JP6997039B2 - Lithium-ion secondary battery capacity recovery device and capacity recovery method - Google Patents

Description

The present invention relates to a capacity recovery device and a capacity recovery method for a lithium ion secondary battery.

Conventionally, a lithium ion secondary battery has been widely used as a secondary battery having a high energy density. The lithium ion secondary battery has a structure in which a separator is present between the positive electrode and the negative electrode and is filled with a liquid electrolyte (electrolyte solution).

Here, since the electrolytic solution of the lithium ion secondary battery is usually a flammable organic solvent, safety against heat may be a problem in particular. Therefore, a lithium ion solid-state battery using an inorganic solid electrolyte instead of the organic liquid electrolyte has also been proposed (see Patent Document 1).

However, in both the electrolytic solution and the solid electrolyte, the lithium ion secondary battery tends to deteriorate with time and cycle, and its capacity tends to decrease. As a measure to reduce the capacity, it is possible to install a large number of batteries at the beginning, but the situation was inferior in terms of cost performance and energy density.

Here, it has been clarified that one of the main causes of battery deterioration is the deviation of the capacity usage area between the positive electrode capacity and the negative electrode capacity. The displacement of the capacity used area of the lithium ion secondary battery is the portion of the arrow shown in FIG. 1, specifically, the positive electrode capacity used area which is the potential-capacity curve of the positive electrode (V-Ah curve of the positive electrode) and the positive electrode capacity used area. It is the difference from the negative electrode capacity use region which is the potential-capacity curve of the negative electrode (V-Ah curve of the negative electrode). Such displacement of the capacity used area occurs because lithium ions are released from the negative electrode and are deactivated without returning to the positive electrode.

As a method of recovering the capacity decrease due to the displacement of the capacity usage area, a method of introducing lithium ions from the outside into the battery by making a hole in the outer layer can of the battery to release the can and immersing the release part in the electrolytic solution is proposed. (See Non-Patent Document 1, FIG. 5.2).

However, since lithium-ion secondary batteries are very sensitive to oxygen, carbon dioxide, and moisture in the air and have a risk of ignition, this method should be performed only in an environment where there is no air or moisture. It wasn't easy because I couldn't do it.

As another method for recovering the capacity, a method has been proposed in which a lithium metal is inserted into the center of the wound body of the laminate composed of the positive electrode layer, the separator, and the negative electrode layer, thereby replenishing the lithium ions ( Non-Patent Document 1, see FIG. 5.1).

However, if the lithium metal is constantly inserted into the center of the lithium ion secondary battery, the lithium metal reacts with the electrolytic solution and not only the lithium metal itself is consumed, but also the electrolytic solution is consumed, which causes new deterioration. Become.

Japanese Unexamined Patent Publication No. 2000-106154

YE YONGHUANG, A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGA

The present invention has been made in view of the above background art, and an object thereof is to recover the capacity of a battery by replenishing or extracting only lithium ions from the outside while suppressing contact with air or moisture. It is an object of the present invention to provide a capacity recovery device for a lithium ion secondary battery, and a capacity recovery method.

The present inventors provide lithium ion conduction paths (salt bridges) inside and outside the lithium ion secondary battery, respectively, and connect the lithium ion conduction paths when necessary, and only the required amount of lithium ions. We have found that the above-mentioned problems can be solved by supplementing or withdrawing from the outside, and have completed the present invention.

That is, the present invention is a capacity recovery device for a lithium ion secondary battery including a positive electrode, a negative electrode, and a third electrode, the charging / discharging device for charging or discharging the lithium ion secondary battery, and the positive electrode or the positive electrode. The second connection portion includes a detachable first connection portion conductively connected to the negative electrode and a detachable second connection portion conductively connected to the third electrode. It is a capacity recovery device for a lithium ion secondary battery having a lithium ion storage / discharge unit that stores or releases lithium ions.

The surface of the lithium ion storage / discharge unit to be connected to the third electrode may be made of a material capable of conducting lithium ions.

The lithium ion storage / release unit may be formed of at least one selected from the group consisting of lithium metal, lithium aluminum, and a lithium indium alloy.

The second connection may be provided with a protective cap that can be isolated from the outside world.

The protective cap may have a gas release unit that discharges gas generated in the lithium ion storage / discharge unit to the outside of the protective cap.

Another invention is a lithium ion secondary battery connected to the capacity recovery device described above, comprising a positive electrode, a negative electrode, and a third electrode, wherein the third electrode is a solid material capable of conducting lithium ions. It is a lithium ion secondary battery.

The third electrode may be provided with a protective cap that can be isolated from the outside world.

Another invention is a capacity recovery method for a lithium ion secondary battery, wherein a capacity recovery device is connected to a lithium ion secondary battery including a positive electrode, a negative electrode, and a third electrode to recover the capacity. The recovery device includes a charging / discharging device, a first connection portion, and a second connection portion, and the second connection portion has a lithium ion storage / discharge unit that stores or releases lithium ions. A lithium ion secondary by a first connection step of connecting the first connection portion to the positive electrode or the negative electrode, a second connection step of connecting the second connection portion to the third electrode, and the charge / discharge device. Charging / discharging to recover the capacity of the lithium ion secondary battery by charging or discharging the battery and storing lithium ions in the lithium ion storage / discharging unit or releasing lithium ions from the lithium ion storage / discharging unit. A method for recovering the capacity of a lithium ion secondary battery, which includes a step.

In the first connection step, the first connection portion may be connected to the negative electrode, and in the charge / discharge step, the lithium ion secondary battery may be charged.

In the first connection step, the first connection portion may be connected to the positive electrode, and in the charge / discharge step, the lithium ion secondary battery may be discharged.

The second connection step and the charge / discharge step may be performed separately from the outside world.

According to the capacity recovery device of the lithium ion secondary battery of the present invention, lithium ions can be replenished without releasing the outer layer can of the battery. Therefore, contact with air and moisture can be suppressed, and a danger of ignition or the like can be avoided.

Further, since the capacity recovery device of the present invention does not need to be incorporated inside the battery, it is possible to suppress an increase in the volume of the battery itself and avoid a decrease in the energy density of the battery.

Further, according to the capacity recovery device of the present invention, the device can be connected at the required time to recover the required capacity. Therefore, for example, when the lithium ion secondary battery is an in-vehicle battery, it is inspected. You can freely select the time and recover the capacity at the time of vehicle inspection. In addition, it is possible to self-judgment the capacity decrease at home and carry out capacity recovery by oneself.

It is a figure which shows the capacity use area deviation of a lithium ion secondary battery. It is a figure which shows one Embodiment of the lithium ion secondary battery applicable to this invention. It is a figure which applied the capacity recovery device of the lithium ion secondary battery of this invention. It shows one embodiment of the 2nd connection step in the capacity recovery method of the lithium ion secondary battery of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Lithium-ion secondary battery>
The lithium ion secondary battery to which the present invention can be applied is a secondary battery that uses lithium ions as electrolyte ions and realizes charging and discharging by the movement of lithium ions between the positive electrode and the negative electrode. As long as lithium ions are used as the electrolyte ions, the state of the electrolyte is not particularly limited, and it may be an electrolytic solution or a solid electrolyte.

FIG. 2 shows an embodiment of a lithium ion secondary battery applicable to the present invention. FIG. 2 shows a lithium ion secondary battery housed in a square battery case. The battery cell 10 has a negative electrode 1, a positive electrode 2, and a third electrode 3. In the battery cell 10 according to one embodiment, a part of the third electrode 3 exists inside the battery and forms a region 4 inside the battery of the third electrode, whereby the lithium ion conduction path (salt bridge) is formed. ) And the inside of the battery have a large contact area. Further, in the battery cell 10 shown in FIG. 2 according to one embodiment, the third electrode 3 is covered with a protective cap 5a.

[Positive electrode and negative electrode]
The positive electrode and the negative electrode of the lithium ion secondary battery to which the present invention can be applied are not particularly limited, and may function as the positive electrode and the negative electrode of the lithium ion secondary battery.

When the lithium ion secondary battery is a solid-state battery, the positive electrode and the negative electrode constituting the lithium ion secondary battery usually contain an active material and a solid electrolyte, and optionally contain a conductive auxiliary agent, a binder, and the like. For the positive and negative electrodes that make up a solid-state battery, select two types from the materials that can make up the electrodes, compare the charge and discharge potentials of the two types of compounds, and use the one that shows the noble potential as the positive electrode. Any battery is constructed by using a battery showing a potential as the negative electrode.

[Third electrode]
The lithium ion secondary battery to which the present invention can be applied has a third electrode. The third electrode is an electrode member provided so as to be reversibly ionic conductive with the positive electrode and the negative electrode, that is, an electrode that is electrochemically connectable to the positive electrode and the negative electrode.

The third electrode is a lithium ion conduction path (Shiohashi) provided inside the lithium ion secondary battery, and when necessary, the lithium ion conduction path of the capacity recovery device of the lithium ion secondary battery of the present invention. The second connection portion is connected and is used when only a required amount of lithium ion is replenished inside the lithium ion secondary battery or pulled out from the inside of the lithium ion secondary battery.

The material of the third electrode is not particularly limited as long as it is a solid material capable of conducting lithium ions. For example, a substance used as a solid electrolyte of a lithium ion secondary battery can be used as a third electrode. Examples of the solid electrolyte of the lithium ion secondary battery include oxide-based and sulfide-based compounds.

(Protective cap)
The third electrode preferably has a protective cap that can be isolated from the outside world in which air, moisture, and the like are present. When the capacity recovery device of the lithium ion secondary battery of the present invention is not connected to the third electrode, the third electrode is covered with a protective cap to shield it from the outside world such as air and moisture, and when the capacity recovery device is connected. Only it is preferable to release the protective cap. The protective cap can prevent the adhesion of dirt and the like to the third electrode, and can suppress the deterioration of the third electrode by isolating it from the outside world in which air, moisture and the like are present.

[Electrolytes]
The electrolyte of the lithium ion secondary battery to which the present invention can be applied is not particularly limited as long as it can conduct lithium ions between the positive electrode and the negative electrode. The state of the electrolyte is not particularly limited, and it may be an electrolytic solution or a solid electrolyte.

<Capacity recovery device for lithium-ion secondary battery>
The capacity recovery device of the lithium ion secondary battery of the present invention includes a charging / discharging device, a first connection portion, and a second connection portion, and the second connection portion stores or discharges lithium ions. It has a discharge part.

The capacity recovery device of the lithium ion secondary battery of the present invention has a second connection portion which is a lithium ion conduction path (Shiohashi), and the second connection portion and the lithium ion secondary battery are required when necessary. By connecting to the third electrode of the above, only the required amount of lithium ion is replenished in the lithium ion secondary battery or drawn out from the lithium ion secondary battery.

FIG. 3 shows a diagram in which the capacity recovery device of the lithium ion secondary battery of the present invention is applied to the lithium ion secondary battery. The capacity recovery device of the lithium ion secondary battery of the present invention includes a charge / discharge device 7, a first connection portion (in FIG. 3, conductively connected to the negative electrode 1), and a second connection portion 6 (FIG. 3). 3 is conductively connected to the third electrode 3).

[Charging / discharging device]
In the capacity recovery device of the lithium ion secondary battery of the present invention, the charging / discharging device is a device that charges or discharges the lithium ion secondary battery. The charging / discharging device is not particularly limited as long as it can charge or discharge the lithium ion secondary battery.

The capacity recovery device of the lithium ion secondary battery of the present invention replenishes the negative electrode of the lithium ion secondary battery with lithium ions by charging, or extracts lithium ions from the positive electrode and discharges the negative electrode of the lithium ion secondary battery. Extract lithium ions or replenish the positive electrode with lithium ions. In both cases of charging and discharging, the amount of lithium ions can be controlled by the charging / discharging device, that is, the required amount of lithium ions can be replenished or extracted by the charging / discharging device.

[First connection part]
In the capacity recovery device of the lithium ion secondary battery of the present invention, the first connection portion is a detachable portion conductively connected to the positive electrode or the negative electrode of the lithium ion secondary battery. The shape is not particularly limited as long as it can be electrically connected to the positive electrode or the negative electrode and is removable.

[Second connection part]
In the capacity recovery device of the lithium ion secondary battery of the present invention, the second connection portion is a detachable portion conductively connected to the third electrode. The shape is not particularly limited as long as it can be electrically connected to the third electrode and can be attached and detached.

The second connection portion is a lithium ion conduction path (Shiohashi) provided in the capacity recovery device of the lithium ion secondary battery of the present invention, and is a lithium ion conduction path of the lithium ion secondary battery when necessary. It is connected to a third electrode and is used to replenish only the required amount of lithium ions inside the lithium ion secondary battery or to withdraw from the inside of the lithium ion secondary battery.

(Lithium ion occlusion and release section)
The second connection portion has a lithium ion storage / discharge unit that stores or releases lithium ions. The lithium ion occlusal / discharging unit is a portion that occludes or releases lithium ions when recovering the capacity of the lithium ion secondary battery. Specifically, the second connection portion replenishes the negative electrode of the lithium ion secondary battery with lithium ions when charging, or extracts lithium ions from the positive electrode, and when discharging, the lithium ion secondary battery. Lithium ions are extracted from the negative electrode or the positive electrode is replenished with lithium ions.

The material constituting the lithium ion storage and discharge unit is not particularly limited, but for example, a lithium metal, a lithium aluminum alloy, a lithium indium alloy, a metal such as carbon, silicon, germanium, tin, or a non-metal, LiCoO ₂ , Transition metal lithium composite oxides such as LiMnO ₂ , LiNiO ₂ , Li (NiCoMn) O ₂ , Li (NiCoAl) O ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiTi ₄ O ₅ , Li ₄ Ti ₅ O ₁₂ and the like, and At least one lithium ion selected from the group consisting of oxides such as MnO ₂ , SiO, SnO, Fe ₂ O ₃ , Fe ₃ O ₄ , CoO, Co ₃ O ₄ , NiO, RuO ₂ , Cu ₂ O, Cu O and the like. It is preferable to include a storage release material. These lithium ion occlusal and release materials occlude and release lithium ions through the lithium ion conduction path by adding a conductive additive, a binder, etc. as necessary and occluding lithium in advance as necessary. can do.

Further, it is preferable that the surface of the second connecting portion connected to the third electrode is made of a material capable of conducting lithium ions. That is, it is preferable that the material capable of conducting lithium ions is arranged on the outer surface of the lithium ion storage / discharge portion. As a result, it is possible to prevent the lithium ion occluding / discharging portion from coming into direct contact with the outside world, and as a result, it is possible to suppress deterioration due to moisture or the like.

(Protective cap)
It is preferable that the second connection portion is provided with a protective cap that can be isolated from the outside world in which air, moisture and the like are present. When the second connection portion is not connected to the third electrode, the second connection portion is covered with a protective cap to block the outside world such as air and moisture, and the protective cap is released only when the second connection portion is connected to the third electrode. It is preferable to do so. The protective cap can prevent dirt and the like from adhering to the second connection portion, and can suppress deterioration by isolating it from the outside world in which air, moisture and the like are present.

When the second connection part has a protective cap, the structure shall have a gas inlet / outlet for discharging the gas generated in the lithium ion storage / discharge part to the outside of the protective cap and filling the inside of the protective cap with the inert gas. Is preferable. As a result, it is possible to remove the outside air that has inadvertently entered due to the connection operation, and it is possible to avoid contact with air or moisture.

<How to recover the capacity of a lithium-ion secondary battery>
The capacity recovery method of the lithium ion secondary battery of the present invention is a method of connecting the capacity recovery device described above to a lithium ion secondary battery including a positive electrode, a negative electrode, and a third electrode to recover the capacity. It has a connection step, a second connection step, and a charge / discharge step.

[First connection process]
The first connection step in the capacity recovery method of the lithium ion secondary battery of the present invention is a step of connecting the first connection portion in the capacity recovery device of the present invention to the positive electrode or the negative electrode of the lithium ion secondary battery for capacity recovery. Is. In the present invention, either the positive electrode or the negative electrode may be used, and the electrode may be appropriately selected depending on the situation in which capacity recovery is required.

[Second connection process]
The second connection step in the capacity recovery method of the lithium ion secondary battery of the present invention is a step of connecting the second connection portion in the capacity recovery device of the present invention to the third electrode of the lithium ion secondary battery for capacity recovery. Is.

In the present invention, the second connection step is preferably carried out in isolation from the outside world. By isolating it from the outside world where air, moisture, etc. are present, deterioration of both the second connection portion and the third electrode can be suppressed.

FIG. 4 shows an embodiment of the second connection step. In FIG. 4, the second connection portion 6 of the capacity recovery device of the present invention is a laminate of a protective cap 12b provided with a gas inlet / outlet 11 and a solid electrolyte 8 and a lithium ion storage / discharge portion 9 protected by the protective cap 12b. Consists of. Further, the third electrode 3 is composed of a protective cap 12a and a solid electrolyte 8 protected by the protective cap 12a.

In the embodiment shown in FIG. 4, the third electrode 3 and the second connection portion 6 are separated from the outside world in which air, moisture, etc. are present by the protective cap 12a and the protective cap 12b, respectively, before the connection. .. When connecting these in the second connection step, the surface of the protective cap 12a and the protective cap 12b that becomes the connection surface between the third electrode 3 and the second connection portion 6 is released.

In the embodiment shown in FIG. 4, the protective cap 12a and the protective cap 12b are connected to each other by bringing the second connecting portion 6 and the third electrode 3 closer to each other at the portion indicated by the double-headed arrow after releasing the surface to be the connecting surface. .. That is, the second connecting portion 6 is brought close to the third electrode 3 from above, and the solid electrolyte 8 of the second connecting portion 6 and the solid electrolyte 8 of the third electrode 3 are brought into contact with each other to be connected.

At this time, by increasing the inner diameter of the protective cap 12a and the protective cap 12b with respect to the outer diameter of one, the protective cap having a small outer diameter is inserted into the protective cap having a large inner diameter. It is possible to engage the protective caps and connect them. By engaging and connecting the protective caps to each other, it is possible to shield them from the outside world.

Further, in the second connection step in the capacity recovery method of the lithium ion secondary battery of the present invention, there is no problem as long as the second connection portion in the capacity recovery device and the third electrode of the lithium ion secondary battery for capacity recovery are connected. , These may be indirectly connected in addition to being directly connected. For example, a liquid or the like capable of conducting lithium ions may be filled between the second connection portion and the third electrode and connected via the liquid.

In the embodiment shown in FIG. 4, the gas inlet / outlet 11 included in the protective cap 12b of the second connection portion releases the gas generated in the lithium ion storage / discharge unit 9 to the outside of the protective cap 12b, and the inert gas is released to the protective cap 12b. Fill. Examples of the inert gas to be filled include nitrogen gas, argon gas, and helium gas.

[Charging / discharging process]
In the charge / discharge step in the capacity recovery method of the lithium ion secondary battery of the present invention, the lithium ion secondary battery connected to the capacity recovery device by the first connection step and the second connection step is charged or charged by the charge / discharge device. The capacity of the lithium ion secondary battery is restored by discharging and discharging lithium ions into the lithium ion storage / discharge unit or releasing lithium ions from the lithium ion storage / discharge unit.

In the present invention, the charge / discharge step is preferably carried out in isolation from the outside world. By isolating it from the outside world where air, moisture, etc. are present, deterioration of both the second connection portion and the third electrode can be suppressed.

In the charge / discharge step, the lithium ion secondary battery is charged or discharged by the charge / discharge device in the capacity recovery device of the lithium ion secondary battery of the present invention. When charging, the negative electrode of the lithium ion secondary battery is replenished with lithium ions, or when lithium ions are extracted from the positive electrode, and when discharged, lithium ions are extracted from the negative electrode of the lithium ion secondary battery, or to the positive electrode. By replenishing lithium ions, the capacity of the lithium ion secondary battery is restored.

In both charging and discharging, the amount of lithium ions can be controlled by the charging / discharging device, so the charging / discharging time in the charging / discharging step is necessary for replenishing or extracting the required amount of lithium ions. It should be a good time.

[Combination of first connection process and charge / discharge process]
In the capacity recovery method of the lithium ion secondary battery of the present invention, as described above, in the first connection step, the first connection portion is connected to either the positive electrode or the negative electrode of the lithium ion secondary battery for capacity recovery. Then, in the charge / discharge step, charging or discharging is performed.

The combination of the electrode to connect the first connection portion and the charge / discharge can be appropriately selected. However, in the first connection step, the first connection portion is connected to the negative electrode, and in the charge / discharge step, the lithium ion secondary is used. It is preferable that the battery is charged. According to this aspect, the negative electrode can be easily replenished with a required amount of lithium ions.

Further, it is preferable that the first connection portion is connected to the positive electrode in the first connection step, and the lithium ion secondary battery is discharged in the charge / discharge step. According to this aspect, the positive electrode can be easily replenished with a required amount of lithium ions.

[Other processes]
Before carrying out the capacity recovery method of the lithium ion secondary battery of the present invention, carry out an inspection step of inspecting the lithium ion secondary battery for grasping the positive electrode capacity, the negative electrode capacity, and the deviation of the capacity used area. Is preferable. Since the capacity that needs to be recovered is clarified by the inspection step, the degree of recovery by the capacity recovery method of the present invention can be made appropriate.

[Place]
The capacity recovery method of the lithium ion secondary battery of the present invention can be carried out without limitation in place and time because the capacity recovery device can be connected to recover the required capacity when recovery is required. Can be done. For example, when a lithium-ion secondary battery is installed in a car, the capacity can be recovered at the time of inspection or vehicle inspection. It is also possible to equip the home with a capacity recovery device and carry out capacity recovery by itself.

1 Negative electrode 2 Positive electrode 3 3rd electrode 4 Area inside the battery of the 3rd electrode 5a, 5b Protective cap 6 2nd connection part 7 Charging / discharging device 8 Solid electrolyte 9 Lithium ion storage / discharge part 10 Battery cell 11 Gas inlet / outlet 12a, 12b protection cap

Claims (10)

A capacity recovery device for a lithium ion secondary battery including a positive electrode, a negative electrode, and a third electrode.
A charging / discharging device that charges or discharges the lithium ion secondary battery, and
A detachable first connection portion conductively connected to the positive electrode or the negative electrode,
A detachable second connection portion that is conductively connected to the third electrode is provided.
The second connection portion is a capacity recovery device for a lithium ion secondary battery having a laminate of a lithium ion storage / discharge unit that stores or releases lithium ions and a solid electrolyte connected to the third electrode . The lithium ion storage and discharge unit includes a lithium metal, a lithium aluminum alloy, a lithium indium alloy, a metal such as carbon, silicon, germanium, tin, or a non-metal, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , Li (NiCoMn) O ₂ , Li. Transition metal lithium composite oxides such as (NiCoAl) O ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiTi ₄ O ₅ , Li ₄ Ti ₅ O ₁₂ , and MnO ₂ , SiO, SnO, Fe ₂ O ₃ , Fe ₃ The lithium ion according to claim 1 , which comprises at least one lithium ion storage and release material selected from the group consisting of oxides such as O ₄ , CoO, Co ₃ O ₄ , NiO, RuO ₂ , Cu ₂ O, and Cu O. Secondary battery capacity recovery device. The capacity recovery device for a lithium ion secondary battery according to claim 1 or 2 , wherein the second connection portion includes a protective cap that can be isolated from the outside world. The capacity recovery device for a lithium ion secondary battery according to claim 3 , wherein the protective cap has a gas release unit that discharges gas generated in the lithium ion storage / discharge unit to the outside of the protective cap. A lithium ion secondary battery connected to the capacity recovery device according to any one of claims 1 to 4 .
Equipped with a positive electrode, a negative electrode, and a third electrode,
The third electrode is a lithium ion secondary battery, which is a solid material capable of conducting lithium ions. The lithium ion secondary battery according to claim 5 , wherein the third electrode includes a protective cap that can be isolated from the outside world. It is a capacity recovery method of a lithium ion secondary battery in which a capacity recovery device is connected to a lithium ion secondary battery provided with a positive electrode, a negative electrode, and a third electrode to recover the capacity.
The capacity recovery device includes a charging / discharging device, a first connection portion, and a second connection portion.
The second connection portion has a laminate of a lithium ion storage / discharge unit that stores or releases lithium ions and a solid electrolyte that is connected to the third electrode .
The first connection step of connecting the first connection portion to the positive electrode or the negative electrode, and
A second connection step of connecting the second connection portion to the third electrode, and
The lithium ion secondary battery is charged or discharged by the charge / discharge device, and the lithium ion is stored in the lithium ion storage / discharge unit or the lithium ion is released from the lithium ion storage / discharge unit. A method for recovering the capacity of a lithium ion secondary battery, which comprises a charge / discharge step of recovering the capacity of the secondary battery. In the first connection step, the first connection portion is connected to the negative electrode.
The method for recovering the capacity of a lithium ion secondary battery according to claim 7 , wherein the lithium ion secondary battery is charged in the charge / discharge step. In the first connection step, the first connection portion is connected to the positive electrode, and the first connection portion is connected to the positive electrode.
The method for recovering the capacity of a lithium ion secondary battery according to claim 7 , wherein in the charging / discharging step, the lithium ion secondary battery is discharged. The method for recovering the capacity of a lithium ion secondary battery according to any one of claims 7 to 9 , wherein the second connection step and the charge / discharge step are carried out in isolation from the outside world.

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