WO2021186804A1

WO2021186804A1 - Battery capacity recovery quantity diagnosis method

Info

Publication number: WO2021186804A1
Application number: PCT/JP2020/045371
Authority: WO
Inventors: 杉政　昌俊; 耕平本蔵; 渉太伊藤; 栄二關; 誠之廣岡; 純川治
Original assignee: 株式会社日立ハイテク
Priority date: 2020-03-16
Filing date: 2020-12-07
Publication date: 2021-09-23
Also published as: JP2021150008A

Abstract

Provided is a method for conveniently ascertaining the condition of a capacity recovery electrode at any given time, in a lithium-ion battery in which capacity is recovered by replenishing with lithium ions from a third electrode that includes lithium in the interior thereof.　A battery capacity recovery quantity diagnosis method for a secondary battery cell (100) that comprises a positive electrode (11), a negative electrode (12), and a capacity recovery electrode (15), wherein the open circuit potential of the capacity recovery electrode (15) is measured treating the electrode potential of the secondary battery cell (100) as a reference, with the positive electrode (11) or the negative electrode (12) as the reference electrode.

Description

Battery capacity recovery diagnostic method

The present invention relates to a method for diagnosing the amount of recovery of the battery capacity of a secondary battery.

Lithium-ion batteries are one of the non-aqueous electrolyte secondary batteries, and because of their high energy density, they are also used as batteries for portable devices and, in recent years, as batteries for electric vehicles. However, it is known that a lithium ion battery deteriorates with use and the battery capacity decreases.
In a lithium ion battery, a lithium metal oxide is generally used as the active material of the positive electrode, and a carbon material such as graphite is generally used as the active material of the negative electrode. The positive electrode and the negative electrode of a lithium ion battery are formed by adding a binder (binding agent), a conductive agent, or the like to a group of minute active material particles to form a slurry (mixture), and then applying the mixture to a metal foil.
At the time of charging, the lithium ions released from the active material of the positive electrode are occluded in the active material of the negative electrode, and at the time of discharging, the lithium ions stored in the active material of the negative electrode are occluded and stored in the active material of the positive electrode. In this way, lithium ions move between the electrodes, causing a current to flow between the electrodes.

In such a lithium ion battery, the capacity is increased by (1) electrical isolation of the positive electrode active material, (2) electrical isolation of the negative electrode active material, and (3) immobilization of lithium ions moving back and forth between the electrodes. Decrease.
Of these factors, for the capacity reduction due to (3) above, a lithium ion battery having a third electrode containing lithium inside is manufactured, and lithium ions are replenished from the third electrode to the positive electrode or the negative electrode. By doing so, it is possible to recover the reduced capacity. Hereinafter, the third electrode installed for the purpose of capacity recovery is referred to as a capacity recovery electrode.

On the other hand, in a lithium-ion battery equipped with a capacity recovery electrode, it is important to grasp the state of the capacity recovery electrode. Since the capacity recovery amount of the lithium-ion battery is limited to the capacity of the capacity recovery electrode, if the recovery process is excessively performed without grasping the state of the capacity recovery electrode, the positive and negative electrodes used for charging and discharging will be damaged. As a result, the lithium-ion battery may become unstable, or the battery itself may be destroyed due to a short circuit caused by the formation of a dendrite due to excessive precipitation of lithium ions.
Patent Document 1 and Patent Document 2 are related to these techniques.

[Summary] of Patent Document 1 provides "[Problem] A lithium ion secondary battery capacity recovery method for realizing effective capacity recovery using a third electrode. [Solution] Capacity disclosed here. In the recovery method, the potential difference (V) between the positive electrode and the third electrode is measured while the capacity recovery treatment is being performed, and the capacity recovery treatment is performed on the condition that the measured potential difference reaches a predetermined stop reference value. Here, as a stop reference value, the positive electrode and the third electrode are made conductive in advance using a reference lithium ion secondary battery having the same configuration as the lithium ion secondary battery whose capacity is to be restored, and the time from the start of the conduction is reached. The potential difference (V) between the positive electrode and the third electrode, which decreases with the passage of time, is monitored, the fluctuation of the potential difference with the passage of time (hr) is determined from the monitored potential difference, and the potential difference downward fluctuation period is determined from the potential difference fluctuation. , The potential difference fluctuation transition period and the potential difference downward stable period are determined, and the potential difference corresponding to the potential difference fluctuation transition period is adopted. ”, And the technique of the capacity recovery method of the lithium ion secondary battery is disclosed.

[Summary] of Patent Document 2 provides a "[problem] a method for managing the state of a lithium ion battery capable of replenishing an appropriate amount of lithium ions that suppress the formation of lithium dendrites and recovering the capacity thereof. A method for managing a state of a lithium ion battery includes a positive electrode containing a first active material and a second active material having a lower electrode potential than the first active material, a negative electrode, and an electrolyte solution. It is a state management method for lithium-ion batteries, and the amount of decrease in lithium ions is used to determine the cause of deterioration of the lithium-ion battery by comparing the initial charge / discharge state of the lithium-ion battery with the charge / discharge state at the time of determination. Is calculated. ”, And the technology of the state management method of the lithium ion battery is disclosed.

As described above, in Patent Document 1, "While performing the capacity recovery process, the potential difference (V) between the positive electrode and the third electrode was measured, and the measured potential difference reached a predetermined stop reference value. The capacity recovery process is stopped on the condition that the capacity recovery process is performed. ”While the volume recovery process is being performed, the potential difference (V) between the positive electrode and the third electrode is measured.
Further, in Patent Document 2, a method is adopted in which the capacity to be recovered is defined by measuring the positive electrode potential.

JP-A-2017-911923 Japanese Unexamined Patent Publication No. 2012-195055

It is expected that the life of lithium-ion batteries will be greatly extended by the generalization of capacity recovery using capacity recovery poles. Along with this, the used battery market is expected to rise, but in order to accurately grasp the value of used batteries, it is necessary to establish a means for easily grasping the capacity of the third electrode.
Further, even when the battery is continuously used for the same purpose for a long period of time, it is important to grasp the state of the capacity recovery electrode even when the capacity recovery time is determined or when the recovery effect cannot be expected and the battery replacement time is determined.
Further, when the capacity recovery electrode is electrically isolated, the capacity recovery cannot be performed, and the surface condition of the capacity recovery electrode may hinder the capacity recovery process. Even if it is understood that a problem has occurred in these capacity recovery poles themselves in the process of capacity recovery processing, there is no way to deal with it, and it will greatly hinder the subsequent battery operation plan.
The constant grasp of the potential of the capacity recovery electrode is indispensable for understanding the recoverable capacity and the surface condition of the capacity recovery electrode. It is a very important factor in grasping the accurate value of lithium-ion batteries.

However, since the method described in Patent Document 1 is a method of "measuring the potential difference (V) between the positive electrode and the third electrode while performing the capacity recovery treatment", the capacity recovery electrode itself Since it is a method of performing the capacity recovery process while the state is unknown, it is not possible to know in advance whether the recovery process is possible and the recoverable capacity until the recovery process is performed, and before the capacity recovery process is performed. , There is a problem (problem) that it is difficult to make an operation plan of how to perform capacity recovery processing.
Further, since the method described in Patent Document 2 is a method of "measuring the positive electrode potential", the state of the capacitance recovery electrode is unknown, and an operation plan for how to appropriately perform the capacitance recovery process is made. There is a problem (problem) that it is difficult.

An object of the present invention is to provide a method for easily constantly grasping the state of the capacity recovery electrode in a lithium ion battery that recovers capacity by replenishing lithium ions from a third electrode containing lithium inside. do.

In order to solve the above-mentioned problems, the present invention was configured as follows.
That is, the method for diagnosing the amount of recovery of battery capacity of the present invention is a method for diagnosing the amount of recovery of battery capacity of a secondary battery cell including a positive electrode, a negative electrode, and a capacity recovery electrode, and the electrode potential of the secondary battery cell is the positive electrode. Alternatively, the open circuit potential of the capacitance recovery electrode is measured with the negative electrode as a reference electrode.

In addition, other means will be described in the form for carrying out the invention.

According to the present invention, in a lithium ion battery that recovers capacity by replenishing lithium ions from a third electrode containing lithium inside, the state of the capacity recovery electrode can be easily grasped. Therefore, it is possible to easily estimate the remaining capacity recovery amount of the battery and the surface state of the capacity recovery electrode, and it is possible to easily grasp the battery usage plan and the value of the battery.

It is a figure which conceptually shows an example of the cross section of the cell of the lithium ion battery which has a capacity recovery electrode. It is a figure which shows an example of the cross section of the power generation element of the cell of FIG. 1 conceptually. It is a figure which conceptually shows the configuration example of the charge / discharge device connected to the battery pack which has a capacity recovery electrode. It is a figure which shows an example of the relationship between the capacity recovery electrode measurement potential and the Li recovery amount in a lithium ion battery which has a capacity recovery electrode. It is a figure which shows an example of the relationship between the electric potential and the discharge amount of a battery cell, a positive electrode, and a negative electrode in a cell of a lithium ion battery. It is a figure which shows an example of the potential measurement result of the capacity recovery electrode measured with respect to the positive electrode in the fully charged state in the method of diagnosing the recovery amount of the battery capacity of the secondary battery which concerns on 1st Embodiment of this invention. It is a figure which shows the relationship between the potential of the negative electrode and the discharge capacity. It is a figure which shows the relationship between dV / dQ and the discharge capacity. It is a figure which shows the relationship between the potential of the negative electrode, and the Li recoverable amount in the method of diagnosing the recovery amount of the battery capacity of the secondary battery which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings as appropriate.
However, it is not easy to understand immediately the method of diagnosing the recovery amount of the battery capacity of the secondary batteries of the first embodiment and the second embodiment of the present invention.
Therefore, first, <structure of lithium ion battery cell>, <charge / discharge device>, and <relationship between capacity recovery electrode measurement potential and Li recoverable amount> will be described first.
After that, a method of diagnosing the amount of recovery of the battery capacity of the secondary batteries of the first embodiment and the second embodiment of the present invention will be described.

<Lithium-ion battery cell structure>
The structure of the cell of the lithium ion battery will be described with reference to FIGS. 1 and 2.
FIG. 1 is a diagram conceptually showing an example of a cross section of a cell of a lithium ion battery having a capacity recovery electrode. Note that FIG. 1 is a view seen from the left side of the paper surface of FIG. 2, which will be described later.
In FIG. 1, the cell (battery cell, secondary battery) 100 includes an electrode occupying portion 1, a positive electrode terminal (tab) 2, a negative electrode terminal (tab) 3, a capacitance recovery electrode terminal (tab) 4, and a separator 5. And the exterior material 6.
The exterior material 6 is made of a laminated film or a similar material.
As described above, FIG. 1 is a view seen from the left side of the paper surface of FIG. 2, which will be described later, and the electrode occupying portion 1 is a portion corresponding to the capacitance recovery electrode 15, the negative electrode 12, and the positive electrode 11 in FIG. Areas that appear to overlap are shown.

FIG. 2 is a diagram conceptually showing an example of a cross section of a power generation element (component of a power generation mechanism) of the cell of FIG.
In FIG. 2, the power generation element of the cell includes a positive electrode 11, a negative electrode 12, a capacity recovery electrode 15, and a separator 5. The electrolytic solution as a battery is impregnated into micropores such as a positive electrode 11, a negative electrode 12, a capacity recovery electrode 15, and a separator 5. Therefore, the electrolytic solution is not shown in FIGS. 2 and 1.
Further, in FIG. 2, in the power generation element, the positive electrode 11 and the negative electrode 12 are alternately arranged with the separator 5 interposed therebetween. Further, the capacitance recovery electrode 15 is arranged on the outermost side as an electrode.
A separator 5 is also arranged outside the capacitance recovery electrode 15. For the separator 5, for example, polypropylene is used. However, as the separator 5, in addition to polypropylene, a microporous film made of polyolefin such as polyethylene, a non-woven fabric, or the like can be used.

The positive electrode 11, the negative electrode 12, and the capacity recovery electrode 15 are each produced by applying an appropriate mixture of an electrode active material, a conductive agent, a binder, and the like to an appropriate metal current collector foil. ..
In the cell of the lithium ion battery which is the subject of the present invention, any current collector can be used without being limited by the material, shape, manufacturing method and the like.

<< Positive electrode 11, capacity recovery electrode 15 >>
The collecting foil of the positive electrode 11 and the capacity recovery electrode 15 is an aluminum foil having a thickness of 10 to 100 μm, an aluminum perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, and a foamed metal plate. Etc. are used. Further, as the material, stainless steel, titanium and the like can be applied in addition to aluminum.

It is desirable that the electrode active material of the positive electrode 11 and the capacity recovery electrode 15 contains a reaction species inside. The reactive species of lithium-ion batteries is lithium-ion. In this case, the electrode active material contains a lithium-containing compound capable of reversibly inserting and removing lithium ions.
The types of electrode active materials of the positive electrode 11 and the capacity recovery electrode 15 include, for example, lithium cobalt oxide, manganese-substituted lithium cobalt oxide, lithium manganate, lithium nickel oxide, and transition metal lithium phosphate such as olivine-type lithium iron phosphate. _{_{_{_{li w Ni x Co y Mn z}}}} O 2 ( wherein, w, x, y, z is 0 or a positive value) and the like.

Further, as the electrode active material of the positive electrode 11 and the capacity recovery electrode 15, the above-mentioned materials may be contained alone or in combination of two or more.
The positive electrode 11 and the capacity recovery electrode 15 may use the same configuration. By using the same configuration for the positive electrode 11 and the capacity recovery electrode 15, the manufacturing cost can be reduced.

<< Negative electrode 12 >>
As the current collecting foil of the negative electrode 12, a copper foil having a thickness of 10 to 100 μm, a copper perforated foil having a thickness of 10 to 100 μm and a pore diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like is used.
In addition to copper, stainless steel, titanium, etc. can also be applied as the material.
The electrode active material of the negative electrode 12 contains a substance capable of reversibly inserting and removing lithium ions. The type of electrode active material for the negative electrode 12 is, for example, natural graphite, a composite carbonaceous material in which a film is formed on natural graphite by a dry CVD method or a wet spray method, a resin material such as epoxy or phenol, or petroleum or coal. Artificial graphite produced by firing using the obtained pitch-based material as a raw material, silicon (Si), graphite mixed with silicon, non-graphitized carbon material, lithium titanate Li ₄ Ti ₅ O _{12, and the} like can be used.
As the negative electrode active material, the above-mentioned materials may be contained alone or in combination of two or more.

《Electrolytic solution》
The power generation element (component of the power generation mechanism) includes an electrolytic solution in addition to the positive electrode 11, the negative electrode 12, the capacity recovery electrode 15, and the separator 5. The positive electrode 11, the negative electrode 12, the capacity recovery electrode 15, and the separator 5 are made of a porous material and are impregnated with an electrolytic solution. Therefore, the electrolytic solution is not shown in FIG. 2 or FIG.
In the case of a lithium ion battery, the electrolytic solution is, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl. An aproton organic solvent such as propyl carbonate (MPC) or ethyl propyl carbonate (EPC) can be used.

Alternatively, in the solvent of the above two or more mixed organic compounds, lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium perchlorate, lithium iodide, lithium chloride, lithium bromide, LiB [OCOCF ₃ ] ₄ , LiB [OCOCF ₂ CF ₃ ] ₄ , LiPF ₄ (CF ₃ ) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) _2, etc. ..
Alternatively, an electrolytic solution in which the above-mentioned two or more kinds of mixed lithium salts are dissolved can be mentioned.

As shown in FIG. 1, the current collecting foils of the positive electrode (11: FIG. 2), the negative electrode (12: FIG. 2), and the capacitance recovery electrode (15: FIG. 2) have metal tabs (2) as terminals for each. , 3, 4: (Fig. 1) is connected. The exterior material 6 is sealed so that only the tab portion is exposed to the outside of the laminated film. With this structure, it is possible to electrically connect the tab portion to the outside of the cell 100 of the lithium ion battery.

<Charging / discharging device>
FIG. 3 is a diagram conceptually showing a configuration example of a charging / discharging device 350 connected to a battery pack 300 having a capacity recovery electrode. The charging / discharging device 350 also serves as a measuring instrument for grasping the state of the battery pack 300.
In FIG. 3, the battery pack 300 has a capacity recovery electrode terminal 4 in addition to the positive electrode terminal 2 and the negative electrode terminal 3.
The charging / discharging device 350 includes a current meter 351 (current sensor, current measuring means), a voltmeter 352 (voltage sensor, voltage measuring means), a capacity recovery pole voltmeter 358 (voltage sensor), a resistor 353, and a power supply. It includes 354, a control unit 355, a charge / discharge changeover switch 356, a capacity recovery switch 357, and a positive / negative voltage changeover switch 359.

The battery pack 300 may include a plurality of cells. Further, the battery pack 300 may be configured to include a plurality of battery modules including a plurality of cells. As used herein, the term "secondary battery" is a concept that includes a cell, a battery module, or a battery pack of a lithium ion battery.

In FIG. 3, each terminal of the positive electrode terminal 2, the negative electrode terminal 3, and the capacity recovery electrode terminal 4 of the battery pack 300 is connected to the charging / discharging device 350, respectively.
The capacity recovery switch 357 is arranged so as to connect any of the negative electrode terminal 3 and the capacity recovery electrode terminal 4 of the battery pack 300 to either the resistor 353 and the power supply 354 via the charge / discharge changeover switch 356. There is. The power supply 354 is for charging, and the resistor 353 is for discharging.
The positive / negative electrode changeover switch 359 is arranged so as to connect either the positive electrode terminal 2 or the negative electrode terminal 3 of the battery pack 300 to either the resistor 353 or the power supply 354.

The ammeter 351 measures the current flowing between the positive electrode terminal and the negative electrode terminal of the battery pack 300, between the positive electrode terminal and the capacity recovery electrode terminal, or between the negative electrode terminal and the capacity recovery terminal, and outputs the result to the control unit 355.
The voltmeter 352 measures the voltage between the positive electrode and the negative electrode, and outputs the result to the control unit 355.
The voltmeter 358 measures the voltage of the capacitance recovery electrode with reference to the positive electrode or the negative electrode, and outputs the result to the control unit 355.
The control unit 355 appropriately switches and controls the charge / discharge changeover switch 356, the capacity recovery switch 357, and the positive / negative electrode changeover switch 359 based on the information of the voltmeter 352, the voltmeter 358, and the ammeter 351.
The charging / discharging device 350 carries out the measurement step and the charging step while switching the charge / discharge changeover switch 356, the capacity recovery switch 357, and the positive / negative electrode changeover switch 359 by the control unit 355.

Note that FIG. 3 shows that the voltmeter 358 is connected between the positive electrode terminal and the capacitance recovery electrode terminal by the solid wire wiring. Further, by selecting the wiring of the broken line, the voltmeter 358 measures the voltage between the negative electrode terminal and the capacitance recovery electrode terminal. Alternatively, voltmeters may be installed both between the negative electrode terminal and the capacitance recovery electrode terminal and between the positive electrode terminal and the capacitance recovery electrode terminal.
Further, the charging / discharging device 350 (which also serves as a measuring instrument) used in the embodiment of the present invention described later is not limited to the configuration shown in FIG. 3, and includes the positive electrode terminal, the negative electrode terminal, and the capacity recovery extreme of the battery pack 300. Any circuit configuration may be used as long as it can connect the child and any two terminals selected from.

<Relationship between capacitance recovery electrode measurement potential and Li recoverable amount>
In a lithium ion battery having a capacity recovery electrode, there is a predetermined relationship between the capacity recovery electrode measurement potential and the Li recoverable amount.
FIG. 4 is a diagram showing an example of the relationship between the capacity recovery electrode measurement potential and the Li recoverable amount in a lithium ion battery having a capacity recovery electrode. The capacitance recovery pole measurement potential is a measurement of the potential in the open circuit state of the capacitance recovery pole (open circuit potential of the capacitance recovery pole).
Further, the "relationship between the capacity recovery electrode measurement potential and the Li recoverable amount" differs depending on the lithium ion battery having various characteristics. Further, the relationship (characteristic) differs depending on whether the capacitance recovery electrode measurement potential is with respect to the positive electrode or the negative electrode.
FIG. 4 is a diagram generally explaining the relationship between the capacity recovery electrode measurement potential and the Li recoverable amount in a lithium ion battery having a capacity recovery electrode.

In FIG. 4, the horizontal axis represents the Li recoverable amount Q (Ah), which is the amount that can recover the capacity of the lithium ion battery. The amount of Li recoverable is defined by the product of the current A and the time h. The vertical axis is the measurement potential of the capacitance recovery electrode. As described above, since FIG. 4 is a diagram for explaining the characteristics in general, the reference for measuring the potential of the capacitance recovery electrode may be the positive electrode side or the negative electrode side.
In FIG. 4, the characteristic line 401 shows the relationship between the Li recoverable amount Q (Ah) and the capacitance recovery pole measurement potential.
In FIG. 4, it is assumed that the “relationship between the Li recoverable amount Q (Ah) and the capacity recovery pole measurement potential” of the lithium ion battery having a predetermined capacity recovery pole can be grasped.

The "Li recoverable amount" will be described. The capacity recovery electrode has lithium ions inside. By performing the recovery process, lithium ions are supplied from the capacity recovery electrode to the positive electrode or the negative electrode. In the process, lithium ions at the capacity recovery electrode decrease.
In the capacity recovery electrode with reduced lithium ions, the "Li recoverable amount" means the amount of lithium ions contained in the capacity recovery electrode. That is, it is an amount capable of recovering lithium in the positive electrode or the negative electrode.
Further, when the capacity recovery electrode supplies lithium ions to the positive electrode or the negative electrode, the "Li recoverable amount" of the capacity recovery electrode decreases, but the potential of the capacity recovery electrode changes with this decrease.

The potential of the capacity recovery pole (open circuit potential of the capacity recovery pole) is measured for the lithium ion battery having the capacity recovery pole. Then, it is assumed that the capacitance recovery pole measurement potential at the measurement point 402 is obtained. Then, the Li recoverable amount Q (Ah) can be grasped from the relationship between the Li recoverable amount Q (Ah) of the characteristic line 401 obtained in advance and the capacitance recovery pole measurement potential.
If the measurement point 403 is the maximum amount of lithium ions accumulated with respect to the capacity recovery electrode, at the measurement point 402, the difference on the horizontal axis between the measurement point 402 and the measurement point 403 is the available amount of lithium at the measurement point 402. Then, it becomes the "Li remaining amount" of the capacity recovery electrode.
When charging or discharging a lithium-ion battery having a capacity recovery electrode, the charging implementation plan and the discharge limit can be grasped based on the above obtained data.

<About the embodiment>
The structure and characteristics of the lithium-ion battery having the capacity recovery electrode and the charging / discharging device have been described above.
Next, based on the above description, a method for diagnosing the amount of recovery of the battery capacity of the secondary batteries of the first embodiment and the second embodiment of the present invention will be described in order.

<< First Embodiment: Method for diagnosing the amount of recovery of the battery capacity of the secondary battery >>
The method for diagnosing the amount of recovery of the battery capacity of the secondary battery according to the first embodiment of the present invention will be described with reference to FIGS. 5 and 6.
FIG. 5 is a diagram showing an example of the relationship between the discharge amount of the battery cell, the positive electrode, and the negative electrode and the voltage (potential) in the cell of the lithium ion battery. The capacity recovery pole is not shown.
In FIG. 5, the characteristic 500 shows the relationship between the voltage of the battery cell and the discharge amount Q. The characteristic line 501 shows the relationship between the potential (voltage) of the positive electrode and the discharge amount Q. The characteristic line 502 shows the relationship between the potential (voltage) of the negative electrode and the discharge amount Q.
Further, the alternate long and short dash line 503 corresponds to a state in which the discharge amount Q is 0, that is, a state in which the battery cell is fully charged.
In FIG. 5, the vertical axis represents voltage or potential (V), and the horizontal axis represents discharge amount (Ah).

In FIG. 5, when the battery cell (cell) is discharged from a fully charged state, the voltage decreases with the discharge, as shown in the characteristic line 500. Further, the potential of the positive electrode decreases according to the characteristic line 501. Further, the potential of the negative electrode increases according to the characteristic line 502.
When the battery cells are discharged as described above, both the positive electrode potential and the negative electrode potential change, but the positive electrode potential (characteristic line 501) changes with respect to the change in the negative electrode potential (characteristic line 502). , It can be seen that the change is relatively large.

The method for diagnosing the amount of recovery of the battery capacity of the secondary battery according to the first embodiment of the present invention is a method of measuring the potential of the capacity recovery electrode with the potential of the positive electrode as a reference (referring to the positive electrode).
Therefore, when the potential of the positive electrode is used as a reference, it is important to devise a method for accurately and stably measuring the amount of recovery of the battery capacity of the secondary battery by the capacity recovery electrode.
Therefore, when the positive electrode is used as a reference, the positive electrode in a fully charged state (predetermined state) is used as a reference. If it is defined as measurement (measurement) in a fully charged state, the stability of measurement is relatively improved.
The fully charged state of the positive electrode corresponds to the characteristic point 504 in FIG.

FIG. 6 is a diagram showing an example of the potential measurement result of the capacity recovery electrode measured with reference to the positive electrode in the fully charged state in the method for diagnosing the recovery amount of the battery capacity of the secondary battery according to the first embodiment of the present invention. ..
In FIG. 6, the vertical axis represents the potential (V) of the capacitance recovery electrode measured with reference to the positive electrode, that is, the open circuit potential of the capacitance recovery electrode, and the horizontal axis represents the Li recoverable amount Q (Ah) of the capacitance recovery electrode. be.
In the method for diagnosing the amount of recovery of the battery capacity of the secondary battery of the first embodiment, the same material is used for the positive electrode and the capacity recovery electrode. Therefore, in FIG. 6, the potential of the capacitance recovery electrode before the recovery process is 0 (V).

First, the recovery process is performed within a predetermined range by the capacitance recovery electrode from the state where the potential of the capacitance recovery electrode is 0 (V).
Then, as shown in FIG. 5, the battery cell (secondary battery) is fully charged by the positive electrode and the negative electrode. The potential of the capacity recovery electrode is measured in this fully charged state.
After this measurement, the recovery process is performed again within a predetermined range by the capacity recovery electrode. Then, as described above, the battery cell (secondary battery) is fully charged by the positive electrode and the negative electrode, and the potential of the capacity recovery electrode is measured in this fully charged state.
In this way, each time the recovery process is performed, the battery is fully charged and the potential of the capacity recovery electrode is measured.
This recovery process and the potential of the capacity recovery electrode after being fully charged are repeated.

In this way, the decrease in the potential of the positive electrode, that is, the deterioration can be measured based on the data when the positive electrode is fully charged. Further, the decrease in the potential of the positive electrode changes depending on the condition of the capacity recovery electrode. That is, the amount of Li recoverable at the capacity recovery electrode can be calculated from the measurement of this deterioration.
The point at which the measurement is repeated is the measurement point 601 shown by the plurality of points in FIG.
As shown in FIG. 6, it is possible to obtain a continuous measurement result of the relationship between the potential of the capacity recovery electrode in the fully charged state and the Li recoverable amount at the capacity recovery electrode.
By measuring the potential of the capacity recovery electrode and comparing and referring to the two data based on the data obtained in FIG. 6, the Li recoverable amount (capacity recoverable amount) can be grasped and the charging implementation plan can be performed. And you can grasp the limit of discharge.

<Summary of the first embodiment>
The method for diagnosing the amount of recovery of the battery capacity of the secondary battery of the first embodiment is a method of measuring the potential of the capacity recovery electrode with reference to the potential of the positive electrode. However, as shown in FIG. 5, the potential of the positive electrode changes greatly. Therefore, when the potential of the positive electrode is used as a reference, it is important to devise a method for accurately and stably measuring the amount of recovery of the battery capacity of the secondary battery by the capacity recovery electrode.
Therefore, when the positive electrode is used as a reference, the positive electrode in a fully charged state is used as a reference. If it is defined as measurement (measurement) in a fully charged state, the stability of measurement is relatively improved.
Then, the potential of the capacity recovery electrode is constantly measured, and the Li recoverable amount (capacity recoverable amount) is grasped.

<Effect of the first embodiment>
By measuring the potential of the capacity recovery electrode based on the data obtained from the relationship between the potential of the capacity recovery electrode and the amount of Li recoverable, an accurate operation plan for the lithium-ion battery based on the remaining capacity and secondary use It is possible to easily grasp the accurate value of the lithium-ion battery in such cases.

<< Second Embodiment: Method for diagnosing the amount of recovery of the battery capacity of the secondary battery >>
The method for diagnosing the amount of recovery of the battery capacity of the secondary battery according to the second embodiment of the present invention will be described with reference to FIGS. 7A, 7B, and 8.
The method for diagnosing the amount of recovery of the battery capacity of the secondary battery of the second embodiment of the present invention is a method of measuring the potential of the capacity recovery electrode with the potential of the negative electrode as a reference (referring to the negative electrode).

FIG. 7A is a diagram showing the relationship between the potential V of the negative electrode and the discharge capacity (charge / discharge capacity) Q of the negative electrode.
FIG. 7B is a diagram showing the relationship between dV / dQ (potential change / discharge charge change of the negative electrode) and the discharge capacity (charge / discharge capacity) Q of the negative electrode.
FIG. 8 is a diagram showing the relationship between the potential V of the negative electrode and the Li recoverable amount Q (Ah) in the method for diagnosing the recovery amount of the battery capacity of the secondary battery according to the second embodiment of the present invention.

FIG. 7A is a diagram showing the relationship between the potential V of the negative electrode and the discharge capacity (charge / discharge capacity) Q of the negative electrode as described above.
In FIG. 7A, the vertical axis represents the potential V (open circuit potential, OCP: Open Circuit Potential) of the negative electrode, and the horizontal axis represents the discharge capacity (charge / discharge capacity) Q of the negative electrode. In addition, this discharge capacity is expressed by the value standardized by the current Ah per unit weight (g) of a negative electrode. Further, the region where the discharge capacity is small is the range of high SOC (State Of Charge), and the region where the discharge capacity (charge / discharge capacity) is large is the range of low SOC.
In FIG. 7A, as shown by the characteristic line 701, the potential of the negative electrode has many flat portions with respect to the charging state. Therefore, it can be used as a reference even during discharge.
It is known that the potential of the negative electrode changes depending on the arrangement of lithium between graphite layers, which is the negative electrode material.

The flat potential region on the high SOC side shown in FIG. 7A is referred to as stage 1, and the flat potential region on the intermediate SOC side is referred to as stage 2. Although a flat potential region exists even on the SOC side lower than the stage 2, the flat region is narrow and the potential fluctuates greatly depending on the discharge state, so that it is not suitable as a reference electrode (reference potential).
Therefore, it is preferable to use the stage 1 or stage 2 region (predetermined state) shown in FIG. 7A as a reference for the capacitance recovery electrode.

Stage 1 is _{a two-phase coexistence state called LiC 6 in} which all the graphite layers are filled with lithium and every other layer is filled with lithium. Therefore, the potential of the negative electrode is flat as long as this coexistence is maintained.
Further, in stage 2, the amount of lithium between the graphite layers decreases, and the two-phase coexistence state in which the lithium is clogged every other sheet and the long-range order in the state where the lithium is clogged every other sheet begins to collapse. Is.
These phase changes can be measured as the peak of dV / dQ by the data of dV / dQ obtained by differentiating the potential V of the negative electrode with the discharge capacity Q.

FIG. 7B is a diagram showing the relationship between dV / dQ (change in potential of the negative electrode / change in discharge charge) and discharge capacity as described above. Then, in order to detect the peak of the dV / dQ, it is a figure which shows the relationship between the discharge capacity and dV / dQ.
In FIG. 7B, the vertical axis is dV / dQ and the horizontal axis is the discharge capacity. In addition, this discharge capacity is expressed by the value standardized by the current per unit weight of a negative electrode.
The characteristic line 702 in FIG. 7B shows the relationship between dV / dQ and the discharge capacity.
The characteristic line 702 shows relatively flat characteristics in the region of stage 1 and the region of stage 2. However, there is a peak 703 in which the characteristic line 702 protrudes between the region of stage 1 and the region of stage 2.
The

stages

1 and 2 in FIG. 7B correspond to the

stages

1 and 2 in FIG. 7A.

In FIG. 7A, the region of stage 1 and the region of stage 2 may not be easily discriminated by the characteristic line 701. However, in FIG. 7B, the peak 703 of the characteristic line 702 can be detected relatively easily.
Therefore, the dV / dQ shown in FIG. 7B can be measured first to detect the peak 703, and the area before and after the rise of the peak can be defined as the stage 1 region or the stage 2 region.
Since the region of stage 1 or the region of stage 2 could be clearly grasped by the measurement shown in FIG. 7B, the region of stage 1 or the region of stage 1 in which the characteristics of the potential of the negative electrode are flat by the measurement shown in FIG. 7A, or The potential of the negative electrode is measured in the region of stage 2.

The capacity of the lithium-ion battery decreases as the lithium-ion battery is immobilized on the surface of the negative electrode as charging and discharging are repeated. Then, in the process of this capacity reduction, the potential of the negative electrode (open circuit potential, OCP) changes.
Therefore, when measuring the potential of the capacitance recovery electrode using the negative electrode, it is preferable to periodically measure dV / dQ and always confirm the relationship between the stage 1 and stage 2 regions of the negative electrode and the charge / discharge capacity.

As described above, FIG. 8 is a diagram showing the relationship between the potential of the capacitance recovery electrode and the Li recoverable amount Q (Ah). More specifically, it is a figure which shows an example of the potential measurement result of the capacitance recovery electrode measured with respect to the potential of the stage 1 of the negative electrode.
As described above, the method for diagnosing the amount of recovery of the battery capacity of the secondary battery of the second embodiment of the present invention is a method of measuring the potential of the capacity recovery electrode with reference to the potential of the negative electrode.
In the second embodiment, the same material is used for the positive electrode and the capacity recovery electrode as in the first embodiment.

<< Stage 1 measurement procedure >>
The capacity of the battery cell (secondary battery) decreases due to repeated charging and discharging, and the potential of the negative electrode (open circuit potential, OCP) may change, but the potential of stage 1 of the negative electrode is always maintained by the capacity recovery process. Is in the same position (stage 1) by measuring dV / dQ.
After that, the potential of the capacitance recovery electrode is measured.
Then, the capacitance recovery process is performed again, and further, it is confirmed by dV / dQ measurement that the potential of the negative electrode stage 1 is always at the same position (stage 1).
After that, the potential of the capacitance recovery electrode is measured.
The above measurement is repeated.
As a result of the above measurement, as shown in FIG. 8, it was possible to obtain the result that the potential of the capacitance recovery electrode continuously changes as in FIG. 6 obtained in the first embodiment.
There is a difference that the reference for measuring the potential of the capacitance recovery electrode in FIG. 6 is the positive electrode, whereas the reference for measuring the potential of the capacitance recovery electrode in FIG. 8 is the negative electrode.

<< Stage 2 measurement procedure >>
As described above, a series of potential measurements were performed in the stage 1, but the measurement is not limited to the stage 1.
As shown in FIG. 7B, the same procedure can be measured even in the stage 2 region where the potential characteristics of the negative electrode are flat.
That is, also in stage 2, it is confirmed by dV / dQ measurement that the potential of stage 2 of the negative electrode is at the same position (stage 2). After that, the potential of the capacitance recovery electrode is measured. Then, the capacitance recovery process is performed again, and further, it is confirmed by dV / dQ measurement that the potential of the negative electrode stage 2 is always at the same position (stage 2).
After that, the potential of the capacitance recovery electrode is measured. The above measurement is repeated. As a result of measuring the potential of the capacitance recovery electrode, it is possible to obtain the result that the potential of the capacitance recovery electrode changes continuously as in stage 1.
The description of the measurement data corresponding to FIG. 8 in stage 2 is omitted.
Further, in the measurement of the stage 2, the description overlapping with the stage 1 will be omitted.

<Summary of the second embodiment>
The method for diagnosing the amount of recovery of the battery capacity of the secondary battery of the second embodiment is a method of measuring the potential of the capacity recovery electrode with reference to the potential of the negative electrode.
As shown in FIG. 7B, the relationship between dV / dQ (potential change / discharge charge change of the negative electrode) and discharge capacity is measured, the peak 703 of dV / dQ is detected, and the regions of stage 1 and stage 2 are grasped. ..
Then, using the stage 1 or stage 2 region shown in FIG. 7A as a reference for the capacitance recovery electrode, the potential of the capacitance recovery electrode is measured, and the potential of the capacitance recovery electrode and the Li recoverable amount Q (shown in FIG. 8). Ah) relationship is obtained.
Then, the potential of the capacitance recovery electrode is constantly measured, and the two data are compared and referred to based on the data obtained in FIG. By this method, the Li recoverable amount (capacity recoverable amount) can be grasped, and the charging implementation plan and the discharge limit can be grasped.

<Effect of the second embodiment>
From the above, according to the present invention, it is possible to understand the capacity recoverable amount (Li recoverable amount) by constantly grasping the potential of the capacity recovery electrode, and it is possible to accurately operate the lithium ion battery based on the remaining capacity. Accurate grasp of the value of lithium-ion batteries in planning and secondary use can be easily realized.

<< Other Embodiments >>
The present invention is not limited to the embodiments described above, and further includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with a part of the configuration of another embodiment, and further, add a part or all of the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete / replace.
Hereinafter, other embodiments and modifications will be further described.

《Material for capacity recovery pole》
In the first embodiment and the second embodiment, the same material is used for the positive electrode and the capacity recovery electrode. Therefore, the potential of the capacitance recovery electrode before the recovery process is 0 V.
However, the positive electrode and the capacity recovery electrode are not limited to using the same material. When the same material different for the positive electrode and the capacity recovery electrode is used, the characteristic line shown in FIG. 6 may move, but the relationship between the potential of the capacity recovery electrode (potential reference of the positive electrode) and the Li recoverable amount. Is still obtained, and from its characteristics, a recovery plan can be made by the state of the battery and charging.

<< Fully charged state of positive electrode >>
In the first embodiment, it has been described that when the potential of the positive electrode is used as a reference, the positive electrode in a fully charged state is used as a reference. However, it is not strictly restricted to being fully charged. If the state is close to a fully charged state, the desired accuracy of measurement may be ensured. In some cases, the measurement can be performed in a short time.

<< Other secondary batteries >>
In the description of the first embodiment and the second embodiment, a lithium ion battery (secondary battery) has been described as a target. However, if a secondary battery of another metal having a positive electrode, a negative electrode, and a capacity recovery electrode and having characteristics similar to those described in FIG. 6 and the like is developed, even if it is not a lithium ion battery, the first embodiment Alternatively, the method for diagnosing the amount of recovery of the battery capacity of the secondary battery cell in the second embodiment can be applied mutatis mutandis.

《Solid electrolyte》
In FIGS. 1 and 2, the electrolytic solution of the lithium ion battery (secondary battery) has been described as being a liquid. However, the electrolytic solution of the lithium ion battery (secondary battery) targeted by the method for diagnosing the amount of recovery of the battery capacity of the secondary batteries of the first embodiment and the second embodiment of the present invention is not limited to a liquid. That is, a solid electrolyte may be used instead of the electrolytic solution.
Examples of the solid electrolyte include ionic conductive polymers such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethylmethacrylate, polyhexafluoropropylene, and polyethylene oxide.
When these solid polymer electrolytes are used, the separator 5 shown in FIGS. 1 and 2 can be omitted.

1 Electrode occupied part 11 Positive electrode 12 Negative electrode 15 Capacity recovery electrode 100 cells (battery cell, secondary battery cell, secondary battery)
2 Positive electrode terminal (tab)
3 Negative electrode terminal (tab)
300 Battery pack 350 Charge / discharge device 351 Ammeter 352,358 Voltmeter 353 Resistance 354 Power supply 355 Control unit 356 Charge / discharge changeover switch (switch)
357 Capacity recovery switch (switch)
359 Positive / negative electrode changeover switch (switch)
4 Capacity recovery pole terminal (tab)
5 Separator 6 Exterior material

Claims

A method for diagnosing the amount of recovery of battery capacity of a secondary battery cell having a positive electrode, a negative electrode, and a capacity recovery electrode.
The open circuit potential of the capacity recovery electrode is measured with the electrode potential of the secondary battery cell as the positive electrode or the negative electrode as a reference electrode.
A method for diagnosing the amount of recovery of battery capacity.
In claim 1,
The step of measuring the open circuit potential of the capacitance recovery electrode with the positive electrode as a reference electrode includes a step of fully charging the secondary battery cell before measuring the open circuit potential of the capacitance recovery electrode.
A method for diagnosing the amount of recovery of battery capacity.
In claim 1,
In the step of measuring the open circuit potential of the capacitance recovery electrode with the negative electrode as a reference electrode, the potential of the negative electrode is discharged by V from the discharge process of the secondary battery cell before measuring the open circuit potential of the capacitance recovery electrode. Including a step of measuring dV / dQ with the capacitance as Q and confirming that it is in the two-phase coexistence region of the negative electrode.
A method for diagnosing the amount of recovery of battery capacity.
In claim 1,
In the step of measuring the open circuit potential of the capacitance recovery electrode, a voltage measuring means for measuring the open circuit potential of the capacitance recovery electrode is provided.
A method for diagnosing the amount of recovery of battery capacity.