Battery deterioration estimation device

Abstract

To enable accurate estimation of a degree of deterioration of a secondary battery with a metal lithium layer on an anode.SOLUTION: A battery deterioration estimation device comprises a current measurement part, a voltage measurement part, a calculation part, and an estimation part. The current measurement part measures a discharge current of a secondary battery at predetermined timing immediately after the start of discharge of the secondary battery. The voltage measurement part measures a drop voltage that is a difference between a voltage of the secondary battery before the start of discharge and a voltage of the secondary battery at the predetermined timing. The calculation part calculates an internal impedance of the secondary battery at the predetermined timing from the measured discharge current and the measured drop voltage. The estimation part estimates a degree of deterioration of the secondary battery from the calculated internal impedance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery degradation estimation device that estimates the degree of degradation of a secondary battery. [Background technology]

[0002] In recent years, electric vehicles such as EVs and HEVs have become more widespread from the viewpoint of reducing carbon dioxide emissions and reducing adverse effects on the global environment. Some secondary batteries mounted on electric vehicles and the like are configured as follows: That is, the secondary battery includes a positive electrode, a negative electrode having a metallic lithium layer, and an electrolyte provided between the positive electrode and the negative electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-87844 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such secondary batteries, an SEI film is formed and grows on the metallic lithium layer of the negative electrode as the battery is repeatedly charged and discharged. Note that "SEI" here stands for "Solid Electrolyte Interphase."

[0005] The present inventors have considered estimating the degree of deterioration of a secondary battery based on the growth degree of the SEI film. This is because the growth of the SEI film means a decrease in activity of metallic lithium in the negative electrode. Therefore, if the growth degree of the SEI film is known, the degree of decrease in activity of metallic lithium can be estimated, and the degree of deterioration of the secondary battery can be estimated.

[0006] As the SEI film grows, the electrical resistance of the SEI layer increases. When the SEI layer grows to a certain extent, the electrical resistance of the SEI film accounts for a large proportion of the internal impedance of the entire secondary battery. Therefore, the degree of growth of the SEI film can be estimated based on the internal impedance of the secondary battery. Based on the degree of growth, the degree of deterioration of the secondary battery can be estimated.

[0007] However, the present inventors have also focused on the following problem. During discharge of the secondary battery, dissolution and precipitation of metallic lithium are stabilized in the metallic lithium layer. That is, metallic lithium in the part of the metallic lithium layer on the negative electrode side from the SEI film is dissolved once, passes through the SEI film, and is then inserted into the positive electrode active material. In the process, the diffusion resistance accounts for a larger proportion of the internal impedance of the secondary battery. Therefore, the electrical resistance of the SEI film cannot be measured with high accuracy. Therefore, the growth degree of the SEI film cannot be estimated with high accuracy. As a result, the deterioration degree of the secondary battery cannot be estimated with high accuracy based on the growth degree.

[0008] The present invention has been made in view of the above circumstances, and has an object to make it possible to accurately estimate the degree of deterioration of a secondary battery having a metallic lithium layer in the negative electrode. [Means for solving the problem]

[0009] The present inventors have found that the degree of growth of the SEI film can be accurately estimated based on the internal impedance of a secondary battery immediately after the start of discharge, and have arrived at the present invention. The present invention is a battery degradation estimation device as described below in (1) to (6) and a battery degradation estimation method as described below in (7).

[0010] (1) A battery degradation estimation device that estimates a degree of degradation of a secondary battery including a positive electrode, a negative electrode having a metallic lithium layer, and an electrolyte provided between the positive electrode and the negative electrode, comprising: a current measuring unit that measures a discharge current of the secondary battery at a predetermined timing immediately after the secondary battery starts to discharge; a voltage measuring unit that measures a voltage drop that is a difference between a voltage of the secondary battery before the start of discharging and a voltage of the secondary battery at the predetermined timing; a calculation unit that calculates an internal impedance of the secondary battery at the predetermined timing from the measured discharge current and the measured voltage drop; an estimation unit that estimates a deterioration degree of the secondary battery from the calculated internal impedance; A battery deterioration estimation device comprising:

[0011] According to this configuration, the current measuring unit, the voltage measuring unit, and the calculating unit obtain the internal impedance of the secondary battery immediately after the start of discharge. Immediately after the start of discharge, the dissolution and precipitation of metallic lithium in the metallic lithium layer has not yet become steady. Therefore, in the entire secondary battery, the decrease in battery voltage due to diffusion resistance has not yet become full-scale. The estimating unit can accurately estimate the growth degree of the SEI film from the internal impedance of the secondary battery in that state. As a result, the deterioration degree of the secondary battery can be accurately estimated. As described above, according to this configuration, the deterioration degree of a secondary battery having a metallic lithium layer on the negative electrode can be accurately estimated.

[0012] (2) the predetermined timing is a timing when a predetermined time of 0.001 second or more and 1.0 second or less has elapsed since the start of discharge of the secondary battery; The battery deterioration estimation device according to (1) above.

[0013] If the discharge time is short, the influence of diffusion resistance and the like can be more effectively eliminated, but if the discharge time is too short, the influence of inductance of the harness and the like is easily caused, and accurate measurement cannot be performed. In this respect, according to the present configuration, the predetermined timing for measuring the internal impedance of the secondary battery is before 1.0 second has elapsed since the start of discharge, so the discharge time is sufficiently short and the influence of diffusion resistance and the like can be more effectively eliminated. In addition, since the predetermined timing is 0.001 or more seconds after the start of discharge of the secondary battery, the discharge time is not too short and the influence of inductance of the harness and the like is unlikely to be caused. From the above, the growth degree of the SEI film can be estimated with greater accuracy.

[0014] (3) a second current measurement unit that measures a second discharge current, which is a discharge current of the secondary battery at a second predetermined timing that is later than the predetermined timing; and a second voltage measurement unit that measures a second voltage drop that is a difference between a voltage of the secondary battery before the start of discharging and a voltage of the secondary battery at the second predetermined timing; a second calculation unit that calculates an internal impedance of the secondary battery at the second predetermined timing from the measured second discharge current and the measured second voltage drop; the estimation unit estimates a degree of deterioration of the secondary battery comprehensively from the calculated internal impedance at the predetermined timing and the calculated internal impedance at the second predetermined timing. The battery deterioration estimation device according to (1) or (2).

[0015] According to this configuration, the second current measuring unit, the second voltage measuring unit, and the second calculating unit obtain the internal impedance of the secondary battery at a second predetermined timing after the predetermined timing. It has been confirmed that the internal impedance at the second predetermined timing increases abruptly at the timing when the capacity of the secondary battery decreases abruptly. Therefore, by using the internal impedance at the second predetermined timing as well, the deterioration degree of the secondary battery can be estimated with higher accuracy.

[0016] (4) the second predetermined timing is a timing when a predetermined time of 3.0 seconds or more and 30 seconds or less has elapsed since the start of discharging of the secondary battery; The battery deterioration estimation device according to (3) above.

[0017] According to this configuration, the second predetermined timing for measuring the internal impedance of the secondary battery is set 3 seconds or more after the start of discharging of the secondary battery, so that a sufficient time is ensured for the internal impedance of the secondary battery to become stable. Also, the second predetermined timing is set 30 seconds or less after the start of discharging, so that it is possible to avoid wasting a lot of time on obtaining the internal impedance.

[0018] (5) The secondary battery and the battery degradation estimation device are mounted on a vehicle. The battery deterioration estimation device according to (1) or (2).

[0019] According to this configuration, the degree of deterioration of the secondary battery can be estimated inside the vehicle.

[0020] (6) A notification device is provided that notifies a driver of the vehicle that the secondary battery is degraded when the estimation unit determines that the secondary battery is degraded to a predetermined standard or more. The battery deterioration estimation device according to (5) above.

[0021] According to this configuration, when the secondary battery has deteriorated, the driver of the vehicle can quickly recognize this fact.

[0022] (7) A battery degradation estimation method for estimating degradation of a secondary battery including a positive electrode, a negative electrode having a metallic lithium layer, and an electrolyte provided between the positive electrode and the negative electrode, comprising: measuring a discharge current of the secondary battery at a predetermined timing immediately after the start of discharging the secondary battery; measuring a voltage drop that is a difference between a voltage of the secondary battery before the start of discharging and a voltage of the secondary battery at the predetermined timing; calculating an internal impedance of the secondary battery at the predetermined timing from the measured discharge current and the measured voltage drop; estimating a degree of deterioration of the secondary battery from the calculated internal impedance; Battery deterioration estimation method.

[0023] This method also provides the same effects as those obtained by the device in (1) above. Effect of the Invention

[0024] As described above, the device of (1) and the method of (7) can accurately estimate the degree of growth of the SEI film in a secondary battery having a metallic lithium layer on the negative electrode. Furthermore, the configurations of (2) to (6) that cite (1) above provide additional effects. [Brief description of the drawings]

[0025] [Figure 1] 1 is a configuration diagram showing a battery deterioration estimating device according to a first embodiment. [Diagram 2] FIG. 2 is a circuit diagram showing a circuit inside a vehicle. [Diagram 3] FIG. 4 is a circuit diagram showing a state during discharging. [Figure 4] FIG. 4 is a circuit diagram showing a state during charging. [Diagram 5] FIG. 1 is a circuit diagram showing a state in which an SEI film is formed. [Figure 6] FIG. 2 is a circuit diagram showing the internal impedance of a secondary battery. [Figure 7] 1 is a graph showing the relationship between the thickness of the SEI film and the impedance after 0.1 seconds. [Figure 8] 1 is a graph showing the relationship between the discharge time and the terminal voltage of a secondary battery. [Figure 9] 1 is a graph showing the relationship between the number of charge / discharge cycles and the impedance after 10 seconds, and the relationship between the number of charge / discharge cycles and the capacity of a secondary battery. [Figure 10] 1 is a graph showing the relationship between the number of charge / discharge cycles and impedance after 0.1 seconds. [Figure 11] FIG. 11 is a configuration diagram showing a battery deterioration estimating device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and can be appropriately modified and implemented without departing from the spirit of the present invention.

[0027] [First embodiment] As shown in Fig. 2, the battery degradation estimation device 50 of this embodiment is mounted on a vehicle 100. The vehicle 100 is further mounted with an electric device 70 and a secondary battery 30. The electric device 70 includes a PCU (power control unit) and the like. The secondary battery 30 supplies power to the electric device 70. The battery degradation estimation device 50 estimates the degree of degradation of the secondary battery 30.

[0028] The secondary battery 30 is a semi-solid battery and includes a positive electrode 38, a negative electrode 32, and an electrolyte 35. The positive electrode 38 includes a positive electrode current collector 38a and a positive electrode active material layer 38b. The positive electrode current collector 38a is made of a current collector foil such as aluminum. The positive electrode active material layer 38b is a layer of, for example, lithium cobalt oxide. The negative electrode 32 includes a negative electrode current collector 32a and a negative electrode active material layer 32b. The negative electrode current collector 32a is made of a current collector foil such as copper. The negative electrode active material layer 32b is a metallic lithium layer. The electrolyte 35 is a semi-solid electrolyte containing lithium ions Li+. The electrolyte 35 is divided into a positive electrode 38 side and a negative electrode 32 side by a separator 35s.

[0029] 3, during discharging when the secondary battery 30 supplies power to the electric device 70, lithium ions Li+ flow from the negative electrode active material layer 32b to the positive electrode 38 through a path passing through the separator 35s. At the same time, electrons e flow from the negative electrode 32 to the positive electrode 38 through a path passing through the circuit of the electric device 70. As a result, a current I flows from the positive electrode 38 to the negative electrode 32 within the vehicle 100, discharging the secondary battery 30. As the secondary battery 30 discharges, metallic lithium dissolves in the negative electrode active material layer 32b.

[0030] 4, when the secondary battery 30 is charged by a charging power source 200 external to the vehicle 100, lithium ions Li+ flow from the positive electrode active material layer 38b to the negative electrode 32 through a path passing through the separator 35s. At the same time, electrons e flow from the positive electrode 38 to the negative electrode 32 through a path passing through the charging power source 200. As a result, a current I flows from the negative electrode 32 to the positive electrode 38, charging the secondary battery 30. As the battery is charged, metallic lithium is precipitated in the negative electrode active material layer 32b.

[0031] By repeating such charging and discharging, the SEI film 32g shown in Fig. 5 is formed and grows on the negative electrode active material layer 32b. That is, the thickness Tg of the SEI film 32g increases.

[0032] Hereinafter, the portion of the negative electrode active material layer 32b closer to the negative electrode current collector 32a than the SEI film 32g will be referred to as an "excess layer 32b1," and the portion of the negative electrode active material layer 32b closer to the positive electrode 38 than the SEI film 32g will be referred to as a "precipitation layer 32b2."

[0033] Next, the principle of the battery degradation estimation device 50 will be described. The battery degradation estimation device 50 judges the degree of degradation of the secondary battery 30 based on the growth degree of the SEI film 32g. This is because the growth of the SEI film 32g means a decrease in activity of metallic lithium in the negative electrode active material layer 32b. Therefore, if the growth state of the SEI film 32g is known, the degree of decrease in activity of metallic lithium can be estimated, and the degree of degradation of the secondary battery 30 can be estimated.

[0034] Hereinafter, as shown in Fig. 6, the electrical resistance of the SEI film 32g will be referred to as "SEI film resistances R3, R4." The SEI film resistances R3, R4 increase as the SEI film 32g grows. When the SEI film 32g has grown to a certain extent, the electrical resistance of the SEI film 32g accounts for a large proportion of the internal impedance Z of the entire secondary battery 30.

[0035] Specifically, the internal impedance Z of the secondary battery 30 includes, for example, as shown in FIG. 6, in addition to the SEI film resistances R3, R4, negative electrode interlayer resistances R1, R2, separator resistance R5, positive electrode internal resistances R6, R7, positive electrode interlayer resistances R8, R9, etc.

[0036] The negative electrode interlayer resistances R1 and R2 are the conduction resistance of electrons e between the negative electrode current collector 32a and the negative electrode active material layer 32b. The SEI film resistances R3 and R4 are the conduction resistance of electrons e in the SEI film 32g. The separator resistance R5 is the conduction resistance of lithium ions Li+ in the separator 35s. The positive electrode internal resistances R6 and R7 are the conduction resistance of lithium ions Li+ in the positive electrode active material layer 38b. The positive electrode interlayer resistances R8 and R9 are the conduction resistance of electrons e between the positive electrode current collector 38a and the positive electrode active material layer 38b. As the SEI film 32g grows, the proportion of the SEI film resistances R3 and R4 in the internal impedance Z of the entire secondary battery 30 including these elements increases.

[0037] Therefore, the battery degradation estimation device 50 predicts the degradation state of the secondary battery 30 based on the internal impedance Z of the secondary battery 30.

[0038] However, there are also the following problems. When the secondary battery 30 is discharged, dissolution and precipitation of metallic lithium in the negative electrode active material layer 32b becomes steady. That is, in the negative electrode active material layer 32b shown in FIG. 5, metallic lithium in the surplus layer 32b1 is dissolved once, passes through the SEI film 32g, and then is inserted into the positive electrode active material layer 38b. In this process, the diffusion resistance accounts for a larger proportion of the internal impedance Z of the secondary battery 30. Therefore, the SEI film resistances R3 and R4 shown in FIG. 6 cannot be measured with high accuracy. Therefore, the growth degree of the SEI film 32g shown in FIG. 5 cannot be estimated with high accuracy. As a result, the deterioration degree of the secondary battery 30 cannot be estimated with high accuracy.

[0039] For this reason, a battery deterioration estimation device 50 shown in Fig. 5 estimates the degree of deterioration of the secondary battery 30 based on the internal impedance Z of the secondary battery 30 at a predetermined timing immediately after the secondary battery 30 starts discharging. This is because the dissolution and precipitation of metallic lithium described above has not yet become steady immediately after the secondary battery 30 starts discharging. Specifically, the "predetermined timing" here is the timing 0.1 seconds after the secondary battery 30 starts discharging. Hereinafter, this timing will be referred to as the "timing 0.1 seconds later."

[0040] In the following, the discharge current of the secondary battery 30 at 0.1 seconds is referred to as "current Ia after 0.1 seconds." As shown in FIG. 8, the difference between the terminal voltage Vo of the secondary battery 30 before the start of discharge and the terminal voltage V of the secondary battery 30 at 0.1 seconds is referred to as "voltage drop ΔVa after 0.1 seconds." As shown in FIG. 7, the internal impedance Z of the secondary battery 30 at 0.1 seconds is referred to as "impedance Za after 0.1 seconds." As shown in FIG. 7, the impedance Za after 0.1 seconds increases with an increase in the thickness Tg of the SEI film.

[0041] Next, a description will be given of the configuration of the battery degradation estimation device 50 shown in Fig. 3. The battery degradation estimation device 50 comprises a voltage detector 51, a current detector 52, a calculation device 57, and a notification device 59.

[0042] The voltage detector 51 detects the terminal voltage V of the secondary battery 30. The current detector 52 detects the current I flowing from the positive electrode 38 side to the negative electrode 32 side of the secondary battery 30. Thus, the discharge current of the secondary battery 30 is detected when the secondary battery 30 is discharged. The calculation device 57 estimates the degree of growth of the SEI film 32g in the metallic lithium layer based on the discharge current and the terminal voltage V, and estimates the degree of deterioration of the secondary battery 30.

[0043] Specifically, as shown in FIG. 1, the arithmetic device 57 includes a voltage measuring unit 53, a current measuring unit 54, a calculation unit 55, and an estimation unit 56.

[0044] The current measuring unit 54 measures the current Ia after 0.1 seconds based on information from the current detector 52. The voltage measuring unit 53 measures the voltage drop ΔVa after 0.1 seconds based on information from the voltage detector 51.

[0045] The calculation unit 55 calculates the impedance Za after 0.1 seconds from the voltage drop ΔVa after 0.1 seconds measured by the voltage measurement unit 53 and the current Ia after 0.1 seconds measured by the current measurement unit 54. That is, the calculation unit 55 calculates the impedance Za after 0.1 seconds as the value (ΔVa / Ia) obtained by dividing the voltage drop ΔVa after 0.1 seconds by the current Ia after 0.1 seconds.

[0046] The estimation unit 56 estimates the growth degree of the SEI film 32g in the negative electrode active material layer 32b shown in Fig. 5 from the impedance Za after 0.1 seconds calculated by the calculation unit 55. Specifically, for example, the estimation unit 56 has a table showing the relationship between information based on the impedance Za after 0.1 seconds and the growth degree of the SEI film 32g. The growth degree of the SEI film 32g is estimated based on the table.

[0047] More specifically, the inventors' tests confirmed that the impedance Za after 0.1 seconds gradually increases with an increase in the number of charge / discharge cycles N, as shown in Fig. 10. Furthermore, it was confirmed that the rate of increase in the impedance Za after 0.1 seconds, that is, the slope of "Za" shown in Fig. 10, increases sharply at a certain number of cycles Nt. At the certain number of cycles Nt, the capacity Sh of the secondary battery 30 decreases sharply, as shown in Fig. 9.

[0048] Therefore, the estimation unit 56 determines that the growth degree of the SEI film 32g has reached a predetermined standard at the point where the slope of the "Za" increases rapidly. Specifically, for example, the information based on the impedance Za after 0.1 seconds in the above-mentioned table includes one or more of the "Za", the slope of the "Za", and the increasing speed of the slope of the "Za". The estimation unit 56 estimates the growth degree of the SEI film 32g from the information based on the impedance Za after 0.1 seconds and the above-mentioned table. From the growth degree, the estimation unit 56 determines whether the SEI film 32g has grown to a predetermined standard or more. Then, on the condition that it is determined that the SEI film 32g has grown to the predetermined standard or more, the estimation unit 56 determines that the secondary battery 30 has deteriorated to a predetermined standard or more, and transmits a notification signal to the notification device 59.

[0049] When the notification device 59 shown in Fig. 1 receives the notification signal, it notifies the driver of the vehicle 100 shown in Fig. 2 that the secondary battery 30 has deteriorated. The notification may be a visual notification using, for example, a lamp or a display, an audio notification using, for example, a warning sound or an announcement, or both.

[0050] The configuration and effects of this embodiment are summarized below.

[0051] According to this embodiment, as shown in FIG. 1, the voltage detector 51, the current detector 52, the voltage measuring unit 53, the current measuring unit 54, and the calculation unit 55 cooperate to acquire the impedance Za after 0.1 seconds. At the timing of 0.1 seconds after the acquisition of the impedance Za after 0.1 seconds, the dissolution and precipitation of the metallic lithium described above has not yet become steady in the negative electrode active material layer 32b shown in FIG. 5. Therefore, in the entire secondary battery 30, the decrease in the terminal voltage V due to the diffusion resistance has not yet become full-scale. The estimation unit 56 can accurately estimate the growth degree of the SEI film 32g shown in FIG. 5 from the internal impedance Z of the secondary battery 30 in that state. As a result, the deterioration degree of the secondary battery 30 can be accurately estimated.

[0052] Moreover, the secondary battery 30 and the battery deterioration estimation device 50 are mounted on the vehicle 100. Therefore, the degree of deterioration of the secondary battery 30 can be estimated inside the vehicle 100.

[0053] Moreover, the notification device 59 notifies the driver of the vehicle 100 that the secondary battery 30 has deteriorated, on condition that the estimation unit 56 has determined that the secondary battery 30 has deteriorated to a predetermined standard or more. Therefore, when the secondary battery 30 has deteriorated, the driver of the vehicle can quickly recognize the fact.

[0054] The use of the battery deterioration estimation device 50 described above corresponds to carrying out a battery deterioration estimation method.

[0055] [Second embodiment] Next, a second embodiment will be described with reference to Fig. 11. The present embodiment will be described based on the first embodiment, focusing on differences from the first embodiment, and descriptions of the same or similar aspects to the first embodiment will be omitted as appropriate.

[0056] The battery degradation estimation device 50 of this embodiment estimates the degree of degradation of the secondary battery 30 based additionally on the internal impedance Z of the secondary battery 30 at a second predetermined timing after the timing of 0.1 seconds. Specifically, the "second predetermined timing" here is the timing 10 seconds after the start of discharging of the secondary battery 30. Hereinafter, this timing is referred to as the "timing after 10 seconds."

[0057] In the following, the discharge current of the secondary battery 30 at the timing 10 seconds later is referred to as the "current Ib after 10 seconds." As shown in FIG. 8, the difference between the terminal voltage Vo of the secondary battery 30 before the start of discharge and the terminal voltage V of the secondary battery 30 at the timing 10 seconds later is referred to as the "voltage drop ΔVb after 10 seconds." The internal impedance Z of the secondary battery 30 at the timing 10 seconds later is referred to as the "impedance Zb after 10 seconds." The "current Ib after 10 seconds" may be read as the "second discharge current." The "voltage drop ΔVb after 10 seconds" may be read as the "second voltage drop."

[0058] 11, the arithmetic device 57 further includes a second voltage measurement unit 53b, a second current measurement unit 54b, and a second calculation unit 55b in addition to the first embodiment. The second voltage measurement unit 53b measures a voltage drop ΔVb after 10 seconds based on information from the voltage detector 51. The second current measurement unit 54b measures a current Ib after 10 seconds based on information from the current detector 52.

[0059] The second calculation unit 55b calculates the impedance Zb after 10 seconds from the voltage drop ΔVb after 10 seconds measured by the second voltage measurement unit 53b and the current Ib after 10 seconds measured by the second current measurement unit 54b. That is, the second calculation unit 55b calculates the impedance Zb after 10 seconds as the value (ΔVb / Ib) obtained by dividing the voltage drop ΔVb after 10 seconds by the current Ib after 10 seconds.

[0060] The estimation unit 56 estimates the deterioration degree of the secondary battery 30 comprehensively from the impedance Za after 0.1 seconds calculated by the calculation unit 55 and the impedance Zb after 10 seconds calculated by the second calculation unit 55b. Specifically, for example, the estimation unit 56 has a table showing the relationship between multi-dimensional information including information based on the impedance Za after 0.1 seconds and information based on the impedance Zb after 10 seconds and the growth degree of the SEI film 32g. The growth degree of the SEI film 32g is estimated based on the table.

[0061] More specifically, as shown in Fig. 9, the inventors have confirmed through their tests that the 10-second impedance Zb increases with an increase in the number of charge / discharge cycles N. It has also been confirmed that the rate of increase in the 10-second impedance Zb, that is, the slope of "Zb" in Fig. 9, increases sharply at a predetermined number of cycles Nt. This is probably because the surplus layer 32b1 shown in Fig. 5 is depleted at the predetermined number of cycles Nt. As shown in Fig. 9, the capacity Sh of the secondary battery 30 also decreases sharply at the predetermined number of cycles Nt.

[0062] Therefore, the estimation unit 56 estimates the degree of deterioration of the secondary battery 30 based on the point where the slope of the "Zb" increases abruptly. Specifically, for example, the information based on the impedance Za after 10 seconds in the above-mentioned table includes one or more of the "Zb", the slope of the "Zb", and the increasing speed of the slope of the "Zb". The estimation unit 56 estimates the degree of deterioration of the secondary battery 30 from the above-mentioned multi-dimensional information including the information based on the impedance Za after 10 seconds and the above-mentioned table. From the degree of deterioration, it is determined whether the secondary battery 30 has deteriorated to a predetermined standard or more.

[0063] 11, the estimation unit 56 estimates the degree of deterioration of the secondary battery 30 comprehensively from the impedance Za after 0.1 seconds and the impedance Zb after 10 seconds, thereby making it possible to estimate the degree of deterioration with higher accuracy.

[0064] [Other embodiments] The above-described embodiment can be modified, for example, as follows. The electrolyte 35 of the secondary battery 30 shown in Fig. 2 may be a liquid electrolyte or an all-solid electrolyte instead of a semi-solid electrolyte. In other words, the secondary battery 30 may be a so-called liquid LiB or an all-solid battery.

[0065] The above-mentioned predetermined timing may be a timing other than the timing 0.1 after. However, even in that case, the predetermined timing is preferably a timing when a predetermined time of 0.001 seconds or more and 1.0 seconds or less has elapsed since the start of discharge of the secondary battery 30. This is because if the discharge time is short, the influence of diffusion resistance and the like can be more effectively eliminated, but if the discharge time is too short, it is easily affected by the inductance of the harness and the like, and accurate measurement cannot be performed. In this respect, if the predetermined timing for measuring the internal impedance Z of the secondary battery 30 is before 1.0 seconds has elapsed since the start of discharge, the discharge time is sufficiently short, so that the influence of diffusion resistance and the like can be more effectively eliminated. Also, if the timing is 0.001 seconds or more after the start of discharge of the secondary battery 30, the discharge time is not too short, and it is difficult to be affected by the inductance of the harness and the like.

[0066] The specified timing is preferably a timing when a specified time of 0.5 seconds or less has elapsed since the start of the discharge, in that it can be measured more reliably before the discharge reaches a steady state, and is even more preferably a timing when a specified time of 0.2 seconds or less has elapsed since the start of the discharge.

[0067] In the second embodiment, the second predetermined timing may be a timing other than 10 seconds later. However, even in this case, the second predetermined timing is preferably a timing at which a predetermined time of 3 seconds or more and 30 seconds or less has elapsed since the start of discharge of the secondary battery 30. This is because, if the second predetermined timing is 3 seconds or more after the start of discharge, a sufficient time can be ensured until the internal impedance Z of the secondary battery 30 becomes steady. Also, if the second predetermined timing is obtained before 30 seconds have elapsed since the start of discharge, it is possible to avoid wasting a lot of time on obtaining the internal impedance Z. [Explanation of symbols]

[0068] 30 Secondary battery 32 Negative electrode 32b Negative electrode active material layer (metallic lithium layer) 35 Electrolytes 38 Positive electrode 50 Battery Deterioration Estimation Device 53 Voltage measurement section 53b Second voltage measuring unit 54 Current measurement section 54b 2nd current measurement section 55 Calculation section 55b Second calculation section 56 Estimation part 59 Notification device 100 vehicles Ia Current after 0.1 seconds (discharge current of secondary battery at a given timing) Ib Current after 10 seconds (second discharge current) V Terminal voltage of secondary battery (voltage of secondary battery) ΔVa: Voltage drop after 0.1 seconds (voltage drop of secondary battery at a specified timing) ΔVb Voltage drop after 10 seconds (second voltage drop) Z Internal Impedance Za Impedance after 0.1 seconds (internal impedance at a given timing) Zb Impedance after 10 seconds (internal impedance at the second specified timing)

Claims

1. A battery degradation estimation device that estimates a degree of degradation of a secondary battery including a positive electrode, a negative electrode having a metallic lithium layer, and an electrolyte provided between the positive electrode and the negative electrode, a current measuring unit that measures a discharge current of the secondary battery at a predetermined timing immediately after the secondary battery starts to discharge; a voltage measuring unit that measures a voltage drop that is a difference between a voltage of the secondary battery before the start of discharging and a voltage of the secondary battery at the predetermined timing; a calculation unit that calculates an internal impedance of the secondary battery at the predetermined timing from the measured discharge current and the measured voltage drop; an estimation unit that estimates a deterioration degree of the secondary battery from the calculated internal impedance; A battery deterioration estimation device comprising:

2. the predetermined timing is a timing when a predetermined time of 0.001 second or more and 1.0 second or less has elapsed since the start of discharging of the secondary battery, The battery deterioration estimating device according to claim 1 .

3. a second current measurement unit that measures a second discharge current, which is a discharge current of the secondary battery at a second predetermined timing that is later than the predetermined timing; a second voltage measurement unit that measures a second voltage drop that is a difference between a voltage of the secondary battery before a discharge starts and a voltage of the secondary battery at the second predetermined timing; a second calculation unit that calculates an internal impedance of the secondary battery at the second predetermined timing from the measured second discharge current and the measured second voltage drop; the estimation unit estimates a degree of deterioration of the secondary battery comprehensively from the calculated internal impedance at the predetermined timing and the calculated internal impedance at the second predetermined timing. The battery deterioration estimating device according to claim 1 or 2.

4. the second predetermined timing is a timing when a predetermined time of 3.0 seconds or more and 30 seconds or less has elapsed since the start of discharging of the secondary battery; The battery deterioration estimating device according to claim 3 .

5. The secondary battery and the battery deterioration estimation device are mounted on a vehicle. The battery deterioration estimating device according to claim 1 or 2.

6. a notification device that notifies a driver of the vehicle that the secondary battery is degraded when the estimation unit determines that the secondary battery is degraded to a predetermined standard or more; The battery deterioration estimating device according to claim 5 .

7. A battery degradation estimation method for estimating degradation of a secondary battery including a positive electrode, a negative electrode having a metallic lithium layer, and an electrolyte provided between the positive electrode and the negative electrode, comprising: measuring a discharge current of the secondary battery at a predetermined timing immediately after the start of discharging the secondary battery; measuring a voltage drop that is a difference between a voltage of the secondary battery before the start of discharging and a voltage of the secondary battery at the predetermined timing; calculating an internal impedance of the secondary battery at the predetermined timing from the measured discharge current and the measured voltage drop; estimating a degree of deterioration of the secondary battery from the calculated internal impedance; Battery deterioration estimation method.

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