Method for recovering lithium from spent crucibles

Abstract

The method for recovering lithium from waste crucibles according to the present invention comprises: contacting the waste crucibles with a salt solution; recovering the waste crucibles that have been in contact with the salt solution and heat-treating the recovered waste crucibles at a temperature of 950°C or higher; separating the waste crucible metamorphic layer from the heat-treated waste crucibles; and recovering lithium from the separated waste crucible metamorphic layer.

Description

Technical Field

[0001] This invention relates to a method for recovering lithium from waste crucibles. Specifically, this invention relates to a method for efficiently separating and recovering lithium from waste crucibles discarded after the preparation of positive electrode active materials. Background Technology

[0002] The positive electrode active material of lithium secondary batteries is prepared by calcining lithium-containing salts such as cobalt, nickel, and manganese at high temperature in a sagger whose main components are silicon, aluminum, and magnesium oxides.

[0003] At this time, the raw material of the positive electrode active material may react with the surface of the crucible. With repeated use of the crucible, the surface of the crucible will be corroded and deteriorated due to the raw material of the positive electrode active material. Therefore, it must be discarded after a certain number of uses.

[0004] Therefore, lithium-containing components are present in the discarded crucibles after reuse, and a method is needed to effectively separate them.

[0005] Traditionally, to recover lithium from waste crucibles, the entire crucible is crushed before being roasted and acid-treated to leach the lithium. However, in this process, fractions with lower lithium content are also incorporated, resulting in higher processing costs.

[0006] Therefore, there is a need to develop a method that selectively recovers only the lithium-containing portion of waste crucibles. Summary of the Invention

[0007] (a) Technical problems to be solved The present invention aims to provide a method for recovering lithium from waste crucibles, which can effectively separate and recover the lithium-containing portion from waste crucibles.

[0008] (II) Technical Solution The present invention provides a method for recovering lithium from waste crucibles, comprising: contacting the waste crucibles with a salt solution; recovering the waste crucibles that have been in contact with the salt solution and heat-treating the recovered waste crucibles at a temperature above 950°C; separating the waste crucible metamorphic layer from the heat-treated waste crucibles; and recovering lithium from the separated waste crucible metamorphic layer.

[0009] (III) Beneficial Effects The method for recovering lithium from waste crucibles according to the present invention has the advantage of saving processing costs because the lithium-containing metamorphic layer is separated from the waste crucibles discarded after the preparation of positive electrode active materials, and then lithium is recovered.

[0010] In addition, lithium can be recovered from waste saggers for recycling, making it an environmentally friendly option with the advantage of reducing waste saggers. Attached Figure Description

[0011] Figure 1 An image showing the cross-section of a discarded sagger.

[0012] Figure 2 Images are shown to illustrate waste sagger samples according to several embodiments of the present invention.

[0013] Figures 3 to 5 These are top-view photographs, side-view photographs, and top-view images illustrating the detached and non-detached areas of the waste crucible sample that did not pass through the vibrating sieve, based on experimental examples. Detailed Implementation

[0014] Embodiments of the invention will be described in detail below. However, these are merely examples and the invention is not limited thereto; the invention is defined only by the scope of the claims.

[0015] In this invention, when a component is described as being "on" another component, this includes not only the case where the component is in direct contact with the other component, but also the case where there is another component between the two components.

[0016] In this invention, when a part is described as "containing" a component, unless otherwise stated, it means that other components may be included, and does not exclude the inclusion of other components.

[0017] One aspect of the present invention relates to a method for recovering lithium from waste crucibles, comprising: contacting the waste crucibles with a salt solution; recovering the waste crucibles that have been in contact with the salt solution and heat-treating the recovered waste crucibles at a temperature above 950°C; separating the waste crucible metamorphic layer from the heat-treated waste crucibles; and recovering lithium from the separated waste crucible metamorphic layer.

[0018] The method for recovering lithium from waste crucibles according to the present invention separates the modified layer by weakening the adhesion between the modified layer and the non-modified layer, and then roasts and acid-treats it to recover lithium, thus having the advantage of effectively recovering lithium.

[0019] Reference Figure 1 It can be seen that the waste crucible contains layers with different properties. Specifically, the part used to prepare the positive electrode active material can be divided into a modified layer containing a large amount of lithium due to the deposition of lithium raw materials and a non-modified layer equivalent to the original crucible.

[0020] Table 1 below shows the main components (unit: weight %) of the metamorphic layer and the non-metamorphic layer (original sagger), confirming that the metamorphic layer contains a large amount of lithium.

[0021] The main mineral phases of the metamorphic layer are lithium-containing LiAlO2 and Li4SiO4.

[0022] Table 1 In this invention, a metamorphic layer containing a large amount of lithium is separated from the non-metamorphic layer, and the lithium is recovered.

[0023] The method for recovering lithium from waste crucibles according to the present invention includes the step of contacting the waste crucibles with a salt solution.

[0024] The sagger is made of a porous material. When the waste sagger is brought into contact with the salt solution, the salt solution is absorbed into the porous waste sagger. Heat treatment at a temperature above 950°C (described later) can weaken the adhesion between the modified and non-modified layers.

[0025] The step of cutting the waste sagger may be further included before the step of contacting the waste sagger with the salt solution, but is not limited thereto.

[0026] When the step of cutting the waste sagger is further included, the contact between the waste sagger and the salt solution is smoother, which is preferred in terms of process.

[0027] In one embodiment of the invention, the salt solution may contain one or more compounds selected from the group consisting of alkali compounds and alkaline earth compounds.

[0028] For example, the salt solution may contain one or more of the group consisting of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, calcium chloride, calcium nitrate, calcium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, disodium hydrogen phosphate, barium chloride, trisodium phosphate, sodium silicate, potassium sulfide, sodium sulfite, zinc sulfate, aluminum chloride, and sodium sulfate.

[0029] Specifically, the salt solution may be obtained by dissolving one or more compounds selected from the group consisting of water-soluble alkali compounds and alkaline earth metal compounds in water.

[0030] In another embodiment of the invention, the salt solution may contain sodium silicate.

[0031] Specifically, the salt solution may contain a water glass solution.

[0032] In another embodiment of the invention, relative to 100% by weight of the total salt solution, one or more compounds selected from the group consisting of alkali compounds and alkaline earth compounds may be included at 3% by weight or more, preferably at 7% by weight or more, and more preferably at 10 to 20% by weight.

[0033] When the range includes one or more compounds selected from the group consisting of the alkali compound and the alkaline earth metal compound, the salt solution can effectively penetrate into the waste sagger. Therefore, the separation of the waste sagger metamorphic layer can be easily performed in the step of separating the waste sagger metamorphic layer from the waste sagger, which is described later. This is therefore preferred.

[0034] In another embodiment of the invention, the step of contacting the waste crucible with the salt solution may involve immersing the waste crucible in the salt solution.

[0035] The impregnation can be carried out by completely immersing the waste crucible in the salt solution for 10 to 90 minutes, preferably 20 to 60 minutes, more preferably 20 to 40 minutes, but is not limited thereto.

[0036] When the immersion time is within the specified range, the penetration of the salt solution can proceed sufficiently, which is therefore preferred.

[0037] In another embodiment of the invention, the salt solution can be applied to the surface of the waste crucible.

[0038] The coating can be performed by one or more methods selected from the group consisting of brush coating, spray coating, knife casting, and doctor blade coating, but is not limited thereto.

[0039] The amount of the salt solution applied is not limited. However, the amount of the salt solution applied can be sufficient to penetrate into the waste crucible.

[0040] The coating can be applied multiple times, but is not limited to this.

[0041] The method for recovering lithium from waste crucibles according to the present invention comprises the steps of: recovering the waste crucibles that have been in contact with the salt solution, and heat-treating the recovered waste crucibles at a temperature of 950°C or higher.

[0042] The main mineral phase of the metamorphic layer is lithium-containing LiAlO2, Li4SiO4, etc., and the metamorphic layer is tightly adhered to the non-metamorphic layer. Therefore, it is difficult to separate the metamorphic layer from the non-metamorphic layer by mechanical impact alone.

[0043] Therefore, according to the method for recovering lithium from waste crucibles according to the present invention, the adhesion between the modified layer and the non-modified layer at the interface is weakened by recovering the waste crucibles that have been in contact with the salt solution and heat-treating the recovered waste crucibles at a temperature of 95°C or higher.

[0044] In another embodiment of the invention, the heat treatment can be performed at a temperature of 1000 to 1500°C.

[0045] In another embodiment of the invention, the heat treatment can be performed at a temperature of 1000 to 1300°C.

[0046] When the heat treatment is performed within the specified range, the heat treatment time can be shortened as much as possible, while the adhesion between the modified layer and the non-modified layer at the interface is weakened to the maximum extent, which is therefore preferred.

[0047] In another embodiment of the present invention, the step of heat-treating the recovered waste sagger at a temperature above 950°C can be carried out for 30 minutes to 3 hours, preferably 40 minutes to 2 hours and 30 minutes, and more preferably 40 minutes to 1 hour.

[0048] When the heat treatment is performed within the specified time range, the energy consumption can be minimized, and the waste sagger layer can be easily separated in the step of separating the waste sagger layer from the waste sagger, which is described later. Therefore, this is preferred.

[0049] The heat treatment can be carried out in an electric furnace or a sintering furnace, but is not limited to these.

[0050] In another embodiment of the invention, it may further include a step of cooling the heat-treated waste sagger after the step of heat-treating the recycled waste sagger at a temperature above 950°C.

[0051] The cooling can be furnace-cooled to room temperature, but is not limited to this.

[0052] The method for recovering lithium from waste saggers according to the present invention includes the step of separating the waste sagger metamorphic layer from the heat-treated waste sagger.

[0053] In another embodiment of the invention, the step of separating the waste sagger metamorphic layer from the heat-treated waste sagger may include the step of separating the waste sagger metamorphic layer from the non-metamorphic layer of the waste sagger using one or more of the group consisting of a crusher, a shear, and a vibrator.

[0054] Specifically, according to the method for recovering lithium from waste saggers according to the present invention, the waste sagger metamorphic layer can be separated from the non-metamorphic layer of the waste sagger by applying physical force to the heat-treated waste sagger.

[0055] Preferably, the step of separating the waste sagger metamorphic layer from the heat-treated waste sagger can be performed using the vibrator.

[0056] Specifically, the vibrator can be a vibrating screen.

[0057] In another embodiment of the present invention, the step of separating the waste sagger metamorphic layer from the heat-treated waste sagger may include the step of separating the non-metamorphic layer of the waste sagger from the metamorphic layer of the waste sagger by sieving.

[0058] The sieving can be performed using a sieve with a mesh size of 3 to 15 mm, preferably 5 to 13 mm, and more preferably 7 to 10 mm.

[0059] The screening process ensures that the metamorphic layer of the waste sagger, separated from the non-metamorphic layer, passes only through the sieve openings of the specified size, thereby allowing the separation of the metamorphic layer.

[0060] The screening can be performed using a vibrating screener, but is not limited to this.

[0061] The steps of separating the waste sagger metamorphic layer from the heat-treated waste sagger and separating the non-metamorphic layer from the waste sagger metamorphic layer by sieving can be performed simultaneously, but are not limited to this.

[0062] For example, the waste crucible sample after heat treatment can be placed on the sieve and vibrated for 5 to 20 minutes, specifically 8 to 15 minutes, more specifically 8 to 10 minutes, thereby separating the waste crucible metamorphic layer by sieving, but not limited thereto.

[0063] In another embodiment of the present invention, the lithium content of the separated waste sagger metamorphic layer can be 1.0% by weight or more relative to the total weight of the separated waste sagger metamorphic layer.

[0064] The method for recovering lithium from waste crucibles according to the present invention includes the step of recovering lithium from the separated metamorphic layer of the waste crucibles.

[0065] Prior to the step of recovering lithium from the waste sagger metamorphic layer, a step of crushing the waste sagger metamorphic layer may be further included as needed, but is not limited thereto.

[0066] For example, after the deteriorated layer of the waste crucible is crushed using a crusher, it can be acid-treated.

[0067] Examples of pulverizers include, but are not limited to, sample mills, hammer mills, needle mills, wing mills, cyclone mills, and hammer crushers.

[0068] The method for recovering lithium from the metamorphic layer of waste saggers can be, for example, acid leaching, hydrothermal method, sulfuric acid roasting method, etc., but is not limited to these.

[0069] For example, lithium can be converted into lithium oxide, lithium carbonate, lithium hydroxide, etc., by calcining the modified layer of the waste sagger.

[0070] The roasting step can be a process of heat-treating the modified layer of the waste sagger at a temperature of 550 to 650°C for 1 to 4 hours. When the roasting step is carried out within the temperature range, the lithium compounds contained in the modified layer of the waste sagger are fully converted into a form that is easily soluble in water or acidic solutions during the acid treatment described later, which is therefore preferred.

[0071] The roasting step can be carried out in a rotary kiln, electric furnace, or similar facility, and can be carried out in an atmospheric atmosphere, but is not limited thereto.

[0072] In addition, lithium can be recovered by contacting the waste crucible metamorphic layer with an acidic solution to dissolve the lithium contained in the waste crucible metamorphic layer, but this is not the only method.

[0073] For the acidic solution, a solution obtained by adding an acid such as sulfuric acid to tap water, industrial water, distilled water, purified water, ion-exchange water, pure water, ultrapure water, etc., can be used.

[0074] For the acidic solution, the concentration can be adjusted so that the pH of the lithium in its dissolved state is between 7 and 10.

[0075] After the lithium is dissolved, it can be recovered by precipitating it out, but is not limited to this.

[0076] The method for recovering lithium from waste saggers according to the present invention does not recover lithium by crushing the entire waste sagger, but selectively recovers lithium by separating only the lithium-containing metamorphic layer. Therefore, compared with the case of recovering lithium by crushing the entire waste sagger, it has the advantage of effectively separating and recovering lithium.

[0077] Preferred embodiments and comparative examples of the present invention are described below. However, the following embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0078] Preparation Example Three sodium silicate solutions of different concentrations (WG1, WG2, and WG3) were prepared using sodium silicate solution (water glass) (purity: SiO2 35%, Na2O 17%), as shown in Table 2.

[0079] Table 2 Experimental Example By cutting up waste saggars, such as Figure 2 A square sample of approximately 3cm × 3cm was prepared as shown.

[0080] Subsequently, each sample was placed in a beaker and completely immersed in the sodium silicate solution prepared according to the preparation example, and then soaked for 30 minutes.

[0081] After impregnation, the samples were removed from the beakers and then heated in an electric furnace at a rate of 10°C per minute to the temperatures (800°C, 900°C, 1000°C) according to Table 3 below, and held for 1 hour, followed by furnace cooling. For comparison, the samples not impregnated in the solution (WG0) were also heat-treated using the same method.

[0082] The furnace-cooled sample was placed on a 9.5 mm test sieve and vibrated for 10 minutes in a vibrating sieve (vibrating sieve separator). Top-view and side-view photographs of the portion that did not pass through the test sieve, as well as the top-view photograph showing the detached and non-detached areas, were then plotted. Figures 3 to 5 .

[0083] In addition, the weight and fraction of the portions of each sample that did not pass through the vibrating sieve and the portions that passed through the vibrating sieve were measured and are shown in Table 3 below.

[0084] Table 3 Figure 3 These are top-view and side-view photographs of the portions that did not pass through the vibrating screen after heat treatment at 800℃, as well as schematic diagrams of the detached and non-detached areas in the top-view photograph. It can be seen that the sample not immersed in the solution (WG0) and the samples with different water glass concentrations (WG1, WG2, and WG3) showed almost no detachment of the lithium-containing metamorphic layer.

[0085] Figure 4 These are top-view and side-view photographs of the portions that did not pass through the vibrating screen after heat treatment at 900℃, as well as schematic diagrams of the detached and non-detached areas in the top-view photograph. It can be seen that the sample not immersed in the solution (WG0) and WG1, WG2, and WG3 with different water glass concentrations showed almost no detachment of the lithium-containing metamorphic layer.

[0086] Figure 5 These are top-view and side-view photographs of the portions that did not pass through the vibrating screen after heat treatment at 1000℃, as well as schematic diagrams of the detached and non-detached areas in the top-view photograph. It can be seen that the samples not immersed in the solution (WG0) and WG1 have slightly more detached portions than the samples treated at 800℃ and 900℃. On the other hand, it can be confirmed that all portions of samples WG2 and WG3 have detached.

[0087] As shown in Table 3, after being immersed in WG2 and WG3 solutions, the sieve residue of the samples heat-treated at 1000℃ was about 25%, and most of the lithium-containing altered layer had fallen off.

[0088] Therefore, it can be concluded that when waste crucibles are immersed in a salt solution of a certain concentration and then heat-treated at a temperature above 1000°C, the lithium-containing modified layer can be easily detached (separated) from the non-modified layer by vibration.

[0089] This invention is not limited to the embodiments described above and can be manufactured in various different ways. Those skilled in the art should understand that other specific methods can be used without altering the technical concept or essential features of the invention. Therefore, it should be understood that the above embodiments are exemplary in all respects and not restrictive.

Claims

1. A method for recovering lithium from waste crucibles, comprising: The step of bringing the waste crucible into contact with the salt solution; The steps include recovering the waste crucibles that have come into contact with the salt solution and heat-treating the recovered waste crucibles at a temperature above 950°C; The step of separating the metamorphic layer from the waste sagger after heat treatment; and The step of recovering lithium from the separated waste crucible metamorphic layer.

2. The method for recovering lithium from waste crucibles according to claim 1, wherein, The step of separating the metamorphic layer from the heat-treated waste sagger includes: The step of separating the metamorphic layer of the waste sagger from the non-metamorphic layer of the waste sagger using one or more of the group consisting of a crusher, a shearer and a vibrator.

3. The method for recovering lithium from waste crucibles according to claim 1, wherein, The salt solution contains one or more compounds selected from the group consisting of alkali compounds and alkaline earth compounds.

4. The method for recovering lithium from waste crucibles according to claim 3, wherein, Relative to 100% by weight of the total salt solution, the compound selected from the group consisting of alkali compounds and alkaline earth compounds comprises 3% by weight or more.

5. The method for recovering lithium from waste crucibles according to claim 1, wherein, The salt solution contains sodium silicate.

6. The method for recovering lithium from waste crucibles according to claim 1, wherein, The step of contacting the waste crucible with the salt solution includes: The waste crucible is immersed in the salt solution.

7. The method for recovering lithium from waste crucibles according to claim 1, wherein, The step of bringing the waste crucible into contact with the salt solution involves coating the surface of the waste crucible with the salt solution.

8. The method for recovering lithium from waste crucibles according to claim 1, wherein, In the step of heat treating the waste sagger. The heat treatment is carried out at a temperature of 1000 to 1500°C.

9. The method for recovering lithium from waste crucibles according to claim 8, wherein, In the step of heat treating the waste sagger. The heat treatment is carried out at a temperature of 1000 to 1300°C.

10. The method for recovering lithium from waste crucibles according to claim 1, wherein, The step of heat-treating the recovered waste saggers at a temperature above 950°C shall be carried out for 30 minutes to 3 hours.

11. The method for recovering lithium from waste crucibles according to claim 1, further comprising: After the step of heat-treating the recovered waste saggers at a temperature above 950°C, The step of cooling the waste sagger after heat treatment.

12. The method for recovering lithium from waste crucibles according to claim 2, wherein, The step of separating the metamorphic layer from the heat-treated waste sagger includes: The step of separating the non-modified layer of the waste sagger from the modified layer of the waste sagger by sieving.

13. The method for recovering lithium from waste crucibles according to claim 1, wherein, The lithium content of the separated waste crucible metamorphic layer is more than 1.0% by weight relative to the total weight.

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