Lithium metal battery degradation state determination device, lithium metal battery degradation state determination method, and program

Abstract

To accurately detect degradation of a lithium metal battery.SOLUTION: A degradation-state determination device for a lithium metal battery includes: an acquisition unit configured to acquire an anode resistance value obtained by applying a voltage to a lithium metal battery having an anode containing lithium; and a determination unit configured to determine the degradation state of the lithium metal battery on the basis of the estimated thickness of the anode estimated from the anode resistance value and the relationship between the anode resistance value and the first reference value related to the thickness of the anode, the relationship being defined by a first map.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lithium metal battery degradation state determination device, a lithium metal battery degradation state determination method, and a program.

Background Art

[0002] In recent years, research and development have been conducted to contribute to energy efficiency in order to enable more people to access affordable, reliable, sustainable, and advanced energy. Regarding such technologies, as a secondary battery, a lithium metal battery that uses lithium metal as a negative electrode has attracted attention. A lithium metal battery includes a positive electrode, a negative electrode having a metal lithium layer, and an electrolyte provided between the positive electrode and the negative electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in this technology, as the lithium metal battery is repeatedly charged and discharged, a SEI (Solid Electrolyte Interphase) film is formed and grows on the metal lithium layer of the negative electrode. Therefore, as the thickness of the negative electrode increases, a load is applied to the lithium metal along with the thickness of the negative electrode, and there is a concern about degradation that may cause structural damage to the lithium metal battery.

[0005] This invention was made in consideration of these circumstances, and one of its objectives is to enable accurate detection of degradation in lithium metal batteries. Ultimately, this contributes to energy efficiency. [Means for solving the problem]

[0006] The lithium metal battery degradation state determination device, lithium metal battery degradation state determination method, and program according to this invention employ the following configuration. (1) A lithium metal battery degradation state determination device according to one aspect of the present invention is a lithium metal battery degradation state determination device comprising: an acquisition unit that acquires resistance value information relating to the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode; a first map that shows the relationship between the thickness of the negative electrode and the resistance value, which has been prepared in advance; and a determination unit that determines the degradation state of the lithium metal battery based on the acquired resistance value information.

[0007] (2): In the embodiment of (1) above, the acquisition unit acquires the resistance value information based on the current value of the current discharged from the lithium metal battery.

[0008] (3) In the embodiment of (1) above, the determination unit determines that the lithium metal battery is in a state where it can be reused if the acquired resistance value is a resistance value such that the thickness of the negative electrode is less than or equal to the first reference value.

[0009] (4) In the embodiment of (3) above, the determination unit determines the degradation state of the lithium metal battery based on a second map that shows the relationship between the thickness of the positive electrode of the lithium metal battery and the resistance value, and determines that the degradation state of the lithium metal battery is such that the thickness of the positive electrode is less than or equal to the second reference value if the obtained resistance value is such that the thickness of the positive electrode is less than or equal to the second reference value.

[0010] (5) In the embodiment of (3) or (4) above, the lithium metal battery is a lithium metal battery mounted on a vehicle, and the acquisition unit acquires a resistance value obtained by applying an AC voltage to the lithium metal battery removed from the vehicle.

[0011] (6): In the embodiment of (1) above, the lithium metal battery is a lithium metal battery mounted on a vehicle, and the acquisition unit acquires a resistance value obtained by applying an AC voltage to the lithium metal battery mounted on the vehicle.

[0012] (7): In the embodiment of (1) above, the lithium metal battery is a lithium metal battery mounted on a vehicle, the acquisition unit acquires a measurement result of the current discharged from the lithium metal battery mounted on the vehicle at a timing after a predetermined time of 0.001 seconds to 1.0 seconds has elapsed, and acquires a preliminary determination result of preliminary determination of the deterioration state of the lithium metal battery based on the acquired measurement result, and the determination unit makes a preliminary determination of the deterioration state of the lithium metal battery based on the preliminary determination result of preliminary determination of the deterioration state of the lithium metal battery.

[0013] (8) A method for determining the degradation state of a lithium metal battery according to one aspect of the present invention is a method for determining the degradation state of a lithium metal battery, wherein a computer acquires resistance value information relating to the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode, and determines the degradation state of the lithium metal battery based on a first map showing the relationship between the thickness of the negative electrode and the resistance value, and the acquired resistance value information.

[0014] (9) A program according to one aspect of this invention causes a computer to acquire resistance value information regarding a resistance value obtained by applying a voltage to a lithium metal battery including a negative electrode containing lithium, and to determine a deterioration state of the lithium metal battery based on a first map showing a relationship between the thickness of the negative electrode created in advance and the resistance value, and the acquired resistance value information.

Advantages of the Invention

[0015] According to aspects (1) to (9), deterioration of a lithium metal battery can be accurately detected.

Brief Description of the Drawings

[0016] [Figure 1] It is a block diagram showing an example of a deterioration state determination device 100 of the first embodiment. [Figure 2] It is a diagram showing an example of a state where a lithium metal battery 10 is mounted on a vehicle M. [Figure 3] It is a diagram schematically showing a change in a negative electrode 12 when charge and discharge of a lithium metal battery 10 are repeated. [Figure 4] It is a diagram showing an example of a visualized deterioration determination map 121. [Figure 5] It is a diagram showing an example of a visualized preliminary determination map 122. [Figure 6] It is a flowchart showing an example of processing of a determination device 100 of the first embodiment. [Figure 7] It is a block diagram showing an example of a deterioration state determination device 200 of the second embodiment. [Figure 8] It is a diagram showing an example of a visualized bipolar deterioration determination map 123. [Figure 9] It is a flowchart showing an example of processing of a determination device 200 of the second embodiment. [Figure 10] It is a graph showing an example of a relationship between an impedance mainly derived from a resistance value and an impedance mainly derived from a capacitor component.

Modes for Carrying Out the Invention

[0017] Hereinafter, referring to the drawings, embodiments of a lithium metal battery degradation state determination device, a lithium metal battery degradation state determination method, and a program of the present invention will be described.

[0018] <First Embodiment> The first embodiment will be described. FIG. 1 is a block diagram showing an example of a degradation state determination device 100 according to the first embodiment. The degradation state determination device (hereinafter, determination device) 100 of the first embodiment determines the degradation state of the lithium metal battery 10. The lithium metal battery 10 includes a negative electrode containing lithium. The lithium metal battery 10 is a secondary battery that can be charged and discharged. The lithium metal battery 10 is, for example, mounted on a vehicle and used.

[0019] The determination device 100, for example, removes the lithium metal battery 10 mounted in the vehicle from the vehicle, determines its degradation state, and determines whether the degree of degradation of the lithium metal battery 10 is such that it can be reused. When the determination device 100 determines the degradation state of the lithium metal battery 10, an AC power supply 20 and an ammeter 30 are connected to the lithium metal battery 10. The degradation state of the lithium metal battery 10 determined by the determination device 100 is mainly a state related to the structural destruction of the lithium metal battery 10 based on the growth of the SEI layer adhering to the negative electrode.

[0020] Prior to the description of the determination device 100, the lithium metal battery 10 will be described. FIG. 2 is a diagram showing an example of a state where the lithium metal battery 10 is mounted on a vehicle M. In addition to the lithium metal battery 10, the vehicle M is equipped with an electrical device 40, a preliminary degradation measurement device 50, and a converter 60. In the vehicle M, when the vehicle M supplies power to the electrical device 40 by the lithium metal battery 10, the preliminary degradation measurement device 50 preliminarily measures the degradation of the lithium metal battery 10.

[0021] The lithium metal battery 10 is, for example, a semi-solid battery. The lithium metal battery 10 comprises, for example, a positive electrode 11, a negative electrode 12, and an electrolyte 13. The positive electrode 11 comprises, for example, a positive electrode current collector 11A and a positive electrode active material layer 11B. The positive electrode current collector 11A is made of, for example, a current collector foil such as aluminum. The positive electrode active material layer 11B is made of, for example, a layer such as lithium cobalt oxide.

[0022] The negative electrode 12 comprises, for example, a negative electrode current collector 12A and a negative electrode active material layer 12B. The negative electrode current collector 12A is made of, for example, a current collector foil made of copper. The negative electrode active material layer 12B is made of, for example, a metallic lithium layer. The electrolyte 13 is a semi-solid electrolyte containing lithium ions Li+. The electrolyte 13 is separated into a positive electrode 11 side and a negative electrode 12 side by a separator 13S.

[0023] During discharge, when the lithium metal battery 10 supplies power to the electrical equipment 40 mounted on the vehicle M, lithium ions (Li+) flow from the negative electrode active material layer 12B through the separator 13S to the positive electrode 11. Along with the flow of lithium ions (Li+), electrons (e) flow from the negative electrode 12 through the circuit of the electrical equipment 40 to the positive electrode 11. The flow of lithium ions (Li+) and electrons (e) causes a current to flow from the positive electrode 11 to the negative electrode 12, discharging the lithium metal battery 10. In the negative electrode active material layer 12B, metallic lithium dissolves as the lithium metal battery 10 discharges.

[0024] The lithium metal battery 10 is charged by a charging device 80 located outside the vehicle M. The charging device 80 is installed, for example, at the vehicle M owner's home or a charging station. During charging, lithium ions Li+ flow from the positive electrode active material layer 11B through the separator 13S to the negative electrode 12 side.

[0025] Along with the flow of lithium ions (Li+), electrons (e) flow from the positive electrode 11 through the charging equipment 80 to the 12 side. The flow of lithium ions (Li+) and electrons (e) causes an electric current to flow from the negative electrode 12 side to the positive electrode 11 side, charging the lithium metal battery 10. In the negative electrode active material layer 12B, metallic lithium is deposited as the lithium metal battery 10 is charged.

[0026] Figure 3 schematically shows the changes in the negative electrode 12 when the lithium metal battery 10 is repeatedly charged and discharged. As the lithium metal battery 10 is repeatedly charged and discharged, metallic lithium is deposited in the negative electrode active material layer 12B. As a result, over time, the SEI layer Q gradually thickens as the lithium metal battery 10 deteriorates, and the thickness of the negative electrode 12 gradually increases from the first thickness D1, to the second thickness D2, to the third thickness D3, and to the fourth thickness D4.

[0027] The electrical equipment 40 includes various devices mounted on the vehicle M and powered by the lithium metal battery 10. The electrical equipment 40 includes, for example, a drive motor for moving the vehicle M, an air conditioning control device for controlling the air conditioning inside the vehicle M, and a monitor for displaying images to provide various information to the occupants.

[0028] The preliminary degradation measurement device 50 includes, for example, a voltage detector 51, a current detector 52, a calculation device 53, and a supply device. The voltage detector 51 detects the voltage value of the terminal voltage of the lithium metal battery 10. The current detector 52 detects the current value of the current flowing from the positive electrode 11 to the negative electrode 12 of the lithium metal battery 10.

[0029] The calculation unit 53 estimates the degree of SEI film growth in the lithium metal layer of the lithium metal battery 10 based on the voltage value detected by the voltage detector 51 and the current value detected by the current detector 52. In estimating the degree of SEI film growth, the calculation unit 53 measures the current discharged from the lithium metal battery 10 mounted on the vehicle M at a predetermined time of 0.001 seconds to 1.0 seconds, for example, after 0.1 seconds have elapsed.

[0030] The arithmetic unit 53 measures the voltage drop after 0.1 seconds based on the voltage value output by the voltage detector 51, for example. The arithmetic unit 53 further measures the current after 0.1 seconds based on the current value output by the current detector 52. The arithmetic unit 53 calculates the impedance after 0.1 seconds (hereinafter referred to as 0.1-second resistance) based on the measured voltage drop after 0.1 seconds and current after 0.1 seconds. Specifically, the arithmetic unit 53 calculates the 0.1-second resistance as the value obtained by dividing the voltage drop after 0.1 seconds by the current after 0.1 seconds. The 0.1-second resistance increases with the number of charge-discharge cycles of the lithium metal battery 10.

[0031] The providing device 54 stores the 0.1-second resistance calculated by the arithmetic unit 53. When the lithium metal battery 10 is removed from the vehicle M and connected to the determination device 100, the providing device 54 provides the determination device 100 with some or all of the stored 0.1-second resistance values, for example, the latest value of the 0.1-second resistance.

[0032] Returning to Figure 1, the AC power supply 20 applies a test voltage to the lithium metal battery 10 according to the control of the determination device 100. The test voltage is applied to the lithium metal battery 10 as, for example, an AC current. The ammeter 30 is connected to the lithium metal battery 10. The ammeter 30 measures the current value of the current discharged from the lithium metal battery 10 to which the test voltage has been applied by the AC power supply 20. The ammeter 30 transmits a current signal based on the measured current value to the determination device 100.

[0033] The determination device 100 includes, for example, a communication unit 110, a storage unit 120, and a processing unit 130. The communication unit 110 transmits and receives signals between the determination device 100 and an external device. For example, the communication unit 110 transmits a current supply signal generated by the processing unit 130 to the AC power supply 20. The communication unit 110 receives a current signal transmitted by the ammeter 30. The transmission and reception performed by the communication unit 110 may be wired communication via wiring or wireless communication via a network.

[0034] The storage unit 120 consists of, for example, an HDD (Hard Disk Drive) or flash memory. The storage unit 120 stores a degradation determination map 121 and a preliminary determination map 122. The degradation determination map 121 is a map that shows the relationship between the thickness of the negative electrode 12 and the resistance value of the lithium metal battery 10, and is a pre-created map.

[0035] Figure 4 shows an example of a visualized degradation judgment map 121. The degradation judgment map 121 is obtained, for example, by measuring the 0.1-second resistance or AC impedance when an AC voltage is applied to a lithium metal battery 10 with a known thickness of the negative electrode 12 generated for testing, determining the bulk resistance and negative electrode reaction resistance, and then determining the resistance value for the thickness of the negative electrode 12.

[0036] The degradation determination map 121 may be created using a lithium metal battery in which the thickness of the negative electrode 12 is unknown. In this case, the degradation determination map 121 may be generated by measuring the thickness of the negative electrode 12 when an AC voltage is applied to the lithium metal battery 10, and by utilizing the resistance value calculated when an AC voltage is applied to the lithium metal battery 10. The degradation determination map 121 is an example of a first map.

[0037] The degradation judgment map 121 includes a first criterion value B1, which serves as a standard for determining whether the lithium metal battery 10 has degraded to the point where it is no longer reusable. The first criterion value B1 is, for example, a resistance value corresponding to the thickness of the negative electrode 12 at which the growth of the SEI layer formed on the negative electrode 12 progresses, and it is judged that there is a high possibility that the lithium metal battery 10 will undergo structural failure.

[0038] The preliminary determination map 122 is, for example, a map showing the relationship between the thickness of the negative electrode 12 and the resistance value of the 0.1-second resistance, and is a pre-created map. Figure 5 shows an example of a visualized preliminary determination map 122. The preliminary determination map 122 is calculated, for example, using a resistance value calculated based on the current value of the current discharged from a lithium metal battery 10 whose thickness of the negative electrode 12 is known. The preliminary determination map 122 may also be generated by measuring the thickness of the negative electrode 12 when current is discharged from the lithium metal battery 10, and using a resistance value calculated based on the current value of the current discharged from the lithium metal battery 10.

[0039] The preliminary judgment map 122 includes a preliminary reference value B0, which serves as a criterion for preliminaryly determining whether the lithium metal battery 10 has deteriorated to the point where it is no longer reusable. The preliminary reference value B0 is, for example, a resistance value corresponding to the thickness of the negative electrode 12 at which it is judged that the growth of the SEI layer formed on the negative electrode 12 has progressed and the lithium metal battery 10 may be at risk of structural failure. The preliminary reference value B0 is greater than the first reference value B1.

[0040] The processing unit 130 includes, for example, a control unit 131, an acquisition unit 132, and a determination unit 133. These components are realized, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphics Processing Unit), or by the cooperation of software and hardware.

[0041] The program may be stored in advance in a storage unit 120 (a storage device equipped with a non-transient storage medium) such as an HDD or flash memory, or it may be stored in a removable storage medium (a non-transient storage medium) such as a DVD or CD-ROM, and installed when the storage medium is inserted into a drive device.

[0042] The control unit 131 comprehensively controls the operation of the determination device 100 when it determines the degradation state of the lithium metal battery 10. For example, when the determination of the degradation state of the lithium metal battery 10 is initiated, the control unit 131 generates a current supply signal to the AC power supply 20 to apply a predetermined AC voltage as a test voltage to the lithium metal battery 10 and transmits it to the AC power supply 20.

[0043] The acquisition unit 132 acquires resistance value information related to the resistance value obtained by applying a voltage to the lithium metal battery 10. The acquisition unit 132 acquires, for example, a current signal transmitted by the ammeter 30 and received by the communication unit 110. Based on the acquired current signal, the acquisition unit 132 acquires the current value of the current discharged by the lithium metal battery 10 to which the test voltage has been applied.

[0044] The acquisition unit 132 calculates the resistance value of the lithium metal battery 10 based on the acquired current value and the voltage value of the voltage applied to the lithium metal battery 10 by the AC power supply 20. The acquisition unit 132 calculates the resistance value of the lithium metal battery 10 by, for example, dividing the acquired current value by the voltage value of the voltage applied to the lithium metal battery 10. The acquisition unit 132 acquires the calculated resistance value as resistance value information. The acquisition unit 132 further acquires 0.1-second resistance information provided by the lithium metal battery 10 supply device 54 as a preliminary determination result of preliminary determination of the lithium metal battery 10.

[0045] The determination unit 133 determines the degradation state of the lithium metal battery 10 based on the degradation determination map 121 and the resistance value information acquired by the acquisition unit 132. For example, the determination unit 133 calculates the thickness of the negative electrode 12 in the lithium metal battery 10 by referring the resistance value based on the acquired resistance value information to the degradation determination map 121. The determination unit 133 determines the degradation state of the lithium metal battery 10 by comparing the calculated thickness of the negative electrode 12 with the first reference value B1.

[0046] Before determining the degradation state of the lithium metal battery 10 by comparing the thickness of the negative electrode 12 with the first reference value B1, the determination unit 133 makes a preliminary determination of the degradation state of the lithium metal battery 10 based on the 0.1-second resistance provided by the lithium metal battery 10 supplying device 54 and acquired by the acquisition unit 132, and the preliminary determination map 122. For example, the determination unit 133 refers the 0.1-second resistance to the preliminary determination map 122 and makes a preliminary determination of the degradation state of the lithium metal battery 10 by comparing the 0.1-second resistance with the preliminary reference value B0.

[0047] Next, the processing in the determination device 100 of the first embodiment will be described. Figure 6 is a flowchart showing an example of the processing in the determination device 100 of the first embodiment. The flowchart shown in Figure 6 is executed after the lithium metal battery 10 removed from the vehicle M is connected to the determination device 100.

[0048] First, the determination device 100 acquires the latest 0.1-second resistance provided by the lithium metal battery 10 supply device 54 in the acquisition unit 132 (step S101). Subsequently, the determination unit 133 refers to the 0.1-second resistance acquired by the acquisition unit 132 in the preliminary determination map 122 (step S103) and determines whether the acquired 0.1-second resistance exceeds the preliminary reference value B0 (step S105).

[0049] If the determination unit 133 determines that the acquired 0.1-second resistance exceeds the preliminary reference value B0, the determination device 100 performs impedance measurement (step S107) to obtain the resistance value of the lithium metal battery 10. In impedance measurement, first, the control unit 131 transmits a current supply signal to the AC power supply 20. After the AC power supply 20 receives the current supply signal and applies a test voltage to the lithium metal battery 10, the ammeter 30 measures the current value of the current discharged from the lithium metal battery 10, generates a current signal based on the current value, and transmits it to the determination device 100.

[0050] The determination device 100 acquires the current signal transmitted by the ammeter 30 in the acquisition unit 132. Subsequently, the acquisition unit 132 calculates the resistance value of the lithium metal battery 10 based on the current value based on the acquired current signal and the voltage value of the voltage applied to the lithium metal battery 10 by the AC power supply 20, and acquires the resistance value information. Impedance measurement is performed in this manner.

[0051] Next, the determination unit 133 refers to the resistance value based on the resistance value information acquired by the acquisition unit 132 in the degradation determination map 121 (step S109) and determines whether the resistance value of the lithium metal battery 10 exceeds the first reference value B1 (step S111). If it is determined that the resistance value of the lithium metal battery 10 exceeds the first reference value B1, the determination unit 133 determines that the lithium metal battery 10 cannot be reused (step S113). In this way, the determination device 100 completes the process shown in Figure 6.

[0052] In step S105, if the determination unit 133 determines that the acquired 0.1-second resistance does not exceed the preliminary reference value B0 (is less than or equal to the preliminary reference value B0), the determination unit 133 determines that reuse is possible (step S115), and the determination device 100 terminates the process shown in Figure 6. Also, if in step S111 the determination unit 133 determines that the resistance value of the lithium metal battery 10 does not exceed the first reference value B1 (is less than or equal to the first reference value B1), the determination unit 133 determines that reuse is possible (step S115), and the determination device 100 terminates the process shown in Figure 6.

[0053] The determination device 100 of the first embodiment uses a degradation determination map 121 to determine the degradation of the lithium metal battery 10. Therefore, the degradation of the lithium metal battery 10 can be determined with high accuracy. Furthermore, when the lithium metal battery 10 is removed from the vehicle, the determination device 100 of the first embodiment determines whether or not the lithium metal battery 10 that has been pre-determined to be degraded based on the 0.1-second resistance can be reused. Therefore, the determination of degradation for lithium metal batteries 10 that are unlikely to be reused can be omitted, and the reusability of the lithium metal battery 10 can be determined efficiently.

[0054] <Second Embodiment> Next, a second embodiment will be described. Figure 7 is a block diagram showing an example of the determination device 200 of the second embodiment. The second embodiment differs from the first embodiment mainly in that the bipolar degradation determination map 123 is stored in the storage unit 120 and in the processing that utilizes the bipolar degradation determination map 123. In the following description, elements common to the first embodiment may be denoted by the same reference numerals and their descriptions may be omitted.

[0055] In the second embodiment of the determination device 100, the storage unit 120 stores a bipolar degradation determination map 123 instead of a degradation determination map 121. The bipolar degradation determination map 123 is a map that shows the relationship between the degree of degradation of the positive electrode 11 and the negative electrode and the resistance value of the lithium metal battery 10, and is a pre-created map. Figure 8 shows an example of a visualized bipolar degradation determination map 123.

[0056] The bipolar degradation determination map 123 is generated, for example, using the resistance values ​​calculated when an AC voltage is applied to a lithium metal battery 10 whose degradation levels of the positive electrode 11 and negative electrode are known. The degradation level of the positive electrode 11 is, for example, reflected in the changes between the layers of the positive electrode 11. As the degradation of the positive electrode 11 progresses, the thickness of the positive electrode 11 increases, and as a result, the resistance value of the lithium metal battery 10 increases. The degradation level of the negative electrode 12 is, for example, determined using the thickness of the negative electrode 12 in the first embodiment.

[0057] The bipolar degradation determination map 123 includes a positive electrode degradation determination map 124 and a negative electrode degradation determination map 125. The positive electrode degradation determination map 124 is obtained, for example, by measuring the 0.1-second resistance or AC impedance of the lithium metal battery 10, determining the bulk resistance and positive electrode reaction resistance, and then determining the resistance value relative to the thickness of the positive electrode 11. The negative electrode degradation determination map 125 is a map similar to the degradation determination map 121 in the first embodiment. The positive electrode degradation determination map 124 is an example of a second map.

[0058] The positive electrode degradation determination map 124 and the negative electrode degradation determination map 125 are set with a second criterion value B2 and a third criterion value B3, respectively, which serve as criteria for determining whether the lithium metal battery 10 has deteriorated to the point where it is no longer reusable. The second criterion value B2 is, for example, a resistance value corresponding to the thickness of the positive electrode 11 at which it is judged that the deterioration of the positive electrode 11 has progressed to the point where it is highly likely that the lithium metal battery 10 cannot be reused. The third criterion value B3 is, for example, a value corresponding to the first criterion value B1 in the first embodiment.

[0059] Next, the processing in the determination device 200 of the second embodiment will be described. Figure 9 is a flowchart showing an example of the processing in the determination device 200 of the second embodiment. The flowchart shown in Figure 9 is executed, for example, after it is determined that the preliminary reference value has been exceeded up to step S105 shown in Figure 6 of the first embodiment.

[0060] The determination device 200 first performs impedance measurement (step S201) to obtain the resistance value of the lithium metal battery 10. In the impedance measurement, the ammeter 30 measures the current value of the current discharged from the lithium metal battery 10 using the same procedure as in the first embodiment, generates a current signal based on the current value, and transmits it to the determination device 100. The determination device 100 calculates the resistance value of the lithium metal battery 10 using the same procedure as in the first embodiment and obtains the resistance value information.

[0061] Next, the determination unit 133 refers to the resistance value based on the resistance value information acquired by the acquisition unit 132 in the bipolar degradation determination map 123 (step S203) and determines whether the resistance value of the lithium metal battery 10 exceeds the second reference value B2 or the third reference value B3 (step S205). If it is determined that the resistance value of the lithium metal battery 10 exceeds the second reference value B2 or the third reference value B3, the determination unit 133 determines that the lithium metal battery 10 cannot be reused (step S207). Thus, the determination device 200 terminates the process shown in Figure 9. If it is determined that the resistance value of the lithium metal battery 10 does not exceed either the second reference value B2 or the third reference value B3 (i.e., it is less than or equal to the second reference value B2 and the third reference value B3), the determination unit 133 determines that it can be reused (step S209). Thus, the determination device 100 terminates the process shown in Figure 9.

[0062] Here, we will explain the procedure for determining the bulk resistance, negative electrode reaction resistance, and positive electrode reaction resistance used when generating the bipolar degradation judgment map 123. Figure 10 is a graph showing an example of the relationship between impedance mainly derived from resistance and impedance mainly derived from the capacitor component. In Figure 10, the horizontal axis shows impedance mainly derived from resistance, and the vertical axis shows impedance mainly derived from the capacitor.

[0063] Figure 10 shows the relationship between the impedance derived from the measured resistance value (hereinafter referred to as resistance impedance) and the impedance mainly derived from the capacitor component (hereinafter referred to as capacitor impedance) for three lithium metal batteries 10. The measurement results for each of the three lithium metal batteries 10 are shown as the first measurement result, the second measurement result, and the third measurement result.

[0064] In the first capacitor curve K1, second capacitor curve K2, and third capacitor curve K3, which show the first, second, and third measurement results, respectively, the capacitor impedance is 0 before an AC voltage is applied to the lithium metal battery 10. From this state, when an AC voltage is applied to the lithium metal battery 10, both the resistive impedance and the capacitor impedance increase.

[0065] Initially, when an AC voltage is applied to the lithium metal battery 10, the capacitor impedance increases as the resistance impedance increases. However, once the resistance impedance reaches its first peak, the relationship changes so that the capacitor impedance decreases as the resistance impedance increases. Furthermore, once the resistance impedance reaches its first lowest point, the relationship returns to one where the capacitor impedance increases as the resistance impedance increases. As a result, the first capacitor curve K1, the second capacitor curve K2, and the third capacitor curve K3 generate the first convex first circular arcs K11, K21, and K31.

[0066] Next, when the resistive impedance reaches a second peak, the relationship becomes such that the capacitor impedance decreases as the resistive impedance increases. Furthermore, once the resistive impedance reaches its second lowest point, the relationship becomes such that the capacitor impedance increases as the resistive impedance increases. As a result, the first capacitor curve K1, the second capacitor curve K2, and the third capacitor curve K3 generate second circular arcs K12, K22, and K32, which are convex at the top of the first curve. If there is no capacitor component in the lithium metal battery 10, the first capacitor curve K1, the second capacitor curve K2, and the third capacitor curve K3 are all linear.

[0067] Since the lithium metal battery 10 contains a capacitor component, the first capacitor curve K1, the second capacitor curve K2, and the third capacitor curve K3 generate first circular arcs K11, K21, K31 and second circular arcs K12, K22, K32, respectively. In the first capacitor curve K1, the second capacitor curve K2, and the third capacitor curve K3, the leftmost points of the first circular arcs K11, K21, K31, respectively, can be considered to be the bulk resistance R0.

[0068] Furthermore, the lengths (resistive impedances) of the first arc lines K11, K21, and K31 are thought to be primarily due to the negative electrode reaction resistance R1, which is caused by the influence of the negative electrode 12. Similarly, the lengths of the second arc lines K12, K22, and K32 are thought to be primarily due to the positive electrode reaction resistance R2, which is caused by the influence of the positive electrode 11. Theoretically, the sum of the bulk resistance R0, the negative electrode reaction resistance R1, and the positive electrode reaction resistance R2 results in a resistance of 0.1 seconds.

[0069] The determination device 200 of the second embodiment provides the same effects as the first embodiment. The determination device 200 of the second embodiment further uses a bipolar degradation determination map 123, which includes a positive electrode degradation determination map 124 and a negative electrode degradation determination map 125, to determine the degradation of the lithium metal battery 10. Therefore, the degradation of the lithium metal battery 10 can be determined with greater accuracy.

[0070] In each of the above embodiments, the degradation state of the lithium metal battery 10 after removal from the vehicle M is determined. However, the degradation state of the lithium metal battery 10 may also be determined by connecting the determination devices 100 and 200 to the lithium metal battery 10 mounted on the vehicle M. In this case, an AC voltage is applied to the lithium metal battery 10 mounted on the vehicle M.

[0071] When applying voltage to the lithium metal battery 10 to determine its degradation state, either an AC power supply 20 may be used, or the voltage supplied by the charging equipment 80 shown in Figure 2 may be used. When using the voltage supplied by the charging equipment 80, the converter 60 may supply the AC voltage to the lithium metal battery 10 by reducing the AC voltage supplied to the charging equipment 80 while keeping it as AC.

[0072] Furthermore, for lithium metal batteries 10 that have been determined to be reusable, the remaining lifespan of the lithium metal battery 10 when it is reused may be estimated based on the measured thickness of the negative electrode 12. In this case, the remaining lifespan of the lithium metal battery 10 may be shorter the thicker the negative electrode 12 is. When there are lithium metal batteries 10 that have been determined to be reusable and multiple lithium metal batteries 10 are used in combination, lithium metal batteries 10 with similar remaining lifespans may be combined.

[0073] The embodiments described above can be expressed as follows. A storage medium that stores computer-readable instructions, A processor connected to the storage medium, The processor executes the computer-readable instructions to: Resistance information is obtained regarding the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode. Based on a first map showing the relationship between the thickness of the negative electrode and the resistance value, and the acquired resistance value information, the degradation state of the lithium metal battery is determined. A device for determining the degradation state of lithium metal batteries.

[0074] Although embodiments for carrying out the present invention have been described above using examples, the present invention is not limited in any way to these embodiments, and various modifications and substitutions can be made without departing from the spirit of the present invention. [Explanation of Symbols]

[0075] 10 Lithium metal batteries 11 Positive electrode 11A positive electrode current collector 11B Positive electrode active material layer 12 Negative electrode 12A negative electrode current collector 12B Negative electrode active material layer 13 Electrolytes 13S Separator 20 AC power supply 30 ammeter 40 Electrical equipment 50. Pre-deterioration measurement device 51 Voltage detector 52 Current detector 53 Arithmetic unit 54 Providing device 60 Converter 80 Charging equipment 100,200 Determination device (Deterioration state determination device) 110 Communications Department 120 Storage section 121 Degradation Judgment Map 122 Preliminary Judgment Map 123 Bipolar Degradation Judgment Map 124 Positive electrode degradation detection map 125 Negative electrode degradation judgment map 130 Processing Unit 131 Control Unit 132 Acquisition Department 133 Judgment section M Vehicle Q SEI layer R0 Bulk resistance R1 Negative electrode reaction resistance R2 Positive electrode reaction resistance

Claims

1. An acquisition unit that acquires resistance value information relating to the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode, The system comprises a first map showing the relationship between the thickness of the negative electrode and the resistance value, and a determination unit that determines the degradation state of the lithium metal battery based on the acquired resistance value information. The determination unit determines that the lithium metal battery is in a reusable state if the acquired resistance value is such that the thickness of the negative electrode is less than or equal to the first reference value. Based on a second map, which was prepared in advance and shows the relationship between the thickness of the positive electrode of the lithium metal battery and the resistance value, the degradation state of the lithium metal battery is determined. If the acquired resistance value is such that the thickness of the positive electrode is less than or equal to the second reference value, it is determined that the lithium metal battery is in a state where it can be reused. A device for determining the degradation state of lithium metal batteries.

2. The acquisition unit acquires the resistance value information based on the current value of the current discharged from the lithium metal battery. A device for determining the degradation state of a lithium metal battery according to claim 1.

3. The lithium metal battery is a lithium metal battery installed in a vehicle. The acquisition unit acquires the resistance value obtained by applying an AC voltage to the lithium metal battery removed from the vehicle. A device for determining the degradation state of a lithium metal battery according to claim 1 or 2.

4. The lithium metal battery is a lithium metal battery installed in a vehicle. The acquisition unit acquires the resistance value obtained by applying an AC voltage to the lithium metal battery installed in the vehicle. A device for determining the degradation state of a lithium metal battery according to claim 1.

5. The lithium metal battery is a lithium metal battery installed in a vehicle. The acquisition unit acquires the measurement result of the current discharged from the lithium metal battery mounted in the vehicle at a timing after a predetermined time of 0.001 seconds or more and 1.0 seconds or less has elapsed. The determination unit makes a preliminary determination of the degradation state of the lithium metal battery based on the acquired measurement results and a preliminary standard value that serves as a criterion for preliminaryly determining whether or not the lithium metal battery is unusable. A device for determining the degradation state of a lithium metal battery according to claim 1.

6. Computers Resistance information is obtained regarding the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode. Based on a first map showing the relationship between the thickness of the negative electrode and the resistance value, which was created in advance, and the acquired resistance value information, the degradation state of the lithium metal battery is determined. The aforementioned computer, If the acquired resistance value is such that the thickness of the negative electrode is less than or equal to the first reference value, it is determined that the lithium metal battery is in a state where it can be reused. Based on a second map, which was prepared in advance and shows the relationship between the thickness of the positive electrode of the lithium metal battery and the resistance value, the degradation state of the lithium metal battery is determined. If the acquired resistance value is such that the thickness of the positive electrode is less than or equal to the second reference value, it is determined that the lithium metal battery is in a state where it can be reused. A method for determining the degradation state of lithium metal batteries.

7. On the computer, Resistance information is obtained regarding the resistance value obtained by applying a voltage to a lithium metal battery having a lithium-containing negative electrode. The system determines the degradation state of the lithium metal battery based on a first map showing the relationship between the thickness of the negative electrode and the resistance value, and the acquired resistance value information. To the aforementioned computer, If the acquired resistance value is such that the thickness of the negative electrode is less than or equal to the first reference value, it is determined that the lithium metal battery is in a state where it can be reused. Based on a second map, which was prepared in advance and shows the relationship between the thickness of the positive electrode of the lithium metal battery and the resistance value, the degradation state of the lithium metal battery is determined. If the acquired resistance value is such that the thickness of the positive electrode is less than or equal to the second reference value, the system determines that the lithium metal battery is in a state where it can be reused. program.

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