JP5269222B1 - Method for separating and collecting current collector and positive electrode active material from positive electrode material for lithium ion battery - Google Patents

Abstract

The present invention provides a method different from the prior art that can achieve high separation and recovery efficiency of a positive electrode active material and a current collector at low cost.
(A) a step of preparing a positive electrode material for a lithium ion battery having a configuration in which a current collector and a positive electrode active material are bonded with a binder; and (B) a pulverizing medium for the positive electrode material for a lithium ion battery. Using the current collector and the positive electrode active material, and separating the positive electrode material and collecting the positive electrode active material under the sieve at the same time. For separating and recovering the body and the positive electrode active material.
[Selection figure] None

Description

The present invention relates to a method for separating and recovering a positive electrode active material from a positive electrode material for a lithium ion battery.

As one of the techniques for separating the current collector from the positive electrode active material, a method of wet-treating the positive electrode material is known. Japanese Patent Laid-Open No. 10-255862 (Patent Document 1) discloses an electrode of a lithium ion secondary battery. Is immersed in any one of an acidic solution, an alkali metal hydroxide solution, an alkali metal alcohol solution, or an organic solvent to separate the electrode into an electrode material and a current collector. JP-A-2005-327482 (Patent Document 2) discloses a method of cutting a positive electrode plate composed of a positive electrode substrate and a positive electrode active material and immersing and stirring in a sulfuric acid aqueous solution having a pH of 0 to 3, whereby a positive electrode substrate and a positive active material are obtained. Is described as a method for separating and recovering a solid in the form of a solid. Moreover, a method of burning the positive electrode material is known. In Japanese Patent Application Laid-Open No. 10-8150 (Patent Document 3), a metal foil coating waste material is cut into a suitable size, for example, a size of several mm to several tens of mm square with a shredder and the like, and then in an oxygen-containing gas stream By conducting a combustion treatment at 300 to 600 ° C., a conductive agent such as acetylene black or carbon and a binder such as fluororesin or fluororubber mixed in the electrode material of the metal foil coating waste material are selectively used. A method of disassembly and removal is disclosed.

JP-A-10-255862 JP 2005-327482 A Japanese Patent Laid-Open No. 10-8150

  Thus, a technique for separating the current collector and the positive electrode active material is known, but in wet processing using an acid, loss due to elution of Co, Ni, etc., which is a recovered material, and dissolution of Al, which is an impurity, There are drawbacks such as contamination. In the separation method using an organic solvent, the recovery rate is high, but there are problems of removal of the solvent from the recovered positive electrode material and safety in handling the solvent, and a disadvantage of high processing cost. In the method of burning, the positive electrode material is recovered by incineration of an organic material that is a binder (binder). However, the recovery rate is low due to poor peeling of the positive electrode material or entrainment due to melting of Al, and further, there remain problems such as different processing conditions depending on the state of scrap.

  Then, this invention makes it a subject to provide the method different from the prior art which can achieve the high isolation | separation collection efficiency of a positive electrode active material and a collector at low cost.

  As a result of intensive studies to solve the above problems, the present inventor has performed a pulverization process using a pulverization medium on a sieve, so that the positive electrode active material from the positive electrode material can be compared with a shearing process or a cutting process. It has been found that the separation / separation property is remarkably improved, and the current collector can be recovered on the sieve and the positive electrode active material can be recovered with high separation efficiency on the sieve. Further, it has been found that by performing the pulverization process using the pulverization medium on the sieve, the working efficiency is remarkably increased, and the cost merit is very large in performing the industrial operation.

The present invention completed on the basis of the above knowledge, in one aspect,
(A) a step of preparing a positive electrode material for a lithium ion battery having a configuration in which a current collector and a positive electrode active material are bonded with a binder;
(B) Step B-1 for separating the positive electrode material for a lithium ion battery into a current collector and a positive electrode active material using a grinding medium, and separating the separated positive electrode material, and collecting the positive electrode active material under a sieve Performing step B-2 simultaneously;
Is a method for separating and collecting a current collector and a positive electrode active material from a positive electrode material for a lithium ion battery.

  In one embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for a lithium ion battery according to the present invention, the sieve mesh used in Step B-2 is 0.1 to 10 mm.

  In another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for a lithium ion battery according to the present invention, the sieve used in Step B-2 is a vibrating sieve.

  In yet another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for lithium ion batteries according to the present invention, the vibrating sieve is an in-plane vibrating sieve, a three-dimensional vibrating sieve, an ultrasonic vibrating sieve. Or a forced stirring sieve.

  In still another embodiment of the method for separating and recovering the current collector and the positive electrode active material from the positive electrode material for lithium ion batteries according to the present invention, the step B includes the positive electrode material for lithium ion batteries to thermally decompose the binder. After the heat treatment.

  In yet another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for a lithium ion battery according to the present invention, the binder is thermally decomposed on the sieve obtained in step B. After that, the process B is repeated.

  In still another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for lithium ion batteries according to the present invention, the heat treatment is performed at 300 to 650 ° C. for 10 to 240 minutes.

  In still another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the lithium ion battery positive electrode material according to the present invention, the heat treatment results in a weight reduction rate of the positive electrode material of 1 to 12%. Implement in scope.

  In still another embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for a lithium ion battery according to the present invention, the grinding medium is made of a metal used for the positive electrode active material.

  According to the present invention, a positive electrode active material and a current collector can be recovered from a positive electrode material for a lithium ion battery with high separation efficiency. In addition, since the method according to the present invention allows the processing system to be easily configured because pulverization and sieving proceed simultaneously, it is possible to reduce the cost and to use an acidic or alkaline aqueous solution or organic solvent. It is possible to operate with high safety because it can be done dry. Therefore, the present invention provides a method with extremely high industrial utility value for separating and recovering the positive electrode active material from the lithium ion battery positive electrode material.

It is a graph which shows the relationship between the heating time in Example 2, and a weight decreasing rate. It is a graph which shows the relationship between the heating time in Example 2, and collection | recovery Al mixing rate.

In one embodiment of the method for separating and collecting the current collector and the positive electrode active material from the positive electrode material for a lithium ion battery according to the present invention,
(A) a step of preparing a positive electrode material for a lithium ion battery having a configuration in which a current collector and a positive electrode active material are bonded with a binder;
(B) Step B-1 for separating the positive electrode material for a lithium ion battery into a current collector and a positive electrode active material using a grinding medium, and separating the separated positive electrode material, and collecting the positive electrode active material under a sieve Performing step B-2 simultaneously;
including.

<Process (A)>
In step A, a positive electrode material for a lithium ion battery having a configuration in which a current collector and a positive electrode active material are bonded with a binder is prepared. Although not limited, in a general positive electrode material, a positive electrode active material, a binder, and, if necessary, an electrode material containing a conductive agent and an electrolyte are dispersed in a solvent to prepare a positive electrode active material slurry. The positive electrode active material is adhered to one side or both sides of the current collector by applying the slurry onto the current collector and drying it, followed by pressing. The method according to the present invention includes, among other things, a positive electrode material recovered from a used lithium ion battery, a non-standard (off-spec) positive electrode material generated in the manufacturing process, a positive electrode material for sampling inspection processing for quality control, and manufacturing. The scraps generated in the process can be particularly treated.

  The current collector is not limited, but metals such as aluminum, copper, nickel, silver, gold, chromium, iron, tin, lead, tungsten, molybdenum, zinc, or alloys containing these are usually used. Aluminum is often used. The current collector is generally provided in the form of a metal foil. The method according to the present invention can be particularly suitably used for a positive electrode material using aluminum or an aluminum alloy as a current collector.

  The positive electrode active material is not particularly limited as long as it is a known positive electrode active material for a lithium ion battery, but generally any one of cobalt, nickel, manganese, titanium, vanadium, iron and copper in addition to lithium. It is provided in the form of a complex oxide or salt containing one or more.

  Resin is generally used as a binder, but it is not limited, but polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), polyimide, polyamide, polyvinyl acetate, polyvinyl chloride (PVC), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyether nitrile (PEN), polyethylene (PE), polypropylene (PP), polyacrylonitrile (PAN), epoxy resin, polyurethane resin, urea resin, etc. Is mentioned. Typically PVDF is used.

<Process B>
In Step B, the step (B-1) of separating the positive electrode material for a lithium ion battery into a current collector and a positive electrode active material using a grinding medium, and separating the separated positive electrode material, the positive electrode active material is placed under the sieve. The collecting step (B-2) is performed simultaneously.

  In Step B-1, the positive electrode material for a lithium ion battery is separated into a current collector and a positive electrode active material using a grinding medium. Use shearing media where the current collector is shattered by shearing with a shredder, uniaxial crusher, biaxial crusher, etc., and the current collector tends to move under the sieve in the subsequent sieving process. Therefore, the current collector is not reduced so much that the positive electrode active material is separated. Therefore, the separation efficiency between the current collector and the positive electrode active material is high. The pulverizing medium is generally in the form of a lump, and among them, it is preferably a ball shape for reasons of handling and pulverization efficiency.

  The material of the grinding medium is not particularly limited as long as the positive electrode material can be pulverized, but is preferably a material having a hardness suitable for pulverizing the positive electrode material. For example, ceramic, magnetic balls made of alumina, positive electrode active material are preferable. Examples include metals used for materials, but the purity of the recovered positive electrode active material is not adversely affected even if the components of the grinding media are moved under the sieving in the next sieving due to wear or damage. Therefore, it is preferable to use a metal used for the positive electrode active material as a material. For example, any one metal of lithium, cobalt, nickel, manganese, titanium, vanadium, iron, and copper, or an alloy that combines two or more of these metals, or one or more of these metals is used. It is preferable to use a ceramic composed of components.

  The size of the grinding medium is not particularly limited, but if it becomes too large, the number of media that can be used will be small, and the number of parts that come into contact with the positive electrode material for the lithium ion battery will decrease, so the separation efficiency will decrease, but it will be too small. However, since the ball often vibrates below the positive electrode material for the lithium ion battery, the separation efficiency is lowered. Therefore, for example, when a ball-shaped grinding medium is used, the diameter is preferably 5 to 50 mm, and more preferably 10 to 30 mm. Further, balls having different diameters may be used in combination. For example, the size of the balls can be divided into two groups, the diameter of the balls of the first group can be 15-30 mm, and the diameter of the balls of the second group can be 10-15 mm. As a result, the positive electrode material for a lithium ion battery having a large first group of balls can be made fine, and the second group of balls can be effectively peeled off. It is possible to divide the size of the ball into three or more groups, but there is a limit to the effect, so there is no need to divide it excessively.

  For efficient separation operation, it is common to use a plurality of grinding media depending on the size of the grinding device. Illustratively, the number (number) of grinding media relative to the weight (g) of the positive electrode material to be treated can be 0.001 to 100, and typically 0.01 to 10.

  The pulverizing means is not particularly limited as long as the kinetic energy of the pulverizing medium can be transmitted to the positive electrode material, and the positive electrode material can be pulverized. For example, a vibrating sieve is preferable. As vibration sieves, in-plane vibration sieves (eg gyro shifters, reciprocating screens, horizontal or tilting vibratory screens), three-dimensional vibrating sieves (eg round screens, rotex screens), ultrasonic vibrating sieves, forced For example, a three-dimensional vibration sieve or an ultrasonic vibration sieve is preferable because of the large vibration in the vertical direction. The frequency of the vibration sieve is preferably 1 to 100 Hz, and more preferably 20 to 80 Hz. It is also possible to use a ball mill in which a sieve is installed at the discharge port.

  The execution time of the step B-1 depends on the number of vibrations and the number of media, but if it is too short, the separation efficiency is deteriorated. On the other hand, if it is too long, the processing cost increases and the current collector is crushed small. Therefore, considering the separation efficiency of the current collector and the positive electrode active material and the mixing ratio of the current collector, 10 to 120 minutes are preferable, and 30 to 60 minutes are more preferable.

  In Step B-2, the positive electrode material separated into the current collector and the positive electrode active material is sieved, and the positive electrode active material is recovered under the sieve. Normally, the positive electrode active material peeled off from the current collector is soft and powdery, while the current collector is relatively hard and is less likely to be smaller than the positive electrode active material. Therefore, by using a sieve having a predetermined opening, it is possible to recover the positive electrode active material at a high recovery rate while preventing the current collector from being mixed. According to the knowledge of the present inventor, the mesh size of the sieve used in Step B-2 is preferably 0.1 to 10 mm, and more preferably 0.3 to 3 mm.

  In the present invention, in principle, the aperture size indicates the length of one side of a square formed by each sieve mesh. However, in the present invention, the shape of the mesh is not limited to a square, and may be, for example, a rectangle, a diamond, or a circle. Therefore, in the present invention, when the opening dimension is defined as xmm, it means that the sieve has a sieve having substantially the same sieving characteristics as a sieve having an opening dimension xmm according to JIS Z8801-1: 2006. Shall.

  Examples of the sieve that can be used in the step B-2 include a vibrating sieve and a stirring sieve. A sieve having a vibrating sieve structure is preferable. By performing the process B on a sieve, the process B and the process B can be performed simultaneously. Specifically, the process B-1 and the process B-2 are simultaneously performed by using a sieve shaker, a vibration sieve machine, a gyro shifter, or a ball mill in which a sieving machine is installed at the discharge port as described above. It can be carried out continuously. In this case, the positive electrode active material that has been separated from the current collector in step B-1 and pulverized to a size that can pass through the sieve mesh immediately moves under the sieve. Thereby, since the positive electrode active material can move under the sieve before it becomes excessively small, the positive electrode active material is prevented from being excessively pulverized to become fine powder. When it becomes fine powder, it is very easy to dance and adversely affects the environment.

  In the previous stage of carrying out the process B, the positive electrode material can be cut into a size that can be easily processed in accordance with restrictions on the size of the apparatus. For example, it can be sized to pass a square mesh of 0.5 to 50 cm, typically 1 to 20 cm. This can be done with scissors, but a cutter or crusher may be used. However, as described above, it is necessary to be careful because excessively reducing the current collector may increase the mixing rate of the current collector.

<Heat treatment>
The binder used in the positive electrode material varies slightly from manufacturer to manufacturer, and it is often necessary to treat the cathode material from various manufacturers in a mixed state. A more versatile separation / recovery method is required than a separation / recovery method with a narrow adaptation range that cannot be applied.

  The separation and recovery methods described above can be applied to many types of positive electrode materials, but some of them have different binder amounts, different coating methods, and special binders. Some positive electrode materials are difficult to separate current collectors. In such a case, before the step B, it is effective to heat-treat the positive electrode material for a lithium ion battery and thermally decompose the binder. Thereby, even if it is a hard-to-peel positive electrode material, a positive electrode active material and an electrical power collector can be isolate | separated with high separation efficiency.

  In the heat treatment, when the heating temperature is too low, the binder is not sufficiently decomposed, but when the heating temperature is too high, the current collector is oxidized or melted, and becomes brittle. Since the mixing rate is likely to increase, the positive electrode material is preferably heated to 300 to 650 ° C., and more preferably heated to 400 to 600 ° C. The longer the heating time, the more the binder is decomposed. However, if the heating time is too long, the current collector tends to become brittle, so 10 to 240 minutes is preferable, and 20 to 120 minutes is preferable. Further, if the heat treatment is performed at an appropriate heating temperature, a sufficient effect can be obtained even if the heating time is not so long. Therefore, considering the viewpoint of saving energy and shortening the time, the heating time is preferably 20 to 80 minutes, and more preferably 20 to 60 minutes.

  The degree of the heat treatment can be based on the weight reduction rate of the positive electrode material. As the thermal decomposition of the binder proceeds, the weight reduction amount of the positive electrode material increases. If the heat treatment is performed so that the weight reduction amount falls within an appropriate range, a high recovery rate of the positive electrode active material can be achieved while preventing the current collector from being mixed under the sieve. When this is excessive, the current collector tends to be mixed under the sieve. Specifically, although the amount of decrease in the weight of the positive electrode material due to the heat treatment is preferably 1 to 12%, more preferably 3 to 10%, depending on the binder usage status of the lithium ion battery positive electrode material manufacturer.

  As described above, since the separation and recovery method described above can be applied to many types of positive electrode materials, there are many positive electrode materials that do not require heat treatment. In order to carry out the heat treatment, it takes a cost, and therefore it is preferable that the number of positive electrode materials to be heat-treated is as small as possible. Therefore, if the heat treatment is performed only on the positive electrode material in which the positive electrode active material and the current collector cannot be separated by the separation and recovery method described above, the heat treatment is not unnecessarily performed. Specifically, the heat treatment for thermally decomposing the binder is performed on the sieve obtained in the process B, and then the heat treatment is performed only on the minimum necessary positive electrode material by repeating the process B. be able to.

  Examples of the present invention will be described below, but the examples are for illustrative purposes and are not intended to limit the invention.

(Example 1)
Positive electrode materials from various manufacturers were prepared as samples (A to E). In these positive electrode materials, the current collector is an aluminum foil, and the metal components of the positive electrode active material are mainly Li, Mn, Co, and Ni. Each sample of the weight described in Table 1 was cut into a square having a side of 10 to 20 mm with scissors. Subsequently, the positive electrode material was put into a sieve shaker together with the magnetic balls, and the positive electrode active material and the current collector were separated and sieved continuously.

<Electromagnetic sieve shaker>
Manufacturer: Retsch Type: AS200
Amplitude: 2.0 mm
Sieve opening: 0.5 mm
Vibration method: 3D motion Frequency: 3,600 times / min
<Magnetic ball>
Material: Alumina Number of inputs: 10 20 mm diameter, 10 14 mm diameter

The results are shown in Table 1. From Table 1, it can be seen that a high recovery rate of the positive electrode active material was obtained while the sample other than sample A was not heat-treated while preventing the current collector from being mixed. In Table 1, the recovery rate (%) of the positive electrode active material was calculated by the following formula, assuming that the total metal weight of Mn, Co, Ni, and Li under the sieve and under the sieve was 100%.
Positive electrode active material recovery rate = (amount of sieving Mn, Co, Ni, Li) / (amount of sieving Mn, Co, Ni, Li + amount of sieving Mn, Co, Ni, Li)
In addition, the Al content of the recovered product was calculated by the following formula with the total Al weight above and below the sieve being 100%.
Collected Al content = (Sieving Al amount) / (Sieving Al amount + Sieving Al amount)
In addition, the weight of each metal was calculated from the result of analyzing the sample by acid dissolving the ICP.

(Example 2)
Sample A, which had a low separation recovery rate in Example 1, was tested for the effect of heat treatment. The positive electrode material of Sample A was cut into scissors square with a side of 10-20 mm. Subsequently, this positive electrode material was heat-treated at various heating temperatures and heating times shown in Table 2 in an electric furnace. Thereafter, under the same conditions as in Example 1, the positive electrode material and the magnetic balls were put into a sieve shaker, and the positive electrode active material and the current collector were separated and sieved continuously. The shaking time was 30 minutes.

  The results are shown in Table 2. From Table 2, it can be seen that a high recovery rate of the positive electrode active material is obtained in the positive electrode material of Sample A by heat treatment while preventing the current collector from being mixed. Further, FIG. 1 shows the relationship between the heating time and the weight reduction rate, and FIG. 2 shows the relationship between the heating time and the recovered material Al mixing rate.

(Example 3: comparison)
A positive electrode material of Sample C was prepared, and 25.0 g of this positive electrode material was cut into a square having a side of 10 to 20 mm with scissors. Next, after the positive electrode material was pulverized by a ball mill under the following conditions to separate the current collector and the positive electrode active material, the positive electrode material was taken out from the ball mill and put into the sieve shaker used in Example 1 to collect the current collector. The body and the positive electrode active material were sieved for 30 minutes. Table 3 shows the size (diameter: mm) and number of balls used in the ball mill.

<Ball mill>
Manufacturer: Asahi Rika Seisakusho Model: AV-1 type Rotation speed: 130rpm
Rotation time: 120 minutes Ball material: Alumina

(Example 4: comparison)
A positive electrode material of Sample C was prepared, and 25.0 g of this positive electrode material was cut into a square having a side of 10 to 20 mm with scissors. Subsequently, this positive electrode material was directly put into the sieve shaker used in Example 1, and the positive electrode active material and the current collector were separated and sieved for 30 minutes. However, the weight under the sieve was less than 0.1% by mass.

Claims (9)

(A) a step of preparing a positive electrode material for a lithium ion battery having a configuration in which a current collector and a positive electrode active material are bonded with a binder;
(B) Step B-1 for separating the positive electrode material for a lithium ion battery into a current collector and a positive electrode active material using a massive grinding medium, and separating the separated positive electrode material; Performing the step B-2 to be recovered simultaneously;
A method for separating and collecting a current collector and a positive electrode active material from a positive electrode material for a lithium ion battery.   The method according to claim 1, wherein the sieve aperture used in Step B-2 is 0.1 to 10 mm.   The method according to claim 1 or 2, wherein the sieve used in Step B-2 is a vibrating sieve.   The method according to claim 3, wherein the vibrating sieve is an in-plane vibrating sieve, a three-dimensional vibrating sieve, an ultrasonic vibrating sieve, or a forced stirring sieve.   The method as described in any one of Claims 1-4 implemented after heat-processing the positive electrode material for lithium ion batteries in order to thermally decompose a binder.   The method as described in any one of Claims 1-5 which performs the heat processing for thermally decomposing a binder with respect to the sieve obtained by the process B, and repeats the process B after that.   The method according to claim 5 or 6, wherein the heat treatment is performed at 300 to 650 ° C for 10 to 240 minutes.   The method according to any one of claims 5 to 7, wherein the heat treatment is performed in a range in which the weight reduction rate of the positive electrode material is 1 to 12%.   The method according to claim 1, wherein the grinding medium is made of a metal used for the positive electrode active material.