WO2016006359A1

WO2016006359A1 - Sealed secondary battery deterioration diagnosis method and deterioration diagnosis system

Info

Publication number: WO2016006359A1
Application number: PCT/JP2015/065539
Authority: WO
Inventors: 福田　武司; 南方　伸之
Original assignee: 東洋ゴム工業株式会社
Priority date: 2014-07-10
Filing date: 2015-05-29
Publication date: 2016-01-14

Abstract

A sealed secondary battery deterioration diagnosis method comprising: a step for detecting deformation of the sealed secondary battery to determine a first curved line indicating the relationship between a discharge capacity from the fully charged state or a charge capacity to the fully charged state and the detected deformation amount of the sealed secondary battery; a step for determining a second curved line L2 indicating the relationship between said charge/discharge capacity and the slope of the first curved line; a step for calculating a charge/discharge capacity Qc between stage change points P1, P2 appearing as minimum values on the second curved line L2; and a step for calculating the maintenance rate of an active material on the basis of a ratio Qc/Qs of the charge/discharge capacity Qc with respect to a charge/discharge capacity Qs between stage change points Ps1, Ps2 in a predetermined reference state.

Description

Degradation diagnosis method and degradation diagnosis system for sealed secondary battery

The present invention relates to a method and system for diagnosing deterioration of a sealed secondary battery.

In recent years, sealed secondary batteries represented by lithium ion secondary batteries (hereinafter sometimes referred to simply as “secondary batteries”) are not only mobile devices such as mobile phones and laptop computers, but also electric vehicles and hybrids. It is also used as a power source for electric vehicles such as cars. The secondary battery deteriorates by repeating charge and discharge, and it becomes difficult to accurately grasp the remaining capacity as the deterioration progresses.

In Patent Document 1, a change in battery voltage per predetermined time is sequentially measured while performing constant current charging or constant current discharging of a secondary battery, and based on the time when the change in the battery voltage is equal to or less than a predetermined value, A method for calculating the deterioration rate of the secondary battery is described. However, since the battery voltage per predetermined time changes depending on the charge / discharge history up to the time of measurement, it is used in an environment where the battery is installed in an electric vehicle that is used repeatedly while charging / discharging, for example, charging / discharging frequently. Not suitable for use in

Patent Document 2 describes a method for calculating a charge capacity by fully charging a battery once it is completely discharged and integrating the amount of current for charging at that time. However, since it is rare that a battery is completely discharged in actual use, it is suitable for use in applications where charging and discharging are repeated, for example, in an environment mounted on an electric vehicle that frequently charges and discharges. Absent.

In Patent Document 3, the voltage and internal pressure of the secondary battery are detected, the relational data between the voltage and the internal pressure of the secondary battery that is not deteriorated, and the relational data between the internal pressure of the secondary battery and the battery capacity. Describes a method of calculating deterioration of a secondary battery using However, since the deterioration mechanism may differ depending on the environment and conditions in which the secondary battery is used, it is necessary to prepare various patterns of relational data and it is difficult to determine which pattern is applicable.

JP 2002-340997 A JP 2008-278624 A JP2013-92398A

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and system capable of easily and accurately diagnosing deterioration of a sealed secondary battery even in applications where charging and discharging are repeated. It is to provide.

The degradation diagnosis method for a sealed secondary battery according to the present invention detects deformation of the sealed secondary battery, discharge capacity from a fully charged state or a charged capacity up to a fully charged state, and the detected sealed secondary battery. A step of obtaining a first curve representing a relationship with the deformation amount of the secondary battery, a step of obtaining a second curve representing the relationship between the charge / discharge capacity and the slope of the first curve, and an extreme value in the second curve. Based on the step of calculating the charge / discharge capacity Qc between the stage change points that appear and the ratio Qc / Qs of the charge / discharge capacity Qc to the charge / discharge capacity Qs between the stage change points in a predetermined reference state The step of calculating is included.

The extreme value appearing in the second curve is due to the stage change of the electrode, and when the active material is deactivated, the amount of active material contributing to charge / discharge is reduced, so the charge / discharge between the stage change points The capacity Qc is reduced. Therefore, by using the ratio Qc / Qs between the charge / discharge capacity Qs and the charge / discharge capacity Qc in the reference state as an index, the extent to which the active material contributing to charge / discharge is maintained, that is, the maintenance ratio of the active material is determined. It can be calculated. The first curve, which is the origin of the second curve, is the relationship between the discharge capacity from the fully charged state or the charge capacity until the fully charged state and the deformation amount of the secondary battery. There are many occasions when the battery is fully charged even in a repetitive environment. Therefore, with this method, deterioration of the sealed secondary battery can be diagnosed simply and with high accuracy even in applications where charging and discharging are repeated.

In the deterioration diagnosis method, the step of correcting the second curve using the maintenance rate so that the charge / discharge capacity Qc is the same as the charge / discharge capacity Qs, and the corrected second curve It is preferable to include a step of calculating a capacity balance deviation amount due to a side reaction based on a charge / discharge capacity difference between the stage change point at and a stage change point corresponding to the predetermined reference state.

By correcting the second curve in this way, a second curve is obtained assuming that there is no deactivation of the active material grasped by the maintenance rate. The charge / discharge capacity difference seen between the corrected second curve and the reference state is a result of a deviation in the capacity balance between positive and negative and the negative electrode. This is caused by the difference between the reaction amount and the side reaction amount at the negative electrode. Therefore, based on this charge / discharge capacity difference, the capacity balance deviation amount due to the side reaction can be calculated, and deterioration of the sealed secondary battery can be diagnosed with higher accuracy. Further, the amount of capacity balance deviation due to this side reaction can be used for predicting the remaining capacity of the sealed secondary battery together with the maintenance rate of the active material.

In the deterioration diagnosis method, the charge / discharge capacity calculated based on the peak width appearing in the second curve is more than the charge / discharge capacity calculated based on the corresponding peak width in a predetermined reference state. In the case of being large, it may include a step of determining a degradation mode due to expansion of the reaction distribution. Thereby, expansion of the reaction distribution can be easily detected.

When it is determined that the degradation mode is due to the expansion of the reaction distribution, the step of charging at a constant current within a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity at the rising edge of the peak appearing in the second curve. It is preferable to include. As a result, inconveniences such as precipitation of lithium metal can be avoided, and it is not necessary to completely discharge the battery.

In the degradation diagnosis method for a sealed secondary battery according to the present invention, a polymer matrix layer is attached to the sealed secondary battery, and the polymer matrix layer is exposed to an external field according to deformation of the polymer matrix layer. It is preferable that a change-providing filler is contained in a dispersed manner, and that the deformation of the sealed secondary battery is detected by detecting the change in the external field according to the deformation of the polymer matrix layer. Thereby, deformation of the sealed secondary battery can be detected with high sensitivity, and deterioration of the sealed secondary battery can be diagnosed with high accuracy.

In the above, it is preferable that the polymer matrix layer contains a magnetic filler as the filler, and the deformation of the sealed secondary battery is detected by detecting a change in the magnetic field as the external field. Thereby, the change of the magnetic field accompanying the deformation of the polymer matrix layer can be detected without wiring. In addition, since a Hall element having a wide sensitivity region can be used, highly sensitive detection can be performed over a wider range.

Further, the sealed secondary battery deterioration diagnosis system according to the present invention includes a detection sensor for detecting deformation of the sealed secondary battery, a discharge capacity from a fully charged state or a charged capacity up to a fully charged state, A first curve representing the relationship between the deformation amount of the sealed secondary battery detected by the detection sensor and a second curve representing the relationship between the charge / discharge capacity and the slope of the first curve are obtained, and the second curve The charge / discharge capacity Qc between the stage change points appearing as extreme values in the curve is calculated, and based on the ratio Qc / Qs of the charge / discharge capacity Qc to the charge / discharge capacity Qs between the stage change points in a predetermined reference state, And a control device for calculating a maintenance rate.

The extreme value appearing in the second curve is due to the stage change of the electrode, and when the active material is deactivated, the amount of active material contributing to charge / discharge is reduced, so the charge / discharge between the stage change points The capacity Qc is reduced. Therefore, by using the ratio Qc / Qs between the charge / discharge capacity Qs and the charge / discharge capacity Qc in the reference state as an index, the extent to which the active material contributing to charge / discharge is maintained, that is, the maintenance ratio of the active material is determined. It can be calculated. The first curve, which is the origin of the second curve, is the relationship between the discharge capacity from the fully charged state or the charge capacity until the fully charged state and the deformation amount of the secondary battery. There are many occasions when the battery is fully charged even in a repetitive environment. Therefore, this system can easily and accurately diagnose the deterioration of the sealed secondary battery even in applications where charging and discharging are repeated.

In the above degradation diagnosis system, the control device corrects the second curve using the maintenance rate so that the charge / discharge capacity Qc is the same as the charge / discharge capacity Qs, and after the correction, It is preferable to calculate the capacity balance deviation amount due to the side reaction based on the charge / discharge capacity difference between the stage change point in the second curve and the corresponding stage change point in a predetermined reference state.

In the above deterioration diagnosis system, the charge / discharge capacity calculated based on the peak width appearing in the second curve is more than the charge / discharge capacity calculated based on the corresponding peak width in a predetermined reference state. When it is large, it may be determined as a deterioration mode due to expansion of the reaction distribution. Thereby, expansion of the reaction distribution can be easily detected.

When it is determined that the deterioration mode is due to the expansion of the reaction distribution, a battery that performs constant current charging within a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity at the rising edge of the peak appearing in the second curve. preferable. As a result, inconveniences such as precipitation of lithium metal can be avoided, and it is not necessary to completely discharge the battery.

In the degradation diagnosis system for a sealed secondary battery according to the present invention, the detection sensor includes a polymer matrix layer attached to the sealed secondary battery, and a detection unit, and the polymer matrix layer includes It is preferable that a filler that changes the external field according to the deformation of the polymer matrix layer is dispersed and contained, and the detection unit detects the change of the external field. Thereby, deformation of the sealed secondary battery can be detected with high sensitivity, and deterioration of the sealed secondary battery can be diagnosed with high accuracy.

In the above, it is preferable that the polymer matrix layer contains a magnetic filler as the filler, and the detection unit detects a change in the magnetic field as the external field. Thereby, the change of the magnetic field accompanying the deformation of the polymer matrix layer can be detected without wiring. In addition, since a Hall element having a wide sensitivity region can be used as the detection unit, highly sensitive detection can be performed over a wider range.

The block diagram which shows an example of the system for performing the deterioration diagnostic method which concerns on this invention (A) perspective view and (b) AA cross-sectional view schematically showing a sealed secondary battery (A) perspective view and (b) BB sectional view schematically showing a sealed secondary battery Graph showing the relationship between the discharge capacity from the fully charged state and the amount of deformation of the detected secondary battery Graph showing the relationship between the discharge capacity from the fully charged state and the slope of the first curve Graph showing the relationship between the discharge capacity from the fully charged state and the slope of the first curve A graph showing the relationship between the charge capacity up to the fully charged state and the slope of the first curve A graph showing the relationship between the charge capacity up to the fully charged state and the slope of the first curve

Hereinafter, embodiments of the present invention will be described.

FIG. 1 shows a system mounted on an electric vehicle such as an electric vehicle or a hybrid vehicle. This system includes a battery module 1 in which an assembled battery composed of a plurality of sealed secondary batteries 2 is housed in a casing. In the present embodiment, four secondary batteries 2 are connected in two parallel two series, but the number of batteries and the connection form are not limited to this. Although only one battery module 1 is shown in FIG. 1, the battery pack 1 actually includes a plurality of battery modules 1. In the battery pack, a plurality of battery modules 1 are connected in series, and they are housed in a casing together with various devices such as a controller. The casing of the battery pack is formed in a shape suitable for in-vehicle use, for example, a shape that matches the underfloor shape of the vehicle.

The secondary battery 2 shown in FIG. 2 is configured as a cell (single cell) in which an electrode group 22 is accommodated in a sealed outer casing 21. The electrode group 22 has a structure in which a positive electrode 23 and a negative electrode 24 are laminated or wound through a separator 25 therebetween, and the separator 25 holds an electrolytic solution. The secondary battery 2 of the present embodiment is a laminated battery using a laminated film such as an aluminum laminated foil as the outer package 21, and is specifically a laminated lithium ion secondary battery having a capacity of 1.44 Ah. The secondary battery 2 is formed in a thin rectangular parallelepiped shape as a whole, and the X, Y, and Z directions correspond to the length direction, the width direction, and the thickness direction of the secondary battery 2, respectively. The Z direction is also the thickness direction of the positive electrode 23 and the negative electrode 24.

The secondary battery 2 is provided with a detection sensor 5 that detects deformation of the secondary battery 2. The detection sensor 5 includes a polymer matrix layer 3 attached to the secondary battery 2 and a detection unit 4. The polymer matrix layer 3 contains a filler that disperses the external field according to deformation of the polymer matrix layer 3 in a dispersed manner. The polymer matrix layer 3 of the present embodiment is formed in a sheet shape from an elastomer material that can be flexibly deformed. The detector 4 detects a change in the external field. When the secondary battery 2 swells and deforms, the polymer matrix layer 3 is deformed accordingly, and a change in the external field accompanying the deformation of the polymer matrix layer 3 is detected by the detection unit 4. In this way, deformation of the secondary battery 1 can be detected with high sensitivity.

In the example of FIG. 2, since the polymer matrix layer 3 is attached to the outer package 21 of the secondary battery 2, the polymer matrix layer 3 can be deformed according to deformation (mainly swelling) of the outer package 21. it can. On the other hand, as shown in FIG. 3, the polymer matrix layer 3 may be attached to the electrode group 22 of the secondary battery 2, and according to such a configuration, the polymer is changed according to deformation (mainly swelling) of the electrode group 22. The matrix layer 3 can be deformed. The deformation of the secondary battery 1 to be detected may be any deformation of the outer package 21 and the electrode group 22.

The signal detected by the detection sensor 5 is transmitted to the control device 6, whereby information relating to the deformation of the secondary battery 2 is supplied to the control device 6. The control device 6 performs deterioration diagnosis of the secondary battery 2 using the information, specifically based on processing including the following steps 1 to 4 and more preferably including

steps

5 and 6. In addition, although the following example demonstrates the behavior when it discharges from a full charge state to arbitrary discharge states, it is not limited to this.

First, the deformation of the secondary battery 2 is detected, and a first curve representing the relationship between the discharge capacity from the fully charged state and the detected deformation amount of the secondary battery 2 is obtained (step 1). The graph of FIG. 4 shows the first curve L1 obtained in the secondary battery 2 after 500 cycles of the charge / discharge process. In the charging / discharging process, the secondary battery 2 is placed in a constant temperature bath at 25 ° C., left still for 120 minutes, charged at a constant current of 4.3 V with a charging current of 1.44 A, reaches 4.3 V, and then reaches 0.00 V. A constant voltage charge was performed until the current value decreased to 07 A, and then an open circuit state was maintained for 10 minutes, and a constant current discharge was performed to 3.0 V with a current of 1.44 A. In addition, in the unused secondary battery 2 which did not deteriorate, the discharge capacity from the fully charged state to the fully discharged state was 1440 mAh.

4, the horizontal axis is the discharge capacity Q with the origin at the fully charged state, and the vertical axis is the detected deformation amount T of the secondary battery 2. As the discharge capacity Q from the fully charged state increases, the deformation amount T of the secondary battery 2 decreases. This is because, in the charged secondary battery 2, the electrode group 22 swells (hereinafter sometimes referred to as “electrode swell”) due to the volume change of the active material, and the electrode group 22 swells along with the discharge. This is because becomes smaller. A curve Ls1 represents the relationship between the discharge capacity from the fully charged state and the deformation amount of the secondary battery 2 in the secondary battery 2 in the reference state. The curve Ls1 is obtained in the same manner as the first curve L1, for example, for the secondary battery 2 at the time of manufacture or before shipment, with the secondary battery 2 in an initial stage that has not deteriorated as a reference state.

In the secondary battery 2, when the electrolytic solution is decomposed due to overcharge or the like, the electrolyte may swell as the internal pressure increases due to the decomposed gas (hereinafter sometimes referred to as “gas swell”). . The detection sensor 5 also detects the deformation of the secondary battery 2 due to this gas expansion, but this is only reflected as the overall size of the deformation amount T and does not appear as a change accompanying an increase in the discharge capacity Q. . Therefore, in FIG. 4, the deformation amount T decreases as the discharge capacity Q increases due to the effect of electrode swelling, and even with the same discharge capacity Q, the first curve L1 has a larger deformation amount than the curve Ls1. T is the effect of gas swell.

The first curve L1 has a shape including some irregularities as shown in FIG. 4 due to the stage change of the electrode. For example, in the case of a lithium ion secondary battery using graphite (graphite) for the negative electrode, it is known that the crystalline state of the graphite sequentially changes in stages as it is discharged from the fully charged state. This is because the crystalline state of graphite changes stepwise with the amount of lithium ions inserted, and the average distance between graphene layers expands stepwise to expand the active material of the negative electrode. In short, the volume of the active material changes stepwise due to the stage change, which is reflected in the first curve L1 and the curve Ls1. In obtaining such a first curve L1, the detection sensor 5 that detects the deformation of the secondary battery 2 with high sensitivity is suitable.

Next, a second curve representing the relationship between the charge / discharge capacity (a general term for discharge capacity and charge capacity, which is the discharge capacity from the fully charged state in this embodiment) and the slope of the first curve is obtained ( Step 2). The graph of FIG. 5 shows the second curve L2 obtained from the first curve L1. The slope dT / dQ of the first curve L1 is obtained as a differential value when the deformation amount T is differentiated by the discharge capacity Q. The second curve L2 has two stage change points P1 and P2 that appear as extreme values, which are caused by the stage change described above. A curve Ls2 represents the relationship between the charge / discharge capacity (discharge capacity in the present embodiment) and the slope of the first curve in the secondary battery 2 in the reference state. The curve Ls2 is obtained from the curve Ls1 in the same manner as obtaining the second curve L2 from the first curve L1. The curve Ls2 also has two stage change points Ps1 and Ps2.

As the active material used for the negative electrode of the lithium ion secondary battery, a material capable of electrochemically inserting and extracting lithium ions is used, and the second material having a plurality of stage change points as described above. In obtaining the curve, a negative electrode containing graphite is preferably used. Examples of the active material used for the positive electrode include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , Li (MnAl) ₂ O ₄ , Li (NiCoAl) O ₂ , LiFePO ₄ , and Li (NiMnCo) O _2. be able to.

Subsequently, the charge / discharge capacity Qc between the stage change points appearing as extreme values on the second curve is calculated (step 3). The extreme value is a collective term of the local minimum value and the local maximum value, and the stage change point appears as a local minimum value during discharging and as a local maximum value during charging. In this embodiment, since the discharge capacity from the fully charged state is viewed, the stage change points P1 and P2 appear as minimum values. FIG. 5 shows the charge / discharge capacity Qc between the stage change points P1, P2 and the charge / discharge capacity Qs between the stage change points Ps1, Ps2. For example, in the case of a lithium ion secondary battery using graphite as a negative electrode, the stage changes when one or more lithium ions are inserted for 24 carbons and when one or more lithium ions are inserted for 12 carbons. Occurs when inserted. Therefore, the decrease in the charge / discharge capacity Qc suggests a decrease in the amount of carbon capable of inserting and desorbing lithium ions, and thus the deactivation of the active material can be inferred.

Then, based on the ratio Qc / Qs of the charge / discharge capacity Qc to the charge / discharge capacity Qs between the stage change points in a predetermined reference state, the active material maintenance ratio is calculated (step 4). For example, when the charge / discharge capacity Qc is 411 mAh and the charge / discharge capacity Qs is 514 mAh, the active material maintenance ratio R is 0.8 (≈411 / 514) based on the ratio Qc / Qs. It can be calculated. This is because in the secondary battery 2 after 500 cycles of the charge / discharge process, about 80% of the active material contributing to charge / discharge is maintained, in other words, the active material contributing to charge / discharge is reduced to 80%. In this way, the deterioration of the secondary battery 2 can be diagnosed.

As described above, the charge / discharge capacity Qc is obtained from the second curve L2, and the first curve L1 serving as the source of the second curve L2 is the discharge capacity Q from the fully charged state and the deformation amount T of the secondary battery 2. As a relationship. And even in an environment where charging and discharging are frequently repeated as in an electric vehicle, there are many opportunities to become fully charged, so according to the method of this embodiment, it is used while repeating such charging and discharging. Even if it is a use to do, the deterioration of the secondary battery 2 can be diagnosed simply and with high accuracy.

The curve Ls1 is acquired in advance for the secondary battery 2 at the time of manufacture or before shipment, for example, with the secondary battery 2 in the initial stage that has not deteriorated as a reference state. Therefore, the curve Ls2, the stage change points Ps1 and Ps2, and the charge / discharge capacity Qs can also be obtained in advance. These data can be stored in a storage unit (not shown) included in the control device 6, but at least the charge / discharge capacity Qs is sufficient for the above-described deterioration diagnosis.

In this embodiment, by further executing the following

steps

5 and 6, the amount of capacity balance shift due to the side reaction can be calculated, and the deterioration of the secondary battery 2 can be diagnosed more accurately. In addition, by taking into account the amount of capacity balance deviation due to the side reaction together with the maintenance rate of the active material, it can be used to predict the remaining capacity of the secondary battery 2.

After calculating the charge / discharge capacity Qc, the second curve is corrected using the retention rate of the active material so that the charge / discharge capacity Qc is the same as the charge / discharge capacity Qs (step 5). Specifically, the discharge capacity value of the second curve is divided by the retention rate of the active material. This step may be after the calculation of the charge / discharge capacity Qc, and may be before the maintenance rate is calculated. The graph of FIG. 6 shows a second curve L2 'obtained by correcting the second curve L2. When the charge / discharge capacity Qc is 411 mAh and the charge / discharge capacity Qs is 514 mAh, the value of the discharge capacity Q of the second curve L2 may be divided by 0.8 as the maintenance ratio R. As a result, the corrected charge / discharge capacity Qc ′ of the second curve L2 ′ is 514 mAh, which is the same as the charge / discharge capacity Qs.

The corrected second curve L2 ′ indicates the discharge capacity Q from the fully charged state and the slope dT / dQ of the first curve L1 when it is assumed that there is no deactivation of the active material ascertained by the maintenance ratio R. It is calculated | required as a curve showing the relationship. However, as shown in FIG. 6, the second curve L2 ′ does not coincide with the curve Ls2, and there is a space between the stage change point P1 ′ (or P2 ′) and the corresponding stage change point Ps1 (or Ps2). A discharge capacity difference Qd is observed. This charge / discharge capacity difference Qd is a result of a shift in the capacity balance between the positive electrode 23 and the negative electrode 24, and this shift is due to the difference between the side reaction amount at the positive electrode 23 and the side reaction amount at the negative electrode 24. Arise.

After correcting the second curve as described above, the side reaction is determined based on the charge / discharge capacity difference between the stage change point in the corrected second curve and the corresponding stage change point in a predetermined reference state. The amount of capacity balance deviation due to is calculated (step 6). For example, when the charge / discharge capacity difference Qd is 116 mAh, it can be determined that an excessive side reaction has occurred in the negative electrode 24, and the capacity balance deviation due to the side reaction is calculated to be 116 mAh. In order to correct the deactivation amount of the active material (that is, to make the second curve L2 ′ coincide with the curve Ls2), the second curve L2 ′ is directed in the positive direction of the discharge capacity Q (right direction of the graph). This is considered because it is necessary to shift by 116 mAh.

Thus, not only calculating the maintenance rate of the active material, but also calculating the amount of capacity balance deviation due to side reactions, the deterioration of the secondary battery 2 can be diagnosed with higher accuracy. Furthermore, the end point of the first curve L1 can be estimated by considering the capacity balance deviation amount due to this side reaction together with the maintenance ratio of the active material, and thereby the remaining capacity of the secondary battery 2 can be predicted. For example, after charging and discharging a secondary battery having a capacity of 1440 mAh before deterioration for 500 cycles, the active material retention rate R is 0.8, and the capacity balance deviation due to side reaction is 116 mAh min. When it is diagnosed, the value (mAh) of the discharge capacity Q at the end point of the first curve L1 is estimated from 1440 × 0.8 + 116, and the remaining capacity is calculated by subtracting the discharge capacity at the time of diagnosis from there. Predictable.

As described above, the deterioration diagnosis method and the deterioration diagnosis system of the present embodiment can grasp what capacity deterioration is occurring in the secondary battery, not simply detecting the capacity decrease of the secondary battery, Specifically, how much active material is maintained (in other words, how much active material is deactivated), and how much side reaction (electrochemistry that does not contribute to charge / discharge) It is possible to obtain detailed degradation information indicating whether or not (reaction) has occurred. Furthermore, the remaining capacity can be predicted by estimating the end point of the discharge capacity for the deteriorated secondary battery. Such deterioration diagnosis is executed by the control device 6 including prediction of the remaining capacity.

In the above-described embodiment, the behavior when discharging from a fully charged state to an arbitrary discharging state has been described. Conversely, the behavior when charging from an arbitrary discharging state to a fully charged state is also described above. The deterioration diagnosis can be performed by the same procedure. In this case, in step 1, a first curve representing the relationship between the charged capacity up to the fully charged state and the detected deformation amount of the secondary battery is obtained. The horizontal axis of the graph of FIG. 4 is reversed, and the amount of deformation of the secondary battery increases as the charging capacity up to the fully charged state increases (that is, as it approaches the fully charged state). In Step 2, a second curve representing the relationship between the charge / discharge capacity (charge capacity up to the fully charged state) and the slope of the first curve is obtained. In the graphs of FIGS. 5 and 6, not only the horizontal axis but also the vertical axis is reversed, a second curve having an upward peak is obtained, and a stage change point appears as a maximum value in the second curve (for example, FIG. 7).

Next, an embodiment for determining the deterioration mode by expansion of the reaction distribution will be described with reference to FIGS. This determination of the deterioration mode can be used in combination with the above-described calculation of the active material maintenance rate. In this case, either the calculation of the maintenance ratio of the active material or the determination of the deterioration mode may be performed first, or these may be performed simultaneously.

FIG. 7 is a graph showing the relationship between the charge / discharge capacity (charge capacity until fully charged) and the slope of the first curve. The second curve L3 is obtained by

steps

1 and 2 as described above. The illustration of the first curve serving as the source of the second curve L3 is omitted. The second curve L3 has two stage change points P3 and P4 that appear as extreme values (as maximum values during charging). In addition, two upward peaks having the stage change points P3 and P4 appear in the second curve L3, which are caused by the stage change described above.

The two peaks appearing in the second curve L3 indicate the amount of each active material that completes the stage change in its capacity (charge capacity in FIG. 7). Capacitances Qp31 and Qp41 at the peak start point (points starting from the base line BL) are the capacity at which the reaction proceeds most quickly among the large number of active materials in the electrode, that is, the capacity at which the stage change starts at the earliest. Capacitances Qp32 and Qp42 at the end points of the peaks (points starting to contact the base line BL) are capacitances at which the stage change of all the active materials in the electrodes is completed. The base line BL is defined by a straight line connecting inflection points before and after each peak. The charge / discharge capacity Qw3 is calculated based on the base width from the start point to the end point of the peak, and is specifically obtained by subtracting the capacity Qp31 from the capacity Qp32. The charge / discharge capacity Qw4 is the same as this. The charge / discharge capacities Qw3 and Qw4 indicate the reaction rate distributions of the individual active materials in the electrodes. Therefore, the reaction distribution of the active material in the electrode can be grasped by comparing the peak width such as the base width before and after the deterioration of the secondary battery 2.

Generally, the expansion of the reaction distribution is caused by an increase in ionic resistance or electrical resistance in the electrode. By expanding the reaction distribution, the charge capacity until the lithium metal is deposited during charging is reduced, and the lithium metal is easily deposited. The deposited lithium metal grows in a dendrite shape, which may cause inconveniences such as causing a short circuit between the positive electrode and the negative electrode. Further, at the time of discharging, there is an inconvenience that the reaction distribution is expanded, so that overdischarge occurs in the active material in which the reaction is most likely to proceed, and the deterioration of the battery is promoted.

The graph of FIG. 8 shows a curve Ls3 representing the relationship between the charge / discharge capacity (charge capacity in the present embodiment) and the slope of the first curve in the secondary battery 2 in the reference state. The first curve that is the origin of the curve Ls3 is the same as the curve Ls1 in FIG. 4, with the secondary battery 2 in the initial stage that is not deteriorated as a reference state, for example, the secondary battery 2 before manufacture or before shipment. , Can be acquired in advance. Accordingly, not only the curve Ls3 but also the stage change points Ps3 and Ps4, the baseline BLs, the capacities Qps31, Qps32, Qps41, and Qps42, and the charge / discharge capacities Qws3 and Qws4 can be obtained in advance. The charge / discharge capacity Qws3 is calculated on the basis of the peak base width, and is specifically obtained by subtracting the capacity Qps31 from the capacity Qps32. The charge / discharge capacity Qws4 is the same as this.

As described above, since the width of each peak reflects the reaction rate distribution of the active material in the electrode, the width of the peak appearing in the second curve L3 corresponds to the peak in a predetermined reference state corresponding thereto. If it is larger than the width of, it can be determined that the degradation mode is due to expansion of the reaction distribution. In this embodiment, as shown in FIGS. 7 and 8, since the charge / discharge capacity Qw3 of the second curve L3 is larger than the charge / discharge capacity Qws3 in the corresponding reference state, the reaction distribution is expanded compared to before deterioration. That is, it is determined that the deterioration mode is caused by expansion of the reaction distribution. The same applies to the comparison between the charge / discharge capacity Qw4 and the charge / discharge capacity Qws4. When determining the deterioration mode, either peak may be compared.

Thus, the expansion of the reaction distribution can be easily detected by comparing the charge / discharge capacity Qw3 and the charge / discharge capacity Qws3 or by comparing the charge / discharge capacity Qw4 and the charge / discharge capacity Qws4. In the present embodiment, the charge / discharge capacities to be compared for determination are calculated based on the base width of the peak, but are not limited to this, and may be calculated based on another width of the peak. For example, the charge / discharge capacity may be calculated based on the half width of the peak (the width at the half position of the peak height), and the deterioration mode may be determined by comparison. Even with this method, it is possible to determine the expansion of the reaction distribution before and after deterioration.

Furthermore, by acquiring in advance the relationship between the peak width and the capacity for each discharge rate and temperature, the remaining capacity depending on the current battery discharge rate and temperature can be predicted by referring to the result.

Usually, in a lithium ion secondary battery using graphite as a negative electrode, stage changes of

stages

2 and 3 are observed during charging and discharging. This embodiment is an example in which graphite is used for the negative electrode. In the graphs of FIGS. 7 and 8, the change to the stage 3 is observed as the left peak, and the change to the stage 2 is observed as the right peak. The Among these, the change to stage 2 is a state in which one lithium ion is inserted into 12 carbons (carbon atoms). Lithium metal deposition, which causes various inconveniences, is a state where two or more lithium ions are inserted into 12 carbon atoms (ie, one or more lithium ions are inserted into 6 carbon atoms). It happens in the state of trying to insert). Therefore, the lithium metal is deposited by intercalating a charge capacity more than twice the charge capacity from the fully discharged state to the stage 2.

As described above, the charge capacity at the rising edge of the peak (the charge capacity at the start point) is the capacity at which the reaction proceeds most quickly among the many active materials in the electrode, that is, the capacity at which the stage change is started the fastest in the battery. Show. Therefore, at the peak indicating the change to the stage 2, it is possible to predict the capacity at which the lithium metal is deposited based on the value twice the charge capacity at the rising edge of the peak. From this, in this embodiment, it can be judged that a value twice as large as the charge capacity Qp41 is a capacity for depositing lithium metal.

In the initial design of the battery, the set upper limit voltage is reached and the constant current charge is switched to the constant voltage charge before reaching the double capacity of the charge capacity at the rising edge of the peak, so that lithium metal does not precipitate. . However, as the battery deteriorates and the ionic resistance and electrical resistance increase due to the deposits on the surface of the active material and the relaxation of the binder, the reaction distribution expands, and the charge capacity at the peak rises to the low capacity side. shift. In that case, in the control method of switching to constant voltage charging after reaching the set upper limit voltage, lithium metal deposition is unavoidable.

Therefore, when it is determined that the deterioration mode is due to the expansion of the reaction distribution, the constant current is within a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity Qp41 at the rising edge of the peak appearing in the second curve L3. It preferably includes a step of charging. In such a method, even if deterioration due to expansion of the reaction distribution occurs, the change in the active material having the fastest charging speed to the stage 2 is detected and the constant current charging is terminated, so that lithium metal is not deposited. As a result, safety can be improved and the progress of deterioration can be suppressed. After the constant current charging is finished, the charging may be finished or switched to constant voltage charging.

When using a battery, it is rare that the battery is completely discharged, and charging is usually started with some capacity left. In this case, the charge capacity up to the charge capacity Qp41 changes according to the remaining capacity at the start of charging. Furthermore, the capacity for depositing lithium metal is a charge capacity that is twice or more the value obtained by adding the remaining capacity at the start of charging (substantially zero if fully discharged) to the charging capacity Qp41. Therefore, in the above step, constant current charging is performed within a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity Qp41. For this reason, it is not necessary to set it in a completely discharged state in order to diagnose deterioration and to select suitable charging conditions.

In the embodiment shown in FIG. 2, the polymer matrix layer is formed on the wall portion 28 a of the exterior body 21 that faces the electrode group 22 in the thickness direction of the positive electrode 23 and the negative electrode 24, that is, the Z direction (vertical direction in FIG. 2B). 3 is pasted. The outer surface of the wall portion 28 a corresponds to the upper surface of the exterior body 21. The polymer matrix layer 3 is opposed to the electrode group 22 with the wall portion 28 a interposed therebetween, and is disposed in parallel with the upper surface of the electrode group 22. Since the electrode swelling is caused by the change in the thickness of the electrode group 22 accompanying the change in the volume of the active material, the action in the Z direction is large. Therefore, in the present embodiment in which the polymer matrix layer 3 is attached to the wall portion 28a, it is possible to detect the swollen electrode with high sensitivity, and thus to accurately perform the deterioration diagnosis.

In the embodiment shown in FIG. 3, the polymer matrix layer 3 is attached to the electrode group 22 from the thickness direction of the positive electrode 23 and the negative electrode 24, that is, the Z direction (vertical direction in FIG. 3B). Thereby, even when the exterior body is formed of a robust material such as a metal can, the swollenness of the electrode group 22, that is, the electrode swollenness can be detected with high accuracy, and the deterioration diagnosis can be accurately performed. be able to.

The detection unit 4 is disposed at a location where a change in the external field can be detected, and is preferably affixed to a relatively rigid location that is not easily affected by the swelling of the secondary battery 2. In this embodiment, as shown in FIG. 2B, the detection unit 4 is attached to the inner surface of the casing 11 of the battery module facing the wall 28a. The casing 11 of the battery module is formed of, for example, metal or plastic, and a laminate film may be used. In the drawing, the detection unit 4 is disposed close to the polymer matrix layer 3, but may be disposed away from the polymer matrix layer 3.

In the present embodiment, an example is shown in which the polymer matrix layer 3 contains a magnetic filler as the filler, and the detection unit 4 detects a change in the magnetic field as the external field. In this case, the polymer matrix layer 3 is preferably a magnetic elastomer layer in which a magnetic filler is dispersed in a matrix made of an elastomer component.

Examples of the magnetic filler include rare earths, irons, cobalts, nickels, oxides, etc., but rare earths capable of obtaining higher magnetic force are preferable. The shape of the magnetic filler is not particularly limited, and may be spherical, flat, needle-like, columnar, or indefinite. The average particle size of the magnetic filler is preferably 0.02 to 500 μm, more preferably 0.1 to 400 μm, and still more preferably 0.5 to 300 μm. When the average particle size is smaller than 0.02 μm, the magnetic properties of the magnetic filler tend to be lowered, and when the average particle size exceeds 500 μm, the mechanical properties of the magnetic elastomer layer tend to be lowered and become brittle.

The magnetic filler may be introduced into the elastomer after magnetization, but is preferably magnetized after being introduced into the elastomer. Magnetization after introduction into the elastomer facilitates control of the polarity of the magnet and facilitates detection of the magnetic field.

As the elastomer component, a thermoplastic elastomer, a thermosetting elastomer, or a mixture thereof can be used. Examples of the thermoplastic elastomer include styrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, polybutadiene-based thermoplastic elastomer, polyisoprene-based thermoplastic elastomer, A fluororubber-based thermoplastic elastomer can be used. Examples of the thermosetting elastomer include polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, diene synthetic rubber such as ethylene-propylene rubber, ethylene-propylene rubber, butyl rubber, acrylic rubber, Non-diene synthetic rubbers such as polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, and natural rubber can be mentioned. Among these, a thermosetting elastomer is preferable because it can suppress the sag of the magnetic elastomer accompanying heat generation and overload of the battery. More preferred is polyurethane rubber (also referred to as polyurethane elastomer) or silicone rubber (also referred to as silicone elastomer).

Polyurethane elastomer is obtained by reacting polyol and polyisocyanate. When using a polyurethane elastomer as an elastomer component, an active hydrogen-containing compound and a magnetic filler are mixed, and an isocyanate component is mixed here to obtain a mixed solution. Moreover, a liquid mixture can also be obtained by mixing a magnetic filler with an isocyanate component and mixing an active hydrogen-containing compound. The mixed liquid is poured into a mold subjected to a release treatment, and then heated to a curing temperature and cured to produce a magnetic elastomer. When a silicone elastomer is used as an elastomer component, a magnetic elastomer can be produced by adding a magnetic filler to a silicone elastomer precursor, mixing it, putting it in a mold, and then heating and curing it. In addition, you may add a solvent as needed.

As the isocyanate component that can be used in the polyurethane elastomer, compounds known in the field of polyurethane can be used. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene Aromatic diisocyanates such as diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, nor It can be mentioned alicyclic diisocyanates such as Renan diisocyanate. These may be used alone or in combination of two or more. The isocyanate component may be modified such as urethane modification, allophanate modification, biuret modification, and isocyanurate modification. Preferred isocyanate components are 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, more preferably 2,4-toluene diisocyanate, 2,6-toluene diisocyanate.

As the active hydrogen-containing compound, those usually used in the technical field of polyurethane can be used. For example, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polyether polyol represented by copolymer of propylene oxide and ethylene oxide, polybutylene adipate, polyethylene adipate, representative of 3-methyl-1,5-pentane adipate Polyester polyol such as polyester polyol, polycaprolactone polyol, reaction product of polyester glycol and alkylene carbonate such as polycaprolactone, and the like, and the reaction of the resulting reaction mixture with organic polyol. Polyester polycarbonate polyol reacted with dicarboxylic acid, esterification of polyhydroxyl compound and aryl carbonate High molecular weight polyol polycarbonate polyols obtained by the reaction can be mentioned. These may be used alone or in combination of two or more.

In addition to the high molecular weight polyol component described above as the active hydrogen-containing compound, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6- Hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, and triethanol Low molecular weight polyol component of such emissions, ethylenediamine, tolylenediamine, diphenylmethane diamine, may be used low molecular weight polyamine component of diethylenetriamine. These may be used alone or in combination of two or more. Further, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5-bis ( Methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6- Diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4'-diamino-3,3 ' -Diethyl-5,5'-dimethyldiphenylmethane, N, N'-di-sec-butyl-4,4'-diaminodiphenylmethane, 4,4'-diamy -3,3'-diethyldiphenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3'-diisopropyl-5,5'- Dimethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane, m-xylylenediamine, Polyamines exemplified by N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine and the like can also be mixed. Preferred active hydrogen-containing compounds are polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, 3-methyl-1,5-pentane adipate, more preferably a copolymer of polypropylene glycol, propylene oxide and ethylene oxide. It is a coalescence.

As a preferred combination of the isocyanate component and the active hydrogen-containing compound, as the isocyanate component, one or more of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and 4,4′-diphenylmethane diisocyanate, active hydrogen Examples of the contained compound include polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, and one or more of 3-methyl-1,5-pentaneadipate. More preferably, a combination of 2,4-toluene diisocyanate and / or 2,6-toluene diisocyanate as the isocyanate component and polypropylene glycol and / or a copolymer of propylene oxide and ethylene oxide as the active hydrogen-containing compound. is there.

The polymer matrix layer 3 may be a foam containing dispersed filler and bubbles. A general resin foam can be used as the foam, but it is preferable to use a thermosetting resin foam in consideration of characteristics such as compression set. Examples of the thermosetting resin foam include a polyurethane resin foam and a silicone resin foam. Among these, a polyurethane resin foam is preferable. The above-mentioned isocyanate component and active hydrogen-containing compound can be used for the polyurethane resin foam.

The amount of the magnetic filler in the magnetic elastomer is preferably 1 to 450 parts by weight, more preferably 2 to 400 parts by weight with respect to 100 parts by weight of the elastomer component. If it is less than 1 part by weight, it tends to be difficult to detect a change in the magnetic field, and if it exceeds 450 parts by weight, the magnetic elastomer itself may become brittle.

For the purpose of rust prevention of the magnetic filler, a sealing material for sealing the polymer matrix layer 3 may be provided to the extent that the flexibility of the polymer matrix layer 3 is not impaired. As the sealing material, a thermoplastic resin, a thermosetting resin, or a mixture thereof can be used. Examples of the thermoplastic resin include styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, polyisoprene-based thermoplastic elastomers, Fluorine-based thermoplastic elastomer, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, fluororesin, polyamide, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polybutadiene Etc. Examples of the thermosetting resin include polyisoprene rubber, polybutadiene rubber, styrene / butadiene rubber, polychloroprene rubber, diene-based synthetic rubber such as acrylonitrile / butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, butyl rubber, Non-diene rubbers such as acrylic rubber, polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, natural rubber, polyurethane resin, silicone resin, epoxy resin and the like can be mentioned. These films may be laminated, or may be a film including a metal foil such as an aluminum foil or a metal vapor deposition film in which a metal is vapor deposited on the film.

The polymer matrix layer 3 may be one in which fillers are unevenly distributed in the thickness direction. For example, the polymer matrix layer 3 may have a structure composed of two layers of a region on one side with a relatively large amount of filler and a region on the other side with a relatively small amount of filler. In the region on one side containing a large amount of filler, the change in the external field with respect to small deformation of the polymer matrix layer 3 becomes large, so that the sensor sensitivity to a low internal pressure can be enhanced. Further, the region on the other side with relatively little filler is relatively flexible and easy to move. By attaching this region, the polymer matrix layer 3 (especially the region on one side) is likely to be deformed.

The filler uneven distribution ratio in the region on one side is preferably more than 50, more preferably 60 or more, and further preferably 70 or more. In this case, the filler uneven distribution rate in the other region is less than 50. The filler uneven distribution rate in the region on one side is 100 at the maximum, and the filler uneven distribution rate in the region on the other side is 0 at the minimum. Therefore, a laminate structure of an elastomer layer containing a filler and an elastomer layer not containing a filler may be used. For the uneven distribution of the filler, after introducing the filler into the elastomer component, it can be allowed to stand at room temperature or at a predetermined temperature, and then spontaneously settled according to the weight of the filler, by changing the temperature and time of standing. The filler uneven distribution rate can be adjusted. The filler may be unevenly distributed using a physical force such as centrifugal force or magnetic force. Alternatively, the polymer matrix layer may be constituted by a laminate composed of a plurality of layers having different filler contents.

The filler uneven distribution rate is measured by the following method. That is, the cross section of the polymer matrix layer is observed at a magnification of 100 using a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDS). The area of the entire cross section in the thickness direction and the two areas obtained by dividing the cross section into two in the thickness direction are each subjected to elemental analysis of a metal element specific to the filler (for example, Fe element in the case of the magnetic filler of this embodiment). Find the abundance. For this abundance, the ratio of one area to the entire area in the thickness direction is calculated, and this is used as the filler uneven distribution rate in the one area. The filler uneven distribution rate in the other region is the same as this.

The other region with relatively little filler may have a structure formed of a foam containing bubbles. Thereby, the polymer matrix layer 3 is further easily deformed and the sensor sensitivity is enhanced. Moreover, the area | region of one side may be formed with the foam with the area | region of the other side, and the polymer matrix layer 3 in that case becomes a foam entirely. Such a polymer matrix layer in which at least a part in the thickness direction is a foam is composed of a laminate composed of a plurality of layers (for example, a non-foamed layer containing a filler and a foamed layer not containing a filler). It doesn't matter.

For example, a magnetoresistive element, a Hall element, an inductor, an MI element, a fluxgate sensor, or the like can be used as the detection unit 4 that detects a change in the magnetic field. Examples of the magnetoresistive element include a semiconductor compound magnetoresistive element, an anisotropic magnetoresistive element (AMR), a giant magnetoresistive element (GMR), and a tunnel magnetoresistive element (TMR). Among these, the Hall element is preferable because it has high sensitivity over a wide range and is useful as the detection unit 4. As the Hall element, for example, EQ-430L manufactured by Asahi Kasei Electronics Corporation can be used.

Since the secondary battery 2 in which the gas expansion has progressed may lead to troubles such as ignition and rupture, in this embodiment, when the expansion amount when the secondary battery 2 is deformed is greater than or equal to a predetermined amount, charging and discharging are performed. It is configured to be blocked. Specifically, the signal detected by the detection sensor 5 is transmitted to the control device 6, and the control device 6 transmits a signal to the switching circuit 7 when a change in the external field exceeding the set value is detected by the detection sensor 5. Then, the current from the power generation device (or charging device) 8 is cut off, and charging / discharging to the battery module 1 is cut off. Thereby, the trouble resulting from gas bulging can be prevented beforehand.

In the above-described embodiment, an example in which the secondary battery is a lithium ion secondary battery has been described, but the present invention is not limited thereto. The secondary battery used is not limited to a non-aqueous electrolyte secondary battery such as a lithium ion battery, and may be an aqueous electrolyte secondary battery such as a nickel metal hydride battery.

In the above-described embodiment, the example in which the change in the magnetic field due to the deformation of the polymer matrix layer is detected by the detection unit has been described. However, other changes in the external field may be detected. For example, the polymer matrix layer may contain conductive fillers such as metal particles, carbon black, and carbon nanotubes as fillers, and the detector may detect changes in the electric field (changes in resistance and dielectric constant) as external fields. It is done.

The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Battery module 2 Sealed secondary battery 3 Polymer matrix layer 4 Detection part 5 Detection sensor 6 Control device 7 Switching circuit 8 Power generation device or charging device 21 Exterior body 22 Electrode group 23 Positive electrode 24 Negative electrode 25 Separator L1 First curve L2 First 2 Curve P1 Stage change point P2 Stage change point

Claims

In the method for diagnosing deterioration of sealed secondary batteries,
The deformation of the sealed secondary battery is detected, and a first curve representing the relationship between the discharge capacity from the fully charged state or the charged capacity to the fully charged state and the detected deformation amount of the sealed secondary battery is obtained. Steps,
Obtaining a second curve representing the relationship between the charge / discharge capacity and the slope of the first curve;
Calculating a charge / discharge capacity Qc between stage change points appearing as extreme values in the second curve;
Calculating a maintenance factor of the active material based on a ratio Qc / Qs of the charge / discharge capacity Qc to the charge / discharge capacity Qs between the stage change points in a predetermined reference state. Secondary battery deterioration diagnosis method.
Correcting the second curve using the maintenance factor so that the charge / discharge capacity Qc is the same as the charge / discharge capacity Qs;
Calculating a capacity balance deviation amount due to a side reaction based on a charge / discharge capacity difference between the stage change point in the corrected second curve and the corresponding stage change point in a predetermined reference state; The deterioration diagnosis method for a sealed secondary battery according to claim 1.
When the charge / discharge capacity calculated based on the peak width appearing in the second curve is larger than the charge / discharge capacity calculated based on the corresponding peak width in a predetermined reference state, The deterioration diagnosis method for a sealed secondary battery according to claim 1, comprising a step of determining a deterioration mode due to expansion.
When it is determined that the deterioration mode is due to the expansion of the reaction distribution, the step of performing constant current charging in a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity at the rising edge of the peak appearing in the second curve A deterioration diagnosis method for a sealed secondary battery according to claim 3.
A polymer matrix layer is affixed to the sealed secondary battery, and the polymer matrix layer contains dispersed fillers that change the external field according to deformation of the polymer matrix layer.
The sealed secondary battery according to any one of claims 1 to 4, wherein the deformation of the sealed secondary battery is detected by detecting a change in the external field according to the deformation of the polymer matrix layer. Degradation diagnosis method.
The polymer matrix layer contains a magnetic filler as the filler,
The deterioration diagnosis method for a sealed secondary battery according to claim 5, wherein the deformation of the sealed secondary battery is detected by detecting a change in a magnetic field as the external field.
In a sealed secondary battery deterioration diagnosis system,
A detection sensor for detecting deformation of the sealed secondary battery;
A first curve representing a relationship between a discharge capacity from a full charge state or a charge capacity to a full charge state and a deformation amount of the sealed secondary battery detected by the detection sensor, and the charge / discharge capacity and the first A second curve representing the relationship with the slope of one curve is obtained, the charge / discharge capacity Qc between the stage change points appearing as extreme values in the second curve is calculated, and the charge / discharge capacity between the stage change points in a predetermined reference state And a controller for calculating a maintenance factor of the active material based on a ratio Qc / Qs of the charge / discharge capacity Qc with respect to Qs.
The control device corrects the second curve using the maintenance factor so that the charge / discharge capacity Qc is the same as the charge / discharge capacity Qs, and changes the stage in the second curve after the correction. 8. The deterioration diagnosis system for a sealed secondary battery according to claim 7, wherein a capacity balance deviation amount due to a side reaction is calculated based on a charge / discharge capacity difference between a point and a stage change point corresponding to the predetermined reference state. .
When the charge / discharge capacity calculated based on the peak width appearing in the second curve is larger than the charge / discharge capacity calculated based on the corresponding peak width in a predetermined reference state, The degradation diagnosis system for a sealed secondary battery according to claim 7, wherein the degradation mode is determined to be a degradation mode due to expansion.
The constant current charging is performed in a range not exceeding twice the value obtained by adding the remaining capacity at the start of charging to the charging capacity at the rising edge of the peak appearing in the second curve when it is determined that the deterioration mode is due to expansion of the reaction distribution. 10. A deterioration diagnosis system for a sealed secondary battery according to 9.
The detection sensor includes a polymer matrix layer attached to the sealed secondary battery, and a detection unit,
11. The polymer matrix layer contains dispersed fillers that change the external field according to deformation of the polymer matrix layer, and the detection unit detects the change in the external field. 2. A degradation diagnosis system for a sealed secondary battery according to item 1.
The deterioration diagnosis system for a sealed secondary battery according to claim 11, wherein the polymer matrix layer contains a magnetic filler as the filler, and the detection unit detects a change in a magnetic field as the external field.