Method for manufacturing porous cellulose nanofiber film, lithium recovery apparatus comprising same, and lithium recovery method using same

Abstract

The present invention discloses a lithium recovery apparatus. The lithium recovery apparatus, which recovers lithium ions, by adsorption, from a lithium ion-containing electrolyte, comprises: a tank for accommodating the lithium ion-containing electrolyte; a porous cellulose nanofiber film immersed in the electrolyte and containing a carboxyl group; and a first electrode and a second electrode disposed to be spaced apart from each other in the electrolyte, with the porous cellulose nanofiber film interposed therebetween.

Description

Method for manufacturing a porous cellulose nanofiber film, a lithium recovery device comprising the same, and a lithium recovery method using the same

[0001] The present invention relates to a method for manufacturing a porous cellulose nanofiber film, a lithium recovery device including the same, and a lithium recovery method using the same.

[0002] Lithium is a key component of lithium-ion batteries, which are used in various electronic devices such as electric vehicles, mobile phones, and laptops. With the expansion of the electric vehicle market, demand for lithium-ion batteries is rapidly increasing, and the market size is expected to expand further. As demand for lithium increases, so too does the need for lithium recovery methods.

[0003] Solvent extraction is a representative lithium recovery method, but it has the disadvantage of consuming a lot of energy during the solvent purification and recycling process and being a complex process. Therefore, a lithium recovery method that can compensate for these shortcomings is needed.

[0004] One object of the present invention is to provide a lithium recovery device having a simple process and a high lithium recovery amount.

[0005] Another object of the present invention is to provide a method for manufacturing a porous cellulose nanofiber film included in the lithium recovery device.

[0006] Another object of the present invention is to provide a method for recovering lithium using the lithium recovery device.

[0007] In order to achieve the above object, the present invention provides a lithium recovery device for recovering lithium ions by adsorbing them from a lithium ion-containing electrolyte, comprising: a tank for accommodating the lithium ion-containing electrolyte; a porous cellulose nanofiber film immersed in the electrolyte and containing a carboxyl group; and a first electrode and a second electrode spaced apart from each other in the electrolyte, with the porous cellulose nanofiber film interposed therebetween.

[0008] In addition, the present invention provides a method for producing a porous cellulose nanofiber film capable of reversible lithium ion adsorption and desorption, comprising: a first step of preparing a suspension by adding cellulose nanofibers and hydrochloric acid to a first solvent; a second step of vacuum-filtering the suspension using a membrane to prepare a filter cake from which moisture has been removed; a third step of immersing the filter cake in a second solvent containing isopropanol and hydrochloric acid to prepare a porous cellulose nanofiber film; and a fourth step of drying the porous cellulose nanofiber film.

[0009] In addition, the present invention provides a method for recovering lithium, comprising: a step of dissolving lithium contained in a recyclable material in a first electrolyte; a step of arranging a porous cellulose nanofiber film containing a carboxyl group in the first electrolyte; a step of applying a voltage to a first electrode and a second electrode spaced apart from each other in the first electrolyte and interposing the porous cellulose nanofiber film therebetween, thereby replacing hydrogen ions of the carboxyl groups with lithium ions to lithiate the porous cellulose nanofiber film; and a step of immersing the lithiated porous cellulose nanofiber film in a second electrolyte containing hydrogen ions to desorb lithium ions from the porous cellulose nanofiber film.

[0010] According to the present invention, the lithium recovery device of the present invention can recover lithium through a simple process, and the porous cellulose nanofiber film of the present invention has the advantage of being reusable.

[0011] Figure 1 is a flow chart of a method for manufacturing a porous cellulose nanofiber film according to an embodiment of the present invention.

[0012] Figure 2 is a schematic diagram of a lithium recovery device according to an embodiment of the present invention.

[0013] Figure 3 is a flowchart of a method for recovering lithium according to an embodiment of the present invention.

[0014] Figure 4 shows the appearance of a porous cellulose nanofiber film and a filter cake.

[0015] Figure 5 is a scanning electron microscope image of a porous cellulose nanofiber film.

[0016] Figure 6 is a nitrogen adsorption / desorption curve of a porous cellulose nanofiber film.

[0017] Figure 7 is a pore distribution diagram of a porous cellulose nanofiber film.

[0018] Figure 8 is an infrared spectroscopy (FT-IR) spectrum of a porous cellulose nanofiber film.

[0019] Figure 9 is an infrared spectroscopy spectrum of a porous cellulose nanofiber film after performing Example 3.

[0020] Figure 10 shows the color change of a porous cellulose nanofiber film according to lithium desorption.

[0021] Figure 11 is a graph showing the lithium extraction amount of Example 3 and Comparative Example 1.

[0022] Figure 12 is a schematic diagram of a reuse method of a lithium recovery device.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be modified in various ways and can take various forms, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing each drawing, similar reference numerals are used to indicate similar components. In the attached drawings, the dimensions of structures are shown larger than actual size to ensure clarity of the present invention.

[0024] While terms like "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0025] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] Meanwhile, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning within the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0027]

[0028] Figure 1 is a flow chart of a method for manufacturing a porous cellulose nanofiber film according to an embodiment of the present invention.

[0029] Referring to FIG. 1, a method for producing a porous cellulose nanofiber film capable of reversible lithium ion adsorption and desorption may include a first step (S110) of preparing a suspension by adding cellulose nanofibers and hydrochloric acid to a first solvent; a second step (S120) of vacuum-filtering the suspension using a membrane to prepare a filter cake from which moisture has been removed; a third step (S130) of immersing the filter cake in a second solvent containing isopropanol and hydrochloric acid to prepare a porous cellulose nanofiber film; and a fourth step (S140) of drying the porous cellulose nanofiber film.

[0030] In the above first step (S110), the first solvent may be water, but is not limited thereto.

[0031] In one embodiment, cellulose nanofibers may be added to the first solvent in an amount of 0.05 to 1 wt%, but the present invention is not limited thereto. For example, cellulose nanofibers may be added to 100 ml of the first solvent in an amount of 0.1 wt%.

[0032] In one embodiment, during the first step, COO included in the initial cellulose nanofibers- Na + The sodium (Na) ions of the group can be replaced by hydrogen (H) ions provided from hydrochloric acid, and as a result, the cellulose nanofibers after the first step can include -COOH groups.

[0033] In the second step (S120), the cellulose nanofibers of the first step can be manufactured into a film form through vacuum filtration.

[0034] In the third step (S130), the second solvent may be a solution in which isopropyl and 1M hydrochloric acid are mixed in a volume ratio of 800 to 1200:1, but is not limited thereto. For example, the second solvent may be a solution in which isopropyl and 1M hydrochloric acid are mixed in a volume ratio of about 1000:1.

[0035] In one embodiment, the filter cake may be immersed in the second solvent for 10 to 15 hours. For example, the filter cake may be immersed in the second solvent for 12 hours. While the filter cake is immersed in the second solvent, it may be immersed in isopropyl alcohol while maintaining the -COOH groups of the cellulose nanofibers by hydrochloric acid. Additionally, an alcohol solvent such as isopropyl alcohol can replace water between the cellulose nanofibers, thereby expanding and improving the porous structure of the film after drying.

[0036] In the fourth step (S140), the drying may be performed at 60 to 100°C for 10 to 15 hours, but is not limited thereto. For example, the drying may be performed at 80°C for 12 hours or more.

[0037]

[0038] Figure 2 is a schematic diagram of a lithium recovery device according to an embodiment of the present invention.

[0039] Referring to FIG. 2, a lithium recovery device can absorb and recover lithium ions from a lithium ion-containing electrolyte, and can include: a tank for receiving the lithium ion-containing electrolyte; a porous cellulose nanofiber film manufactured by the method for manufacturing the porous cellulose nanofiber filter, immersed in the electrolyte, and containing a carboxyl group; and a first electrode and a second electrode spaced apart from each other in the electrolyte, with the porous cellulose nanofiber film interposed therebetween.

[0040] In one embodiment, the porous cellulose nanofiber film comprises COO of cellulose nanofibers. - Na + The functional group may be converted to COOH. The COOH electrochemically reacts with lithium ions contained in the electrolyte to form COO - Li + Bonds can be formed.

[0041] In one embodiment, the average pore size of the porous cellulose nanofiber film containing the carboxyl group may be, but is not limited to, 4 to 11 nm. For example, the porous cellulose nanofiber film may have a mesoporous structure with an average pore size of 8 nm.

[0042] In one embodiment, the electrolyte is not particularly limited in material as long as it can conduct lithium ions after dissolving lithium from a material containing lithium metal. In one embodiment, the electrolyte may include a lithium salt typically used in a lithium ion battery. For example, the electrolyte may include, but is not limited to, one or more lithium salts selected from the group consisting of LiPF6, LiBF4, LiPO2F2, LiNO3, LiBOB, LiDFOB, LiTFSI, and LiFSI.

[0043] In one embodiment, the negative electrode is lithium, and the positive electrode may include, but is not limited to, one or more selected from the group consisting of lithium, LiFePO4, LiMn2O4, LiCoO2, LiNiO2, and Li2FeSiO4. For example, LiFePO4 may be used as the positive electrode. The positive electrode may use a positive electrode material containing lithium.

[0044] In one embodiment, the positive electrode and the negative electrode can apply an electric field to the electrolyte, thereby causing lithium ions in the electrolyte to move toward the porous cellulose nanofiber film. In addition, hydrogen ions in the carboxyl groups of the porous cellulose nanofiber film can be replaced by lithium ions that have moved toward the porous cellulose nanofiber film.

[0045]

[0046] Figure 3 is a flowchart of a method for recovering lithium according to an embodiment of the present invention.

[0047] Referring to FIG. 3, a method for recovering lithium using the lithium recovery device may include a step of dissolving lithium contained in a recyclable material in a first electrolyte (S150); a step of arranging a porous cellulose nanofiber film containing a carboxyl group in the first electrolyte (S160); a step of applying a pulse current to a first electrode and a second electrode spaced apart from each other in the first electrolyte and positioned between the porous cellulose nanofiber films, thereby replacing hydrogen ions of the carboxyl groups with lithium ions to lithiate the porous cellulose nanofiber film (S170); and a step of immersing the lithiated porous cellulose nanofiber film in a second electrolyte containing hydrogen ions to desorb lithium ions from the porous cellulose nanofiber film (S180).

[0048] In one embodiment, the pulse current may be repeated 50 to 200 times at 0.3 to 1 mA. For example, the pulse current may be repeated 100 times at 0.55 mA.

[0049]

[0050] Hereinafter, to aid understanding of the present invention, examples will be given in detail. However, the following examples are intended only to illustrate the scope of the present invention and are not intended to limit its scope. These examples are provided to more fully explain the present invention to those of average skill in the art.

[0051]

[0052] <Example 1> Manufacturing of porous cellulose nanofiber film

[0053] Cellulose nanofibers were diluted in 100 ml of water to a concentration of 0.1 wt%. 15 ml of 0.1 M HCl was additionally added and a suspension was prepared using a homogenizer. The suspension was vacuum-filtered, and the filter cake with the moisture removed was recovered. The filter cake was immersed in a mixed solution of isopropyl and 1 M HCl (Isopropanol / HCl 1000:1 by volume) for more than 12 hours. After the immersion was complete, the filter cake was recovered and dried in an oven at 80°C under vacuum for 12 hours.

[0054]

[0055] <Example 2> Manufacturing of lithium recovery device and lithium adsorption

[0056] EC / DEC (50 / 50, v / v) containing 1.0 M LiPF6 was used as an electrolyte and injected into a tank. Lithium foil was placed inside the tank as the first and second electrodes, spaced apart from each other. The porous cellulose nanofiber film manufactured in Example 1 was placed between the first and second electrodes. A pulse current of 0.55 mA was applied to the electrodes for 100 times over 45 minutes.

[0057]

[0058] <Example 3> Lithium recovery method using a lithium recovery device

[0059] After performing the above Example 2, a porous cellulose nanofiber film was recovered. The porous cellulose nanofiber film was immersed in an electrolyte solution of 0.1 M HCl for 1 hour, and then the film was removed.

[0060]

[0061] <Comparative Example 1>

[0062] The porous cellulose nanofiber film manufactured in Example 1 was immersed in an electrolyte solution of EC / DEC (50 / 50, v / v) containing 1.0 M LiPF6 dissolved therein for 12 hours, and then dried in an argon atmosphere.

[0063]

[0064] Experimental Example 1

[0065] Figure 4 shows the appearance of a porous cellulose nanofiber film and a filter cake. The filter cake is the appearance after being immersed in a mixed solution of isopropyl and 1 M HCl (Isopropanol / HCl 1000:1 by volume) for more than 12 hours in Example 1. It was confirmed that the cellulose nanofiber film was translucent. This is because the porous structure caused light scattering, reducing the amount of light transmittance.

[0066] Figure 5 is a scanning electron microscope image of a porous cellulose nanofiber film. During the vacuum filtration process for manufacturing the porous cellulose nanofiber film, the area in contact with air was set to the upper portion, and the area in contact with the filtration membrane was set to the lower portion. The surface properties of the upper and lower portions were observed. The results in Figure 3 confirmed that both the upper and lower portions had a porous structure.

[0067] Figure 6 shows the nitrogen adsorption / desorption curve of a porous cellulose nanofiber film. According to the IUPAC (International Union of Pure and Applied Chemistry) adsorption isotherm classification, this corresponds to a type-IV isotherm, and hysteresis loops due to the material's mesoporous structure were observed.

[0068] Figure 7 is a pore distribution diagram of a porous cellulose nanofiber film. It was confirmed that the average pore size of the porous cellulose nanofiber film was approximately 7 nm.

[0069]

[0070] Experimental Example 2

[0071] Figure 8 is an FT-IR spectrum of a porous cellulose nanofiber film. The COO of conventional cellulose nanofibers - Na + It was confirmed that COOH was converted into COO through Example 1. The porous cellulose nanofiber film of Example 2 was converted into COO - Li + It was confirmed that it was converted to . Comparative Example 1 maintained the COOH form without chemical change.

[0072]

[0073] Experimental Example 3

[0074] Figure 9 is an infrared spectroscopy (FT-IR) spectrum of a porous cellulose nanofiber film after performing Example 3. Comparing the FT-IR peaks of the porous cellulose nanofiber filters of Examples 2 and 3, COO - Li + It was confirmed that lithium was converted to COOH as it was extracted.

[0075] Figure 10 shows the color change of a porous cellulose nanofiber film according to lithium desorption. The porous cellulose nanofiber film was originally gray, but changed to yellow upon lithium adsorption (Example 2). The process of extracting lithium from the lithium-adsorbed cellulose nanofiber film and restoring its original color was confirmed in Figure 10. When lithium was extracted according to Example 3, it was confirmed that the lithium was extracted while restoring its original color within approximately 5 seconds. These visible characteristics suggest that it could be applied as a lithium recovery material and a type of lithium indicator.

[0076] Figure 11 is a graph showing the lithium extraction amounts of Example 3 and Comparative Example 1. The lithium extraction amounts of the electrolytes after performing Example 3 and Comparative Example 1 were analyzed using an Atomic Absorption Spectrometer (AAS). The lithium concentration in the electrolyte of Example 3 was detected to be approximately 9 times higher than that in the electrolyte of Comparative Example 1.

[0077] Figure 12 is a schematic diagram of a method for reusing a lithium recovery device. After recovering lithium by performing a porous cellulose nanofiber film as in Example 3, it can be placed back into the lithium recovery device. Alternatively, a porous cellulose nanofiber film can be manufactured according to Example 1 and placed into the lithium recovery device, thereby reusing the lithium recovery device.

[0078]

[0079] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. In a lithium recovery device that absorbs and recovers lithium ions from a lithium ion-containing electrolyte, A tank containing the lithium ion-containing electrolyte; A porous cellulose nanofiber film immersed in the electrolyte and containing a carboxyl group; A lithium recovery device comprising a first electrode and a second electrode spaced apart from each other in the electrolyte, with the porous cellulose nanofiber film interposed therebetween.

2. In paragraph 1, The porous cellulose nanofiber film containing the above carboxyl group is COO of cellulose nanofibers - Na + A lithium recovery device in which the functional group is converted to COOH.

3. In paragraph 1, A lithium recovery device, wherein the average pore size of the porous cellulose nanofiber film containing the above carboxyl group is 2 to 11 nm.

4. In paragraph 1, A lithium recovery device, wherein the electrolyte comprises one or more lithium salts selected from the group consisting of LiPF6, LiBF4, LiPO2F2, LiNO3, LiBOB, LiDFOB, LiTFSI and LiFSI.

5. In paragraph 1, The above negative electrode is lithium, A lithium recovery device, wherein the positive electrode comprises at least one selected from the group consisting of lithium, LiFePO4, LiMn2O4, LiCoO2, LiNiO2, and Li2FeSiO4.

6. A method for manufacturing a porous cellulose nanofiber film capable of reversible lithium ion adsorption and desorption, A first step of preparing a suspension by adding cellulose nanofibers and hydrochloric acid to a first solvent; A second step of producing a filter cake from which moisture has been removed by vacuum filtering the above suspension using a membrane; A third step of preparing a porous cellulose nanofiber film by immersing the filter cake in a second solvent containing isopropanol and hydrochloric acid; and A method for producing a porous cellulose nanofiber film, comprising a fourth step of drying the porous cellulose nanofiber film.

7. In paragraph 6, In the above first step, A method for producing a porous cellulose nanofiber film, wherein cellulose nanofibers are added in an amount of 0.05 to 1 wt% to the first solvent.

8. In paragraph 6, In the third step above, A method for producing a porous cellulose nanofiber film, comprising immersing the filter cake in the second solvent for 10 to 15 hours.

9. In paragraph 6, In the above 4th step, A method for producing a porous cellulose nanofiber film, wherein the above drying is performed at 60 to 100°C for 10 to 15 hours.

10. A step of dissolving lithium contained in recycled material into a first electrolyte; A step of placing a porous cellulose nanofiber film containing a carboxyl group in the first electrolyte; A step of applying voltage to a first electrode and a second electrode spaced apart from each other in the first electrolyte solution and positioned between the porous cellulose nanofiber films, thereby replacing hydrogen ions of the carboxyl groups with lithium ions to lithiate the porous cellulose nanofiber film; and A method for recovering lithium, comprising the step of immersing the above-mentioned lithiated porous cellulose nanofiber film in a second electrolyte containing hydrogen ions to desorb lithium ions from the above-mentioned porous cellulose nanofiber film.

11. In paragraph 10, The above pulse current is A method for recovering lithium, repeating 50 to 200 times at 0.3 to 1 mA.

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