DETECTION APPARATUS, MANAGEMENT APPARATUS, AND DETECTION METHOD

Abstract

To detect the state of a lithium ion secondary battery by a simpler method.SOLUTION: A detection device according to the present disclosure that detects the state of a lithium-ion secondary battery includes a control unit that acquires the real part of the AC impedance at a frequency that is more than 10 times the real part of the AC impedance of 1 kHz due to the skin effect, and uses the obtained real part of the AC impedance to detect the presence of deposits of lithium and / or foreign metal inside the lithium-ion secondary battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] A detection apparatus, a management apparatus, and a detection method are disclosed herein. [Background technology]

[0002] Conventionally, a method for determining deterioration of a lithium secondary battery has been proposed in which the battery is discharged to SOC 10% or less, and the battery state is detected based on the measured value of the impedance of the battery (see, for example, Patent Document 1). This detection method is said to be able to detect the state of a lithium secondary battery simply and with high accuracy. Also, a method has been proposed in which the complex impedance at at least two different frequencies in the diffusion region of the secondary battery is linearly approximated to determine the battery as having a normal capacity balance if the angle of inclination is equal to or greater than a threshold, and the battery is determined as having an abnormal capacity balance if the angle of inclination is less than the threshold (see, for example, Patent Document 2). This detection method is said to be able to detect the battery state, particularly the normal / abnormal state of the battery and the degree of deterioration of the battery, with high accuracy by analyzing the complex impedance of the battery. Also, a method has been proposed in which the state change of the constituent members of the battery is detected based on the change in the peak of the relaxation time of the frequency band that appears in an arc shape on the Nyquist diagram obtained based on the measurement results of the AC impedance (see, for example, Patent Document 3). This detection method is said to be able to analyze the internal state or state change of the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-212513 A [Patent Document 2] International Publication No. 2013 / 115038 Brochure [Patent Document 3] International Publication No. 2017 / 179266 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned Patent Documents 1 to 3, the purpose is to detect the deterioration state of a lithium ion secondary battery, but the deterioration state of the battery includes, for example, deterioration accompanied by precipitation of lithium metal and deterioration not accompanied by precipitation of lithium metal, and it was not possible to detect such detailed states. For example, in Patent Document 1, the amount of deposited lithium is estimated from the reaction resistance value, but the reaction resistance value is a parameter that affects not only the amount of deposited lithium but also the amount of film formation, and it is difficult to say that the deposited lithium can be accurately diagnosed. In addition, in Patent Document 2, the normality or abnormality of the capacity balance is judged from the frequency differential of two or more complex impedances, but, for example, detection of lithium metal deposition was not considered. In addition, in Patent Document 3, the peak relaxation time is obtained from the Nyquist plot of the AC impedance to estimate the amount of film formed on the electrode, but the frequency band used is low, such as 10 mHz to 10 kHz or less, and it was difficult to separate the amount of deposited lithium from the amount of film formation. Thus, a technology for detecting the deterioration state of a lithium ion secondary battery in detail has been required.

[0005] The present disclosure has been made in consideration of such problems, and has as its main object to provide a new detection device, management device, and detection method that can detect the state of a lithium-ion secondary battery in more detail. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the inventors discovered that it is possible to obtain more detailed information about the state of lithium metal and foreign metals inside a lithium ion secondary battery, as well as the formation of a coating, from the AC impedance characteristics in a specific high frequency band, and have thus completed the invention disclosed in this specification.

[0007] That is, the detection device disclosed in the present specification is A detection device for detecting a state of a lithium ion secondary battery, a control unit that acquires a real part of AC impedance at a frequency that is 10 times or more higher than the real part of AC impedance at 1 kHz due to a skin effect, and detects the deposition of lithium and / or the presence of foreign metal inside the lithium ion secondary battery using the acquired real part of AC impedance; It is equipped with the following:

[0008] The management device disclosed in this specification is A management device that manages the lithium ion secondary battery based on information acquired from the above-mentioned detection device, a management unit that sets a recycling use of the lithium ion secondary battery using the detection result of lithium precipitation inside the lithium ion secondary battery output from the control unit; It is equipped with the following:

[0009] Alternatively, the management device disclosed in this specification may include: A management device that manages the lithium ion secondary battery based on information acquired from the above-mentioned detection device, a management unit that uses the detection result of the presence of foreign metal inside the lithium ion secondary battery output from the control unit to set whether or not the lithium ion secondary battery is to be shipped; It is equipped with the following:

[0010] The detection method disclosed herein comprises: A method for detecting a state of a lithium ion secondary battery, comprising: Detecting the presence of lithium deposition and / or foreign metals inside the lithium ion secondary battery using 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; It includes. Effect of the Invention

[0011] The present disclosure can provide a novel detection device, management device, and detection method capable of detecting the state of a lithium ion secondary battery in more detail. The reason why the present disclosure has such an effect is presumed to be as follows. For example, in a frequency band (for example, a frequency band of 100 kHz or more) that is so high that diffusion, reaction, movement, etc. of lithium ions, which are components of a lithium ion secondary battery, cannot be followed and is measurable, it is possible to capture the resistance decrease due to lithium deposition. It is also presumed that this high frequency band is not affected by deterioration due to diffusion, reaction, and movement other than that of lithium ions, and is sensitive only to metal deposition. Note that the frequency of the AC impedance substantially examined in Patent Documents 1 to 3 is in the range of 10 kHz or less, which is 1 / 1000 or less of the frequency of the present disclosure that shows 10 times or more due to the skin effect, and the information obtained is different. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a battery management system 10. [Diagram 2] FIG. 4 is a relationship diagram showing an example of the real part Z of AC impedance versus frequency. [Diagram 3] FIG. 4 is an explanatory diagram showing an example of an equivalent circuit model. [Figure 4] FIG. 11 is a diagram showing the relationship between frequency and real impedance part during degradation. [Diagram 5] 4 is a flowchart showing an outline of a calculation process for detecting a cell state. [Figure 6] 10 is a flowchart showing an example of a state detection processing routine. [Figure 7] 11 is a flowchart showing an example of a pre-shipment inspection process routine. [Figure 8] 11 is a flowchart showing an example of a collection determination process routine. [Figure 9] FIG. 13 is an explanatory diagram showing an example of data storage for cell lending. [Figure 10] FIG. 13 is an explanatory diagram showing an example of data storage for sell-through. [Figure 11]Relationship diagram between the capacitance retention rate at 100 kHz and the change amount of the real part of the impedance. [Figure 12] Relationship diagram between the capacitance retention rate at 1.5 MHz and the change amount of the real part of the impedance. [Figure 13] Relationship diagram between the capacitance retention rate at 20 MHz and the change amount of the real part of the impedance. [Figure 14] Relationship diagram between the capacitance retention rate and the estimated capacitance rate.

Embodiments for Carrying Out the Invention

[0013] (Battery Management System 10) Embodiments of the detection device disclosed in this specification will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram showing an example of the battery management system 10. The battery management system 10 is, for example, a system that executes the sales and usage management of manufactured lithium-ion secondary batteries (cells 30). This battery management system 10 includes a detection device 11 and a management device 20.

[0014] First, the cell 30 to be measured will be described. The cell 30 is configured as a lithium-ion secondary battery. The cell 30 may include, for example, a positive electrode, a negative electrode, and an ion conduction medium that is interposed between the positive electrode and the negative electrode and conducts carrier ions. The positive electrode may include, as a positive electrode active material, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, etc. The positive electrode active material is, for example, a lithium manganese composite oxide having a basic composition formula of Li (1-x) MnO2 (0 < x < 1, etc., the same below), Li (1-x) Mn2O4, etc., a lithium cobalt composite oxide having a basic composition formula of Li (1-x) CoO2, etc., a lithium nickel composite oxide having a basic composition formula of Li (1-x) NiO2, etc., a lithium nickel cobalt manganese composite oxide having a basic composition formula of Li (1-x) Ni a Co b Mn cO2 (a+b+c=1) or other lithium nickel cobalt manganese composite oxides can be used. The term "basic composition formula" means that other elements may be included. The negative electrode may include a carbon material or a composite oxide containing lithium as a negative electrode active material. Examples of the negative electrode active material 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 the carbon material include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite are preferred. Examples of the composite oxides include lithium titanium composite oxides and lithium vanadium composite oxides. The ion conductive medium can be, for example, an electrolyte in which a supporting salt is dissolved. Examples of the supporting salt include lithium salts such as LiPF6 and LiBF4. Examples of the solvent of the electrolytic solution include carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, which can be used alone or in combination. Specifically, examples of the carbonate 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-t-butyl carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate. The ion-conducting medium can be a solid ion-conducting polymer, an inorganic solid electrolyte, or a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bound by an organic binder. The solid electrolyte and the electricity storage device 13 may have a separator disposed between the positive electrode and the negative electrode.

[0015] The detection device 11 is a device that detects the deterioration state of the lithium ion secondary battery, for example, the presence of inactive lithium metal deposits or foreign metals inside the cell 30, the generation state of a coating, etc. The detection device 11 includes a control unit 12, a storage unit 13, a signal generator 14, a measurement unit 15, and a communication unit 16. The control unit 12 is configured as a microprocessor centered on 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 measurement unit 15, and the communication unit 16. The control unit 12 detects at least one of the deposition state of solid metallic lithium and the presence of foreign metals inside the cell 30 using information on the real part of the AC impedance acquired from the measurement unit 15. The storage unit 13 is configured as a large-capacity storage device, for example, an HDD, and stores information on the measurement results and various programs for inspecting the cell 30. The signal generator 14 is a device that generates a signal in a predetermined frequency band that is 10 times or more the real part of the AC impedance at 1 kHz due to the skin effect, and applies the signal of the generated frequency to the 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 may be a range of 100 kHz or more. FIG. 2 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, FIG. 2A is a relationship diagram of 1 Hz to 100 kHz, and FIG. 2B is a relationship diagram of 100 kHz to 100 MHz. The AC impedance measured in the vicinity of 1 kHz shows an ohmic resistance component. The detection device 11 detects the real part of the AC impedance at a frequency where the real part of the AC impedance is higher than the ohmic resistance, for example, 2 times, 5 times, or 10 times, i.e., a high frequency band. The signal generator 14 may apply a signal in a frequency band so high that the diffusion, reaction, and movement of lithium ions, which are components of a lithium ion secondary battery, cannot follow to the cell 30. The signal generator 14 may output a signal in a frequency band of, for example, 100 kHz or more, more preferably, a frequency of 200 kHz or more, and even more preferably, a frequency of 250 kHz or more.The signal generator 14 may output a signal in the range of 0.5 MHz to 5 MHz or a signal in the range of 10 MHz to 100 MHz. For example, the real part of the AC impedance in the range of 0.5 MHz to 5 MHz can determine deterioration due to deposition of inactive solid metallic lithium inside the cell 30, the presence of foreign metal, and the like. The real part of the AC impedance in the range of 10 MHz to 100 MHz can determine deterioration due to film formation. The measurement unit 15 measures at least one of the voltage and current responses from the cell 30 in response to the signal output from the signal generator 14 to the cell 30. The control unit 12 can obtain the response from the measurement unit 15 and determine the real and imaginary parts of the AC impedance. The communication unit 16 is an interface that communicates with external devices. The communication unit 16 communicates with external devices, a locally connected management device 20, and the like via an external network 17 such as the Internet, a LAN, and the like.

[0016] The management device 20 is a device that manages the cells 30 based on the information detected by the detection device 11. The management device 20 executes a process of setting the contents of collection, replacement, and maintenance of the used cells 30 by the management unit 21. The management unit 21 is configured as, for example, a microprocessor centered on a CPU, and controls the entire device. The management device 20 may use, for example, the detection result of the precipitation state of solid metallic lithium inside the cells 30 output from the detection device 11, and may use the cells 30 by limiting the recycling use based on the remaining capacity of the active lithium. Examples of recycling uses include reuse for predetermined normal uses such as in-vehicle batteries and mobile batteries, reuse for deterioration that does not require high output such as fixed-point power sources, and dismantling and recycling. The management device 20 may also perform a process of quantifying the remaining value of the lithium-ion secondary battery, including the remaining usage time, based on the remaining capacity of the active lithium, using the detection result of the precipitation state of solid metallic lithium inside the cells 30 output from the detection device 11. Alternatively, management device 20 may calculate the distribution value using the detection result of the precipitation state of solid metallic lithium inside cell 30 output from detection device 11, and output the calculated distribution value.

[0017] Here, the operation principle of the detection device 11 will be described. FIG. 3 is an explanatory diagram showing an example of an equivalent circuit model of a lithium-ion secondary battery, in which FIG. 3A is a mechanical structure model, FIG. 3B is a full model of the equivalent circuit, FIG. 3C is a simplified equivalent circuit model, and FIG. 3D is an equivalent circuit model with a high frequency function. FIG. 3D is a model in which parameters that can be considered to be almost zero impedance with a high frequency function are eliminated. FIG. 4 is a relationship diagram between frequency and real impedance part in degradation. Notes on each element are summarized in Table 1. FIG. 4 shows the impedance characteristic result calculated using the equivalent circuit model of FIG. 3 and formula (1). One of the degradation patterns of a lithium-ion secondary battery is the precipitation of lithium metal inside the battery, and there is a concern that the more metal precipitation there is, the more unsafe the battery becomes. Here, three states of a lithium-ion secondary battery were considered: an initial battery, a lithium precipitation-degraded battery, and a SEI (coating) precipitation-degraded battery. As shown in region A1 of FIG. 4, a decrease in the real part of the AC impedance can be confirmed in the range of 0.5 MHz or more, and in the range of 5 MHz or less, especially around 1 MHz, depending on the amount of lithium precipitation. On the other hand, in this frequency range, it can be confirmed that there is almost no change in the real part of the AC impedance in the SEI precipitation-degraded battery compared to the initial battery. 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 deterioration is due to lithium precipitation or film formation. In addition, an increase in impedance depending on the amount of SEI precipitation can be confirmed in the range of 10 MHz or more, and in the range of 100 MHz or less, especially in region A2 around 20 MHz. That is, it is presumed that in this frequency range, the effect of SEI precipitation deterioration is more significant than that of lithium precipitation deterioration. Note that FIG. 4 shows the calculation results using formula (1), but the results measured using a 18650-type lithium ion secondary battery also showed the same tendency as the waveform shown in FIG. 3. Therefore, it has been confirmed that the calculation results in FIG. 4 are correct.

[0018] [Table 1]

[0019] From FIG. 3D, the real part of the high-frequency AC impedance can be expressed by the following equation (1). Here, R Li In order to clarify the frequency dependence, R Li (ω), and R varies due to SEI precipitation. SEI In order to clarify the frequency dependence, R SEI (ω) (ω is the angular frequency). R Li (2πf) and R SEI (ω) and R Li (ω) and the parallel resistance R S The parameters other than R have almost no impedance fluctuation due to degradation. etc Then, equation (1) becomes R Li (ω) and R SEI (ω) and R S and R etc Here, the amount of metallic lithium precipitated can be rewritten as Q Li , the amount of precipitated SEI is Q SEI Then, the relational expression of impedance according to each deposition amount is expressed as the following equation (3). Here, α Li is the coefficient for converting the impedance of Li into the amount of deposition, α SEI is the coefficient for converting the impedance of the SEI into the amount of deposition, R init SEI (ω) is the impedance corresponding to the initial SEI, R degr SEI (ω) shows the impedance corresponding to the SEI after degradation. The reason why the SEI equation shows the difference is because the SEI is already formed in the initial battery and is observed as impedance. In the initial battery, metallic lithium has not been precipitated, and Q Li = 0, so R init SEI (ω)=∞(R init Li (ω) is the initial lithium impedance. Also, when the frequency is about 1 MHz, the SEI has almost no dielectric saturation loss, so R SEI (ω) = 0. At this time, the initial impedance Z init (ω) and impedance after degradation Z degr(ω) can be expressed by the following equations (4) and (5). Here, Q Li can be obtained from the following equation (6): Z init (ω) and Z degr (ω) is a value that can be obtained by measurement, and α Li , R S Since Q has a value specific to the battery material and shape, the amount of lithium deposition can be estimated. Next, the initial and post-degradation impedances at around 20 MHz can be expressed by the following equations (7) and (8). Similarly, Q can be calculated from the change in impedance before and after degradation. SEI can be obtained from the following equation (9). Here, k is a constant that depends on the frequency ratio due to the skin effect of lithium metal, and since 1 MHz (= ω1) is compared with 20 MHz (= ω2), k = √(ω2 / ω1). If the amount of capacity degradation of the battery is ΔCap, the following equation (10) holds, since deactivated lithium is generated as metallic lithium and SEI. Here, if the impedance at 1 MHz and the impedance at 20 MHz are obtained from equation (10), Q Li +Q SEI Since the capacity degradation can be calculated, the amount of metallic lithium deposition can be estimated by obtaining ΔCap and the impedance at 20 MHz. Therefore, for example, the ratio of metallic deposition in the degraded state can be estimated by using the impedance measurement results in these two frequency bands.

[0020]

number

[0021] (Detection method) Next, the operation of the detection device 11 of this embodiment thus configured, in particular, a detection method for detecting the state of a lithium ion secondary battery executed by the detection device 11 will be described. This detection method may include a detection step of detecting the deposition of lithium and / or the presence of foreign metal inside the lithium ion secondary battery using the real part of the AC impedance at a frequency that is 10 times or more the real part of the AC impedance of 1 kHz due to the skin effect. Furthermore, this detection method may include an acquisition step of applying a frequency that is 10 times or more the real part of the AC impedance of 1 kHz due to the skin effect to the lithium ion secondary battery before the detection step and acquiring the real part of the AC impedance. Here, for the convenience of explanation, the detection step will be mainly described as detecting the deposition of inactive solid metallic lithium and detecting deterioration of the battery.

[0022] FIG. 5 is a flow chart showing an outline of the calculation process for detecting the state of the cell mounted on the control unit 12, where FIG. 5A shows the calculation process in the frequency domain A1, and FIG. 5B shows the calculation process including the frequency domain A2. The control unit 12 calculates the deterioration amount and the amount of metallic lithium deposition of the cell 30 from the real part of the AC impedance in the high frequency band. In addition, by using the above-mentioned principle regarding the deposition of metallic lithium, it is possible to detect the resistance change caused when foreign metal is mixed inside the battery, and this information can be used to perform inspection before shipping and improve the quality in the production process. As shown in FIG. 5A, the control unit 12 measures the real part of the AC impedance of the cell 30 in the frequency domain A1, obtains the amount of change in the real part from the initial state, and executes a process of obtaining the amount of lithium metal deposition from the amount of change in the real part of the AC impedance using a MAP obtained in advance (S10). The MAP can be set based on, for example, the relationship between the amount of change in the real part of the AC impedance and the amount of lithium metal deposition empirically obtained in advance by experiments or the like. Then, the control unit 12 presents, for example, the safety factor of the corresponding cell 30 from the obtained amount of lithium metal deposition. Alternatively, as shown in Fig. 5B, after the calculation of S10, the control unit 12 measures the AC impedance of the cell 30 in the frequency domain A2, and executes a process of obtaining the remaining capacity SOC from the real part of the AC impedance using a previously obtained MAP (S20). The MAP can be set based on, for example, a relationship between the amount of change in the real part of the AC impedance and the remaining capacity SOC empirically obtained in advance through an experiment or the like. Then, the control unit 12 presents, for example, the safety factor and the remaining capacity SOC of the corresponding cell 30.

[0023] Next, a more specific process of the detection device 11 will be described. FIG. 6 is a flow chart showing an example of a state detection process routine executed by the control unit 12 of the detection device 11. This routine is executed at the timing of detecting the deterioration state of the cell 30. This timing may be, for example, when an operator inputs a command to start the routine, or may be the timing after a predetermined period of time during which deterioration can be recognized (for example, one week or one month has passed). The control unit 12 executes this routine using the signal generator 14 and the measurement unit 15. When this routine is started, the control unit 12 causes the signal generator 14 to generate a signal of a specific frequency (S100), and causes the measurement unit 15 to measure the voltage and / or current input / output / reflected to the cell 30 (S110). The specific frequency may be a frequency that is 10 times or more higher than the real part of the above-mentioned 1 kHz AC impedance due to the skin effect, or a frequency that is so high that diffusion, reaction, movement, etc. of lithium ions, which are components of a lithium ion secondary battery, cannot follow, such as a frequency of 100 kHz or more.

[0024] Next, the control unit 12 calculates the AC impedance from the acquired voltage and / or current (S120) and compares it with reference data (S130). The control unit calculates the real part of the AC impedance, and further calculates the difference between the calculated real part and the real part of the cell 30 in the initial state as the amount of change. The reference data may be, for example, a specified range that is specified as the amount of solid metallic lithium precipitation that can be safely charged and discharged in the cell 30 in a deteriorated state (for example, the range of S1 in FIG. 5A). Next, the control unit 12 determines whether the amount of change in the calculated real part of the AC impedance is within a specified range (S140), and if it is within the specified range, the control unit 12 stores the cell 30 in the storage unit 13 as a battery with a small amount of solid metallic lithium precipitation (S150) and ends this routine. On the other hand, if the amount of change in the real part of the AC impedance calculated in S140 is outside the specified range, the control unit 12 stores the cell 30 in the storage unit 13 as a battery with a large amount of solid metallic lithium precipitation (S160) and ends this routine. Here, the control unit 12 may output and display the determination result in S140 on a display unit (not shown).

[0025] Next, the evaluation process of the cell 30 executed using the detection result of the cell 30 in the state detection process routine will be described. FIG. 7 is a flow chart showing an example of a pre-shipment inspection process routine executed by the control unit 12 of the detection device 11. This routine is stored in the storage unit 13 and executed at the time of pre-shipment inspection after the manufacture of the cell 30. This routine may be executed by the management unit 21 of the management device 20. When this routine is started, the control unit 12 executes the above-mentioned state detection process (S200) and judges whether or not the amount of change in the real part of the obtained AC impedance is within a specified range (S210). When the amount of change in the real part of the obtained AC impedance is within the specified range, the control unit 12 outputs information that the cell 30 is free of foreign metal and can be shipped (S220), and ends this routine. On the other hand, when the amount of change in the real part of the obtained AC impedance is outside the specified range, the control unit 12 outputs information that the cell 30 is free of foreign metal and can be sent for dismantling and recycling (S230), and ends this routine. The control unit 12 may output this information to be stored in the memory unit 13, or may output it to be displayed on the display unit. Since solid metallic lithium generated by charging and discharging is not present inside the cell 30 immediately after manufacture, if the change in the real part of the AC impedance is outside a specified range, it can be determined that foreign metal is present inside the cell 30. Since such a cell 30 cannot be shipped, resources are utilized, for example, by dismantling and recycling.

[0026] Next, a process for selecting a reuse use of the cell 30, which is executed using the detection result of the cell 30 in the state detection process routine, will be described. FIG. 8 is a flow chart showing an example of a collection determination process 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 cell 30 is used and collected. This routine may be executed by the management unit 21 of the management device 20. When this routine is started, the control unit 12 executes the above-mentioned state detection process (S200), and obtains the deterioration degree from the real part of the obtained AC impedance (S300). The deterioration degree can be obtained, for example, from a relationship between the remaining capacity SOC obtained in the above-mentioned S20 and the deterioration degree, which is empirically obtained in advance.

[0027] Next, the control unit 12 judges whether the deterioration degree is within a predetermined allowable range (S310). This predetermined allowable range may be, for example, a range empirically defined as a limit amount of solid metallic lithium precipitation in a deteriorated cell 30 beyond which charging and discharging cannot be safely performed (for example, the range of S2 in FIG. 5A). When the deterioration degree is outside the allowable range, the control unit 12 outputs information to send the corresponding cell 30 to dismantle and recycle (S320). The control unit 12 may store and output this information to be stored in the storage unit 13, or may display and output this information to be displayed on the display unit. On the other hand, when the deterioration degree is within the allowable range in S310, the control unit 12 judges whether the amount of solid metallic lithium precipitation is within a specified range (S330). This amount of precipitation can be obtained by the process of S10 described above. In addition, the specified range may be, for example, a specified range defined as a amount of solid metallic lithium precipitation in a deteriorated cell 30 beyond which charging and discharging can be safely performed (for example, the range of S1 in FIG. 5A). When the amount of precipitation is within a specified range, the control unit 12 outputs information for reusing the cell 30 for normal use (S340) and ends this routine. On the other hand, when the amount of precipitation is outside the specified range, the control unit 12 outputs information for reusing the cell 30 for use corresponding to the deterioration (S350) and ends this routine. An example of a use corresponding to the deterioration is reusing an in-vehicle battery that requires high output in a short time as a fixed power source for a house or the like that does not require a high rate. In this way, by using the detection device 11, it is possible to grasp the degree of deterioration of the cell 30, and to grasp a more detailed deterioration state, such as whether the deterioration is due to the formation of a coating on the electrode or the precipitation of inactive solid metallic lithium on the electrode.

[0028] Here, the correspondence between the components of this embodiment and the components of this disclosure will be clarified. The cell 30 of this embodiment corresponds to the lithium ion secondary battery of this 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. Note that in this embodiment, an example of the detection method of the present disclosure is also clarified by explaining the operation of the detection device 11.

[0029] In the present embodiment described above, it is possible to provide a novel detection device 11, management device 20, and detection method that can detect the state of a lithium ion secondary battery in more detail. The reason why the present disclosure has such an effect is presumed to be as follows. For example, this is because it is possible to capture the resistance reduction due to lithium deposition at a frequency that is so high that diffusion, reaction, movement, etc. of lithium ions, which are components of a lithium ion secondary battery, cannot be followed, and in a measurable frequency band (for example, a frequency band of 100 kHz or more). It is also presumed to be because, in this high frequency band, it is not affected by deterioration due to diffusion, reaction, and movement other than that of lithium ions, and is sensitive only to metal deposition.

[0030] The detection device 11 also detects the presence of lithium precipitation and / or foreign metals inside the lithium ion secondary battery using the real part of the AC impedance in a frequency band of 100 kHz or more. In particular, the detection device 11 detects the presence of inactive solid metallic lithium precipitation and / or foreign metals inside the lithium ion secondary battery based on a decrease in the real part of the AC impedance obtained in a frequency range of 0.5 MHz to 5 MHz. The detection device 11 also estimates the amount of film precipitation on the electrode based on an increase in the real part of the AC impedance obtained in a frequency range of 10 MHz or more, and detects deterioration based on film formation. In this way, the detection device 11 can more clearly distinguish between a deterioration state based on the precipitation of solid metallic lithium and a deterioration state based on film formation by using a plurality of different frequency bands. Using the information obtained in this way, the inspection device 11 can more appropriately select a reuse use of the cell 30.

[0031] It goes without saying that the present disclosure is in no way limited to the above-described embodiment, and can be embodied in various forms as long as it falls within the technical scope of the present disclosure.

[0032] In the above-described embodiment, a battery management system 10 having one cell 30 has been described, but this is not limited to this, and the detection device 11 may be a battery management system 10 in which the cells 30 are directly connected, or a battery management system 10 in which the cells 30 are connected in parallel.

[0033] FIG. 9 is an explanatory diagram showing an example of data storage for cell rental. FIGS. 9 and 10 are examples of services that can be provided by the administrator. For example, if the battery management system 10 is used as a management algorithm for leased battery management, a rental service capable of managing safe use can be provided. As shown in FIG. 9, the battery leasing system 500 acquires information such as a customer ID, purpose of use, date of use, service points, and place of use from a customer. In addition, the battery leasing system 500 acquires information such as a battery ID of a used battery module, remaining capacity SOC, amount of stored power, lithium deposition state, deterioration state, and place of use. Then, the battery leasing system 500 executes the price of the battery module to be rented, compatibility with the customer, maintenance, and use safety management, and can rent an appropriate battery module to the customer.

[0034] FIG. 10 is an explanatory diagram showing an example of data storage for cell sales. For example, if the battery management system 10 is an algorithm for managing deterioration safety factors, a resale service for reuse can be constructed. As shown in FIG. 10, the battery reuse system 510 acquires information such as a customer ID, purpose of use, date of use, service points, and place of use from a customer. The battery reuse system 510 also acquires information such as a battery ID of a used battery module, remaining capacity SOC, amount of stored power, lithium deposition state, deterioration state, and place of use. The battery reuse system 510 then executes the price of the battery module to be rented, compatibility with the customer, maintenance, and usage safety management, and can sell appropriate battery modules to the customer for reuse.

[0035] In the above embodiment, the detection device 11 executes the pre-shipment inspection processing routine, i.e., the detection device 11 has the functions of the management device of the present disclosure, but the present invention is not limited to this, and the management device 20 may execute the pre-shipment inspection processing routine. Even in this case, the result of detecting the presence or absence of foreign metal can be appropriately used.

[0036] In the above embodiment, the detection device 11 executes the recovery determination process routine, i.e., the detection device 11 has the function of the management device of the present disclosure, but the present invention is not limited to this, and the management device 20 may execute the recovery determination process routine. Even in this case, information on the precipitation of solid metallic lithium can be appropriately used for reusing and recycling the cells 30. EXAMPLES

[0037] Below, an example in which the detection device and detection method of the present disclosure were specifically examined will be described as an experimental example.

[0038] (Experimental Example 1) The positive electrode active material is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A commercially available 18650 cylindrical lithium-ion secondary battery with a negative electrode active material of graphite was used for two types of degradation methods to prepare various degraded batteries with two types of degradation states. The first type was a degradation condition in which inactive solid metallic lithium was hardly precipitated, and a number of batteries were prepared by repeatedly charging and discharging at 60°C and 0.5C so that the degree of degradation relative to the initial capacity was about 92% to 84%. The second type was a degradation condition in which inactive solid metallic lithium was easily precipitated, and a number of batteries were prepared by repeatedly charging and discharging at 20°C and 2C so that the degree of degradation relative to the initial capacity was about 92% to 87%. The AC impedance of each battery 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 (Keysight E5061B), and then the impedance of the degraded battery prepared above was also measured in the same manner. The measurement conditions were a remaining capacity SOC of 40% and a measurement temperature of 20° C. The difference between the initial real part obtained by measurement and the real part after deterioration was calculated, and this was taken as the change in the real part of the AC impedance, ΔZre (mΩ).

[0039] (Calculation of capacity deterioration) The estimated capacity rate of each of the deteriorated batteries was calculated from the measured AC impedance using the above-mentioned formulas (9) and (10). The parameters used are summarized in Table 2.

[0040] [Table 2]

[0041] (Results and Discussion) FIG. 11 is a relationship diagram between the capacity remaining rate and the change in the impedance real part at 100 kHz in Experimental Example 1. FIG. 12 is a relationship diagram between the capacity remaining rate and the change in the impedance real part at 1.5 MHz in Experimental Example 1. FIG. 12 is a photograph of the electrodes after disassembly of a battery with a large amount of metallic lithium precipitation and a battery with no amount of precipitation. FIG. 13 is a relationship diagram between the capacity remaining rate and the change in the impedance real part at 20 MHz in Experimental Example 1. In addition, in FIGS. 11 to 14, a deteriorated battery without metallic lithium precipitation is represented by "○", and a deteriorated battery with metallic lithium precipitation is represented by "□". As shown in FIG. 11, the change in the real part of the AC impedance at a frequency of 100 kHz is not different in resistance depending on the presence or absence of metallic lithium precipitation, and a resistance change cannot be observed, whereas, as shown in FIG. 12, it was found that the value of the real part of the AC impedance decreases only in the deteriorated battery with metallic lithium precipitation at a frequency of 1.5 MHz. In order to confirm the presence or absence of precipitation, a representative battery of each deteriorated battery was disassembled and the amount of lithium precipitation was confirmed. It was confirmed that lithium was not precipitated in the degraded battery under the condition where metallic lithium was not precipitated, and that metallic lithium was precipitated in the degraded battery under the condition where metallic lithium was precipitated. As shown in Fig. 11 and Fig. 4, for example, it was found that the change in the real part of the AC impedance in the frequency band of 0.5 MHz to 5 MHz can separately detect the state of degradation due to the precipitation of metallic lithium from the state of degradation due to SEI generation. Also, as shown in Fig. 13, it was found that the resistance change from the initial time of the real part of the AC impedance at 20 MHz indicates that the change in the real part of the AC impedance fluctuates depending on the amount of the coating (SEI) formed on the electrode. That is, as shown in Fig. 13 and Fig. 4, it was found that the deterioration due to the formation of SEI can be evaluated from the change in the real part of the AC impedance in the frequency band of 10 MHz to 100 MHz, for example, from the initial time.

[0042] Fig. 14 is a relationship diagram between the remaining capacity rate (%) measured for a degraded battery and the estimated capacity rate (%) calculated from the AC impedance. The estimated capacity rate is a value of the degree of degradation calculated using the real part of the impedance at 1 MHz and 20 MHz. As shown in Fig. 14, the error between the measured remaining capacity rate (%) and the calculated estimated capacity rate (%) is within ±3%, indicating that a highly reliable degree of degradation can be obtained by calculation. [Industrial Applicability]

[0043] The detection device, management device, and detection method disclosed in this specification can be used in technical fields for detecting the state of lithium ion secondary batteries. [Explanation of symbols]

[0044] 10 battery management system, 11 detection device, 12 control unit, 13 memory unit, 14 signal generator, 15 measurement unit, 16 communication unit, 17 external network, 20 management device, 21 management unit, 30 cell, 500 battery leasing system, 510 battery reuse system.

Claims

1. A signal generator capable of outputting a signal having a frequency range of 100 kHz or more; a measurement unit that measures at least one of a voltage response and a current response from a battery to a signal of the frequency output from the signal generator; a control unit that measures an AC impedance based on the response and detects at least one of a presence of a foreign metal and a deposition of lithium in the battery based on the AC impedance; A measuring device comprising:

2. The measuring device according to claim 1, The measuring device according to claim 1, wherein the control unit includes a display unit that displays the state.

3. A method of measuring at least one of a voltage and a current response from a battery to a signal having a frequency in the range of 100 kHz or more; measuring an AC impedance based on the response and detecting at least one of a presence of foreign metal and lithium precipitation in the battery based on the AC impedance; A detection method comprising:

4. A signal generator capable of outputting a signal having a frequency in the range of 100 kHz or more; a measurement unit that measures at least one of a voltage response and a current response from a battery to a signal of the frequency output from the signal generator; a control unit that measures an AC impedance based on the response and determines whether the battery can be recycled or reused based on the AC impedance; A measuring device comprising:

5. The measuring device according to claim 4, The control unit determines, based on the AC impedance, whether the battery can be reused for normal use or whether it needs to be reused due to deterioration.

6. A signal generator capable of outputting a signal having a frequency in the range of 100 kHz or more; a measurement unit that measures at least one of a voltage response and a current response from a battery to a signal of the frequency output from the signal generator; a control unit that measures an AC impedance based on the response and detects at least one of a presence of a foreign metal and a deposition of lithium in the battery based on the AC impedance; Equipped with A battery management system that uses the status information to manage the lending of the batteries to customers.

7. A signal generator capable of outputting a signal having a frequency in the range of 100 kHz or more; a measurement unit that measures at least one of a voltage response and a current response from a battery to a signal of the frequency output from the signal generator; a control unit that measures an AC impedance based on the response and detects at least one of a presence of a foreign metal and a deposition of lithium in the battery based on the AC impedance; Equipped with A battery management system that uses the status information to manage sales of the batteries to customers.

8. A signal generator capable of outputting a signal in a first frequency band and a signal in a second frequency band higher than the first frequency band; measuring at least one of a voltage and a current response from the battery to the signal in the first frequency band as a first response, and measuring at least one of a voltage and a current response from the battery to the signal in the second frequency band as a second response; a control unit that determines whether the battery is degraded due to at least one of the presence of a foreign metal and lithium deposition or degradation due to film formation based on the first response and the second response; A measuring device comprising:

9. The measuring device according to claim 8, The control unit estimates a rate of deterioration of the battery due to at least one of the presence of the foreign metal and the precipitation of lithium.

10. The measuring device according to claim 8, The control unit estimates a proportion of deterioration of the battery caused by the formation of the film.

11. The measuring device according to claim 10, The measuring device according to claim 1, wherein the control unit includes a display unit that displays a result of the determination made by the control unit.

12. A battery manufacturing method, which detects the state of the battery using the detection method described in claim 3, and produces the battery according to the state.

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