JP2003272720A - Recovery method of lithium cobaltate - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To recover lithium cobalt oxide from a lithium ion secondary battery by a flotation method. It has been extremely difficult to separate lithium cobaltate and graphite in a black powder material recovered after crushing a lithium ion secondary battery. SOLUTION: Since lithium cobaltate in a lithium ion secondary battery is covered with a resin binder such as polyvinylidene fluoride, powder (mixture of lithium cobaltate and graphite) recovered from crushed lithium ion secondary battery ) At a predetermined temperature (about 500 ° C.), the resin binder can be removed.
Lithium cobaltate and graphite from which the resin binder has been removed can be easily separated by a flotation method.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering lithium cobalt oxide from a lithium ion secondary battery, and more particularly to a method for recovering lithium cobalt oxide from a waste lithium ion secondary battery by a floating sorting method. .

[0002]

2. Description of the Related Art A lithium ion secondary battery
(battery, LIB) has a high operating voltage, an excellent discharge and charge cycle, and can be miniaturized, so communication and information devices such as mobile phones, laptop computers, digital cameras, and various AV systems.
It is used in a very wide range of equipment. This lithium-ion battery has a high energy density, excellent charge and discharge cycles, and is lighter in weight than existing batteries, so 199
It has been used as a power source for mobile devices since 0 years. LI
The production of B was about 40 million in 1995, but 2
In 000 years, it increased to more than 10 times, about 470 million.
In recent years, the amount of discarded lithium-ion secondary batteries has increased enormously, and it is necessary to recycle rare resources such as lithium and cobalt contained in the batteries. LI
B contains a large amount of valuable metals such as lithium and cobalt, which are relatively expensive, and is an economically valuable resource. Therefore, recycling research focusing on the recovery of valuable metals is currently active. Has been done.

[0003]

In the existing process,
Generally, a relatively large-scale recycling process, in which a waste lithium-ion secondary battery is treated by a roasting process or a leaching process, has been studied and put into practical use. For example, a method in which lithium cobalt oxide is dissolved by nitric acid and a desired component is precipitated and filtered is disclosed (Japanese Patent Laid-Open No. Hei 10 (1999) -242242).
11-054159 etc.). On the other hand, it is extremely difficult to separate lithium cobalt oxide and graphite (C) in the black powder substance recovered after crushing, and no specific selection method has been proposed. Particularly, the lithium cobalt oxide powder is mixed with a resin binder or a conductive material for increasing the conductivity, which makes the separation difficult. As a result, among the waste lithium-ion secondary batteries, the technology for recovering lithium cobaltate, which has the highest resource value, has not yet been established, and establishment of such technology is important from the resource and industrial viewpoints. Has been regarded as a challenge.

[0004]

The present invention is a method capable of recovering valuable lithium cobalt oxide from LIB with good quality and high yield by a simple process constitution without complicated chemical treatment. Is provided. In the present invention, a black powder substance obtained by mixing lithium cobalt oxide and graphite (C) contained in a waste lithium ion secondary battery is used.
It was possible to separate and collect both by using the floating sorting method. The technology of the present invention for recovering lithium cobalt oxide, which has the highest resource value in a lithium ion secondary battery, by a floating sorting method that is excellent in economic efficiency and operation efficiency is an unprecedented technology. As a characteristic part of the method of the present invention, (1) lithium cobalt oxide and graphite can be separated by a floating sorting method to recover only lithium cobalt oxide, and (2) lithium cobalt oxide and graphite before the floating sorting. The point is that the mixed powder is surface-modified by heat treatment (removal of the binder from the lithium cobalt oxide), and (3) that the effective conditions for such floating selection are carefully examined.

That is, the present invention relates to lithium cobalt oxide (L
This is a method of recovering lithium cobalt oxide from a lithium ion secondary battery (LIB), which comprises heating a mixture of iCoO ₂ ) and graphite at a predetermined temperature and subjecting the mixture to floating selection in water. This predetermined temperature is 350 ° C or higher, preferably 450 ° C or higher, and more preferably 500 ° C.
Above, it is preferable that the temperature is as low as possible within this range, for example, 800 ° C or lower, preferably 600 ° C or lower.
It is preferably not more than a degree. This temperature is especially 500 ℃
The neighborhood is suitable. The heating time depends on the heating temperature, but is 50
It is 1 hour or more, preferably 2 hours or more at around 0 ° C.
At the time of this floating selection, lithium cobalt oxide may be recovered as a precipitate in water.

Further, the water may contain a collecting agent and / or a foaming agent. As the scavenger, oil-based scavengers having hydrocarbon groups (collection oils) such as diesel oil and kerosene (kerosene) and tar oils are preferable. The concentration of addition depends on the concentration of the lithium cobalt oxide powder, but the collector is 100 g / ton (or 100 mg / l) to 320 with respect to the mass of the aqueous solution.
If about 0 g / ton (or 3200 mg / l) is mixed,
It is possible to recover lithium cobalt oxide in high yield (90% or more) and high quality (90% or more). on the other hand,
The foaming agent is preferably an aromatic alcohol-based nonionic flotation agent represented by MIBC (methylisobutylcarbinol) or an unsaturated hydrocarbon-based pine oil, and the addition concentration thereof is 100 g / ton (based on the amount of the aqueous solution). Or 100 mg /
If about 1) is added, it is possible to recover lithium cobalt oxide with an actual yield of 90% or more and quality. Further, at this time, it is possible to recover lithium cobalt oxide by adding only the foaming agent without using the oil-based collector. MI as a foaming agent
Using BC, the added concentration is 100 g / ton (or 1
At the time of 00 mg / l), the actual yield and quality of lithium cobalt oxide were 87.7% and 91.5%, respectively. Further, the mixture of lithium cobalt oxide and graphite may be a residue obtained by separating the separator and the metal from the pulverized product of the lithium ion secondary battery. This separation is preferably done by sieving, especially by vibrating sieving.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A lithium ion secondary battery (LI
B) is generally a composite metal oxide composed of lithium (Li) and cobalt (Co) and an Al current collector in the positive electrode, a carbonaceous material and Cu current collector in the negative electrode, and a lithium salt dissolved in the electrolyte. It is a storage secondary battery using the aprotic organic solvent described above. Using the method of the present invention, such a waste lithium ion secondary battery is crushed, and a mixed powder containing lithium cobalt oxide and graphite, which is finally recovered by sieving, is separated and sorted by a floating sorting method, Highly valuable lithium cobalt oxide can be selectively recovered.

A method for selectively recovering lithium cobalt oxide from a lithium ion secondary battery (LIB) including the method of the present invention comprises the following steps. The process drawing is shown in FIG. (1) The waste lithium ion secondary battery is crushed, the crushed material is sieved, and the oversize is separated into a separator and metals by using an air table. (2) The undersize is screened with a vibrating screen to separate metals, and a black mixed powder containing lithium cobalt oxide and graphite is recovered. (3) This powder (a mixture of LiCoO ₂ and graphite) is heated at about 500 ° C. for a predetermined time. By this step, the binder covering the surface of LiCoO ₂ is removed. (4) By subjecting the powder (mixture of LiCoO ₂ and graphite) thus heat-treated to floating selection,
Lithium cobalt oxide (LiCoO ₂ ) is recovered as a precipitate. By the method described above, it is possible to recover lithium cobalt oxide with a high purity and a high recovery rate from the mixed powder of lithium cobalt oxide and graphite, which has been difficult in the past.

[0009]

The method of the present invention makes it possible to recover lithium cobalt oxide, which has a great resource value, in lithium ion secondary batteries, which are vastly discarded in social activities in recent years, and to recycle rare metal resources. It is considered to have a great influence on the processing. Especially, cobalt and lithium are called rare metals,
Since the resource abundance is scarce, it is considered that recycling from waste has important meaning in resource strategy. Moreover, the flotation method used as a recovery method is
Due to its high economic efficiency and excellent operability, it is expected to be extremely effective for total recycling of lithium ion secondary batteries and to have a great ripple effect. Furthermore, it is expected to be applied as a recovery method for storage batteries other than lithium ion secondary batteries, powder-molded metal materials contained in waste electronic devices, and the like.

[0010]

EXAMPLES The present invention will be illustrated below with reference to Examples, but is not intended to limit the present invention. In the present embodiment, the high frequency inductively coupled plasma (ICP) measurement is made by Seiko Instruments Inc. SPS3000 ICP emission spectroscopic analyzer, and the scanning electron microscope (SEM) is made by Jeol.
JSM-5900LV, and Thermo plus TG 8120 manufactured by Rigaku was used for thermogravimetric-differential heat (TG-DTA) measurement. In this embodiment, a rectangular LIB (46.7 × 28.5 × 4.5) is used.
The metal case from which the resin portion of the outer frame (mm) was removed was treated. The structure of this LIB is shown in FIG. This LIB
Is composed of a composite metal oxide of lithium and cobalt and an Al current collector, and the anode is a carbonaceous material and Cu.
It is composed of a current collector. A separator is present between the cathode and the anode, and Al is mainly used in the case.

First, the waste LIB was crushed for 1 minute using a high-speed rotary crusher. The crushed product is 10 mesh (about 1.65 m
sieving with m), the oversize is separated into a separator and metals (Al, Cu, case, etc.) using an air table, and the undersize uses a vibrating screen of 65 mesh (about 0.21 mm) Then, it was separated into metal (Al, Cu, etc.) and powder (a mixture of LiCoO ₂ and graphite).

The ground waste LIB powder is a mixture of lithium cobalt oxide (LiCoO ₂ ) and graphite. The weight ratio of the crushed waste LIB was 55.9% for the powder (mixture of LiCoO ₂ and graphite) and for the metals (A
(1), Cu, etc.) was 40.3%, and resin-based materials such as separators were 3.7%. Since the surface of pure lithium cobalt oxide is hydrophilic and the surface of graphite is hydrophobic, it is considered that they are easily separated in water, but in reality, both are hydrophobic that float above the water surface. With the nature of. It is considered that this is because the surface of lithium cobalt oxide is covered with a resin binder (conductive polyvinylidene fluoride or the like), so that the surface property is changed from hydrophilic to hydrophobic. L with the binder on the surface
The iCoO ₂ TG-DTA - was investigated by (thermogravimetric differential thermal analysis). The result is shown in FIG. About 200 ℃ to 50
The weight loss up to 0 ° C is due to the removal of the binder,
It is considered that the binder was completely removed at about 500 ° C. That is, by removing the binder adhering to the surface of LiCoO ₂ by heat treatment, LiCoO ₂
It is possible to change the surface property of the from hydrophobic to hydrophilic.

The change in the surface of LiCoO ₂ due to the heat treatment was observed by SEM. The result is shown in FIG. From these photographs, it can be seen that the sample without heat treatment (Fig. 4 (a)) is Li
A large amount of binder is present on the surface of the CoO ₂ particles and between the particles, but due to the increase in the heat treatment temperature (see FIG.
(C)) It can be seen that the binder attached to the LiCoO ₂ surface was gradually removed, and most of the binder was removed in the sample heat-treated at 500 ° C. for 2 hours (FIG. 4D).

Next, the powder (mixture of LiCoO ₂ and graphite) was subjected to floating selection. Kerosene (4 l / ton) was used as the collector, MIBC (methyl isobutyl carbinol, 60 g / ton) was used as the foaming agent, the pulp concentration was 5%, and the floating sorting time was 7 minutes. The effect of the heat treatment temperature on the floating selection of LiCoO ₂ is shown in FIG. 98% of LiCoO _{2 in} the sample whose heat treatment temperature is 350 ° C or less
It is impossible to sort because the above floats, but it is possible to sort 98% or more because the sample treated at 450 ° C. floats about 4% and at 500 ° C. only about 2% floats.

The effect of heat treatment temperature on the floating selection of graphite is shown in FIG. From this figure, graphite does not depend on the heat treatment temperature, and is 99% at any treatment temperature.
It floated over. From these things, Li
It is considered possible to separate CoO ₂ and graphite.

Next, based on the results of the floating sorting so far,
LiCoO_TwoAnd the weight ratio of graphite
The result of the loose selection is shown in FIG. LiCoO_TwoThe weight ratio of 3
When increasing from 0% to 70%, LiCoO_TwoAnd the purity of
The recovery rate is slightly reduced, but the effect is small and the purity is 98
% Or more of LiCoO _TwoCan recover more than 97%
I understand that

Floating sorting was performed by changing the pulp concentration of the ground LIB powder with 5% as a standard. FIG. 8 shows the effect of pulp concentration (ratio of this mixture in the liquid) on the floating selection of the powder (mixture of LiCoO ₂ and graphite) obtained by grinding the waste LIB. Pulp concentration from 3% to 1
Purity and recovery gradually decrease with increasing to 0%,
Even with a pulp concentration of 10%, 92% or more of LiCoO ₂ having a purity of 93% or more could be recovered. Compared to the result of the manual selection method, the purity and recovery rate are lower, but this is due to the metal (Al
It is considered that this is due to the inclusion of (for example).

The main conclusions obtained from the above examples are shown below. 1) Waste LIBs are sorted using a cutting mill, air table and vibrating screen, and resins such as separators, metals (Al, Cu, etc.) and powders (L)
a mixture of iCoO ₂ and graphite). 2) By heat treating LiCoO ₂ at 500 ° C. for 2 hours, its surface property changed from hydrophobic to hydrophilic, and it was possible to separate LiCoO ₂ and graphite by 97% or more by floating sorting. 3) As a result of floating selection of the powder obtained by grinding the waste LIB, 93
92% or more of LiCoO ₂ having a purity of% or more could be recovered.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a LIB in this embodiment.

FIG. 2 is a process drawing of a method for recovering lithium cobalt oxide from a lithium ion secondary battery including the method of the present invention.

FIG. 3 is a view showing a TG-DTA (thermogravimetric-differential thermal analysis) chart of lithium cobalt oxide having a binder on its surface.

FIG. 4 Surface SEM of lithium cobalt oxide by heat treatment
It is a figure which shows a photograph.

FIG. 5 is a diagram showing the effect of heat treatment temperature on floating sorting of LiCoO ₂ .

FIG. 6 is a diagram showing the effect of heat treatment temperature on the floating selection of graphite.

FIG. 7 is a diagram showing the influence of the weight ratio on the floating sorting of LiCoO ₂ and graphite.

FIG. 8 is a diagram showing the effect of pulp concentration on the floating selection of ground LIB.

Continued front page    (72) Inventor Atsushi Shibayama             Akita Prefecture, Akita City             Building 3 F-term (reference) 4D071 AA41 AB13 AB14 AB16 AB17                       AB19 BB12 CA03 DA15                 5H031 BB01 BB02 EE02 EE03 HH06

Claims (6)

[Claims] 1. Lithium cobaltate (LIB) is recovered from a lithium ion secondary battery (LIB), which comprises heating a mixture of lithium cobaltate (LiCoO ₂ ) and graphite at 350 ° C. or higher and subjecting the mixture to floating selection in water. Method. 2. The method according to claim 1, wherein lithium cobalt oxide is recovered as a precipitate in water during the floating sorting. 3. The method according to claim 1, wherein the temperature for heating the mixture is 500 ° C. or higher. 4. The method according to claim 1, wherein the water contains a collecting agent and / or a foaming agent. 5. The method according to claim 1, wherein the mixture of lithium cobalt oxide and graphite is a residue obtained by separating a separator and a metal from a pulverized product of a lithium ion secondary battery. 6. The method of claim 5, wherein the separating is by sieving.