JP2024008972A - Regenerated lithium ion secondary battery - Google Patents

Abstract

To provide a lithium ion secondary battery regeneration method for enabling reuse of the lithium ion secondary battery itself.SOLUTION: Provided is a lithium ion secondary battery regeneration method including: a preparation step of discharging a consumed lithium ion secondary battery, which is a lithium ion secondary battery on which charging and discharging have been performed a plurality of times, to make a regeneration-prepared lithium ion secondary battery; a first replacement step of replacing a used negative electrode, which is a negative electrode of the regeneration-prepared lithium ion secondary battery, with a lithium supplement electrode containing lithium to make a pre-regeneration processing lithium ion secondary battery; a regeneration step of discharging the pre-regeneration processing lithium ion secondary battery to make a post-regeneration processing lithium ion secondary battery; and a second replacement step of replacing the lithium supplement electrode of the post-regeneration processing lithium ion secondary battery with the used negative electrode or a negative electrode that has not been used to obtain a regenerated lithium ion secondary battery.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for regenerating a lithium ion secondary battery and a regenerated lithium ion secondary battery.

In recent years, with the rise in international environmental awareness, the popularity of environmentally friendly vehicles such as hybrid vehicles and plug-in hybrid vehicles that emit low carbon dioxide is increasing. There is a strong desire to develop a lithium ion secondary battery with excellent output characteristics and charge/discharge cycle characteristics as a battery for environmentally friendly vehicles.

A common type of lithium ion secondary battery is a non-aqueous electrolyte secondary battery. Non-aqueous electrolyte secondary batteries are composed of a positive electrode, a negative electrode, and an electrolyte, etc. The positive and negative electrodes use materials that can intercalate lithium, that is, reversibly insert and desorb lithium ions. It will be done. By placing an electrolyte between the positive electrode and the negative electrode, electrochemical energy can be obtained by utilizing the redox reaction when lithium ions are intercalated and deintercalated at the positive and negative electrodes.

As positive electrode active materials in lithium ion secondary batteries, lithium-cobalt composite oxide (LiCoO _{2 ), which is relatively easy to manufacture, and lithium-nickel composite oxide (LiNiO 2 )} , which uses nickel, which is cheaper than cobalt, are used. , lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, lithium nickel manganese cobalt composite oxide (NMC), lithium nickel cobalt aluminum composite oxide (NCA), etc. Examples include metal composite oxides.

As the negative electrode active material, for automotive use, cost is the most important factor, so inexpensive carbon-based materials can be used, but for battery testing and evaluation, metal lithium, lithium alloys, lithium metal oxides, Alternatively, metals that are alloyed with lithium can also be used.

Furthermore, all-solid-state secondary batteries using solid electrolytes have also recently attracted a lot of attention. An all-solid-state secondary battery is composed of a positive electrode, a negative electrode, and a lithium ion-conducting solid electrolyte, and the active materials for both the positive and negative electrodes are capable of desorbing and inserting lithium ions, as in the case described above. possible materials are used. Among these, all-solid-state batteries that use a lithium metal composite oxide with a layered or spinel-type structure as the positive electrode active material are expected to be batteries with high energy density because they can obtain high voltages of 4.5 V or more. There is.

By the way, as mentioned above, the lithium metal composite oxide used as the positive electrode active material contains a large amount of valuable metals such as lithium, nickel, manganese, and cobalt. For this reason, attempts have been made to recover these valuable metals from lithium ion batteries (consumable lithium ion secondary batteries) that have deteriorated due to long-term use. In particular, backed by an atmosphere that promotes the 3R activities of Reduce, Reuse, and Recycle, consumable lithium ion The need to recover valuable metals from secondary batteries is becoming more and more widespread.

For example, Patent Document 1 describes a first step of adding a mineral acid or a mixture of mineral acid and hydrogen peroxide to a positive electrode active material for a lithium ion secondary battery, and then separating the eluate. A second step of contacting an organic solvent containing a metal extractant to carry out an extraction separation treatment, and a third step of bringing a mineral acid into contact with the organic solvent phase of the extract and carrying out back extraction separation. A method for recovering valuable metals from a positive electrode active material for a lithium ion secondary battery is disclosed.

Patent Document 2 describes a magnetic separation process in which crushed powder of a lithium ion battery obtained by crushing after firing is sieved to a predetermined particle size or less, and then the crushed powder is magnetically sorted into magnetic materials and non-magnetic materials, and lithium A first extraction step of extracting and separating cobalt contained in a positive electrode plate constituting an ion battery in a first acidic solvent, and cobalt contained in a magnetic material sorted by the magnetic separation step and in the first acidic solvent. Disclosed is a method for recovering cobalt in a lithium ion battery, comprising a second extraction step of extracting and separating cobalt contained in an extraction residue floating or precipitated in a second acidic solvent. .

Patent Document 3 describes a disassembly process of disassembling a lithium ion battery, a cleaning process of washing the disassembled battery with alcohol or water to remove electrolyte and electrolyte, and immersing the washed disassembled battery in an aqueous sulfuric acid solution. , a positive electrode active material peeling step of peeling the positive electrode active material from the positive electrode substrate, a leaching step of leaching the peeled positive electrode active material with an acidic solution in the presence of a fixed carbon-containing substance, and neutralization from the obtained leachate to remove aluminum, A neutralization step to separate and remove copper, a nickel/cobalt recovery step to separate and recover nickel and cobalt from the leachate after the neutralization step, and a nickel/cobalt recovery step to concentrate lithium in the remaining aqueous solution by solvent extraction and back extraction. A method for recovering valuable metals from a lithium ion battery is disclosed, which comprises a lithium recovery step of separating and recovering lithium carbonate as a solid.

Patent Document 4 describes a method for leaching valuable metals from a positive electrode active material of a lithium ion battery made of a composite oxide composed of a transition metal containing at least manganese, in which the positive electrode active material is leached in an aqueous solution containing sulfuric acid. The first step is to dissolve the soluble components in the sulfuric acid solution, and the unleached components that remain in the sulfuric acid leaching slurry are removed by adding hydrogen peroxide to the sulfuric acid leaching slurry solution without solid-liquid separation after the first step. A method for leaching a positive electrode active material is disclosed, which includes a second step of further leaching a positive electrode active material.

Patent Document 5 describes a step of preparing a lithium composite precursor from which lithium has been partially extracted electrochemically or chemically, and a step of reacting a lithium compound with the lithium composite precursor from which lithium has been partially extracted. A method for regenerating a lithium composite oxide is disclosed.

Japanese Patent Application Publication No. 10-287864 Japanese Patent Application Publication No. 2004-214025 Japanese Patent Application Publication No. 2007-122885 JP2012-072488A JP2016-085953A

In the 3R activities mentioned above, from the perspective of reducing the consumption of energy such as electricity and heat as well as water and various other resources as much as possible, the first priority is reduce, the second is reuse, The third order is recycling.

However, Patent Documents 1 to 4 each disclose a technique for separating and recovering valuable metals from a positive electrode active material contained in a positive electrode plate of a lithium ion secondary battery. Namely. All of the techniques disclosed in Patent Documents 1 to 4 are limited to those relating to recycling as a last resort, and no consideration has been given to techniques that can reduce and reuse the lithium ion secondary battery itself.

In addition, although Patent Document 5 describes a technique for regenerating a lithium composite oxide by reacting a lithium compound with a lithium composite precursor from which lithium has been partially extracted, the lithium composite oxide that is the positive electrode active material is It is the rebirth of things. In other words, it does not fall under technology that can reduce or reuse the lithium ion secondary battery itself. Moreover, the technique disclosed in Patent Document 5 involves a firing process using a lithium compound, and it cannot be said that energy and resources can be sufficiently reduced. Furthermore, Patent Document 5 does not provide any details on how to recover the lithium composite precursor from which lithium has been partially extracted from the positive electrode plate of a used, consumable lithium ion secondary battery in a solid state. Not yet. In other words, when targeting lithium ion secondary batteries, the technology disclosed in Patent Document 5 is also related to recycling.

In view of the problems of the above-mentioned conventional techniques, one aspect of the present invention aims to provide a method for regenerating a lithium ion secondary battery that allows the lithium ion secondary battery itself to be reused.

According to one aspect of the present invention to solve the above problems,
a preparation step of discharging a depleted lithium ion secondary battery, which is a lithium ion secondary battery that has been charged and discharged multiple times, into a lithium ion secondary battery ready for regeneration;
A first replacement step of replacing the used negative electrode, which is the negative electrode of the regeneration-prepared lithium ion secondary battery, with a lithium replenishment electrode containing lithium to obtain a pre-regeneration lithium ion secondary battery;
a regeneration step of discharging the pre-reprocessed lithium ion secondary battery to obtain a reprocessed lithium ion secondary battery;
a second exchange step of replacing the lithium replenishment electrode of the recycled lithium ion secondary battery with the used negative electrode or an unused negative electrode to obtain a recycled lithium ion secondary battery. Provides a method for recycling batteries.

According to one aspect of the present invention, it is possible to provide a method for recycling a lithium ion secondary battery that allows the lithium ion secondary battery itself to be reused.

1 is a process flow diagram showing a method for regenerating a lithium ion secondary battery according to an embodiment of the present invention. 1 is a schematic diagram showing a regenerated lithium ion secondary battery according to an embodiment of the present invention.

Hereinafter, modes for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments, and the following embodiments may be implemented without departing from the scope of the present invention. Various modifications and substitutions can be made to .
[How to recycle lithium ion secondary batteries]
In considering a method for regenerating a lithium ion secondary battery that allows the lithium ion secondary battery itself to be reused, the inventors of the present invention have identified the mechanism of aging and wear and tear of a lithium ion secondary battery, which is particularly important. , conducted intensive research on the behavior of lithium, which contributes to intercalation reactions. As a result, the main factor that makes the lithium (lithium ion) in lithium ion secondary batteries inactive, that is, turns it into inactive lithium that does not contribute to the intercalation reaction, is the immobilization of lithium due to the occurrence of cation mixing originating from the positive electrode side. It has been found that the following two methods can be mentioned: and lithium immobilization due to the formation of a SEI (Solid Electrolyte Interphase) film originating from the negative electrode side.

Then, by replenishing new lithium to the lithium that no longer contributes to the intercalation reaction due to the above immobilization (hereinafter also referred to as "inactive lithium"), the form as a lithium ion secondary battery is impaired. First, they discovered that it is possible to restore the discharge capacity and regenerate lithium ion secondary batteries, and completed the present invention.

Here, we will first explain the aging and consumption mechanisms of lithium ion secondary batteries.
1. Aging and depletion of lithium ion secondary batteries When charging and discharging lithium ion secondary batteries, an intercalation reaction occurs inside the lithium ion secondary battery in which lithium ions are inserted and desorbed at the positive and negative electrodes. There is. However, when charging and discharging are repeated, inactive lithium that no longer contributes to the intercalation reaction may be generated as described above. Depending on the amount of inert lithium, the charge/discharge capacity of the lithium ion secondary battery may decrease, leading to deterioration and wear and tear.

The main factors for aging and consumption of such lithium ion secondary batteries, that is, the main factors for inactivating the lithium contained in the lithium ion secondary batteries, are included in both the positive electrode side and the negative electrode side. .
(1) Main factors on the positive electrode side First, regarding the positive electrode side, for example, when a positive electrode active material with a high nickel composition ratio is used in a lithium ion secondary battery, a high capacity density can be obtained. The percentage will also increase. Therefore, in space group R-3m of the crystal of the positive electrode active material, for example, cation mixing is likely to occur, in which monovalent lithium ions present at the 3a site and divalent nickel ions present at the 3b site are replaced.

Cation mixing is thought to occur for reasons such as (A) and (B) below. (A) The ionic radius of monovalent lithium ions and the ionic radius of divalent nickel ions are quite close. (B) During the firing process during the production of the positive electrode active material, damage to the positive electrode active material may occur due to an increase in divalent nickel ions due to insufficient oxygen concentration in the furnace, or excessive firing, such as high firing temperature or long firing time. To increase.

When cation mixing occurs, the lithium seat occupancy rate of the positive electrode active material, that is, the proportion of lithium occupying, for example, the 3a site, decreases, and the amount of lithium intercalated and deintercalated during charging and discharging decreases, resulting in a decrease in capacity density. When the lithium site occupancy rate of the positive electrode active material decreases, nickel tends to occupy, for example, the 3a site in space group R-3m instead of lithium, rather than manganese or cobalt. Therefore, lithium that no longer occupies the 3a site occupies the 3b site where nickel was located.

Although the effect of the above-mentioned cation mixing on lithium is partial and limited, on the other hand, for example, lithium that occupies the 3b site instead of nickel ions is immobilized and can hardly contribute to charging and discharging. Becomes inert lithium. Moreover, the metal ions occupying the 3a site instead of lithium are also immobilized, and as a result, the region in which lithium can be inserted into the positive electrode active material is also lost.

Here, we have explained the case of a positive electrode active material with a high nickel composition ratio and a crystal space group of R-3m, but other metals and positive electrode active materials for lithium ion secondary batteries with other space groups are used. Even in this case, cation mixing may similarly occur during repeated charging and discharging, resulting in inactive lithium. In addition, in the following explanation, the case of a positive electrode active material whose crystal space group is R-3m may be explained as an example, but the method for regenerating a lithium ion secondary battery of this embodiment It can be applied not only to a lithium ion secondary battery having a lithium ion secondary battery but also to various lithium ion secondary batteries.
(2) Main factors on the negative electrode side Next, regarding the negative electrode side, when a lithium ion secondary battery is repeatedly charged and discharged, SEI (Solid), a thin film less than 50 nm thick, forms on the surface of the negative electrode. An Electrolyte Interphase) coating is formed. SEI film is a film of lithium fluoride, lithium alkyl carbonate, lithium carbonate, lithium oxide containing lithium, carbon, oxygen, fluorine, phosphorus, silicon, etc., which is formed on the surface of the negative electrode by reductive decomposition of the electrolyte. It is a complex containing multiple inorganic lithium compounds and organic lithium compounds.

Although the SEI film has ionic conductivity, it does not have electronic conductivity, so it plays the role of incorporating a suitable amount of lithium ions into the negative electrode while also suppressing the decomposition of the electrolyte on the negative electrode. For this reason, if there is no SEI coating, the decomposition of the electrolyte will be accelerated and the operation of the battery will eventually stop, so it is preferable that a certain SEI coating be formed.

However, when a lithium ion secondary battery is repeatedly charged and discharged, the thickness of the SEI coating may change. When the thickness of the SEI film becomes thin, the decomposition reaction of the electrolyte may proceed too much. Conversely, as the film thickness increases, electrical resistance increases, and lithium is used in the formation of the SEI film itself, and lithium is captured and immobilized inside the SEI film, resulting in a decrease in charge/discharge capacity. may decrease. When the lithium ion secondary battery is repeatedly charged and discharged in this way, if the thickness of the SEI coating changes, there is a possibility that the battery life and efficiency will be adversely affected. Therefore, in order to improve the performance of a lithium ion secondary battery, it is preferable to stably control the thickness of the SEI coating.

However, the detailed mechanism of SEI film formation is currently unknown and its control is extremely difficult. Therefore, if SEI film evaluation methods advance further and the mechanism is clarified, lithium ion It is believed that this will be of great help in improving the performance of secondary batteries.
(3) Consumable lithium ion secondary battery As described above, when an unused lithium ion secondary battery is used for a long period of time, it is affected by cation mixing on the positive electrode side and SEI film formation on the negative electrode side. , it becomes an old and consumable lithium ion secondary battery. However, once both the cation mixing and the formation of the SEI film occur, the lithium immobilized by them is no longer able to return to its original state, with its function contributing to the intercalation reaction taken away. Therefore, in order to restore and regenerate a depleted lithium-ion secondary battery to the state of an unused lithium-ion secondary battery, it is necessary to replenish the fixed amount of lithium in some way. .

The inventor of the present invention has completed a method for regenerating a lithium ion secondary battery based on the above knowledge. Hereinafter, a method for regenerating a lithium ion secondary battery according to this embodiment will be explained.
2. Method for regenerating a lithium ion secondary battery A method for regenerating a lithium ion secondary battery according to the present embodiment will be described.

The method for regenerating a lithium ion secondary battery according to the present embodiment can be carried out according to the flowchart shown in FIG. 1, and can include the following steps.
A preparation process in which a depleted lithium ion secondary battery, which is a lithium ion secondary battery that has been charged and discharged multiple times, is discharged to become a lithium ion secondary battery ready for regeneration.
A first replacement step in which the used negative electrode, which is the negative electrode of the lithium ion secondary battery prepared for regeneration, is replaced with a lithium replenishment electrode containing lithium to obtain a lithium ion secondary battery before regeneration treatment.
A regeneration process in which a pre-reprocessed lithium ion secondary battery is discharged to become a reprocessed lithium ion secondary battery.
A second exchange step of replacing the lithium replenishing electrode of the recycled lithium ion secondary battery with a used negative electrode or an unused negative electrode to obtain a recycled lithium ion secondary battery.
As mentioned above, according to the studies conducted by the inventors of the present invention, at least a portion of the lithium contained in a consumable lithium ion secondary battery, which is a lithium ion secondary battery that has been charged and discharged multiple times, is located on the positive electrode side. It is fixed by cation mixing and SEI coating on the negative electrode side, and becomes inactive lithium. Therefore, in order to regenerate such a consumable lithium ion secondary battery, it is necessary to replenish the short amount of fixed lithium.

Therefore, the inventor of the present invention investigated a method for replenishing lithium.

As a result, they discovered that by using a lithium replenishment electrode that contains lithium and is capable of supplying and replenishing lithium, it is possible to replenish the immobilized lithium shortage. That is, it has been found that a used negative electrode can be taken out from a depleted lithium ion secondary battery, replaced with a lithium replenishment electrode, and lithium can be replenished using the lithium replenishment electrode.

They also discovered that by replenishing lithium using a lithium replenishment electrode, it is possible to create a regenerated lithium ion secondary battery with restored discharge capacity without damaging the original form of the consumable lithium ion secondary battery.

The method for regenerating a lithium ion secondary battery of the present embodiment can be applied regardless of whether the electrolyte is liquid or solid. Therefore, by using a solid electrolyte, the influence of SEI film formation on the negative electrode side is small, and it is said that deterioration is unlikely to occur.It is also applicable to all-solid-state secondary batteries.

Each step of the method for regenerating a lithium ion secondary battery of this embodiment will be described in detail below. Note that after the name of each step, the step number in FIG. 1 is also shown.
(1) Preparation process (S11)
In the preparation step, a depleted lithium ion secondary battery, which is a lithium ion secondary battery that has been charged and discharged multiple times, can be discharged to become a lithium ion secondary battery ready for regeneration.

In a lithium ion secondary battery, by performing charging and discharging multiple times, a portion of the lithium that contributes to the intercalation reaction is inactivated, and becomes inactive lithium that does not contribute to the intercalation reaction during charging and discharging. The lithium ion secondary battery that has been charged and discharged multiple times has become a consumable lithium ion secondary battery containing the inert lithium.

Therefore, in the preparation step (S11), the depleted lithium ion secondary battery is first discharged, and lithium other than inactive lithium is transferred from the negative electrode to the positive electrode, thereby making it possible to prepare a regeneration-ready lithium ion secondary battery.

As described above, once lithium is inactivated due to cation mixing or the formation of an SEI film, the inactive lithium that is generated will not return to its original state with its function deprived. Furthermore, in cation mixing, for example, in the space group R-3m of the crystal of the positive electrode active material, the area where lithium can be inserted is reduced due to the metal occupying the 3a site instead of the lithium that should be inserted. There is.

Therefore, the purpose of the preparation step is to move lithium other than inactive lithium to a region not affected by cation mixing, for example, in the 3a site, by performing discharge. However, if the consumable lithium ion secondary battery has already been discharged and lithium other than inactive lithium has moved from the negative electrode to the positive electrode, the already performed discharge will be treated as a preparation process and a new preparation process will be started. It is not necessary to carry out.

As mentioned above, the configuration of a consumable lithium ion secondary battery is not particularly limited, and a consumable lithium ion secondary battery may be a lithium ion secondary battery that uses an electrolyte as an electrolyte, or a solid electrolyte as an electrolyte. Any of the so-called all-solid-state batteries used may be used. That is, a consumable lithium ion secondary battery has a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator, and an electrolyte, or a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a solid electrolyte. can have. Note that in either case, it is also possible to further include arbitrary members as necessary.

In addition, the configuration of the positive electrode active material included in the positive electrode of the consumable lithium ion secondary battery is not particularly limited, but in the case of a positive electrode active material that is likely to cause cation mixing especially after being charged and discharged multiple times, the lithium of this embodiment The method for regenerating ion secondary batteries can exhibit particularly high effects. Therefore, the consumable lithium ion secondary battery is equipped with a positive electrode containing a positive electrode active material, and it is preferable that the positive electrode active material contains nickel and cobalt.

As mentioned above, one or more selected from the positive electrode active material and the SEI film formed on the surface of the negative electrode of the consumable lithium ion secondary battery is intercalated during charging and discharging of the consumable lithium ion secondary battery. Contains inert lithium, which is lithium that does not contribute to the reaction. In the positive electrode active material, for example, as described above, inert lithium is contained in the 3b site of the space group R-3m of the crystal of the positive electrode active material.
(2) First exchange step (S12)
In the first replacement step, the used negative electrode, which is the negative electrode of the lithium ion secondary battery prepared for regeneration, is replaced with a lithium replenishment electrode containing lithium, thereby making it possible to obtain a lithium ion secondary battery before regeneration treatment.

In the above preparation step, lithium other than inactive lithium contained in the consumable lithium ion secondary battery is moved to a region not affected by cation mixing, for example, in the 3a site, which is a lithium site. However, in the positive electrode of a consumable lithium-ion secondary battery, the area where lithium such as lithium used for forming the SEI coating itself or lithium immobilized inside the SEI coating was supposed to be inserted is , which remains vacant. In order to insert new lithium into the region of the positive electrode into which lithium can be inserted in the regeneration process described later, it becomes a lithium supply source in place of the used negative electrode, which is the negative electrode used in the consumable lithium ion secondary battery. The purpose of this process is to replace the electrode with a lithium replenishment electrode. Since the lithium replenishment electrode is an electrode for replenishing lithium, it is preferable that it contains lithium. As the lithium replenishment electrode, for example, an electrode having at least one material selected from metallic lithium, lithium alloy, lithium metal oxide, etc. can be used.

Note that lithium replenishment electrodes containing lithium are not generally used in automotive applications due to cost and other reasons, and are used as negative electrode active materials for battery testing and evaluation, such as half-cell performance evaluation of positive electrode active materials. The only thing that happened was that However, the purpose of the above-mentioned lithium replenishment electrode containing lithium is to replenish new lithium to the lithium ion secondary battery, and once replenishment is completed, it must be replaced with the original used negative electrode or an unused negative electrode, as described below. Therefore, even if a lithium replenishment electrode containing such lithium is used, the cost can be sufficiently suppressed.
(3) Regeneration process (S13)
In the regeneration step, the lithium ion secondary battery before the regeneration process can be discharged to become a regenerated lithium ion secondary battery.

Specifically, the pre-recycled lithium ion secondary battery obtained in the first exchange step is discharged, new lithium is transferred from the lithium replenishment electrode to the positive electrode, and a regenerated lithium ion secondary battery is obtained. be able to. In the regeneration process, new lithium ions are supplied from the lithium replenishment electrode by discharging the unregenerated lithium ion secondary battery in which the lithium replenishment electrode is disposed. For this reason, for example, in the space group R-3m of the crystal of the positive electrode active material, new lithium is added to the vacant region of the 3a site that is not affected by cation mixing. can be inserted and replenished.
(4) Second exchange step (S14)
In the second replacement step, the lithium replenishment electrode of the regenerated lithium ion secondary battery is replaced with a used negative electrode or an unused negative electrode to obtain a regenerated lithium ion secondary battery.

Replacing the lithium replenishment electrode of a recycled lithium ion secondary battery with a used negative electrode, which is the original negative electrode used in the depleted lithium ion secondary battery, or with an unused negative electrode to create a recycled lithium ion secondary battery. Can be done.

If the lithium replenishment electrode is used as it is as a negative electrode, lithium dendrites, that is, dendritic lithium precipitates will grow during the long period of repeated charging and discharging, and such precipitates will damage and penetrate the separator, etc. In some cases, internal short circuits may occur. In addition, it is preferable to replace the negative electrode with a used negative electrode or an unused negative electrode since it is a large burden in terms of cost.

As the used negative electrode and the unused negative electrode, an electrode containing carbon can be suitably used. That is, the used negative electrode and the unused negative electrode can contain carbon.

Note that an SEI film may be formed on the surface of the negative electrode used. Therefore, it is preferable to analyze the SEI film in advance and, if there is a problem such as the SEI film being too thick, to replace it with an unused negative electrode. Furthermore, even when it is thought that the capacity of the used negative electrode to store lithium is insufficient, it is preferable to replace it with an unused negative electrode.

The analysis method for the SEI film is not particularly limited, but examples include cross-section polisher processing-field emission scanning electron microscopy (CP-FE-SEM), focused ion beam processing-in-lens scanning electron microscopy (FIB-in-lens SEM), X-ray photoelectron spectroscopy, hard X-ray photoemission spectroscopy (HAXPES), focused ion beam processing-transmission electron microscopy-electron energy loss spectroscopy (FIB-TEM-EELS) In addition to It can be analyzed using analysis/evaluation equipment such as these.

In the second replacement process, if the electrolyte decreases significantly due to decomposition, it is preferable to replenish the electrolyte.For all-solid-state secondary batteries, if the solid electrolyte has deteriorated, replace it with an unused one. It is preferable. In addition, the separator is also inspected as necessary, and if any abnormality is found, it is preferable to replace it with an unused one.

The method for regenerating a lithium ion secondary battery according to the present embodiment has been described in detail above, but this technology is not for regenerating a certain consumable lithium ion secondary battery only once, but for regenerating it multiple times. You can also do it. That is, for example, it is possible to repeat the operation of use → consumption → regeneration → reuse many times for the same lithium ion secondary battery.

In this way, according to the method for regenerating a lithium ion secondary battery of this embodiment, a lithium ion secondary battery can be regenerated any number of times, and the lithium ion secondary battery can be reused.
[Recycled lithium ion secondary battery]
Next, the regenerated lithium ion secondary battery of this embodiment will be explained.

Note that the regenerated lithium ion secondary battery of this embodiment can be manufactured by regenerating a depleted lithium ion secondary battery using the method for regenerating a lithium ion secondary battery described above. For this reason, some of the matters already explained will be omitted.

The regenerated lithium ion secondary battery of this embodiment is a regenerated lithium ion secondary battery in which an unused lithium ion secondary battery is charged and discharged multiple times to become a consumable lithium ion secondary battery, and then regenerated.
The regenerated lithium ion secondary battery of this embodiment contains more lithium than an unused lithium ion battery, and has an active state that contributes to the intercalation reaction during charging and discharging of the regenerated lithium ion secondary battery. The amount of lithium can be made larger than that of a consumable lithium ion secondary battery. Furthermore, the amount of inert lithium that does not contribute to the intercalation reaction can be made equal to or less than the amount of the depleted lithium ion secondary battery.

FIG. 2 is a schematic diagram showing a regenerated lithium ion secondary battery according to this embodiment.

The regenerated lithium ion secondary battery 20 of this embodiment can have a positive electrode 21, a negative electrode 22, and an electrolyte 23. The electrolyte 23 may be an electrolytic solution or a solid electrolyte. Note that, as shown in FIG. 2, a housing 25 that accommodates a separator 24, electrodes, etc. can be provided as necessary.

As mentioned above, in lithium ion secondary batteries, by charging and discharging multiple times, some of the lithium that contributes to the intercalation reaction is inactivated, and some of the lithium that does not contribute to the intercalation reaction during charging and discharging becomes inactive. Becomes active lithium. A lithium ion secondary battery that has been charged and discharged multiple times has become a consumable lithium ion secondary battery containing the above-mentioned inert lithium.

When regenerating a depleted lithium ion secondary battery, first, in the first replacement step described above, the used negative electrode of the depleted lithium ion secondary battery is replaced with a lithium replenishment electrode. Next, in the regeneration step, the insufficient lithium corresponding to the inactive lithium derived from the SEI coating, or in other words, the insufficient lithium corresponding to the inactive lithium other than the one derived from cation mixing at the positive electrode, is replaced with new lithium. Replenish by Thereafter, in a second exchange step, the lithium replenishment electrode is replaced with the original used negative electrode or an unused negative electrode, thereby producing a regenerated lithium ion secondary battery.

Therefore, the regenerated lithium ion secondary battery of this embodiment contains inert lithium 211 generated by cation mixing in the positive electrode 21 by charging and discharging an unused lithium ion secondary battery multiple times. . In addition, the positive electrode 21 further contains new active lithium 212 replenished by the above-mentioned regeneration. Note that FIG. 2 schematically shows inactive lithium 211 and new active lithium 212, and does not mean that these lithiums exist locally as shown in FIG.

In other words, since the regenerated lithium-ion secondary battery finally obtained is further supplemented with lithium during the regeneration process, the amount of lithium it contains (total amount) before being reused as a lithium-ion secondary battery ) exceeds that of an unused lithium-ion secondary battery immediately after its original manufacture. Furthermore, for the same reason, a regenerated lithium ion secondary battery can contain a larger amount of lithium than a depleted lithium ion secondary battery before regeneration. Note that the total amount of lithium here is the sum of active lithium that contributes to the intercalation reaction and inactive lithium.

Furthermore, in the regenerated lithium ion secondary battery, active lithium that contributes to the intercalation reaction is replenished in the regeneration process as described above. Therefore, the amount of active lithium that contributes to the intercalation reaction exceeds that of the exhausted lithium ion secondary battery. However, in a consumable lithium ion secondary battery, some of the lithium sites in the positive electrode are occupied by other metals such as nickel due to cation mixing as described above. Therefore, in the regeneration process, it is not possible to recover the amount of active lithium to the same amount as in an unused lithium ion secondary battery, and the amount of active lithium in a regenerated lithium ion secondary battery is equal to that of an unused lithium ion secondary battery. Less than secondary batteries.

Furthermore, in a regenerated lithium ion secondary battery, the amount of inert lithium can be reduced to less than a consumable lithium ion secondary battery. However, the amount of inert lithium cannot be reduced as much as an unused lithium ion secondary battery that contains almost no inactive lithium, so in a regenerated lithium ion secondary battery, the amount of inert lithium is The use of lithium-ion batteries is increasing.

In addition, in the regenerated lithium ion secondary battery of this embodiment in which a depleted lithium ion secondary battery is regenerated, by replenishing active lithium in the regeneration process as described above, the initial discharge capacity can be increased from the depleted lithium ion secondary battery. It can be made larger than the discharge capacity immediately before the battery is regenerated.

In particular, the discharge capacity recovery rate determined by the following equation (1) can be set to 10% or more.
{(CB)/(AB)}×100(%)...(1)
A: Initial discharge capacity of unused lithium ion secondary battery (mAh/g)
B: Discharge capacity (mAh/g) of a depleted lithium ion secondary battery just before regeneration treatment
C: Initial discharge capacity of recycled lithium ion secondary battery (mAh/g)
The lithium replenishment electrode used to supply new lithium in the regeneration process can be used not only once but many times, and the negative electrode can basically be reused. Therefore, by using the recycled lithium ion secondary battery of this embodiment, the lithium ion secondary battery itself can be reused without disassembling or disassembling the lithium ion secondary battery, reducing new consumption of energy and resources as much as possible. can do.

EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples in any way.

First, a comparative example, which is a blank test for the example, will be described.
[Comparative example 1]
An unused lithium ion secondary battery equipped with a negative electrode having an NMC-based positive electrode active material and a carbon-based negative electrode active material was charged and discharged 2000 times to obtain a consumable lithium ion secondary battery. The NMC-based positive electrode active material is an oxide containing Li, Ni, Mn, and Co as metal elements, and Ni, Mn, and Co are contained in a material amount ratio of Ni:Mn:Co=8:1:1. Contains. Further, the ratio of the amount of Li to metals other than Li is Li/metal=1.05. In addition, a consumable lithium ion secondary battery has a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator, and an electrolyte, and the SEI coating formed on the surfaces of the positive electrode active material and the negative electrode is Contains active lithium. The same applies to other Examples and Comparative Examples below.

In addition, in the consumable lithium ion secondary battery used in this comparative example, lithium other than inactive lithium has already been transferred to the positive electrode, the preparation process has already been carried out, and the lithium ion secondary battery is ready for regeneration. There is. Therefore, here, the following operations after the first exchange step were performed.

The used negative electrode, which is the negative electrode of the lithium ion secondary battery prepared for reproduction, was replaced with a lithium replenishment electrode (first replacement step). An unused carbon-based negative electrode containing no lithium was used as a lithium replenishment electrode to replace the used negative electrode.

Next, a regeneration process was performed by discharging the lithium ion secondary battery before the regeneration process (regeneration process). This resulted in a recycled lithium ion secondary battery.

Then, the lithium replenishment electrode was replaced with the used negative electrode that had been the negative electrode of the lithium ion battery prepared for regeneration, and the electrolyte was also replenished to obtain a regenerated lithium ion secondary battery (second replacement step).

From the initial discharge capacity of an unused lithium ion secondary battery, the discharge capacity of a depleted lithium ion secondary battery just before regeneration processing, and the initial discharge capacity of a recycled lithium ion secondary battery, the following formula (1) is used to calculate the recycled lithium ion The discharge capacity recovery rate of the secondary battery was determined.
{(CB)/(AB)}×100(%)...(1)
A: Initial discharge capacity of unused lithium ion secondary battery (mAh/g)
B: Discharge capacity (mAh/g) of a depleted lithium ion secondary battery just before regeneration treatment
C: Initial discharge capacity of recycled lithium ion secondary battery (mAh/g)
Note that the discharge capacity was determined by setting the current density to the positive electrode to 0.05 mA/cm ² and setting the cutoff voltage to 4 after leaving each battery for about 12 hours after manufacturing and stabilizing the open circuit voltage OCV (open circuit voltage). The discharge capacity was defined as the capacity when the battery was charged to .3V and then discharged to a cutoff voltage of 2.5V after a 10-minute pause. The discharge capacity of the exhausted lithium ion secondary battery immediately before the regeneration process was measured in the same manner at an arbitrary timing after the open circuit voltage became stable.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 2]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Mn, and Co as metal elements, and the ratio of Ni, Mn, and Co is Ni:Mn:Co=6. An NMC-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.04. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 1.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 3]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Co, and Al as metal elements, and the ratio of the amount of Ni, Co, and Al is Ni:Co:Al=9. :0.7:0.3, and the ratio of the amount of Li to metals other than Li was Li/metal=1.01. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 1.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 4]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Co, and Al as metal elements, and the ratio of the amount of Ni, Co, and Al is Ni:Co:Al=8. An NCA-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.02. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 1.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 5]
After the regeneration treatment by discharge, the same procedure as in Comparative Example 1 was performed except that the original negative electrode was not returned and the unused carbon-based negative electrode was used as it was. That is, the second exchange step was not performed, and the regenerated lithium ion secondary battery obtained in the regeneration step was used as a regenerated lithium ion secondary battery.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 6]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Mn, and Co as metal elements, and the ratio of Ni, Mn, and Co is Ni:Mn:Co=6. An NMC-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.04. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative Example 7]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Mn, and Co as metal elements, and the ratio of Ni, Mn, and Co is Ni:Mn:Co=2. :2:6, and the ratio of the amount of Li to metals other than Li was Li/metal=1.05. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative example 8]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Mn, and Co as metal elements, and the ratio of Ni, Mn, and Co is Ni:Mn:Co=2. An NMC-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.05. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative Example 9]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Co, and Al as metal elements, and the ratio of the amount of Ni, Co, and Al is Ni:Co:Al=9. :0.7:0.3, and the ratio of the amount of Li to metals other than Li was Li/metal=1.01. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative Example 10]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Co, and Al as metal elements, and the ratio of the amount of Ni, Co, and Al is Ni:Co:Al=8. An NCA-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.02. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Comparative Example 11]
As a positive electrode active material of an unused lithium ion secondary battery, it is an oxide containing Li, Ni, Co, and Al as metal elements, and the ratio of the amount of Ni, Co, and Al is Ni:Co:Al=7. An NCA-based positive electrode active material was used in which the ratio of Li to metals other than Li was Li/metal = 1.06. Except for the above points, the lithium ion secondary battery was consumed and regenerated in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, as shown in Table 1.
[Example 1]
In Comparative Example 1, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 1 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

In the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to be replaced with the used negative electrode.

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 1.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 64%, as shown in Table 1.
[Example 2]
In Comparative Example 2, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 2 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

In the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to be replaced with the used negative electrode.

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 2.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 73%, as shown in Table 1.
[Example 3]
In Comparative Example 3, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 3 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

In the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to be replaced with the used negative electrode.

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 3.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 12%, as shown in Table 1.
[Example 4]
In Comparative Example 4, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 4 was directly used as It was used as an ion secondary battery.

In the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to be replaced with the used negative electrode.

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 4.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 43%, as shown in Table 1.
[Example 5]
In Comparative Example 5, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 5 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 5.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 80%, as shown in Table 1.
[Example 6]
In Comparative Example 6, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 6 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 6.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 83%, as shown in Table 1.
[Example 7]
In Comparative Example 7, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 7 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 7.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 96%, as shown in Table 1.
[Example 8]
In Comparative Example 8, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 8 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 8.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 90%, as shown in Table 1.
[Example 9]
In Comparative Example 9, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 9 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 9.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 21%, as shown in Table 1.
[Example 10]
In Comparative Example 10, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 10 was directly used as a depleted lithium ion battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation step, first exchange step, regeneration step, and second exchange step were carried out in the same manner as in Comparative Example 10.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 48%, as shown in Table 1.
[Example 11]
In Comparative Example 11, which was positioned as a blank test, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 0%, so the regenerated lithium ion secondary battery of Comparative Example 11 was directly used as a depleted lithium ion secondary battery. It was used as an ion secondary battery.

Then, in the first replacement step, an electrode made of metallic lithium was used as a lithium replenishment electrode to replace the used negative electrode, and in the second replacement step, the lithium replenishment electrode was replaced with an unused carbon electrode. .

Except for the above points, the preparation process, first exchange process, regeneration process, and second exchange process were carried out in the same manner as in Comparative Example 11.

As a result, the discharge capacity recovery rate of the regenerated lithium ion secondary battery was 72%, as shown in Table 1.

空（ブランク）試験の位置付けであった比較例１～比較例１１については、再生リチウムイオン二次電池における放電容量回復率が全て０％であり、供給できる新たなリチウムイオンを含まない未使用の炭素系負極では、リチウム補充用電極として機能しないことが確認できた。

Regarding Comparative Examples 1 to 11, which were positioned as empty (blank) tests, the discharge capacity recovery rate in the recycled lithium ion secondary batteries was all 0%, and the unused lithium ion secondary batteries did not contain new lithium ions that could be supplied. It was confirmed that the carbon-based negative electrode did not function as a lithium replenishment electrode.

On the other hand, for Examples 1 to 11, the discharge capacity recovery rates in recycled lithium ion secondary batteries are distributed in the range of approximately 10% to 100%, and the discharge capacity was recovered in all Examples. I was able to confirm that it does.

Furthermore, in Examples 1 to 4, in which the originally used negative electrodes were returned after the regeneration treatment by discharge, and in Examples 5 to 11, in which unused carbon-based negative electrodes were used, the latter There was a tendency for the discharge capacity recovery rate in the example to be higher.

The cause of this is not yet clear, but in the former case, there is a possibility that lithium is immobilized in the original negative electrode not only due to the formation of the SEI film but also in some form in the negative electrode itself. In other words, the capacity of the used negative electrode to store lithium is lower than that of an unused carbon-based negative electrode, and it is conceivable that the entire amount of lithium cannot be stored even after new lithium is added.

From another perspective, if the discharge capacity recovery rates of the latter Examples 5 and 6 (NMC system) and Examples 9 and 10 (NCA system) are taken as the standard (zero), then the former Examples 1 and 2 It can also be said that the discharge capacity recovery rate of (NMC type) is in the range of -15% to -10%, and the discharge capacity recovery rate of Examples 3 and 4 (NCA type) is in the range of -10% to -5%. Therefore, it can be said that this range corresponds to the capacity at which lithium can no longer be occluded in the negative electrode used.

Note that the regenerated lithium ion secondary batteries obtained in Examples 1 to 11 were supplemented with new active lithium in the replacement process.

Therefore, in all of the regenerated lithium ion secondary batteries obtained in Examples 1 to 11, the amount of lithium contained is lower than that of an unused lithium ion secondary battery or a depleted lithium ion secondary battery before regeneration. It's more than that.

In addition, although the amount of active lithium in these regenerated lithium ion secondary batteries is greater than that of the consumed lithium ion secondary battery before regeneration, it is less than that of an unused lithium ion secondary battery, and the amount of inactive lithium is , more than unused lithium-ion secondary batteries and less than exhausted lithium-ion secondary batteries.

From these results, the method for regenerating a lithium ion secondary battery of this embodiment and the regenerated lithium ion secondary battery exhibit very excellent effects, and save energy and energy without disassembling or disassembling the lithium ion secondary battery. This proves that it is possible to reuse lithium-ion secondary batteries themselves, reducing new consumption of resources as much as possible.

As explained above, the method for regenerating lithium ion secondary batteries and the regenerated lithium ion secondary batteries of this embodiment are suitable for the atmosphere of promoting global 3R activities, and are very environmentally friendly technologies. Furthermore, it is thought that it will play a major role in the future in terms of industrial use.

S11 Preparation process S12 First exchange process S13 Regeneration process S14 Second exchange process

Claims (4)

A regenerated lithium ion secondary battery that is recycled after being charged and discharged multiple times to become a consumable lithium ion secondary battery,
The amount of lithium contained is greater than the unused lithium ion secondary battery,
The amount of active lithium that contributes to the intercalation reaction during charging and discharging of the regenerated lithium ion secondary battery is greater than that of the depleted lithium ion secondary battery,
A regenerated lithium ion secondary battery, wherein the amount of inert lithium that does not contribute to the intercalation reaction is less than or equal to the depleted lithium ion secondary battery. The amount of lithium contained is greater than that of the consumable lithium ion secondary battery,
The amount of active lithium is smaller than the unused lithium ion secondary battery,
The regenerated lithium ion secondary battery according to claim 1, wherein the amount of the inert lithium is greater than the amount of the unused lithium ion secondary battery. The regenerated lithium ion secondary battery according to claim 1 or 2, wherein the initial discharge capacity is larger than the discharge capacity of the depleted lithium ion secondary battery immediately before the regeneration process. The regenerated lithium ion secondary battery according to any one of claims 1 to 3, wherein the discharge capacity recovery rate determined by the following formula (1) is 10% or more.
{(CB)/(AB)}×100(%)...(1)
A: Initial discharge capacity (mAh/g) of the unused lithium ion secondary battery
B: Discharge capacity (mAh/g) of the consumable lithium ion secondary battery immediately before the regeneration process
C: Initial discharge capacity (mAh/g) of the recycled lithium ion secondary battery

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