electrode based on an increase in a real part of AC impedance obtained within a frequency range of 10 MHz or more.

6. The detection device according to claim 5, wherein: The control unit estimates the amount of film deposition.

7. A management device for managing the lithium-ion secondary battery based on information acquired from the detection device according to any one of claims 1 to 6, wherein: The management device includes a management unit configured to set a recycling purpose for the lithium ion secondary battery using the detection result of lithium deposition in the lithium ion secondary battery output from the control unit.

8. A management device for managing the lithium-ion secondary battery based on information acquired from the detection device according to any one of claims 1 to 6, wherein: The management device includes a management unit configured to determine whether the lithium ion secondary battery can be shipped, using the detection result of the presence of foreign metal inside the lithium ion secondary battery output from the control unit.

9. A detection method for detecting the state of a lithium-ion secondary battery, wherein: The detection method includes the steps of detecting lithium deposition and / or the presence of foreign metal in the lithium ion secondary battery using the real part of the AC impedance at a frequency 10 times or higher than the real part of the AC impedance at 1 kHz due to the skin effect.

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