JP2016149330A - Disposal of used lithium ion batteries - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method for recovering fluorine contained in a used lithium ion battery efficiently.SOLUTION: A processing method of a used lithium ion battery has a thermal decomposition step for thermally decomposing the organic components and the fluorine compound of the battery by heating a used lithium ion battery, a crushing screening step for crushing the heated battery and screening into fine particles and coarse particles, a cleaning elution step for cleaning the fine particles and eluting the fluorine compound contained in the fine particles, a fluorine immobilization step for forming a fluorine-containing precipitation by adding a precipitation agent to the liquid after cleaning containing the eluted fluorine compound, and a separation recovery step for recovering the fluorine-containing precipitation while separating solid and liquid.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for treating a used lithium ion battery, and relates to a treatment method for safely treating and recovering a fluorine compound or the like contained in a lithium ion battery.

  Large-sized lithium ion batteries are used in electric vehicles and electronic devices to supply high-capacity electricity, and the processing of used large-sized lithium ion batteries that occur in large quantities due to the widespread use of electric vehicles and electronic devices becomes a problem. It's getting on.

A lithium ion battery is a secondary battery in which lithium ions in an electrolyte are responsible for electrical conduction. In a typical configuration, graphite is used for the negative electrode active material, lithium cobaltate, lithium nickelate, and lithium manganate are used for the positive electrode active material. The active material used for both electrodes is fixed to a current collector made of a copper or aluminum foil with a fluorine-based binder such as polyvinylidene fluoride (PVDF). In addition, an electrolytic solution in which a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in an organic solvent such as carbonates is mainly used.

Thus, the fluorine compound is used for the lithium ion battery. Fluorine is a harmful environmentally regulated substance, and there are strict regulations on wastewater and exhaust gas. In recycling or disposal of used lithium ion batteries, it is required to appropriately treat fluorine compounds contained in the batteries. Carbonates used in the electrolytic solution are flammable liquids that fall under the fourth category of hazardous materials, and LiPF _{6 as} an electrolyte decomposes to generate toxic hydrogen fluoride. From these points, a safe processing method is required.

  As a method for treating a used lithium ion battery, conventionally, a method of baking the battery in a furnace is known. For example, in Japanese Patent No. 3079285 (Patent Document 1), a lithium ion battery is roasted in a furnace, the roasted product is crushed and separated into a magnetic material and a non-magnetic material, and contains aluminum, copper, or the like. A method for recovering the product is described. Japanese Patent Application Laid-Open No. 10-330855 (Patent Document 2) describes a method in which a lithium ion battery is placed in a furnace at 800 ° C. or higher and an exterior material is ruptured to recover an active material.

As a method for treating an electrolyte contained in a lithium ion battery, a method using a calcium compound is known. For example, Japanese Patent No. 5551166 (Patent Document 3) describes a method of collecting and recovering calcium fluoride by adding slaked lime to an acid leaching solution of a positive electrode active material. Japanese Patent Laid-Open No. 2012-229481 (Patent Document 4) discloses that a lithium ion battery is leached in an alkaline earth metal aqueous solution of calcium or magnesium, and fluorine and phosphorus are hardly soluble in alkaline earth fluoride or alkaline earth. A method of washing and removing these fluorides and phosphates which are converted into phosphates and suspended in the solution is described.
Furthermore, JP 2000-106221 A (Patent Document 5) discloses that a lithium ion battery is crushed and washed with water to elute LiPF ₆ , and a high-temperature acid is added to the solution after washing to add LiPF ₆ to phosphorus. A treatment method is described that decomposes into an acid and fluorine and adds slaked lime to the mixture to recover a mixture of calcium fluoride and calcium phosphate.

Japanese Patent No. 3079285 JP-A-10-330855 Japanese Patent No. 5510166 JP 2012-229481 A JP 2000-106221 A

Since the processing methods of Patent Document 1 and Patent Document 2 mainly recover metals, fluorine is not sufficiently recovered. On the other hand, in the method of Patent Document 3, a Ca compound or the like is added to a leachate obtained by leaching a positive electrode active material of a lithium ion battery with an acidic solution to adjust the pH of the leachate to 2 to 4, and phosphorus or Although it is described that fluorine is removed, fluorine compounds other than LiPF ₆ adhering to the positive electrode active material remain.
Further, the processing methods of Patent Document 4 and Patent Document 5 are methods in which calcium and the like are added to the liquid from which LiPF ₆ is eluted to immobilize fluorine and phosphorus, but the generated solids are calcium fluoride and calcium phosphate. Therefore, there is a problem that it takes time to separate them and it is difficult to reuse them. Further, in the conventional processing method, PVDF fluorine as an electrode binder remains.

This invention solves the said problem in the conventional processing method, and provides the processing method which collect | recovers fluorine efficiently from a used lithium ion battery. In the present invention, not only the fluorine of LiPF ₆ that is an electrolyte but also the fluorine of PVDF that is an electrode binder that has not been targeted by the conventional processing method can be recovered. Since PVDF plays a role of physical adhesion between the current collector and the active material, it is easy to separate the current collector from the active material in the subsequent crushing and sieving step by decomposing. Specifically, according to the present invention, a lithium ion battery is first heat-treated to thermally decompose an organic component and a fluorine compound, whereby a fluorine component of an electrolyte LiPF ₆ and a binder PVDF is simultaneously filtered in one step. Lithium fluoride (LiF). This provides a treatment method that facilitates the separation and recovery of fluorine, and that can recover fluorine efficiently by combining the step of washing and eluting lithium fluoride and the step of fixing fluorine.

The present invention relates to a method for treating a used lithium ion battery having the following configuration.
[1] A thermal decomposition process in which a lithium ion battery is heat-treated to thermally decompose the organic components and fluorine compounds of the battery, and a crushing sieving in which the heat-treated battery is crushed and sieved into fine particles and coarse particles A step of washing, eluting the fluorine compound contained in the fine particle and eluting the fluorine compound, and adding a fixing agent to the post-cleaning solution containing the eluted fluorine compound to produce a fluorine-containing precipitate. A method for treating a lithium ion battery, comprising: a fluorine immobilization step to be performed; and a separation / recovery step to separate and recover the fluorine-containing precipitate by solid-liquid separation.
[2] In the pyrolysis step, the lithium ion battery is heated to 350 ° C. to 600 ° C. in a non-oxidizing atmosphere to thermally decompose and mineralize the organic component, and lithium hexafluorophosphate as an electrolyte and a binder The method of treating a lithium ion battery according to the above [1], wherein the polyvinylidene fluoride is thermally decomposed and the fluorine contained therein is reacted with a lithium compound to form lithium fluoride.
[3] In the crushing and sieving step, the heat-treated battery is crushed and a coarse product mainly composed of fine particles having an average particle diameter of less than 1 mm mainly composed of an active material and a metal foil of a current collector larger than this The method for treating a lithium ion battery according to the above [1] or [2], wherein sieving into granules is performed.
[4] In any one of the above [1] to [3], in the washing and elution step, the fine particles are washed with water to elute lithium fluoride contained in the fine particles, thereby removing fluorine and lithium. A method for treating a lithium ion battery as described.
[5] In the fluorine immobilization step, the calcium compound is used as a fluorine immobilizing agent for the fluorine-containing wastewater discharged from the washing and elution step, and calcium fluoride precipitates are generated in the above [1] to [4] The processing method of the lithium ion battery described in any one.
[6] The lithium ion battery according to any one of [1] to [5] above, wherein lithium is recovered from a liquid fraction obtained by solid-liquid separation of calcium fluoride precipitate, and the treatment liquid is repeatedly used as a cleaning liquid in a cleaning elution process. Processing method.

[Specific description]
The treatment method of the present invention includes a thermal decomposition step of thermally treating a used lithium ion battery to thermally decompose the organic components and fluorine compound of the battery, and crushing the heat-treated battery into fine and coarse particles. Crushing and sieving step for sieving, washing and elution step for washing the fine particles to elute the fluorine compound contained in the fine particles, and adding a fixing agent to the post-washing solution containing the eluted fluorine compound A process for treating a lithium ion battery, comprising: a fluorine immobilization step for generating a fluorine-containing precipitate; and a separation and recovery step for recovering the fluorine-containing precipitate by solid-liquid separation.
An outline of the treatment method of the present invention is shown in FIG.

  The treatment method of the present invention is intended for used lithium ion batteries, lithium ion batteries whose lifetime has passed, lithium ion batteries discarded due to specification changes, lithium ion batteries determined to be defective in the manufacturing process, and the like.

[Pyrolysis process]
In the treatment method of the present invention, first, a thermal decomposition step of heat-treating a lithium ion battery is performed. In the pyrolysis step, the battery is placed in a heating furnace and heated to about 350 ° C. to about 600 ° C., preferably 400 ° C. to 550 ° C. in a non-oxidizing atmosphere. As the non-oxidizing gas, a gas not containing oxygen such as nitrogen, carbon dioxide, argon, superheated steam or the like may be introduced. If it exceeds 600 ° C., the aluminum contained in the battery is melted, and the separation efficiency is lowered in the subsequent sorting step. On the other hand, when the temperature is lower than 350 ° C., PVDF does not decompose and remains as a resin, so that F derived from PVDF cannot be recovered.

In this thermal decomposition step, combustible components such as a resin, an adhesive, a porous polyolefin used as a separator, and an organic solvent of the electrolytic solution contained in the used lithium ion battery are decomposed. In addition, the fluorine component contained in the electrolyte lithium hexafluorophosphate (LiPF ₆ ) and the electrode binder polyvinylidene fluoride (PVDF) reacts with the lithium compound contained in the battery component to form solid lithium fluoride (LiF )become. As a lithium compound contained in the battery, there is an electrolyte LiPF ₆ or a positive electrode active material lithium compound. A positive electrode active material, for example, lithium cobaltate, lithium nickelate, or lithium manganate, is decomposed into an oxide or metal such as cobalt, nickel, or manganese by thermal decomposition, and lithium is taken into the lithium fluoride.

  By this thermal decomposition, 75% to 99% of the fluorine contained in the battery is contained in the thermal decomposition residue as lithium fluoride. On the other hand, the remaining 1% to 25% of fluorine is contained in the pyrolysis gas as hydrogen fluoride. Fluorine in the exhaust gas can be absorbed into water to form a fluorine-containing wastewater, and a calcium compound can be added thereto to precipitate calcium fluoride, which can be solid-liquid separated to recover the fluorine.

[Fracture sieving process]
The battery heat-treated in the pyrolysis step is crushed and sieved into fine and coarse particles. In general, the current collector of the positive electrode is high-purity aluminum, and the current collector of the negative electrode is high-purity copper, and each current collector is a sheet or foil having a thickness of about 10 to 20 μm. Since these sheet or foil current collectors are malleable, they become coarse crushed materials of 1 mm or more. On the other hand, since the active material adhering to the current collector is an aggregate of particles of about 1 to 50 μm, it can be finely crushed into fine crushed material of less than 1 mm. The current collector and the active material can be selected by sieving into fine particles having a size of less than 1 mm and coarse particles having a size larger than 1 mm. Sieve using a vibrating sieve having an aperture of 0.1 to 1.0 mm, preferably 0.15 to 0.5 mm.

  By this crushing and sieving, 90 wt% to 99.5 wt% of the positive electrode active material and the negative electrode active material are contained in the fine particles. On the other hand, the crushed material of the current collector is included in the coarse particles. The coarse particles can be sorted into a light weight mainly made of aluminum and a heavy weight mainly made of copper by specific gravity sorting or the like, and aluminum and copper can be recovered.

[Washing and elution process]
Since lithium fluoride is finely crushed, almost all of the fine particles are contained together with the active material. Since lithium fluoride is chemically stable, it is difficult to remove it by dry method, and it can be removed by elution by wet cleaning.
Therefore, the fine particles thus screened are washed with water to elute lithium fluoride, and the washed liquid containing the eluted lithium fluoride is collected. Since there is no highly soluble substance other than lithium fluoride in the active material coexisting in the fine particles, lithium fluoride can be selectively eluted. As the water washing, general chemical leaching operations such as stirring washing, multistage stirring washing, cake washing and the like can be applied. More than 94% of the fluorine in the fine particles after washing can be removed.

  After washing the fine particles, the liquid is collected and sent to the fluorine fixation process. On the other hand, since the cleaning residue contains oxides or metals such as cobalt, nickel, and manganese derived from the positive electrode active material, these can be recovered from the cleaning residue.

[Fluorine immobilization process]
Since the lithium fluoride is dissolved in the liquid after washing the fine particles and contains fluoride ions and lithium ions, a calcium-based fixing agent is added to the liquid after washing to fluorinate fluorine. Precipitate as calcium fluoride. As the calcium-based fixing agent, slaked lime, quick lime, calcium carbonate, alkaline chemicals containing these, or the like can be used. These are preferable because calcium fluoride is immediately precipitated, and this precipitation is difficult to dissolve in water and can easily fix fluorine in the liquid.

[Separation and recovery process]
The calcium fluoride precipitate is recovered by solid-liquid separation. As solid-liquid separation, a cake having a low water content can be obtained by separating the calcium fluoride precipitate by agglomeration and then separating it into a concentrated slurry, followed by filtration and dewatering with a filter press. In addition to the filter press, dehydration can be performed by centrifugation, vacuum filtration, or a belt press. The recovered calcium fluoride can be used as a raw material for producing hydrofluoric acid when the purity is high, and the calcium fluoride can be used as a raw material for cement.

  Since the liquid component obtained by solid-liquid separation contains lithium ions, lithium can be recovered by a cation exchange resin. The liquid after the treatment can be used as a washing liquid in the repeated washing and elution process.

According to the treatment method of the present invention, fluorine contained in a used lithium ion battery can be efficiently removed, and specifically 94% or more of fluorine can be removed.
In the treatment method of the present invention, the fluorine recovery process can be simplified since the treatment is uniformly performed in a state where different types of fluorine compounds such as a binder and an electrolyte, which are resin compounds, are mixed. Furthermore, since all the fluorine sources contained in the battery are comprehensively processed, the fluorine recovery rate can be increased.
The treatment method of the present invention does not use any special agent, and the treatment after thermal decomposition is easily performed because it is a simple process of crushing sieving, washing and elution, addition of a fluorine fixing agent, and solid-liquid separation. be able to.

Process drawing which shows the outline of the processing method of this invention. 3 is an XRD chart of the thermal decomposition residue of Example 1. FIG. The XRD chart of the active material before thermal decomposition.

  Examples and Comparative Examples of the present invention are shown below. The results of Examples and Comparative Examples are shown in Table 1. The ion concentration was measured by anion chromatography. The pyrolysis residue and active material were analyzed by XRD.

[Example 1]
A used lithium ion battery (LIB) was placed in a heating furnace in a superheated steam atmosphere and heat-treated at 500 ° C. for 1 hour. The thermal decomposition residue of the battery was crushed, and fine particles of 0.5 mm or less were collected. An XRD chart of the fine particles is shown in FIG. As shown in the chart, the pyrolysis residue contains LiF. On the other hand, as shown in the XRD chart (FIG. 3) of the active material before the heat treatment, there is no LiF peak. From this result, it can be confirmed that the fluorine of the fluorine compound contained in LIB became LiF by the heat treatment.
The fluorine concentration contained in the collected fine particles was 4.1 wt%. 15 g of this fine granule (fluorine content: 615 mg) was subjected to a subsequent wet cleaning. In the wet cleaning, pure water was used, and the cleaning was repeated 10 times. The amount of pure water used for one washing was 150 g (liquid / solid ratio = 10/1). The amount of fluorine eluted in the solution after washing 10 times after washing was 580 mg, and the fluorine elution rate indicated by the amount of fluorine eluted with respect to the amount of fluorine in the fine granules was 94.3%.
Subsequently, when 2 L of the washed liquid with a fluorine concentration of 610 ppm was used and 4.0 g of Ca (OH) ₂ was added to the washed liquid, the fluorine concentration in the liquid was 20 ppm. When 3.0 g of Ca (OH) ₂ was additionally added, the fluorine concentration in the liquid became 10 ppm.
The resulting precipitate was recovered by solid-liquid separation. The precipitate was confirmed to be calcium fluoride by XRD analysis. The collected precipitate had a dry weight of 7.56 g, and the recovery rate of fluorine in the fine granules was 92.8%.

[Example 2]
LIB is heat-treated and crushed under the processing conditions shown in Table 1. Fine-grained crushed material is sieved and recovered, washed, and a solidifying agent is added to the solution after washing to produce a precipitate containing fluorine. I let you. The results are shown in Table 1.

[Comparative Example 1]
LIB similar to Example 1 was put into a heating furnace in a superheated steam atmosphere and heat-treated at 500 ° C. for 1 hour. The thermal decomposition residue of the battery was crushed, and fine particles of 0.5 mm or less were collected. 15 g of this fine-grained product (fluorine content: 615 mg) was further heated to 1000 ° C. in the atmosphere and held for 1 hour. When the amount of fluorine in the heating residue was measured, 108 mg of fluorine was volatilized and removed. The fluorine removal rate indicated by the amount of fluorine volatilized with respect to the amount of fluorine in the fine particles is 17.6%, and the fluorine removal rate is low only by heat treatment that volatilizes fluorine, and the fluorine recovery rate is low only by heat treatment. Lower.

[Comparative Example 2]
The used LIB was washed with water and crushed without heat treatment, and fine particles of less than 0.5 mm were collected by sieving. The collected fine particles had a fluorine concentration of 1.9 wt%. 15 g of this fine particle (fluorine content: 285 mg) was subjected to a subsequent wet cleaning. Wet cleaning was performed in the same manner as in Example 1. As a result, the amount of fluorine eluted in the solution after washing by integrating 10 times of washing was 30 mg, and the elution rate of fluorine was 10.5%.

Claims (6)

A thermal decomposition process in which used lithium ion batteries are heat-treated to thermally decompose the organic components and fluorine compounds of the batteries, and a crushing and sieving process in which the heat-treated batteries are crushed and sieved into fine and coarse particles A washing and elution step of washing the fine particles to elute the fluorine compound contained in the fine particles, and adding a fixing agent to the post-washing solution containing the eluted fluorine compound to generate a fluorine-containing precipitate. A method for treating a lithium ion battery, comprising: a fluorine fixing step; and a separation and recovery step of recovering the fluorine-containing precipitate by solid-liquid separation. In the pyrolysis step, the lithium ion battery is heated to 350 ° C. to 600 ° C. in a non-oxidizing atmosphere to thermally decompose the organic component and mineralize, and the electrolyte is lithium hexafluorophosphate and the binder polyfluoride. The method for treating a lithium ion battery according to claim 1, wherein vinylidene is thermally decomposed, and fluorine contained therein is reacted with a lithium compound to form lithium fluoride. In the crushing and sieving step, the heat-treated battery is crushed and a fine particle having an average particle diameter of less than 1 mm mainly composed of an active material, and a coarse particle mainly composed of a metal foil of a current collector larger than this The processing method of the lithium ion battery of Claim 1 or Claim 2 sieved to. The lithium ion battery according to any one of claims 1 to 3, wherein in the washing and elution step, the fine particles are washed with water and lithium fluoride contained in the fine particles is eluted to remove fluorine and lithium. Processing method. In the fluorine fixation step, calcium fluoride is used as a fluorine fixing agent for the fluorine-containing wastewater discharged from the washing and elution step, and calcium fluoride precipitation is generated. A method for treating a lithium ion battery. The method for treating a lithium ion battery according to any one of claims 1 to 5, wherein lithium is recovered from a liquid fraction obtained by solid-liquid separation of calcium fluoride precipitate, and the treatment liquid is repeatedly used as a washing liquid in the washing and elution step.

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