JP2015026566A - Method of peeling carbon from copper foil surface of negative electrode sheet of lithium ion battery and peeling agent for use in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering a valuable metal, with which cost of recycle is significantly improved by peeling carbon, which is an active material, from a copper foil surface of a negative electrode sheet of a lithium ion battery with a simple method and recovering a copper foil having high purity and the carbon.SOLUTION: Provided is a method of peeling carbon, which is an active material, from a copper foil surface of a negative electrode sheet of a lithium ion battery, with which cost of recycle is significantly improved by peeling the carbon from the copper foil surface of the negative electrode sheet of the lithium ion battery using a peeling agent, whose active ingredient is a nonionic surfactant, a cationic surfactant, or an amphoteric surfactant except for an anionic surfactant, and recovering a copper foil having high purity and the carbon. Also provided is a carbon peeling agent for use in the method.

Description

  The present invention makes it easy to peel off active material carbon from the surface of the copper foil of the negative electrode sheet of a lithium ion battery, and to separate and collect the copper foil and carbon with high purity, respectively. The present invention also relates to a carbon stripping agent and a stripping method from a copper foil surface, which can greatly improve the economic cost.

  Generally, copper foil is used for the negative electrode sheet which is a negative electrode material of a lithium ion battery, and 30 to 70 mass percent of carbon graphite (hereinafter referred to as “carbon”) is used as an active material on the surface of the copper foil. Is attached. Therefore, when valuable copper is to be recovered from the negative electrode sheet of the used lithium ion battery, it is necessary to separate carbon that is firmly attached to the copper foil surface.

  In order to remove carbon from the surface of the copper foil, for example, there is a method in which a copper foil with carbon attached to the surface is recovered as crude copper by melting copper in a blast furnace after pulverization. However, even when processing in a blast furnace, copper having a high melting point must be heated to a high temperature, so that a very large energy is required unlike a metal having a low melting point such as aluminum. In addition, the melting equipment is required to be a furnace that can withstand high temperatures. Furthermore, when obtaining crude copper, a large amount of carbon or the like that becomes slag is generated, which must be removed in large quantities.

  Also, although the copper foil before melting was originally high-purity copper, the crude copper obtained after melting has low purity, and in order to further increase this, a refining process to remove impurities such as oxygen is necessary. After melting, electrolytic refining must be performed for high purity. In this way, high-purity copper and crude copper after refining, in addition to their characteristics, take account of the refining process in addition to the transaction price, so the purity of high-purity copper is much higher than that of crude copper. It is very expensive.

  However, there are circumstances different from general scrap scraps, and it is not easy to melt the copper foil material of the negative electrode sheet in an electric furnace. In general, an electric furnace uses heat generated by electric resistance as a main heat source. However, the high-purity copper foil used for the electrodes has low electrical resistance, and carbon with extremely high electrical conductivity is attached to the surroundings. This is because copper does not melt. Therefore, in the case of melting treatment in an electric furnace, it is in a situation where an extra step such as adding a pretreatment step such as scraping carbon from the copper foil surface in advance and then putting it into the electric furnace is forced. .

  Further, even when copper is recovered by smelting as described above, a gas containing toxic fluorine may be generated from the binder used for bonding the copper foil of the negative electrode sheet of the lithium ion battery and carbon. . Therefore, from the viewpoint of environmental load, it is not preferable to melt easily.

  Therefore, as a separation method other than melting, for example, a copper foil in a negative electrode of a lithium ion battery is oxidized through the following steps to obtain copper oxide, which is then dissolved in a sulfuric acid aqueous solution and separated after recovery. Such a method is disclosed. (For example, refer to Patent Document 1.)

  In this conventional method, first, as a pre-stage of copper recovery, a lithium ion battery is immersed in an aqueous solution containing an electrolyte and discharged to destroy its function as a battery, and then cut to obtain an aluminum and stainless steel casing and electrode. After removing the terminal, the electrolyte solution and the organic bonding material are removed by immersing the mixture including the positive electrode material, the negative electrode material, and the separator in water. Then, after several steps, the separated solid is dissolved in a sulfuric acid aqueous solution by a rotary separator, and further leached while adding a hydrogen peroxide aqueous solution. Then, manganese, cobalt, nickel, and graphite contained in the positive electrode material are eluted as an aqueous solution on the undersize side of the rotary separator.

  Further, copper contained in the negative electrode material is leached into a sulfuric acid aqueous solution in the form of copper oxide by aeration oxidation. Further, after filtering these, it is separated into an aqueous solution containing manganese, cobalt, nickel, and copper and a leach residue containing graphite as a main component, and a resin is recovered on the oversize side of a rotary separator, This is a method for recovering metal.

  However, the recovery method described in Patent Document 1 requires refining, unlike the method of directly peeling the copper foil from the negative electrode material and collecting the peeled copper foil. Further, since the metal is eluted in the aqueous solution, the aqueous solution has to be disposed of after each use, and the amount of the molten metal melted is large, and the load of waste liquid treatment is also large.

JP 2010-277868 A

  Problems to be solved by the present invention are as follows: (1) By immersing the negative electrode sheet material of a lithium ion battery in a solution of a release agent, the copper foil and the carbon on the surface of the copper foil are easily peeled off without melting. (2) A copper foil with high purity can be obtained in a solid state without requiring refining, etc., and the copper foil and carbon can be separated, and both the copper foil and carbon can be recovered for reuse. (3) By repeatedly using the stripping solution, it is possible to reduce the environmental burden due to stripping, separation, recovery and disposal, and to greatly improve the cost. Therefore, the present invention provides a method for easily realizing separation of copper foil and carbon from the negative electrode sheet material, a method for easily separating and recovering both copper foil and carbon, and It aims at providing the peeling agent to be used.

  The first means of the present invention for solving the above-mentioned problem is to peel off the negative electrode sheet material for lithium ion batteries having carbon attached to the copper foil surface, containing an aqueous solution containing hydroxide and a surface active component. Peeling of carbon on the surface of the copper foil, wherein the carbon attached to the surface of the copper foil of the negative electrode sheet material is peeled off by dipping in a tank, and the copper foil and carbon can be separated and recovered. Is the method.

  According to a second means of the present invention, a negative electrode sheet material for a lithium ion battery in which carbon is attached to a copper foil surface, an aqueous solution containing a hydroxide and a surface active component and having a liquid temperature of 20 ° C. or higher and lower than 90 ° C. The carbon on the copper foil surface is characterized in that it is immersed in a peeling tank and the carbon adhering to the surface of the copper foil of the negative electrode sheet material is peeled off while stirring to separate and collect the copper foil and carbon. It is a peeling method.

  According to a third means of the present invention, the surfactant component in the aqueous solution is at least one interface selected from any one of nonionic surfactants, cationic surfactants and amphoteric surfactants. It is the carbon peeling method on the copper foil surface according to the first or second means of the present invention, which contains an activator as an active ingredient.

  According to a fourth means of the present invention, in any one of the first or second means of the present invention, the surface active component in the aqueous solution is polyoxyethylene alkyl ether or polyoxyethylene alkyl phenyl ether. It is the peeling method of the carbon on the copper foil surface of description.

  According to a fifth means of the present invention, the hydroxide in the aqueous solution contains at least one hydroxide selected from potassium hydroxide, sodium hydroxide and lithium hydroxide. A method for peeling carbon on a copper foil surface according to any one of the first to fourth aspects of the invention.

  According to a sixth means of the present invention, in any one of the first to fifth aspects of the present invention, the hydroxide in the aqueous solution further contains at least one of or both of a phosphate and a silicate. This is a carbon peeling method on the surface of the copper foil described in the above means.

  According to a seventh means of the present invention, there is provided a negative electrode sheet material for a lithium ion battery in which carbon is adhered to a copper foil surface in a peeling tank containing the aqueous solution according to any one of the first to sixth aspects of the present invention. Then, the sheet material taken out is washed with water in a washing tank and dried to recover the copper foil. On the other hand, carbon dispersed in the aqueous solution in the peeling tank and the washing water in the washing tank is filtered and dried to obtain carbon. This is a copper foil and carbon recycling method for collecting powder and separating and collecting copper foil and carbon.

  The eighth means of the present invention is a carbon release agent that adheres to the copper foil surface of a negative electrode sheet material for a lithium ion battery, comprising an aqueous solution containing a hydroxide and a surface active component.

  According to a ninth means of the present invention, the surfactant component is at least one surfactant selected from a nonionic surfactant, a cationic surfactant and an amphoteric surfactant. A release agent for carbon adhering to the copper foil surface of the negative electrode sheet material for a lithium ion battery according to the eighth means of the present invention.

  The tenth means of the present invention is the negative electrode sheet for lithium ion batteries according to the eighth means of the present invention, wherein the surface active component is polyoxyethylene alkyl ether or polyoxyethylene alkylphenyl ether. It is a carbon release agent that adheres to the copper foil surface of the material.

  The eleventh means of the present invention is characterized in that the hydroxide contains at least one hydroxide selected from potassium hydroxide, sodium hydroxide and lithium hydroxide. A release agent for carbon adhering to the copper foil surface of the negative electrode sheet material for a lithium ion battery according to any one of 8 and 9.

  The twelfth means of the present invention is characterized in that the hydroxide in the aqueous solution further contains at least one of or both of a phosphate and a silicate. It is a carbon release agent that adheres to the copper foil surface of the negative electrode sheet material for a lithium ion battery on the copper foil surface according to any means.

  The hydroxide is soluble in an aqueous solution. For example, in the present invention, any one of potassium hydroxide, sodium hydroxide, and lithium hydroxide is preferable.

  Examples of suitable surfactant components include nonionic surfactants, cationic surfactants, and amphoteric surfactants. It shall contain at least one surfactant selected from any of these systems. In addition, since this peeling agent is a mixture with the aqueous solution of hydroxide, an anionic surfactant may not necessarily be suitable in relation to the dissolution equilibrium.

  Examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts and the like.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkylphenyl ether, sucrose fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyethylene glycol Examples include fatty acid esters and fatty acid alkanolamides.
The polyoxyalkyl ether is poly (oxyethylene) = alkyl ether, and the alkyl group having 12 to 15 carbon atoms and a mixture thereof. Examples of the polyoxyethylene alkylphenyl ether include poly (oxyethylene) = nonylphenyl ether and poly (oxyethylene) = octylphenyl ether.

  Examples of the amphoteric surfactants include lauryl dimethylamino oxide, amine oxides of olein dimethylamino oxide, amino acids such as sodium lauroylglutamate, lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, cocamidopropyl hydroxysultaine And betaine series such as 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

  By the way, polyoxyethylene alkylphenyl ethers such as poly (oxyethylene) = nonylphenyl ether are easy to biodegrade the polyoxyethylene chain of the hydrophilic group, but the biodegradation rate of the hydrophobic group (alkylphenol) is slow. Some people are concerned about the risk of endocrine disrupting effects. However, the stripping solution of the present invention is not intended to elute metals, and is not intended to elute copper foil or carbon in the stripping solution. In the present invention, if the powdered carbon suspended in the stripping solution after immersion is filtered and separated, and the carbon powder recovered together with the cleaning solution is filtered, the stripped copper foil and carbon powder are respectively Can be separated and collected easily. Therefore, the separated stripping solution is appropriately defoamed and has an excellent feature in that it can be used repeatedly, and disposal is not required every time. Also, the cleaning liquid can be discarded after removing the surface active component after filtration with activated carbon. In this respect, the practical environmental impact is extremely low compared to the previous method in which all the metals etc. are dissolved in the stripper and the waste liquid after treatment is discarded. It is a liquid and a peeling method.

  By immersing in the stripping solution of the present invention, carbon can be easily stripped from the surface of the copper foil of the negative electrode sheet of the lithium ion battery without melting. As a result, the copper foil having a high purity can be recovered in a solid state, which makes it very easy to recycle. In addition, since the peeled carbon can be recovered from the stripping solution and the cleaning solution, both the copper foil and the carbon can be separated and recovered in a state that can be easily reused and reused.

  In addition, the release agent used in the present invention can be used continuously and repeatedly by replenishing the solution if the carbon peeled from the foil is recovered and separated and removed from the release agent, so the release agent is newly updated. No replacement work is required, and the amount of waste liquid generated is significantly less than when the stripping solution is recovered by eluting metal or the like. Further, the release agent according to the present invention has low basic toxicity and low environmental load, so that it is easy to handle, and the waste liquid treatment after use is also difficult.

  Furthermore, among the surfactant component (B) that can be used in the present invention, polyoxyalkylphenyl ether is an inexpensive and easily available surfactant as a raw material. The present invention has led to a new application such that the active material carbon can be easily peeled off from the surface of the copper foil of the negative electrode sheet of the lithium ion battery only through the dipping and cleaning steps. Since the stripping solution can be repeatedly used without being disposed of, the practical environmental load is small and the utility is high.

It is a SEM image of carbon powder after separation collection (600 times). It is a SEM image of 3000 carbon after separation and collection.

  After stripping using a stripping agent and stripping method for stripping active material carbon from the copper foil surface of the negative electrode sheet of the lithium ion battery of the present invention and the stripping agent, high purity copper foil and carbon are separated and recovered. About the method, the form for implementing them is demonstrated in order. Of course, the release agent of the present invention is not limited to the exemplified components of these examples.

  About the release agent for carbon from the copper foil surface of the negative electrode sheet of the lithium ion battery used in the present invention, the alkaline solution obtained by diluting and mixing with the A liquid component and B liquid component shown in Table 1 and Table 2 below, and water. The solution will be described as an example. The adjustment to the A liquid and the B liquid is only for the convenience of storage and handling before use, and both components of the A liquid B liquid are diluted and mixed with water at the same time in the present invention. It may be used as a stripping solution. In addition, in order to dilute the surface active component of the liquid B, it is preferable to mix while gradually adding water or the like to the surface active component.

  It is preferable to mix and adjust the two liquids A and B at the time of use in order to avoid separation if the two liquids are mixed and stored for a long time. Even if it is separated, it can be used by stirring and mixing, but stirring with a large volume of the stripping solution while defoaming is labor intensive, so it can be said that it is easier to prepare by adjusting just before use. The stripping solution is diluted to a concentration that is excellent in cleaning properties while maintaining the capability as a stripping solution by gradually mixing 10% by mass of each of the A solution and B solution with water to make an emulsion. It can be used for Of course, even if the liquid A is mixed and used without being diluted, it can be peeled off sufficiently. However, since the labor for cleaning increases, the liquid A is diluted with water. It is preferable to use the solution as a stripping solution.

(Table A)
(Liquid A)
Ingredient name / Content (mass%)
Potassium hydroxide: 1.0-5.0
Phosphate: 5.0-10.0
Silicate: 5.0-10.0
Polyhydric alcohol: 1.0 or less
Water: the rest

(Table B)
(Liquid B)
Ingredient name / Content (mass%)
Poly (oxyethylene) = nonylphenyl ether: 8.0
Water: 92.0

  Here, potassium hydroxide uses a stripping solution as an alkaline solution. Phosphate gives the solution releasability and is effective as a builder. Silicate has a chelating effect and plays a role in preventing copper corrosion. Water is a diluent.

  Further, hydroxides such as sodium hydroxide and lithium hydroxide may be used in place of the potassium hydroxide in the liquid A. Examples of the phosphate include diphosphate and the like. Examples of the silicate include potassium silicate. Examples of polyhydric alcohols include glycol ethers. Although the thing containing a polyhydric alcohol is illustrated in A liquid, it is not an essential component.

  The surface active component of the B liquid facilitates the penetration of the hydrophobic compound that plays the role of adhering the copper foil and carbon of the negative electrode into the binder. Will go. By mixing the A liquid and the B liquid component, a solution that can be easily peeled can be obtained without particularly requiring conditions such as stirring, long-time immersion, and high-temperature treatment.

  Table 2 illustrates poly (oxyethylene) = nonylphenyl ether as the type of surfactant in the liquid B, but is not particularly limited. Nonionic surfactants, cationic surfactants Surfactants such as amphoteric surfactants can be used. Since the stripping agent is a mixture with an aqueous solution of hydroxide, an anionic surfactant is not necessarily suitable in relation to its dissolution equilibrium.

  The temperature of preparation (mixing) of the stripping solution and stripping operation is preferably 20 ° C. or higher. When the negative electrode sheet material is immersed in the stripping solution of this example, if the liquid temperature of the stripping solution is 20 ° C. or higher, it will be sufficiently stripped just by immersing in the stripping solution in about 5 to 15 minutes. Furthermore, when a gentle flow rate is given by stirring, peeling is further promoted and the treatment time can be shortened.

  And from a practical viewpoint, 50 degreeC or more is suitable for shortening of immersion time, Preferably it is 60 to 80 degreeC. This is because a practical peeled state can be obtained without requiring special stirring within a few minutes. In order to shorten the stripping time, it is desirable to increase the processing temperature in the stripping tank to 50 ° C. or higher. However, if the processing temperature is too high, the stripping solution tends to evaporate or the stripping solution is maintained at a low temperature. That would be the case. In addition, when mixing at a high temperature of 80 ° C. to 90 ° C. or higher, the B liquid component may be salted out, which is not preferable. However, even when the mixing is performed at a high temperature, the salt breakage state of the component B is eliminated by cooling the mixed solution, so that it can be used repeatedly.

  In addition, it is not very preferable in terms of working time to carry out dilution mixing of the A and B liquids at a low temperature of 20 ° C. or lower. This is because the temperature and the time required for mixing the two liquids are proportional to each other, so that if the temperature is too low, a long time is required for mixing.

  Furthermore, a series of steps of a method for peeling off the active material carbon from the copper foil surface of the negative electrode sheet of the lithium ion battery in the embodiment of the present invention will be described below. Roughly, the carbon is removed from the copper foil by immersing the negative electrode sheet in a release agent, washing and washing, wiping and drying, filtering the copper foil from the cleaning solution, and drying it to obtain carbon. The copper foil and carbon are separated and recovered.

(Removal agent adjustment procedure)
The standard use concentration of the stripping agent is a concentration obtained by diluting 5 times so that it becomes 1000 L by adding warm water to 100 kg of solution A and 100 kg of solution B. But the density | concentration of a peeling agent can be suitably adjusted according to the state and quantity of the carbon adhering to the copper foil surface. The liquid is put into the peeling tank and slowly stirred and adjusted so that the whole becomes a uniform liquid. At that time, for example, the free alkalinity is adjusted to about 8 to 12 points, and the processing temperature is set to about 60 to 80 ° C.

(Measurement of free alkalinity)
Here, pipette 10 ml of the carbon stripper accurately into an Erlenmeyer flask, add several drops of indicator phenolphthalein, and titrate with 0.1 mol / L hydrochloric acid test solution until the carbon stripper turns from red to colorless. The number of ml of the 0.1 mol / L hydrochloric acid test solution required for the test is referred to as a point, and represents the free alkalinity of the carbon release agent.

  If the stripping process is continued repeatedly, some of the components are consumed or evaporated, so it is recommended to measure the concentration appropriately and adjust the deficiency to maintain a good concentration of the stripper. . The replenishment amount of A liquid and B liquid can be calculated by the following formula. Even if the point condition is satisfied, the peeling ability is sufficiently maintained by appropriately replacing the peeling liquid after repeated use to some extent.

A liquid replenishment amount (kg) = 10 × (Po−P) × V
Po: Standard concentration P: Measurement concentration V: Carbon release agent amount (m ³ )
The replenishment amount of the B liquid is the same as that of the A liquid.

(Immersion process)
The negative electrode sheet taken out from the lithium ion battery (as it is or may be cut into an appropriate size in advance) is placed in a mesh basket, and the stripping solution of the present invention (for example, the liquid temperature is 60 ° C.). Soak in a cylindrical container containing the solution. At that time, when left standing for 3 to 15 minutes, the stripping solution penetrates, and the carbon is turned up and peeled off from the surface of the copper foil. Of course, the stripping solution may be fluidized not only to stand at the time of immersion but also to slowly move the stirrer and stir. Even without stirring, it can be sufficiently peeled off by lifting, but when it is further stirred, peeling is completed in a shorter time. When the cocoon is pulled up from the cylindrical container, the copper foil is pulled up with the carbon turned up from the surface of the copper foil, so some of the carbon falls into the stripping solution, but many are pulled up with the copper foil in the lifted state. . When the exfoliated carbon layer is thick, it is crushed into a exfoliating solution and precipitated as a block or powder.

(Washing process)
The copper foil is transferred to a water washing tank, and the stripping solution component remaining on the copper foil surface is immersed in water for cleaning. Since the carbon pulled together is only lightly adhered to the surface, it can be easily detached from the copper foil. For example, the process of washing with gentle stirring for 30 seconds is repeated twice. Whether the copper foil surface after washing with water is sufficiently washed can be confirmed as follows. The free alkalinity in the stripping solution and the washing solution is measured, and the dilution rate, that is, the washing rate is determined from these values. If the free alkalinity in the stripping solution is 8.2 points or less, it can be said that the alkali component is sufficiently removed. At the time of washing with water, the carbon adhering lightly to the surface is crushed and peeled off, so that a clean copper foil is obtained.

  If necessary, an impact caused by vibration such as cavitation by ultrasonic waves may be applied as appropriate, and if there is a carbon residue on the surface, it may be removed and an alkali component on the surface of the copper foil may be removed. . Since the present invention has a sufficient carbon peeling ability so as to exert a sufficient effect without ultrasonic cleaning, for the purpose of more quickly cleaning the alkali component on the surface of the copper foil, It is a degree to use.

(4) Wiping and drying process After the said process, a final copper foil can be obtained more rapidly by wiping off the copper foil surface suitably and drying. A copper foil that is clean even if it is lifted from the cleaning liquid and allowed to stand or is naturally dried can be obtained. The copper foil surface also has the effect of a chelating agent component, maintains a clean metallic luster, and is recovered as a copper foil solid, so the purity of 99% or more of the original copper foil is maintained as it is. doing.

(Flushing water filtration and carbon separation)
Separation and collection of the sludge carbon in the washing water is performed by filtering the washing water. In addition, although a filtrate may foam, when foaming is confirmed, the surfactant is removed from washing water, defoaming by adding activated carbon suitably.

  As a specific procedure, filter paper is set in a funnel (branner), the suction pump is operated to keep the inside of the suction bottle in a negative pressure state, and the water to be filtered is poured into the Buchner for suction filtration. By passing through the suction step in this way, carbon can be quickly removed from the washing water. Similarly, carbon desorbed on the stripping solution side is appropriately filtered at the stage where the stripping solution becomes dirty, and dried to separate and recover the carbon.

  The obtained carbon can be separated and recovered as a high-purity carbon powder by removing residual impurity components such as a binder by calcination at a higher temperature in addition to filtration and drying. The particle size distribution, specific surface area, and true specific gravity of the obtained carbon were measured, and a fine surface structure was observed with a scanning electron microscope. For the particle size distribution, a Shimadzu laser diffraction particle size distribution analyzer SALD-2000 was used. Belsorp-mini made by Nippon Bell Co., Ltd. was used for the relative area. The SEM image used Hitachi-S-3000N.

After separation and recovery, the calcined carbon powder had an average particle size of 12 μm in median diameter. The specific surface area was 16 m ² / g, and the true specific gravity by a pycnometer was 2.30. 1 and 2 show SEM images of the carbon powder after the calcination treatment. The magnification is 600 times in FIG. 1 and 3000 times in FIG. 2, and the applied voltage is 15 kV. It was confirmed that the fine carbon powder used for general industrial applications was obtained by recovery.

Example 1
The above-mentioned liquid A and liquid B (containing poly (oxyethylene) = nonylphenyl ether as a surfactant component) dissolved in water at a 5-fold dilution, free alkalinity adjusted to 8 to 12 points, and temperature adjusted to 60 ° C. Make a liquid and put it into the peeling tank. The lithium ion battery was disassembled, the negative electrode sheet material was taken out, placed in a mesh basket, and then immersed in a peeling tank for about 5 minutes. Thereafter, it was lifted and moved to a water washing tank, and carbon was sufficiently peeled from the copper foil while being appropriately stirred.

  The peelability evaluation was A +. Simply dipping the negative electrode sheet material for 5 minutes just by immersing it in the above stripping solution makes it possible to easily detach the carbon from the copper foil surface of 90% or more of the negative electrode sheet material in the peeling tank. It was confirmed that they were peeled off.

In addition, after the peeling process of the copper foil and carbon of Example 1, washing water was filtered and carbon was collect | recovered. In addition, the filtration filter is No. having a filtration area of 0.0038 m ² . 5C was used. As a result of the filtration, the filter was not clogged and the filtration was good. In addition, since bubbling of the filtrate was observed, it was defoamed with activated carbon. A few mm thick deposit (dehydrated cake) could be easily separated and recovered from the filter paper surface.

  In Table 1, the result of having evaluated peelability, changing a component and a composition ratio is shown as an Example of this invention. The copper foil was immersed in the same procedure as in Example 1 for about 5 minutes, and then the copper foil and carbon were peeled off while being washed with water.

In addition, about the peeling state of the copper foil in each surfactant, it evaluated by C from A + as follows.
A +: Excellent (90% or more peeled off only by dipping, which can be sufficiently peeled off by water washing without stirring)
A: Good (80% was peeled off only by dipping, and residual carbon was sufficiently peeled off in the cleaning process)
A-: Slightly good (sufficient peeling was not obtained by dipping alone, but residual carbon was peeled off by hand turning in the cleaning process)
B: Permitted (Dipping and stirring do not release sufficiently, and some parts cannot be removed even after washing)
C: Impossible (only a practically peeled state was obtained)

(Example 2)
As shown in Table 1, the polyhydric alcohol was not included, but the peelability evaluation was A +, which was excellent.

Example 3
As the surfactant component, polyoxyethylene lauryl ether (nonionic surfactant) is used. The peelability evaluation was A.

Example 4
As the interfacial chemical conversion component, octyldimethylethylammonium ethyl sulfate (cationic surfactant) is used. The peelability evaluation was A.

(Example 5)
As the surfactant component, lauryl dimethylamino oxide (an amphoteric surfactant) is used. The peelability evaluation was A.

(Example 6)
It does not contain phosphate and silicate. Since phosphate has a peeling effect, the peelability was slightly inferior to that of Example 1, and the evaluation was A.
As a result of the above, it was confirmed that when the stripping solution of the surfactant component of the present invention was used, the carbon was satisfactorily stripped from the copper foil surface.

(Example 7)
The component of hydroxide, silicate, and phosphate of A liquid is increased. The peelability evaluation was A +.

(Example 8)
The amount of hydroxide of the A liquid is reduced. The peelability evaluation is A-, which is slightly inferior to other examples, but practicality is obtained.

(Comparative Example 1)
The component A was diluted 10 times with water, the negative electrode sheet was immersed for about 5 minutes in the same manner as in Example 1, and then the state of peeling of the copper foil and carbon was observed while washing with water. However, the evaluation of Comparative Example 1 was C, and the copper foil and carbon could not be peeled from the negative electrode of the lithium ion battery.

(Comparative Example 2)
The negative electrode sheet was immersed in an aqueous solution containing only the surface active component poly (oxyethylene) = nonylphenyl ether for about 5 minutes, and then peeling was attempted while washing with water. However, the evaluation of Comparative Example 2 was C, and the copper foil and carbon could not be sufficiently peeled from the negative electrode of the lithium ion battery, and practicality as a stripping solution was not obtained.

  As described above, according to the stripping solution of the present invention, since the stripping can be stably stripped only by immersion, the copper foil can be recovered while maintaining the purity of the solid without much extra work, Both carbon can be separated and recovered, and both can be separated and recovered in a form that can be effectively reused.

Claims (12)

  By immersing the negative electrode sheet material for lithium ion batteries, on which the carbon is adhered to the copper foil surface, in a peeling tank containing an aqueous solution containing a hydroxide and a surface active component, the negative electrode sheet material adheres from the copper foil surface of the negative electrode sheet material A method for peeling carbon on a copper foil surface, wherein the carbon being peeled is peeled so that the copper foil and carbon can be separated and collected.   While immersing the negative electrode sheet material for a lithium ion battery having a carbon foil attached to the copper foil surface in a peeling tank containing an aqueous solution containing a hydroxide and a surface active component and having a liquid temperature of 20 ° C. or higher and lower than 90 ° C. while stirring. A method for peeling carbon on a copper foil surface, comprising: peeling off carbon adhering from the copper foil surface of the negative electrode sheet material so that the copper foil and carbon can be separated and collected.   The surfactant component in the aqueous solution contains, as an active ingredient, at least one surfactant selected from any of nonionic surfactants, cationic surfactants and amphoteric surfactants. The carbon peeling method on the copper foil surface according to claim 1 or 2, characterized by the above-mentioned.   The surface active component in the aqueous solution is polyoxyethylene alkyl ether or polyoxyethylene alkyl phenyl ether. The carbon on the copper foil surface according to any one of claims 1 to 2, Peeling method.   The hydroxide in the aqueous solution contains at least one hydroxide selected from potassium hydroxide, sodium hydroxide, and lithium hydroxide, according to any one of claims 1 to 4. The peeling method of carbon on the copper foil surface as described in 2.   The hydroxide in the aqueous solution further contains at least either or both of phosphate and silicate, on the copper foil surface according to any one of claims 1 to 5, Carbon peeling method.   The negative electrode sheet material for a lithium ion battery in which carbon is attached to the surface of the copper foil is immersed in the peeling tank containing the aqueous solution according to any one of claims 1 to 6, and then the taken-out sheet material is washed in the cleaning tank. The copper foil is recovered by washing with water and drying to collect the copper foil. On the other hand, the carbon dispersed in the aqueous solution of the peeling tank and the washing water of the cleaning tank is filtered and dried to recover the carbon powder. Recycling method for copper foil and carbon to be separated and recovered.   A carbon release agent that adheres to the copper foil surface of a negative electrode sheet material for a lithium ion battery, comprising an aqueous solution containing a hydroxide and a surface active component.   The surfactant component is at least one surfactant selected from any one of nonionic surfactants, cationic surfactants and amphoteric surfactants. The release agent of carbon adhering to the copper foil surface of the negative electrode sheet material for lithium ion batteries of description.   9. The carbon release agent attached to the copper foil surface of the negative electrode sheet material for a lithium ion battery according to claim 8, wherein the surface active component is polyoxyethylene alkyl ether or polyoxyethylene alkyl phenyl ether.   The hydroxide according to any one of claims 8 to 9, wherein the hydroxide contains at least one hydroxide selected from potassium hydroxide, sodium hydroxide, and lithium hydroxide. A carbon release agent that adheres to the copper foil surface of the negative electrode sheet material for lithium ion batteries.   The hydroxide in the aqueous solution further contains at least one or both of phosphate and silicate, on the copper foil surface according to any one of claims 8 to 11. A carbon release agent that adheres to the copper foil surface of the negative electrode sheet material for lithium ion batteries.